JPS6095406A - Light transmitting fiber - Google Patents

Abstract

PURPOSE:To enhance transparency, heat resistance, and flexibility, and to improve adhesion to a core component by using a polymer of fluoroalkyl methacrylate contg. a specified amt. of maleic anhydride for the sheath component of a light transmitting fiber using PMMA or its deriv. as a core component. CONSTITUTION:A light transmitting fiber consists of a core component of a polymer composed essentially of methyl methacrylate (MMA) monomer units, and a sheath component of a polymer composed essentially of fluoroalkyl methacrylate monomer units contg. 2-40wt% maleic anhydride monomer units. The polymer composed essentially of MMA monomer units also contains, as monomer units, methacrylate of >=8C alicyclic hydrocarbon groups, such as bornyl, fenchyl, or adamantly methacrylate, in an amt. of 8-40wt%. As the sheath component, fluoroalkyl methacrylate, 2,2,2-trifluoroethyl, and 1,1,1,3,3,3-hexafluoro-2- propyl methacrylates, etc. are used. Such a light transmitting fiber has good adhesion between the core and the sheath, and superior heat resistance and flexibility, and it can be used for motor cars, airplanes, robots, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical transmission fiber having a core-sheath structure and having excellent heat resistance and flexibility.

Optical transmission fibers are conventionally manufactured using glass-based materials as a base material, and are used as optical signal transmission media for measurement control between devices and within devices.
It is widely used for data transmission, medical purposes, decoration, and image transmission. However, optical transmission fibers based on glass-based materials have the disadvantage of poor flexibility unless the fibers are made with a thin inner diameter, are easily broken, have a high specific gravity, and are expensive, including connectors. For these reasons, various attempts have been recently made to make them from plastic.

The major characteristics of using plastic are that it is lightweight, and even fibers with a thick inner diameter are strong and flexible.Therefore, high apertures and large diameters are possible, and it is easy to combine with light receiving and emitting elements. It has excellent operability.

A common method for manufacturing such optical transmission fibers using plastic is to use a plastic with a large refractive index and good light transmission as a core component, and a plastic with a smaller refractive index than the core material.
In addition, the fiber has a core-sheath structure in which the sheath component is transparent plastic. This method transmits light by reflecting it at the core-sheath interface, and the larger the difference in refractive index between the plastics that make up the core and sheath, the better the light transmission properties.

Amorphous materials are preferable as plastics with high light transmittance, and polymethyl methacrylate and polystyrene are attracting attention from an industrial perspective (for example,
Publication No. 8978).

When manufacturing optical transmission fibers, it is basically important to increase the difference in refractive index between the core and sheath, but it is also important to increase the adhesion state at the interface between the core and sheath, as well as the possibility of dust, bubbles, or polymers. The influence of contamination with foreign substances and the physical, mechanical, and thermal properties of the polymer forming the optical transmission fiber are also important factors.

In this sense, a combination of a polystyrene resin and a polymethyl methacrylate resin proposed in Japanese Patent Publication No. 48-8978, or a combination of a polymethyl methacrylate resin and a certain type of fluorine-containing polymethacrylate resin is considered. Transmission fibers are noteworthy. However, polystyrene has the disadvantage that the transmitted light has a yellowish tinge, its optical transmission properties are particularly poor in the short wavelength region, and it is easily degraded by light, making the resin with poor flexibility even worse. However, it also has the problem that the adhesion between the sheath and the core component is not good. In addition, fluorine-containing polymethacrylate resins as shown in the same publication generally have poorer heat resistance than the core component, and as the temperature rises, light guide loss increases, and the reliability as an optical signal medium is insufficient. There are drawbacks. In addition, the fluorine-containing alcohol, which is the raw material for these polymers, requires advanced technology to synthesize and purify, and is also expensive, resulting in an economic disadvantage.

(5) As a method to improve these drawbacks, optical transmission fibers containing a copolymer of vinylidene fluoride and hexafluoropropylene as a sheath component (Japanese Patent Publication No. 4B-8978) and fluoride fibers having a specific copolymer composition are proposed. Optical transmission fibers whose sheath component is a resin that is a copolymer of vinylidene and tetrafluoroethylene (Japanese Patent Publication No. 5B-21660, Japanese Patent Application Laid-Open No. 52-154645, and Japanese Patent Publication No. 54-807)
No. 58) has been proposed. However, the copolymer of vinylidene fluoride and hexafluoropropylene is sticky and has insufficient adhesion to the core component methacrylic resin, insufficient interfacial reflectance, and thermal decomposition. It has drawbacks such as being easy to mold and difficult to melt mold, and has extremely little practical value.

