JP2003084148A - Plastic optical fiber, plastic optical fiber cable and plastic optical fiber cable with plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastic optical fiber having low transmission loss and excellent mechanical properties such as durability against repeated bending. SOLUTION: The plastic optical fiber has a core made of methyl polymethacrylate and a first clad and a second clad concentrically formed in layers around the core. In this fiber, a copolymer having a specified composition containing a long-chain fluoroalkylmethacrylate unit (A) expressed by general formula (I), a short-chain fluoroalkylmethacrylate unit (B) expressed by general formula (II) and a methyl methacrylate unit (C) is used for the first clad. A copolymer having a specified composition consisting of a vinylidene fluoride unit, a tetrafluoroethylene unit and a hexafluoropropylene unit is used for the second clad. In formula (I), m represents 1 or 2 and n represents an integer of 5 to 12. In formula (II), X represents a hydrogen atom or a fluorine atom and m represents an integer of 1 to 4.

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, a plastic optical fiber cable and a plastic with a plug, which are used for home home networks and optical information communication in mobile media such as automobiles, airplanes and railways. Optical fiber cable.

[0002]

2. Description of the Related Art Conventionally, as an optical fiber, a silica-based optical fiber capable of excellent optical transmission over a wide wavelength range has been put to practical use mainly in a trunk system, but this silica-based optical fiber is expensive. Low workability. Therefore, a plastic optical fiber (hereinafter appropriately abbreviated as "POF") having advantages such as cheaper, lighter weight, larger diameter, and easier end face processing and handling has been developed, for example, in fields such as lighting and sensors. , FA, OA, LAN, etc. have been put to practical use in the field of wiring for short / medium distance communication.

Most of the communication POFs currently in practical use are step index POFs having a core-clad structure with polymethylmethacrylate (PMMA) as a core material, and have recently been driven at high speed. In combination with a possible visible red light source, it is expected to be used as a high-speed communication transmission line such as a medium-high speed LAN. P currently in practical use
The OF transmission band is usually about 75 MHz / 50 m, and improvement of the band is required.

Further, when the POF is used as indoor wiring or wiring inside an automobile, it is usually laid and used in a narrow space. Therefore, reduction of optical transmission loss due to bending is also desired.

In recent years, in WO96 / 36894 and Japanese Patent No. 2992352, a method of increasing the numerical aperture (NA) of POF from about 0.5 to about 0.3 for the purpose of improving the transmission band is proposed. Taken, transmission distance 5
The transmission band at 0 m is improved to about 200 MHz. However, since such a POF has a small numerical aperture, there is a problem in that the amount of light rays emitted to the outside when the fiber bends increases and the optical transmission loss increases.

For the purpose of solving this problem, Japanese Unexamined Patent Publication No. 9-159844 discloses a method of disposing a second cladding having a lower refractive index outside the cladding. As the general second cladding, a copolymer of vinylidene fluoride and tetrafluoroethylene (mass ratio 71.9 / 28.1), which is commonly used in lighting fibers and the like, is used. . This POF has a refractive index of N.V. when the refractive index of the core is n ₁ and the refractive index of the second cladding is n ₃ . The numerical aperture calculated from the relational expression of A = (n ₁ ² −n ₃ ² ) ^1/2 is at most about 0.5,
It is difficult to sufficiently reduce the bending loss. In addition, in order to investigate the light loss due to bending, for a 50 m bare wire or cable, use a light source with an excitation NA of 0.60 to hold the light once when wrapped around a bar with a bending radius of 10 mm at a point of 25 m of the bare wire or cable. Although the rate is sought, the POF bare wire has a retention rate of 78% and the POF cable has a retention rate of 70%, which are not sufficient characteristics to satisfy practical characteristics such as in-vehicle applications.

Recently, there has been disclosed a technique for further improving bending characteristics by using a ternary copolymer of vinylidene fluoride having a low refractive index, tetrafluoroethylene and hexafluoropropylene as the second cladding.

In Japanese Unexamined Patent Publication (Kokai) No. 10-221543, a core, a first clad material consisting of 10 to 40 mol% of a short-chain fluoroalkyl methacrylate and 60 to 90 mol% of methyl methacrylate, and a vinylidene fluoride unit are used. P comprising a second clad comprising a copolymer containing
OF is disclosed. Also, in that embodiment,
The first clad is 8FMA (2,2,3,3,4,4,5,5-octafluoropentyl methacrylate) / MMA (methyl methacrylate) copolymer (refractive index n _1-clad = 1.458),
A POF is disclosed in which the second cladding is a vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer (refractive index n2 _-clad = 1.365). Since the first clad has a high transparency, it cannot attenuate the light of higher modes, and thus the transmission band of the POF cannot be sufficiently obtained, and the copolymer composition unit is a short-chain methacrylate unit. Therefore, the glass transition temperature becomes high and the polymer becomes rigid, and when POF is bent, cracks are likely to occur, resulting in insufficient mechanical strength.

