JP2023149651A - plastic optical fiber - Google Patents

Abstract

To provide a plastic optical fiber (for example, for design illumination) excellent in optical characteristics, heat resistance, mechanical strength, and scratch resistance.SOLUTION: A plastic optical fiber includes: a core containing a polymethyl methacrylate-based resin; a cladding layer that surrounds a periphery of the core and contains a transparent fluororesin a refractive index of which is lower than that of the core; and, further outside the cladding layer, a protection layer that contains a transparent resin a refractive index of which is higher than that of the cladding layer. A flexural modulus of the resin forming the protection layer is 1000 MPa or more and 4000 MPa or less.SELECTED DRAWING: None

Description

The present invention relates to plastic optical fibers and their uses.

Plastic optical fibers have a structure in which the outer periphery of a core made of a transparent resin is covered with a cladding layer made of a resin with a lower refractive index than the transparent resin, and the core is completely reflected at the boundary between the core and the cladding layer. It is a medium that transmits light within a device. Generally, plastic optical fibers are used as plastic optical fiber cables with a coating layer provided on the outside of the plastic optical fibers to prevent physical or chemical damage. Plastic optical fibers with such a configuration are used as communication media for industrial and automotive applications because the light incident from one end undergoes total internal reflection at the interface between the core and cladding and is efficiently transmitted to the other end. Widely used.

In these applications, it is important to transmit light that enters from one end to the other end without leaking light along the way. If it can function as a fiber for decorative lighting that leaks light from the side, it can be used for alternative purposes such as indirect lighting inside and outside buildings and electric displays. In addition, by using these as fabrics woven into them, it can be expected to be used in decorative lighting applications such as interior lighting for moving objects such as cars, trains, and airplanes, and other decorative applications.

For such lighting applications, a method has been proposed in which light is leaked by performing sandblasting or laser processing on plastic optical fibers to intentionally damage the cladding (for example, see Patent Document 1).

Japanese Patent Application Publication No. 2016-201200

However, processing of plastic optical fibers as described in Patent Document 1 requires a high degree of processing precision. Particularly when precision processing is applied to an arbitrary location to allow light to leak from the side, if there are scratches on the surface of the plastic optical fiber, excess light may leak from there. It is required that there be no Furthermore, if the plastic optical fiber described in Patent Document 1 has uneven thickness in the cladding layer, or if the fiber has a tendency to twist or bend, the cladding layer will be shaved too much, causing strong local light leakage and bright spots. It may also cause. Therefore, for use in decorative lighting, there is a demand for plastic optical fibers that have good surface scratch resistance and have an excellent balance between workability and mechanical strength.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a plastic optical fiber (for example, for decorative lighting) that has excellent optical properties, heat resistance, mechanical strength, and scratch resistance.

The inventors of the present invention conducted extensive studies to solve the above problems, and found that a plastic optical fiber that satisfies specific requirements has excellent optical properties, heat resistance, and mechanical strength, and has completed the present invention. .

That is, the present invention relates to the following.
[1]
A core containing a polymethyl methacrylate resin, a cladding layer surrounding the core and having a refractive index lower than that of the core and containing a transparent fluororesin, and further outside the cladding layer a cladding layer having a refractive index lower than that of the cladding layer. Contains a protective layer containing high and transparent resin,
A plastic optical fiber, wherein the resin forming the protective layer has a bending elastic modulus of 1000 MPa or more and 4000 MPa or less.
[2]
The plastic optical fiber according to [1], wherein the protective layer contains at least one selected from the group consisting of acrylic resin, polyolefin resin, polyester resin, and polyamide resin.
[3]
the protective layer contains a colorant,
The plastic optical fiber according to [1] or [2], wherein the content of the colorant is 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the resin forming the protective layer.
[4]
The plastic optical fiber according to [3], wherein the colorant is a black pigment or a black dye.
[5]
The plastic optical fiber according to any one of [1] to [4], wherein the transparent fluororesin contained in the cladding layer has a refractive index of 1.35 or more and 1.48 or less when measured at 20° C. with sodium D line. .
[6]
An optical fiber illumination in which at least one end of the plastic optical fiber according to any one of [1] to [5] is connected to a light source.
[7]
An optical fiber fabric having at least a portion of the plastic optical fiber according to any one of [1] to [5].
[8]
An optical fiber knitted fabric having at least a portion of the plastic optical fiber according to any one of [1] to [5].
[9]
A method for manufacturing a side-emitting plastic optical fiber, comprising the steps of forming the plastic optical fiber according to any one of [1] to [5], and sandblasting the plastic optical fiber.

According to the present invention, it is possible to provide a plastic optical fiber (hereinafter sometimes referred to as POF) that has excellent optical properties, heat resistance, mechanical strength, and scratch resistance.

1 is a schematic cross-sectional view of an example of a single-core plastic optical fiber of this embodiment. 1 is a schematic cross-sectional view of an example of a multicore plastic optical fiber of this embodiment. A schematic cross-sectional view of another example of the multicore plastic optical fiber of this embodiment is shown.

Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "this embodiment") will be described in detail. The present embodiment below is an illustration for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be implemented with appropriate modifications within the scope of its gist. Note that duplicate explanations of the same elements in the drawings will be omitted. In addition, the positional relationships such as top, bottom, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios.

The plastic optical fiber of this embodiment includes a core containing a polymethyl methacrylate resin, a cladding layer surrounding the core, having a lower refractive index than the core and containing a transparent fluororesin, and further outside the cladding layer. The protective layer has a refractive index higher than that of the cladding layer and includes a transparent resin, and the resin forming the protective layer has a flexural modulus of 1000 MPa or more and 4000 MPa or less. The plastic optical fiber of this embodiment has such characteristics and thus has excellent optical properties, heat resistance, mechanical strength, and scratch resistance.

In this embodiment, for example, a POF as shown in FIGS. 1 to 3 having the above characteristics can be used. Specifically, for example, by forming a three-layer structure consisting of a core, a transparent cladding resin with a lower refractive index than the core, and a transparent protective resin with a higher refractive index than the cladding resin, the structure shown in FIGS. A POF as shown in FIG. 3 can be used.

FIG. 1 shows a schematic cross-sectional view of an example of the POF of this embodiment.
As shown in FIG. 1, the single-core POF 10 has a core 12 at the center, a cladding layer 14 formed around the outer periphery of the core 12, and a protective layer 16 formed around the outer periphery of the cladding layer 14. We are prepared. The core 12, cladding layer 14, and protective layer 16 constitute a single-core POF 10.

FIG. 2 is a schematic cross-sectional view of another example of the POF of this embodiment.
As shown in FIG. 2, the multi-core POF 20 has seven cores 22 each individually covered with a cladding layer 24, and these are covered with a protective layer 26 to make the multi-core POF 20 multi-core. Note that, although the POF 20 is a seven-core type optical fiber, the POF of this embodiment is not limited to seven cores.

FIG. 3 is a schematic cross-sectional view of another example of the POF of this embodiment.
As shown in FIG. 3, the multicore POF 30 has seven cores 32 covered with a cladding layer 34, making it multicore. Further, a protective layer 36 is provided around the outer periphery of the cladding layer 34 to constitute the plastic optical fiber 30. Note that, although the POF 30 is a seven-core type optical fiber cable, the POF of this embodiment is not limited to seven cores.

Hereinafter, the parts, materials, etc. that make up the POF of this embodiment will be explained in detail.

(core)
In the POF of this embodiment, the resin constituting the core (hereinafter also referred to as "core resin") includes a polymer having methyl methacrylate units (polymethyl methacrylate resin).
The resin constituting the core is preferably a transparent resin.
As the core resin, those known as core resins for plastic optical fibers can also be used.
The core resin includes, for example, polymethyl methacrylate resin, but may also include polycarbonate resin or the like. Among them, polymethyl methacrylate resin is preferred from the viewpoint of transparency.

Polymethyl methacrylate resin (hereinafter also referred to as "PMMA") refers to a methyl methacrylate homopolymer or a copolymer containing 50% by mass or more of methyl methacrylate monomer. That is, the polymethyl methacrylate resin may be a copolymer of a methyl methacrylate monomer and another monomer copolymerizable with the methyl methacrylate monomer.
Other monomers that can be copolymerized with the methyl methacrylate monomer are not particularly limited, but include, for example, acrylic esters such as methyl acrylate, ethyl acrylate, and butyl acrylate; ethyl methacrylate, and propyl methacrylate. , methacrylic acid esters such as cyclohexyl methacrylate; maleimides such as isopropylmaleimide; acrylic acid, methacrylic acid, styrene, and the like. The other copolymerizable monomers may be used alone or in combination of two or more.

The weight average molecular weight of the polymethyl methacrylate resin is not particularly limited, but from the viewpoint of moldability, it is preferably 80,000 or more and 200,000 or less, more preferably 100,000 or more and 120,000 or less. The weight average molecular weight can be measured by a conventionally known GPC (gel permeation chromatography) method.

(cladding layer)
In the POF of this embodiment, the cladding layer surrounds the core, and is formed, for example, on the outer periphery of the core. When the optical signal is reflected at the interface between the cladding layer and the core, the optical signal is propagated within the optical fiber. From this point of view, it is preferable that the cladding layer directly covers the surface of the core.

The resin constituting the cladding layer (hereinafter also referred to as "cladding resin") includes a transparent fluororesin having a lower refractive index than the core. Among them, fluororesins with high visible light transmittance are particularly preferred. By using such a fluororesin, transmission loss can be further suppressed.

