JP4759624B2 - Manufacturing method of plastic optical fiber - Google Patents

Description

  The present invention relates to a method for producing a transparent plastic linear body, and more particularly to a method for producing a plastic optical fiber.

  Conventionally, as a method for producing a transparent plastic linear body (monofilament), a melt extrusion spinning method in which a transparent plastic is melted and extruded from a thin nozzle is often employed. As an example of a method for producing a plastic optical fiber using the melt extrusion spinning method, for example, there is a method in which methyl methacrylate monomer is bulk polymerized and the fiber is continuously extruded without going through pellets. The extruder used for the melt extrusion spinning method is a large-sized apparatus and is expensive, but like this method, the melt extrusion spinning method is suitable for mass production. However, a long time is required from the start of the operation of the extruder to the start of the steady operation, and the loss of time and material is large. For this reason, when changing the material, such as changing the type of resin of the material or changing the type of additive, there is a large loss for switching, and the melt extrusion spinning method is not necessarily suitable for the production of a small variety of products.

  As another method for producing a transparent plastic monofilament, there is a method in which a transparent plastic rod-shaped body is molded, and then the tip is heated to draw a thin monofilament (hereinafter, this method is referred to as “stretching method”). Although this drawing method is not suitable for mass production, it is easy to produce not only circular cross-sectional shapes but also irregular shapes such as rectangles, and it is easy to change materials, producing a wide variety of products. Suitable for The method for producing a plastic optical fiber by the drawing method is often used for producing a plastic optical fiber for special applications such as a fluorescent fiber and a scintillation fiber. In the stretching method, generally, the tip of a transparent plastic rod is heated by a cast heater of about 200 to 350 ° C. or the like. According to this heating method, a part of the heat from the heater is conducted to the surface of the rod-shaped body using air or an inert gas as a medium, the rod-shaped body is heated, and far infrared rays radiated from the heater surface are The surface of the rod is heated directly. Since the transparent plastic has high absorption efficiency of far infrared rays, when a heater is used, only the surface of the rod-like body is heated by heating using air or the like as well as heating by far infrared rays.

  In general, since the thermal conductivity of plastic is small, when trying to heat a thick rod-shaped body using a heater or hot air in the stretching method, only the surface is heated, and heat is not transmitted to the center of the rod-shaped body, so the temperature of the center is It did not rise and could not be stretched. If the temperature of the heater or hot air is raised in order to raise the temperature to the center of the thick rod-shaped body, only the surface temperature of the rod-shaped body will rise excessively, and foaming or heat deterioration will occur on the surface of the rod-shaped body. When an optical fiber is manufactured from such a rod-shaped body, defects and wire diameter irregularities are generated in the optical fiber, and only an optical fiber inferior in light guide loss can be obtained.

  The present invention has been made in view of the above problems, and suppresses foaming and heat deterioration of the surface in the production of a transparent plastic linear body by a stretching method, and produces a high-quality transparent plastic linear body at a high production rate. It aims to provide a method.

The invention of the present invention relating to a method of manufacturing a transparent plastic optical fiber that solves the above-mentioned problems is a transparent plastic having a cross-sectional shape substantially similar to that of the transparent plastic rod-shaped body by heating and drawing the tip of the transparent plastic rod-shaped body. In the method for producing a linear body, the transparent plastic rod-shaped body includes at least one selected from an acrylic resin, a polystyrene resin, a polycarbonate resin, and a PET resin, and the diameter of the transparent plastic rod-shaped body is in a range of 70 mm to 200 mm. , preferably in the range of 70Mm～100mm, mainly using a near infrared ray source for heating the transparent plastic rod-shaped body, the near infrared source used to heat the transparent plastic rod-like body near infrared color temperature 1500~4000K A radiator that is heated with a near infrared source Between the plastic rod-like body, characterized in that the short-wavelength cutoff filter for blocking light of a wavelength shorter than 700~800nm is provided.

