Polymer optical fiber

Abstract

Polymer optical fibers comprising a polyamide core are described herein. The polyamide core typically comprises one or more nylon polymers and is microcrystalline. The POF may have an operating temperature exceeding 150 DEG C and a calculated numerical aperture (NA) of 0.6 or greater.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 394,695, filed on August 3, 2022, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present application relates to a polymer optical fiber and a method for manufacturing the polymer optical fiber, which can be applied in various fields. Background Art

[0004] Optical fibers are used to transmit light from one end of the fiber to the other end of the fiber; they are suitable, for example, for optical communications, which allow transmission over longer distances and at higher bandwidths than cables. Optical fibers are also used for lighting and imaging, and in the case of optical sensors and fiber lasers.

[0005] The composition of such optical fibers is variable. Typically, optical fibers contain glass (silicon dioxide) and / or plastic materials. In particular, some optical fibers contain a polymer core and a polymer cladding. For example, EP0472384A2 describes polymer optical fibers having a plurality of monomers that can be used to make a polymer core of an optical fiber. JPH08304639A discloses a polymer optical fiber having a matrix of a non-crystalline fluoropolymer, substantially free of CH bonds. JP3059147B2 provides an optical fiber for optical communications by polymerization of a halogenated polyamideimide (with reference to the necessity of avoiding the use of polymers having CH bonds for optical waveguides, since these bonds strongly absorb light in the near infrared region). US7,058,271 discloses an optical fiber comprising a core made of a plurality of polymers, including acrylic polymers, polystyrene, polynorbornene, polycarbonate, polyimide and polyester. An exemplary polymer optical fiber is the Mitsubishi Eska SK-20 optical 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 the Hitachi HPOF optical fiber, which has a silicone core and a FEP cladding, and has an MOT of 150° C.

[0006] Optical fibers comprising polyamide coatings are known. See, for example, Sapozhnikov et al., "Heat-Resistant Polymeric coatings of Optical Fibers", Polymer Science, Series C, 62, 165-171, 2020. Trogamid CX polyamide resin is currently used as an optical material for making lenses, i.e., for applications with relatively short optical lengths where attenuation is not a problem. However, polyamide has not been used in the core of optical fibers to date; the core typically comprises silica or PMMA, such as that contained in Mitsubishi and Hitachi optical fibers as described above.

[0007] There continues to be a need for a polymer optical fiber (POF) that can operate at elevated temperatures in harsh chemical environments (eg, during sterilization procedures), including but not limited to the temperatures required to deposit a cladding thereon. Summary of the invention

[0008] The present invention provides optical fibers, methods of making such optical fibers, and methods of using optical fibers. According to various embodiments, the present invention provides an optical fiber comprising, or made using, a material operable in a temperature range of 150°C to 170°C, having excellent chemical resistance, particularly to hydrocarbons, alcohols, phenols, and lipids. In addition, the optical fibers provided herein according to various embodiments can advantageously maintain a large numerical aperture (NA) in elevated temperatures and harsh chemical environments. In some embodiments, CX polyamide resin is used as the core material of optical fiber by carefully processing the material.

[0009] The present invention includes, but is not limited to, the following embodiments.

[0010] Embodiment 1: A polymer optical fiber (POF) comprising: a core comprising one or more polyamides; and a cladding comprising one or more fluoropolymers, wherein the POF has an operating temperature exceeding 150°C and a calculated numerical aperture (NA) of 0.6 or greater.

[0011] Embodiment 2: The POF according to Embodiment 1, wherein the one or more polyamides comprise microcrystalline polyamide.

[0012] Embodiment 3: The POF according to Embodiment 1, wherein the one or more polyamides consist essentially of microcrystalline polyamide.

[0013] Embodiment 4: The POF according to any one of Embodiments 1-3, wherein the one or more polyamides comprise transparent polyamides.

[0014] Embodiment 5: The POF according to Embodiment 4, wherein the one or more polyamides consist essentially of transparent polyamide.

[0015] Embodiment 6: The POF according to any one of Embodiments 1-5, wherein the one or more polyamides comprises nylon.

[0016] Embodiment 7: The POF according to Embodiment 6, wherein the one or more polyamides consist essentially of nylon.