In JP-A-11-101915, the first clad is made of a resin having a higher refractive index than the second clad, and the second clad is made of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene. In the combination, the vinylidene fluoride component is 30 to 92 mol%, the tetrafluoroethylene component is 0 to 55 mol%, and the hexafluoropropylene component is 8 to
A POF consisting of a resin in the range of 25 mol% is disclosed. Further, as the optimum one for the first cladding, (meth) acrylic acid long-chain fluoroalkyl ester /
(Meth) acrylic acid short-chain fluoroalkyl ester /
A methyl (meth) acrylate copolymer is exemplified.
In this clad material, the refractive index is increased by increasing the copolymerization ratio of methyl methacrylate, which is a copolymerization component, and decreasing the copolymerization ratio of fluorinated alkyl (meth) acrylate. However, the fluorinated alkyl (meth) acrylate is not introduced only for the purpose of lowering the refractive index, but is also introduced for the purpose of improving the flexibility and strength of the first cladding. When the refractive index is increased, there is a problem that the strength of the first cladding decreases.

The second composition within the composition range described in these publications
The clad resin is a (meth) acrylic acid long-chain fluoroalkyl ester / (meth) acrylic acid short-chain fluoroalkyl ester / methyl (meth) acrylate copolymer, which is generally known as a first clad resin, or Low compatibility with (meth) acrylic acid long-chain fluoroalkyl ester / methyl (meth) acrylate copolymer, (meth) acrylic acid short-chain fluoroalkyl ester / methyl (meth) acrylate copolymer, etc. However, there is a problem in that structural irregularities are likely to occur at the interface between the first cladding and the second cladding, and peeling easily occurs at the interface between the first cladding and the second cladding when repeatedly bent. Furthermore, since the second clad resin itself has high transparency, the loss of higher-order mode light generated when the incident light is transmitted while being reflected in the fiber is small, so that the band is not sufficient. is there.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a plastic optical fiber, a plastic optical fiber cable and a plastic optical fiber cable with a plug, which have low transmission loss and excellent mechanical properties such as resistance to repeated bending. Especially.

[0012]

The present invention is directed to a core made of polymethylmethacrylate or a copolymer of one or more vinyl monomers and methylmethacrylate, and a first clad on the outer periphery of the core. And a second clad, which is a plastic optical fiber having clads laminated concentrically in this order, wherein the first clad has the following general formula (I):

[0013]

[Chemical 3] (In the formula, m represents 1 or 2, and n represents an integer of 5 to 12.)
1 to 40% by mass of the unit (A) of the long-chain fluoroalkyl methacrylate represented by the following general formula (II)

[0014]

[Chemical 4] (In the formula, X represents a hydrogen atom or a fluorine atom, and m represents an integer of 1 to 4.) 1 to 40% by mass of the unit (B) of the short-chain fluoroalkyl methacrylate and the methyl methacrylate unit (C). The second clad comprises a vinylidene fluoride unit and a tetrafluoroethylene unit, the copolymer being composed of 50 to 98% by mass and another copolymerizable monomer unit (D) of 0 to 10% by mass. And hexafluoropropylene units, and consisting of 37.01 to 92 mol% of vinylidene fluoride units, 0.01 to 55 mol% of tetrafluoroethylene units, and 4.0 to 7.99 mol% of hexafluoropropylene units. The present invention is also characterized in that the present invention has a refractive index n ₁ of the core, a refractive index n ₂ of the first cladding, and a _second refractive index n ₂ at 25 ° C. by sodium D line.
The refractive index n _{3 of the} clad is expressed by the following relational expressions (1) and (2).
And (3) n ₂ > n ₃ (1) 0.36 ≧ (n ₁ ² −n ₂ ² ) ^1/2 ≧ 0.23 (2) (n ₁ ² −n ₃ ² ) ^1/2 ≧ 0. 55 (3) is satisfied, and relates to the above plastic optical fiber.

The present invention also relates to a plastic optical fiber cable having a coating layer on the outer circumference of the plastic optical fiber.

The present invention also relates to a plastic optical fiber cable with a plug in which a plug is installed at the end of the plastic optical fiber cable.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The POF of the present invention comprises polymethylmethacrylate (PMMA) or methylmethacrylate (MMA).
It has a core made of a copolymer containing MA) as a main component, and a clad that is concentrically laminated in the order of a first clad and a second clad on the outer periphery of the core.