In addition, the resin, which is a copolymer consisting of vinylidene fluoride and tetrafluoroethylene, has a low refractive index and mechanical toughness such as bending resistance and abrasion resistance, but this composition retains some crystallinity. However, due to heat treatment, crystallization progresses, and (6) transparency is insufficient, reducing light transmission, and adhesion at the interface between the core and sheath components is insufficient, resulting in increased light reflection loss. There are still some points that require improvement. In addition, vinylidene fluoride has insufficient thermal stability, and copolymers containing 60 to 8Qmo1% of vinylidene fluoride have a narrow processing temperature range when coating the core component using the melt composite spinning method. There are still many points that need improvement.

In view of the current situation, the inventors of the present invention conducted extensive studies on a sheath component that has excellent heat resistance, good workability, flexibility, transparency, and excellent adhesion between the core component and the core component, and as a result, the present invention was developed. Reached.

That is, the present invention provides an optical transmission fiber having a core-sheath structure in which the core component is a polymer mainly composed of methyl methacrylate. The present invention provides a light transmission fiber characterized in that the sheath component is a polymer mainly composed of acid fluoroalkyl.

The features of the present invention can be summarized in the following points.

1) It is possible to perform melt @Il composite spinning of the sheath component and the core component, and the sheath component can be stably formed.

2) The sheath component has a low refractive index and good adhesion with the core component, and has excellent bending strength and heat resistance, so it has excellent light transmission properties and increases reliability. 3) The core component contains a fat with a carbon number of 8 or more. When Nisder methacrylate having a cyclic hydrocarbon group is used, heat resistance is significantly improved.

The polymer mainly composed of methyl methacrylate used as the core component in the present invention is a mono or copolymer of methyl methacrylate containing at least 60% or more repeating units of methyl methacrylate, and includes ethyl methacrylate, methacrylic acid, etc. Copolymers containing propyl, butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, or methacrylic esters having an alicyclic hydrocarbon group having 8 or more carbon atoms in the ester moiety, and lθ
Copolymers of methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate and the like are useful.

Among these, a copolymer containing 70% or more of methyl methacrylate units is particularly preferred as a core component because it is highly pure, extremely transparent, and easily available.

The methacrylic acid ester having an alicyclic hydrocarbon group having 8 or more carbon atoms in the ester moiety is obtained by esterifying methacrylic acid or more preferably its acid chloride with an alicyclic hydrocarbon mono-ol of the formula ROH. created by.

Alicyclic hydrocarbons/monols include 1-adamantanol, 2-adamantanol, 8-methyl-1-adamantanol, 8,5-dimethyl-1-adamantanol, 8-ethyladamantanol, 8-methyl-5 -ethyl-l-adamantanol, 8,5.8-triethyl-
1-adamantanol and 8,5-dimethyl-8-ethyl-1-adamantanol, octahydro-4,7-
Menznoinden-5-ol, octahydro-4,7
-men, tanoindene (9) -1-ylmethanol, p-menthanol 8, p-menthanol-2,8-hydroxy-2゜6,6-drimethyl-bicyclo(g,i,i)hebutane, 8,7 .7-Dolimethyl-4-hydroxy-bicyclo(4,1,0)hebutane, borneol, 2-methylcamphanol, fenthyl alcohol, J-menthanol, 2,2゜5-
Examples include alicyclic hydrocarbons/monols such as trimethylcyclohexanol, and copolymers made from corresponding methacrylic acid esters. The reason why it is limited to alicyclic hydrocarbon groups is that aromatic hydrocarbon groups cause large light guide loss in optical transmission fibers, which limits their use as optical signal transmission media.

Among the alicyclic hydrocarbon groups having 8 or more carbon atoms, preferably the alicyclic hydrocarbon groups having 10 to 18 carbon atoms have a particularly high contribution rate to improving heat resistance.

Among these methacrylic acid esters, particularly preferred are 1-adamantyl methacrylate, 2-adamantyl methacrylate, and 3,5- methacrylate.
dimethyl-1-adamantyl, bornyl methacrylate,
p-menthane methacrylate, 2-methyl camphor methacrylate, fentyl methacrylate, methacrylate
Examples include polymers or copolymers of 1-menthyl and 2,2.5-trimethylcyclohexane methacrylate. Since the polymer made of the methacrylic acid ester exhibits a high refractive index, it has particularly favorable properties as a light transmission fiber.

