JPH0416904A - Manufacture of plastic optical fiber and compound spinning nozzle used for the manufacture - Google Patents

Abstract

PURPOSE:To obtain a plastic optical fiber with a small transmission loss by using a compound spinning nozzle whose acute angle at the interface side of both a resin for coating and a resin for sheath material layer is less than 60 deg. formed by the running direction of the former and that of the latter. CONSTITUTION:The compound spinning of the resin for coating and the resin for sheath material layer with refractive index less than that of the resin for coating is performed by using the compound spinning nozzle. In such a case, the compound spinning nozzle is provided with a resin introduction hole 2 for sheath material layer provided in such a way that the running direction of the resin for sheath material layer is provided obliquely against the center line of a resin instroduction hole 1 for coating so as to make an angle less than 60 deg., more desirable, less than 45 deg. at the interface side of both resin. Thereby, since non-matching of interface between a coating material and a sheath material can be reduced, the plastic optical fiber with small amount of optical transmission loss can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a plastic optical fiber and a composite spinning nozzle used in the method.

More specifically, the present invention relates to a method for manufacturing a plastic optical fiber suitable for use in the electric/electronic field and the automobile field, for example, as a plastic optical fiber to be placed in the engine room of an automobile, and a composite spinning nozzle used in the method. .

[Prior art and the problem to be solved by the invention] In recent years,
As optical fibers for optical transmission, we are developing plastic optical fibers that are more resistant to bending stress, easier to connect, easier to handle, and cheaper than the inorganic glass optical fibers that have been widely used in the past. It is being put into practical use.

This plastic optical fiber is composed of a core material made of a polymer with excellent light transparency and a sheath material layer made of a polymer with a lower refractive index than the core material and excellent transparency. It is commonly produced by extruding these two materials into a two-layered fiber using a composite spinning machine.

One of the important things in such a manufacturing method is the irregularity of the interface between the core material and the sheath material layer, which is one of the causes of transmission loss in plastic optical fibers.

By reducing this, a plastic optical fiber with low optical transmission loss can be obtained.

As a technology with such ingenuity, Japanese Patent Application Laid-Open No. 53-4
No. 2261 and Japanese Unexamined Patent Publication No. 57-46204 disclose a method in which the flow of the resin on the side forming the side interface of the composite spinning nozzle is set at 90 degrees when producing plastic optical fibers by the composite spinning method. .

However, in all of these, by using one in which the flow path of the core material and the glass material form a 90 degree angle, the resulting plastic optical fiber has a circularity of the interface between the core material and the sheath material in its cross section. The plastic optical fibers have the disadvantage that they have poor optical properties and are also wavy in the longitudinal direction.As a result, the resulting plastic optical fibers have the problem of not being able to sufficiently reduce optical transmission loss.

This invention has been made based on the above circumstances.

The object of the present invention is to provide a method for manufacturing a plastic optical fiber, which makes it possible to obtain a plastic optical fiber with low transmission loss by using a composite spinning nozzle for reducing the irregularity of the interface between a core material and a sheath material, and to provide such a manufacturing method. An object of the present invention is to provide a composite spinning nozzle suitable for carrying out the method.

[Means for Solving the Problems] The first invention of the present application for solving the above problems provides an optical fiber comprising a core material made of plastic and a sheath material layer made of a plastic material having a lower refractive index than the core material. In the method for producing plastic optical fibers by a composite spinning method, the composite spinning is an acute angle formed by the flow direction of one core resin and the flow direction of the sheath resin, and the angle between the two resins is at an acute angle or within 60 degrees. There is a method for manufacturing a plastic optical fiber characterized by using a nozzle, and the second invention is a composite spinning nozzle used in a composite spinning method, which is characterized in that the flow direction of a core resin and the sheath resin are controlled. Composite spinning characterized by having a resin introduction hole for the sheath material layer that is inclined with respect to the resin introduction hole for the core material so that it is within an acute angle of 60 degrees on the interface side of both resins formed in the flow direction. It's a nozzle.

Next, the structure of the composite spinning nozzle used in the manufacturing method of the present invention will be explained, and the manufacturing method of the present invention will be explained in detail.

