CN105676344A - Optical fiber, optical cable, communications equipment and lighting equipment - Google Patents

Abstract

The present invention relates to optical fiber, optical cable, communications equipment and lighting equipment which provide heat resistance, low transmission loss, optical fiber excellent in flexibility. Solution of the present invention is an optical fiber having a core and at least one layer of fiber sheath, the sheath material comprising a fluorine-based resin, fluorine-based resin comprising units selected from vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene units from the side leakage from the group consisting of units of at least one kind, so that the halogen lamp light source color coordinates x between the transmission light is x less of equal to 0.34.

Description

Optical fiber, optical cable, communication equipment and lighting equipment

technical field

The present invention relates to optical fibers, optical cables, communication equipment and lighting fixtures.

Background technique

Optical fibers are used in a wide variety of applications such as light transmission, lighting fixtures, decoration, and displays. Glass-based optical fibers have excellent light transmission properties over a wide wavelength range, but have problems such as poor processability and mechanical properties. On the other hand, a plastic optical fiber has a structure in which, for example, the outer periphery of a core formed of a highly transparent resin such as polymethyl methacrylate is covered with a sheath formed of a resin having a lower refractive index than the core and a highly transparent resin. Therefore, compared with glass-based optical fibers, it has characteristics such as excellent flexibility and processability.

As the material constituting the sheath, it is often used to contain vinylidene fluoride because of its excellent transparency, heat and humidity resistance, mechanical properties, and adhesion to polymethyl methacrylate, and its low refractive index compared with polymethyl methacrylate. Fluorine resin with ethylene unit and fluorinated alkyl methacrylate unit.

For example, Patent Document 1 discloses a plastic optical fiber using a fluorine-based resin containing vinylidene fluoride units, tetrafluoroethylene units, and hexafluoropropylene units as a material constituting the sheath. In addition, Patent Document 2 discloses a plastic optical fiber using a fluorine-based resin containing a fluorinated alkyl methacrylate unit as a material constituting the sheath.

prior art literature

patent documents

Patent Document 1: Japanese Patent Application Laid-Open No. 11-095044

Patent Document 2: Japanese Patent Laid-Open No. 2002-105134

Contents of the invention

The problem to be solved by the invention

Fluorine-based resins including vinylidene fluoride units, tetrafluoroethylene units, and hexafluoropropylene units as disclosed in Patent Document 1 generally contain sulfur atoms. Studies by the inventors of the present invention have revealed that when a large amount of sulfur atoms is contained, the transmission loss of the optical fiber, especially the transmission loss of the optical fiber at 400 nm to 600 nm, which is a short wavelength region, remarkably increases.

In addition, the fluorine-based resin containing the fluorinated alkyl methacrylate unit disclosed in Patent Document 2 is rigid and therefore prone to cracks, and the cracks cause optical fiber light leakage and may increase transmission loss.

Therefore, an object of the present invention is to provide an optical fiber that is heat-resistant, has low transmission loss, and is also excellent in bendability.

method used to solve the problem

The invention relates to an optical fiber, which is an optical fiber having a core and at least one sheath. The material constituting the sheath includes a fluorine-based resin, and the fluorine-based resin is composed of a vinylidene fluoride unit, a tetrafluoroethylene unit and a hexafluoropropylene unit. In at least one of the groups, the chromaticity coordinate x of the light leaked from the side during light transmission using a halogen lamp as a light source is x≤0.34.

Furthermore, the present invention relates to an optical cable having a coating layer on the outer periphery of the aforementioned optical fiber.

Further, the present invention relates to a communication device and a lighting fixture including the above-mentioned optical fiber.

The effect of the invention

The optical fiber of the present invention has heat resistance, low transmission loss, and excellent bendability.

Description of drawings

FIG. 1 is a schematic cross-sectional view showing an example of a step-index type optical fiber as an example of the optical fiber of the present invention.

Fig. 2 is a schematic cross-sectional view showing an example of a multi-core optical fiber as an example of the optical fiber of the present invention.

