JP2710361B2 - Plastic optical fiber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a plastic optical fiber having low transmission loss from a visible light region to a near infrared region and having excellent long-term heat resistance and stability.

(Prior art) Plastic optical fibers are more flexible and have a larger diameter and a higher numerical aperture than quartz-based optical fibers.
Applications such as internal wiring and short-range communication have begun due to the ease of end face processing and connection.

Plastic optical fiber, which has been put into practical use,
There are the following.

A material using polymethyl methacrylate as a core material and using a vinylidene fluoride-tetrafluoroethylene copolymer or a fluorinated methacrylate copolymer as a sheath material.

Polystyrene core material and sheath material made of polymethyl methacrylate.

In addition, as a heat-resistant plastic optical fiber that can be used even at high temperatures of 100 ° C or higher, the core material has a glass transition point of about 15
One using a polycarbonate at 0 ° C. has been considered. Examples of resins for sheath materials include poly-4-methylpentene-1 and fluorine-containing resin described in JP-A-60-32004, JP-A-61-6604, JP-A-61-22313, and JP-A-62-118307. A methacrylate copolymer, a vinylidene fluoride copolymer and the like are disclosed.

(Problems to be Solved by the Present Invention) A conventional plastic optical fiber using polycarbonate as a core material shows almost no increase in transmission loss even when used at a high temperature of 120 ° C. to 130 ° C. for a short period of time. But,
In the case of a long period of time of 1000 hours or more, there is a disadvantage that coloring occurs due to the progress of thermal deterioration, and the loss gradually increases. This degree increases as the wavelength is shorter, 660n
In the window area near m, the loss increases by more than 300 dB / km.

(Means for Solving the Problems) As a result of intensive studies to solve the above-mentioned problems, the polycarbonate used for the core material has a difference in heat resistance depending on the type of the terminal group, and the phenolic property at the terminal. Polycarbonates having OH groups tend to be colored, which has been found to be the main cause of the increase in transmission loss when exposed to high temperatures for long periods. Therefore, the production of a plastic optical fiber having a long-term heat resistance can be achieved by using a polycarbonate whose most terminals are not phenolic OH groups.

That is, in the present invention, in a plastic optical fiber in which a polymer mainly composed of polycarbonate is used as a core material and a resin having a lower refractive index than the core material is used as a sheath material, the terminal of the polymer used for the core material has a phenolic property. Provided is a plastic optical fiber characterized in that the proportion of OH groups is 0.02% by weight or less as the amount of OH as determined by the TiCl ₄ method.

Suitable polycarbonates for the core include aromatic polycarbonates. Preferably, bisphenol A
It is desirable to use polycarbonate. Copolymers of these polycarbonates with dioxy compounds such as 4,4-dioxyphenyl ether, p-xylene glycol and 1,6-hexanediol, and hetero bonds having not only carbonate bonds but also ester bonds A copolymer may be used. The melt index is 0.5
It is preferably in the range of 2020 g / 10 min and smaller than the melt index of the sheath material.

Polycarbonate is obtained by reacting bisphenol A and phosgene in a mixed solvent of an aqueous sodium hydroxide solution and dichloromethane. The polycarbonate used in the plastic optical fiber of the present invention must thoroughly remove dust and impurities in order to reduce transmission loss. For this purpose, bisphenol A or phosgene as a main raw material, a solvent such as sodium hydroxide solution or dichloromethane, a terminator such as p-tert-butyl phenol,
In addition, it is necessary to remove dirt and impurities from washing water, nitrogen, air, and the like by a method such as distillation or filter filtration. Also, the raw materials used in the polymerization, the ratio of the amount of the solvent and the polymerization aid, and the polymerization conditions must be properly controlled. Due to the effects of impurities in the polymerization tank, deviations in the ratio of raw materials and terminal stoppers, fluctuations in polymerization conditions, etc., the normal reaction does not proceed, and the hydrolysis of intermediates, which is a competitive process, proceeds, and the terminal ends with phenolic It is thought that the amount of low molecular weight polycarbonate having an OH group is increased, and a material having poor mechanical strength and heat resistance is produced. It is also important that after the polymerization, the remaining sodium hydroxide, salt, catalyst and the like are completely washed away with water and that dichloromethane is skipped. In addition, in order to remove low molecular weight components having a large amount of terminal groups, it is preferable to purify by a reprecipitation method or the like.