In the invention of the method for producing a transparent plastic linear body, the near infrared source used for heating the transparent plastic rod has a peak wavelength of 0.7 to 3 μm and a color temperature of 1000 to 4000 K. It is preferable that the inside of the rod-shaped body can be heated uniformly and the heating efficiency is not impaired. Further, between the transparent plastic rod-like body to be heated and the near infrared source, by providing a short wavelength cutoff filter for blocking light having a short wavelength less short wavelength than that of visible wavelength or ultraviolet wavelength, visible light or ultraviolet light Ru can be prevented material degradation of the rod-like body according to.

As transparency plastic rod-like body, there can be used those composed of a bundle of a number of plastic optical fiber, also plastic rod-shaped body, may contain a fluorescent agent. The rod-shaped body is not limited to a cylindrical shape, and a deformed cross-section linear body can be manufactured by forming the rod-shaped body into a deformed shape such as a rectangle or a triangle.

According to the present invention, it is possible to provide a method for producing a high-quality transparent plastic optical fiber by suppressing surface foaming, heat degradation and light degradation in the production of a transparent plastic optical fiber by a stretching method.

It is the schematic which shows an example of the near-infrared heating furnace and extending | stretching apparatus which are used for this invention. It is a figure which shows the radiant energy distribution of a halogen lamp. It is a figure which shows the light absorption coefficient of an acrylic resin. It is a figure which shows the method and result of a heating experiment using near infrared rays. It is a figure which shows an example of the wavelength characteristic of a short wavelength cut off filter suitable for using in combination with a halogen lamp.

  A near-infrared heating furnace and stretching apparatus used in the present invention are shown in FIG. The near-infrared heating furnace includes a near-infrared ray source 2, and near-infrared rays emitted from the near-infrared ray source 2 are irradiated to the transparent plastic rod 6 through the furnace core tube 4. The near-infrared ray source 2 is disposed at equal intervals on the outer periphery of the transparent plastic rod-like body 6 with the furnace core tube 4 inside. If the near-infrared ray sources 2 are not arranged at equal intervals, even if the transparent plastic rod-like body is a perfect circle, the stretched transparent plastic linear body may become an ellipse or an irregular shape. In order to obtain a perfect circular transparent plastic linear body, a large number (for example, 8 or more, preferably 10 or more) of the near-infrared sources 2 are preferably arranged. If necessary, the near-infrared ray source 2 may be arranged in two or more stages in the vertical direction.

As the near-infrared source, a radiant heat transfer source similar to so-called Planck's blackbody radiation is used. An incandescent light bulb or a halogen lamp for illumination using a tungsten filament as a radiation source is preferably used as the radiation heat transfer source. FIG. 2 shows the wavelength distribution of the radiation source temperature (color temperature) and Planck's blackbody radiant energy. The relationship between the wavelength λmax giving the maximum value of the radiant energy and the absolute temperature T is expressed by the following equation ( In 1), the total radiant energy E is expressed by the following formula (2), respectively. Equation (2) is called Stefan Boltzmann's law.
λmax · T = 2882 (μm · K) (1)
E = σT ⁴ (σ: constant) (2)
FIG. 2, formula (1) and formula (2) show that the higher the temperature, the shorter the emission peak wavelength, and the more suddenly the radiant energy increases. For example, when the color temperature of the halogen lamp is 3000 K, the emission peak of the halogen lamp is in the vicinity of 1 μm from FIG. 2 and formula (1). Here, the absorption coefficient of an acrylic resin, which is an example of a transparent rod-shaped material, is shown in FIG. 3 (Source: Toshikuni KAINO, et al., Review of the Electrical Communication Laboratories Vol.32 No.3 (1984) P478- 488). Acrylic resin is transparent at wavelengths below 0.7 μm and absorbs little, but the absorption gradually increases from a visible wavelength of 0.7 μm to a wavelength of 3 μm. At far-infrared wavelengths exceeding 3 μm, the absorbance per cm is 10 It can be seen from FIG. 3 that the above (that is, 99% absorption after passing 1 cm) becomes almost opaque. That is, for internal heating to a depth of several centimeters to 10 centimeters, it is preferable to heat with near infrared rays having a wavelength of about 1 μm, translucent to acrylic resin, and about half of which is absorbed. On the other hand, when far infrared rays having a radiation peak exceeding 3 μm are used for heating, since the absorption coefficient is large, the far infrared rays are almost absorbed by the surface of the acrylic resin transparent body and become heat, which causes foaming and heat deterioration of the surface. Easy to wake up. On the other hand, when visible light having a radiation peak of less than 0.7 μm is used for heating, the light absorption coefficient is small, so that visible light is transmitted, and the acrylic resin transparent body is not heated. There is a high risk of

