polymer optical fiber

Abstract

Described herein is a polymer optical fiber (POF) having a polyamide core. The polyamide core generally comprises one or more nylon polymers and is microcrystalline. The described POF can have an operating temperature greater than 150°C and a calculated numerical aperture greater than or equal to 0.6.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 394,695, filed August 3, 2022, the entire disclosure of which is incorporated herein by reference in its entirety.

[0002] FIELD OF THE INVENTION This application relates to polymer optical fibers for various applications and methods for making such polymer optical fibers. [Background technology]

[0003] Optical fibers are fibers useful for transmitting light from one end of the fiber to the other, and are applicable, for example, to optical communications, allowing transmission over longer distances and at higher bandwidths than electrical cables. Optical fibers are also used in lighting and imaging, as well as in optical sensors and fiber lasers.

[0004] The composition of such optical fibers can vary. Optical fibers often contain glass (silica) and / or plastic materials. In particular, some optical fibers contain a polymer core and a polymer cladding. For example, U.S. Patent No. 6,299,496 describes polymer optical fibers containing various monomers that can be used to manufacture the polymer core of the fiber. U.S. Patent No. 6,299,496 discloses a polymer optical fiber having a matrix of an amorphous fluoropolymer substantially free of C-H bonds. U.S. Patent No. 6,299,496 provides an optical fiber based on the polymerization of halogenated polyamideimide for use in optical communications (noting that polymers containing C-H bonds should be avoided for optical conduits because these bonds strongly absorb light in the near-infrared region). U.S. Patent No. 6,299,496 discloses optical fibers containing cores made from various polymers, including acrylic polymers, polystyrene, polynorbornene, polycarbonate, polyimide, and polyester. One exemplary polymer optical fiber is Mitsubishi Chemical Corporation's Eska SK-20 Fiber, which has a poly(methyl methacrylate) (“PMMA”) core and a fluorinated ethylene propylene (“FEP”) cladding and has a maximum operating temperature (MOT) of 70° C. Another example of an optical fiber is Hitachi, Ltd.'s HPOF Fiber, which has a silicone core and a FEP cladding and has a MOT of 150° C.

[0005] Optical fibers with polyamide coatings are also known. See, for example, "Trogamid CX Polyamide Resin," IEEE Transactions on Optical Fiber Engineering, Vol. 1, No. 1, pp. 111-114, 2003. Trogamid CX polyamide resin is currently used as an optical material for lens manufacturing, i.e., for applications with relatively short optical lengths where attenuation is not an issue. However, polyamide has not previously been used for the core of optical fiber. Cores have traditionally contained silica or PMMA, as contained, for example, in the optical fibers of Mitsubishi Chemical Corporation and Hitachi, Ltd., mentioned above. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] European Patent Application Publication No. 0472384 [Patent Document 2] Japanese Patent Application Publication No. 8304639 [Patent Document 3] Patent No. 3059147 [Patent Document 4] U.S. Patent No. 7,058,271 [Non-patent literature]

[0007] [Non-Patent Document 1] Sapozhnikov et al., "Heat-Resistant Polymeric coatings of Optical Fibers", Polymer Science, Series C, 62, 165-171, 2020 Summary of the Invention [Problem to be solved by the invention]

[0008] There is a continuing need for polymer optical fibers (POFs) that can operate in harsh chemical environments (e.g., during sterilization procedures) at elevated temperatures, including, but not limited to, the temperatures required to deposit cladding layers. [Means for solving the problem]

[0009] The present disclosure provides optical fibers, methods for making such optical fibers, and methods for using optical fibers. According to various embodiments, the present disclosure provides optical fibers comprising or made with materials that have excellent chemical resistance, particularly to hydrocarbons, alcohols, phenols, and lipids, and that can operate at temperatures ranging from 150°C to 170°C. Furthermore, the optical fibers provided herein, according to various embodiments, can advantageously maintain a large numerical aperture (NA) at high temperatures and in harsh chemical environments. In some embodiments, TROGAMID™ CX polyamide resin is used as the core material of optical fibers through careful processing of the material.

