JPS63303304A - Production of plastic optical fiber - Google Patents

Abstract

PURPOSE:To improve bending resistance, light transmittability, etc., and to decrease the fluctuation in fiber diameter by heating and stretching a plastic optical fiber under specific conditions. CONSTITUTION:While the unstretched plastic optical fiber 1 discharged from a composite spinning mouth piece 2 and cooled 3 is destaticized 5, the fiber is guided to a stretching zone 6 at a speed V1m/sec (speed of rollers 4). Heating air flow is then blown from an introducing part 9 oppositely to the traveling direction of the fiber 1 and the fiber is stretched to a prescribed magnification by the pulling force of stretching rollers 10 at a speed V2m/sec on the rear side. The fiber is in succession subjected to destaticizing 5 and to a heat treatment 11 for a fixed length without contact in a similar device 6. The fiber is taken up 12 after sufficient cooling. The conditions of the roller speed are so selected as to satisfy 15A<=2L/(V1+V2)<=15A+16 where the sectional area of the stretched fiber 1 is designated as Amm<2> and the length of the zone 6 is designated as Lm. The more uniform optical fiber 1 is obtd. if -10<=P<=10 (P: the distance cm from the outlet of the heating air flow in the outlet of the zone 6 up to the completion point of the fining by the stretching) is set.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is directed to the development of high-quality plastic optical fibers with excellent mechanical strength, especially bending resistance, translucency, and dimensional stability. Regarding manufacturing methods.

[Prior art] Development of optical fibers that form the core of technology innovation in the field of communication technology I
J1, there are remarkable results based on glass-based optical fiber assemblies, and the use of organic optical fibers is attracting attention in the field of short-distance transmission where cost and 7JO workability are important.

Organic optical fiber, ′? The L-, or Plus Deck optical fiber, has inferior translucency compared to glass-based optical fibers, but it is inexpensive and easy to handle, so it will be widely used for short-distance transmission. It is said that

However, this plastic light Noah'fiber is
Usually, it is manufactured by applying the melt spinning method, which is a general synthetic fiber manufacturing method, or unlike ordinary synthetic fibers, it is made of a polymer that is used, has no crystallinity, and has optical fiber assembly characteristics. The polymer used in the fiber manufacturing process must be extremely pure and completely free from foreign substances and impurities during the fiber manufacturing process. There are technical difficulties in industrial implementation, such as extremely severe manufacturing processes and the adoption of Article 1'-1.

Despite these technical difficulties, in order to improve the mechanical properties of the plastic optical fiber, especially its bending resistance and flexibility, we drew the melt-spun undrawn fibers to form polymer chains in the fiber axis direction. Is it necessary to orient the
In this drawing step, interface irregularities and interface peeling 1 occur between the core component and the sheath component constituting the plastic optical fiber. Therefore, it is extremely important to solve the problems of reducing the transmission loss of plastic optical fibers and reducing the variation in wire diameter.

In order to solve such technical difficulties, conventionally, the plastic optical fibers are stretched using heating rolls, heating plates, etc., which damage the sheath components due to abrasion during the stretching process.
Easy to fall off. As a result, non-contact heating stretching is used instead of contact stretching, which reduces translucency and mechanical strength.
For example, a method is employed in which the fibers are stretched while being indirectly heated in a heated atmosphere such as heated air or nitrogen.

However, in the case of non-contact heating and stretching, it is often difficult to uniformly heat the fibers, and if the fibers are deformed by stretching in an uneven state, interface irregularities will occur, reducing the translucency of the plastic optical fiber, and There is also the problem that the drawing becomes unstable and fluctuations in wire diameter cannot be sufficiently reduced.

[Problems to be Solved by the Invention] An object of the present invention is to provide a high-quality plastic optical fiber that has excellent mechanical strength, particularly bending resistance, translucency, and dimensional stability, and has small wire diameter fluctuations. be. Another object of the present invention is to provide a method for drawing plastic optical fibers that enables uniform drawing without the irregular interface between the core and sheath components, which is a technical problem in the production of plastic optical fibers.

[Means for Solving the Problems] As stated in the claims above, the object of the present invention is to draw plastic optical fibers under the conditions expressed by the following formula when heating and stretching them in a non-contact manner. This can be achieved by stretching in d3.