  FIG. 3 shows the extinction coefficient of the acrylic resin. However, since it has a characteristic that light is absorbed in the infrared wavelength region in the case of a general transparent plastic such as polystyrene resin, polycarbonate resin, and PET resin, It can be suitably used in the present invention. According to the present invention, by using near-infrared rays for heating the transparent plastic rod-like body, the rod-like body can be heated from the inside, and it is transparent as in the case of using a conventional heat transfer heat source such as a cast-in heater. The surface temperature of the plastic rod-like body can be prevented from rising more than necessary, and foaming and heat deterioration can be suppressed. Also, according to the internal heating by the near-infrared source, it is possible to heat the inside of the rod-shaped body in a shorter time than the case of using the conduction heat transfer heating source, and the stretching speed of the transparent plastic linear body is conventionally increased. It is possible to stretch a transparent plastic rod having a larger diameter than before.

  The near-infrared source used for heating the transparent plastic rod may be any heating source as long as it is a black body radiator having a peak wavelength of 0.7 to 3 μm and a color temperature of 1000 to 4000 K. Those having a wavelength of 0.8 to 2 μm (color temperature 1500 to 3500 K) are more preferable. For example, a halogen lamp with high radiation efficiency can be preferably used.

  It was confirmed by the test method schematically shown in FIG. 4A that the inside of the plastic transparent body is effectively heated by using near infrared rays for heating. Here, a thermoelectric body is attached to the center of the front and back surfaces of an acrylic resin plate (two types of transparent and black) having a vertical dimension of 70 mm, a horizontal dimension of 90 mm, and a thickness of 10 mm. Near-infrared rays were irradiated from a distance using a halogen lamp (100 V 500 W, color temperature 2950 K), and the temperature change was measured (measurement results are shown in FIG. 4B). Considering based on FIG. 4 (b), in the case of a transparent acrylic resin plate, the surface temperature 3 minutes after the start of irradiation is 80 ° C., the back surface temperature is 28 ° C., and the heating efficiency is not high, but the temperature difference between the front and back sides Is as small as 52 ° C. This indicates that internal heating is progressing. On the other hand, although the result of the test using a black acrylic resin board was shown in FIG. 4 for the comparison, this is shown as simulation of conduction heat transfer or far-infrared heating. In the case of a black acrylic resin plate, the temperature of the surface 3 minutes after the start of irradiation is 143 ° C., the temperature of the back surface is 26 ° C., the temperature difference between the front and back is as large as 117 ° C., and the heating efficiency is high, but the surface heating is excessive. Indicates that it is progressing. In the case of a black acrylic resin plate, the temperature on the back surface does not increase for about 1 minute from the start of irradiation, whereas in the case of a transparent acrylic resin plate, the temperature increase on the back surface starts simultaneously with the start of irradiation. This also indicates that the inside is directly heated by near infrared rays rather than heat conduction.

  Since halogen lamps sometimes generate harmful visible light and ultraviolet rays, in order to remove visible light and ultraviolet rays unnecessary for heating the transparent plastic rods between the halogen lamp and the transparent plastic rods, What is necessary is just to arrange | position the short wavelength cutoff filter 1 which interrupts | blocks a short wavelength of 700-800 nm or less (refer FIG. 1). An example of the wavelength characteristics of a short wavelength cutoff filter suitable for use in combination with a halogen lamp is shown in FIG. When manufacturing a plastic scintillation fiber according to the present invention, it is particularly preferable to dispose a short wavelength cutoff filter. This is because the fluorescent material may be deteriorated and faded or the resin may be colored due to the fluorescent agent when the rod-shaped body is irradiated with ultraviolet rays at the time of heating and stretching.

