JPH08146235A - Manufacture of graded-index fiber for macromolecular material - Google Patents

Abstract

PURPOSE: To provide a continuous refraction factor distribution by extruding a composite monofilament from a solution of polymer material containing two kinds of monomars having a different refraction factor, and diffusing the monomars in a diffusion zone. CONSTITUTION: A material feed tank 10 contains a solution composed of a polymer material A and at least one kind of monomer B, and another material feed tank 12 contains a solution composed of a polymer material D and at least one kind of monomer C. A double-layered composite monofilament 24 is extruded from the orifice of a forming die 22 and fed to a sealed diffusion zone 26. The monomars in the outer and inner layers are diffused in directions opposite to each other during travel within the diffusion zone 26 over a certain time, thereby generating an effect for forming a continuous refraction factor distribution on the composite monofilament 24. Thereafter, the composite monofilament 24 is fed to a curing zone 30 and cured therein. Then, the composite monofilament 24 is taken out with a takeout roll 34 via a roller 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a graded index fiber (hereinafter sometimes referred to simply as "fiber") by an extrusion process, and more specifically, it contains two monomers having different refractive indexes. A method for producing a graded index fiber by extruding a polymer material solution through a concentric mold so that monomers diffuse into each other in a diffusion region to form a polymer material composite monofilament having a continuous refractive index distribution. Regarding

[0002]

2. Description of the Related Art An optical fiber is basically composed of an outer layer called a cladding and an inner layer called a core. The refractive index of the core should be slightly higher than that of the cladding in order for a ray to be transmitted from the high index region to the low index region for total internal reflection and for the ray to be continuously transmitted through the medium. I have to

Optical fibers can generally be divided into two groups: step index fibers and graded index fibers. In a step-index fiber, the refractive index of the core and the refractive index of the cladding change abruptly, and thus when the light beam is transmitted by such a fiber, it travels in multiple modes with different and different velocities, resulting in a signal. It introduces distortion and eventually its bandwidth must be severely limited. To eliminate the above drawbacks, so-called single mode optical fibers have been developed. Single-mode optical fibers have a very small core diameter, only a few micrometers, so that only one beam of light can enter the core, and therefore the times at which the rays reach their intended spots are matched. Moreover, in the single mode optical fiber, there is no diffusion problem caused by other modes, so that the transmission band can be wide. However, it is not easy to get an effective coupling because the core is so small. Therefore, graded index fibers were developed to overcome the above problems.

A graded index fiber has a continuous refractive index distribution from the surface layer to the center of the fiber. The refractive index distribution is in the shape of a parabolic curve. In a graded index fiber, the further the area is from the center in the radial direction, the smaller its index of refraction, and the velocity of the light beam transmitted through the medium is inversely proportional to the index of refraction. The rays that leave
It will return to the central axis by continuous total internal reflection. on the other hand,
A ray traveling along the central axis travels in a medium with a higher refractive index, so it travels at a slower speed and consequently arrives at the intended point at the same time as the ray returned away from the central axis. become. Therefore, the diffusion problem described above is eliminated. Further, since the optical fiber of this system has a larger core diameter, no coupling problem is observed.

An optical fiber made of glass or quartz and having a continuous refractive index distribution from its surface layer toward the center is disclosed in Japanese Patent Laid-Open No. 47-816 and US Pat.
053204, 4163654, 4227271, 51
No. 86236,5206180. However, this type of optical fiber is made by the ion exchange or sol-gel method, and therefore the production rate is very low and the cost is very high. On the other hand, an optical fiber made of glass or crystal has the problems of lacking flexibility and poor workability.

