JPH09243834A - Refractive index distribution type plastic optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a refractive index distribution type optical fiber having excellent stability against heat in the distribution of refractive index by using at least one kind selected from triphenyl phosphate, tricresyl phosphate and diphenyl phthalate as a nonpolymerizable compd. to give the density gradation. SOLUTION: This fiber consists of a polymer which forms a transparent matrix and a nonpolymerizable compd. and the fiber has distribution of refractive index obtd. by making density gradation of the nonpolymerizable compd. between the center to the peripheral part of the fiber. The polymer which constitutes the matrix is not limited as far as it can form a transparent matrix, and for example, methylmethacrylate and ethylmethacrylate can be used. As for the nonpolymerizable compd., at least one compd. selected from triphenyl phosphate, tricresyl phosphate and diphenyl phthalate is used. The nonpolymerizable compd. has solubility with the polymer of the matrix and gives the density gradation.

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 excellent in heat resistance stability of the gradient index.

[0002]

2. Description of the Related Art In order for a plastic optical fiber to have a refractive index distribution in the fiber cross section, it must be composed of two or more kinds of polymers having different refractive indexes or composed of a polymer and a non-polymerizable low molecular weight material. is there. However, in a plastic optical fiber composed of two or more polymers having different refractive indices, the scattering loss due to phase separation between the polymers becomes large, and it is extremely difficult to obtain an optical fiber with low loss. is there. On the other hand, a plastic optical fiber composed of a polymer and a non-polymerizable low molecular weight substance has a refractive index distribution with a concentration gradient of the non-polymerizable low molecular weight substance, and since there is no scattering loss due to phase separation, low loss Optical fiber can be obtained (WO93 / 08488 gazette, Japanese Patent Laid-Open No. Hei 6
-186441, JP-A-6-186442, JP-A-7-27928).

As a non-polymerizable low molecular weight compound in a gradient index plastic optical fiber using such a polymer and a non-polymerizable low molecular weight compound, for example, Japanese Patent Publication No. 55-1888.
No. 2 discloses ethylene diacetate, dimethyl phthalate and dibutyl phthalate, WO 93/08488 discloses bromobenzene, benzyl benzoate and butyl benzyl phthalate, and JP 7-27928 discloses sebacic acid. Dibutyl is indicated. However, the refractive index distribution type plastic optical fiber obtained by using the non-polymerizable low molecular weight compound disclosed therein has a problem that the refractive index distribution is likely to change when heated, and the heat resistance stability of the refractive index distribution is poor. Have a point.

[0004]

SUMMARY OF THE INVENTION The present invention solves the problems of the conventional gradient index plastic optical fiber by using a selected specific non-polymerizable low molecular weight compound. An object of the invention is to provide a gradient index plastic optical fiber having excellent heat resistance stability of the gradient index.

[0005]

The present invention comprises a transparent matrix polymer and a non-polymerizable compound,
In the gradient index optical fiber in which the concentration gradient of the non-polymerizable compound is formed between the central part and the outer peripheral part of the fiber, the non-polymerizable compound is selected from the group of triphenyl phosphate, tricresyl phosphate and diphenyl phthalate. A graded index plastic optical fiber characterized in that it is at least one.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The gradient index plastic optical fiber of the present invention comprises a transparent matrix polymer and a non-polymerizable compound, and the non-polymerizable compound is provided between the central portion and the outer peripheral portion of the fiber. Since the concentration gradient is formed, it has a refractive index distribution.

The polymer constituting the matrix of the plastic optical fiber of the present invention is not particularly limited as long as it can form a transparent matrix. For example, methyl methacrylate, ethyl methacrylate, methacrylic acid (n
-, I-) propyl, methacrylic acid (n-, i-, s
-, T-) butyl, cyclohexyl methacrylate, benzyl methacrylate, phenyl methacrylate, bornyl methacrylate, adamantyl methacrylate, tricyclodecyl methacrylate, dicyclopentanyl methacrylate,
2,2,2-Trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 2,2,3,3 methacrylate 4,4,4-hexafluorobutyl, 1-trifluoromethyl methacrylate
2,2,2-trifluoroethyl, methacrylic acid 1H,
Homopolymers or copolymers of methacrylic acid esters such as 1H, 5H-octafluoropentyl or blend polymers thereof, methyl group as a substituent, ethyl group,
(N-, i-) propyl group, (n-, i-, s-, t
-) Aliphatic N having a butyl group, a cyclohexyl group, etc.
Examples thereof include homopolymers or copolymers of substituted maleimide monomers or blend polymers thereof, homopolymers or copolymers of styrene and its derivatives, or blend polymers thereof.