Such fluororesins include, but are not particularly limited to, fluorinated methacrylate polymers, polyvinylidene fluoride resins, ethylene-tetrafluoroethylene copolymers, and the like.
Fluorinated methacrylate polymers include, but are not particularly limited to, fluorine-containing polymers such as fluoroalkyl methacrylate, fluoroalkyl acrylate, α-fluoro-fluoroalkyl acrylate, etc. from the viewpoint of high transmittance and excellent heat resistance and moldability. Acrylate or methacrylate monomers are preferred. It may also be a copolymer containing units derived from fluorine-containing (meth)acrylate monomers and units derived from other components copolymerizable with these, and copolymerizable hydrocarbons such as methyl methacrylate. Copolymers with units derived from monomers of the system are preferred. A copolymer of a unit derived from a fluorine-containing (meth)acrylate monomer and a unit derived from a hydrocarbon monomer copolymerizable with this is preferred because the refractive index can be controlled.

Polyvinylidene fluoride resins are not particularly limited, but from the viewpoint of excellent heat resistance and moldability, vinylidene fluoride homopolymers; vinylidene fluoride, tetrafluoroethylene, hexafluoropropene, trifluoroethylene, A copolymer with at least one monomer selected from the group consisting of hexafluoroacetone, perfluoroalkyl vinyl ether, chlorotrifluoroethylene, ethylene, and propylene; a polymer containing units derived from these vinylidene fluoride components; Alloys with PMMA are preferred.

Furthermore, from the viewpoint of heat resistance and mechanical strength, the fluororesin constituting the cladding layer is preferably a copolymer containing vinylidene fluoride, hexafluoropropene, and tetrafluoroethylene, and more preferably vinylidene fluoride. A copolymer containing 40 mol% or more and 62 mol% or less, a tetrafluoroethylene component 28 mol% or more and 40 mol% or less, and a hexafluoropropene component 8 mol% or more and 22% mol% or less is preferred.
The copolymer of vinylidene fluoride, hexafluoropropene and tetrafluoroethylene can be used with trifluoroethylene, hexafluoroacetone, perfluoroalkyl vinyl ether, chlorotrifluoroethylene, ethylene, propylene, etc., as long as it is within the above component ratio. It may be a copolymer of

The transparent fluororesin contained in the cladding layer preferably has a refractive index of 1.35 or more and 1.48 or less, more preferably 1.36 or more and 1.45 or less, even more preferably It is 1.37 or more and 1.42 or less. If the refractive index of the transparent fluororesin contained in the cladding layer is 1.35 or more, the numerical aperture of the POF (described later) will be large and a sufficient amount of light can be propagated, and even when processed for design lighting, a considerable amount of light can be transmitted. You can get the amount of light. On the other hand, if the refractive index of the transparent fluororesin included in the cladding layer is 1.48 or less, the numerical aperture of the POF becomes small, and light leaks easily when the POF is bent, resulting in excellent luminescence.

Here, the numerical aperture (hereinafter also referred to as "NA") represents the relationship between the refractive index of the core resin and the cladding resin, and is expressed by the following formula (1). NA is a factor that determines the reflection characteristics of light, and the larger the NA value, the better the coupling with the light source, the larger the allowable range of optical axis deviation, and the more efficient light propagation becomes an index. Therefore, in order to efficiently propagate light, the numerical aperture is preferably 0.15 or more and 0.65 or less.
NA=(Ncore ² - Nclad ² ) ^0.5 ...(1)
Ncore Refractive index of core resin
Nclad Refractive index of clad resin

In addition, in a POF having a structure as shown in the single-core POF of FIG. 1 and the multi-core POF of FIG. 2, the thickness of the cladding layer of the fiber is preferably 1.0 μm or more and 10.0 μm or less, and 1.5 μm or more. It is more preferably 9.0 μm or less, and even more preferably 3.0 μm or more and 7.0 μm or less. If the thickness of the cladding layer is 1.0 μm or more, visible light can be effectively totally reflected when it is transmitted through the POF. On the other hand, if the thickness of the cladding layer is 10.0 μm or less, the cladding layer is sufficiently thick and it becomes easier to cut the cladding layer when processing the POF surface by blasting or the like, which will be described later, in order to emit light. preferable.

Further, in the case of a POF having a multi-core structure as shown in FIG. 3, a cladding resin is filled between each core, and this cladding resin has a function of reflecting light propagating through the cores. Therefore, in this case, the thickness of the cladding is defined by the inter-core distance (the distance between the cores) in this structure. In this case, the distance between the cores is preferably 0.5 μm or more and 5.0 μm or less, more preferably 1.0 μm or more and 4.0 μm or less, and 1.5 μm or more and 3.5 μm or less. If the distance between the cores is 0.5 μm or more, visible light can be effectively totally reflected when it is transmitted through the POF. On the other hand, if the distance between the cores is 5.0 μm or less, the cladding layer is thick, so crosstalk in which light leaking from the core enters the core again is suppressed, and the fiber can function as a side-emitting fiber.