Others have proposed a method of manufacturing an optical fiber having a continuous refractive index distribution from the surface layer of the optical fiber toward the center, from a polymer material. One such method is ion implantation polymerization in which the concentration of metal ions is continuously changed from the column center to the surface layer so that a polymer optical fiber having a continuous refractive index distribution from the surface layer to the center is obtained. A synthetic resin fiber is manufactured by a technique. Such a method is disclosed in Japanese Patent Laid-Open No. 4
No. 7-26913. As another method, a method of manufacturing an optical fiber from a mixture of two or more transparent polymeric resin materials having different refractive indexes has been proposed. After special solvent treatment, a part of the resin mixture is dissolved to obtain an optical fiber. This technique is disclosed in Japanese Patent Laid-Open No. 47-28059. In addition, in the method disclosed in Japanese Unexamined Patent Publication No. 54-30301, a polymer having a continuous refractive index distribution from the fiber surface layer to its center is used by using two monomers having different refractive indexes. It teaches polymerization methods to form materials. In yet another method, a method of diffusing the monomer in the surface layer of the block copolymer so that the content of the monomer in the block copolymer is continuously distributed from the surface layer to the center of the block copolymer was disclosed. . Then, a polymerization reaction is carried out,
An optical fiber having a continuous refractive index distribution is produced. These techniques are disclosed in Japanese Patent Laid-Open Nos. 52-5857 and 56-3752.
1 and 57-29682. It should be noted that all of the above disclosed methods and techniques are carried out in non-continuous batch operations.

In order to overcome the deficiency of the discontinuous production process, the continuous production method is disclosed in Japanese Patent Laid-Open Nos. 1-1896021 and 1-25.
3704, 2-16505 and 2-233104. In this technique, polymeric material and monomer are mixed in a mixing tank and heated until the polymeric material dissolves in the monomer and is uniformly mixed. Then, the composite monofilament is extruded from the mold and sent to the gas evaporator. Gas is fed into the evaporator so that the monomer evaporates from the composite monofilament surface. In this way, a composite monofilament in which the concentration of the monomer is continuously distributed is formed. After the curing treatment, a polymer material composite monofilament having a continuous refractive index distribution from the surface layer to the center is obtained.

[0008]

The above-mentioned method has several drawbacks: for example, the diffusion takes a long time (therefore, the production time is long and the production speed is low), and the optimum production conditions are not satisfied. Difficult to choose and lack of reproducibility. These problems must be resolved before the method is applied to the production floor.

[0009]

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a method of making a graded index fiber from a polymeric material having a continuous index profile from the surface of the fiber to its center.

Another object of the present invention is to provide a practical manufacturable process for producing graded index fibers from polymeric materials having a continuous refractive index profile in the fiber.

A further object of the present invention is to provide a method capable of producing a graded index fiber having a continuous refractive index distribution from the surface layer of the fiber to the center thereof from a polymer material at a high production rate.

Still another object of the present invention is to provide a method capable of producing a graded index fiber having a continuous refractive index distribution from the fiber surface layer to the center thereof from a polymer material with a high level of reproducibility in a continuous process. To provide.

[0013]

According to the present invention, there is provided a method for producing a graded index fiber having a continuous refractive index distribution from a surface layer of a fiber toward its center in a continuous production process from a polymer material.

According to the method of the present invention, extruding a composite monofilament from a solution of a polymeric material containing two monomers having different refractive indices, and allowing the monomers to react with each other before the composite monofilament is cured. A continuous manufacturing method is provided by diffusing in a diffusive region so that they diffuse one another.

According to the present invention, the above graded index fiber having a high optical transparency can be produced in a continuous process.

The present invention discloses a method for producing a graded index fiber having a continuous refractive index distribution from the surface layer of the fiber toward the center of the fiber in a continuous production process from a polymer material.

In the present invention, the first mixture of the polymeric material A and the monomer B which is the solvent of the polymeric material A, or the polymeric material A and the monomer which is the solvent of the polymeric material A And a second mixture of the polymer material D and a monomer C different from the monomer B contained in the first mixture are concentric with each other. Through the mold of 2
Extruded into multilayer composite monofilaments. The separate monomers diffuse in the diffusion region of the composite monofilament until the two monomers diffuse into each other. Then, the composite monofilament is cured.

