JPH04358103A - Plastic optical fiber - Google Patents

Abstract

PURPOSE:To improve performances of not only heat resistance but light transmittability and mechanical characteristics as well and to allow stable production by improving the fluorinated polymer to be used as a sheath component to improve the boundary adhesion to a core component. CONSTITUTION:The plastic optical fiber is constituted by using a polymer essentially consisting of methyl methacrylate as the core component and a compsn. which consists essentially of the fluorinated polymer having >=70 deg.C glass transition temp. and is compounded with 0.02 to 5wt.% graft polymer disposed with the polymers identical to or analogous with two kinds of these polymers respectively in either of trunk or branch polymer chains as the sheath component.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic optical fiber that has excellent light transmittance, heat resistance, and mechanical properties and can be stably manufactured.

0002

2. Description of the Related Art Plastic optical fibers are composed of two types of polymers: a core component and a sheath component. Polymers with excellent transparency and good weather resistance, such as polymethyl methacrylate, are generally used as the core component. On the other hand, the sheath component is used to trap light inside the core.
It needs to have a lower refractive index than the core component, and fluorine-containing polymers are widely used.

As the fluorine-containing polymer, vinylidene fluoride/tetrafluoroethylene copolymer (Japanese Patent Publication No. 6
Vinylidene fluoride copolymers such as hexafluoroacetone/vinylidene fluoride copolymer (Japanese Patent Application Laid-Open No. 61-22305) are generally used.

These vinylidene fluoride copolymers are
Since it has good compatibility with a polymer whose main component is methyl methacrylate, an optical fiber using it as a sheath component has good interfacial adhesion with the core component and good mechanical properties. However, all of these vinylidene fluoride copolymers are crystalline polymers and have a problem of poor transparency. Furthermore, since the glass transition temperature is low, optical fibers using it as a sheath component have a low heat resistance of about 70° C., and their uses are limited.

[0005] Therefore, an optical fiber using the following fluorine-containing polymer as a sheath component, which has high transparency and a high glass transition temperature, has been proposed.

[0006] a: Copolymer of fluoroalkyl methacrylate and methyl methacrylate (Japanese Patent Publication No. 43-8
No. 978, Japanese Unexamined Patent Publication No. 62-265606), b:
α-Fluoroacrylate copolymer (JP-A-59-2
27908), c: imidization reaction products such as a and b above (Japanese Patent Laid-Open Publication No. 6
1-121005, JP-A-61-246703), or acid anhydride (JP-A-60-184211)
, d: cyclic fluoropolymer (JP-A-63-261204
No., Japanese Unexamined Patent Publication No. 63-302303).

These fluorine-containing polymers have excellent transparency and a high glass transition temperature compared to vinylidene fluoride copolymers, but have good compatibility with polymers whose main component is methyl methacrylate. do not have. Therefore, while optical fibers using these as sheath components have superior heat resistance compared to optical fibers that use conventional vinylidene fluoride copolymers as sheath components, they do not have sufficient interfacial adhesion with the core component. There are problems with poor translucency, mechanical properties, etc.

[0008]

[Problem to be Solved by the Invention] The main purpose of the present invention is to
By improving the sheath component, which is mainly composed of a fluorine-containing polymer with a high glass transition temperature, so that it has excellent interfacial adhesion with the core component, it not only has heat resistance but also has excellent translucency and mechanical properties. It is an object of the present invention to provide a plastic optical fiber that has excellent performance such as characteristics and can be manufactured stably.

[0009]

[Means for Solving the Problems] In order to achieve this object, the plastic optical fiber of the present invention is made of a polymer (A) containing 60% by weight or more of methyl methacrylate units (hereinafter referred to as methyl methacrylate units). An optical fiber having a core component made of a polymer (A)) and a sheath component made of a polymer having a lower refractive index than the core component, wherein the sheath component has a glass transition temperature of 70°C or higher. Fluorine-containing polymer (B
), one of the trunk and branch polymer chains is composed of a polymer (C1) containing 60% by weight or more of methyl methacrylate units, and the other is a fluorine-containing polymer (C2)
0.02 to 5% by weight of graft polymer (C) consisting of
It is characterized by comprising a fluorine-containing polymer composition containing.

That is, the present invention adds polymers that are the same or similar to the core component and the sheath component to the fluorine-containing polymer (B) having a high glass transition temperature, such as the above-mentioned a to d, which have been proposed as the sheath component. A graft polymer (C) in which 0.02
By using a composition containing a small amount of ~5% by weight as the sheath component, the problems of the prior art could be solved.