However, A: Cross-sectional area of the drawn fiber (mm2) Vl: Roller speed for supplying the plastic optical fiber to the heated drawing zone (m7 seconds) V2: Roller speed for drawing out the plastic optical fiber from the heated drawing zone (m7 seconds) 1 -: Length of the heating stretching zone (m) In the non-contact heating stretching of the present invention, the roller speed for supplying the unstretched plastic optical fiber to the heating stretching zone is set to Vl (m7 seconds), and the stretched Plus Book 9 no.
・When the roller speed at which the fiber is pulled out from the heated drawing zone is V2 (m7 seconds), the average speed of the fiber in the heated drawing zone is an arithmetic mean (using V1 + V2 ＞/2 Therefore, the average transit time of the fiber when traveling through a heated drawing zone of length l (m) is T = 21
/ (Vl + V2 >).We carefully investigated the preferred range for the average transit time of the fiber traveling through the heated drawing zone for plastic optical fibers with various wire diameters, and found that the cross-sectional area of the drawn plastic optical fiber was When A (mm2 >), the fourth
The present invention has been achieved based on the discovery that, in the shaded range shown in the figure, a high-quality plastic optical fiber with good light transmittance, bending resistance, and small wire diameter variation can be obtained.

In other words, when 21-<15A Vl +V2, the fiber is not heated enough and undergoes deformation (boot
6 = Due to the high viscosity of the fiber or the high deformation rate per unit length of the fiber,
As a result of increased deformation stress and high-tension stretching, large distortions tend to occur and non-uniform stretching tends to occur. In particular, in general melt spinning, a gear pump is used as a metering means when transporting the melt, so the wire diameter changes due to rotational fluctuations and clearance fluctuations for each gear blade, and the wire diameter when discharged from the spinneret hole. Undrawn plastic optical fibers have wire diameter fluctuations due to melt fractures at the hole introduction part, melt fractures due to stick-slip on the inner wall of the discharge hole, and the like. Therefore, when subjected to the above-described high-tension stretching action, stress is first concentrated in the narrow diameter portion of the unstretched plastic optical fiber. Next, as the stress propagates to the large diameter portion, the wire diameter fluctuations in the drawn plastic optical fiber are amplified, and even though the average wire diameter has become thinner due to drawing, the wire diameter fluctuations that the undrawn plastic optical fiber had are reduced. It can reach several times or more, and in extreme cases, it can reach 10 times or more. The target wire diameter variation is ±2% or less with respect to the center wire diameter. Alternatively, different types of polymers are generally used for the core component polymer and the sheath component polymer that constitute the plastic optical fiber. In particular, since the sheath component polymer is required to have a low refractive index, fluorine-containing polymers are often used, and interfacial irregularities may occur if the polymer is deformed by stretching without sufficient heating. , which reduces the light transmittance of plastic optical fibers. Moreover, only plastic optical fibers with poor legal stability can be obtained.

If the amount is too large, the degree of orientation of the molecular chains due to stretching becomes low, resulting in a fiber with weak mechanical strength such as bending resistance, which is also a problem from the viewpoint of the stretching operation.

In the non-contact heating stretching of the present invention, a heated air stream is applied from around the plastic optical fiber near the exit of the zone (hereinafter referred to as the stretching zone) in which the unstretched plastic optical fiber is heated and stretched, and the heating air is applied in the running direction of the optical fiber. Preferably, the heated air currents are introduced into the stretching zone in a countercurrent manner. By introducing the heating fluid into the drawing zone and applying the heating fluid to the optical fiber, it is possible to fix the point at which thinning of the optical fiber is completed near the heated air outlet at the exit of the drawing zone. be.

In other words, we obtain an optical fiber that has excellent mechanical properties such as bending resistance, is more uniform and highly stretched, has no interfacial irregularities or interfacial peeling of both the core and sheath components, and has excellent translucency with small wire diameter fluctuations. In order to do this, under the non-contact heated stretching conditions, the point at which thinning of the optical fiber is completed by stretching is fixed near the heated air outlet at the exit of the stretching zone. In other words, the end point of the change in the profile of the optical fiber should exist in the shortest possible region, and the heating zone -
- By balancing the drawing force and fiber internal stress just before the transition from the zone to the cooling zone, undrawn plastic optical fibers are transformed into drawn plastic optical fibers with molecular chains oriented in the fiber axis direction and at the same time having a stable fiber structure. It is possible to force it. Next, the plastic optical fiber that has passed through the cooling area is sufficiently cooled in the cooling area and has become a stretched fiber with bending resistance, so it can be handled in the same way as ordinary synthetic fiber in the subsequent process. .

