JP3504064B2 - Graded-index plastic optical fiber and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gradient index plastic optical fiber that can be used as a large capacity optical information communication medium and a method for manufacturing the same.

[0002]

2. Description of the Related Art Optical fibers can be classified into single-mode fibers and multi-mode fibers according to the number of modes of light to be transmitted, and step index type (SI type) and graded index type (SI type) are used according to the refractive index profile of the fiber. GI type). In addition, there are silica type and plastic type optical fibers depending on the material, and it is possible to obtain plastic optical fibers with a large diameter, although it is inferior to quartz type in terms of transmission loss, and there is a large allowance for axis deviation. It is mainly used in the short-distance field because of its excellent flexibility and easy handling.

Polycarbonate, cyclic polyolefin, maleimide-based polymer and the like are used as materials for such plastic optical fibers, but polymethylmethacrylate is mainly used because of its low transmission loss.
As for the plastic optical fiber, the SI type has already been industrialized, but in recent years, the GI type capable of transmitting information having a larger capacity than the SI type has been developed.

The GI type optical fiber is an optical fiber having a refractive index distribution in which the refractive index continuously decreases from the central part of the fiber toward the outer peripheral part, and is also called a refractive index distribution type optical fiber, which transmits a large amount of information. Suitable for As a method of forming such a refractive index distribution in a plastic optical fiber, a method of continuously changing the blending ratio thereof by using two kinds of polymers having different refractive indexes (JP-A-1-26).
520), a method of continuously changing the copolymerization composition of two kinds of monomers having different refractive indexes after polymerization (JP-A-5-173025 and JP-A-5-173).
No. 026), a method of continuously changing the abundance ratio of the non-polymerizable low molecular weight compound having a higher refractive index than the matrix polymer (WO93 / 08488), and the like.

However, in the method of changing the blending ratio of the two kinds of polymers, some polymers cause phase separation between the polymers to increase scattering loss, and on the other hand, when the glass transition temperature is low, it is practically sufficient. Since it is not possible to obtain excellent heat resistance, it is necessary to combine polymers having good compatibility with each other and high glass transition temperatures, but it is extremely difficult to select such a combination of polymers. . In the method using two kinds of monomers, unless the copolymerization system is a completely random system, microscopic phase separation due to the reactivity ratio of different kinds of monomers occurs and scattering loss becomes large. Unable to get high performance optical fiber.

On the other hand, in the method of changing the abundance ratio of the non-polymerizable low molecular weight compound having a higher refractive index than the matrix polymer, phase separation between polymers and micro phase separation in copolymerization do not occur and scattering loss is small. Therefore, an optical fiber with high transmission performance can be obtained. However, since the low molecular weight compound is contained in the matrix, the optical fiber is plasticized and the heat resistance and mechanical properties due to the glass transition temperature decrease are greatly reduced. There is a problem in that the optical fiber is diffused inside and the refractive index distribution of the optical fiber is disturbed to deteriorate the transmission characteristics.

[0007]

DISCLOSURE OF THE INVENTION An object of the present invention is to use a polymer and a non-polymerizable compound having a high refractive index, which has a low loss, stability over time, and thermal stability. To provide a plastic optical fiber.

[0008]

The present invention provides the following formula [1]:
An optical fiber composed of a matrix polymer composed of a monomer represented by and a non-polymerizable compound having a higher refractive index than the polymer and having a molecular weight of 100 to 1,000, wherein the non-polymerizable compound is a fiber. A graded-index plastic optical fiber characterized by being present in a concentration gradient that decreases continuously from the central portion toward the outer peripheral portion,

[0009]

[Chemical 4]

A polymer of the monomer represented by the above formula [1] and a molecular weight of 100 to 1,0 having a refractive index higher than that of the polymer.
No. 00 non-polymerizable compound is formed into a fiber-shaped spinning solution, and then a part of the non-polymerizable compound is volatilized from the outer periphery of the fiber under heating. And its manufacturing method,

Also, a polymer of the monomer represented by the above formula [1] and a molecular weight of 100 to 100, which has a higher refractive index than the polymer.
Using a multi-layer composite spinning nozzle, a plurality of spinning stock solutions each consisting of 1,000 non-polymerizable compounds and having different composition ratios of the non-polymerizable compounds were used to measure the abundance ratio of the non-polymerizable compound from the center of the fiber toward the outer peripheral portion. A method for producing a graded index plastic optical fiber, characterized in that the particles are discharged in a state of being concentrically laminated so as to decrease, and a non-polymerizable compound is diffused under heating between adjacent layers during or after the discharging. ,It is in.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer constituting the matrix of the plastic optical fiber of the present invention is a polymer comprising a monomer having a 5-membered ring lactone structure represented by the above formula [1]. Examples of the monomer represented by the formula [1] include:
For example, α-methylene-γ-butyrolactone, α-methylene-4,4-dimethyl-γ-butyrolactone, α-methylene-4-ethyl-γ-butyrolactone, α-methylene-4,4-bis (trifluoromethyl)- γ-butyrolactone, α-methylene-4-phenyl-γ-butyrolactone, α-methylene-4-cyclohexyl-γ-butyrolactone and the like can be mentioned. The synthesis of these monomers is
gew. Chem. Ed. Engl, Volume 24, 94
Page (1985), Journal of Organic Synthetic Chemistry, Vol. 39, Vol.
It is carried out by a known method on page 8 (1981) and the like.