The polymer material A or polymer material D used in the present invention is polymethylmethacrylate, or methylmethacrylate and other monomers such as ethyl methacrylate, n-propyl methacrylate and methacrylic acid. It is a copolymer with isopropyl, t-butyl methacrylate, cyclohexyl methacrylate, fluoroalkyl methacrylate, methyl 2-hydroxymethacrylate, ethyl 2-phenoxymethacrylate, glyceryl methacrylate, benzyl methacrylate, phenyl methacrylate. . Polymer materials are methyl methacrylate and methyl acrylate,
It may be a copolymer with an acrylate such as ethyl acrylate, propyl acrylate or fluoroalkyl acrylate. Further, the polymer material may be a copolymer of methyl methacrylate and methacrylic acid such as acrylic acid.

Monomer B and Monomer C used in the present invention
Is methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, fluoroalkyl methacrylate, 2-hydroxymethyl methacrylate, 2-Phenoxyethyl methacrylate, glaryl methacrylate, and acrylic acid type monomers such as methyl acrylate, ethyl acrylate, propyl acrylate or fluoroalkyl acrylate may be included.

To carry out the invention, a first mixture of polymeric material A of methyl methacrylate and a monomer B and a second mixture of polymeric material D of methyl methacrylate and a monomer C are used.
A mixture of is created. During preparation, a heat-activated curing agent or typical UV-activated curing agent is added to the mixture.
The content of monomer B or monomer C in the mixture is between about 10 and about 80 weight percent of the total mixture, preferably between about 30 and about 80 weight percent, and more preferably between about 40 and about 40 weight percent. The range is between 70 weight percent. Frequently used heat-activated hardeners are peroxide type hardeners, while UV-activated hardeners are benzophenone and 1-hydroxycyclohexyl phenyl ketone.

In order to increase the storage stability of the mixture of the present invention and prevent the viscosity change when the mixture forms filaments, that is, thermal polymerization, an inhibitor of thermal polymerization may be added to the mixture. If you add a thermal polymerization inhibitor, for example, 100 ℃
Even at temperatures of, no such thermal polymerization occurs.

In the present invention, when two mixtures of polymeric material A / monomer B and polymeric material D / monomer C are made, the viscosity of the resulting mixture is about 10 ² to 10 ^5.
It is a range between Poise. When the viscosity is below 10 ² poise, the composite monofilaments are frequently cut, making it difficult to extrude the aforementioned filaments. When the viscosity is higher than 10 ⁵ poise, the extrusion treatment of the composite monofilament is difficult in practice.

In the next processing step, two different mixtures are extruded through concentric molds to form a composite monofilament having inner and outer layers of different materials. The extrusion process is performed according to the following standard industry practice. After the extrusion treatment, the monomer B and the monomer C diffuse into each other through the diffusion region which is the boundary between the inner and outer layers. The extruded composite monofilament is then cured by either heat activated or UV activated means to complete the process.

In the composite monofilament made according to the present invention, the volume ratio of the inner and outer layers of the composite monofilament extruded through the concentric mold is between about 1: 1 and about 1: 100, with the above-mentioned inner and outer layers being preferred. The volume ratio is between about 1: 1 and about 1:10, and the more preferred volume ratio of the inner and outer layers is between about 1: 1 and about 1: 5.

As an additional processing step, during the diffusion of the two monomers of the composite monofilament, the diffusion zone may be heated in a conventional manner, if desired, to further facilitate diffusion. However, such heating should not cause any further polymerization of the composite monofilament.

