JPH0416905A - Manufacture of plastic optical fiber - Google Patents

Abstract

PURPOSE:To easily and stable produce an optical fiber with high performance in which optical transmission loss is sufficiently reduced further in addition to the full use of superior characteristic of polycarbonate group resin by applying annealing treatment on an optical fiber material at 60-100 deg.C for 5 minutes to 72 hours, and annealing it at a cooling rate less than 1 deg.C/min. CONSTITUTION:A plastic optical fiber 1 is comprised of at least a coating material 2 made of polycarbonate group resin and a seath material layer 3 made of plastic with refractive index less than that of the coating material 2. In such a case, the annealing treatment is applied to the optical fiber material at 60-100 deg.C for five minutes to 72 hours, thence, it is annealed at the cooling rate less than 1 deg.C/min. Thereby, it is possible to easily and stable produce the optical fiber with high performance in which the optical transmission loss can be sufficiently reduced further without lowering the superior characteristic of the polycarbonate group resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a plastic optical fiber.

More specifically, the present invention relates to a method of manufacturing a plastic optical fiber with low optical transmission loss, which can be suitably used, for example, in the electric/electronic field, the automobile field, etc.

[Prior Art and Problems to be Solved by the Invention] Conventionally, as optical fibers, inorganic glass optical fibers made of inorganic glass such as quartz glass have been used for industrial, medical, decorative, or information transmission purposes. Widely used.

However, inorganic glass optical fibers such as quartz optical fibers have fundamental drawbacks of being expensive, heavy, and having poor flexibility.

Therefore, compared to inorganic glass optical fibers such as quartz optical fibers, plastic optical fibers have been developed and put into practical use, as they have the advantages of being lightweight, resistant to bending stress, easy to handle, and inexpensive.

Such plastic optical fibers generally have a core material layer made of a resin with excellent light transmittance, and a core material layer that has a refractive index smaller than that of the core material and has excellent adhesive properties with the core material. It is preferable that the sheath material (crat material) layer is made of resin, for example, polycarbonate 5l11.
! Plastic optical fibers using the core material as the core material have been proposed (JP-A-61-6604, JP-A-61-2).
(See Publication No. 62706).

Optical fibers whose core material is polycarbonate have excellent performance in various respects, and are superior to other plastic optical fibers, including those whose core material is polymethyl methacrylate (PMMA). , # is overwhelmingly superior in terms of heat resistance, impact resistance, etc.

By the way, this type of polycarbonate core optical fiber, like many other plastic optical fibers, generally has a core material and a sheath material layer, or these and a covering layer (protective layer).
is used as a basic structural unit, and after extruding each component of the basic structural unit by a composite spinning method, it is manufactured by cooling and shaping.

However, when optical fibers made of such a core material or polycarbonate resin are manufactured by conventional methods, the disadvantage is that the optical transmission loss is relatively large, so it is desired to develop a method to reduce the optical transmission loss. ing.

For example, according to JP-A No. 6+-6604, a plastic optical fiber with excellent mechanical properties, especially tensile strength, can be obtained by using a polycarbonate resin with an intrinsic viscosity [η] of 0.5 as a core material. However, the plastic optical fiber has an optical transmission loss of 990 dB/km at an optical wavelength of 770 nm, which is a problem in that the optical transmission loss is not sufficiently small.

In addition, as a manufacturing method for this type of polycarbonate core optical fiber, the optical fiber material (coating material consisting of the core material, sheath material layer, and coating layer) obtained by the above-mentioned composite spinning etc. is subjected to an annealing treatment. A method has been proposed (see Japanese Unexamined Patent Publication No. 32004/1983).

However, the manufacturing method described in Japanese Patent Application Laid-open No. 60-32004 has the following problems because the conditions for annealing treatment are not appropriate as will be described later.

In other words, ■The above publication states that ``It is preferable to anneal at a temperature higher than the glass transition temperature (T, )'', and that if the optical fiber material is annealed at a temperature higher than T1, the optical fiber material will change. There is a problem with deformation.

ε However, in the examples of the publication, 10
An example is shown in which heat treatment is performed at 0 to 140°C for 3 hours. Under such annealing treatment conditions, the optical transmission loss of the resulting optical fiber material is also large (for example,
The decrease in optical transmission loss is as small as about 0.02 dB/-. )
There are some problems such as.