In the POF of the present invention, the refractive index of the first cladding (measured value using sodium D line at 25 ° C.)
Is preferably 1.43 or more from the viewpoint of sufficiently reducing the numerical aperture of POF and improving the transmission band.
It is more preferably 1.455 or more. If the refractive index is too high, the bending loss of the POF tends to increase, so the refractive index of the first cladding is preferably 1.477 or less.

The first cladding is a unit (A) 1 of a long-chain fluoroalkyl methacrylate represented by the general formula (I).
-40% by mass and 1-40% by mass of the unit (B) of the short-chain fluoroalkyl methacrylate represented by the general formula (II)
And methyl methacrylate unit (C) 50 to 98% by mass
And other copolymerizable vinyl-based monomer units (D) 0 to
And 10% by mass.

The number of fluorine atoms of the fluorinated alkyl group of the unit (A) of the long-chain fluoroalkyl methacrylate represented by the general formula (I) is 13 or more in order to improve the mechanical properties of the copolymer. It is preferable. Examples of such a monomer unit include 2- (perfluorohexyl) ethyl methacrylate (13FM), 1H, 1H, 9H-hexadecafluorononyl methacrylate (16FM),
Monomer units such as 2- (perfluorooctyl) ethyl methacrylate (17FM), 1H, 1H, 11H- (icosafluoroundecyl) methacrylate (20FM) and 2- (perfluorodecyl) ethylmethacrylate (21FM) Is mentioned. These monomer units may be used alone or in combination of two or more.

The content of the long-chain fluoroalkylmethacrylate unit (A) in the copolymer constituting the first clad is in the range of 1 to 40% by mass, but in order to further improve the flexibility and mechanical properties. Is preferably in the range of 15 to 40% by mass. When the content of the unit (A) is less than 1% by mass, flexibility and mechanical properties may be insufficient, and when it exceeds 40% by mass, transparency is lowered and transmission loss of POF is increased. There is a risk.

The number of fluorine atoms of the fluorinated alkyl group of the unit (B) of the short-chain fluoroalkyl methacrylate represented by the general formula (II) is 9 or less in order to improve the transparency of the copolymer. Is preferred. Examples of such a monomer unit include 2,2,2-trifluoroethyl methacrylate (3FM), 2,2,3,3-tetrafluoropropyl methacrylate (4FM), 2,2,3,3,3.
-Pentafluoropropyl methacrylate (5FM),
Amount of 2,2,3,4,4,4-hexafluorobutyl methacrylate (6FM), 1H, 1H, 5H-octafluoropentyl methacrylate (8FM), 2- (perfluorobutyl) ethyl methacrylate (9FM), etc. The unit of body is mentioned. These monomer units may be used alone or in combination of two or more.

The content of the unit (B) of the short-chain fluoroalkyl methacrylate represented by the general formula (II) is 1% by mass.
Although it is in the range of ˜40% by mass, it is preferably in the range of 15% by mass to 40% by mass in order to further improve transparency. If this content is less than 1% by mass, sufficient transparency may not be obtained, and if it exceeds 40% by mass, flexibility decreases and cracks occur in the clad when the POF is bent. Therefore, the effect of reducing the increase in transmission loss may be insufficient.

The content of the methyl methacrylate unit (C) in the copolymer constituting the first cladding is 50% by mass to 9%.
It is in the range of 8% by mass, preferably 50.01% by mass or more. The content of the methyl methacrylate unit (C) is 5
If it is less than 0% by mass, it may be difficult to provide the first cladding with a sufficiently high refractive index, and sufficient transparency and heat resistance may not be obtained. If the amount is more than 98% by mass, the rigidity will be high, and it will be difficult to sufficiently reduce the increase in transmission loss when the POF is bent.

The copolymer constituting the first cladding optionally contains another monomer unit (D) in the range of 0 to 10% by mass. As the monomer forming the unit (D), it is preferable to use methyl acrylate in order to improve the thermal decomposition resistance, and methacrylic acid is used in order to improve the adhesion at the core-clad interface. Is preferred.

The copolymer constituting the first cladding is 23
It is preferable that the melt flow index is 5 to 40, which indicates the amount (g) of the polymer discharged from a nozzle having a diameter of 2 mm and a length of 8 mm in 10 minutes under the condition of 0 ° C. and a load of 5 kgf (49 N). If the melt flow index is too large, the flexibility and workability of POF may be reduced. On the contrary, if it is too small, the moldability of the copolymer may decrease.

The copolymer constituting the first cladding has a glass transition temperature (Tg) of 75 determined by DSC.
It is preferably at least ° C. If Tg is too low, spinning stability may be reduced, or heat resistance of POF may be reduced. On the other hand, if the Tg is too high, the clad material becomes hard and easily cracks, which may increase the transmission loss when the POF is bent. Therefore, Tg is preferably 110 ° C. or lower.