[0017] Embodiment 8: The POF according to any one of Embodiments 1-7, wherein the one or more polyamides comprise a polymer containing a cycloaliphatic diamine and 1,12-dodecanedioic acid monomers.

[0018] Embodiment 9: The POF of Embodiment 8, wherein the one or more polyamides consist essentially of a polymer containing cycloaliphatic diamine and 1,12-dodecanedioic acid monomers.

[0019] Embodiment 10: A POF according to any one of Embodiments 1-9, wherein the one or more polyamides comprise CX Polyamide.

[0020] Embodiment 11: The POF according to Embodiment 10, wherein the one or more polyamides consist essentially of CX polyamide composition.

[0021] Embodiment 12: The POF according to any of Embodiments 1-11, wherein the core consists essentially of the one or more polyamides.

[0022] Embodiment 13: The POF according to any one of Embodiments 1-11, wherein the core further comprises one or more additives.

[0023] Embodiment 14: The POF according to Embodiment 13, wherein the one or more additives comprise a refractive index modifier.

[0024] Embodiment 15: A POF according to 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-alternate-ethylene (ETFE), a copolymer of tetrafluoroethylene and perfluoromethyl vinyl ether (MFA), a copolymer of perfluoro(alkyl vinyl ether) (PFE), and copolymers, compositions and derivatives thereof.

[0025] Embodiment 16: The POF according to any one of Embodiments 1-15, wherein the cladding layer consists essentially of fluoropolymer material.

[0026] Embodiment 17: The POF according to any one of Embodiments 1-16, wherein the cladding further comprises one or more additives.

[0027] Embodiment 18: The POF according to any one of Embodiments 1-17, consisting essentially of the core and the cladding.

[0028] Embodiment 19: A method of making the POF according to any one of Embodiments 1-18, comprising extruding the cladding onto the core.

[0029] Embodiment 20: A method of manufacturing the POF according to any one of Embodiments 1-18, comprising applying the cladding to the core, and heat-shrinking the cladding on the core.

[0030] These and other features, aspects and advantages of the present invention will become apparent by reading the following detailed description and the accompanying drawings briefly described below. The present invention 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 set forth in the present invention, regardless of whether such features or elements are explicitly combined in the specific embodiment description herein. The present invention is intended to be read as a whole so that any separable features or elements of the disclosed invention should be considered to be combinable in any of its different aspects and embodiments, unless the context clearly specifies otherwise. DETAILED DESCRIPTION

[0031] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the invention are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments described herein; rather, these embodiments are provided so that the invention will satisfy applicable legal requirements. Like reference numerals refer to like elements throughout.

[0032] The present invention provides a polymer optical fiber (POF) having a core and cladding structure, wherein the core comprises polyamide. According to the present invention, the inventors have found that materials comprising certain polyamides can be uniquely selected in combination with different cladding materials for use in the core of the POF to provide the POF with desired properties, as further described below.

[0033] As mentioned above, the core of the disclosed POF uniquely comprises a polyamide. The term "polyamide" generally includes polymers having repeating units connected by amide (-CO-NH) units. A wide range of polyamides are known, including but not limited to different nylons (aliphatic polyamides) and polyaramids (aromatic polyamides). It is generally known that the properties of such polyamides are widely variable, depending on, for example, the distance between adjacent amide units, the composition between adjacent amide units, etc. The composition and corresponding physical properties of polyamides are very similar, and the present invention describes in part the identification and use of polyamides suitable for POF cores.

[0034] In some embodiments, suitable polyamides are crystallizable polyamides, such as crystallizable nylons (i.e., aliphatic polyamides). Advantageously, in preferred embodiments, the crystallites of the crystallizable polyamides are so small that they do not scatter visible light. Therefore, in such embodiments, the crystallizable polyamides are transparent to the human eye (i.e., the polyamides exhibit "microcrystallinity"). Although not intended to be limited by theory, it is believed that the microcrystalline structure of certain polyamides imparts various beneficial properties to the formed POF core, such as the types of properties that can be generated by crystallinity, including but not limited to stress crack resistance and limited to the absence of visual turbidity in the material. It should be noted that in preferred embodiments, the crystallinity ratio is low enough so as not to negatively affect the shrinkage behavior of the core (i.e., the isotropic shrinkage behavior typically observed in amorphous materials is advantageously substantially retained in crystallizable polyamides).

