JPH03116104A - Plastic optical transmission fiber and production thereof - Google Patents

Abstract

PURPOSE:To render a continuous refractive index gradient to a core material and to reduce the loss of the quantity of light (transmission loss) by combining the core material made of a single resin with a sheath material made of a resin having a lower refractive index than the core material by >=0.1% and specifying the refractive index of the peripheral part of the core material. CONSTITUTION:A core material made of a practically single resin is combined with a sheath material made of a resin having a lower refractive index than the core material by >=0.1% and the refractive index of the peripheral part of the core material is made gradually lower than that of the central part by >=0.001, preferably >=0.002. Any polymer having a higher refractive index than the sheath material by >=0.01 and superior transparency may be used as the resin of the core material. A useful plastic optical transmission fiber having a refractive index gradient from the central part of the core material toward the peripheral part and causing a small loss of the quantity of light (transmission loss) is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a plastic light transmitting fiber and a method for manufacturing the same. More specifically, the present invention relates to a plastic light transmitting fiber with little diameter variation and low light transmission loss, which can be suitably used as an optical communication means, and a method for producing such an excellent plastic light transmitting fiber.

[Problem to be solved by the prior art and the invention 1] In recent years, fibers for optical transmission have become more resistant to bending stress, easier to handle, and cheaper than the inorganic glass optical fibers that have been widely used. Plastic light transmitting fibers have been developed and put into practical use.

This plastic optical fiber has a core material layer made of a polymer with excellent light transmittance, and a sheath material layer made of a polymer with a lower refractive index than the core material layer and excellent transparency. It is generally composed of two materials, and is manufactured by coextruding both materials into a two-layered fiber using a composite spinning device.

Due to their structure, optical transmission fibers can be classified into clad type (step index type) and focused type (graded index type).
It is classified into The clad type is a simple core-sheath type and is the most common optical transmission type that has been put into practical use! A fiber, the incident light is transmitted through repeated total reflection at the core-sheath interface, resulting in a large light quantity (transmission) loss.On the other hand, the focusing type has a continuous refractive index gradient from the center of the core material to the periphery. Because of this, the light travels smoothly without being totally reflected, resulting in less light loss (transmission) compared to the clad type.

Various studies have been conducted on focusing plastic light transmitting fibers. For example, monomer A for high refractive index resin and 7-summer for low-refractive-index resin, which has a higher copolymerization reactivity ratio than the above-mentioned 7-summer A. Select B and perform light irradiation polymerization in a cylindrical container to create a rod with a refractive index gradient.
A method of hot stretching 100 to 300 times has been proposed.

However, the fibers obtained by this method are difficult to form a uniform, convergent structure, and it is difficult to reduce light intensity (transmission) loss, so it has not yet been put to practical use.
1-43388 discloses that a monomer is diffused from the surface of a linear molded object such as a polycarbonate resin so as to create a continuous refractive index gradient from the center to the periphery of the linear molded object, A method of polymerizing by irradiating radiation, or Japanese Patent Publication No. 52-40987 discloses composite fibers made of a core material such as a polycarbonate resin and a glass material made of a copolymer of a vinyl monomer and styrene having a curable group. A method is disclosed in which, after curing the glass material, the core material is impregnated with 7-mer, which is a raw material for forming a resin with a refractive index lower than that of the core material, and then polymerized. However, all of these methods require complicated steps such as impregnating and diffusing the monomer into the core material, and there is also the problem that the fiber material is dissolved by the 7-layer and the cross section is not perfectly circular. Since the loss of light intensity (transmission) of the fibers also does not show any significant decrease, it is difficult to put it into practical use.

Another problem with plastic light transmitting fibers is how to suppress the variation in diameter between the core material layer and the sheath material layer during composite spinning in such a manufacturing method.