[0011] Here, the graft polymer refers to a comb-shaped branched copolymer having a structure in which one polymer is grafted onto another polymer, and the trunk polymer chain and branch polymer chains are different types of polymers. do. Therefore, this graft polymer is a copolymer with a so-called crosslinked structure branched into a network with polyfunctional monomers, etc., or a trunk polymer chain and a branch polymer chain are distinguished by copolymerization of polyfunctional monomers. This is different from branched copolymers, which are similar copolymers that cannot be used.

The methyl methacrylate polymer (A) constituting the core component is a polymer containing 60% by weight or more of methyl methacrylate units, such as methyl methacrylate units.
methacrylate-based copolymers, which are mainly composed of methyl methacrylate and copolymerized with (meth)acrylic acid esters, (meth)acrylic acid, substituted styrene, N-substituted maleimide, etc. Alternatively, modified polymers such as glutaric anhydride, glutarimide, etc., which are obtained by polymerizing these materials, may be used.

Examples of (meth)acrylic acid esters include methyl acrylate, ethyl methacrylate, butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, and phenyl methacrylate. Examples include ester, bornyl methacrylate, and adamantyl methacrylate.

Examples of the substituted styrene include styrene, methylstyrene, and α-methylstyrene.

Examples of the N-substituent in the N-substituted maleimide include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, t-butyl, hexyl, and cyclohexyl.

A plurality of these copolymerization components may be used, and a small amount of components other than these may also be used. Further, a stabilizer such as a thermal oxidative deterioration inhibitor may be included in an amount that does not adversely affect the translucency.

Fluorine-containing polymer (which is the main component of the sheath component)
B) is a fluorine-containing polymer with a glass transition temperature of 70°C or higher, such as the polymers a to d (below) mentioned above; The fluorine-containing polymer is not limited to this as long as it is transparent and desired to improve compatibility with the methyl methacrylate polymer (A) as the core component.

a. Copolymer of fluoroalkyl methacrylate and methyl methacrylate b. α-fluoroacrylate copolymer c. a, b above
Imidization reaction products such as acid anhydrides d. Among the cyclic fluoropolymers, formula 1

[0019]

[Chemical 2]

(However, R1 is H or F, R2 is CH3 or F, m is 1 or 2, and p is an integer from 0 to 10.)
60 to 100% by weight of meth)acrylate units, and
A polymer containing 0 to 40% by weight of methyl methacrylate units as a (co)polymerization component, or a modified polymer such as glutaric anhydride or glutarimide obtained by polymerizing these polymers are effective.

[0021] A small amount of graft polymer is added to the sheath component.
(C) is a polymer (C1) in which either the trunk or branch polymer chains contain 60% by weight or more of methyl methacrylate units.
(hereinafter abbreviated as methyl methacrylate polymer (C1)), and the other is a fluorine-containing polymer (C2), and the desired effect can be obtained regardless of which one is the trunk or branch polymer chain. be able to.

The methyl methacrylate polymer (C1) forming the monopolymer chain of the graft polymer (C) can be freely selected within the range of the methyl methacrylate polymer (A) forming the core component. do it. However, in order to sufficiently improve the interfacial adhesion with the methyl methacrylate polymer (A) as the core component, it is necessary to
It is preferable to select a polymer that is the same or similar to the type of polymer (A), or a polymer with good compatibility.

Similarly, the fluorine-containing polymer (C2) forming the monopolymerized chain of the graft polymer (C) may be selected freely within the range of the fluorine-containing polymer (B) forming the sheath component. Among them, polymers containing (fluoro)alkyl (meth)acrylate units represented by the above formula 1, or glutaric anhydride obtained by polymerizing them,
Preferably, it is a modified polymer such as glutarimide, and further, 40 to 100% by weight of the (fluoro)alkyl (meth)acrylate unit and 0 to 60% by weight of the methyl methacrylate unit are (co)polymerized. It is preferable to use a polymer contained as a component or a modified polymer such as glutaric anhydride or glutarimide obtained by polymeric reaction with the polymer. Furthermore, it is preferable to select a polymer that is the same or similar to the fluorine-containing polymer (B) used for the sheath component, or a polymer that has good compatibility.