Here, the point at which thinning is completed by stretching is not necessarily a necking portion as seen in polyester fibers. This point will be explained based on FIG. That is, FIG. 2 is a side view showing the point at which the thinning of the plastic optical fiber is completed by drawing, or as shown in the figure, the set fiber diameter (
Dl) undrawn plastic optical fiber point (Pl)
The fiber diameter (D2) is reduced to 103% of the target fiber diameter (D3) of the drawn plastic optical fiber.
) is set as the point (P2) of completion of thinning by stretching by -10=. The reason why it is not 100% is to take into account errors due to variations in wire diameter.

In such a drawing method, the heating temperature, heat supply amount, or cooling rate in the drawing zone and cooling zone vary depending on the running speed of the optical fiber running in the stretching zone, the fiber diameter d3, and the length of the heating zone. -cl, but
As above, satisfies and preferably formula IPI≦1
It is better to set conditions that satisfy the relationship of 0 (cm) and then stretch the film.

1, where P is the distance (cm) from the 71[] hot air outlet at the exit of the stretching zone to the point at which thinning is completed by stretching, and an example of the method for measuring the point at which thinning is completed by stretching is ,
The plastic optical fiber being stretched is simultaneously gripped and cut at the entrance of the heated drawing zone and immediately before the drawing rolls, and quickly removed from the heated drawing zone without causing any substantial tensile shrinkage, and marked at intervals of 1 to 5 cm. There is a method of measuring the fiber diameter change, that is, the thinning film, using a micrometer or the like, and by such a method, the drawing point based on the above definition can be determined. Further, the sign of the value of P can be defined as follows.

In other words, if the position of the heated air outlet at the outlet of the stretching zone is P=O, and the point where thinning by stretching is completed is in the direction of the stretching zone (U, the value of P is a negative (-) value, the thinning by stretching is If the point of completion of conversion is in the direction outward from the exit of the drawing zone, the value of P can be expressed as a plus (+) value, and the value of P can be expressed as -1.
When it is within the range of 0rP≦-1-10, the fiber diameter is small, the fiber diameter is small, the transmission loss due to interface irregularities is small, the mechanical properties such as bending resistance are excellent, and the fibers are of high quality. It is possible to make one plastic optical fiber.

If the P value is less than -10 cm, that is, if the thinning completion point due to stretching is located inside the stretching zone, one loaf of optical fiber with good bending resistance cannot be produced. Also, the P value is +1Qc
If the point at which thinning is completed by drawing is located in a region far away from the exit of the drawing zone, only optical fibers of poor quality with large fluctuations in fiber diameter will be obtained.

In J-3 such non-contact heating stretching, it is desirable to fix the point at which the thinning of the optical fiber is completed near the exit of the stretching zone by blowing a heating fluid into the exit of the stretching zone, and on the other hand, The purpose of this method is to actively discharge the fluid from the vicinity of the drawing zone using, for example, an ejector to stabilize the flow of the heated fluid flowing through the drawing zone. By applying such heating fluid introduction and discharge means, it is possible to constantly renew the heat transfer film on the surface of the optical fiber running in the drawing zone, thereby promoting uniform drawing. A3: From the viewpoint of increasing thermal efficiency and reusing thermal energy, it is generally desirable to circulate the exhaust heating fluid.

In addition, assuming that the glass transition point of the core component polymer constituting the plastic optical fiber is q, and the non-contact heating stretching temperature is O (°C), it is heated non-contactly at a temperature within the range of Tg-10≦θ≦TO+80. Contact stretching is preferred. Here, the reason why θ is set to T 0-10 or more is because under the stretching tension, the glass transition point is generally lower than when measured statically by increasing the height by 10'C/min using DSC etc. This method can be used because even in actual non-contact heating stretching, the wire diameter variation is not so large and the translucency is hardly deteriorated. If it is less than that, the drawing tension will increase, and the wire diameter will fluctuate greatly and the translucency will deteriorate.

On the other hand, at Tg+80 (°C) or higher, the deformation stress is low, resulting in insufficient molecular chain orientation, and the mechanical properties of the durable layer are inferior to those of 1st class.

Next, in order to impart dimensional stability to the drawn optical fiber, non-contact constant length heat treatment is performed as a thermal stabilization treatment at a temperature selected from the non-contact stretching temperature range without elongation d3 or contraction. 1M Riko is preferable.

That is, by selecting the conditions of the non-contact heated drawing method, it is possible to reduce the shrinkage rate of the obtained drawn optical fiber to a considerable extent and improve the dimensional stability -14=. In cases where the drawing speed is high or high-magnification drawing is performed to significantly improve mechanical strength, selecting the non-contact heated drawing conditions alone can sufficiently reduce the shrinkage rate of the drawn optical fiber. , it may be difficult to provide good dimensional stability (=l).