As a technology with such ingenuity,
The s2os publication describes a plastic-based optical transmitter that uses a core material layer, a sheath material layer, and a protective layer as basic structural units, and that is shaped by extruding each layer component of the basic structural units using a composite spinning method and then cooling. wherein the protective layer is formed of a polymer having a glass transition temperature higher than that of the polymer constituting the core material layer, and the cooling is performed to increase the glass transition temperature of the protective layer polymer and the core material. In the temperature range including the glass transition temperature of the layer polymer, it is 10 to 10. A plastic light transmitting fiber is disclosed which is characterized by cooling at a cooling rate of OOQ'C/see. In the publication, blowing of gas such as air, nitrogen gas, argon gas, carbon dioxide gas, etc. is disclosed as a preferable cooling means, and as a specific cooling means,
．． An air flow of 5 m/sec is disclosed.

Further, Japanese Patent Application Laid-Open No. 83-303304 proposes a technique for heating and stretching plastic fibers under certain conditions. This publication also states that the cooling air speed is 0.4
A spinning method with cooling at m/see is disclosed.

However, in plastic optical fibers,
It is known that forced cooling by air current or the like at the exit of a spinneret of a composite spinning machine tends to cause fluctuations in fiber diameter and circularity, making it difficult to obtain optically transmitting fibers of uniform quality and excellent quality. Such fluctuations in fiber diameter and roundness caused by air currents can be avoided even when forced cooling is not used or when ordinary air cooling is used, as air currents are generated around the running fibers. The diameter variations and roundness variations still cannot be eliminated.

One purpose of this invention is to solve the above-mentioned problems and to provide a continuous refractive index gradient to the core material without going through complicated processes such as impregnating and diffusing the light quantity (transmission). )
An object of the present invention is to provide a plastic light transmitting fiber with low loss.

Another object of this invention is to produce
Equipped with a continuous refractive index gradient in the core material, with little diameter variation.
Another object of the present invention is to provide a method for producing the plastic light transmitting fiber having excellent roundness.

[Means for Achieving the Object] The present invention for solving the above problem provides a core material made of substantially a single resin, and a sheath material made of a resin having a refractive index lower than that of the core material by 0.1% or more. A plastic optically transmitting fiber characterized in that the peripheral part of the core material has a refractive index gradient that is 0.001 or more lower than the refractive index in the central part; A core material made of a single resin and a sheath material made of a resin whose refractive index is 0.1% or more lower than that of the core material are spun into a cooled guide tube with virtually no airflow using a composite spinning method. This is a method for producing billable fibers, which is characterized by coextruding from a die, cooling, and then cooling in an air cooling zone.

Next, the plastic light transmitting fiber of the present invention and the manufacturing method of the present invention will be explained in detail.

-Plastic light transmitting fiber- The plastic light transmitting fiber of the present invention has a core material layer made of a substantially single plastic with excellent light transmittance, and a refractive index smaller than that of the core material layer, and a sheath material layer made of highly transparent plastic.

Alternatively, a plastic light-transmitting fiber may be formed by further laminating a protective layer on the outer surface of the sheath material layer.

The plastic used as the core material layer has a refractive index that is 0.0 lower than the refractive index of the sheath material layer! larger than,
Any polymer that has excellent transparency may be used.

Further, in the present invention, the refractive index of the peripheral part of the core material layer is 0.001 or more, preferably 0.01 or more, than the refractive index of the central part.
It is important to have a refractive index gradient that is lower than 0.02. This is because the presence of this refractive index gradient allows the light transmitting fiber to function with less loss in light amount (transmission).

This refractive index gradient of the core material layer can be easily formed by the spinning method (manufacturing method) of the present invention, which will be described later, without using any specific monomer after forming the fiber.

Specific examples of such plastics for use as core materials include methacrylic polymers, polycarbonates, polystyrene, styrene-methacrylate copolymers, polyolefins, or plastics in which all or some of the hydrogen atoms of these polymers are replaced with deuterium atoms. Examples include 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 can also be used as the core material for the shoe.