(protective layer)
The plastic optical fiber of this embodiment includes a protective layer further outside the cladding layer that has a higher refractive index than the cladding layer. Specifically, the protective layer is provided on the outer periphery of the core/clad structure, for example, as shown in FIG. In this way, by providing a protective layer with an appropriate function on the outer periphery of the cladding layer, it is possible to give POF functionality such as heat resistance, weather resistance, and scratch resistance, as well as mechanical strength. Therefore, the performance of the plastic optical fiber can be further improved.

Here, the resin constituting the protective layer (hereinafter also referred to as "protective resin") will be explained.
Generally, in order to improve the functionality of POF, when the core resin is coated with a thermoplastic resin to make the POF multi-layered, the refractive index of the resin forming the outermost resin layer (corresponding to the protective layer used in this embodiment) In many cases, a material having a refractive index lower than that of the resin forming the inner layer (corresponding to the cladding layer used in this embodiment) is used. With such a structure, the protective layer can be given a function as a second cladding layer, and light leaking from the cladding can be reflected at the outermost layer, and an effect of effectively propagating light can be expected. However, since the POF of this embodiment is, for example, a POF for design lighting, the refractive index of the protective resin (for example, the resin forming the outermost layer of the POF) is selected to be higher than that of the cladding resin. By doing so, it becomes possible to intentionally leak light that leaks from the cladding layer when the POF is bent.

In particular, the resin used for the protective layer of this embodiment is a resin whose flexural modulus falls within a specific range. The bending elastic modulus of the resin is also related to the surface hardness of the resin, and the larger the bending elastic modulus, the higher the hardness. Therefore, by providing a resin having a high bending elastic modulus on the protective layer of the POF (for example, the surface of the POF), it is possible to improve the scratch resistance.
Here, the bending elastic modulus of the resin can be measured by a method according to JIS K7171; 2016 "Plastics - How to determine bending properties". The flexural modulus of the protective resin measured under the above conditions is preferably in the range of 1,000 MPa to 4,000 MPa, more preferably in the range of 1,500 MPa to 3,750 MPa, and most preferably in the range of 2,000 MPa to 3,500 MPa. If the flexural modulus of the protective resin is 1000 MPa or more, when used as a POF, it will function satisfactorily as a protective layer and improve scratch resistance and weather resistance. Further, if the flexural modulus of the protective resin is 4000 MPa or less, the processability will not be impaired when the POF is subjected to blasting treatment as described below to improve the design.
In particular, POF woven or knitted fabrics formed by weaving POF with monofilament as described below are required to have high scratch resistance and weather resistance in the usage environment after forming. In this embodiment, since the flexural modulus of the protective resin is within the above range, it is possible to suppress these external damages.

In this embodiment, the protective resin that satisfies these conditions is preferably a thermoplastic resin that can be spun together with the material forming the core/clad structure. From the viewpoint of adhesion with the layer and moldability, it is preferable to contain at least one selected from the group consisting of acrylic resin, polyolefin resin, polyester resin, and polyamide resin, particularly acrylic resin and polyolefin resin. This is preferred because the resin has appropriate surface hardness and excellent transparency. As the acrylic resin, a polymethyl methacrylate resin such as a methyl methacrylate homopolymer or a copolymer containing 50% by mass or more of methyl methacrylate monomer, which is a specific example of the core resin used in this embodiment, is preferably used. I can do it. Polyolefin resins include amorphous polyethylene resins made by copolymerizing ethylene with α-olefins (also referred to as higher α-olefins) such as propylene, 1-butene, 1-hexene, and 1-octene, and propene with ethylene and higher α-olefins. Amorphous polypropylene resins made by copolymerizing α-olefins, cyclic olefin resins made by polymerizing cyclic olefins such as cycloolefins, and cyclic olefin copolymers made by copolymerizing cyclic olefins and α-olefins become transparent. It is preferable because it is excellent.

Furthermore, the protective layer may contain a colorant. Specifically, the protective resin used for the protective layer is a dye or pigment that absorbs light of any wavelength in order to effectively color the light leaking from the cladding layer or to control the amount of light emitted. It may be functionalized by containing a coloring agent. Preferably, the colorant is a black pigment or black dye. For example, if a dye is added to POF that absorbs light of a specific wavelength when visible light that includes light in the entire wavelength range from 380 to 780 nm is transmitted, it will absorb light of a specific wavelength from the leaked light. This makes it possible to arbitrarily adjust the color tone of the leaking light. In addition, if a black pigment such as carbon black is added to the protective layer, when processing the surface of a plastic optical fiber to intentionally cause local light leakage, as described below, if the protective layer is black, it can be processed easily. It becomes possible to suppress light emission other than the part, and it becomes possible to obtain a plastic optical fiber with good design and a processed product thereof.

The content of such a coloring agent is preferably 0.1 parts by mass or more and 10 parts by mass or less, and 0.5 parts by mass or more and 7 parts by mass or less, based on 100 parts by mass of the resin forming the protective layer. The amount is more preferably 0.7 parts by mass or more and 5 parts by mass or less from the viewpoint of dispersibility of the colorant. If 0.1 part by mass or more of the colorant is added, unnecessary light leakage can be suppressed when the POF is bent or when the POF is subjected to surface treatment such as blasting, which will be described later. Furthermore, by adding 10 parts by mass or less of a coloring agent, the appearance of the POF is not impaired.