One Composite Spinning Nozzle As shown in FIGS. 1 and 2, the composite spinning nozzle of the present invention has two sheath material layers with respect to the center line A of the core resin introduction hole 1 into which the core material resin is introduced. Is it the flow direction of the resin?
60 degrees or less on the interface side of both resins, preferably 45 degrees
It has a resin introduction hole 2 for the sheath material layer which is provided with an inclination of less than 30 degrees.

If this angle exceeds 60 degrees, the interface between the core material 3 and the sheath material layer 4 will become irregular.

Furthermore, the finishing accuracy of the inner surface of the connection part B between the core material resin introduction hole and the sheath material layer resin introduction hole in the composite spinning nozzle (the shaded area in FIG. 1) has a surface roughness of 0.4-S or less. ,
Preferably, it is 0.1-3 or less.

If the surface roughness is rougher than 0.4-S, the interface between the core material and the sheath material layer may become irregular.

Further, the L/D of the composite spinning nozzle is preferably within the range of 0.1 to 1O. (However, L is the length from the connection part of the resin introduction hole for the sheath material layer with the resin introduction hole for the core material to the nozzle outlet, and D is the diameter of the nozzle exit.) In addition, the sheath material described later When producing a plastic optical fiber using a fluorine-containing polymer among the resins used in the layer, it is preferable that the material of the composite spinning nozzle is Ni or an alloy containing mainly Ni or Mo JPCr. By using a Ni-Mo-Cr alloy, the corrosion resistance against the corrosive properties of fluorine is increased.

By the composite spinning method using the composite spinning nozzle having the above-described structure, it is possible to manufacture a plastic optical fiber with low optical transmission loss using conventionally known resins for the core material and resins for the sheath material.

- Method for manufacturing a plastic optical fiber - A preferred embodiment of the method of the present invention uses a composite spinning nozzle having the above structure, and uses a resin for the core material and a resin for the sheath material layer having a lower refractive index than the resin for the core material. Its content is to provide composite thread protection for and.

The plastic optical fiber manufactured by the method of the present invention has a core material made of plastic (resin for core material) with excellent light transmittance, and a plastic material with a refractive index smaller than that of the core material and with excellent transparency. (resin for sheath material layer).

1M The plastic used as the core material may be any polymer whose refractive index is 0.01 or more higher than the refractive index of the sheath material layer and has excellent transparency. Examples of such plastics for the core material include methacrylic polymers, polycarbonates, polystyrene, styrene-methacrylate copolymers, polyolefins, or those polymers in which all or some of the hydrogen atoms have been replaced with deuterium atoms. Mention may be made of transparent non-grade thermoplastic resins such as deuterated polymers. Furthermore,
Blends of the various polymers mentioned above or amorphous polymers other than those mentioned above may also be used as the plastic for the core material.

As the plastic for the core material, methacrylic resins and polycarbonate-based 4# resins are preferred, and polycarbonate-based resins are particularly preferred.

(2) Polycarbonate Resin As the polycarbonate resin, one type or, if necessary, two or more types can be selected and used from various types of known polycarbonate resins.

Specific examples of the polycarbonate resin include various types, but preferred examples include alicyclic polycarbonates represented by the following general formula, and aromatic polycarbonates represented by R in the general formula. I can list many things.

Furthermore, copolymers of these and dihydroxy compounds such as 4,4'-dihydroxydiphenyl ether, ethylene glycol, P-phenylene glycol, and 1,6-hexanediol can also be used. The polycarbonate resin may have a partially branched structure.

There are no particular limitations on the method for producing the polycarbonate resin in the present invention, and examples include the phosgene method, which involves the reaction of dihydric phenols with phosgene, and the reaction between dihydric phenols and carbonic acid esters such as diphenyl carbonate. A transesterification method, a method of reacting a dihydric phenol with a heroformate such as chloroformate, etc. can be suitably employed.