Explanation of symbols

10 fibers

11 cores

12 sheaths

12a sheath (innermost)

12b sheath (outermost layer)

12c Sheath (Sea Department).

detailed description

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the configurations shown in these drawings.

(optical fiber)

The optical fiber of the present invention has a core and a sheath composed of at least one layer surrounding the outer periphery of the core. The type of optical fiber includes, for example, a step-index optical fiber, a multimode step-index optical fiber, a graded-index optical fiber, and a multi-core optical fiber. Among these optical fibers, a step-index type optical fiber is preferable in terms of thermal stability, easy and inexpensive manufacture, and ability to realize longer-distance communication.

The step-index optical fiber totally reflects light at the interface between the core and the sheath, and propagates the light in the core.

FIG. 1 shows a cross-sectional structure of an example of a step-index optical fiber 10 . FIG. 1( a ) shows a case where the sheath is composed of one layer, and the sheath 12 surrounds the outer periphery of the core 11 . FIG. 1( b ) shows the case where the sheath is composed of two layers. The innermost sheath 12 a surrounds the outer periphery of the core 11 , and the outermost sheath 12 b surrounds the innermost sheath 12 a outer periphery.

In the multi-core optical fiber, light is totally reflected at the interface between the core and the sheath, and the light is propagated through the plurality of cores.

Fig. 2 shows a cross-sectional structure of an example of a multi-core optical fiber. In the example shown in FIG. 2( a ), one sheath (sea portion) 12 c surrounds a plurality of cores 11 to constitute a multi-core optical fiber. In the example shown in FIG. 2( b ), a plurality of cores 11 have sheaths 12 on their respective outer peripheries, and one sheath (sea portion) 12 c surrounds the plurality of sheaths 12 to constitute a multi-core optical fiber.

(core)

The material (core material) constituting the core is not particularly limited as long as it is a highly transparent resin, and can be appropriately selected according to the purpose of use and the like.

Examples of highly transparent resins include acrylic resins, styrene-based resins, and carbonate-based resins. These resins may be used alone or in combination of two or more. Among these resins, acrylic resins are preferable from the viewpoint of reducing the transmission loss of optical fibers.

Examples of the acrylic resin include methyl methacrylate homopolymer (PMMA), a copolymer containing 50% by mass or more of a methyl methacrylate unit (methyl methacrylate copolymer), and the like. These acrylic resins may be used alone or in combination of two or more. Among these acrylic resins, methyl methacrylate homopolymers and copolymers containing 50% by mass or more of methyl methacrylate units are preferable because of excellent optical properties, mechanical properties, heat resistance, and transparency. The methyl methacrylate-based copolymer is preferably a copolymer containing 60% by mass or more of methyl methacrylate units, more preferably a copolymer containing 70% by mass or more of methyl methacrylate units. It is particularly preferred that the core material is methyl methacrylate homopolymer.

The core material can be produced using known polymerization methods. As a polymerization method for producing a core material, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, a solution polymerization method etc. are mentioned, for example. Among these polymerization methods, the bulk polymerization method or the solution polymerization method is preferable from the viewpoint of suppressing the mixing of foreign substances.

(sheath)

The sheath forms at least one layer around the core. The sheath may be formed of one layer as shown in FIG. 1( a ), or may be formed of two or more layers as shown in FIG. 1( b ). From the viewpoint of reducing light attenuation, the sheath preferably has 1 to 3 layers. In addition, the sheath is more preferably one layer because the manufacturing equipment can be simplified and the productivity is excellent.

The material constituting the sheath (sheath material) is a fluorine-based resin containing at least one selected from the group consisting of vinylidene fluoride (VDF) units, tetrafluoroethylene (TFE) units, and hexafluoropropylene (HFP) units.

By using the above-mentioned fluorine-based resin as the sheath material, attenuation of light at the interface between the core and the sheath can be reduced. As a result, the transmission loss is reduced, the flexibility is high, and the sheath is less likely to be cracked, so an optical fiber excellent in heat resistance and bendability can be obtained.

When the sheath is composed of two or more layers, it is preferable that at least the sheath of the outermost layer (for example, 12b in FIG.