The second cladding in the POF of the present invention is
A vinylidene fluoride unit, a tetrafluoroethylene unit, and a hexafluoropropylene unit are included, and when the total of these three types of units is 100 mol%, the vinylidene fluoride unit is 37.01 to 92 mol% and the tetrafluoroethylene unit. Of 0.01 to 55 mol% and hexafluoropropylene units of 4.0 to 7.99 mol%. The copolymer of the second clad may contain other units within a range in which desired properties are obtained, and the content of the other units depends on the total constitutional units of the copolymer of the second clad. When the total is 100 mol%, 20 mol% or less is preferable, 10 mol% or less is more preferable, and 5 mol% or less is further preferable.

The copolymer used as the second clad in the present invention has good compatibility with the above-mentioned first clad, so that structural irregularity at the interface between the first clad and the second clad is reduced, and transmission loss is reduced. Not only can be reduced, but also peeling at the interface can be suppressed, and the second cladding having excellent strength can effectively protect the first cladding and suppress cracking of the first cladding. It is possible to suppress an increase in transmission loss when the POF is repeatedly bent. Further, the copolymer used for the second clad is also excellent in wet heat resistance. That is, in the POF of the present invention, by combining the specific first cladding and second cladding, the transmission loss of the POF is reduced, and in combination with the characteristics of the second cladding itself, mechanical characteristics such as resistance to repeated bending are improved. It can be further improved.

When the content of the vinylidene fluoride unit in the copolymer constituting the second cladding of the present invention is more than 92 mol%, the moldability is lowered and the refractive index is increased, so that the opening angle of the optical fiber is increased. There is a risk that the light amount becomes large and the bending loss light amount increases. On the other hand, if it is less than 37.01 mol%, the hardness and heat resistance may decrease. The content of vinylidene fluoride unit is 50 to 7
It is preferably 0 mol%.

The content of tetrafluoroethylene units is 5
If it is more than 5 mol%, the hardness and moldability may decrease. Further, by containing the tetrafluoroethylene unit, the refractive index can be lowered, the numerical aperture of the POF can be increased, and the heat resistance can be improved. The content of the tetrafluoroethylene unit is preferably 22.5 to 45 mol%.

Hexafluoropropylene has a structure with low symmetry, so by copolymerizing a relatively small amount,
The crystallinity of the copolymer of vinylidene fluoride and tetrafluoroethylene can be reduced. The effect of reducing the crystallinity is sufficiently exhibited when the content of the hexafluoropropylene unit is 4.0 mol% or more. However, the hexafluoropropylene unit in the copolymer composition is 7.99 mol% or less for the following three reasons.

1) The hexafluoropropylene unit is 7.
If it is more than 99 mol%, the compatibility between the first clad and the second clad decreases, and structural imperfections are likely to occur at the interface between the first clad and the second clad, resulting in deterioration of optical transmission characteristics and mechanical characteristics. To do.

2) Polyamide resin, especially nylon 11
Alternatively, when a coating layer using nylon 12 is formed on the outer periphery of the second cladding, the higher the content of hexafluoropropylene units in the second cladding, the lower the adhesion between the second cladding and the coating layer. , POF cable pull-out strength is reduced.

3) When the light leaking from the first clad is transmitted while being reflected in the second clad, if the transparency of the second clad is high, the generated higher mode light is not lost in the fiber. , Which causes a decrease in bandwidth. Therefore, by leaving a small amount of an appropriate crystalline portion in the second cladding, it is possible to reduce high-order mode light and improve the band.

For the above reasons, the content of hexafluoropropylene units in the second cladding is 4.0 to 7.99 mol%. The content of hexafluoropropylene unit is preferably 4.5 mol% or more, and 7.5 mol%
The following is preferable. More preferably, it is 4.7 mol% or more and 7.0 mol% or less.

The melt flow index of the copolymer constituting the second clad is 5 to 200,
It is preferable from the viewpoint of the spinning stability of POF.

The refractive index of the copolymer constituting the second clad (measured value at 25 ° C. using sodium D line)
Is preferably in the range of 1.350 to 1.380 because the amount of bending loss light can be sufficiently reduced.

The core of the POF of the present invention is a PMM.
A copolymer of A or MMA and a monomer copolymerizable with this MMA (hereinafter referred to as "MMA-based copolymer") is used. By using these (co) polymers, it is possible to obtain POF having excellent optical properties and high reliability.

The MMA-based copolymer preferably has an MMA unit content of 50% by mass or more from the viewpoint of transparency and heat resistance when the total copolymerization composition is 100% by mass.
0 mass% or more is more preferable, and 70 mass% or more is further preferable.