[0035] Suitable polyamides for the purposes described herein generally exhibit good optical properties. For example, in some embodiments, they can exhibit high clarity and high transmittance. In some embodiments, they exhibit high UV resistance.

[0036] In some embodiments, suitable polyamides are transparent or substantially transparent. In some embodiments, suitable polyamides may be characterized as "permanently transparent". In some embodiments, "permanently transparent" means that the material maintains its transparency (e.g., based on visual observation) over an extended period of time, such as two months or longer, six months or longer, one year or longer, two years or longer, three years or longer, four years or longer, five years or longer, ten years or longer, 20 years or longer, or 50 years or longer. In some embodiments, "permanently transparent" means that the material maintains its transparency (e.g., based on visual observation) under a wide range of conditions (e.g., up to and exceeding 200°C, 300°C, 400°C, 500°C, or 600°C). In some embodiments, "permanently transparent" as mentioned herein includes (at least) visual transparency under the conditions expected of the material and within the expected life of the material. For example, the core provided herein may be described as "permanently transparent" for use under the conditions under which the optical fiber is to be used (which may include elevated temperatures, elevated pressures, exposure to corrosive chemicals, etc.).

[0037] CX is an example of a crystallizable and permanently transparent polyamide. CX comprises a cycloaliphatic diamine and dodecanoic acid monomer units. This material (which is described in further detail, for example, at trogamid.com (last visited on July 24, 2023), which is incorporated herein by reference in its entirety) comprises crystallites so small that they do not scatter visible light, thereby achieving high transparency and permanent transparency, high transmittance (e.g. 92%), outstanding chemical resistance and stress cracking resistance, high dynamic strength (number of load cycles), very high toughness (even at low temperatures), wear and scratch resistance and / or very low isotropic shrinkage.

[0038] In general, unlike other polymers commonly used in POF, polyamides exhibit strong absorption peaks in the NIR region of the spectrum due to NH bond stretching (see Table 1 below, from: HAMahdi, J. Pure and Appl. Sci., 24, 1, 2011, incorporated herein by reference). Surprisingly, when processed into a POF form (as a core material), the polyamides provided herein transmit visible light without significant absorption near the red end of the spectrum. In fact, when compared to other polyamides such as nylon 6, nylon 6,6, nylon 4,6, nylon 11, nylon 6,11 and nylon 6,12, this material (e.g. Polyamide) has an absorbance of more than 3000 cm at the infrared end of the spectrum. -1, with relatively weak NH stretching bands. See M. Enlow, JL Kennedy, AA Nieuwland, JE Hendrix, SL Organ, Applied Spectroscopy, 59, 986-992, 2005, which is incorporated herein by reference in its entirety. In this way, The properties of bring it more closely into line with the amine-free materials currently used as POF cores, such as PMMA. See G. Vijayakumari, N. Selvakumar, K. Jeyasubramanian, R. Mala, Physics Procedia, 49, 67-78, 2013, which is incorporated herein by reference in its entirety.

[0039] Table (1): Pure nylon 6,6 FTIR spectrum assignment

[0040] <![CDATA[Wave number (cm -1 )]]> Absorbance Assignment 3410 0.34 NH Stretch I 3306 0.38 NH Stretch II 3082 0.18 CH stretching (asymmetric) 2932 0.28 <![CDATA[CH2 stretching (asymmetric)]]> 2862 0.25 <![CDATA[CH2 stretching (symmetric)]]> 1639 0.53 Amide I stretching 1539 0.46 <![CDATA[Amide II stretch / CH2 (asymmetric)]]> 1469 0.31 <![CDATA[N-H deformation / CH2 cleavage]]> 1269 0.34 Amide III stretching 1200 0.29 <![CDATA[CCH bending (symmetric) / CH2 twisting]]> 934 0.17 CC Stretch 691 0.20 CC Bending 579 0.18 CC Deformation

[0041] The cores comprising polyamide materials described herein may comprise, consist essentially of, or consist of a selected polyamide. In some embodiments, the core may comprise a small amount 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 components (additives) intentionally added thereto, for example, including but not limited to refractive index enhancers.