By subjecting the above filaments to UV irradiation or heat treatment, the curing treatment of the composite monofilament may be accelerated, but it is not always necessary. Suitable irradiation sources are, for example, carbon arc lamps, high-pressure mercury lamps, ultra-high pressure mercury lamps, low-pressure mercury lamps, electrodeless lamps, xenon lamps or laser sources used at wavelengths between 150 nm and 600 nm.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A description will now be given with reference to FIG. 1 which shows an overview of the apparatus used in this invention. The material supply tank 10 contains a solution of the polymer material A and at least one monomer B, and the material supply tank 12 contains the solution of the polymer material D and at least one monomer C. To be The heating devices 14 and 16 are used to promote the dissolution of the polymeric material A and the polymeric material D in the monomer B and the monomer C. The solution is normally heated to a predetermined temperature above room temperature. Constant volume pumps 18 and 20 are used to pump the two mixtures into the concentric mold 22 at a predetermined flow rate. The double layer composite monofilament 24 is formed by the molding die 22.
Extruded from the orifice (not shown) in the closed diffusion zone 2
Sent to 6. While traveling through the diffusion zone 26 for a period of time, the monomers in the outer layer and the monomers in the inner layer diffuse with each other, producing the effect of a continuous refractive index profile on the filament. The composite monofilament 24 is then sent to the cure zone 30 where it is cured. The composite monofilament 24 is then removed by the unload roll 34 through the roller 32.

Other objects, features and benefits of the present invention will be apparent in view of the specification and the accompanying drawings (FIG. 1) and the accompanying drawing (FIG. 2) which is a diagram showing the refractive index profile of graded index fibers. Let's be

Example 1 The first mixture used in the inner layer (ie, core) was 57 parts by weight of methyl methacrylate, 28 parts by weight of benzyl methacrylate monomer, 14 parts by weight of methyl methacrylate monomer,
1-Hydroxycyclohexyl phenyl ketone 0.5
And 0.1 parts by weight of hydroquinone. The second mixture used in the outer layer (ie cladding) also
Further, it was made from 60 parts by weight of methyl methacrylate, 40 parts by weight of a monomer of methyl methacrylate, 0.5 part by weight of 1-hydrooxycyclohexyl phenyl ketone, and 0.1 part by weight of hydroquinone. The two mixtures are then pumped simultaneously through concentric mold orifices.

Using the apparatus shown in FIG. 1, the composite monofilament 24 is passed through a closed diffusion zone 26 maintained at a temperature of 80 ° C. of a length of about 45 cm, after which the composite monofilament 24 is evenly spaced. It passes through a curing zone 30 containing four 60 cm long high-pressure mercury lamps for curing. The volume ratio of inner layer to outer layer of the resulting composite monofilament is 1: 3. The composite monofilament has a radius of 1 mm. The refractive index distribution was found to be 1.508 at the filament center and 1.490 at the filament outer layer. The refractive index data is In
It was measured using a terphako interference microscope. It was also found that the composite monofilament showed a continuous decrease in refractive index from the center of the filament to the outer periphery of the filament. The refractive index profile of the obtained filament is shown in FIG. 2, respectively. There is no distortion in the image transmitted by the resulting filament.

Example 2 57 parts by weight of methyl methacrylate, 37 parts by weight of benzyl methacrylate monomer, 0.5 parts by weight of 1-hydrooxycyclohexyl phenyl ketone, and 0.1 parts of hydroquinone.
A first mixture was made for the inner layer (ie, core) composed of parts by weight. For an outer layer (ie, cladding) composed of 60 parts by weight of methyl methacrylate, 40 parts by weight of a monomer of methyl methacrylate, 0.5 parts by weight of 1-hydroxyoxycyclohexyl phenyl ketone, and 0.1 parts by weight of hydroquinone. A second mixture was also made. The two mixtures were then pumped simultaneously through a concentric mold orifice.

Using the apparatus shown in FIG. 1, after passing the composite monofilament 24 through a closed diffusion zone 26 maintained at a temperature of 80 ° C. of about 55 cm length, the composite monofilament 24 is evenly spaced. Four 60c placed
Curing zone 30 equipped with m high pressure mercury lamp for curing
Through. The volume ratio of inner layer to outer layer of the resulting composite monofilament is 1: 3. The composite monofilament has a radius of 1 mm. The refractive index profile measured at the filament center was found to be 1.516 and 1.490 for the filament outer layer. Refractive index data was measured using an Interphako interference microscope. It was also observed that the composite monofilament showed a continuous decrease in refractive index from the center of the filament to the outer periphery of the filament. The transmitted image by the obtained filament has no distortion.