Next, it was used to quantify the terminal phenolic OH groups.
The TiCl ₄ method will be described. This quantification is based on Die Makromole
Vo described in kulare Chemie 88 (1965) pp215-231
n Performed according to the quantitative method performed by A. Horbach et al. Also,
The following were used as solvents and reagents.

・ Solvent: Use dichloromethane water content of 0.01% or less.

TiCl ₄ solution: 40 g of TiCl ₄ and 0.5 g of acetic acid were dissolved in 1 of dichloromethane.

Acetic acid solution: 50 g of acetic acid was dissolved in 1 of dichloromethane.

First, 50-200 mg of polycarbonate is dissolved in 10 ml of dichloromethane. To this, 10 ml of TiCl ₄ solution and 4 of acetic acid solution
ml was added, and dichloromethane was further added to make a total of 25 ml. Then, the solution was immediately colored orange to red, and the extinction coefficient [cm ^-1 ] of this solution was measured with light from a 546 nm mercury lamp. The equation for determining the extinction coefficient is described below.

ε = [10g ₁₀ (I ₀ / I)] / d ε: extinction coefficient [cm ^-1 ] I ₀ : incident light intensity I: transmitted light intensity d: sample thickness [cm] Using carbonate, a calibration curve representing the relationship between the value of the extinction coefficient and the OH weight in a 25 ml solution was determined. This graph is shown in FIG.

From the extinction coefficient of the polycarbonate solution and the calibration curve,
The weight of OH contained in the 25 ml solution was determined, and the weight% of phenolic OH groups was calculated from the ratio of this to the weight of the dissolved polycarbonate.

When the ratio of the phenolic OH group exceeds 0.02% by weight, the coloring becomes easy, and the amount of increase in transmission loss at 120 ° C. becomes large. The preferred ratio of phenolic OH groups is 0.
It is at most 018% by weight, more preferably at most 0.015% by weight.

The sheath material used in the present invention may be any transparent resin having a lower refractive index than that of the core polycarbonate. More preferably, it should have a suitable mechanical strength and adhere to polycarbonate. For example, polymers and copolymers such as fluoroalkyl acrylate, fluoroalkyl methacrylate, and fluoroalkyl-α-fluoroacrylate, copolymers such as vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, and hexafluoropropylene, and polymethyl methacrylate And polymethyl methacrylate, poly-4-methylpentel-1, and the like, and vinylidene fluoride-hexafluoroacetone copolymer described in JP-A-63-142308.

As a method for producing the plastic optical fiber of the present invention, the pellets of the core material and the sheath material are each brought into a molten state in a clean environment, and the core is formed by a special nozzle and two extruders.
It is optimal to use a so-called composite spinning method in which a sheath structure is formed. The sheath is coated to a thickness of about 2/1000 to 300/1000 of the diameter of the core to obtain a bare wire. In order to further increase the heat resistance, the bare wire can be used as a cord by applying several layers of heat-resistant coating such as cross-linked polyethylene, cross-linked vinyl, polypropylene, polyvinylidene fluoride, and nylon.

The thus produced plastic optical fiber of the present invention has a small loss increase in the visible region to the near-infrared region even after long-term use at a high temperature and is very stable.

(Examples) Next, the present invention will be described in more detail with reference to Examples.
The present invention is not limited by these examples. In addition, each physical property value was measured as follows.

(1) Transmission loss Fiber loss spectrometer FP-889 manufactured by Operex Corporation
Was measured by a 12m-2m cutback method.

(2) Melt index Using a melt indexer manufactured by Toyo Seiki Co., Ltd.
It was measured under the conditions of a −1238 test temperature of 230 ° C., a load of 3.8 kg, and a die inner diameter of 2.0955 mm.

Example 1 456 g of bisphenol A of high purity and 9.5 g of p-tert
-Butylphenol was added to 1500 g of filtered pure water, and nitrogen filtered by a filter was blown while stirring to remove oxygen in the reaction tank. Next, 335 g of a 45% aqueous sodium hydroxide solution and 1000 g of dichloromethane were added, and 237 g of high-purity phosgene was blown in over 60 minutes while maintaining the temperature at 25 ° C. After the completion of the phosgene blowing, 0.8 g of triethylamine was added, and the mixture was further stirred for 2 hours to allow the reaction to proceed.