Examples of the dihydric phenols include hydroquinone, 4.
4'-dihydroxybiphenyl, bis(hydroxyphenyl)alkane, bis(hydroxyphenyl)cycloalkane, bis(hydroxyphenyl)ether, bis(
Examples include N analytes such as hydroxyphenyl) sulfide, bis(hydroxyphenyl)sulfone, lower alkyl thereof, and halogen.

Among these dihydric phenols, for example, 2.2
-Bis(4-hydroxyphenyl)propane [hereinafter sometimes referred to as bisphenol A]. ], l, l-bis(
4-hydroxyphenyl)ethane, 2,2-bis(4-
Hydroxyphenyl)-hexafluoropropane and the like are preferred.

Further, these dihydric phenols may be used alone or in combination.

The polycarbonate resin used for the core material preferably has a molecular weight within an appropriate molecular weight range, and generally has a viscosity average molecular weight of 20,000 to 28,000,
It is preferably within the range of 000, especially 20.5
0[1 to 27,000 is preferred.

The polycarbonate resin used for the core material has a viscosity average molecular weight of 20,000 to 28,000, for example.
By using a material within an appropriate range, such as within the range of , it is possible to easily ensure sufficient strength and good moldability of the plastic optical fiber.
Improvements in optical properties such as transparency, refractive index, and optical transmission loss of plastic optical fibers can also be easily ensured.

The viscosity average molecular weight of the polycarbonate resin can be easily adjusted by adjusting the amount of a terminal capping agent such as P tert-butylphenol in the polymerization reaction during the production of the polycarbonate resin.

In addition, the polycarbonate resin used for the core material is
The weight average molecular weight (M w
) and the number average molecular weight (M n ) [M w / M
n (GPC method)] is generally preferably within the range of 2.0 to 2.6, particularly preferably within the range of 2.0 to 2.4. Further, the polycarbonate resin can be obtained by treating the polymer obtained during production with a solvent such as acetone to obtain a low molecular weight component [M w ; 3,
000 or less] is preferably removed.

Furthermore, the polycarbonate resin preferably has a low content of halogenated hydrocarbons, particularly 15 ppm.
It is preferable that it is less than m.

The polycarbonate resin constituting the core material in the present invention preferably has a foreign matter strength of 1 x 105 gm2/g or less, and in particular, 5xl [l'p, m27 g or less, which can further reduce optical transmission loss. It is preferable.

Furthermore, by forming the core material from the polycarbonate resin, its refractive index can be made to a sufficiently high level as a core material of an optical fiber. This refractive index varies depending on the type of polycarbonate resin used, and in the case of hisphenol A polycarbonate, it usually has a value of around 1.586.

On the other hand, from the perspective of heat resistance, the heat deformation humidity is 12
It is preferable to use a polycarbonate resin having a temperature of 0° C. or higher. Here, heat distortion temperature is ASTM D
-648, and refers to the measured value at a load of 4.6 kg/cm2.

As mentioned above, it is advantageous to use a resin derived from bisphenol A as the polycarbonate resin used in the present invention. Most preferably, polycarbonates made by interfacial polycondensation at temperatures below 50°C are used.

■Methacrylic resins Examples of methacrylic resins include, for example, homopolymers or copolymers of methyl methacrylate (7% of the starting material).
Preferably, 0% by weight or more is methyl methacrylate and 30% by weight or less is other polymers copolymerizable with methyl methacrylate. Examples of the polymers copolymerizable with methyl methacrylate include vinyl polymers such as methyl acrylate and ethyl acrylate.

In addition, cyclohexyl methacrylate, t-butyl methacrylate, and isobornyl methacrylate.

Examples include copolymers of methacrylic acid esters such as adamantyl methacrylate, benzyl methacrylate, phenyl methacrylate, and naphthyl methacrylate and monomers copolymerizable with these esters. Among these, homopolymers and copolymers of methyl methacrylate are preferred.

One sheath material layer one As for the polymer used as the sheath material layer.

The refractive index of the core component polymer is 0. Smaller than O1,
There is no particular restriction as long as it is a transparent polymer.

Examples include polymethyl methacrylate, poly-4-methylpentene-1, polyarylate, silicone resin, and fluororesin.