Example 3 55 parts by weight of methyl methacrylate, 45 parts by weight of a monomer of benzyl methacrylate, 0.5 part by weight of 1-hydrooxycyclohexyl phenyl ketone, and 0.1 of hydroquinone.
A first mixture was made for the inner layer (ie, core) composed of parts by weight. For an outer layer (ie, cladding) composed of 60 parts by weight of methyl methacrylate, 40 parts by weight of a monomer of methyl methacrylate, 0.5 parts by weight of 1-hydroxyoxycyclohexyl phenyl ketone, and 0.1 parts by weight of hydroquinone. A second mixture was also made. The two mixtures were then pumped simultaneously through a concentric mold orifice.

Using the apparatus shown in FIG. 1, after passing the composite monofilament 24 through the closed diffusion zone 26 maintained at a temperature of 90 ° C. of about 55 cm length, the composite monofilament 24 is evenly spaced. Four 60c placed
Curing zone 30 equipped with m high pressure mercury lamp for curing
Through. The volume ratio of inner layer to outer layer of the resulting composite monofilament is 1: 3. The composite monofilament has a radius of 1 mm. The refractive index profile measured at the filament center was found to be 1.526 and 1.490 for the filament outer layer. Refractive index data was measured using an Interphako interference microscope. It was also observed that the composite monofilament showed a continuous decrease in refractive index from the center of the filament to the outer periphery of the filament. The transmitted image by the obtained filament has no distortion.

Example 4 Methyl methacrylate 58 parts by weight, benzyl methacrylate monomer 28 parts by weight, methyl methacrylate monomer 14
A first mixture for the inner layer (i.e., core) consisting of 1 part by weight, 0.5 part by weight of 1-hydrooxycyclohexyl phenyl ketone, and 0.1 part by weight of hydroquinone was made. 60 parts by weight of methyl methacrylate, 20 parts by weight of a monomer of methyl methacrylate, 0.5 part by weight of 1-hydroxycyclohexyl phenyl ketone, and hydroquinone of 0.
A second mixture was also made for the outer layer (ie, cladding), which consisted of 1 part by weight. Then the mixture of the two
It was simultaneously pumped through a concentric mold orifice.

Using the apparatus shown in FIG. 1, after passing the composite monofilament 24 through a closed diffusion zone 26 maintained at a temperature of 80 ° C. of about 55 cm length, the composite monofilament 24 is evenly spaced. Four 60c placed
Curing zone 30 equipped with m high pressure mercury lamp for curing
Through. The volume ratio of inner layer to outer layer of the resulting composite monofilament is 1: 3. The composite monofilament has a radius of 1 mm. The refractive index profile measured at the filament center was found to be 1.502 and for the outer filament layer was 1.476. Refractive index data was measured using an Interphako interference microscope. It was also observed that the composite monofilament showed a continuous decrease in refractive index from the center of the filament to the outer periphery of the filament. The transmitted image by the obtained filament has no distortion.

Example 5 55 parts by weight of methyl methacrylate, 45 parts by weight of a monomer of benzyl methacrylate, 0.5 part by weight of 1-hydrooxycyclohexyl phenyl ketone, and 0.1 of hydroquinone.
A first mixture was made for the inner layer (ie, core) composed of parts by weight. For an outer layer (ie, cladding) composed of 55 parts by weight of methyl methacrylate, 45 parts by weight of a monomer of methyl methacrylate, 0.5 part by weight of 1-hydroxyoxycyclohexyl phenyl ketone, and 0.1 part by weight of hydroquinone. A second mixture was also made. The two mixtures were then pumped simultaneously through a concentric mold orifice.

