JP4933839B2 - Manufacturing method of plastic optical fiber cable - Google Patents

Description

   The present invention relates to a method for producing a plastic optical fiber cable used as a short-distance communication wiring for a moving body such as an automobile, an aircraft, a ship, a train, or the like, or an FA, a domestic device, an office device, etc. The present invention relates to a technique for making the coating state uniform when applying a plurality of coating layers to POF).

   POF has already been put into practical use for short-distance data communication wiring and sensor applications. At that time, it is often used in the form of a POF cable in which the outer periphery of the POF is protected with a covering material.

Regarding the configuration of such a POF cable, various POF cables having a plurality of coating layers have been proposed. For example, Patent Document 1 proposes a POF cable in which a vinylidene fluoride resin is provided on the outside of the POF as an adhesion layer and a polyamide resin is coated on the outside in order to improve the heat resistance and the adhesion between the POF and the coating layer. Has been. Patent Document 2 proposes a POF cable provided with three coating layers so as to satisfy various characteristics such as mechanical characteristics and chemical characteristics.
Japanese Patent Laid-Open No. 2000-275481

   In the POF cable disclosed in the above-mentioned Patent Document 1, in the manufacturing process, the process of applying the adhesion layer and the process of applying the coating layer are separate processes, so the thermal history applied to the POF increases. There was a tendency for the optical characteristics of the POF cable to be impaired. In addition, there is a problem that the manufacturing process increases and the manufacture of the POF cable becomes complicated.

   That is, an object of the present invention is to provide a production method for obtaining a POF cable excellent in optical characteristics by coating a thinned inner coating layer with a uniform thickness.

  As a result of intensive studies, the present inventors have combined the resin used for the coating inner layer of the POF cable and the resin used for the outer coating layer so that the relationship of their dynamic viscosities falls within a specific range, It has been found that the thinned inner coating layer can be coated to a uniform thickness, the coating process can be simplified, and the optical properties of the POF cable can be prevented from being lowered.

That is, the present invention is a method for producing a plastic optical fiber cable in which a coated inner layer is formed on the outer periphery of a plastic optical fiber having a core-sheath structure, and further, a coated outer layer is formed on the outer periphery thereof. When the shear viscosity of the coating material A forming the inner coating layer at 230 ° C. is η _A (Pa · s) and the shear viscosity of the coating material B forming the outer coating layer is η _B (Pa · s), the shear rate is the ratio η _a / η _B of the shear viscosity of the following areas 1000 / s or more 10000 / s in the range of formula (1), and when the thickness of the covering lining the d _a, the thickness of the coating layer and d _B In addition, the present invention relates to a method of manufacturing a plastic optical fiber cable that collectively coats the inner coating layer and the outer coating layer so that the thickness ratio d _B / d _A falls within the range of the following formula (2).
0.5 ≦ η _A / η _B ≦ 2 (1)
1.0 ≦ d _B / d _A ≦ 49 (2)

  According to the manufacturing method of the present invention, it is possible to provide a plastic optical fiber cable that can reduce the thickness of the inner coating layer without deteriorating optical characteristics and can be coated with a uniform thickness.

   Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2 and Table 1. FIG.

   FIG. 1 is a cross-sectional view showing an embodiment of a POF cable manufactured by the manufacturing method of the present invention. A coating inner layer A13 is formed on the outer periphery of the POF 12 including the core 11A and the first sheath 11B formed on the outer periphery of the core 11A and the second sheath 11C formed on the outer periphery of the first sheath 11B. B14 is formed.

   Here, as the POF 12, a known one can be used in addition to the configuration shown in FIG. 1, for example, a GI POF in which the refractive index of the core 11A continuously decreases from the center toward the outer periphery, and outward from the center. For example, a multi-layer POF in which the refractive index of the core 11A gradually decreases, and a multi-core POF in which a plurality of the cores 11A are surrounded by a sheath are combined. In particular, it is preferable to use a multilayer POF in order to increase the bandwidth of the POF and perform high-speed signal transmission. In addition, you may use what coat | covered the sheath 11B further on the outer periphery of GI type | mold POF or multilayer POF.