The non-polymerizable compound in the plastic optical fiber of the present invention must be at least one selected from the group consisting of triphenyl phosphate, tricresyl phosphate and diphenyl phthalate. These non-polymerizable compounds in the present invention are compatible with the matrix polymer and can provide a concentration gradient.

Further, since the non-polymerizable compound in the plastic optical fiber of the present invention has a large refractive index, the concentration of the non-polymerizable compound is increased in the central portion of the optical fiber, and the non-polymerizable compound is introduced from the central portion to the outer peripheral portion of the optical fiber. It is particularly preferred that a concentration gradient is formed which progressively decreases towards the content of non-polymerizable compounds.

The plastic optical fiber containing the non-polymerizable compound of the present invention does not have a flat refractive index distribution even when it is exposed to a temperature close to the glass transition temperature of the polymer of the matrix for a long time. The heat resistance stability of the refractive index distribution is excellent.

The optical fiber of the present invention can be manufactured by a known method including a batch method and a continuous method exemplified below. That is, as a batch method, a cylindrical container of polymer is filled with a monomer and a non-polymerizable compound of the polymer constituting the container, and while being held horizontally and rotated, by heating or light irradiation from the outside of the container. It is possible to employ a method in which the monomers are sequentially polymerized from the outside to be integrated with the polymer constituting the container, and at the same time, the non-polymerizable compound is diffused and moved to the central portion to form a rod, and the obtained rod is stretched. Further, as a continuous system, a low polymerization polymer containing a non-polymerizable compound and a high polymerization polymer not containing a non-polymerizable compound,
With a high degree of polymerization polymer containing no non-polymerizable compound on the outside,
A method in which composite spinning is performed and a non-polymerizable compound inside is heated and diffused can also be adopted.

[0012]

The present invention will be described below in more detail with reference to examples.

(Embodiment 1) Length 600 mm, inner diameter 17.
Methyl methacrylate 112 g, benzoyl peroxide 0.56 g, n-butyl mercaptan 35 in a 6 mm glass tube.
After filling with 0 μl and sealing the upper end, it was kept horizontal, heated at 70 ° C. for 4 hours while rotating at 3000 rpm, then stopped rotating and heated at 90 ° C. for 20 hours to polymerize and consist of polymethylmethacrylate. A cylindrical container was produced. Seal one end of this polymethylmethacrylate container,
Methyl methacrylate 48 g, non-polymerizable compound triphenyl phosphate 12 g, di-t-butyl peroxide 54
After filling up with μL and 160 μL of n-lauryl mercaptan and sealing the other end, hold horizontally and hold at 10 rp.
While rotating at m, heat at 95 ° C for 24 hours, then stop rotation and heat at 110 ° C for 48 hours to polymerize to give an outer diameter of 17.6.
A mm rod was obtained.

This rod was attached vertically to a rod feed apparatus, and was heated and melted in a cylindrical heating furnace at 220 ° C. while being drawn at a constant speed and wound and melt-spun to obtain an optical fiber having a diameter of 0.75 mm. The refractive index distribution of the fiber cross section of the obtained optical fiber was measured, and FIG.
As shown in, the refractive index gradually decreased from the central portion toward the outer peripheral portion. When the transmission characteristics of the obtained optical fiber at 100 m length were evaluated, the transmission loss was found to be 65 nm.
15.6 dB at 0 nm, transmission band 3.7 GHz
And had good performance as a gradient index plastic optical fiber. In addition, the obtained optical fiber is
A heating test was carried out by placing it in an oven at 5 ° C. and the refractive index distribution after 3000 hours was measured. As a result, as shown in FIG. 2, the initial refractive index distribution was retained.