Using the apparatus shown in FIG. 1, after passing the composite monofilament 24 through the closed diffusion zone 26 maintained at a temperature of 90 ° C. of about 60 cm length, the composite monofilament 24 is evenly spaced. Four 60c placed
Curing zone 30 equipped with m high pressure mercury lamp for curing
Through. The volume ratio of inner layer to outer layer of the resulting composite monofilament is 1: 3. The composite monofilament has a radius of 1 mm. The refractive index profile measured at the filament center was found to be 1.515 and for the outer filament layer was 1.455. Refractive index data was measured using an Interphako interference microscope. It was also observed that the composite monofilament showed a continuous decrease in refractive index from the center of the filament to the outer periphery of the filament. The transmitted image by the obtained filament has no distortion.

[0039]

According to the present invention, there is provided a method for producing a graded index fiber having a continuous refractive index distribution from a surface layer of a fiber toward its center in a continuous production process from a polymer material.

According to the method of the present invention, extruding a composite monofilament from a polymer material solution containing two monomers having different refractive indices, and allowing the monomers to diffuse into each other before the composite monofilament is cured. A continuous manufacturing method is provided by diffusing in a diffusing region to match.

Further, according to the present invention, the above graded index fiber having high optical transparency can be produced in a continuous process.

[Brief description of drawings]

1 is a schematic diagram of an apparatus used in the method of the present invention.

2 is a diagram showing a refractive index profile of the graded index fiber obtained in Example 1. FIG.

[Explanation of symbols]

 10 Material Supply Tank 12 Material Supply Tank 14 Heating Device 16 Heating Device 18 Constant Volume Pump 20 Constant Volume Pump 22 Concentric Mold 24 Composite Monofilament 26 Closed Diffusion Zone 28 Separator 30 Curing Zone 32 Roller 34 Ejecting Roll

Claims (8)

[Claims] 1. Preparing a mixture of a first polymeric material and at least one first monomer that is a solvent for the first polymeric material; a second polymeric material and the first polymeric material. 2 a mixture with at least one second monomer which is a solvent for the polymeric material, said at least one second monomer being said at least one first monomer Preparing a second mixture which is different; to obtain a composite monofilament having an inner layer and an outer layer formed by said first and said second mixture with an interface between them Flowing the first and second mixtures through a concentric mold with an orifice; a sufficient amount of the first and second monomers across the interface to the outer and inner layers. Enough time for each to spread Passing the composite monofilament through a diffuser during a period of time; passing the composite monofilament into a curing jig so that the composite monofilament is cured, continuous from the center of the fiber to the outermost layer of the fiber. Manufacturing method of graded index fiber made of polymer material having refractive index distribution. 2. The first polymer material and the second polymer material are polymethylmethacrylate and methylmethacrylate and ethylmethacrylate, n-propylmethacrylate, isopropylmethacrylate, t-methacrylate. Butyl, cyclohexyl methacrylate, fluoroalkyl methacrylate, methyl 2-hydroxymethacrylate, 2-
Copolymerization with a monomer selected from the group consisting of phenoxyethyl methacrylate, glyceryl methacrylate, benzyl methacrylate, phenyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, fluoroalkyl acrylate and acrylic acid. The method of claim 1, wherein the method is selected from the group consisting of coalescence. 3. The at least one first monomer and the at least one second monomer are methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, methacrylic acid. t-butyl, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, fluoroalkyl methacrylate, methyl 2-hydroxymethacrylate, ethyl 2-phenoxymethacrylate, glaryl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate And a fluoroalkyl acrylate is selected from the group consisting of: 4. The volume ratio of the inner layer to the outer layer is about 1:
The method of claim 1, wherein the method is between 1 and about 1: 100. 5. The method according to claim 4, wherein the volume ratio of the inner layer to the outer layer is between about 1: 1 and about 1:10. 6. The method of claim 4, wherein the volume ratio of the inner layer to the outer layer is between about 1: 1 and about 1: 5. 7. The content of the first monomer in the first mixture or of the second monomer in the second mixture is about 10 of the total mixture.
To about 80% by weight. 8. The content of the first monomer in the first mixture or the second monomer in the second mixture is about 40 of the total mixture.
8. The process according to claim 7, which is in the range of about 70% by weight.