  In the near-infrared heating furnace and stretching apparatus used in the present invention shown in FIG. 1, while protecting the electric wire and the short-wavelength cutoff filter in the heating furnace, in order to enhance the effect of near-infrared heating, In order not to raise the temperature excessively, a cooling fan 3 is attached to the near infrared heating furnace. The core tube 4 can prevent the drawing diameter from fluctuating due to the transparent plastic rod 6 hitting the cooling air from the cooling fan 3 of the near infrared heating furnace.

  The transparent plastic rod 6 is lowered at a constant speed by the constant speed lifting device 5. A take-up machine 9 is provided at the lower part of the near-infrared heating furnace, and a linear body stretched in a shape substantially similar to the transparent plastic rod-like body 6 passes through the take-up machine 9 to be used as a cutting machine, a winder, or the like. Sent. The outer diameter of the transparent plastic linear body is measured by the outer diameter measuring device detection unit 7 and the result is displayed on the outer diameter measuring device display unit 8 and is taken out according to the predetermined outer diameter (target value) and the difference. The take-up speed at the machine 9 is controlled.

  The invention of the present method for producing a transparent plastic linear body using such a near-infrared heating furnace and a stretching apparatus can be used for producing a plastic optical fiber. In addition, it can be used for the production of monofilaments having a small diameter or a large diameter. In the case of manufacturing a plastic optical fiber, as a transparent plastic rod used for the manufacturing, for example, a core material / cladding material made of styrene resin / acrylic resin, acrylic resin / fluorine resin, polycarbonate resin / acrylic resin is used. Can be mentioned. Further, the transparent plastic rod-like body may be composed of a bundle of a large number of plastic optical fibers, and if a fluorescent agent is added to the transparent plastic rod-like body, a fluorescent fiber or a scintillation fiber can be suitably produced.

Example 1
In the near-infrared heating furnace and drawing apparatus shown in FIG. 1, as the near-infrared source 2, 12 halogen lamps (color temperature when supplying 100V is 2750K on a circumference of 120 mm radius. Lamp supply voltage 75V, current 19.5A). ) Are arranged at equal intervals in two stages (a total of 24). Inside the halogen lamp, an infrared transmission filter (ITF-50S-80IR manufactured by Sigma Koki Co., Ltd.) having transparency shown in FIG. 5 was attached. A plastic optical fiber rod-shaped body made of polystyrene resin (core material) and acrylic resin (cladding material) having a diameter of 70 mm is set in this spinning device, and the tip of the rod-shaped body is halogenated at a speed of 1.65 mm / min. The resin that has been introduced into the heating furnace, heated, softened, and hung down is guided to the take-out machine through the outer diameter measuring device detector (take-off speed: 7.2 m / min), and drawn into a plastic optical fiber having a diameter of 1 mm and no foam. I was able to. The light guide loss of this plastic optical fiber was good at 195 dB / km at a wavelength of 670 nm.

(Example 2)
The apparatus used in Example 1 was introduced by introducing a rod for plastic scintillation fiber having a diameter of 70 mm composed of polystyrene resin (core material) and acrylic resin (cladding material) containing a fluorescent agent for plastic scintillator. A plastic scintillation fiber having a diameter of 1 mm without foaming could be produced by heating and drawing under the same rod-like body pulling-down rate and heating conditions as in Example 1. The fluorescent agent contained in the polystyrene resin is 2- (4-tbutylphenyl) -5- (4-biphenyl) 1,3,4 oxadiazole 1% (manufactured by Ciba Geigy), 4-4′bis (2,5 Dimethylstyryl) diphenyl 0.02%. In Example 2, the take-up speed with the take-up machine was 7.5 m / min. The amount of light emitted from this plastic scintillation fiber was satisfactory without any problem, and the attenuation length, which is an index of transparency of the scintillation fiber, was as good as 380 cm.