Example 2 A polymethylmethacrylate container manufactured in the same manner as in Example 1 was used, and methylmethacrylate 48 was added to the polymethylmethacrylate container.
g, 12 g of non-polymerizable compound tricresyl phosphate, di-
After filling 54 μl of t-butyl peroxide and 160 μl of n-lauryl mercaptan and sealing the inlet end, it was kept horizontal, heated at 95 ° C. for 24 hours while rotating at 10 rpm, and then stopped rotating at 110 ° C. Four
Polymerization was carried out by heating for 8 hours to obtain a rod having an outer diameter of 17.6 mm.

This rod was attached vertically to a rod feed device, and was melted by spinning at a constant speed while being heated and melted in a cylindrical heating furnace at 220 ° C., and was melt-spun to obtain an optical fiber having a diameter of 0.75 mm. The refractive index distribution of the fiber cross section of the obtained optical fiber was measured, and FIG.
As shown in, the refractive index gradually decreased from the central portion toward the outer peripheral portion. When the transmission characteristics of the obtained optical fiber at 100 m length were evaluated, the transmission loss was found to be 65 nm.
16.3 dB at 0 nm, transmission band 3.1 GHz
And had good performance as a gradient index plastic optical fiber. In addition, the obtained optical fiber is
A heating test was carried out by placing it in an oven at 5 ° C., and the refractive index distribution after 3000 hours was measured. As a result, as shown in FIG. 4, the initial refractive index distribution was retained.

(Example 3) A polymethylmethacrylate container manufactured in the same manner as in Example 1 was used, and methylmethacrylate 48 was added to the polymethylmethacrylate container.
g, non-polymerizable compound diphenyl phthalate 12 g, di-
After filling 54 μl of t-butyl peroxide and 160 μl of n-lauryl mercaptan and sealing the inlet end, it was kept horizontal, heated at 95 ° C. for 24 hours while rotating at 10 rpm, and then stopped rotating at 110 ° C. Four
Polymerization was carried out by heating for 8 hours to obtain a rod having an outer diameter of 17.6 mm.

This rod was attached vertically to a rod feed apparatus, was melted by heating at 220 ° C. in a cylindrical heating furnace at a constant speed while being melted by heating, and was melt-spun by winding to obtain an optical fiber having a diameter of 0.75 mm. When the refractive index distribution in the fiber cross section of the obtained optical fiber was measured,
As shown in, the refractive index gradually decreased from the central portion toward the outer peripheral portion. When the transmission characteristics of the obtained optical fiber at 100 m length were evaluated, the transmission loss was found to be 65 nm.
14.5 dB at 0 nm, transmission band 2.3 GHz
And had good performance as a gradient index plastic optical fiber. In addition, the obtained optical fiber is
When it was placed in an oven at 5 ° C., a heating test was performed, and the refractive index distribution after 3000 hours was measured, the change in the initial refractive index distribution was slight, as shown in FIG.

(Comparative Example 1) A polymethylmethacrylate container manufactured in the same manner as in Example 1 was used, and methylmethacrylate 48 was added to the polymethylmethacrylate container.
g, non-polymerizable compound benzyl benzoate 12 g, di-t
-Butyl peroxide (54 μl) and n-lauryl mercaptan (160 μl) were charged, the inlet end was sealed, and then held horizontally, while rotating at 10 rpm.
Heat at 5 ° C for 24 hours, then stop spinning and 110 ° C for 48 hours.
Polymerization was carried out by heating for a time to obtain a rod having an outer diameter of 17.6 mm.