Examples of monomers copolymerizable with MMA include acrylic acid esters such as methyl acrylate, ethyl acrylate and butyl acrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, cyclohexyl methacrylate and fluorine. Examples thereof include methacrylic acid esters such as modified alkyl methacrylate, maleimides such as isopropyl maleimide, acrylic acid, methacrylic acid, styrene, and the like.
It can be copolymerized with MA.

In the POF of the present invention, the refractive index n ₁ of the core, the refractive index n ₂ of the first clad and the n _{3 of} the second clad at 25 ° C. by sodium D line are expressed by the following relational expression (1),
It is preferable to satisfy (2) and (3).

N ₂ > n ₃ (1) 0.36 ≧ (n ₁ ² −n ₂ ² ) ^1/2 ≧ 0.23 (2) (n ₁ ² −n ₃ ² ) ^1/2 ≧ 0.55 (3) By satisfying the relational expression (1), that is, the refractive index n ₂ of the first cladding and the refractive index n ₃ of the second cladding are set to n ₂ > n ₃
Therefore, when the POF is bent,
The light leaked from the first clad can be reflected by the second clad, and the transmission loss when the POF is bent can be reduced.

Regarding the relational expression (2), (n ₁ ² −
If n ₂ ² ) ^1/2 is less than 0.23, it may be difficult to sufficiently reduce the bending loss light amount when the POF is bent. If it exceeds 0.36, it may be difficult to obtain a POF having a sufficient transmission band.

Further, regarding the relational expression (3), (n ₁ ²
When -n ₃ ^{2) 1/2} is less than 0.55, it may become difficult to sufficiently reduce the bending loss amount when by bending the POF.

As described above, in the present invention, by using the material satisfying the relational expressions (1) to (3), the transmission band is high and the bending loss light amount can be reduced.

In the POF of the present invention, a protective layer may be coated on the outside of the second clad in order to improve flex resistance and wet heat resistance. As the protective layer, it is preferable to use a fluorine-based resin having a fluorine atom ratio of 59% by mass or more. When the proportion of fluorine atoms is 59% by mass or more, sufficient flex resistance, wet heat resistance, and chemical resistance can be achieved.

The material for the protective layer is, for example, a copolymer of vinylidene fluoride (vinylidene fluoride) and tetrafluoroethylene, a copolymer of vinylidene fluoride and hexafluoroacetone, vinylidene fluoride and trifluoroethylene. Copolymer with vinylidene fluoride and hexafluoropropylene copolymer, vinylidene fluoride with tetrafluoroethylene and hexafluoropropylene copolymer, vinylidene fluoride with tetrafluoroethylene and hexafluoroacetone copolymerization, Examples thereof include copolymers of ethylene, tetrafluoroethylene and hexafluoropropylene, but are not limited thereto.

The POF cable of the present invention can be made into a POF cable by closely disposing a coating layer on the outer periphery of the clad or the outer periphery of the protective layer in order to improve the bending resistance and the moisture heat resistance. Since this coating layer does not come into direct contact with the core, there is no particular problem even if the transparency decreases due to crystallization.

The material of the coating layer is vinyl chloride resin,
One or a mixture of two or more selected from the group consisting of chlorinated polyethylene resin, polyamide resin, polyethylene resin, polypropylene resin, urethane resin, and fluorine resin can be used, and is usually used as a coating material. It can be appropriately selected from known materials. Among them, the polyamide-based resin is excellent in heat resistance, bending resistance, and solvent resistance, and is therefore suitable as a POF coating material for applications requiring heat resistance and environment resistance. In particular, among the above polyamide-based resins, nylon 11 and nylon 12 are preferable as the POF coating material because they have excellent heat shrinkability and bending resistance, and have a relatively low melting point so that they have good processability. Also, nylon 11 and nylon 1
When No. 2 is coated on the outer side of the second cladding of the POF of the present invention described above, the adhesion between the second cladding and the coating layer is excellent, and the dimensional stability of the coating layer can effectively prevent the pinning phenomenon, which is preferable. , Nylon 11 is more preferable.

Further, the POF cable of the present invention is made of PO in order to further improve durability and environmental resistance.
A second coating layer made of a thermoplastic resin may be provided on the outer periphery of the coating layer provided on the outer periphery of F.

The thermoplastic resin used in the second coating layer includes vinyl chloride resin, polyethylene resin, polypropylene resin, chlorinated polyethylene resin, polyamide resin, polyurethane resin, fluorine resin, ethylene-vinyl acetate copolymer. One or a mixture of two or more selected from the group consisting of can be used. Of these, a polyamide resin is preferable when the POF requires heat resistance and solvent resistance depending on the environment in which it is used, and a polyethylene resin, ethylene-vinyl acetate when the POF requires bending resistance. A resin having a small elastic modulus such as a copolymer is more preferably used.