After the completion of the reaction, the dichloromethane solution containing the polycarbonate was sufficiently washed with filtered pure water to thoroughly remove remaining impurities such as salts and alkalis. Thereafter, heptane, which is a poor solvent, was added to reprecipitate the polycarbonate, and a low molecular weight cut was also performed. After the solvent was removed, the mixture was formed into a pellet by an extruder equipped with a vent.

When the ratio of the terminal phenolic OH groups was measured by the TiCl ₄ method, it was 0.005% by weight. The melt index was 5 g / 10 minutes.

Using this polycarbonate as a core and using poly-4-methylpentene-1 for the sheath, an outer diameter of 1000 μm and a thickness of the sheath of 10 μm
A plastic optical fiber bare wire was obtained. In addition to this, commercially available water-crosslinked polyethylene Nippon Unicar Co., Ltd. "SN-15
0 '' is coated so as to have a sheath diameter of 2.2 mm, in a skein state, and put in a water bath at 65 ° C. for 20 hours to cause a crosslinking reaction,
A plastic optical fiber cord was manufactured.

The transmission loss of this code is 500dB / k at the optical wavelength of 770nm.
m, 520 dB / km at 660 nm. This cord was placed in a thermostat at 120 ° C and the transmission loss after 2000 hours was measured.
It was 540 dB / km at 770 nm and 620 dB / km at 660 nm, and was very stable.

Example 2 Commercially available polycarbonate ("Panlite" L-1225,
A low molecular weight component was removed by repeating a purification method in which Teijin Chemicals Ltd.) was dissolved in dichloromethane, reprecipitated in acetone and separated from the solvent several times.

The ratio of phenolic OH groups at the terminals of this polycarbonate was 0.012% by weight, and the melt index was 5 g / 10
Minutes.

Except that this purified polycarbonate was used as the core material,
A plastic optical fiber cord having a core diameter of 1000 μm and a sheath diameter of 2.2 mm was produced in the same manner as in Example 1.

The transmission loss of this code is 650dB / km at 770nm and 660nm.
It was 750 dB / km. This cord was placed in a thermostat at 120 ° C and the transmission loss after 2000 hours was measured.
dB / km, 880dB / km at 660nm, very stable.

Example 3 The ratio of phenolic OH groups of "Iupilon" H4000 (manufactured by Mitsubishi Gas Chemical Co., Ltd.) was measured to be 0.015% by weight.
And the melt index was 14 g / 10 minutes.

Using this polycarbonate as a core material, a plastic optical fiber code was produced in the same manner as in Example 2, and the transmission loss was 670 dB / km at 770 nm and 775 dB / km at 660 nm.
This code was placed in a thermostat at 120 ° C, and the transmission loss after 2000 hours was measured.The result was 720 dB / km at 770 nm and 910 dB / km at 660 nm.
km and stable.

Comparative Example 1 The ratio of the terminal phenolic OH group of a commercially available polycarbonate (“PANLITE” AD-5503, manufactured by Teijin Chemicals Ltd.) was measured to be 0.050% by weight, and the melt index was 16 g / It took 10 minutes.

A plastic optical fiber cord having a bare wire diameter of 1000 μm and a sheath diameter of 2.2 mm was produced in the same manner as in Example 1 except that this polycarbonate was used as a core.

The transmission loss of this code is 930 dB / km at 770 nm and 660 dB.
The transmission loss after heating at 120 ° C for 2000 hours was 1050 dB / km and 660 n at 770 nm.
It increased to 1800dB / km at m.

(Effects of the Invention) The plastic optical fiber of the present invention has a small increase in transmission loss over the visible light region to the near infrared region even when heating is continued at 120 ° C. for 2000 hours, and exhibits extremely excellent long-term heat resistance. . Therefore, the plastic optical fiber of the present invention can be applied to a part that requires long-term heat resistance and stability, such as an automobile engine dome.

[Brief description of the drawings]

FIG. 1 shows a calibration curve used for quantification of terminal phenolic OH groups in the present invention.

Claims (1)

(57) [Claims] 1. A plastic optical fiber in which a polymer mainly composed of polycarbonate is used as a core material and a resin having a lower refractive index than the core material is used as a sheath material, the terminal of the polymer used for the core material is phenolic. The proportion of OH groups is TiCl ₄
A plastic optical fiber characterized in that the amount of OH as determined by the method is 0.02% by weight or less.