The component copolymerized with these methacrylic esters is selected from alkyl acrylates or alkyl methacrylates having an alkyl group having 1 to 6 carbon atoms,
For example, methyl, ethyl, n-propyl, n-butyl,
Alkyl acrylates or alkyl methacrylates having an alkyl group such as cyclohexyl or the like can be effectively used.

The sheath component, which is the most important element constituting the present invention, is a polymer mainly composed of fluoroalkyl methacrylate containing 2 to 40% by weight of maleic anhydride. The preferred maleic anhydride content is 5-85%. More preferably, it is 10 to 80%. The proportion of maleic anhydride is 2
If it is less than 40%, it has excellent ITI flexibility but little contribution to improving heat resistance, while if it exceeds 40%, it has excellent heat resistance but has poor workability and insufficient flexibility. Undesirable.

Among the fluoroalkyl methacrylates, those whose homopolymer has a softening temperature of about 70° C. or higher and a refractive index of 1.42 or lower are preferred. Preferred fluoroalkyl methacrylates used in the present invention include 2°2,2-trifluoroethyl methacrylate and l methacrylate.

1.1,8,8.8-hexafluoro-2-propyl,
1.1-diethyl-2゜2.8,4,4, methacrylate
4-hexafluoro-1-butyl, l-propyl-2,2,8°4.4.4-hexafluoro-1 methacrylate
-butyl, 1,1-dimethyl-8-trifluoromethyl-2,2,4,4,4-pentafluorobutyl methacrylate, 2-trifluoromethyl-2,8-methacrylate,
8,8-tetrafluoropropyl, methacrylic acid 1.1
Examples include -dimethyl-2,2,8°8-tetrafluoropropyl, perfluoroisopropyl methacrylate, and 2-trifluoromethyl-8,8,8-1-lifluoropropyl methacrylate.

Furthermore, in the polymer mainly composed of fluoroalkyl methacrylate, which is the sheath component of the present invention, an alkyl acrylate or alkyl methacrylate component having an alkyl group having 1 to 4 carbon atoms or a fluorinated alkyl group is added by copolymerization. It can be included. In order to maintain heat resistance and refractive index, it is preferable that the amount of these copolymerized components is set at a minimum amount not exceeding 40% of the total amount of the polymer forming the shell and sheath components.

The polymer of the carrier component of the present invention is produced according to the known copolymerization method of methyl methacrylate and maleic anhydride (eg, D, C, Blackley).

(1B) H, W, Melville, Macromolecular Chemistry Makromol, chem.
1B/19, 16 (1956)).

In order to obtain a uniform composition of maleic anhydride, it is polymerized by a known sequential addition method or the like. In the case of the core component polymer, the manufacturing method for the sheath component polymer has no effect on optical transmission properties, so make sure that foreign substances such as goslin are not mixed in, and if necessary, use the offshore method. The sheath component polymer may be produced by removing foreign substances such as dust.

The core component polymer of the present invention can be produced by conventionally known methods such as suspension polymerization and bulk polymerization. However, in the suspension polymerization method, since a large amount of water is used, foreign substances contained therein are likely to be mixed into the polymer, and there is also a possibility that foreign substances may be mixed in during the dehydration process. Therefore, a desirable method is to carry out the manufacturing step of the core component polymer and the manufacturing step of the optical transmission device in a continuous process, and
There is a method for producing a core component polymer in two steps (14): a continuous bulk polymerization step at high temperature and a subsequent continuous separation step of volatiles mainly containing residual unreacted monomers. Alternatively, a production method in which the core component is bulk polymerized, and then the core component and sheath component are formed from the obtained polymer by a double extrusion method is also desirable.

Examples of radical polymerization initiators in these polymerization methods include 2,2-azo-bis(isobutyronitrile), l,
l-azobis(cyclohexanecarbonitrile), 2.
2-azobis(2゜4-dimethylvaleronitrile), azobisisobutanol diacetate, azotert-
Azo compounds such as butane, di-tert-butyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, di-tert-butyl perphthalate, di-tart-butyl peracetate, di-t
Examples include organic peroxides such as ert-amyl peroxide.