■Furthermore, in the publication, the optical fiber material subjected to the above annealing treatment consists of three layers: core material/sheath material layer/covering layer (protective layer).
When the layered structure is manufactured by a composite spinning method, there is a problem that the layered structure becomes complicated and the manufacturing process also becomes complicated.

The present invention has been made in view of the above circumstances.

An object of the present invention is to provide an optical fiber having a core material made of a polycarbonate resin, and a sheath material layer made of a plastic having a refractive index lower than that of the core material, with a refractive index of at least 2N or more, which achieves the various advantages of the polycarbonate resin. A method for producing polycarbonate core-based plastic optical fibers, which is extremely advantageous in practice and allows easy and stable production of high-performance optical fibers with sufficiently reduced optical transmission loss while making full use of their properties. Our goal is to provide the following.

[Means for Solving the Problems] The present invention for solving the above problems provides an optical fiber material having a core material made of a polycarbonate resin and a sheath material layer made of a plastic having a refractive index lower than that of the core material. , a method for producing a plastic optical fiber, which is characterized by performing an annealing treatment at 60 to 100°C for 5 minutes to 72 hours, and then slowly cooling at a cooling rate of 1°C/min or less.

A preferred example of the plastic optical fiber manufactured by the method of the present invention is composed of at least a core material made of a polycarbonate resin and a sheath material layer made of a plastic having a refractive index lower than that of the core material. For example.

As shown in FIG. 1, a core material 2 and a sheath material layer 3 which is its outer layer
Alternatively, as shown in FIG. 2, for example, a cover layer 4 as a protective layer is further provided on the outer layer of the sheath material layer 3 as required.

Hereinafter, the core material, sheath material layer, and coating layer will be explained in detail in this order, and further, the manufacturing method will be explained in detail.

, It The core material is made of a polycarbonate resin, and as the polycarbonate resin, one type, or two or more types can be selected and used from various types of polycarbonate resins, such as those known in the art. .

Specific examples of the polycarbonate-based resin include various types, preferably alicyclic polycarbonates represented by the following general formula (%), in which R is represented by Examples include aromatic polycarbonates represented by:

Furthermore, copolymers of these and dihydroxy compounds such as 4,4'-dihydroxydiphenyl ether, ethylene glycol, P-phenylene glycol, and 1,6-hexanediol may 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; for example, the phosgene method involves the reaction of dihydric phenols with phosgene, or the reaction of dihydric phenols with carbonate esters such as diphenyl carbonate. A transesterification method, a method of reacting a dihydric phenol with a hexafluoromate 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 hydroxyphenyl)sulfitobis(hydroxyphenyl)sulfone, and substituted products thereof such as lower alkyl and halogen.

``Among these dihydric phenols, for example, 2.
2-bis(4-hydroxyphenyl)propane [hereinafter referred to as
It is sometimes called bisphenol A. ], ]1,1-bis4-hydroxyphenyl)ethane, 2,2-bis(4
-Hydroxyphenyl)-hexafluoropropane-
Somehow desirable.

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 among the above, and generally has a viscosity average molecular weight of za, non to 2.
g, (1 (preferably within the range of 10, especially,
Preferably, it is within the range of 20,500 to 27,000.

The polycarbonate resin used for the core material has a viscosity average molecular weight of, for example, 20.000 to 28.000.
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, and
Improvements in optical properties such as transparency, refractive index, and light transmission properties 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) [M w / M n
(GPC method)] or 5 is usually within the range of 2.0 to 2.5, preferably within the range of 2.0 to 2.4, and particularly preferably within the range of 2.0 to 2.4. The polycarbonate resin is obtained by treating the polymer obtained during production with a solvent such as acetone to remove the low molecular weight component [M w ; 3,000
It is preferable to remove the following].

Further, it is preferable that the polycarbonate resin has been sufficiently desalinated, for example, it is preferable that the content of heroganized hydrocarbon is 15 ppm or less.

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, 5 x 10' μm2/g or less to 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, but in the case of 1-bisphenol A polycarbonate,
Usually the value is around 1,586.

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

1 and 1 The sheath material layer is made of plastic having a smaller refractive index than the core material. Specifically, the refractive index is 1 higher than that of the core material.
A plastic having a refractive index that is usually at least 0.01 lower, preferably at least 0.02 lower (hereinafter sometimes referred to as resin (A)). ] Consists of.