   Various types of highly transparent polymers are used for the core 11A, and the polymer is not particularly limited, but a polymer having a methyl methacrylate unit as a constituent unit is preferably used. More preferably, a methyl methacrylate homopolymer, a polymer having a methyl methacrylate unit as a main constituent unit, a polymer having a benzyl methacrylate unit as a main constituent unit, or a polymer having a fluorinated alkyl methacrylate unit as a main constituent unit. Among them, methyl methacrylate homopolymer is particularly preferable.

   The sheath formed on the outer periphery of the core may be formed from one layer or may be formed from a plurality of layers of two or more layers. As the resin for forming the sheath, a known material can be appropriately selected as a sheath material for plastic optical fibers such as a fluorinated methacrylate polymer, a vinylidene fluoride polymer, and a tetrafluoroethylene polymer.

   In order to sufficiently secure the mechanical properties, heat resistance and impact resistance of the POF cable, the sheath is formed of two or more layers, and the sheath layer located at the outermost layer has a tetrafluoroethylene (TFE) unit. It is preferable to use a fluorine-containing olefin resin having at least a structural unit and a heat of crystal fusion of 59 mJ / mg or less. As the fluorine-containing olefin resin containing a TFE unit, at least one of a TFE unit and a vinylidene fluoride (VdF) unit, a hexafluoropropylene (HFP) unit, or a perfluoro (fluoro) alkyl vinyl ether (FVE) unit is used. Copolymers obtained by polymerization, copolymers of VdF units, TFE units and hexafluoroacetone units, copolymers of TFE units, HFP units and ethylene units, etc., are limited thereto. It is not a thing. As a copolymerization component with a TFE unit, a VdF unit, an HFP unit, and an FVE unit are particularly preferable from the viewpoints of low cost, high transparency, and excellent heat resistance.

   Examples of the resin preferable as the sheath layer of the inner layer include known materials as the sheath material of POF such as a fluorinated methacrylate polymer and a vinylidene fluoride polymer. In particular, a fluorinated methacrylate polymer is preferable because it is easy to adjust the refractive index and is excellent in flexibility and workability while having good transparency and heat resistance.

   Such POF 12 can be produced by a known method such as a melt spinning method. In addition, when POF 12 is used in a high temperature environment of about 70 to 105 ° C. or in an environment with a large temperature difference, annealing may be performed continuously or batchwise to suppress pistoning.

   The POF cable obtained by the production method of the present invention includes at least a coating inner layer in contact with the outside of the POF and a coating outer layer positioned on the outer periphery thereof.

   The coating material A used for the coating inner layer has a function of improving the adhesion between the outer periphery of the POF and the coating material B used for the coating outer layer, a low molecular weight substance existing in the coating material B, a coloring pigment, a plasticizer, etc. Is required to prevent the system from moving into the POF. As such a coating material A, a known resin can be used as a coating material for a POF cable, but in order to obtain a POF cable having high heat resistance, a methyl (meth) acrylate unit is a main constituent unit. Resin, resin having styrene unit as main structural unit, resin having polycarbonate as main component, resin having propylene unit as main structural unit, resin having ethylene-vinyl alcohol copolymer as main component, polybutylene terephthalate as main component It is preferable to use as the coating inner layer at least one of the resin and the resin mainly composed of polyvinylidene fluoride.

   The coating material B used as the coating outer layer has a function of improving chemical resistance, a function of preventing the incidence of external light, a function of improving mechanical strength, a function of improving heat resistance, and the like. Required. Examples of such a coating material B include polyamide resins, polyvinyl chloride resins, polyethylene resins, polypropylene resins, chlorinated polyethylene resins, polyurethane resins, fluorine resins, ethylene-vinyl acetate copolymers, or 2 of these resins. Mention may be made of mixtures obtained using more than one species. In particular, when a POF cable is used as an in-vehicle wiring, it is preferable to use a polyamide-based resin as a material having functions such as chemical resistance, mechanical strength, and heat resistance.