In such cases, or as a dimensional stabilization treatment to obtain an optical fiber with improved dimensional stability, it is preferable to heat-treat the optical fiber after the stretching is completed at a temperature selected from the stretching temperature range of the stretching zone, and in particular, to perform a fixed-length heat treatment. is preferable.

In the heat treatment of optical fibers made of amorphous polymers, unlike the heat treatment of fibers made of crystalline polymers such as ordinary synthetic fibers (heat setting), the fiber axis direction given during the drawing process is It is applied with the intention of maintaining the orientation of the polymer chains as much as possible, equalizing the distortion inside the fiber, and imparting dimensional stability. During the heat treatment for achieving dimensional stability, the optical fiber is passed through a heating zone in which a heating fluid circulates and heat-treated to a fixed length, similar to the non-contact heating and stretching method. The heat treatment may be performed so that the shrinkage rate of the optical fiber after 24 hours of heat treatment under dry heat at the maximum operating temperature of the optical fiber is 2% or less, preferably 1% or less.

The core component polymer constituting the optical fiber of the present invention is not particularly limited, and may include a variety of materials having excellent light transmittance, such as homopolymers or copolymers containing methyl methacrylate as the main component, Polycarbonate 1~
, small lunyl homopolymer or copolymer, styrene)
Homopolymers or copolymers containing maleimide as a main component can be mentioned, and similarly polymers constituting the sheath component include a combination of fluorine-containing methacrylate-1 and vinylidene fluoride with tetrafluoride. A copolymer with T tyrene,
Examples include fluorine-containing olefin copolymers.

In addition, as an example of a combination of these core and sheath-tube polymer components, it is natural that there is a difference in refractive index between the two, but from the point of view of composite spinning, the melting point of both types of combined components is It is desirable that it is possible or close.

An example of the non-contact FJO hot stretching and heat treatment method of the present invention will be specifically explained below based on the drawings.

FIG. 1 is a sectional view showing an example of the method of drawing and heat treating an optical fiber used in the present invention. In the figure, 1 is a plastic optical fiber, 2 is a spinneret, 3 is a cooling chimney, and 4 is a take-up roller for the undrawn plastic optical fiber, which also serves as a supply roller to the drawing zone. This roller speed is required at Vl (m7 seconds). 5
6 is a static eliminator, 6 is a stretching zone equipped with a block builder, 7 is a fan for hot fluid circulation, 8 is a heater for heating fluid, 9 is a heated fluid introduction part, 10 is a stretching roller, that is, the stretched plastic A roller pulls out the optical fiber from the drawing zone, and its speed is V2 (m7 seconds).

1 is a heat treatment roller, and 12 is a winding section.-0 When the hollow part of the heating zone, that is, the inside of the yarn passage is circulated countercurrently, the temperature inside the yarn passage becomes uniform, and as described above. As described above, since the heat transfer film on the surface of the optical fiber can be constantly renewed and covered, heat transfer is good, and it is therefore possible to shorten the length of the heater. If only the block heater is heated, the temperature will be uneven, and the above effect cannot be expected.

In FIG. 1, an undrawn plastic optical fiber 1 discharged from a composite spinneret 2 and cooled is guided to a drawing zone [6] at a speed V1 (m7 seconds) while discharging the cooled optical fiber 1.
A heated air stream is blown from 9 facing the running direction of the paper, and stretched to a predetermined magnification by the traction force of a rear stretching roll at a speed of V2 (m7 seconds). After long heat treatment and sufficient cooling, it is rolled up.

FIG. 2 is a diagram showing the point at which thinning by stretching is completed, as described above.

FIG. 3 shows the thinning film due to stretching deformation of the optical fiber when the manufacturing method of the present invention is adopted, and the cross-sectional area of the fiber A (mm2 >= 18
- The length L (m) of the stretching heating zone and the roller speed conditions, that is, are selected to satisfy the following conditions, and furthermore, if the thinning completion point by stretching is considered in the range of -10≦P≦10 as described above, the thinning will be more uniform. Optical fiber can be obtained. In that case, the central BC
As shown in the figure, the profile of the optical fiber in the cooling region is not disturbed, the wire diameter variation is small, and the desired light transmittance and bending resistance can be imparted. J5A is caused by excessive heating and has poor mechanical properties. In the case of D, the FJO heat is insufficient and the wire diameter fluctuates greatly.

In Figure 4, the cross-sectional area A (mm2) of the optical fiber is plotted on the horizontal axis, and the average passing time of the stretching zone is expressed as Vl + V2.
When the vertical axis is taken as the vertical axis, the area of stretching conditions that satisfy the object of the present invention is shown with diagonal lines.