If the refractive index of the plastic used as the sheath material layer is higher than the refractive index of the core material, the optical transmission loss will increase and the performance of the plastic optical fiber cannot be ensured.

There are no particular restrictions on the type of resin (A) constituting the sheath material layer, and in JL terms, for example, polymethyl methacrylate, poly-4-methylpentene-1, boa arylate, alicyclic polycarbonate, Aromatic polycarbonate, silicone resin, silicone acrylate resin, urethane acrylate resin, fluorine-containing polymethyl methacrylate, vinylidene fluoride polymer, difluoride-hexafluorobrobylene copolymer, styrene-methyl methaxolate copolymer Examples include Copolymer 1 ethylene-vinyl acetate copolymer, methyl methacrylate/styrene, vinyltoluene or α-methylstyrene/maleic anhydride ternary or quaternary copolymer.

These polymers are used to improve delamination strength.
For example, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and itacone #, unsaturated glycidyl monomers such as dicrycidyl acrylate or methacrylate, β-methylcrisicyl acrylate or methacrylate,
A parent polymer such as acrylamide, methacrylamide, derivatives thereof, hydroxyalkyl acrylate, or methacrylate may be copolymerized.

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@2.2
．． 2-trifluoroethyl, methacrylic acid 2,2.・
3.3-tetrafluoropropyl, methacrylic acid 2,
2,3,3,3-pentafluoropropyl and the like may be mentioned.

By using one or more of these fluorine-containing methacrylic esters, a copolymer consisting of a vinyl monomer that can be copolymerized with the fluorine-containing methacrylic ester and a vinyl monomer that can form a hydrophilic homopolymerization ring is prepared. You can also use it.

Among these resins, a resin having a refractive index smaller than that of the core material can be employed as the resin (A).

The plastic optical fiber manufactured by the method of the present invention may further have a covering layer (protective layer) as an outer layer of the sheath material layer, if necessary.

The protective layer is made of a resin (hereinafter sometimes referred to as resin (B)) having a heat resistance equal to or higher than the heat deformation temperature of the core material and the sheath material layer. ] is preferably formed.

Since the heat deformation temperature of the resin (B) is higher than the heat deformation temperature of the sheath material layer, the heat resistance of the plastic optical fiber can be improved.

Examples of the resin (B) include polyester, polyamide, poly-4-methylpentene-1, polyvinylidene fluoride, polyacetal, polysulfone, polytetramethylene terephthalate, polyethylene terephthalate, polypropylene, polyoxymethylene, polybutene, ABS resin, So-called engineered plastics such as polyphenylene oxide, bocarbonate, and crosslinked polyolefin may be mentioned. It is also possible to use polycarbonate resin used as a core material.

Further, in order to improve the durability of the plastic optical fiber, the resin (B) may contain a filler such as carbon flak, talc, silica, glass fiber, carbon fiber, or polyamide fiber.

In the method for producing a plastic optical fiber of the present invention, an optical fiber material (e.g. ,
A bare optical fiber having a structure equivalent to that shown in FIG. 1 or an optical fiber coating material having a structure equivalent to that shown in FIG. After performing the anilization treatment for ~72 hours, it is gradually cooled at a cooling rate of 1° C./min or less.

Here, the optical fiber material to be subjected to the annealing treatment uses at least the polycarbonate resin as a core material or its main component, and the resin (A) as a sheath material layer or its main component to improve the refractive index of the sheath material layer. If the core material is formed to be lower than that of the core material, a newly manufactured optical fiber material may be used, or a separately manufactured optical fiber material (for example, a commercially available product).
However, in this specification, the optical fiber material is intentionally referred to as an optical fiber material instead of an optical fiber.
This is to distinguish it from the plastic optical fiber produced by the method of the present invention, and therefore, this optical fiber material is a conventional plastic optical fiber (such as bare optical fiber, optical fiber coating material, etc.) if it is composed of the above-mentioned components. That's fine.

In the method of the present invention, there is no particular restriction on the steps up to the manufacturing stage of the optical fiber material, and the optical fiber material can be manufactured by various methods such as the known composite spinning method, and by any method. It may also be something you have.