This rod was attached vertically to a rod feed device, was melted by heating at 220 ° C. in a cylindrical heating furnace while being melted and drawn at a constant speed, and was melt-spun to obtain an optical fiber having a diameter of 0.75 mm. When the refractive index distribution of the fiber cross section of the obtained optical fiber was measured,
As shown in, the refractive index gradually decreased from the central portion toward the outer peripheral portion. When the transmission characteristics of the obtained optical fiber at 100 m length were evaluated, the transmission loss was found to be 65 nm.
13.7 dB at 0 nm, transmission band 1.9 GHz
And had good performance as a gradient index plastic optical fiber. However, the obtained optical fiber was put in an oven at 85 ° C. and subjected to a heating test.
When the refractive index distribution after 00 hours was measured,
As shown in, the initial refractive index distribution changed greatly.

(Comparative Example 2) A container made of polymethylmethacrylate prepared in the same manner as in Example 1 was used, and methylmethacrylate 48 was placed in the container made of polymethylmethacrylate.
g, non-polymerizable compound benzyl-n-butyl phthalate 1
2 g, 54 μl of di-t-butyl peroxide,
Fill 160 μl of n-lauryl mercaptan,
After sealing the inlet end, keep it horizontal, rotate at 10 rpm and heat at 95 ° C for 24 hours, then stop rotation 1
Polymerization was carried out by heating at 10 ° C. for 48 hours to obtain a rod having an outer diameter of 17.6 mm.

This rod was attached vertically to a rod feed device, was melted by heating at 220 ° C. in a cylindrical heating furnace at a constant speed while being melted by heating, and was melt-spun to obtain an optical fiber having a diameter of 0.75 mm. When the refractive index distribution of the fiber cross section of the obtained optical fiber was measured, FIG.
As shown in, the refractive index gradually decreased from the central portion toward the outer peripheral portion. When the transmission characteristics of the obtained optical fiber at 100 m length were evaluated, the transmission loss was found to be 65 nm.
17.2 dB at 0 nm, transmission band 2.4 GHz
And had good performance as a gradient index plastic optical fiber. However, the obtained optical fiber was put in an oven at 85 ° C. and subjected to a heating test.
When the refractive index distribution after 00 hours was measured, the results are shown in FIG.
As shown in 0, the initial refractive index distribution was largely changed.

[0023]

The optical fiber of the present invention is superior in the heat resistance stability of the refractive index distribution to the conventionally known refractive index distribution type plastic optical fiber, and the reliability of the transmission characteristics of the optical fiber is high. Is more improved.

[Brief description of drawings]

FIG. 1 is a refractive index distribution diagram of a fiber cross section of an optical fiber obtained in Example 1.

FIG. 2 is a refractive index distribution diagram of a cross section of the optical fiber obtained in Example 1 after a heating test.

3 is a refractive index distribution diagram of a fiber cross section of the optical fiber obtained in Example 2. FIG.

FIG. 4 is a refractive index distribution diagram of a cross section of a fiber after a heating test of the optical fiber obtained in Example 2.

5 is a refractive index distribution diagram of a fiber cross section of the optical fiber obtained in Example 3. FIG.

FIG. 6 is a refractive index distribution chart of a cross section of the optical fiber obtained in Example 3 after a heating test.

7 is a refractive index distribution diagram of a fiber cross section of the optical fiber obtained in Comparative Example 1. FIG.

FIG. 8 is a refractive index distribution diagram of a cross section of the optical fiber obtained in Comparative Example 1 after a heating test.

9 is a refractive index distribution diagram of a fiber cross section of the optical fiber obtained in Comparative Example 2. FIG.

FIG. 10 is a refractive index distribution diagram of a cross section of the optical fiber obtained in Comparative Example 2 after a heating test.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location G02B 6/18 G02B 6/18 (72) Inventor Kikue Irie 20-1 Miyukicho, Otake City, Hiroshima Prefecture Central Research Laboratory, Mitsubishi Rayon Co., Ltd.

Claims (1)

[Claims] 1. A gradient index optical fiber comprising a transparent matrix polymer and a non-polymerizable compound, wherein a concentration gradient of the non-polymerizable compound is formed between the central part and the outer peripheral part of the fiber, A gradient index plastic optical fiber, wherein the non-polymerizable compound is at least one selected from the group consisting of triphenyl phosphate, tricresyl phosphate and diphenyl phthalate.