The polymer composed of the monomer represented by the above formula [1] has a glass transition temperature of, for example, α-methylene-
γ-butyrolactone homopolymer is 190 ° C., α-methylene-4,4-dimethyl-γ-butyrolactone homopolymer is 180 ° C., α-methylene-4-ethyl-γ-butyrolactone homopolymer is 160 ° C., Even if a non-polymerizable compound is contained in the matrix polymer, the optical fiber is
It maintains a glass transition temperature of 00 ° C or higher and has practically sufficient heat resistance. The polymer may be a homopolymer or copolymer of the monomer represented by the above formula [1], or a blend polymer thereof.

The non-polymerizable compound is a high refractive index non-polymerizable compound having a molecular weight of 100 to 1,000, which has a higher refractive index than the polymer. If the molecular weight is too small, diffusion in the matrix tends to occur excessively and the stability of the refractive index distribution is lacking,
On the other hand, if the molecular weight is too large, diffusion in the matrix is difficult to occur and it becomes difficult to form a suitable refractive index distribution itself.

As such a high refractive index non-polymerizable compound,
Examples thereof include benzoic acid esters such as benzyl benzoate, phthalic acid esters such as diphenyl phthalate, phosphoric acid esters such as triphenyl phosphate, and phosphite esters such as tricresyl phosphite. Those having compatibility with the polymer corresponding to the coalescence are used.

The refractive index distribution in the gradient index plastic optical fiber of the present invention is formed by the presence of the high refractive index non-polymerizable compound in a concentration gradient in which the high refractive index non-polymerizable compound continuously decreases from the central portion of the fiber toward the outer peripheral portion. Has been done. In order to widen the transmission band of the optical fiber, this refractive index distribution is preferably a distribution in which the refractive index in the optical fiber is represented by a quadratic decreasing function from the central part of the fiber toward the outer peripheral part.

The gradient index plastic optical fiber of the present invention can be manufactured by the method described below. That is, (1) a spinning stock solution composed of a polymer of a monomer represented by the above formula [1] and a high-refractive-index non-polymerizable compound is discharged using a spinning nozzle and shaped into a fiber, A method of heating the fiber to volatilize a part of the non-polymerizable compound from the outer peripheral portion of the fiber to reduce the existing ratio of the non-polymerizable compound from the central portion of the fiber toward the outer peripheral portion.

Further, (2) a plurality of spinning dope liquids each consisting of a polymer of the monomer represented by the above formula [1] and a high refractive index non-polymerizable compound, wherein the composition ratio of each non-polymerizable compound is different. , Using a multi-layer composite spinning nozzle, eject in a state of concentrically stacked layers so that the abundance ratio of non-polymerizable compounds decreases from the center of the fiber to the outer peripheral direction, and non-polymerizable between adjacent layers during or after ejection. It is a method of diffusing a compound under heating.

In the methods (1) and (2), the stock solution for spinning may be one prepared by polymerizing the monomer represented by the above formula [1] in the presence of a non-polymerizable compound having a high refractive index. It may be a polymer of a monomer dissolved in a monomer and a high refractive index non-polymerizable compound. When a spinning dope containing a monomer is used, the monomer is polymerized by heat during discharge or by heat or energy rays after discharge. The content of the high refractive index non-polymerizable compound in the spinning dope is preferably 5 to 40% by weight when a single spinning dope is used, and
When using a plurality of spinning dope, it is preferably in the range of 0 to 40% by weight, and when using a plurality of spinning dope, the spinning dope is prepared from the center side in the descending order of the content of the non-polymerizable compound. Place and eject.

In addition, during or after the ejection in the spinning by the method (2), the monomer and the high refractive index non-polymerizable compound are interdiffused between adjacent layers during or after shaping by heating by heating. Further, the monomer is cured by heat or photopolymerization, or by heating, the high refractive index non-polymerizable compound is mutually diffused between adjacent layers during or after shaping. This diffusion of the high refractive index non-polymerizable compound smoothes the concentration gradient of the high refractive index non-polymerizable compound between the layers in the obtained fiber.