In the present invention, at least one coating layer is preferably coated in a non-stretched state. The resin containing methyl methacrylate as the main component of the POF core approaches the glass transition temperature when the temperature exceeds 100 ° C., and the molecular orientation of the core resin is relaxed, so that heat shrinkage occurs and the transmission loss rapidly increases. However, the heat shrinkage of the POF can be effectively suppressed by coating the coating layer with a resin having good adhesion to the clad or protective layer of the POF and excellent heat resistance without stretching.

Further, a plasticizer may be added to the resin constituting the coating layer, and in the case of vinyl chloride resin, for example, dioctyl phthalate, trioctyl trimellitate, tricresyl phosphate or the like can be added. . When adding the plasticizer, it is preferable to appropriately select and use a necessary amount so that the added plasticizer does not migrate to the POF and hinder the optical performance and mechanical properties of the POF.

The POF cable of the present invention can be manufactured by the composite melt spinning equipment which is a general POF manufacturing apparatus. It can also be produced by melt spinning only the core material and then dissolving the clad material in a solvent such as dimethylformamide or dimethylacetamide for solvent coating.

The POF cable of the present invention has a plug having a plug attached to the end of the cable for joining with a light source which is a signal source, a housing of a unit incorporated in a detector, another POF cable or the like. It can be used as an optical fiber cable. This plug includes a plug body and a stopper attached to the plug body to fix the optical cable.

[0057]

The present invention will be described in more detail with reference to the following examples. The evaluation and measurement in the examples were carried out by the following methods.

(Melt Flow Index) The melt flow index was measured according to Japanese Industrial Standard JIS K7210. The amount of polymer discharged from a nozzle having a diameter of 2 mm and a length of 8 mm in 10 minutes under the conditions of 230 ° C. and a load of 5 kgf (49 N) was measured.

(Refractive index) 200 μm thick by melt pressing
A film-shaped test piece of m was formed, and the refractive index (n _D of sodium D line at room temperature 25 ° C. (n _D
²⁵ ) was measured.

(Glass Transition Temperature (Tg)) Differential Scanning Calorimeter (DSC) (DSC manufactured by Seiko Instruments Inc.)
-220) was used. Sample heating rate 10 ° C /
The temperature was raised to 180 ° C in 10 minutes, held for 10 minutes to melt, then rapidly cooled to 0 ° C at 10 ° C / minute, and the heating rate was again 10 ° C.
The temperature was raised at a rate of 1 / min, and the glass transition temperature was determined from the heat generation and heat absorption behavior at this time.

(Light transmittance) A film having a thickness of 2.0 mm was prepared, and the light transmittance was measured using an integrating sphere in accordance with JIS K7361-1 standard.

(Transmission band) An optical fiber cable having a length of 20 m is prepared, and a wavelength of 650 n is obtained by the impulse response method.
m, excitation NA = 0.30, −3 dB band at 0.55 was measured using a sampling oscilloscope.

(Transmission loss) The transmission loss (dB / km) was measured by the 25m-5m cutback method. Light having a measurement wavelength of 650 nm and an incident light NA (numerical aperture) of 0.1 or 0.65 was used.

(Measurement of Bending Loss) Light is made incident from one end of a POF cable having a length of 11 m, and in that state, the POF cable has a radius of 10 mm at 10 points at 1 m intervals.
The sample was bent 90 degrees at a time, and the amount of light emitted from the other end was measured. The bending loss was calculated from the amount of light emitted from the POF cable bent in this way and the amount of emitted light measured in the same manner for the linear POF cable.

(Measurement of the number of times of repeated bending) P having a length of 4 m
A load of 500 gf (4.9 N) was applied to one end of the OF cable, and the center of this POF cable was sandwiched by two circular tubes having a diameter of 15 mm. The other end of this POF cable is moved to one side of the circular pipe and wrapped around the outer circumference of the circular pipe so that the POF cable bends 90 degrees, and then moved to the other side of the circular pipe so that the POF cable bends 90 degrees. Wrap it around the pipe circumference and bend it a total of 180 degrees, repeat this,
The number of bends when the POF cable was cut was measured.

(Measurement of Drawing Strength) The drawing strength between the POF element wire and the coating layer was measured. First, POF cable 1
Take 50mm and put 1st coating layer and 2nd coating layer from one end.
Carefully peel off each 0 mm, and length 50 from all sides.
The mm coating material was stripped off to leave the first coating layer and the second coating layer having a length of 100 mm. PO with the coating layer removed
The exposed part of the F strand is a diameter of a 5 mm thick acrylic plate.
While passing through a 1 mm hole and pulling out this POF wire at a pulling speed of 100 mm / min, from the POF cable to PO
The stress when the F strand was pulled out was measured.