   More specifically, as the polyamide-based resin, a homopolymer such as nylon 11, nylon 12, nylon 6, nylon 66, nylon 6-12, or a nylon copolymer comprising a combination of monomer units of these polymers, A nylon elastomer in which a flexible segment is introduced into these polymers, or a mixture containing a nylon elastomer and another polyamide resin is preferable.

   Further, these coating materials B may contain a light shielding material such as carbon black in order to give a function of preventing the outside light from entering the POF.

   Furthermore, as a POF cable, a coating layer may be formed on the outer periphery of the coating outer layer.

   When the POF cable having such a structure is manufactured, the POF is coated using an extrusion coating apparatus equipped with a crosshead die in the coating step of applying a coating layer to the POF. The coating material A and the coating material B forming the outer layer are collectively covered.

  The coating temperature T (° C.) when the coating layer is applied to the POF is preferably 190 ≦ T ≦ 230. If the temperature is lower than 190 ° C., the resin to be coated is not sufficiently melted and becomes a lump, resulting in a large variation in the thickness of the coating layer, or a poor flow of the coating resin in the coating apparatus piping, causing insufficient resin discharge, Thickness control becomes difficult. On the other hand, when the coating temperature T is higher than 230 ° C., the POF is likely to be melted, which may cause fluctuations in the outer diameter due to the coating resin supply pressure in the coating process, and may increase transmission loss due to thermal degradation. In order to control the thickness of the coating layer to be thinner and more uniform and maintain the optical properties of the POF, it is more preferable that the coating temperature T is in the range of 200 ≦ T ≦ 220.

  In the present invention, in order to more uniformly control the thickness of the two coating layers, the relationship between the shear viscosity η of the coating material A and the coating material B at a coating temperature T ° C. (190 ≦ T ≦ 230) is constant. It is important to control the range.

More specifically, at the above-described coating temperature T ° C. (190 ≦ T ≦ 230), the shear viscosity η _{A (} Pa · s) at the coating temperature T of the coating material A used for the coating inner layer, and outside the coating inner layer. Regarding the shear viscosity η _B (Pa · s) of the coating material B used for the outer coating layer at the temperature T, the ratio η _A / η _B between η _A and η _B in the region where the shear rate range is 1000 / s to 100,000 / s. _B (shear viscosity ratio) must be in the range of the following formula (2).

0.5 ≦ η _A / η _B ≦ 2 (2)

Here, the range of the shear rate set to 1000 / s or more and 100000 / s or less is a coating resin present in a resin flow path formed by a crosshead die, a die, and a nipple used in a coating apparatus at the time of coating. It is set based on the shear rate of the material.

If the value of the shear viscosity ratio η _A / η _B is greater than 2, that is, the relative viscosity of the coating material A with respect to the coating material B is increased, the resin material B is prevented from evenly flowing outside the resin material A. The thickness of the inner layer of the coating becomes non-uniform such as a petal shape. When the value of η _A / η _B is smaller than 0.5, that is, when the relative viscosity of the coating material A to the coating material B is small, a uniform layer of the resin material A can be formed inside the resin material B. Therefore, the thickness unevenness of the layer becomes large.

In order to control the thickness of the coating inner layer thinner and more uniformly, the shear viscosity ratio is preferably in the range of the following formula (3).

0.7 ≦ η _A / η _B ≦ 1.5 (3)

Further, in order to realize effectively the functions of both of the coating materials A and B, the relationship between the thickness of the coating inner and outer layers, the thickness of the covering the inner layer d _A, the thickness of the coating layer as d _B, the following It is necessary to make it the range of Formula (1).

1.1 ≦ d _B / d _A ≦ 49 (1)

Low molecular weight substance and present in the coating material B, colored pigments, in order to plasticizer is sufficiently prevented transition to POF interior, the thickness of the coating inner layer is is better to thick as possible, d _B When the value of / d _A is smaller than 1.1, the chemical resistance and mechanical strength of the outer coating layer are greatly reduced, which is not preferable. On the other hand, in order to improve the adhesion between the POF and the coating layer, the thickness of the coating inner layer should be as thin as possible. However, when the value of d _B / d _A is larger than 49, the effect of preventing the transition of the coating inner layer is large. It will decline.

