Plastic optical fiber, woven fabric, and knitted fabric

Abstract

The present invention provides: a plastic optical fiber which has excellent light-emitting properties on a side surface when light is inputted and which has heat resistance; and a light-emitting woven fabric and knitted fabric which use the plastic optical fiber.　The present invention is a plastic optical fiber having a core and at least one layer of cladding. The resin used for the core is polymethyl methacrylate, and the glass transition point Tg of the polymethyl methacrylate is 115-130°C. The melting point of the resin used for the cladding in the outermost layer among the at least one layer of cladding is 150-200°C. The outer diameter of the plastic optical fiber is 50-300 μm. The thickness of the cladding of the outermost layer is 7.5-20.0 μm. An uneven shape is present on at least a portion of the surface of the plastic optical fiber. The exposure of the core in the portion where the uneven shape is present is 0-10%. The breaking strength of the plastic optical fiber as determined by a tensile test is 6.6-9.0 N.

Description

Plastic fiberglass, textiles and knitted fabrics

[0001] This invention relates to plastic optical fibers, particularly side-emitting plastic optical fibers, and their applications in woven and knitted fabrics.

[0002] Generally, plastic optical fibers used for optical transmission consist of a core (inner layer) and cladding (outer layer) made of transparent resin, arranged in a concentric circular shape. Because light incident from one end of a plastic optical fiber undergoes repeated total internal reflection at the interface between the core and cladding, it is efficiently transmitted to the other end. Therefore, it is effectively used as an optical transmission material for medical endoscopes, industrial applications, and automotive lighting. These optical fibers all serve as a means of transmitting light from one end to the other without any leakage along the way. On the other hand, if light can be leaked from the longitudinal direction (side) to function as a linear light emitter, its applications can be expanded to include indoor and outdoor lighting, neon signs and electronic displays, other decorative applications, and even sensor applications. As an optical fiber that emits light in the lateral direction, a method is known in which a light-scattering material is incorporated into either the core layer, the cladding layer, or both (see, for example, Patent Documents 1-2).

[0003] However, when light-scattering materials are incorporated into the core or cladding layer, excessive light leaks out to the sides, resulting in reduced brightness on the sides as the optical fiber length increases, and thus poor brightness uniformity.

[0004] Furthermore, a method is known for using plastic optical fibers for side emission by creating fine irregularities on the side surface of the optical fiber and irradiating light in the lateral direction (see, for example, Patent Document 3).

[0005] A common method for creating uneven surfaces is sandblasting (see, for example, Patent Document 4). However, when an uneven surface is formed on the cladding by sandblasting, the cladding may be removed, exposing the core. In plastic optical fibers, the cladding not only causes total internal reflection of light passing through the core but also protects the core from heat, moisture, etc. However, when the core is exposed, there is a problem in that the heat resistance is significantly reduced.

[0006] JP-A-6-118238 Patent No. 5341391 JP-A 54-163045 JP-A 11-84135

[0007] The present invention aims to provide a plastic optical fiber that exhibits excellent luminescence on its side when light is applied and is heat-resistant, as well as luminescent woven and knitted fabrics using the same.

[0008] The present invention and its preferred embodiments have the following configuration: [1] A plastic optical fiber having a core and at least one cladding layer, wherein the resin used for the core is polymethyl methacrylate, the glass transition temperature Tg of the polymethyl methacrylate is 115°C or higher and 130°C or lower, the melting point of the resin used for the outermost cladding layer of the at least one cladding layer is 150°C or higher and 200°C or lower, the outer diameter of the plastic optical fiber is 50 μm or higher and 300 μm or lower, the thickness of the outermost cladding layer of the at least one cladding layer is 7.5 μm or higher and 20.0 μm or lower, an uneven shape exists on at least a part of the surface of the plastic optical fiber, the exposure of the core in the part where the uneven shape exists is 0% or higher and 10% or lower, and the breaking strength of the plastic optical fiber by tensile testing is 6.6 N or higher and 9.0 N or lower.

[0009] [2] The plastic optical fiber according to [1], wherein the plastic optical fiber emits light from its side.

[0010] [3] The outermost cladding contains 10 to 35% by mass of ethylene, 45 to 69% by mass of tetrafluoroethylene, 20 to 45% by mass of hexafluoropropylene, and 0.01 to 10% by mass of a fluorovinyl compound represented by formula (1) as copolymer components, as described in [1] or [2]. ２ = CX １ (CF ２ )nX ２ Formula (1) In formula (1), X １ X is a fluorine atom or a hydrogen atom. ２ represents a fluorine atom, a hydrogen atom, or a hydrocarbon group, and n represents an integer from 1 to 10.

[0011] [4] A plastic optical fiber according to any one of [1] to [3], having another cladding layer in the inner layer of the outermost cladding layer.

[0012] [5] The plastic optical fiber according to any one of [1] to [4], wherein the maximum surface roughness Rz of the portion where the uneven shape exists is 3.0 μm or more and 7.0 μm or less.