Further, in order to control the molecular weight, tert-butyl, n-butyl, n-octyl, n-dodecyl mercaptan, etc. are added as a chain transfer agent to the polymerization system in an amount of about 1 mol % or less based on the monomers.

As described above, the present invention greatly expands the applicable temperature range of conventional plastic optical transmission fibers when a specific polymer is used for the core component and the sheath component in optical transmission fibers having a core-sheath structure. The present invention provides an optical transmission fiber with excellent heat resistance and flexibility in practical use, and its industrial value is extremely high. Since the practical temperature can be 110° C. or higher, it can be applied to, for example, automobiles, ships, aircraft, or robots. Furthermore, the range of application will be expanded by relaxing temperature conditions for on-premises and intra-building communications.

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

The light guide loss in the examples was measured using a diffraction grating spectrometer with a non-containing tungsten lamp as the light source.
The output intensity of the measured light transmission delicate and reference light transmission [a] at the wavelength of is read with a silicon photodiode, and the light intensity at the entrance and exit of the optical transmission fiber with different fiber lengths L (K,) is calculated by the following formula. The light guide loss α was calculated by measuring IO and I, respectively. .

This formula shows that the smaller the α value, the better the optical transmission performance.

In addition, the heat resistance test was completed by heating the obtained optical transmission fiber for a predetermined period of time, and then measuring and comparing the light guide loss at the initial stage and after heating.

In addition, flexibility was measured by preparing several types of rods with different outer diameters, wrapping optical transmission fibers around them, and determining the radius (r) at which they would begin to break. Therefore, the smaller the value of r, the greater the flexibility.

Moreover, parts in the examples indicate parts by weight.

Example 1 Bornyl methacrylate purified by vacuum distillation 80%
, 69% methyl methacrylate, 1% methyl acrylate, and 0.025% n-dodecyl mercaptan, 2
．． 2-azobis(2,,4-dimethylvaleronitrile)
A monocatalyst mixture to which 0.10% was added was prepared in the absence of oxygen, sent to a reaction tank maintained at 150°C, and prepolymerized for 8 hours. Then, the polymerization was completed by sending it into a screw conveyor maintained at 220°C for a residence time of 2 hours,
A polymer having a claimed intrinsic viscosity [η) of 0.90 and a refractive index of 1.49 was obtained at 25°C. Further, this polymer was fed to a two-stage vented extruder heated to 266°C, and the polymer in the form of a strand with a diameter of 1! Fluoro-8,8,8-trifluoropropyl-maleic anhydride-methyl methacrylate-methyl acrylate copolymer [copolymer composition; 75
:15:8:2 (%), refractive index 1.40.25°C, intrinsic viscosity [η): 0.70) prepared with ethyl acetate solution (18) was melt-coated as a sheath component to form a core-sheath structure. I got a strand of. The core-sheath polymer blending ratio was set at 90:10. 25℃ and 7
The light guide loss at 0°C was measured to be 200 dB/m and 200 d at a wavelength of 650 nm, respectively.
It was B/h. After heat-treating this optical transmission fiber at 110°C for 6 hours, the light guide loss was measured again, and the result was 220 d.
B/h, showing excellent heat resistance. Furthermore, when the flexibility was measured, it was possible to bend up to 5 wIL.

Examples 2 to 8 Optical transmission fibers (0,85
~0.75 pus φ) was obtained.

The light guide loss, heat resistance, and flexibility of the obtained optical transmission fiber were measured in the same manner as in Example 1, and the results are shown in Table 1. As shown in Table 1, all of the optical transmission fibers had excellent physical properties.

(19) Comparative Example 1 Methyltetrafluoropropyl-methyl acrylate copolymer [copolymer composition i95:5 (94, refractive index 1.89)
．． Intrinsic viscosity measured with ethyl acetate at 25°C [η]: 0.77
) was melt-spun in the same manner as in Example 1 to obtain an optical transmission fiber having a core-sheath structure and having a diameter of 0.85 mm.

When the light guide loss at 25° C. was measured for a wavelength of 650 nm, it was 200 dB/IIJ. This is 9
When heat treated at 0° C. for 2 hours, it showed a light guide loss of 540 dB/mu.