Specific examples of such polymers for the sheath layer include:
Polymethyl methacrylate, styrene-methyl methacrylate copolymer, poly-4-methylpentene-1,
Ethylene-vinyl acetate copolymer, silicone acrylate resin, urethane acrylate resin, fluorine-containing polymethyl methacrylate, polycarbonate, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, methyl methacrylate - Styrene, vinyltoluene or α-methylstyrene/maleic anhydride ternary or quaternary copolymers. In addition, when a polycarbonate resin is used as the core material, a terpolymer of vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene, a copolymer of methyl methacrylate, or a copolymer of methyl methacrylate can be used as the sheath material layer. Polycarbonate having a structure represented by the following formula is particularly preferred in terms of low optical transmission loss.

Among these, fluorinated polycarbonate polymers are preferred because they have good heat resistance and good compatibility with the core material polymer.

However, a and b in the above formula represent the respective molar amounts of repeating units in the polymer.

The polycarbonates represented by the formulas (1,) and (II) that are suitable for the sheath material layer are those represented by the formulas (I) and (I).
It may be a block copolymer or a random copolymer of the two types of repeating units in I), and a random copolymer is preferred.

Further, in the above formulas (1) and (II).

It is desirable to set the value of (a/a+b)xlooo to 20 or more; if this value is less than 20, optical transmission loss may increase. Note that b may be 0, or
The glass transition temperature (Tg) of the polycarbonate represented by the formula ('I) is usually 157° C. or higher, and the refractive index is 1.57 or lower.

In this way, when a fluorine-containing polymer is used for the sheath material layer, it is desirable that the material of the composite nozzle is N1 alloy as described above.

These polymers are used to improve peel strength
Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid, unsaturated glycidyl monomers such as diglycidyl acrylate or methacrylate, β-methylglycidyl acrylate or methacrylate, acrylamide, methacrylamide, and derivatives thereof, hydroxyalkyl acrylate, or methacrylate You may also copolymerize hydrophilic molecules such as.

Examples of highly versatile materials include methacrylic polymers such as polymethyl methacrylate, and polymers obtained by polymerizing esters made of methacrylic acid and fluorinated alcohols.

Specific examples of the esters include methacrylic acid 2,2
．． 2-trifluoroethyl, methacrylic acid 2,2,3.
3-tetrafluoropropyl, methacryl $2.2,3
, 3.3-pentafluoropropyl and the like.

Using one or more of these fluorine-containing methacrylic acid esters, a copolymer consisting of a vinyl monomer that can be copolymerized with the same and a vinyl monomer that can form a hydrophilic homopolymer is used. You can also do that.

1. Manufacturing method 1. The plastic optical fiber of the present invention is manufactured by composite spinning a core material resin and a sheath material layer resin having a lower refractive index than the core material resin using the composite spinning nozzle having the above configuration, as described above. I have something to do.

In the method of this invention, the temperature of the composite spinning nozzle is
It is preferable to carry out composite spinning at a temperature of 35 to 280°C, particularly 240 to 270°C.

Furthermore, the take-up speed of the molten plastic optical fiber discharged from the composite spinning nozzle having the above structure is 8 to 2.
A range of 0 m/sin is preferable. By matching the extrusion speed and withdrawal speed of the molten resin, it is possible to produce a plastic optical fiber free from interfacial irregularities.

In addition, in the method of this invention, the air gap is
It is preferable to cool the fiber to a thickness of 00 to 1,300 mm and then perform composite spinning.

The temperature of the composite spinning nozzle is set within the range of 235-280°C for extrusion, and the air gap is set at 700-1. :
By setting it at 100 am, it is possible to always stably and easily manufacture plastic optical fibers with small fluctuations in roundness and outer diameter and low optical transmission loss.

Cooling by the air gap may be natural cooling at room temperature or forced cooling. Further, in composite spinning, a spinning tube may be provided in a part between the composite spinning nozzle and the take-off machine.

Plastic optical fibers manufactured in this manner generally have an outer diameter of 400 to 1. The thickness of the sheath material layer is approximately 1 to 50 m.

Furthermore, the sheath material layer is further coated with a protective layer.

It is also possible to produce plastic optical fibers with a protective layer.