As the plastic for the core material, methacrylic polymers and polycarbonates are preferred, with polycarbonate being particularly preferred.

The methacrylic polymer is, for example, a homopolymer or copolymer of methyl methacrylate (70% by weight or more of the starting monomer is preferably methyl methacrylate and 30% by weight or less is another monomer copolymerizable with methyl methacrylate). Examples of monomers that can be copolymerized with methyl methacrylate include vinyl monomers such as methyl acrylate and ethyl acrylate.

Examples include copolymers of methacrylic acid esters such as cyclohexyl methacrylate, t-butyl methacrylate, impolnyl methacrylate, adamantyl methacrylate, benzyl methacrylate, phenyl methacrylate, and naphthyl methacrylate and monomers copolymerizable with these. It will be done.
Among these, methyl methacrylate homopolymers and copolymers are preferred.

Suitable polycarbonates include, for example, where the R is ／　　＼ CH3 CH3 Alicyclic polycarbonate, indicated by CH3 6 5 6 H11 I can do that.

In addition, these and 4.4°-dioxydiphenyl ether, ethylene glycol, p-xylylene glycol, 1
．． Copolymers with dioxy compounds such as 8-hexanediol can also be used.

From the viewpoint of heat resistance etc., the heat distortion temperature (ASTMD-
848, load 4.8 kg/cm2) is preferably 120°C or higher. More specifically, an aromatic polycarbonate having a repeating unit represented by the following is particularly preferred.

The polymer used as the sheath material layer has a refractive index of 0.0. Specific examples of such polymers for the sheath material layer include polymethyl methacrylate, styrene-methyl methacrylate copolymer, poly 4-methylpentene-1, which is not particularly limited as long as it is smaller than O1 and is transparent. , ethylene-vinyl acetate copolymer, polycarbonate, fluorine-containing polymethyl methacrylate, vinylidene fluoride-hexafluoropropylene copolymer, hnylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer,
Examples include methyl methacrylate-styrene, vinyltoluene, and α-methylstyrene/maleic anhydride terpolymer or quaternary copolymer. Among them, vinylidene fluoride-fluoroolefin copolymer, poly-
4-Methylpentene-1 and polycarbonate having a structure represented by the following general formula are particularly preferred in terms of low light transmission loss.

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

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

The polycarbonate represented by the formula CI) suitable for the sheath material layer may be a block copolymer of the two types of repeating units in the formula (I) or a random copolymer, which is preferred. is a random copolymer.

Furthermore, in the formula (I), (a/a+b)×100
It is desirable that the value is 20 or more; if this value is less than 20, optical transmission loss may increase. In addition,
b may be O, and the polycarbonate represented by the formula (I) usually has a glass transition temperature (Tg) of 157° C. or higher and a refractive index of 1.57 or lower.

In the method for producing a plastic light transmitting fiber of the present invention, the plastic constituting the sheath material layer and the plastic constituting the core material layer are brought into a molten state, and the composite spinning method is used to cool the plastic fibers substantially without airflow. It is important to co-extrude the material from the spinneret into a cooled guide tube, cool it, and then cool it in an air cooling zone.

Next, the method for manufacturing the optically transmitting am of the present invention will be explained in detail together with the apparatus.

1. Manufacturing device 1. The manufacturing device used in the manufacturing method of the present invention includes a hollow cooling type guide tube airtightly connected to the outlet of a spinneret of a composite spinning machine, and an air-cooled spinning zone connected thereto.

The cooling type guide cylinder is formed by a cooling cylinder having openings at both ends. This cooling tube may have a structure that includes a flow path through which a cooling medium can flow, and a cooling chamber nri that can cool the plastic light transmitting fiber extruded from the spinneret in a substantially windless state. There are no particular restrictions.

Here, "substantially no wind" means that no gas is blown into the cooling space.