Example 1 As the material of the first cladding,
To a monomer solution consisting of 2,2,3,3- (tetrafluoropropyl) methacrylate 15% by mass, 2- (perfluorooctyl) ethyl methacrylate 15% by mass, methyl methacrylate 69% by mass and methacrylic acid 1% by mass. On the other hand, N-N azobisisobutyronitrile 0.1% by mass,
0.1% by mass of n-octyl mercaptan was added, and dissolved oxygen was completely removed by nitrogen bubbling, followed by polymerization at 65 ° C. for 5 hours and then at 120 ° C. for 2 hours to obtain a polymer. After crushing the obtained polymer, it was vacuum dried at 180 ° C. for 10 hours. The melt flow index of this polymer was 19, the refractive index was 1.465, and the glass transition temperature was 95.2 ° C.

The above copolymer as the first clad material, the second
Vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer (5
2.1 / 40.0 / 7.9 mol%, refractive index 1.369,
Melt flow index 42.7), P as core material
After supplying MMA (refractive index 1.492) to a spinning head at 225 ° C. and spinning using a concentric compound nozzle, 15
Stretched twice in the fiber axis direction in a hot air oven at 0 ° C
Clad thickness 10 μm, second clad thickness 10 μm
A POF wire having a diameter of 1 mm was obtained.

The POF strands thus obtained were evaluated by the above method. The transmission loss of this POF strand is 650n
136 dB when measured with an incident NA of 0.1 at a wavelength of m
/ Km, and 165 dB / km at an incident NA of 0.65
And showed very good transmission characteristics. The transmission band is 432 at NA = 0.30 and 0.55, respectively.
MHz and 197 MHz.

The boundary between the first clad and the second clad of the POF was observed with a transmission electron microscope at a magnification of 25,000. As a result, an intermediate compatible layer was formed at the interface between the first clad and the second clad. Was observed.

First clad material 2g and second clad material 2g
Was sufficiently stirred and dissolved in 16 g of ethyl acetate, the solution was spread on a polyester film, and the solvent was removed by volatilization to obtain a polymer composition. The light transmittance of this polymer composition was 92%. Further, the transparency of this polymer composition was retained even after being retained for a long time (100 hours, 85 ° C., 95% RH).

Example 2 The POF element wire obtained in Example 1 was coated with nylon 12 using a T-die to form a first coating layer, and a POF cable having a diameter of 1.5 mm was obtained. . Furthermore, nylon 12 is attached to the outer circumference of this POF cable.
To form a second coating layer, which has a diameter of 2.3 mm
I got an F cable.

This POF cable was evaluated by the above method. The transmission loss of this POF cable is 138 dB / k when measured with an incident NA of 0.1 at a wavelength of 650 nm.
m, and was 172 dB / km at an incident NA of 0.65. The transmission bands are 400 MHz and 180 MHz at NA = 0.30 and 0.55, respectively.
Even if F was made into a cable, the transmission loss and the transmission band were good. Moreover, the number of repeated bendings was 30,000, the bending loss was 1.08 dB, and the pull-out strength was 65N.

POF after the repeated bending test
Similarly, the boundary portion between the first clad and the second clad was observed with a transmission electron microscope at a magnification of 25,000 times, but no change was observed at the interface between the first clad and the second clad.

It was confirmed that a plug could be attached to the end of this POF cable and used as a signal transmission cable to stably send a signal.

Example 3 A vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer (60.5 / 34.5 / 5.0 m) was used as the second clad material.
ol%, refractive index 1.374, melt flow index 32.1) except that P was changed in the same manner as in Example 1.
An OF strand was produced.

Then, a coating layer was provided on this POF element wire in the same manner as in Example 2 to obtain a POF cable.

The POF cable was evaluated by the method described above. The transmission loss of this POF cable is 6
134 dB measured at an incident NA of 0.1 at a wavelength of 50 nm
/ Km, and 178 dB / km at an incident NA of 0.65
Met. The transmission band is NA = 0.30, 0.55
At 430MHz and 221MHz respectively,
Even if the POF was made into a cable, the transmission loss and the transmission band were good. Moreover, the number of repeated bending was 35,800, the bending loss was 0.97 dB, and the pull-out strength was 69N.

Comparative Example 1 A vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer (53.0 / 38.0 / 9.0 m) was used as the second clad material.
ol%, refractive index 1.365, melt flow index 35.0) except that P was changed in the same manner as in Example 1.
An OF strand was produced.

Then, a coating layer was provided on this POF element wire in the same manner as in Example 2 to obtain a POF cable.