The desired effect can be obtained by blending this graft polymer (C) in an amount of 0.02 to 5% by weight with respect to the sheath component composition;
~3% by weight is preferred. If it is less than 0.02% by weight, it is difficult to obtain sufficient effects. On the other hand, if it exceeds 5% by weight, not only will the cost increase, but the excellent properties of the fluorine-containing polymer (B), which is the main component of the sheath component, will be inhibited, and the optical fiber will become cloudy and the translucency of the optical fiber will be impaired. It is not suitable as a sheath component as it may reduce the

The weight ratio of the trunk/branch polymer chains of the graft polymer (C) is preferably in the range of 1/4 to 4/1. Outside this range, the effect of improving the compatibility with the fluorine-containing polymer (B), which is the main component of the sheath component, or the interfacial adhesion with the methyl methacrylate polymer (A), which is the core component, is insufficient. becomes.

Although it is possible to improve the adhesion between the core and sheath interface by adding a small amount of this graft polymer (C) to the core component, the cleanliness of the core component is impaired and the transparency is reduced. It is practically difficult to use because the optical property deteriorates.

[0027] In general, for the production of graft polymers,
A. A method of grafting a branch polymer chain polymer onto a trunk polymer chain polymer; B. A method of polymerizing a monomer of a branch polymer chain onto a polymer of a main polymer chain, C. There are methods such as polymerizing a branch polymer chain polymer (macromonomer) having a reactive group at the end and a trunk polymer chain monomer, but in order to produce this graft polymer (C), The method C is most preferred because it is difficult to produce a homopolymer consisting only of chains or branched polymer chains, and the length (molecular weight) and number of branched polymer chains can be easily controlled.

Graft polymer (C) thus obtained
, chips or flakes of fluorine-containing polymer (B
) to form a polymer composition, which is used as the sheath component, and the core component methyl methacrylate polymer (A
) may be melted and co-extruded to produce an optical fiber.

This optical fiber further contains polyethylene, polypropylene or copolymers and blends thereof, olefinic polymers containing organic silane groups, ethylene-vinyl acetate, polyvinyl chloride, polyvinylidene fluoride, and nylon resin. It can be coated with resin such as polyester resin, nylon elastomer, polyester elastomer, or urethane to form a cord.

It is also possible to melt and extrude only the core component and then fuse the sheath component around the core component in a temperature range equal to or higher than the glass transition temperature of the sheath component to form a sheet. Alternatively, a multicore die may be used to extrude into a sea-island structure in which the core component forms an island and the sheath component forms a sea.

[0031]

[Function] In the present invention, by adding a small amount of a specific graft polymer (C) as a modifier to the conventional fluorine-containing polymer (B) having a high glass transition temperature in the sheath component, This method was able to solve the problems of the prior art.

That is, the fluorine-containing polymer (B) as the sheath component is the methyl methacrylate polymer (B) used as the core component.
Although the interfacial adhesion with A) is not good, it has excellent properties such as high transparency and a high glass transition temperature. However, even if the fluorine-containing polymer (B) is the main component, a polymer (C1) that is the same as or similar to the methyl methacrylate polymer (A), and a polymer that is the same or similar to the fluorine-containing polymer (B) A graft polymer (C) in which a polymer (C2) is arranged on either the trunk or branch polymer chains.
Surprisingly, the above-mentioned drawbacks of the fluorine-containing polymer (B) can be compensated for by forming an optical fiber with a polymer composition containing a small amount of 0.02 to 5% by weight as a sheath component. This makes it possible to obtain an optical fiber that has excellent properties such as heat resistance, translucency, and mechanical properties, and can be manufactured stably.

[0033]

EXAMPLES The abbreviations and chemical compositions of monomers and macromonomers used in the following examples are as follows.

(1) Fluoroalkyl methacrylate
G 5FM:

[0035]

[C3]

(2) Fluoroalkyl methacrylate
G 4FM:

[0037]

[C4]

(3) PMMA macromonomer (product number AA-6 manufactured by Toagosei Kagaku Kogyo Co., Ltd., number average molecular weight 6,000):

[0039]

[C5]

An example of the method for synthesizing the graft polymer (C) is shown below.

Reference Example 1 PMMA macromonomer 35 parts by weight 5FM
30 parts by weight 4FM
15 parts by weight Methyl methacrylate 20 parts by weight Azobisisobutyronitrile 0.01 parts by weight n
-Butyl mercaptan 0.0
05 parts by weight benzotrifluoride 1
00 parts by weight was placed in a glass ampoule, and after removing dissolved oxygen, the tube was sealed and heated at 60°C for 16 hours and then at 100°C for 8 hours.
Polymerization was completed by heating for an hour. The polymer mixture was diluted with benzotrifluoride and reprecipitated into methanol,
The precipitate was vacuum dried at 100 DEG C. for 48 hours to obtain a graft polymer in which the trunk polymer chain was made of a fluorine-containing polymer and the branch polymer chains were made of polymethyl methacrylate.