Polymerization of the monomer represented by the above formula [1] in the present invention can be carried out by radical polymerization. In the polymerization, a thermal polymerization initiator such as an azo type or peroxide type or a benzophenone type or phenyl ketone is used. It is preferable to use a photopolymerization initiator of a system or the like, and a chain of n-butyl mercaptan, t-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan or the like in order to adjust to a desired molecular weight. A polymerization inhibitor such as a transfer agent or hydroquinone can also be used.

Therefore, in the methods (1) to (3),
When using a spinning stock solution or a mixed solution containing a monomer,
It is preferable to add a heat or photopolymerization initiator, a chain transfer agent, a polymerization inhibitor and the like in advance. Further, as a light source for photopolymerization and curing, a carbon arc lamp, a low pressure mercury lamp,
A high pressure mercury lamp, a chemical lamp, a xenon lamp, a metal halide lamp, a laser beam, etc. are used.

[0023]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 80 parts by weight of α-methylene-γ-butyrolactone, 20 parts by weight of benzyl benzoate and 0.1 part by weight of azobisisobutyronitrile were mixed and the mixture was mixed at 80 ° C.
It was polymerized for 4 hours. Next, this polymer was supplied to a screw type extruder and discharged as a spinning stock solution at 230 ° C. from a circular spinning nozzle to form a strand fiber having a diameter of 1 mm. Subsequently, this fiber was heated at 200 ° C. for 120 minutes to diffuse and volatilize the non-polymerizable compound benzyl benzoate from the outer peripheral side to obtain an optical fiber.

When the refractive index distribution of the optical fiber cross section of the obtained optical fiber was measured by an interphaco interference microscope, it was confirmed that the refractive index continuously decreased from the central portion toward the outer peripheral portion. The refractive index of the part is 1.522,
The refractive index of the outer peripheral portion was 1.506. Moreover, when the transmission characteristics of the obtained optical fiber were measured, the transmission loss was 1
62 dB / km (wavelength 650 nm), transmission band 3.1
It was GHz. This optical fiber is 3
Although it was exposed for 6 months, the transmission loss was 163 dB / km (wavelength 6
50 nm), the transmission band was 3.1 GHz, and the initial performance was maintained.

The transmission loss is measured with a cutback method of 50 m to 5 m and an excitation NA of 0.1. The transmission band is measured with a sampling oscilloscope manufactured by Hamamatsu Photonics and a semiconductor laser TOLD9410 manufactured by Toshiba.
The -3 dB band was obtained by the impulse response method under the conditions of 50 nm, excitation NA = 0.65, and fiber length 100 m.

Example 2 A mixed solution having a composition ratio shown in Table 1 was prepolymerized at 80 ° C. for 2 hours and then 230 at 5 ° C./min.
The temperature was raised to 0 ° C to prepare 5 kinds of spinning dope.

[0028]

[Table 1]

Using a multi-layer composite spinning nozzle in which the slits are arranged concentrically, the spinning dope N is mainly composed of five types of spinning dope.
o. Spinning stock solution No. 1 at the outermost periphery. Stock spinning solution No. 5 Spinning stock solution No. 1 to No. 1 5 was discharged at the discharge radius ratio shown in Table 1, and the length was 1 in an atmosphere of 200 ° C.
The high refractive index non-polymerizable compound benzyl benzoate is diffused between the adjacent layers in the discharge filament by passing through a 50 cm heat-retaining tube, then the refractive index distribution is fixed in the cooling zone, and 2 m / min with the nip roller. The optical fiber having a diameter of 1 mm was obtained by winding at a speed of.

The refractive index distribution of the cross section of the optical fiber thus obtained was measured by an interphaco interference microscope, and it was confirmed that the refractive index continuously decreased from the central portion toward the outer peripheral portion. The refractive index of the part is 1.520,
The refractive index of the outer peripheral portion was 1.503. Moreover, when the transmission characteristics of the obtained optical fiber were measured, the transmission loss was 1
53 dB / km (wavelength 650 nm), transmission band 4.3
It was GHz. This optical fiber is 3
Although it was exposed for 6 months, the transmission loss was 150 dB / km (wavelength 6
50 nm), the transmission band was 4.2 GHz, and the initial performance was maintained.

Example 3 Five kinds of stock solutions for spinning were prepared by kneading and dissolving at 70 ° C. for 2 hours at the composition ratio shown in Table 2.