Furthermore, various modifiers may be added to the protective resin used in this embodiment for the purpose of further improving weather resistance and scratch resistance in combination with the above-mentioned colorant.
Additives that improve weather resistance include commercially available modifiers such as benzotriazole UV absorbers, triazine UV absorbers, benzophenone UV absorbers, benzoate UV absorbers, and hindered amine light stabilizers that absorb UV rays. It can be used.
Furthermore, as additives for improving scratch resistance, commercially available modifiers such as polyolefin waxes, silicone surface conditioners, and polysiloxane surface conditioners can be used.

The content of such a modifier is preferably 0.01 parts by mass or more and 5 parts by mass or less, and 0.05 parts by mass or more and 3 parts by mass or less, based on 100 parts by mass of the resin forming the protective layer. is more preferred, and from the viewpoint of dispersibility of the modifier, 0.1 part by mass or more and 1 part by mass or less is even more preferred. If 0.01 parts by mass or more of the modifier is added, a sufficient modification effect can be exerted on the surface of POF. Further, by adding 5 parts by mass or less of the modifier, the appearance of the POF is not impaired.

Additives such as colorants and modifiers to be added to such a protective layer are not particularly limited, but for example, heat resistance to the extent that they do not decompose during melt-kneading and dispersibility in the protective resin should be taken into consideration. You can use any one you like. The method of mixing the protective resin and the above additives is not particularly limited, but examples include a method of directly melt-kneading the colorant using a device such as a known twin-screw extruder, and a method of directly melt-kneading the colorant using a device such as a known twin screw extruder, Examples include a method in which a masterbatch is prepared by kneading the material into a base resin, and this is melt-kneaded with the protective resin using a single-screw extruder or the like.

The thickness of the protective layer is, for example, preferably 1.0 μm or more and 10.0 μm or less, more preferably 1.5 μm or more and 9.5 μm or less, and 2.0 μm or more and 9.0 μm or less, for example, within a range that does not reduce the light intensity of the plastic optical fiber. The following are more preferred. If the thickness of the protective layer is 1.0 μm or more, the POF can be reliably protected from scratches and the effects of chemicals and the like. On the other hand, if the thickness of the protective layer is 10.0 μm or less, the flexibility when used as a POF is not impaired.

Next, an example of a method for manufacturing the side-emitting plastic optical fiber according to this embodiment will be described.

The method for manufacturing a side-emitting plastic optical fiber of this embodiment includes the steps of forming the above-mentioned plastic optical fiber, and performing sandblasting on the plastic optical fiber.
In the manufacturing method of this embodiment, the plastic optical fiber (POF) that is the source of the side-emitting plastic optical fiber is manufactured using a composite nozzle that can spin multiple resins forming the core, cladding layer, and protective layer all at once. It can be manufactured using According to this composite spinning method, it is possible to continuously manufacture a core coated with a cladding and a protection coated with a uniform thickness.

Next, by heating and stretching the POF to 1.5 to 2.5 times, mechanical properties and resistance to heat loss can be imparted to the POF. When the stretching ratio is 1.5 times or more, the stretching orientation of POF is good and the mechanical strength is improved. On the other hand, when the stretching ratio is 2.5 times or less, thermal shrinkage of POF can be suppressed in a high-temperature environment.
The outer diameter of the POF used in this embodiment is preferably 0.1 mm to 3.0 mm, and may be selected as appropriate depending on the purpose, but from the viewpoint of workability such as blasting treatment, which will be described later, the outer diameter of the POF is preferably 0.1 mm to 3.0 mm. More preferably, it is 1.5 mm.

In the POF used in this embodiment, the surface of the fiber is subjected to a sandblasting treatment to intentionally damage the surface of the POF, thereby improving the side light emitting property. The sandblasting process is not particularly limited, but for example, fine particles of fused alumina, silicon carbide, etc. with a particle size of 10 to 500 μm are sprayed onto a desired location on the surface of a plastic optical fiber to form a protective layer or cladding layer that forms a POF. Cut to a certain depth. By performing such surface treatment, it becomes possible to effectively leak light incident from one end of the POF from the side surface.