Examples of fluororesins include VDF homopolymer, VDF/TFE copolymer, VDF/TFE/HFP copolymer, VDF/HFP copolymer, VDF/TFE/HFP/(perfluoro)alkyl vinyl ether Copolymer, VDF/hexafluoroacetone copolymer, VDF/TFE/hexafluoroacetone copolymer, ethylene/VDF/TFE/HFP copolymer, ethylene/TFE/HFP copolymer, VDF/trifluoroethylene copolymer, etc. These fluorine-based resins may be used alone or in combination of two or more. Among these fluorine-based resins, VDF/TFE copolymers, VDF/TFE/HFP copolymers, VDF/HFP copolymers, ethylene/ VDF/TFE/HFP copolymer, ethylene/TFE/HFP copolymer, more preferably VDF/TFE copolymer, VDF/TFE/HFP copolymer, VDF/HFP copolymer.

The total content of VDF units, TFE units, and HFP units is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, based on 100% by mass of the fluorine-based resin, from the viewpoint of excellent flexibility. .

From the standpoint of processability and reduction in optical fiber transmission loss, when a VDF/TFE copolymer is used as the fluorine-based resin, in 100% by mass of the copolymer, the VDF unit is preferably 65% by mass to 85% by mass, The TFE unit is 15% by mass to 35% by mass, more preferably the VDF unit is 77% by mass to 83% by mass, and the TFE unit is 17% by mass to 23% by mass.

From the standpoint of processability and reduction in optical fiber transmission loss, when a VDF/HFP copolymer is used as the fluorine-based resin, in 100% by mass of the copolymer, it is preferable that the VDF unit is 70% by mass to 90% by mass, The HFP unit is 10% by mass to 30% by mass, more preferably the VDF unit is 82% by mass to 88% by mass, and the HFP unit is 12% by mass to 18% by mass.

In addition, the fluororesin can be produced using a known method.

(chromaticity coordinates)

When the optical fiber of the present invention transmits light from a halogen lamp as a light source, the chromaticity coordinate x of light leaking from the side is x≤0.34, preferably x≤0.31. The chromaticity coordinate x can be adjusted within the above-mentioned range by adjusting, for example, the content of sulfur atoms in the fluororesin.

In addition, in this specification, the chromaticity coordinate x is taken as the value measured using a spectrophotometer to transmit light using a halogen lamp as a light source to an optical fiber and leak out from the side of the optical fiber. The value of is calculated according to JISZ8701-1995.

Regarding the X-ray intensity derived from the sulfur element in the fluorine-based resin, it is preferably 0.6 kcps or less, more preferably 0.5 kcps or less, from the perspective of reducing the attenuation of light at the interface between the core and the sheath and reducing the transmission loss of the optical fiber. It is preferably 0.4 kcps or less, particularly preferably 0.3 kcps or less.

In addition, in this specification, the X-ray intensity originating in a sulfur element shall be the value measured by fluorescent X-ray analysis based on JISK0119.

The content of sulfur atoms in the fluororesin is preferably 50 ppm or less in order to obtain the chromaticity coordinates within the above range, and to reduce the attenuation of light at the interface between the core and the sheath and to reduce the transmission loss of the optical fiber. It is more preferably 40 ppm or less, still more preferably 30 ppm or less, particularly preferably 20 ppm or less.

In addition, in this specification, the content rate of a sulfur atom shall be the value calculated from the said X-ray intensity value.

The refractive index of the core material and the sheath material is not particularly limited as long as the refractive index of the sheath material is lower than that of the core material. From the viewpoint of increasing the numerical aperture relative to the maximum angle at which light can propagate, the refractive index of the core material is preferably 1.45 to 1.55, the refractive index of the sheath material is 1.35 to 1.51, and the refractive index of the core material is more preferably 1.46 to 1.53. The refractive index of the sheath material is 1.37-1.49, more preferably the refractive index of the core material is 1.47-1.51, and the refractive index of the sheath material is 1.39-1.47.