Reference Example 2 The charging composition was PMMA macromonomer 65 parts by weight 5FM
15 parts by weight 4FM
10 parts by weight Methyl methacrylate 10 parts by weight Azobisisobutyronitrile 0.01 parts by weight n
-Butyl mercaptan 0.0
05 parts by weight benzotrifluoride 1
A polymer was obtained in the same manner as in Reference Example 1 except that the amount was 00 parts by weight.

Reference Example 3 The charging composition was PMMA macromonomer.
35 parts by weight
Pentafluoropropyl α-fluoroacrylate
55 parts by weight Methyl α-fluoroacrylate
10 parts by weight
Azobisisobutyronitrile
0.01 parts by weight n
-Butyl mercaptan
0.005 parts by weight
benzotrifluoride
A polymer was obtained in the same manner as in Reference Example 1 except that the amount was 100 parts by weight.

Reference Example 4 The charging composition was PMMA macromonomer.
10 parts by weight
Pentafluoropropyl α-fluoroacrylate
75 parts by weight Methyl α-fluoroacrylate
15 parts by weight
Azobisisobutyronitrile
0.01 parts by weight n
-Butyl mercaptan
0.005 parts by weight
benzotrifluoride
A polymer was obtained in the same manner as in Reference Example 1 except that the amount was 100 parts by weight.

The present invention will now be explained in more detail with reference to Examples using the graft polymers obtained in Reference Examples 1 to 4 above.

The optical fibers were evaluated as follows.

The light transmittance was measured by the usual cutback method and evaluated by the loss value at 650 nm.

[0048] Heat resistance is 10m test length, 90% in oven.
After heating at ℃ for 500 hours, the amount of emitted light was measured when a red LED was used as the light source, and evaluated by the light amount retention rate determined by comparing the amount of emitted light with the value of the amount of emitted light of an untreated product.

The bending properties were evaluated by continuously bending 180 degrees with a bending radius of 5 mm under a load of 700 g, measuring the number of times until breakage five times, and using the average value.

[0050] The manufacturing stability of the optical fiber was also evaluated based on the variation range of the average wire diameter.

Example 1 The graft polymer of Reference Example 1 was mixed with 5FM/4FM/methyl methacrylate copolymer (copolymerization ratio (wt%): 5
0/20/30, refractive index 1.41) and 0.3% by weight. This is used as a sheath component, and polymethyl methacrylate (100%, refractive index 1.49) is used as a core component, and 240 The composite was spun by melt coextrusion at ℃, and then stretched twice to obtain an optical fiber.

The outer diameter of the obtained optical fiber was 1000μ,
The thickness of the sheath component was 10μ.

[0053] Also, the diameter variation range of the optical fiber is 18
μ, translucency is 128dB/km, heat resistance is light intensity retention rate 9
8%, and the bending property was 1230 times at break.

Example 2 An optical fiber was obtained in the same manner as in Example 1, except that the content of the graft polymer of Reference Example 1 relative to the total sheath component was 1.0% by weight.

The diameter variation range of the obtained optical fiber was 19μ.
, translucency is 127dB/km, heat resistance is light intensity retention rate 98
%, and the bending properties were broken 1310 times.

Example 3 An optical fiber was obtained in the same manner as in Example 1, except that the content of the graft polymer of Reference Example 2 relative to the total sheath component was 1.0% by weight.

The diameter variation range of the obtained optical fiber was 20μ.
, translucency is 126dB/km, heat resistance is light intensity retention rate 99
%, and the bending properties were broken 1430 times.

Comparative Example 1 An optical fiber was obtained in the same manner as in Example 1, except that no graft polymer was blended.

The diameter variation range of the obtained optical fiber was 20μ.
, translucency is 135dB/km, heat resistance is light intensity retention rate 97
%, and the bending properties were broken 860 times.

Comparative Example 2 An optical fiber was obtained in the same manner as in Example 1, except that the content of the graft polymer in Reference Example 1 relative to the total sheath component was 10% by weight.

The diameter variation width of the obtained optical fiber was 23μ.
, translucency is 268dB/km, heat resistance is light intensity retention rate 96
%, and the bending properties were broken 1610 times.