In this way, POF fabrics or knitted fabrics can be obtained by weaving the sandblasted POF into synthetic fibers such as polyester, polyamide, and acrylic, semi-synthetic fibers such as rayon, natural fibers such as cotton and wool, etc.
The optical fiber fabric of this embodiment has at least a portion of the above-mentioned plastic optical fiber. Moreover, the optical fiber knitted fabric of this embodiment has the above-mentioned plastic optical fiber at least in part.
POF woven fabrics are not particularly limited, but can be obtained, for example, by weaving POF as warp threads and other fibers as weft threads while intersecting them using a known woven fabric manufacturing method. Further, the method for producing the POF knitted fabric is not particularly limited, but, for example, a known method for producing knitted fabrics can be employed. Specifically, there is no particular limitation, but it can be obtained, for example, by hooking the next POF onto a looped POF and knitting it. POF woven fabrics have a higher fiber density and are more durable than POF knitted fabrics. Therefore, it can be suitably used for applications that require durability, such as vehicle interior lighting, especially the skin of vehicle interior materials such as door trims and roof trims.
On the other hand, POF knitted fabrics are lightweight and have excellent elasticity, and by taking advantage of their light weight, they can be suitably used for medical blankets, particularly for phototherapy applications such as neonatal jaundice.

Note that the above-mentioned blasting treatment may be performed after the POF obtained in this embodiment is woven in advance with chemical fibers such as polyester or polyamide to produce a POF fabric. By performing a blasting process after manufacturing the POF fabric, it becomes possible to impart patterns such as arbitrary designs with high precision.

(Optical fiber lighting)
In the optical fiber illumination according to this embodiment, at least one end (for example, an end face) of the above-mentioned plastic optical fiber (POF) is connected to a light source. The light source is not particularly limited as long as it is publicly known, and for example, discharge luminescent bodies such as mercury lamps and fluorescent lamps, and electroluminescent bodies such as organic/inorganic EL and LED can be used. In particular, EL and LED can be used as light sources suitable for POF lighting because they generate less heat and do not get hot easily. LEDs can emit light at various wavelengths in the ultraviolet, visible, and infrared regions depending on the semiconductor material used, so by selecting any wavelength of light, there is a high degree of flexibility in illumination, making it suitable for design lighting and medical applications. It becomes possible to expand to

Hereinafter, the present embodiment will be described with reference to specific examples and comparative examples, but the present embodiment is not limited to the examples described below.
First, evaluation methods in Examples and Comparative Examples will be explained.

(transmission loss)
Using POF cables manufactured in Examples and Comparative Examples described later, transmission loss was measured by a 22 m-2 m cutback method under conditions of a measurement wavelength of 650 nm and an excitation NA of 0.15.

(Transmission loss after 1000 hours)
A 22 m POF cable manufactured in the Examples and Comparative Examples described later was left in a skein-wound state under a dry heat environment of 85°C and a moist heat environment of 85°C and 85% RH, respectively, and the transmission loss after 1000 hours was measured. was measured.
The measurement conditions were a measurement wavelength of 650 nm and an excitation NA of 0.15, and the transmission loss was measured using a 22 m-2 m cutback method.

(bending modulus)
The protective resin used in the Examples and Comparative Examples described later was formed into a strip-shaped test piece with a length of 80 mm, a width of 10 mm, and a thickness of 4 mm. Both ends were supported horizontally from below, and the test piece was tested from the center at a test speed of 2 mm/min. The value obtained by dividing the maximum load when a load was applied by the cross-sectional area was calculated as the bending elastic modulus.

(Evaluation of scratch resistance of POF)
In order to confirm the presence or absence of scratches on the surface of POFs manufactured in Examples and Comparative Examples described later, a 500m POF manufactured under the same conditions was wound around a bobbin, and light from a halogen lamp was emitted from one end in a dark room to examine the surface of the fiber. The presence or absence of scratches was visually confirmed. Items with no scratches on the surface and no local light leakage were marked as ○, and items with scratches and light leaking from the sides in the form of bright spots or lines were marked as ×.

(Refractive index)
A film-like test piece with a thickness of 200 μm was produced by melt pressing using the core resin, clad resin, and protective resin used in Examples and Comparative Examples described later. Using an Abbe refractometer, the refractive index (nD20) of the sodium D line at 20°C was measured. In addition, regarding the refractive index of the colored protective resin, the refractive index of the base resin before being colored was measured.
Further, the numerical aperture (NA) was calculated from the refractive index of the core resin and the cladding layer resin using the following formula (1).
NA=(Ncore ² - Nclad ² ) ^0.5 ...(1)
Ncore Refractive index of core resin
Nclad Refractive index of clad resin
Note that NA is a factor that determines the reflection characteristics of light, and the larger the value of NA, the better the coupling with the light source, the larger the allowable range of optical axis deviation, and the more efficient light propagation becomes an index.

(Clad layer thickness, protective layer thickness)
POFs produced in Examples and Comparative Examples described below were sliced thinly using an industrial razor so that both ends were flat, and the cross section was measured using a Keyence Microscope VHX-8000 at room temperature and 25°C atmosphere.

(bending light amount)
Regarding POFs manufactured in Examples and Comparative Examples to be described later, the light intensity reduction rate was measured when the POFs were bent along 90 degrees using a jig with a bending radius of 1 mmR.
Light intensity reduction rate (%) = Light intensity after bending / Light intensity before bending x 100
The smaller the 90-degree bending light intensity retention rate, the greater the light intensity loss during bending, which indicates that the amount of light emitted from the side is larger.