(Example 3)
By introducing into the apparatus used in Example 1 a rod-shaped body for a plastic optical fiber having a diameter of 100 mm and made of polystyrene resin (core material) and polymethacrylic resin (cladding material), and heating and stretching. A plastic optical fiber having a diameter of 1 mm without foaming could be produced. In Example 3, the lamp supply voltage of the halogen lamp is 85V, and the current is 22.5A. The pulling-down speed of the rod-shaped body was 2.0 mm / min, and the pulling speed with the pulling machine was 19.5 m / min. When the light guide loss of this plastic optical fiber was measured, it was 185 dB / km at a wavelength of 670 nm.

(Comparative Example 1)
A stretching apparatus (heater temperature of 320 ° C.) having a structure similar to that shown in FIG. 1 and incorporating a brass cast heater with an inner diameter of 150 mm instead of a halogen lamp as a heating source was used. In the same manner as in Example 1, a 70 mm diameter plastic optical fiber rod made of polystyrene resin (core material) and polymethacrylic resin (cladding material) was introduced into a stretching apparatus, and heated and stretched to obtain a diameter. Attempted to produce a 1 mm plastic optical fiber. The pulling-down speed of the rod-shaped body at this time was 1.1 mm / min, and the pulling speed with the take-up machine was 4.8 m / min. Next, when the pulling speed of the rod-shaped body was changed to 1.65 m / min (the same stretching speed as in Example 1) in order to increase the stretching speed, stretching could not be performed because the internal heating of the rod-shaped body was not sufficiently heated. . Therefore, when the temperature of the brass casting heater was raised to 340 ° C., foaming occurred in the heated portion on the surface of the rod-like body, and a good optical fiber with little wire diameter unevenness and no defects could not be obtained. When the light guide loss of this plastic optical fiber was measured, the light guide loss was as low as 450 dB / km.

(Comparative Example 2)
An optical fiber rod having a diameter of 100 mm, which is the same as that of Example 3, was introduced into the apparatus used in Comparative Example 1, and the plastic optical fiber was manufactured by heating and stretching. The temperature of the brass casting heater was 340 ° C. and the pulling speed of the rod-shaped body was 0.5 mm / min. However, since the internal heating of the rod-shaped body was not sufficiently heated, stretching could not be performed. Therefore, when the temperature of the heater was raised to 360 ° C., the surface portion of the rod-shaped body foamed, and a good optical fiber with little wire diameter unevenness and no defects could not be obtained.

1: Short wavelength cut filter 2: Near-infrared ray source 4: Core tube 5: Constant speed elevating device 6: Transparent plastic rod 7: Outer diameter measuring device detection unit 8: Outer diameter measuring device display unit 9: Take-out machine

Claims (4)

In the method of manufacturing a transparent plastic optical fiber having a cross-sectional shape substantially similar to the transparent plastic rod-shaped body by heating and drawing the tip of the transparent plastic rod-shaped body, the transparent plastic rod-shaped body is made of acrylic resin, polystyrene At least one selected from a resin, a polycarbonate resin, and a PET resin, the diameter of the transparent plastic rod is in a range of 70 mm to 200 mm, and a near infrared source is mainly used for heating the transparent plastic rod, and the transparent plastic The near-infrared source used for heating the rod-shaped body is a near-infrared radiator having a color temperature of 1500 to 4000 K, and has a short wavelength of 700 to 800 nm or less between the near-infrared source and the heated transparent plastic rod-shaped body. Plus a short-wavelength cutoff filter that blocks light Method of manufacturing a click optical fiber.   2. The method for producing a plastic optical fiber according to claim 1, wherein the diameter of the transparent plastic rod is in a range of 70 mm to 100 mm.   The method for producing a plastic optical fiber according to claim 1, wherein the near infrared ray source is a halogen lamp.   The method for producing a plastic optical fiber according to any one of claims 1 to 3, wherein the transparent plastic rod-shaped body is made of a bundle of a large number of plastic optical fibers.

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