Comparative Example 3 The sheath component was vinylidene fluoride/tetrafluoroethylene copolymer (copolymerization ratio (weight %): 80/20, refractive index 1
．． An optical fiber was obtained in the same manner as in Example 1 except that only 40) was used.

The diameter variation range of the obtained optical fiber was 14μ.
, Translucency is 135dB/km, Heat resistance is light intensity retention rate 45
%, and the bending properties were 1880 times at break.

Example 4 The graft polymer of Reference Example 3 was mixed with pentafluoropropyl α-fluoroacrylate/methyl α-fluoroacrylate copolymer (copolymerization ratio (weight %): 80/20,
An optical fiber was obtained in the same manner as in Example 1, except that 1.0% by weight of the refractive index (1.39) was mixed.

The diameter variation width of the obtained optical fiber was 17μ.
, Translucency is 200dB/km, Heat resistance is light intensity retention rate 10
0%, and the bending property was 1330 times at break.

Comparative Example 4 An optical fiber was obtained in the same manner as in Example 4, except that no graft polymer was blended.

The diameter variation range of the obtained optical fiber was 18μ.
, Translucency is 212dB/km, Heat resistance is light intensity retention rate 99
%, and the bending properties were broken 760 times.

Comparative Example 5 An optical fiber was obtained in the same manner as in Example 4, except that the content of the graft polymer of Reference Example 4 relative to the total sheath component was 1.0% by weight.

The diameter variation width of the obtained optical fiber was 18μ.
, translucency is 210dB/km, heat resistance is light intensity retention rate 99
%, and the bending properties were broken 800 times.

Example 5 A sheath component was prepared by mixing 2.0% by weight of the graft polymer of Reference Example 3 with the pentafluoropropyl α-fluoroacrylate/methyl α-fluoroacrylate copolymer. Example 1 was carried out in the same manner as in Example 1, except that methyl methacrylate/N-isopropyl maleimide copolymer (copolymerization ratio (wt%): 70/30, refractive index 1.50) was used as the core component. Obtained optical fiber.

The diameter variation width of the obtained optical fiber was 22μ.
, Translucency is 251dB/km, Heat resistance is light intensity retention rate 10
3%, and the bending property was 1380 times at break.

Comparative Example 6 An optical fiber was obtained in the same manner as in Example 5, except that no graft polymer was blended.

The diameter variation width of the obtained optical fiber was 20μ
, translucency is 269dB/km, heat resistance is light intensity retention rate 10
1%, and the bending property was 820 times at break.

[0074]

[Effects of the Invention] Compared to conventional optical fibers whose sheath component is a fluorine-containing polymer (B) that has a high glass transition temperature and poor compatibility with the core component, the optical fiber of the present invention has excellent heat resistance. In addition, the interfacial adhesion between the core component and the sheath component is improved, mechanical properties such as translucency and bending properties are improved, and stable production is possible.

Claims (3)

[Claims] 1. An optical fiber having a core component made of a polymer (A) containing 60% by weight or more of methyl methacrylate units, and a sheath component made of a polymer having a refractive index lower than that of the core component. , the sheath component has a glass transition temperature of 7
The main component is a fluorine-containing polymer (B) with a temperature of 0°C or higher, and one of the trunk and branch polymer chains is composed of a polymer (C1) containing 60% by weight or more of methyl methacrylate units, and the other is A plastic optical fiber comprising a fluorine-containing polymer composition containing 0.02 to 5% by weight of a graft polymer (C) consisting of a fluorine-containing polymer (C2). 2. The fluorine-containing polymer (B) which constitutes the main component of the sheath component has the formula 1: (wherein R1 is H or F, R2 is CH3 or F, m is 1 or 2, and n represents an integer from 0 to 10.) Contains 60 to 100% by weight of (fluoro)alkyl (meth)acrylate units and 0 to 40% by weight of methyl methacrylate units as (co)polymerization components. 2. The plastic optical fiber according to claim 1, wherein the plastic optical fiber is a polymer of 3. The fluorine-containing polymer (C2) constituting the polymer chain of the graft polymer contains 40 to 1 (fluoro)alkyl (meth)acrylate unit represented by the formula 1.
00% by weight and 0 to 6 methyl methacrylate units
2. The plastic optical fiber according to claim 1, wherein the plastic optical fiber is a polymer containing 0% by weight as a (co)polymerization component.