(mechanical strength)
Regarding POFs manufactured in Examples and Comparative Examples described below, the yield point strength when POFs are deformed and the maximum breaking strength at rupture (tensile The breaking strength) was measured. The higher the yield point strength and tensile strength at break, the better the mechanical properties of the POF.

(heat shrinkage rate)
At room temperature (23°C), POFs produced in the Examples and Comparative Examples described below were cut into 1 m lengths with an industrial razor so that both ends were flat, heated at 105°C for 1 hour, and then cooled to room temperature. After that, the cable length was measured, and the shrinkage rate was determined using the following formula. POF with a heat shrinkage rate of 4% or less was considered to have sufficient heat resistance and was passed.
Heating shrinkage rate (%) = (1m - cable length after test) / 1m x 100

The core resin, clad resin, and protective resin used in Examples and Comparative Examples are listed at the bottom of Tables 1 and 3.

[Example 1] (No coloring)
Polymethyl methacrylate resin (PMMA) with a refractive index of 1.49 and an MFR of 1.5 g/10 minutes is used as the core resin, and perfluoroalkyl vinyl ether, vinylidene fluoride, and tetrafluoride are used as the clad resin in contact with the core. A quaternary copolymer (refractive index: 1.35) of fluoroethylene and hexafluoropropene was used. Further, as a resin constituting the protective layer (protective resin), a copolymer of methyl methacrylate and methyl acrylate (refractive index 1.49, flexural modulus 3300 MPa) was used.
These polymers are melted, supplied to a spinning head at 230°C, and subjected to melt composite spinning using a concentric composite nozzle, and then stretched to double in the fiber axis direction in a hot air heating furnace at 150°C to form a cladding. A plastic optical fiber (POF) having a diameter of 0.5 mm and having a layer thickness of 5.0 μm and a protective layer thickness of 5.0 μm was obtained.

The POF thus obtained was evaluated by the evaluation method described above, and the results are shown in Table 2.

[Example 2, Comparative Examples 1 to 3] (No coloring)
A POF with a diameter of 0.5 mm was obtained in the same manner as in Example 1, except that the resins used for the cladding layer and the protective layer were changed to the materials shown in Table 1.
The same evaluation as in Example 1 was performed using these plastic optical fibers (POF), and the results are shown in Table 2. Note that the POF shown in Comparative Example 1 was not provided with a protective layer. Comparative Examples 2 and 3 were POFs manufactured with a resin composition in which the protective resin had a bending elastic modulus lower than 1000 MPa.

Fluorine resin 1: Perfluoroalkyl vinyl ether/vinylidene fluoride/tetrafluoroethylene/hexafluoropropene quaternary copolymer (transparent resin)
Fluorine resin 2: Vinylidene fluoride/tetrafluoroethylene copolymer (transparent resin)
Fluorine resin 3: vinylidene fluoride/tetrafluoroethylene/hexafluoropropene ternary copolymer (transparent resin)
Fluorine resin 4: Fluoroalkyl methacrylate copolymer (transparent resin)
Fluorine resin 5: Fluoroalkyl methacrylate/methyl methacrylate copolymer (transparent resin)
Acrylic resin: Methyl methacrylate/methyl acrylate polymer (transparent resin)
Polyolefin resin 1: Cyclic olefin resin: (ethylene/norbornene copolymer) (transparent resin)
Polyolefin resin 2: Low density polyethylene resin (transparent resin)

From the results in Table 2, it can be seen that the POF provided with the protective layer having an appropriate bending elastic modulus obtained in Examples 1 and 2 had a light intensity retention rate of 90% or less when bent at 90 degrees in the bending light intensity test, and the side emission It was found that the amount of leaked light was sufficient for a POF. Furthermore, the POFs obtained in Examples 1 and 2 were proven to be resistant to scratches during manufacturing. In addition, the POFs obtained in Examples 1 and 2 had good breaking strength and heat resistance in other physical properties as well. On the other hand, in Comparative Example 1 in which no protective layer was provided, the amount of leaked light was equivalent to that of the example, but the scratch resistance and heat resistance were insufficient. Furthermore, in Comparative Example 2, the light intensity retention rate when bent by 90 degrees was 94% in the bending light intensity test, and the amount of leaked light was insufficient as a side-emitting POF. Further, in Comparative Examples 2 and 3, the flexural modulus of the protective resin was lower than 1000 MPa, and the scratch resistance was poor.