For this reason, although d _B / d _A is required to meet the above range, the value of d _B / d _A is more preferably from _{1.5 ≦ d B / d A ≦} 25, More preferably, 5 ≦ d _B / d _A ≦ 12.5.

  Next, a crosshead coating apparatus used for manufacturing the POF cable of the present invention will be described. FIG. 2 shows a die portion attached to the tip of the crosshead. The central axis 25 is a POF passage, and the coating material A that forms the coating inner layer passes through the first flow path 23, and the coating material B that forms the coating outer layer passes through the second flow path 24, and Both merge. Thereafter, the third flow path 26 joins the central axis 25 at an angle θ, and the coating materials A and B are coated with POF, and a POF cable is manufactured.

   Here, the angle θ (°) formed by the third flow path 26 and the center line 25 of the POF is preferably in the range of 10 degrees to 60 degrees. That is, it is preferable that the POF and the coating material A and the coating material B are in contact with each other at 10 to 60 degrees. If θ is less than 10 degrees, it tends to be difficult to coat the coating material A and the coating material B on the POF with a uniform thickness, while if it exceeds 60 degrees, the heat given to the POF by the material heated to a high temperature. In some cases, the stress increases and the optical properties of the POF deteriorate. In order to form the coating inner layer thinner and more uniformly, it is more preferable to set θ in the range of 20 degrees to 45 degrees.

   In the case where a coating layer is further provided outside the present invention, the coating temperature and the contact angle with POF are preferably within the above ranges.

Hereinafter, the present invention will be described by way of examples, but the scope of the present invention is not limited to these examples.
Each evaluation method in the examples is as follows.

(MFR)
Using a melt indexer (L217-1531) manufactured by Techno Seven, measurement was performed under the conditions of a measurement temperature of 210 degrees and a load of 5 kgf based on the JIS K 7210A method.

(Shear viscosity η)
Using a twin capillary rheometer (RH7-2) manufactured by Rosand, the shear viscosity at a shear rate of 1000 to 100,000 (/ s) was measured under conditions of a die diameter of 1 mm, a die total length of 16 mm, a measurement temperature of 210 degrees, and conditions.

(Cross sectional shape judgment)
After polishing a single surface of the plastic optical fiber cable with # 8000 polishing paper, the cross-sectional state was visually observed with a microscope. The case where the coating inner layer and the coating outer layer are coated with a uniform thickness is excellent (represented by ◎ in the table), and the outer shape is slightly deformed, but there is no significant variation in thickness (represented by ○ in the table). ), Those having a non-uniform thickness and large fluctuations were judged as defective (represented by x in the table).

[Example 1]
Methyl methacrylate (MMA) homopolymer (PMMA) as the core material and 2,2,2-trifluoroethyl methacrylate (3FM) / 1,1,2,2-perfluorodecyl methacrylate (17FM) as the sheath material / MMA / methacrylic acid (MAA) = 31/50/18/1 (wt%) copolymer, and as a protective layer, vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene = 70/20/10 (mol %) Copolymers were melted and concentrically laminated in order from the center and composite spun to obtain POF12 having a core diameter of 970 μm, a sheath thickness of 5 μm, and a protective layer thickness of 10 μm.

Then, ethylene-vinyl alcohol copolymer (Eval F104B Kuraray Co., Ltd .: MFR25, η _{A =} 70) is used as the coating material A, and nylon 12 (Daiamide 12 L1640, manufactured by Daicel Huls Co., Ltd .: MFR113, η _{B =} ) is used as the coating material B. 50), these are supplied to a compression type cross-head type coating apparatus for a two-layer batch coating whose cross section is shown in FIG. 2, and coating materials A and B are collectively coated on the outer periphery of the POF 12 to obtain an outer diameter of 1 A 5 mm POF cable was obtained. At this time, the thickness d _A of the coating layer A is 30 μm, the thickness d _B of the coating material B is 220 μm, that is, d _B / d _A is 7.3, the resin temperature T during coating is 210 ° C., and the die 21 is The thickness was 3 mm, the hole diameter of the die 21 was 1.5 mm, and two types with an angle θ between the third flow path 26 and the POF central axis 25 of 35 ° and 45 ° were used. The cross-sectional shape of the POF cable thus obtained was excellent in covering state.

