JPH01254904A - Plastic optical fiber - Google Patents

Abstract

PURPOSE:To obtain optical fiber comprising heat resistant polycarbonate having superior light transmitting characteristic in a near infrared region by specifying a relation between a transmission loss measured for 770nm wavelength and that measured for 633nm wavelength. CONSTITUTION:The title optical fiber is constituted of a core comprising a polycarbonate having >=0.4dl/g and <0.60dl/g intrinsic viscosity (in methylene chloride) and a shell comprising fluorinated polycarbonate, wherein a relation between a transmission loss L770(dB/km) measured for 770nm wavelength and a transmission loss L633(dB/km) measured for 633nm wavelength is defined by L770/L633<0.60. Such optical fiber is produced by drawing a polycarbonate which is melted completely at >=260 deg.C by extruding the polycarbonate through a nozzle in a compound melt spinning process, without cooling the polycarbonate to below the m.p. (-20 deg.C) of the polycarbonate crystal, keeping the temp. of a range of >=10cm below the spinning nozzle at >=70 deg.C. Thus, plastic optical fiber having low transmission loss in a near infrared region is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a plastic optical fiber with low transmission loss in the near-infrared region.

[Prior art] Although plastic optical fibers have lower transmission loss levels than inorganic glass optical fibers,
It has been developed as a short-distance optical fiber because it is easy to process and can be easily obtained with a large diameter. Among these, high-performance plastic optical fibers with a core material of polymethyl methacrylate, which has high optical transparency, have a transmission loss value of 200 dB/Xm or less, and in this case, especially Utilizing its good optical transmission properties in the visible wavelength region, it is widely used in the field of optical guidance such as displays and image transmission. However, in the case of plastic optical fibers made of polymethyl methacrylate as a core material, the glass transition temperature of polymethyl methacrylate constituting the core material is 100°C, so the optical fiber has a heat resistance of 100°C or higher. The disadvantage is that it cannot be used in the necessary fields. In order to eliminate these drawbacks, plastic optical fibers using polycarbonate as a core material have been developed. As is well known, polycarbonate has a glass transition temperature of 140°C, so it is expected to be used in high-temperature areas such as the engine room of an automobile or the inside of computer equipment. The purpose of use in such fields is for high-speed signal transmission rather than optical guidance of visible light, but light sources capable of high-speed response are not available (in the visible light range), and LEDs and LDs in the near-infrared range are used.
It is necessary to use Therefore, even if a heat-resistant optical fiber can be obtained, it must be said that it is of no use if the transmission loss in the near-infrared region is high. However, the key point for the polycarbonate optical fibers that have been proposed so far is the transmission loss in the visible light region rather than the near-infrared region, and it is difficult to develop a polycarbonate optical fiber that has much better transmission loss in the near-infrared region than in the visible light region. The current situation is that this has not been done.

Incidentally, although JP-A-61-262706 proposes a polycarbonate optical fiber.

Here, only the improvement of optical transmission loss in the visible light region is pursued, and no recognition is given to the improvement of transmission loss in the near-infrared region. That is.

The transmission loss characteristics of the disclosed polycarbonate optical fibers are, for example, 780 dB/Km at 660 nm and 700 dB/Km at 770 nm, which remain at approximately the same level and are not suitable for signal transmission. .

[Problems to be Solved by the Invention] The present invention solves the above-mentioned drawbacks, has much better light transmission properties in the near-infrared region rather than the visible light region, and has heat resistance. The purpose of the present invention is to provide an optical fiber using polycarbonate as a core material suitable for high-speed signal transmission.

[Means for Solving the Problems] The present invention provides a plastic optical fiber having a polycarbonate core and a fluorinated polycarbonate sheath having a lower refractive index than the core, with a transmission loss L of 770 (dB/Km) measured at a wavelength of 770 nm. ) and 633nm
Between the transmission loss L633 (dB/Km) measured at
The present invention relates to a polycarbonate optical fiber having transmission loss characteristics such that the following relationship holds: 770/L633<0.60.