The optical fiber material can be suitably manufactured, for example, as follows. That is, using a composite spinning machine 5 as shown in FIG. 3, the predetermined polycarbonate resin is supplied to the melt extruder 6a as a raw material for the core material, and the predetermined resin (A) is supplied as a raw material for the sheath material layer. The polycarbonate resin is supplied to a melt extrusion ASB, and the polycarbonate resin is coated with the resin (A) through the nozzle 7 for composite spinning.

The obtained fiber (optical fiber material) may be suitably cooled and solidified as it is, and then subjected to the annealing treatment.1 Usually, the composite spun fiber is spun at a distance from the nozzle 7 to the take-up machine 8 (air It is preferable that the material be cooled by passing through a gap 9), thereby being solidified and then taken off by a take-off machine 8 and made into an optical fiber material.

Here, the temperature of the nozzle may be appropriately selected depending on the type and characteristics of the polymer to be used, such as polycarbonate resin, and there is no particular restriction.
Within the range of 5-280°C, preferably 240-270'
It is preferable to set it within the range of C and perform composite spinning.

In addition, the air gap is set to 700 to 1,300 mm.
It is preferable to perform composite spinning while cooling.

Extrude by keeping the nozzle temperature within the range of 235-280℃, and the air gap is 700-1,300mm.
By doing so, it is possible to reduce fluctuations in roundness and outside diameter, and more effectively and stably ensure reduction in optical transmission loss of the obtained optical fiber material.

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 nozzle and the take-off machine.

The polycarbonate resin supplied to the melt extruder 6a is preferably a granular material (unmelted) containing 90% by weight or more of granular material having a particle size of 500 to 2,000 .mu.m.

The bulk density of the polycarbonate resin granules to be supplied is preferably 0.6 to 0.8 g/cm', or preferably the bulk density of the polycarbonate resin granules is 0.6 to 0.8 g/cm'.
If it is 0.8 g/cm'', it is possible to feed the extruder in the same manner as a general pellet-shaped resin, and the resin can be extruded stably.

The structure of the optical fiber material manufactured in this way may be selected as appropriate depending on the purpose of use, etc., but normally, for example, the outer diameter is about 400 to 1,000 pm, the thickness of the sheath material layer is about 1,000 pm, etc. It is appropriate that the thickness be approximately 50 μm.

Further, if desired, a coating layer (protective layer) of an appropriate thickness may be further formed on the sheath material layer to form an optical fiber material (covering coating material) having a protective layer.

One of the important points in the method of the present invention is that the optical fiber material thus produced is subjected to an annealing treatment under the above-mentioned specific conditions.

The conditions for the annealing treatment are a temperature of 60 to 100°C.
Preferably, the temperature is 80 to 100°C, and the time for maintaining the temperature is 5 minutes to 72 hours, preferably 1 to 20 hours.

When the temperature in the annealing treatment is less than 60°C,
The effect of reducing the optical transmission loss of the optical fiber cannot be obtained. On the other hand, if the annealing temperature is higher than 100°C, the effect of reducing the optical transmission loss is small. In either case, the object of the present invention cannot be achieved. do not have.

Furthermore, if the processing time of the annealing treatment at 60 to 100° C. is less than 5 minutes, the effect of reducing optical transmission loss will not be sufficiently obtained; on the other hand, if the processing time exceeds 72 hours, In some cases, the effect of reducing optical transmission loss may be obtained, but in some cases, the optical transmission loss may even increase, and in either case, the object of the present invention cannot be achieved.

In the method of the present invention, it is important to slowly cool the optical fiber material thus annealed under specific conditions at a temperature of 1"C7 minutes or less, preferably 4 to 7 degrees Celsius.

If this cooling is performed at a cooling rate faster than 1° C./min, the effect of reducing optical transmission loss cannot be obtained, and the object of the present invention cannot be achieved.

Such annealing treatment and cooling treatment can be carried out using various types of equipment and equipment as long as they have an appropriate temperature control mechanism, and there are no particular restrictions on the heating method or cooling method. This annealing treatment and cooling treatment, which can be applied using equipment and equipment as is or with appropriate modifications, can be performed in various ways such as continuous, semi-continuous, and discontinuous, improving productivity and From the viewpoint of operability, etc., it is preferable to carry out the process in a continuous manner.