As long as the wall surface forming the internal space of the cooling tube is made of a material with good thermal conductivity, such as metal, there are no particular restrictions on the material and shape of the cooling tube. It is preferable that the spinneret for extruding the fibers be closely attached to the spinneret through a heat insulating material.

Note that the cooling type guide tube is not limited to one that is attached directly to the spinneret, but may be attached to the spinneret attachment part as long as it surrounds or surrounds the spinning nozzle.
This is because if there is a gap between the heat insulating material and the cooling type guide tube, air can enter and leave the gap, creating an airflow in the space through which the fibers pass, making it impossible to maintain an airless state.

The air-cooled spinning zone is a device that is installed directly under the cooling guide tube, and further cools the fibers cooled in the cooling guide tube in a windless state using an air flow. The air-cooled spinning zone is provided with an air inlet on the outside of its lower part, and is also provided with air outlets arranged in series along the fibers and blows air toward the fibers, and these outlets blow air in one direction. It is possible to arbitrarily select a cross-blowing type in which air is flowed through the air, a cylindrical type in which air is flowed around the traveling am in the diametrical direction of the m-shape and toward the fibers, and various other types of air cooling. A cylindrical configuration in which air flows on average from around the fibers is the most preferred embodiment of the air-cooled spinning zone.

The air-cooled spinning zone cools the fibers by airflow, preferably at a wind speed of 0.5 to 100 am/sec, at 100C.
If the wind speed is higher than 2/sec, the yarn may swing so much that it may become difficult to spin the yarn.

When using a preferable cylindrical air-cooled spinning belt, it is preferable to attach the air-cooled cylinder to the cooling guide cylinder so that there is no gap.

There are no particular restrictions on the material forming the air-cooled spinning zone.

All materials such as metal, plastic, and ceramics can be arbitrarily selected. The length is also not particularly limited, but is preferably at least 500+us.

1 to 4 show examples of preferred embodiments of the cooling type guide tube and air-cooled spinning zone of the present invention.

The cooling type guide tube shown in FIGS. 1 and 2 is of a double cylindrical type (Liebig cooler type), and is formed of a cylindrical inner wall and an outer wall, through which a cooling medium such as cooling water flows. A cooling medium population 3 is formed below the outer wall, and a cooling medium outlet 4 is formed above the outer wall.

The upper end opening of this cooling type guide cylinder is connected to the spinneret 5 through a heat insulating material 6 in an airtight and heat-insulated manner.

Further, FIG. 1 shows an example of a side-blown air-cooled spinning belt 7a, and FIG. 2 shows an example of a double-cylindrical air-cooled spinning tube 8a. Both are directly connected to the cooling guide tube and have an air inlet 8 and a plurality of airflow outlets for the airflow toward the running fibers. FIG. 2(A) shows a cross-sectional view of the cylindrical air-cooled spinning zone 8a. In this cylindrical air-cooled spinning zone 8a, airflow flows in the diametrical direction from the inner wall of the cylindrical air-cooled spinning zone 8a toward the fibers running at the axis of the cylindrical air-cooled spinning zone 8a.

The cooled guide tube shown in FIGS. 3 and 4 is of a pipe type. That is, as shown in the figure, it has a structure in which a pipe is spirally wound without any gaps, and the internal space l of this coil, which is formed into a cylindrical shape by spirally winding the pipe, is the light transmitting edge @2. A cooling medium 3 is provided below the coil, and a cooling medium outlet 4 is provided above the coil. In this cooling type guide cylinder as well, the spinneret 5 and the cooling type guide cylinder formed in a coil shape from a pipe are connected through a heat insulating material 6 in an airtight and heat insulating state.

In addition, in any of the cooling type guide tubes shown in FIGS. 1 to 4, the cooling medium may be either liquid or gas, and from the viewpoint of economy and ease of handling, water or cooling medium may be used. Air is preferable.

Moreover, a heat pump method can also be used as a cooling method.