(Example 2 to Example 8)
Coating was performed in the same manner as in Example 1 except that the coating material A was changed to the material shown in Table 1, and the cross-sectional shape was observed. The results are shown in Table 1.

(Comparative Examples 1 and 2)
The coating material A was coated in the same manner as in Example 1 except that polystyrene (MFR34, η _A = 24) or polycarbonate (MFR20, η _A = 101) was used, and the cross-sectional shape was observed. As a result, the cross section had a large thickness unevenness and was poor.

In addition, the symbol in a table | surface shows the following content.
EVALA: ethylene-vinyl alcohol copolymer (EVAL F104B manufactured by Kuraray Co., Ltd.)
EVALB: ethylene-vinyl alcohol copolymer (EVAL F101B manufactured by Kuraray Co., Ltd.)
PBT A: Polybutylene terephthalate (Hytrel 4047 manufactured by Toray DuPont)
PBT B: Polybutylene terephthalate (Hytrel 4767 manufactured by Toray DuPont)
PBT C: Polybutylene terephthalate (Hytrel 2474 manufactured by Toray DuPont)
AcrylA: 17FM / MMA / MAA copolymer (composition ratio: 30/68/2% by mass)
Acryl B: 17FM / MMA / MAA copolymer (composition ratio: 14/84/2% by mass)
AcrylC: BA / MMA / MAA copolymer (composition ratio: 10/88/2% by mass)
3FM: trifluoroethyl ethacrylate 17FM: 1,1,2,2-perfluorodecanyl methacrylate MMA: methyl methacrylate MAA: methacrylic acid PS: polystyrene (HIPS433 manufactured by PS Japan)
PC: Polycarbonate (OQ1020 manufactured by GE Plastics)
PA12: Polyamide 12 (L1640, manufactured by Daicel Degussa)

It is sectional drawing which shows an example of the POF cable obtained by the manufacturing method of the POF cable of this invention. It is a longitudinal cross-sectional view which shows an example of the coating | coated apparatus used for the manufacturing method of the POF cable of this invention.

Explanation of symbols

10 ... POF cable 11A ... core 11B ... first sheath 11C ... second sheath 12 ... POF
13 ... Coating inner layer 14 ... Coating outer layer 21 ... Die 22 ... Nipple 23 ... First flow path 24 ... Second flow path 25 ... Center axis 26 of POF 12 ... Third flow path θ ・ ・ ・ Taper angle of die nipple

Claims (3)

On the outer periphery of a plastic optical fiber having a core-sheath structure, a resin mainly composed of a methyl (meth) acrylate unit, a resin mainly composed of an ethylene-vinyl alcohol copolymer, and polybutylene terephthalate are principally composed. to form a coating inner layer is formed using at least one resin of the resin, a further plastic optical fiber manufacturing method of the cable for forming a coating layer on the outer periphery thereof, the coating temperature T and 190 ° C. ≦ T ≦ 230 ° C. When the shear viscosity of the coating material A forming the inner coating layer at the coating temperature is η _A (Pa · s) and the shear viscosity of the coating material B forming the outer coating layer is η _B (Pa · s), the shear rate There was a ratio η _a / η _B of the shear viscosity of the following areas 1000 / s or more 10000 / s in the range of formula (1), and the thickness of the covering the inner layer d _a, coated When the thickness of the layer was set to d _B, a manufacturing method of the plastic optical fiber cable the ratio d _B / d _A thick coats collectively the coating inner layer and the coating layer to be in the range of the following formula (2) .
0.5 ≦ η _A / η _B ≦ 2 (1)
1.0 ≦ d _B / d _A ≦ 49 (2) The method of manufacturing a plastic optical fiber cable according to claim 1, wherein the coating material A and the coating material B are introduced into the die at an angle of 10 degrees to 45 degrees with respect to the plastic optical fiber. 3. The method for producing a plastic optical fiber cable according to claim 1, wherein the coating material B is made of a polyamide-based resin.

Images