In the composite melt spinning process, such optical fibers are
When the polycarbonate completely melted at a temperature of 260°C or higher is discharged from the spinneret, it is spun without being cooled to less than 10°C (melting point of polycarbonate crystals -20°C), and a length of 10 cm or more below the spinneret is spun at 70°. It can be manufactured by keeping the temperature above C.

The polycarbonate used in the present invention is generally produced by reacting dihydric phenol with a carbonate precursor such as phosgene.

As the dihydric phenol used as a raw material for polycarbonate, bisphenol is preferred, particularly 2,2-bis(4-hydroxyphenyl)propane.

(hereinafter referred to as bisphenol A) is preferred.

Further, part or all of bisphenol A may be replaced with other dihydric phenol. 2 other than bisphenol A
As the hydric phenol, 1.1-(4-hydroxyphenyl)ethane [bisphenol El.

1.1-bis(4-hydroxyphenyl)cyclohexane [bisphenol Z], 1.1-bis(4-hydroxyphenyl)butane, 2,2-bis(3-methyl-4-
hydroxyphenyl)propane, 2,2-bis(3゜5
dimethyl-4-hydroxyphenyl)propane.

1.1-bis(3,5dimethyl-4-hydroxyphenyl)methane, 1-phenyl-1,1-(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl-3,5-dichlorophenyl) ) propane, 2,2-
There are dihydric phenols such as bis(4-hydroxyphenyl-3,5-dibromophenyl)propane. Also.

These polycarbonates may contain aromatic dioxy compounds or aliphatic dioxy compounds other than the dioxy compound as the main component, and furthermore, polycarbonate 1 itself may contain two or more different types. There may also be a mixture of polycarbonate.

On the other hand, the fluorine-containing polycarbonate polymer disposed in the sheath material layer in the present invention is produced by the same reaction as the polycarbonate required for the core material, but considering the heat resistance of the optical fiber, the following general formula (A) is used. A fluorine-containing polycarbonate containing the shown units as a main component and having a refractive index lower than that of the core material by 0.07 or more is suitable.

Rf l 11 Rf" ○ (In the formula, Rf and Rf' each represent a fluoroargyl group having 1 to 6 carbon atoms or a perfluoroalkyl group having 1 to 4 carbon atoms.) Here, as Rf and Rf' Examples include the following groups, among which it is most preferable that both the Rf group and the Rf' group are CF3 groups.

1)-(CF2)mCF3 (m=0~4)-(C
H2)n(CF2)+! 1CF3 (n=0~2.m=0
~・3) n-fluoroalkyl group such as.

2)-(CH2)nCF(CF3')2 (n=0~
2)-(CH2)nC(CF3)3 (n,=o-
1so- or tert-fluoroalkyl group such as 2).

3) Cyclic fluoroalkyl groups such as perfluorocyclohexyl.

4) Fluoroalkyl groups containing halogen such as -CF3I (X=CI, B]~, I).

Of course, the fluorinated polycarbonate of the present invention may have a fluoro or perfluoroalkyl group in the aromatic ring.

Intrinsic viscosity of polycarbonate used in the present invention: core material,
Both sheath materials must be 0.40 or more and less than 60 dl/g, preferably 0.45-0.55 dl/g, 7
g range. When the intrinsic viscosity becomes 0360 or more.

It is necessary to set the melting temperature in the spinning process to an extremely high temperature, such as 330° C., and the resulting optical fiber has a large transmission loss due to thermal deterioration of the polycarbonate. Further, when the intrinsic viscosity is less than 0.40, the fiber diameter unevenness of the obtained yarn becomes irregular, and therefore the transmission loss also worsens.