[0042] The cladding material of POF provided herein can change, and can be any conventional cladding material.Although not limited to this, cladding generally comprises a material with a lower refractive index than the material of core.In some embodiments, the cladding material is a fluoropolymer material.In some embodiments, the cladding comprises poly (tetrafluoroethylene-co-hexafluoropropylene) (FEP), EFEP (terpolymer comprising ethylene, tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) monomers), polytetrafluoroethylene-alternating-ethylene (ETFE), tetrafluoroethylene and perfluoromethyl vinyl ether copolymer (MFA), perfluoro (alkyl vinyl ether) copolymer (PFE), and copolymers, compositions and derivatives thereof.In some embodiments, the cladding material is applied as a heat shrink material (such as FEP) and heat shrinks on the core.

[0043] In some embodiments, the cladding consists essentially of the cladding material (e.g., a fluoropolymer). Among other components, the cladding may further include one or more additives. Exemplary additives include, but are not limited to, radiopaque fillers (e.g., barium sulfate and / or bismuth trioxide).

[0044] Advantageously, the core and cladding of the disclosed POFs do not exhibit significant delamination as determined by peel tests known in the art.

[0045] In some embodiments, the POF provided herein may include additional components. For example, one or more sheaths and / or buffer layers as generally known in the art may cover the cladding, for example to protect the core and cladding. In some embodiments, the POF provided herein may have a fairly high operating temperature (even in the absence of a covered sheath and / or buffer layer). In some embodiments, the POF may have an operating temperature exceeding 150°C, exceeding 155°C, or exceeding 160°C, for example, about 150°C-about 180°C or about 150°C-about 170°C. It should be noted that, in some embodiments, the POF provided herein may exhibit even higher operating temperatures, for example, when coated with a suitable sheath and / or buffer layer.

[0046] The POF provided herein can exhibit good physical properties / technical attributes, such as, but not limited to, numerical aperture ("NA") and critical angle of total internal reflection ("θ"), c ”), which makes the disclosed POF good for various optical fiber applications. In some embodiments, the POF herein exhibits a calculated NA value of about 0.4 or greater, about 0.5 or greater, or about 0.6 or greater. NA can be determined by the total internal reflection angle calculated using Snell's law. FEP (ri1.34) Trogamid CX (ri1.51) - critical angle at θ30° is 62.55°, i limit is 70.66°, θmax is 44.11°, NA = 0.696.

[0047] As a non-limiting demonstration of the types of values ​​exhibited by the disclosed POFs, a polyamide comprising microcrystalline polyamide (e.g. CX) and EFEP cladding. The numerical aperture ("NA") is defined as the sine of the maximum angle an incident ray can have for total internal reflection in the core (as shown below). A higher core refractive index relative to the cladding produces a larger NA value. The theoretical NA is calculated based on the following formula:

[0048]

[0049] The refractive index of EFEP is about 1.40, and The refractive index of is about 1.52, which gives the theoretical NA of the demonstrated POF to be about 0.60. In some embodiments, a POF is provided having a calculated numerical aperture of 0.6 or greater.

[0050] The critical angle of total internal reflection (θ c ) is given by:

[0051]

[0052] For EFEP and For a representative POF, θ c The theoretical value of is therefore about 67°. These results will depend on the exact resin grade used and the processing conditions.

[0053] Optical fiber provided herein can be prepared according to conventional methods. In some embodiments, POF is drawn from a fiber preform comprising the desired material. In some embodiments, POF is prepared by extruding selected core and cladding materials (independently or simultaneously). In some embodiments, POF is prepared by coating the core with a heat shrinkable cladding material and heat shrinking the cladding material.

[0054] The size and core of POF provided herein: cladding ratio can vary widely, and the principle outlined herein is applicable to a wide range. In some embodiments, the diameter of the core can be up to about 1mm. In some embodiments, POF provided herein is therefore considered to be a "large core" POF. In some embodiments, the diameter of the core is about 100-about 2000 microns, and the thickness of the cladding is also about 100-about 2000 microns.