In addition, in this specification, a refractive index is set as the value measured using sodium D-ray at 25 degreeC.

(forming)

Optical fibers can be shaped using known shaping methods. As a molding method, a melt spinning method is mentioned, for example. The shaping of the optical fiber by the melt spinning method can be carried out, for example, by melting the core material and the sheath material separately and performing composite spinning.

The diameter of the optical fiber is preferably from 0.01 mm to 5.0 mm, more preferably from 0.05 mm to 4.0 mm, and still more preferably from 0.1 mm to 3.0 mm, since the transmission loss of the optical fiber can be reduced and the handleability of the optical fiber is excellent.

The diameter of the core relative to the diameter of the optical fiber is preferably 70% to 99.8%, more preferably 80%, from the viewpoint of reducing the transmission loss of the optical fiber, the coupling efficiency with the optical element, and the tolerance to optical axis deviation. % to 99.4%, more preferably 90% to 99%.

The thickness of the sheath relative to the diameter of the optical fiber is preferably 0.1% to 15%, more preferably 0.3%, from the viewpoint of reducing the transmission loss of the optical fiber, the coupling efficiency with the optical element, and the tolerance to the optical axis deviation. % to 10%, more preferably 0.5% to 5%.

When the sheath is composed of two layers, the thicknesses of the innermost sheath (12a in FIG. 1(b)) and the outermost sheath (12b in FIG. 1(b)) can be appropriately set.

When the sheath is composed of two layers, the ratio of the thickness of the sheath of the outermost layer to the thickness of the sheath of the innermost layer is preferably 0.5 to 5, more preferably 1, from the viewpoint of reducing the transmission loss of the optical fiber. ~4, more preferably 1.2~3.

(post-processing)

From the viewpoint of improving the mechanical properties, the optical fiber is preferably heat-stretched. The conditions of the heat stretching treatment may be continuously or batchwise as long as they are appropriately set according to the material of the optical fiber.

When the optical fiber is used in an environment with a large temperature difference, it is preferable to anneal the optical fiber in order to suppress loosening. The conditions of the annealing treatment may be continuously or batchwise as long as they are appropriately set according to the material of the optical fiber.

In order to reduce the transmission loss of the optical fiber, the optical fiber can be subjected to wet heat treatment and warm water treatment. The conditions of the moist heat treatment and the warm water treatment may be set appropriately according to the material of the optical fiber, and may be continuous or batchwise.

After the optical fiber is subjected to wet heat treatment and warm water treatment, the optical fiber can be dried. The conditions of the drying treatment may be continuously or batchwise as long as they are appropriately set according to the material of the optical fiber.

(transmission loss)

The optical fiber of the present invention uses light with a wavelength of 400nm and a numerical aperture (NA) of 0.1. The transmission loss measured by the 25m-1m cut-off method is preferably 350dB/km or less, more preferably 300dB/km or less.

In addition, in this specification, the measurement of the cut-off method of 25m-1m is performed based on IEC60793-1-40:2001. Specifically, a 25-m optical fiber is installed in a measuring device, and after the output power P2 is measured, the optical fiber is cut to a cutback length ( ₁ m from the incident end), the output power P1 is measured, and calculated using the following formula ( ₁ ): Light transmission loss.

[number 1]

(coiling light retention rate)

In the cable bending test according to IEC60794-1:1993, the optical fiber of the present invention has a entanglement light retention rate of preferably 50% or more, more preferably 70% or more, when the diameter of the cylinder is 10 mm and the number of windings is 10 times.

In addition, in this specification, the cable bending test was performed according to IEC60794-1:1993. Specifically, a 10-m optical fiber is set in a measuring device, and after measuring the output power _P3 , the optical fiber is wound around a cylinder with a diameter of 10 mm slowly and at the same speed ₁₀ times, and the output power P4 is measured. The light quantity retention rate was calculated by the following mathematical formula (2).

Winding light retention rate (%) = (P ₃ /P ₄ )×100(2)

(coating layer)

The optical fiber of the present invention can be used as an optical cable by providing a coating layer on the outer periphery as necessary.