For composite melt spinning, the intrinsic viscosity should be 0.40 or more and 0.6
It is preferable to use a screw-type melt extruder with a vent hole to spin the yarn using a polycarbonate (core material) having a content of less than 0. The temperature of the extruder at this time needs to be at least 260°C in order to completely melt the polycarbonate.
However, if the temperature exceeds 320°C, polycarbonate will deteriorate due to heat.
The transmission loss of the resulting optical fiber worsens. Therefore, the highest temperature part of the melt extruder is 260°C
It is necessary that the temperature is 0°C or less, and a more preferable range is 270°C or more and 310°C or less. Next, the polycarbonate melted in the extruder is metered by a gear pump and guided to the bag of the composite spinning head, combined with the sheath material at the pack mouthpiece, and discharged from the mouth hole. At this time,
In order to improve the uniformity of the fiber diameter and obtain good light transmission, it is necessary to lower the temperature of the composite spinning head to 280°C or less (if the highest temperature part exceeds 280°C). however.

Even in this case, if the discharge temperature from the mouthpiece is lower than the melting point of the polycarbonate crystal by more than 20°C.

Optical transmission loss in the near-infrared region such as 770° is worsened probably because crystal nuclei are generated in polycarbonate. In this case, although the optical transmission failure in the visible light region such as 633 nm also shows a tendency to worsen, there is no adverse effect in the near-infrared region such as 770 nm. (Fifth gear loss L 770 (d
B/Km) and transmission loss measured at 633 nm, 63
3 (dB/Km), i.e. L 770/L, 6
33 becomes 0.60 or less. The cause of this poor transmission loss in the near-infrared region is not clear, but it is presumed that the generation of crystal nuclei has a subtle effect.For this reason, polycarbonate It is preferable that the discharge temperature from the mouthpiece of the crystal is equal to or higher than (the melting point of the crystal -20°C).The melting point of polycarbonate crystals with an intrinsic viscosity of 0.40 to 0.60 dl/g is usually around 245°C, The temperature at which the polycarbonate is discharged from the mouthpiece is 225°C or higher, preferably 245°C or higher.

The discharge temperature of polycarbonate is 225°C or higher.

Particularly at temperatures above 235°C, it is not always easy to maintain good uniformity in fiber diameter. but.

As described above, simply lowering the discharge temperature worsens the transmission loss. In this case, optical transmission loss in the near-infrared region first becomes worse. Furthermore, although it is not necessarily easy to obtain good fiber diameter uniformity even if the discharge temperature is high, it has been found that this disadvantage can be overcome by keeping the bottom of the spinneret warm and slowly cooling it. It was. That is, in a composite melt spinning process.

It has been found that it is sufficient to keep a length of 10 cm or more below the spinneret at 70'C or higher, preferably a length of 30 cm or more at 70°C or higher. Furthermore, by keeping the heat under the cap in this manner, optical transmission loss is also reduced. Furthermore, by installing a free-rotating roll downstream of this heat retention area to cut the spinning tension, or by installing a cooling water bath, it is possible to wind at low spinning speeds, and the fiber diameter can be adjusted arbitrarily. can.

[Effects of the Invention] The polycarbonate optical fiber of the present invention has a uniform fiber diameter and exhibits good transmission loss at a wavelength of 770 nm. It is far more advantageous than other fibers, and its uses as optical transmission fibers are greatly expanded. Moreover, combined with the good heat resistance of polycarbonate optical fibers, a wide range of applications can be expected, and its industrial value and significance are extremely high.

[Examples of the Invention] In order to explain the present invention more specifically, Examples and Comparative Examples will be described below, but the present invention is not limited to these Examples.

The physical properties in Examples and Comparative Examples were evaluated using the following test method.

(1) LED with a wavelength of 770 nm driven by an optical transmission loss stabilized power source
Using a 633RO++ helium-neon laser as a light source, a 30 m long sample polycarbonate optical fiber was cut 4 times in 5 m increments up to 10 m, and the light intensity (2) was measured using an optical power meter. The average value of the optical transmission loss calculated by the following formula from the incident light amount Ii and the output light iIo for each 5 m length was used.

Transmission loss (dB/Km) ='(1010,005)l
(2) Fiber diameter irregularity sample The fiber diameter of the polycarbonate optical fiber was measured at n = 50 points at 10 cm intervals using a micrometer,
Calculate the average value X and standard deviation σ, and fiber diameter unevenness (%) = (
6σ/X)X100 was used.