Comparative Example 2 2-trifluoromethyl methacrylate-8,8,8-trifluoropropyl-methyl acrylate copolymer [copolymer composition: 98] was used as the sheath component polymer for the same core component as in Example 8. :2 (foundation), refractive index 1.40.25℃,
Using the intrinsic viscosity [η): 0.69) determined with ethyl acetate, melt spinning was performed in the same manner as in Example 1 to obtain an optical transmission fiber having a core-sheath structure and a diameter of about 0.85711111 mm. When the flexibility was measured, it was possible to bend up to 5 mm. When the light guide loss was measured at 25°C and 70°C for a wavelength of 6501 m, it was 260 d, respectively.
b/&, 270 dB/yx. This is 100°
When heated at C for 6 hours, 1000 dB/K
It showed a light guide loss of s+ or more. When the flexibility was measured, it was found to be extremely brittle.

Comparative Example 8 A core component polymer was obtained from a monomer mixture consisting of 1% bornyl methacrylate, 96% methyl methacrylate, and 8% methyl acrylate as core components by the same operation as in Example 1, and then The same polymer as 1 was used as a sheath component and melt-spun by the same operation to obtain a light transmission fiber having a core-sheath structure and having a diameter of about 0.851 rrIn.

When the flexibility was measured, it was possible to bend up to 5 Min. When the light guide loss was measured at 258C and 70℃ for a wavelength of 650nm, it was 850 db respectively.
/Km, 500 dB/b. This was heat treated at 105°C for 7 hours, at llo'c for 3 hours, at 120°C for 8 hours, and at 150°C for 8 hours.
It exhibited a light guide loss of 1 or more at 0 dB/0, and its flexibility was poor.

Comparative Example 4 A light transmission fiber was obtained in the same manner as Comparative Example 1 except that benzyl methacrylate was used as the core component. This is 100
Tokoro treated at ℃ for 2 hours, 1000 dB/+cs+
The light guide loss was above and the heat resistance was poor.

Comparative Example 8 A light transmitting device was obtained in the same manner as Comparative Example 1 except that 0-octyl methacrylate was used as the core component. This is 1
When processed at 00'C for 2 hours, 1000 dB/h
The light guide loss was above and the heat resistance was poor.

(28) Comparative Example 4 After obtaining a core component polymer from a monomer mixture consisting of 50% nomenthyl methacrylate, 47% methyl methacrylate, and 8% methyl acrylate as core components by the same operation as in Example 1. Using the same polymer mainly composed of fluoroalkyl methacrylate as in Example 1 as the sheath component, a light transmitting device having a core-sheath structure and having a diameter of 0.45 m was obtained by the same operation. When we measured the flexibility, it was 200W+
It was extremely fragile and could not be bent. (i 5 Q
When the light guide loss at 25° C. at a wavelength of nm was measured, it was 400 dB/h. 1 at 180℃
When heat treated for 2 hours, the light guide loss was 420 dB/b, indicating excellent heat resistance.

(24 completed)

Claims (1)

[Scope of Claims] (1) In an optical transmission fiber having a core-sheath structure in which the core component is a polymer mainly composed of methyl methacrylate, a fluoroalkyl methacrylate containing 2 to 40% by weight of maleic anhydride is used. Optical transmission fiber with excellent heat resistance and flexibility, characterized by having a polymer as the main component as a sheath component. (2) A patent claim in which the polymer mainly composed of methyl methacrylate is a polymer mainly composed of methyl methacrylate containing 8 to 40% by weight of a methacrylic ester having an alicyclic hydrocarbon group having 8 or more carbon atoms. The optical transmission fiber according to item 1. (8) Methacrylic acid esters having an alicyclic hydrocarbon group having 8 or more carbon atoms in the ester moiety include bornyl methacrylate, fentyl methacrylate, and methacrylic acid! - Menthyl, methacrylic pongee. (4) Fluoroalkyl methacrylate is methacrylic acid 212, 2-)lifluoroethyl, methacrylic acid 1,
1,1,8,8.8-hexafluoro-2-propyl,
1.1-diethyl-2,2,8,4,4, methacrylate
4-Hexafluoro-1-butyl, 1-brobyl-2,2,8,4,4,4-hexafluoro-1 methacrylate
-butyl, 1,1-dimethyl-8-trifluoromethyl-2゜2.4,4,4-pentafluorobutyl methacrylate, 2-trifluoromethyl-2,8゜8.8-tetrafluoropropyl methacrylate , methacrylic acid 1.1
-dimethyl-2,2,8,8-tetrafluoropropyl, perfluoroisopropyl methacrylate, or 2-trifluoromethyl-8,8,8-trifluoropropyl methacrylate. transmission fiber.