[0010] The present disclosure includes, but is not limited to, the following embodiments. Embodiment 1: A polymer optical fiber (POF) comprising a core comprising one or more polyamides and a cladding comprising one or more fluoropolymers, the POF having an operating temperature greater than 150°C and a calculated numerical aperture (NA) of 0.6 or greater. Embodiment 2: The POF of embodiment 1, wherein the one or more polyamides include microcrystalline polyamide. Embodiment 3: The POF of embodiment 1, wherein the one or more polyamides consist essentially of microcrystalline polyamide. Embodiment 4: The POF according to any one of embodiments 1 to 3, wherein the one or more polyamides include a transparent polyamide. Embodiment 5: The POF of embodiment 4, wherein the one or more polyamides consist essentially of transparent polyamides. Embodiment 6: The POF according to any one of embodiments 1 to 5, wherein the one or more polyamides include nylon. Embodiment 7: The POF of embodiment 6, wherein the one or more polyamides consist essentially of nylon. Embodiment 8: The POF of any one of embodiments 1 to 7, wherein the one or more polyamides comprise a polymer comprising an alicyclic diamine and a 1,12-dodecanedioic acid monomer. Embodiment 9: The POF of embodiment 8, wherein the one or more polyamides consist essentially of a polymer comprising a cycloaliphatic diamine and a 1,12-dodecanedioic acid monomer. Embodiment 10: The POF of any one of embodiments 1 to 9, wherein the one or more polyamides include TROGAMID™ CX polyamide. Embodiment 11: The POF of embodiment 10, wherein the one or more polyamides consist essentially of TROGAMID™ CX polyamide. Embodiment 12: The POF according to any one of embodiments 1 to 11, wherein the core consists essentially of one or more polyamides. Embodiment 13: The POF of any one of embodiments 1 to 11, wherein the core further comprises one or more additives. Embodiment 14: The POF of embodiment 13, wherein the one or more additives include a refractive index adjuster. Embodiment 15: A POF described in any one of embodiments 1 to 14, wherein the cladding comprises one or more fluoropolymers selected from the group consisting of poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), EFEP (a terpolymer comprising ethylene, tetrafluoroethylene (TFE), and hexafluoropropylene (HFP) monomers), polytetrafluoroethylene-alt-ethylene (ETFE), copolymers of tetrafluoroethylene and perfluoromethyl vinyl ether (MFA), copolymers of perfluoro(alkyl vinyl ether) (PFE), and copolymers, combinations, and derivatives thereof. Embodiment 16: The POF according to any one of embodiments 1 to 15, wherein the cladding consists essentially of a fluoropolymer material. Embodiment 17: The POF according to any one of embodiments 1 to 16, wherein the cladding further comprises one or more additives. Embodiment 18: The POF according to any one of embodiments 1 to 17, consisting essentially of a core and a cladding. Embodiment 19: A method for manufacturing a POF according to any one of embodiments 1 to 18, comprising extruding a cladding onto a core. Embodiment 20: A method for manufacturing a POF according to any one of embodiments 1 to 18, comprising applying a cladding onto a core and heat-shrinking the cladding onto the core.

[0011] These and other features, aspects, and advantages of the present disclosure will become apparent from the following detailed description read in conjunction with the accompanying drawings, which are briefly described below. The present invention also includes any combination of two, three, four, or more of the above-described embodiments, as well as any combination of two, three, four, or more features or elements described in this disclosure, regardless of whether such features or elements are specifically combined in the description of a specific embodiment herein. The present disclosure is intended to be read holistically, and therefore in any of its various aspects and embodiments, it is to be understood that any separable features or elements of the disclosed invention are intended to be combinable, unless the context clearly dictates otherwise. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention is described in more detail below with reference to the accompanying drawings, some, but not all, of which embodiments are shown. Indeed, these inventions may be embodied in many different forms and are not to be construed as limited to the embodiments set forth herein. Rather, these embodiments are presented so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0013] The present disclosure provides a polymer optical fiber (POF) having a core and cladding structure, wherein the core comprises a polyamide. In accordance with the present disclosure, the inventors have discovered that certain polyamide-containing materials can be uniquely selected for use in the core of the POF in combination with various cladding materials to impart desired properties to the POF, as further described herein below.

[0014] As mentioned hereinabove, the core of the disclosed POF uniquely comprises a polyamide. The term "polyamide" generally encompasses polymers having repeating units linked by amide (-CO-NH) units. A wide variety of polyamides are known, including, but not limited to, various nylons (aliphatic polyamides) and aramids (aromatic polyamides). It is generally known that the properties of such polyamides vary widely, depending, for example, on the distance between adjacent amide units, the composition between adjacent amide units, etc. Polyamides vary in both composition and corresponding physical properties, and this disclosure will, in part, describe the identification and use of polyamides suitable for application in the context of POF cores.