The temperature of the space within the cooling guide cylinder is appropriately determined depending on the type of spinning resin, spinning speed, etc. If the guide cylinder is not cooled at this point, the temperature will rise and the tensile tension of the spun fibers will decrease, resulting in large yarn sway, making it impossible to obtain the excellent plastic light-transmitting fiber that is the object of the present invention.

The length of the cooling guide cylinder can be arbitrarily selected according to the manufacturing conditions of the plastic light transmitting fiber, and is not particularly limited. Usually, it is 5 to 150 c+w. Conventional cooling methods can optionally be used for further cooling after cooling under no airflow conditions. i.e. forced cooling with air or water,
Alternatively, air cooling and water cooling may be combined.

1. Manufacturing method 1. The plastic optically transmitting fiber of the present invention is produced by composite spinning in which the plastic constituting the sheath material layer and the plastic constituting the core material layer are melted and discharged from a spinneret using a special die. Do it by method.

What is important in the method of the present invention is that the plastic for the core material Namerikawa and the plastic for the sheath material layer are coextruded from a spinneret into a cooling guide cylinder with substantially no airflow by a composite spinning method. It is.

Here, the cooling guide cylinder and the air-cooled spinning zone are as described above.

The length of the cooling guide cylinder, that is, the effective length of the spun plastic light transmitting fiber while being cooled, is determined by using polycarbonate as the core material Namekawa plastic and poly(4-methylpentene) as the sheath material layer plastic. -1 is adopted, the diameter of the nozzle is 3mm,
%5~ when the nozzle temperature is 240~280℃
It is good to have a 100c layer, preferably a 10 to Hc layer.

When the plastic light transmitting fiber spun using the cooling guide cylinder and air-cooled spinning belt of the present invention is forcibly cooled,
Since temperature rise is effectively prevented within the cooling guide cylinder, there is no decrease in the tensile strength of the plastic light transmitting fiber (tension between the nozzle and the take-up roll), there is no yarn shaking, and there is no change in diameter. Very few plastic light transmitting fibers are produced.

The Plasti-2 optically transmitting fiber produced in this way has a core layer that has a continuous refractive index gradient from the center to the periphery, and the refractive index of the periphery is higher than that of the center. Also 0.
001 or more, which leads to the expression of the function of a focusing type light transmitting fiber.

There have been no reports to date of this plastic optically transmitting fiber, which is essentially made of a single resin and whose core material has a gradient of refractive index using only the extrusion composite spinning method.
This was discovered for the first time by the present inventors.

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

(Example 1) Commercially available polycarbonate (manufactured by Idemitsu Petrochemical Co., Ltd., refractive index: 1.585, Tg: 1) as core material Namegawa polymer
48°C, viscosity average molecular weight (M); 22,000)
In addition, poly-4-methylpentene-1 (manufactured by Mitsui Petrochemicals, product number TPX-MXO) was used as a polymer for the sheath material layer.
O4, refractive index, 1.463, T g , 240
°C) from the spinneret (nozzle diameter: 3 mmφ) of a composite spinning machine into a cooling guide cylinder that is airtightly connected to the spinneret and cooled by passing cooling water into the cooling guide cylinder, which maintains the inside of the cylinder in a substantially windless state. Co-extruded, taken off at a speed of 20 m/min, and further cooled in an air-cooled spinning zone, the diameter of the core material layer was 9801 mm.
A plastic light transmitting fiber with a sheath material layer thickness of 10 JLm was obtained.

Here, the cooling type guide tube is of a double cylindrical type (the system shown in Fig. 2) with an inner diameter of 75 mm and a length of 450 layers, and the air-cooled spinning belt has an inner diameter of 75 mm and a length of 500 layers. A double cylinder system (the system shown in Figure 2) was used.

Regarding the obtained plastic light transmitting fiber, 660n
The optical transmission loss at m, the diameter variation (%) using a laser outer diameter measuring device, and the refractive index of the core material layer in the radial direction using an interference microscope were measured. The results are shown in Tables 1 and 5.
As shown in the figure.