[0055] POF provided herein can be used for various applications, such as any application of conventional use of POF. For example, they can be used for optical data transmission (such as in industrial environments, automotive industry, aircraft industry, consumer markets, digital home appliance interfaces and home and car networks) and for lighting purposes.

[0056] Example

[0057] Various embodiments of the present invention can be more fully illustrated by the following non-limiting examples.

[0058] Example 1. The CX polyamide resin was dried to a moisture content of less than 0.1% and extruded into 0.022 inch diameter filaments using a single screw extruder equipped with a 0.708 inch mixing screw with a length to diameter ratio (L / D) of 24:1. The EFEP cladding was then extruded onto the extruder by feeding the core through an extrusion head and a die / mandrel assembly. on a monofilament core. The target wall thickness of the EFEP cladding was 0.005 inches. The resulting fiber showed good adhesion between the core and cladding and good clarity.

[0059] Example 2. The CX polyamide resin was dried to a moisture content of less than 0.1%. A single screw extruder equipped with a 0.75 inch mixing screw and 24:1 L / D was used to extrude the inner layer. EFEP was extruded as the outer layer using a single screw extruder equipped with a 0.75" mixing screw and 24:1 L / D. The inner and outer layers were extruded simultaneously using a coextrusion crosshead to produce a solid inner layer of 0.018" diameter and an outer layer thickness of 0.001".

[0060] Example 3. Using the The monofilament core and FEP are heat shrunk to create discrete lengths of optical fiber. The FEP heat shrink tubing was manually fed over the length of the core. The FEP heat shrink was then recovered using a heat gun to fit tightly around the core. The resulting optical fiber showed good adhesion between the core / cladding and good clarity.

[0061] Those skilled in the art to which the present invention belongs who have the benefit of the foregoing description will be able to conceive of many modifications and other embodiments of the present invention. Therefore, it should be understood that the present invention is not limited to the specific embodiments disclosed, and modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used only in a general and descriptive sense and not for limiting purposes.

Claims

1. A polymer optical fiber (POF), comprising: a core comprising one or more polyamides; and A cladding layer comprising one or more fluoropolymers, Wherein the POF has an operating temperature exceeding 150° C. and a calculated numerical aperture (NA) of 0.6 or greater. 2 . The POF according to claim 1 , wherein the one or more polyamides comprise microcrystalline polyamide.

3. The POF according to claim 1, wherein the one or more polyamides consist essentially of microcrystalline polyamide. The POF according to claim 1 , wherein the one or more polyamides comprise transparent polyamide.

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

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

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

8. The POF according to any one of claims 1 to 7, wherein the one or more polyamides comprise a polymer containing a cycloaliphatic diamine and 1,12-dodecanedioic acid monomers.

9. The POF according to any one of claims 1 to 7, wherein the one or more polyamides consist essentially of a polymer containing cycloaliphatic diamine and 1,12-dodecanedioic acid monomers.

10. The POF according to claim 1, wherein the one or more polyamides comprise CX Polyamide.

11. The POF according to claim 1, wherein the one or more polyamides consist essentially of CX polyamide composition.

12. The POF according to any one of claims 1-11, wherein the core consists essentially of the one or more polyamides.

13. The POF according to any one of claims 1-11, wherein the core further comprises one or more additives.

14. The POF according to claim 13, wherein the one or more additives comprise a refractive index modifier.

15. The POF according to any one of claims 1 to 14, wherein the one or more fluorine-containing polymers are selected from poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), EFEP (a terpolymer comprising ethylene, tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) monomers), polytetrafluoroethylene-alternative-ethylene (ETFE), a copolymer of tetrafluoroethylene and perfluoromethyl vinyl ether (MFA), a copolymer of perfluoro(alkyl vinyl ether) (PFE), and copolymers, combinations and derivatives thereof.

16. The POF according to any one of claims 1-15, wherein the cladding consists essentially of fluoropolymer material.

17. The POF according to any one of claims 1 to 15, wherein the cladding further comprises one or more additives.

18. The POF according to any one of claims 1 to 17, consisting essentially of the core and the cladding.

19. A method of making the POF of any one of claims 1 to 18, comprising extruding the cladding onto the core.

20. A method of making the POF of any one of claims 1 to 18, comprising applying the cladding to the core, and heat shrinking the cladding on the core.

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