The POF cable was evaluated by the above method. The transmission loss of this POF cable is 6
14 when measured with an incident NA of 0.1 at a wavelength of 50 nm
1 dB / km, 175 dB at an incident NA of 0.65
It was / km. The transmission band is NA = 0.30,
420MHz and 150MHz at 0.55 respectively
Met. Moreover, the number of times of repeated bending was 9,000, the bending loss was 1.02 dB, and the pull-out strength was 40 N.

When the boundary between the first and second claddings of POF was observed with a transmission electron microscope at a magnification of 25,000 times, an intermediate compatible layer was found at the interface between the first and second claddings. Not observed, both clads were clearly divided into two.

Further, the POF after the above repeated bending test
Similarly, when the boundary part between the first clad and the second clad was observed with a transmission electron microscope at a magnification of 25,000 times, in the interface between the first clad and the second clad,
It was observed that delamination of both claddings occurred in some places.

A film of a mixed composition of the first clad material and the second clad material was produced in the same manner as in Example 1. As a result, a film which became cloudy and whitened during the slow cooling process was obtained. The same film, long-term (100 hours, 85 ℃, 95
% RH), it remained cloudy.

[0085]

As described above, according to the present invention,
It is possible to provide a POF and a POF cable having low transmission loss and excellent mechanical properties such as resistance to repeated bending. Further, it is possible to provide a POF cable having sufficient pull-out strength and repeated bending resistance.

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Claims (12)

[Claims] 1. A core made of polymethylmethacrylate or a copolymer of one or more vinyl monomers and methylmethacrylate, and a first clad and a second clad on the outer periphery of the core.
A plastic optical fiber having clads laminated concentrically in the order of clads, wherein the first clad has the following general formula (I): (In the formula, m represents 1 or 2, and n represents an integer of 5 to 12.)
1 to 40% by mass of the unit (A) of the long-chain fluoroalkylmethacrylate represented by the following general formula (II) (In the formula, X represents a hydrogen atom or a fluorine atom, and m represents an integer of 1 to 4.) 1 to 40% by mass of the unit (B) of the short-chain fluoroalkyl methacrylate and the methyl methacrylate unit (C). The second clad is composed of a copolymer composed of 50 to 98% by mass and another copolymerizable monomer unit (D) of 0 to 10% by mass, and the second cladding is a vinylidene fluoride unit and a tetrafluoroethylene unit. And hexafluoropropylene unit, vinylidene fluoride unit 37.01 ~
92 mol% and tetrafluoroethylene units 0.01-5
5 mol% and hexafluoropropylene units 4.0 to 7.
A plastic optical fiber comprising a copolymer of 99 mol%. 2. The refractive index n ₁ of the core, the refractive index n ₂ of the first clad, and the refractive index n ₃ of the second clad at 25 ° C. by sodium D line are expressed by the following relational expressions (1) and (2). ) And (3) n ₂ > n ₃ (1) 0.36 ≧ (n ₁ ² −n ₂ ² ) ^1/2 ≧ 0.23 (2) (n ₁ ² −n ₃ ² ) ^1/2 ≧ 0 0.55 (3) is satisfied, The plastic optical fiber of Claim 1 characterized by the above-mentioned. 3. The first cladding has a load of 5 at 230.degree.
A copolymer having a melt flow index value of 5 to 40, which indicates the amount (g) of the polymer discharged in 10 minutes from a nozzle having a diameter of 2 mm and a length of 8 mm under the condition of kgf (49 N). 2. The plastic optical fiber according to item 2. 4. The plastic optical fiber according to claim 1, 2 or 3, wherein the first cladding is made of a copolymer having a glass transition temperature (Tg) of 75 ° C. or higher determined by DSC. 5. The plastic optical fiber according to claim 1, further comprising a protective layer made of a fluorine-based resin having a fluorine atom ratio of 59% by mass or more on the outer periphery of the second cladding. 6. A plastic optical fiber cable having a coating layer on the outer circumference of the plastic optical fiber according to any one of claims 1 to 5. 7. The coating layer is one or a mixture of two or more selected from the group consisting of polyamide resin, vinyl chloride resin, chlorinated polyethylene resin, polyethylene resin, polypropylene resin, urethane resin, and fluorine resin. 7. The plastic optical fiber cable according to claim 6. 8. The plastic optical fiber cable according to claim 7, wherein the coating layer is made of nylon 11 or a resin containing nylon 12 as a main component. 9. The plastic optical fiber cable according to claim 6, further comprising a second coating layer made of a thermoplastic resin on the outer periphery of the coating layer. 10. The plastic optical fiber cable according to claim 9, wherein the second coating layer is made of a polyamide resin. 11. The plastic optical fiber cable according to claim 6, wherein at least one coating layer is not stretched. 12. A plastic optical fiber cable with a plug, wherein a plug is installed at the end of the plastic optical fiber cable according to any one of claims 6 to 11.