Note that, as described above, the annealing treatment and the cooling treatment can also be performed continuously following the composite spinning, before the optical fiber material is taken up by the take-off machine during the composite spinning.

Furthermore, as described above, the annealing treatment may be performed on an optical fiber material (optical fiber bare wire material) that does not have a coating layer (protective layer), or on an optical fiber material (optical fiber coated cord) that has a coating layer (protective layer). materials, etc.)
If necessary, annealing and cooling treatments may be performed on the bare optical fiber.

A coating layer (protective layer) is applied to the obtained optical fiber as appropriate.
You may also set up and use it.

As described above, in the method of the present invention, the manufacturing process of an optical fiber material by composite spinning etc. and its annealing treatment and cooling treatment process can be made continuous or separated as appropriate, or a covering layer (protective layer) can be formed in composite spinning. Various production methods can be adopted as needed, such as forming a protective layer at the same time or forming a covering layer (protective layer) after annealing and cooling.
improvement) can be carried out efficiently.

In the manner described above, a high-performance plastic optical fiber with sufficiently reduced optical transmission loss can be manufactured easily, stably, and at low cost.

The polycarbonate core-based plastic optical fiber manufactured by the method of the present invention, which combines the specific annealing treatment and cooling treatment, is lightweight and inexpensive, and has high heat resistance and bending strength based on the polycarbonate resin. , thermal and mechanical properties such as thermal shock resistance, and optical properties such as high transparency and refractive index. Moreover, this plastic optical fiber
In particular, optical transmission loss is sufficiently reduced compared to conventional polycanibonate core-based optical fibers. Therefore, the plastic optical fiber of the present invention can be suitably used as an optical fiber for industrial, medical, decorative, or information transmission purposes in various fields, particularly in the automobile field, home appliance field, etc.

[Examples] Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these Examples, and various modifications can be made within the scope of the gist of the present invention. and applications are possible.

(Examples 1 to 6) Polycarbonate resin having repeating units derived from bisphenol A was used as the polymer for the core material, and 80% by weight of methyl methacrylate was used as the polymer for the sheath material layer.
Using a copolymer obtained by copolymerizing and 20% by weight of isobornyl methacrylate, these polymers were simultaneously extruded using a screw melt extruder set at 270°C and 230°C, respectively, and having a nozzle diameter of 31φ. It was supplied to the spinning head of a composite spinning machine and extruded from the spinneret. This extruded fiber is cooled and solidified, and taken off by a take-off machine at a speed of 20-1 minutes.
gm, and a bare optical fiber having a sheath material layer thickness of 10 μm was obtained.

After measuring the optical transmission loss of this optical fiber material by the cut back method using a light source with a wavelength of 660 rv, it was placed in a 20 m oven and annealed at the annealing temperature shown in Table 1 for the time shown in Table 1. Thereafter, the sample was cooled to room temperature by cooling at the cooling rate shown in Table 1 to obtain a desired optical fiber sample. The optical transmission loss of this optical fiber was measured in the same manner as described above.

The results are shown in Table 1.

(Comparative Examples 1 to 8) The same procedure as in Example 1 was conducted except that the annealing conditions and cooling rate were set to the values shown in Table 1.

The results are shown in Table 1.

[Effects of the Invention] According to the present invention, it is possible to easily and stably produce a high-performance optical fiber with sufficiently reduced optical transmission loss without deteriorating various excellent properties of polycarbonate resin. An object of the present invention is to provide a method for manufacturing a polycarbonate core-based plastic optical fiber, which is extremely advantageous in practice.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory cross-sectional views showing an example of the plastic optical fiber of the present invention. FIG. 3 is an explanatory diagram showing an example of an apparatus used in the manufacturing method of the present invention. l... Plastic optical fiber 2... Core material, 3... Sheath material layer, 4... Protective layer, 5... Composite spinning machine 6a, 6b... Melt extruder, 7... Nozzle 8...
・Collection machine, 9...Air gap. Figure 2 Figure 3

Claims (1)

[Claims] (1) An optical fiber material having a core material made of a polycarbonate resin and a sheath material layer made of a plastic having a lower refractive index than the core material is annealed at 60 to 100°C for 5 minutes to 72 hours. , followed by slow cooling at a cooling rate of 1° C./min or less.