As the material constituting the coating layer, for example, olefin resins such as polyethylene resin and polypropylene resin; chlorine resins such as vinyl chloride resin and chlorinated polyethylene resin; fluorine resin; urethane resin; Amide resin, etc. These materials constituting the coating layer may be used alone or in combination of two or more.

The covering layer may be one layer or two or more layers.

(use)

Since the optical fiber of the present invention is heat-resistant, has low transmission loss, and is excellent in bendability, it can be used for, for example, communication equipment, lighting fixtures, decorations, displays, etc., and can be suitably used in communication equipment in particular.

Example

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.

(X-ray intensity from sulfur source)

Regarding the fluorine-based resin constituting the sheath material used in Examples and Comparative Examples, the X-ray intensity derived from elemental sulfur was measured. Specifically, according to JISK0119, a vacuum-dried fluorine-based resin was press-molded at 25°C as a sample, and the sulfur element was measured using a fluorescent X-ray analysis (machine model name "ZSX100e", manufactured by Rigaku Corporation) Source X-ray intensity.

In addition, the target range of the measurement is Na (sodium) to U (uranium) of the periodic table.

(Content rate of sulfur atoms)

The content of sulfur atoms in the fluororesins constituting the sheath materials used in Examples and Comparative Examples was calculated from the values of the above-mentioned X-ray intensities.

(transmission loss)

With regard to the optical fibers obtained in Examples and Comparative Examples, dry heat treatment at a temperature of 70°C and a relative humidity of 10% or less for 1000 hours was measured by a cut-off method of 25m-1m using light with a wavelength of 400nm and a wavelength of 650nm and a numerical aperture (NA) of 0.1 The transmission loss before and after (initial transmission loss and transmission loss after dry heat treatment).

In addition, the measurement of the cut-off method of 25m-1m was performed based on IEC60793-1-40:2001. Specifically, a 25-m optical fiber is installed in a measuring device, and after the output power P2 is measured, the optical fiber is cut to a cut _- back length (1 m from the incident end), the output power P1 is measured, and the optical power is calculated using the above-mentioned formula ( ₁ ). transmission loss.

(chromaticity coordinates)

The optical fibers obtained in Examples and Comparative Examples were wound along the bobbin for 1500 m, and measured using a spectrophotometer (machine model name "PMA-11", manufactured by Hamamatsu Photonics Co., Ltd.) with a halogen lamp (trade name "JCR12V100W10H", Iwasaki Electric Co., Ltd., 12V, 100W) is the value of the wavelength spectrum of the light leaked from the side of the optical fiber when the light as the light source is transmitted to the optical fiber. From the obtained value of the wavelength spectrum, the chromaticity coordinate x was calculated according to JISZ8701-1995.

(coiling light retention rate)

The optical fibers obtained in Examples and Comparative Examples were subjected to a cable bending test in accordance with IEC60794-1:1993, and the entanglement light quantity retention rate was measured. Specifically, a 10-m optical fiber is set in a measuring device, and after measuring the output power _P3 , the optical fiber is wound around a cylinder with a diameter of 10 mm slowly and at the same speed ₁₀ times, and the output power P4 is measured. The light quantity retention rate was calculated using the above-mentioned mathematical formula (2).

(Material)

In Examples and Comparative Examples, resins shown below were used as core materials or sheath materials.

Resin A: PMMA (refractive index 1.49)

Resin B: VDF/TFE copolymer (molar ratio 80/20, refractive index 1.40)

Resin C: VDF/HEP copolymer (molar ratio 85/15, refractive index 1.40)

Resin D: 2-(perfluorooctyl) ethyl methacrylate/2,2,2-trifluoroethyl methacrylate/methyl methacrylate/methacrylic acid copolymer (molar ratio 39/51 /9/1, index of refraction 1.40)

In addition, the X-ray intensity originating from sulfur element and the content rate of sulfur atoms are different in each of the Examples and Comparative Examples, as shown in Table 1, respectively.