The plastic optical fiber manufactured by this invention is a
l Excellent mechanical strength and heat resistance, and low optical transmission loss,
Plastic optical fibers can be suitably used in fields where conventional plastic optical fibers have not been applicable, such as sensor means and optical communication means in electrical, electronic, and automobile fields.

[Example] Next, an example of the present invention will be shown and the present invention will be explained in more detail.

(Example 1) A polycarbonate containing repeating units derived from bisphenol A was used as the core polymer, and a copolymer consisting of 80% by weight of methyl methacrylate and 20% by weight of isobornyl methacrylate was used as the polymer for the sheath material. 2
From a screw melt extruder set at 70°C and 230°C, an angle of 30 degrees at the lamination point, a finishing accuracy of 0.1-5,
A composite spinning nozzle of material 5US304 was fed to form a core/sheath structure.

Next, it was extruded through a nozzle, cooled and solidified, and then pulled out at a speed of 20 m/inch/min to obtain an optical fiber.

The interface irregularities of the optical fiber thus obtained were measured.

Interfacial irregularity evaluation method: The obtained optical fiber was cut in a direction perpendicular to the fiber axis, the cross section was observed with an optical microscope, and the diameter of the core was measured every 26 minutes. The variation in the diameter of the core was defined as interface irregularity, and was expressed as a CV value. Since the fiber is not elliptical, a large Cv value indicates a large interfacial irregularity.

(However, CV value=σ/X [σ: standard deviation, X: average value]) Furthermore, optical transmission loss was measured using a light source with a wavelength of 6600 square meters.

The results are shown in Table 1.

(Comparative Example 1) The same procedure as in Example 1 was carried out except that the angle at the lamination point was set to 90°.

The results are shown in Table 1.

(Example 2) Copolymerizing a polymer mainly composed of methyl methacrylate containing 5 mol% methyl acrylate as a core material polymer with tetrafluoroethylene containing 70 mol% vinylidene fluoride as a sheath material polymer. Combine at 230℃ and 2
The material was supplied from a screw melt extruder set at 40°C to a composite spinning nozzle made of Hesteroy C, with an angle of 45° at the lamination point, a finishing accuracy of 0.1-S, and a core/sheath structure.

Next, it was extruded from a nozzle, cooled and solidified, and then taken off at a speed of 20 m/sin per minute to obtain an undrawn yarn.

Furthermore, this undrawn yarn was stretched 1.5 times at 140°C,
I got an optical fiber.

The interface irregularities and optical transmission loss of the optical fiber thus obtained were measured in the same manner as in Example 1.

The results are shown in Table 1.

(Comparative Example 2) The same procedure as in Example 2 was carried out except that the angle at the lamination point was set to 90'.

The results are shown in Table 1.

(Hereinafter, blank space) [Effects of the Invention] According to the manufacturing method of the present invention, the unevenness of the interface between the core material and the sheath material is reduced in the resulting plastic optical fiber, thereby providing a plastic optical fiber with low optical transmission loss. I can do that.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a composite spinning nozzle used in the manufacturing method of the present invention, and FIG. 2 is an end view of FIG. 1. DESCRIPTION OF SYMBOLS 1... Resin introduction hole for core material, 2... Resin introduction hole for sheath material layer, 3... Core material, 4... Sheath material layer. Figure 2

Claims (2)

[Claims] (1) In a method for producing a plastic optical fiber, in which an optical fiber is made of a core material made of plastic and a sheath material layer made of a plastic material having a lower refractive index than the core material, by a composite spinning method, the flow of the resin for the core material A method for producing a plastic optical fiber, characterized in that a composite spinning nozzle is used in which an acute angle on the interface side between both resins formed by the flow direction of the sheath material layer resin and the flow direction of the resin for the sheath material layer is within 60 degrees. (2) A composite spinning nozzle used in the composite spinning method, in which the acute angle between the flow direction of the core resin and the flow direction of the sheath resin on the interface side of both resins is within 60 degrees. A composite spinning nozzle characterized in that the resin introduction hole for the sheath material layer is inclined with respect to the resin introduction hole for the core material layer.