[Example 3] (Colored product)
Polymethyl methacrylate resin (PMMA) with a refractive index of 1.49 and an MFR of 1.5 g/10 minutes is used as the core resin, and perfluoroalkyl vinyl ether, vinylidene fluoride, and tetrafluoride are used as the clad resin in contact with the core. A quaternary copolymer (refractive index: 1.35) of fluoroethylene and hexafluoropropene was used. Further, as a resin constituting the protective layer (protective resin), a copolymer of methyl methacrylate and methyl acrylate (refractive index 1.49, flexural modulus 3300 MPa) was used. The protective resin used was a resin composition obtained by melt-kneading a resin in which 5 parts by mass of carbon black as a coloring agent was added to 100 parts by mass of the resin at 230°C.
These polymers are melted, supplied to a spinning head at 230°C, and subjected to melt composite spinning using a concentric composite nozzle, and then stretched to double in the fiber axis direction in a hot air heating furnace at 150°C to form a cladding. A plastic optical fiber (POF) having a diameter of 0.5 mm and having a layer thickness of 5 μm and a protective layer thickness of 5 μm was obtained.

The POF thus obtained was evaluated using the evaluation method described above, and the results are shown in Table 4. In addition, Table 5 shows each formulation in which the protective resin was blended with a colorant and an additive.

[Example 4, Comparative Examples 4-5] (Coloring)
A POF with a diameter of 0.5 mm was obtained in the same manner as in Example 1, except that the resins used for the cladding layer and the protective layer were changed to the materials shown in Table 3. In addition, the additives (colorant and modifier) shown in Table 5 were added in predetermined amounts as the protective resin, and the resin was melt-kneaded using a twin-screw extruder in the same manner as in Example 3.
The same evaluation as in Example 3 was performed using these plastic optical fibers, and the results are shown in Table 4.

Fluorine resin 1: Perfluoroalkyl vinyl ether/vinylidene fluoride/tetrafluoroethylene/hexafluoropropene quaternary copolymer (transparent resin)
Fluorine resin 2: Vinylidene fluoride/tetrafluoroethylene copolymer (transparent resin)
Fluorine resin 3: vinylidene fluoride/tetrafluoroethylene/hexafluoropropene ternary copolymer (transparent resin)
Fluorine resin 4: Fluoroalkyl methacrylate copolymer (transparent resin)
Fluorine resin 5: Fluoroalkyl methacrylate/methyl methacrylate copolymer (transparent resin)
Acrylic resin: Methyl methacrylate/methyl acrylate polymer (transparent resin)
Polyolefin resin 1: Cyclic olefin resin: (ethylene/norbornene copolymer) (transparent resin)
Polyolefin resin 2: Low density polyethylene resin (transparent resin)

Fluorine resin 3: vinylidene fluoride/tetrafluoroethylene/hexafluoropropene ternary copolymer (transparent resin)
Acrylic resin: Methyl methacrylate/methyl acrylate polymer (transparent resin)
Polyolefin resin 1: Cyclic olefin resin: (ethylene/norbornene copolymer) (transparent resin)
Polyolefin resin 2: Low density polyethylene resin (transparent resin)
Dye 1: Nigrosine black dye

From the results in Table 2, it can be seen that the POFs provided with the protective layer having appropriate flexural modulus obtained in Examples 3 and 4 had good scratch resistance without any light leakage such as bright spots in the light projection test. I found out that In addition, the POFs obtained in Examples 3 and 4 had good breaking strength and heat resistance in other physical properties as well. On the other hand, in Comparative Examples 4 and 5 in which a resin with a low flexural modulus was used as the protective resin, light leakage due to scratches was observed here and there even when a colored protective layer was used.

10: single core POF, 12: core, 14: cladding layer, 16: protective layer, 20: multicore POF, 22: core, 24: cladding layer, 26: protective layer, 30: multicore POF, 32: core, 34: cladding layer, 36: protective layer.

Claims (9)

A core containing a polymethyl methacrylate resin, a cladding layer surrounding the core and having a refractive index lower than that of the core and containing a transparent fluororesin, and further outside the cladding layer a cladding layer having a refractive index lower than that of the cladding layer. Contains a protective layer containing high and transparent resin,
A plastic optical fiber, wherein the resin forming the protective layer has a bending elastic modulus of 1000 MPa or more and 4000 MPa or less. The plastic optical fiber according to claim 1, wherein the protective layer contains at least one selected from the group consisting of acrylic resin, polyolefin resin, polyester resin, and polyamide resin. the protective layer contains a colorant,
The plastic optical fiber according to claim 1 or 2, wherein the content of the colorant is 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the resin forming the protective layer. 4. A plastic optical fiber according to claim 3, wherein the colorant is a black pigment or a black dye. The plastic optical fiber according to any one of claims 1 to 4, wherein the transparent fluororesin contained in the cladding layer has a refractive index of 1.35 or more and 1.48 or less when measured at 20° C. with sodium D line. . Optical fiber illumination, in which at least one end of the plastic optical fiber according to any one of claims 1 to 5 is connected to a light source. An optical fiber fabric comprising at least a portion of the plastic optical fiber according to any one of claims 1 to 5. An optical fiber knitted fabric comprising at least a portion of the plastic optical fiber according to any one of claims 1 to 5. A method for manufacturing a side-emitting plastic optical fiber, comprising the steps of forming the plastic optical fiber according to any one of claims 1 to 5, and sandblasting the plastic optical fiber.