[Example 1]

The melted resin A and resin B were respectively supplied to a spinning head at 220°C. Then, resin A as the core material and resin B as the sheath material (X-ray intensity derived from sulfur element: 0.05kcps, sulfur atom content: 4ppm, hereinafter referred to as resin B1) were used in a concentric two-layer structure. The fiber was spun with a circular composite spinning nozzle and stretched to 2 times along the fiber axis direction in a hot air heating furnace at 140°C to obtain an optical fiber with a core diameter of 990 μm, a sheath thickness of 5 μm, and a diameter of 1 mm.

Table 1 shows the evaluation results of the obtained optical fibers.

[Examples 2-5, Comparative Examples 1-4]

Except for changing the resin of the sheath material as shown in Table 1, the same operation as in Example 1 was performed to obtain an optical fiber.

Table 1 shows the evaluation results of the obtained optical fibers. In addition, in the table, B2 to B4, C1 to C3, D1, and D2 all represent resin B, C, or D, and mean resins having different sulfur atom content rates.

[Table 1]

As shown in Table 1, it can be seen that the optical fibers of the present invention obtained in Examples 1 to 5 have low transmission loss and excellent bendability. In addition, it can be seen that the transmission loss at a wavelength of 400 nm for light with a numerical aperture of 0.1 can be 350 dB/km or less after dry heat treatment.

On the other hand, as a result of the optical fibers obtained in Comparative Examples 1, 2, and 4, since the chromaticity coordinate x was outside the range of the present invention, the transmission loss was large, and the thermal stability of the transmission loss was also poor. In addition, the results of the optical fibers obtained in Comparative Examples 3 and 4 were poor in bendability because the fluorine-based resin of the sheath material was out of the scope of the present invention.

industry availability

Since the optical fiber of the present invention has low transmission loss and excellent heat resistance and bendability, it can be used, for example, in communication equipment, lighting fixtures, decorations, displays, etc., and can be suitably used in communication equipment in particular.

Claims (13)

1. An optical fiber is an optical fiber having a core and at least one sheath, The material constituting the sheath includes a fluororesin, The fluorine-based resin contains at least one selected from the group consisting of vinylidene fluoride units, tetrafluoroethylene units, and hexafluoropropylene units, The chromaticity coordinate x of the light leaked from the side when the light is transmitted using the halogen lamp as the light source is set to be x≦0.34. 2. The optical fiber according to claim 1, wherein the chromaticity coordinate x is x≦0.31. 3. The optical fiber according to claim 1, wherein the X-ray intensity derived from the sulfur element in the fluorine-based resin measured by fluorescent X-ray analysis is 0.6 kcps or less. 4. The optical fiber according to claim 1, wherein the X-ray intensity derived from the sulfur element in the fluororesin measured by fluorescent X-ray analysis is 0.3 kcps or less. 5. The optical fiber according to claim 1, wherein the content of sulfur atoms in the fluororesin is 20 ppm or less. 6. The optical fiber according to claim 1, wherein the fluorine-based resin contains 70% to 90% by mass of vinylidene fluoride units and 10% to 30% by mass of hexafluoropropylene units. 7. The optical fiber according to claim 2, wherein the fluorine-based resin contains 70% to 90% by mass of vinylidene fluoride units and 10% to 30% by mass of hexafluoropropylene units. 8. The optical fiber according to claim 1, wherein the fluorine-based resin contains 82% to 88% by mass of vinylidene fluoride units and 12% to 18% by mass of hexafluoropropylene units. 9 . The optical fiber according to claim 1 , which has a transmission loss of 350 dB/km or less as measured by a 25 m-1 m cut-off method using light with a wavelength of 400 nm and a numerical aperture of 0.1. 10 . The optical fiber according to claim 1 , in a cable bending test according to IEC60794-1:1993, the entanglement light retention rate is 50% or more when the diameter of the cylinder is 10 mm and the number of windings is 10 times. 11 . 11. An optical cable having a coating layer on the outer periphery of the optical fiber according to any one of claims 1 to 10. 12. A communication device comprising the optical fiber according to any one of claims 1-10. 13. A lighting fixture comprising the optical fiber according to any one of claims 1-10.