Hereinafter, the present invention will be explained in more detail based on Examples.

[Example] In the Examples, translucency was confirmed by using a tungsten-halogen lamp as a light source and determining wavelength characteristics using a diffraction grating spectrometer. Usually wavelength 6
Using the value at 50 nm, the target is preferably 300 dB/km or less for a wire diameter of 250 microns, and 180 dB/km or less for a wire diameter of 500 microns or more.

Examples 1-13. Comparative Examples 1 to 10 After sufficiently purifying commercially available methyl methacrylate-1, the liquid was sent to a polymerization tank, and initiator A3 and chain transfer agent were added to carry out continuous bulk radical polymerization, leading to the demonomerization step. , weight average molecular weight 84,000. Polymethyl methacrylate having a residual monomer content of 0.11% by volume was prepared and supplied to side 8 of the melt composite spinning section. The TQ measured by DSC method by increasing the temperature at 10'C/min was 118°C.

On the other hand, a commercially available vinylidene fluorite-detrafluoroethylene copolymer (80/20 ratio) was supplied to the fine side of the composite spinning section, and the spinning temperature was 24 o'c and the cooling air speed was 0.4 m/sec. Composite spinning was performed. At this time, adjust the discharge amount on the 8th side and fine side for each wire diameter, and set the thickness of the sheath part as follows:
In the case of a wire diameter of 250 microns, the diameter was 5 microns, and in the case of 1000 microns and 2000 microns, the diameter was 10 microns. The undrawn plastic optical fiber thus obtained is continuously guided to the non-contact heating stretching/non-contact constant length heat treatment apparatus shown in Fig. 1, where it is stretched and constant length heat treated under conditions not shown in Table 1. I did this.

The optical fiber in the drawing zone is gripped at the entrance and exit of the drawing zone, simultaneously cut at both ends, quickly removed from the drawing zone without applying substantial tension or shrinkage, and then pulled into the drawing zone. Measure the change in fiber diameter with a micrometer and
Based on the definition of E, the thinning completion point of J during stretching was determined.

In addition, the fluctuation range of the wire diameter was determined using an Anritsu laser outer diameter measuring device, and the light transmission loss was measured using the method described above. Two round rods with a diameter of 10 mm are placed facing each other at an interval of 3 Q mm, and between them the optical fiber is placed under tension and bent continuously in a -21 = S-shape. It was also measured in a dry heat oven at 80'C for 24 hours.
The treatment was carried out without any time constraints, and the shrinkage rate was determined from the rate of change in length before and after treatment. These results are summarized in Table 2.

All the properties of the plastic optical fiber drawn within the range measured by the present invention were satisfactory, and a high-quality fiber with excellent bending resistance could be obtained.

= 22 = Table 2 [Effects of the Invention] The plastic optical fiber manufactured according to the present invention has small wire diameter fluctuations, excellent mechanical properties, especially bending resistance,
It is uniform in the longitudinal direction, has high quality, and has good translucency and dimensional stability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the method of drawing and heat treating an optical fiber used in the present invention. FIG. 2 is a side view showing the point at which thinning of the PlusDeck optical fiber is completed by drawing. FIG. 3 is an explanatory diagram showing a thinning profile due to stretching of an optical fiber when the manufacturing method of the present invention is adopted. FIG. 4 is a relationship illustrating the range of stretching conditions that satisfy the object of the present invention, where the horizontal axis is the cross-sectional area A (mm2) of the optical fiber and 1+V2, which represents the average passing time of the stretching zone, is the vertical axis. Fig. 1: Nibrassbook optical fiber 2: Spinneret 3: Cooling boom 4: Undrawn plastic optical fiber take-up roller;
Also, supply roller 5 to the stretching zone: static eliminator 6: equipped with a beater! i'TJ stretching zone 7
:1) [1 Heat fluid circulation fan 8: Fluid heating regulator 9: Heating fluid introduction part] O: Stretching roller] 1: Heat treatment 1] - Roller 12: Winding part

Claims (1)

[Claims] (1) A method for producing a plastic optical fiber, which comprises heating and stretching the plastic optical fiber in a non-contact manner under conditions expressed by the following formula. 15A≦2L/(V_1+V_2)≦15A+16 Where, A: Target cross-sectional area of drawn fiber (mm^2) V_1: Speed of roller supplying plastic optical fiber to heated drawing zone (m/sec) V_2: Plastic from heated drawing zone Optical fiber drawing roller speed (m/sec) L: Length of heated stretching zone (m)