(Example 2) In Example 1, the temperature of the cooling water in the cooling type guide tube was set to 50
Spinning was carried out in the same manner as in Example 1 except that the temperature was changed to .degree.

The results are shown in Table 1 and Figure 5.

(Example 3) Spinning was carried out in exactly the same manner as in Example 1, except that the air-cooled spinning zone and wind speed were changed.

The results are shown in Table 1 and Figure 5.

(Comparative Example 1) Table 1 and FIG. 5 show the results of spinning in Example 1 without using a cooling guide cylinder or an air-cooled spinning belt.

(Comparative Example 2) Table 1 and FIG. 5 show the results of spinning in Example 1 without using an air-cooled spinning belt.

As is clear from Table 5, the light transmitting fiber produced using the method of the present invention has a refractive index gradient from the center to the periphery of the core layer 10, and the refractive index of the periphery is at the center. o, oo from the department
It is shown that the loss is lower than t, and comparison with Table 1 shows that the light amount (transmission) loss is greatly reduced. In Fig. 5, numeral 11 indicates the glass material layer.Also, as shown in Table 1, when cooling is performed by passing cooling water through the cooling type guide tube (example), the glass material layer is indicated by 11. Compared to the case (Comparative Example 2), it is shown that the diameter variation and optical transmission loss of the obtained optically transmitting fiber are extremely small.

[Effects of the Invention] According to the method of the present invention, plastic light transmitting fibers are produced using a composite spinning machine equipped with a cooling guide tube and an air-cooled spinning zone. Compared to the conventional method that does not use a type guide cylinder or an air-cooled spinning belt, it is possible to obtain an excellent fiber with low transmission loss. Moreover, the focusing type plastic light transmitting am can be manufactured extremely easily without using other monomers as in the conventional method.

In particular, the plastic light-transmitting fiber produced by the method of the present invention has a refractive index gradient from the center of the core material to the periphery, and is an extremely useful plastic light-transmitting m-fiber with little loss of light quantity (transmission).

[Brief explanation of drawings]

FIG. 1 is a sectional view of a double cylindrical cooling guide tube and a cross-blowing air-cooled spinning zone, which are examples of the cooling guide tube and air-cooled spinning zone of the present invention, and FIG. Figure 3 is a cross-sectional view of a pipe-type cooling guide tube and a cross-blowing air-cooled spinning belt, and Figure 4 is a cross-sectional view of a pipe-type cooling guide tube and a double cylinder type air-cooled spinning belt. FIG. 5, which is a cross-sectional view of an air-cooled spinning belt, is a diagram showing the refractive index distribution of the core material of the plastic optically transmitting fiber of the present invention. FIG. 2A is a cross-sectional view of the double cylindrical air-cooled spinning zone of FIG. DESCRIPTION OF SYMBOLS 1...Cooling space of guide tube, 2...Plastic light transmitting fiber, 3...Cooling medium inlet, 4...Cooling medium outlet, 5...
- Spinneret, 6... Insulating material, 7.9... Cooling space of air-cooled spinning zone, 8... Spinning zone air inlet, 11-13... Fibers obtained in Examples 1-3 refractive index of 14-15... refractive index of the fiber of Comparative Example 1.2.

Claims (2)

[Claims] (1) Consisting of a core material made of substantially a single resin and a sheath material made of a resin whose refractive index is 0.1% or more lower than that of the core material,
And the refractive index of the peripheral part of the core material is 0.0 less than the refractive index of the central part.
A plastic light transmitting fiber characterized by having a refractive index gradient as low as 0.01 or more. (2) A core material made of substantially a single resin and a sheath material made of a resin whose refractive index is 0.1% or more lower than that of the core material are coextruded from a composite spinneret, and cooled with substantially no airflow. 2. The method for producing a plastic light transmitting fiber according to claim 1, wherein the plastic light transmitting fiber is cooled by being guided into a guided tube and then into an air cooling zone.