[0032]

[Table 2]

Using a multi-layer composite spinning nozzle having slits arranged concentrically, five kinds of spinning dope are centered and spinning dope N
o. Spinning stock solution No. 1 at the outermost periphery. Stock spinning solution No. 5 Spinning stock solution No. 1 to No. 1 5 was discharged at a discharge radius ratio shown in Table 2, and then a chemical lamp (manufactured by Ushio Inc., center emission wavelength 350
nm, irradiation intensity 4 mW / cm) is passed through a heat-retaining tube with a length of 1 m that contains α-methylene-4,4-dimethyl-γ-butyrolactone and benzyl benzoate between adjacent layers in the discharge filamentous material. While diffusing, the monomer in the discharged filament was polymerized and hardened to fix the refractive index distribution, and a high pressure mercury lamp (manufactured by Ushio Inc., emission wavelength 365n
m, irradiation intensity 8 mW / cm) to complete the polymerization of the discharged filamentous material and wind it with a nip roller at a speed of 2 m / min to obtain an optical fiber having a diameter of 1 mm.

The refractive index distribution of the cross section of the obtained optical fiber was measured by an interferco interference microscope, and it was confirmed that the refractive index continuously decreased from the central portion toward the outer peripheral portion. The refractive index of the part is 1.518,
The refractive index of the outer peripheral portion was 1.505. Moreover, when the transmission characteristics of the obtained optical fiber were measured, the transmission loss was 1
65 dB / km (wavelength 650 nm), transmission band 4.0
It was GHz. This optical fiber is 3
Although it was exposed for 6 months, the transmission loss was 160 dB / km (wavelength 6
50 nm) and the transmission band was 4.0 GHz.

(Comparative Example 1) In Example 3, poly (α
-Methylene-4,4-dimethyl-γ-butyrolactone)
To poly (methyl methacrylate), α-methylene-
An optical fiber having a diameter of 1 mm was obtained in the same manner as in Example 3 except that methyl methacrylate was used instead of 4,4-dimethyl-γ-butyrolactone.

When the refractive index distribution of the optical fiber cross section of the obtained optical fiber was measured by an interphaco interference microscope, it was confirmed that the refractive index continuously decreased from the central portion toward the outer peripheral portion. The refractive index of the part is 1.521,
The refractive index of the outer peripheral portion was 1.502. Moreover, when the transmission characteristics of the obtained optical fiber were measured, the transmission loss was 1
30 dB / km (wavelength 650 nm), transmission band 2.3
It was GHz. This optical fiber is 3
After exposure for a month, the transmission loss was 129 dB / km (wavelength 650 nm) and the transmission band was 0.8 GHz, showing a remarkable decrease in the transmission band.

[0037]

Industrial Applicability The graded index plastic optical fiber of the present invention is suitable for a large-capacity optical information communication medium with a wide band loss and little loss, and has practically sufficient heat resistance and transmission. It has the characteristics of stability over time and thermal stability.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI G02B 6/18 G02B 6/18 (72) Inventor Kazumi Nakamura 20-1 Miyuki-cho, Otake-shi, Hiroshima Mitsubishi Rayon Co., Ltd. In-lab (72) Inventor Shoji Hayashi 20-1 Miyuki-cho, Otake-shi, Hiroshima Mitsubishi Rayon Co., Ltd. Central Research Laboratory (56) Reference JP-A-8-231648 (JP, A) JP-A-6-186441 (JP, A) JP 5-113511 (JP, A) JP 3-81705 (JP, A) US Patent 2624723 (US, A) International Publication 94/004949 (WO, A1) (58) Field (Int.Cl. ⁷ , DB name) G02B 6/00 G02B 6/10 G02B 6/16-6/22 G02B 6/44

Claims (3)

(57) [Claims] 1. An optical fiber composed of a matrix polymer composed of a monomer represented by the following formula [1] and a non-polymerizable compound having a refractive index higher than that of the polymer and having a molecular weight of 100 to 1,000. In the gradient index plastic optical fiber, the non-polymerizable compound is present in a concentration gradient in which the non-polymerizable compound continuously decreases from the central portion of the fiber toward the outer peripheral portion. [Chemical 1] 2. A polymer of a monomer represented by the following formula [1] and a molecular weight of 100 to 1,0 having a refractive index higher than that of the polymer.
No. 00 non-polymerizable compound is formed into a fiber-shaped spinning solution, and then a part of the non-polymerizable compound is volatilized from the outer periphery of the fiber under heating. And its manufacturing method. [Chemical 2] 3. A polymer of a monomer represented by the following formula [1] and a molecular weight of 100 to 1,0 having a refractive index higher than that of the polymer.
No. 00 non-polymerizable compound and different composition ratios of each non-polymerizable compound are used to reduce the abundance ratio of the non-polymerizable compound from the central part of the fiber toward the outer peripheral part using a multi-layer composite spinning nozzle. As described above, the method of producing a gradient index plastic optical fiber is characterized in that the non-polymerizable compound is ejected in a state of being concentrically laminated, and the non-polymerizable compound is diffused under heating during or after the ejection. [Chemical 3]