[0015] In some embodiments, a suitable polyamide is a crystalline polyamide, such as crystalline nylon (i.e., an aliphatic polyamide). Advantageously, in preferred embodiments, the crystallites of the crystalline polyamide are small enough not to scatter visible light. Thus, the crystalline polyamide of such embodiments appears transparent to the human eye (i.e., the polyamide exhibits "microcrystalline" properties). Without intending to be limited by theory, it is believed that the microcrystalline structure of certain polyamides imparts various beneficial properties to the resulting POF core, including, but not limited to, stress crack resistance and the absence of visual cloudiness of the material, the type of properties that can result from crystallinity. Note that in preferred embodiments, the crystalline fraction is sufficiently low so as not to adversely affect the shrinkage behavior of the core (i.e., the isotropic shrinkage behavior typically observed in amorphous materials is advantageously substantially preserved in crystalline polyamides).

[0016] Polyamides suitable for the purposes described herein generally exhibit good optical properties. For example, in some embodiments, polyamides can exhibit high transparency and high transmittance. In some embodiments, polyamides exhibit high UV resistance.

[0017] In some embodiments, suitable polyamides are transparent or substantially transparent. In some embodiments, suitable polyamides may be characterized as "permanently transparent." "Permanently transparent" means, in some embodiments, that the material maintains its transparency (e.g., based on visual observation) for an extended period of time, such as for 2 months or more, 6 months or more, 1 year or more, 2 years or more, 3 years or more, 4 years or more, 5 years or more, 10 years or more, 20 years or more, or 50 years or more. In some embodiments, "permanently transparent" indicates that the material maintains its transparency (e.g., based on visual observation) under a wide range of conditions (e.g., temperatures up to and exceeding 200°C, 300°C, 400°C, 500°C, or 600°C). In some embodiments, references herein to "permanently transparent" encompass visual transparency (at least) under the conditions and lifetime intended for the material. For example, the cores provided herein may be described as "permanently transparent" for use under conditions in which optical fibers are used (which may include high temperatures, high pressures, exposure to corrosive chemicals, etc.).

[0018] TROGAMID™ CX is an example of a crystalline, permanently transparent polyamide. TROGAMID™ CX contains monomer units of a cycloaliphatic diamine and dodecanoic acid. This material, described in more detail, for example, at trogamid.com (last accessed July 24, 2023; incorporated herein by reference in its entirety), contains crystallites small enough not to scatter visible light, thereby achieving high clarity and permanent transparency, and has high transmittance (e.g., 92%), excellent chemical and stress crack resistance, high dynamic strength (number of load cycles), very high toughness even at low temperatures, abrasion and scratch resistance, and / or very low isotropic shrinkage.

[0019] Generally, unlike other polymers commonly used in POFs, polyamides exhibit a strong absorption peak toward the NIR region of the spectrum due to N-H bond stretching (see Table 1 below from H.A. Mahdi, J. Pure and Appl. Sci., 24, 1, 2011; incorporated herein by reference). Surprisingly, the polyamides provided herein, when processed into the form of a POF (as a core material), transmit visible light without significant absorption near the red end of the spectrum. Indeed, the absorbance at the infrared end of the spectrum of such materials (e.g., TROGAMID™ polyamides) has a relatively weak N-H stretching band compared to other polyamides, such as nylon 6, nylon 6,6, nylon 4,6, nylon 11, nylon 6,11, and nylon 6,12, with a peak at 3000 cm. -1 amine-containing materials currently used as the core of POFs, such as PMMA. See G. Vijayakumari, N. Selvakumar, K. Jeyasubramanian, R. Mala, Physics Procedia, 49, 67-78, 2013 (incorporated herein by reference in its entirety).

[0020] [Table 1]

[0021] Cores comprising the polyamide materials described herein can comprise, consist essentially of, or consist of selected polyamide(s). In some embodiments, the core may contain small amounts of stabilizers or other components (e.g., contained in the polyamide resin obtained and processed to form the disclosed core). In other embodiments, the core may contain one or more additional intentionally added components (additives), including, but not limited to, refractive index increasing agents.