(3) Crystal melting point was measured using a differential thermal analyzer at a heating rate of 10°C/mil.

[Example 1] After reacting bisphenol A with phosgene at 20 to 30°C in the presence of methylene chloride solvent, sodium hydroxide, p-tert-butylphenol and triethylamine, washing was repeated and methylene chloride was then removed. Polycarbonate was obtained. This is supplied as a polymer required for the core material to a screw-type melt extruder with a vent hole set at a maximum temperature of 280'C, passed through a gear pump at 280°C, and sent to a core-sheath two-component composite spinning head at 250°C. sent.

The intrinsic viscosity of the obtained polycarbonate was 0.45 d1/
g, the crystal melting point was 245°C2 and the refractive index was 1.59. Further, the vent vacuum degree of the extruder was 5 Torr.

On the other hand, as a sheath component polymer, it is represented by the above formula (A), and R
Fluorinated polycarbonate (specific viscosity (η5p) 0.19, refractive index 1.51) in which both f and Rf' are CF3 is melted in an extruder with a maximum temperature of 280°C, then passed through a gear pump at 280°C and heated to 250°. It was sent to a core-sheath two-component composite spinning head of C. Note that 9 spinning heads include the Journal of the Japan Institute of Textile Science and Technology (Textiles and Industry) Vol. 42, No.

4 (1986) P, 114 was used.

The core-sheath binary molten polymer was produced from a composite spinneret at 250%
It is discharged at 120°C and 10cm, then passed through a 70°C and 60cm heating area, and then transferred to a godet roller. 2 Then, it is stretched at 165°C for 1.5@2
I wound it up.

The obtained optical fiber had a core diameter of 970 μm and a sheath diameter of 30 μm.
μm, outer diameter 1, OOOμ mouth, fiber diameter unevenness is 6.0%
Met. Optical transmission loss is 520dB/770nmD iron
Km, 900 dB/Km at 633 nm, the ratio was 0.58, and the optical transmission loss at 770 nm was extremely good.

[Comparative Example 1] An optical fiber was obtained in the same manner as in Example 1 except that the composite spinning head temperature was 220°C and the composite spinning head was discharged at 220°C. At this time, the fiber diameter unevenness was 6.8%, but the optical transmission loss was 860 dB/Km at 770 nm.
1010 dB/Km at 633 nm.

The ratio was 0.85.

[Comparative Example 2] An optical fiber was obtained in the same manner as in Example 1 except that the bottom of the base was not kept warm. This sharp fiber diameter unevenness is 28°4%, and the optical transmission loss is 1150 cf/Km at 770 nm, 6
It was 1270 dB/Km at 33 nm, and the ratio was 0.91.

[Example 2] An optical fiber was obtained in the same manner as in Example 1 except that polycarbonate (Panlite, manufactured by Yojin Kasei Co., Ltd.) with an intrinsic viscosity of 0 and 50 dl/g was used as the core component. The fiber diameter unevenness of this product was 5.7%. Also, the optical transmission loss is 77
540dB/Km at 0 stop, 1.12 at 633%m
0 dB/Km, and the ratio was 0.48.

Claims (3)

[Claims] (1) In a plastic optical fiber with a polycarbonate core and a polymer sheath with a lower refractive index than the core, the core has an intrinsic viscosity (in methylene chloride) of 0.40 dl.
/g or more and less than 0.60 dl/g, the sheath is made of fluorinated polycarbonate, and the transmission loss L770 (dl/g) measured at a wavelength of 770 nm is
B/Km) and transmission loss L633 measured at 633 nm
(dB/Km), a relationship of L770/L633<0.60 holds true. (2) Transmission loss L770 measured at a wavelength of 770 nm (
dB/Km) and transmission loss L63 measured at 633 nm
3 (dB/Km), the relationship between L770/L633<0.50. (3) Transmission loss L770 measured at a wavelength of 770 nm (
dB/Km) is 800 dB/Km or less, the plastic optical fiber according to claim (1) or (2).