[0022] The cladding material of the POF provided herein can vary and can be any conventional cladding material. Without limitation, the cladding typically comprises a material having a lower refractive index than the core material. In some embodiments, the cladding material is a fluoropolymer material. In some embodiments, the cladding comprises poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), EFEP (a terpolymer comprising ethylene, tetrafluoroethylene (TFE), and hexafluoropropylene (HFP) monomers), polytetrafluoroethylene-alt-ethylene (ETFE), copolymers of tetrafluoroethylene and perfluoromethyl vinyl ether (MFA), copolymers of perfluoro(alkyl vinyl ether) (PFE), and copolymers, combinations, and derivatives thereof. In some embodiments, the cladding material is applied as a heat shrink material (e.g., FEP) and heat shrunk onto the core.

[0023] In some embodiments, the cladding consists essentially of the cladding material (e.g., a fluoropolymer). In other compositions, the cladding can further include one or more additives. Exemplary additives include, but are not limited to, radiopaque fillers (e.g., barium sulfate and / or bismuth trioxide).

[0024] Advantageously, the core and cladding layers of the disclosed POF do not exhibit substantial delamination, for example, as determined by peel tests known in the art.

[0025] In some embodiments, the POFs provided herein may include additional components. For example, to protect the core and cladding, the cladding may be covered with one or more jacket and / or buffer layers, e.g., as commonly known in the art. The POFs provided herein may, in some embodiments, have a moderately high operating temperature (even in the absence of an overlying jacket and / or buffer layer). In some embodiments, the POF may have an operating temperature greater than 150°C, greater than 155°C, or greater than 160°C, e.g., from about 150°C to about 180°C, or from about 150°C to about 170°C. It should be noted that in some embodiments, the POFs provided herein may exhibit even higher operating temperatures, e.g., when coated with suitable jacket and / or buffer layers.

[0026] The POFs provided herein may be configured with a variety of optical fibers, including, for example, a numerical aperture ("NA") and a critical angle for total internal reflection ("θ"). c」 The disclosed POFs can exhibit favorable physical / technical attributes, including, but not limited to, NA, making them suitable for a variety of optical fiber applications. In some embodiments, the POFs herein exhibit calculated NA values of about 0.4 or greater, about 0.5 or greater, or about 0.6 or greater. NA can be determined by the angle of total internal reflection calculated using Snell's law. FEP (ri 1.34) Trogamid CX (ri 1.51) - critical angle 62.55°, i limit at θ 30° 70.66°, θ max 44.11°, NA = 0.696.

[0027] As one non-limiting example of the types of values exhibited by the disclosed POF, a fiber comprising a microcrystalline polyamide (e.g., TROGAMID™ CX) and an EFEP cladding is provided. The numerical aperture ("NA") is defined as the sine of the largest angle an incident ray can have with respect to the total internal reflectance at the core (shown below). The higher the reflectivity of the core relative to the cladding, the higher the NA value. The theoretical NA is calculated based on the following formula:

number

[0028] The refractive index of EFEP is about 1.40 and the refractive index of TROGAMID™ is about 1.52, resulting in a theoretical NA of about 0.60 for the demonstrated POF. In some embodiments, a POF with a calculated numerical aperture of 0.6 or greater is provided.

[0029] The critical angle of total internal reflection (θ c ) is given by the following formula:

number

[0030] Therefore, in typical POFs including EFEP and TROGAMID™, θ c The theoretical value for is approximately 67°. These results will vary depending on the exact resin grade and processing conditions used.

[0031] The optical fibers provided herein can be fabricated according to conventional methods. In some embodiments, the POF is drawn from a fiber preform containing the desired materials. In some embodiments, the POF is fabricated by extruding selected core and cladding materials (independently or simultaneously). In some embodiments, the POF is fabricated by covering the core with a heat-shrink cladding material and heating the heat-shrink cladding material.

[0032] The size and core:cladding ratio of the POFs provided herein can vary widely, and the principles outlined herein are applicable across a wide range. In some embodiments, the core can have a diameter of up to about 1 mm. Thus, in some embodiments, the POFs provided herein are considered "large-core" POFs. In some embodiments, the core has a diameter of about 100 microns to about 2000 microns, and the cladding thickness also ranges from about 100 microns to about 2000 microns.

[0033] The POF provided herein can be used in a variety of applications, including any of the applications for which POF is traditionally used, such as optical data transmission (e.g., in industrial environments, the automotive industry, the aviation industry, the consumer market, digital appliance interfaces, and home and automotive networks) and lighting purposes. [Example]

[0034] Various embodiments of the present invention can be more fully demonstrated by the following non-limiting examples.

[0035] Example 1. TROGAMID™ CX polyamide resin was dried to a moisture level of less than 0.1% and extruded into a 0.022 inch diameter monofilament using a single screw extruder equipped with a 0.708 inch mixing screw with a length to diameter ratio (L / D) of 24:1. EFEP cladding was then extruded onto the TROGAMID™ monofilament core by feeding the core through an extrusion head and die / mandrel setup. The target wall thickness of the EFEP cladding was 0.005 inch. The resulting optical fiber exhibited good adhesion between the core and cladding and good clarity.

[0036] Example 2. TROGAMID™ CX polyamide resin was dried to a moisture level of less than 0.1%. TROGAMID™ was extruded as an inner layer using a 24:1 L / D single screw extruder equipped with a 0.75 inch mixing screw. EFEP was extruded as an outer layer using a 24:1 L / D single screw extruder equipped with a 0.75 inch mixing screw. The inner and outer layers were simultaneously extruded using a coextrusion crosshead to yield a solid inner layer diameter of 0.018 inches and an outer layer thickness of 0.001 inch.

[0037] Example 3. Individual lengths of optical fiber were fabricated using the TROGAMID™ monofilament core and FEP heatshrink of Example 1. FEP heatshrink tubing was manually applied over the entire length of the TROGAMID™ core. The FEP heatshrink was then restored to a snug fit around the core using a heat gun. The resulting optical fiber exhibited good core / cladding adhesion and good clarity.

[0038] Many variations and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing description. It is to be understood, therefore, that the invention is not to be limited to the specific embodiments disclosed, and that variations and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A polymer optical fiber (POF), a core comprising one or more polyamides; a cladding comprising one or more fluoropolymers; and having an operating temperature exceeding 150° C. and a calculated numerical aperture (NA) of 0.6 or greater.

2. The POF of claim 1 , wherein the one or more polyamides comprise a microcrystalline polyamide.

3. 10. The POF of claim 1, wherein the one or more polyamides consist essentially of microcrystalline polyamides.

4. The POF of claim 1 , wherein the one or more polyamides comprise a transparent polyamide.

5. 10. The POF of claim 1, wherein the one or more polyamides consist essentially of a transparent polyamide.

6. The POF according to any one of claims 1 to 5, wherein the one or more polyamides comprise nylon.

7. The POF according to any one of claims 1 to 5, wherein the one or more polyamides consist essentially of nylon.

8. 6. The POF according to claim 1, wherein the one or more polyamides comprise a polymer comprising an alicyclic diamine and a 1,12-dodecanedioic acid monomer.

9. 6. The POF according to claim 1, wherein the one or more polyamides consist essentially of a polymer comprising a cycloaliphatic diamine and a 1,12-dodecanedioic acid monomer.

10. 10. The POF of claim 1, wherein the one or more polyamides comprise TROGAMID™ CX polyamide.

11. 10. The POF of claim 1, wherein the one or more polyamides consist essentially of TROGAMID™ CX polyamide.

12. 6. The POF according to claim 1, wherein the core consists essentially of the one or more polyamides.

13. The POF according to any one of claims 1 to 5, wherein the core further comprises one or more additives.

14. 14. The POF of claim 13, wherein the one or more additives include a refractive index modifier.

15. 6. The POF according to any one of claims 1 to 5, wherein the one or more fluoropolymers are selected from the group consisting of poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), EFEP (a terpolymer comprising ethylene, tetrafluoroethylene (TFE), and hexafluoropropylene (HFP) monomers), polytetrafluoroethylene-alt-ethylene (ETFE), copolymers of tetrafluoroethylene and perfluoromethyl vinyl ether (MFA), copolymers of perfluoro(alkyl vinyl ether) (PFE), and copolymers, combinations, and derivatives thereof.

16. 6. The POF according to claim 1, wherein the cladding consists essentially of a fluoropolymer material.

17. The POF according to any one of claims 1 to 5, wherein the cladding further comprises one or more additives.

18. 6. The POF according to claim 1, consisting essentially of said core and said cladding.

19. A method for producing the POF according to any one of claims 1 to 5, comprising extruding a cladding onto a core.

20. A method for manufacturing the POF according to any one of claims 1 to 5, comprising applying a cladding onto a core and heat-shrinking the cladding onto the core.

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