[0013] [6] The plastic optical fiber according to any one of [1] to [5], wherein the surface irregular shape of the plastic optical fiber is obtained by removing a part of the outermost cladding.

[0014] [7] The plastic optical fiber according to any one of [1] to [6], wherein the surface irregularities are formed by a blast treatment.

[0015] [8] A fabric made using plastic optical fibers as described in any of [1] to [7].

[0016] [9] A knitted fabric made using plastic optical fibers as described in any of [1] to [7].

[0017] According to the present invention, it is possible to provide a plastic optical fiber that exhibits excellent luminescence on its sides when light is applied and is also heat-resistant, as well as a luminescent woven fabric and knitted fabric using the same.

[0018] The plastic optical fiber of the present invention (hereinafter also simply referred to as "optical fiber") has a core and at least one layer of cladding.

[0019] The resin used in the core is polymethyl methacrylate (PMMA). PMMA has excellent transparency.

[0020] The glass transition temperature (Tg) of the aforementioned polymethyl methacrylate is between 115°C and 130°C. PMMA is an amorphous polymer, and its Tg depends on its molecular weight. However, having a Tg within the above range results in an optical fiber with a good balance of properties such as spinnability and heat resistance during the spinning process of plastic optical fibers. A Tg of 115°C or higher provides sufficient heat resistance. Furthermore, a Tg of 130°C or lower improves spinnability.

[0021] The at least one cladding layer is formed on the outer circumference of the core and consists of an organic polymer having a refractive index smaller than that of the core.

[0022] A key feature is that the resin used in the outermost cladding layer of the at least one cladding layer has a melting point of 150°C or higher and 200°C or lower. When the melting point is 150°C or higher, a cladding layer with a higher melting point than the Tg (softening point) of the PMMA forming the core is formed, and the inner core is protected by the outermost cladding layer even in environments where the optical fiber is subjected to high temperatures, thereby improving the heat resistance of the plastic optical fiber. On the other hand, when the melting point is 200°C or lower, the temperature difference with the Tg (softening point) of the PMMA forming the core is appropriate, and it is possible to prevent bubbles caused by decomposition gases from being mixed into the core during spinning.

[0023] The outermost cladding layer of the at least one cladding layer is preferably made of a fluoropolymer resin, considering the difference in refractive index with the PMMA forming the core.

[0024] Among the aforementioned fluoropolymer resins, those containing 10-35% by mass of ethylene, 45-69% by mass of tetrafluoroethylene, 20-45% by mass of hexafluoropropylene, and 0-10% by mass of other copolymerizable components are preferred in terms of the balance between melting point and refractive index.

[0025] As the other copolymerizable component, a fluorovinyl compound represented by the formula (1) is preferable. By using the fluorovinyl compound, the plastic optical fiber of the present invention can obtain good heat resistance. CH ２ =CX １ (CF ２ ) ｎ X ２ Formula (1) In the formula (1), X １ is a fluorine atom or a hydrogen atom, X ２ represents a fluorine atom, a hydrogen atom or a hydrocarbon group, and n represents an integer of 1 to 10.

[0026] When using the fluorovinyl compound represented by the formula (1), the content rate as the copolymerization component is preferably 0.01 to 10% by mass.

[0027] The outer diameter of the plastic optical fiber is 50 μm or more and 300 μm or less. If the outer diameter is 50 μm or more, preferably 150 μm or more, more preferably 200 μm or more, the tensile strength of the optical fiber is sufficient, and breakage of the optical fiber during weaving work on an automatic loom can be suppressed. If the outer diameter is 300 μm or less, preferably 280 μm or less, more preferably 270 μm or less, the flexibility of the optical fiber is maintained, and curling of the fabric can be suppressed.

[0028] The thickness of the outermost clad layer is 7.5 μm or more and 20.0 μm or less. By having a clad thickness of 7.5 μm or more with respect to the outer diameter of the optical fiber of 300 μm or less, the heat resistance as an optical fiber is excellent. Also, even in a region where the clad thickness is thin due to the uneven shape on the surface of the optical fiber described later, the clad thickness is appropriately maintained in the concave portion of the uneven shape on the surface of the optical fiber, and it becomes possible to protect the core and suppress the exposure of the core portion. If the clad thickness is 20.0 μm or less, the ratio of the core is also appropriate, and the luminance of the side emission is sufficiently maintained.

[0029] The plastic optical fiber may also preferably have one or more additional cladding layers in the inner layer of the outermost cladding. In the present invention, whether or not there is an additional cladding layer can be determined by whether or not it is formed from a different component. The type of the additional cladding layer is not particularly limited, but it is preferable to use a polymer obtained by polymerizing a polymerization component containing 90% by mass or more of vinylidene fluoride, because a portion of it crystallizes, making it easier to emit light in the lateral direction of the plastic optical fiber.

[0030] The aforementioned plastic optical fiber has an uneven surface on at least a portion of its surface. Due to the presence of this uneven surface, some of the light passing through the interior of the optical fiber is emitted from the sides, causing the optical fiber to function as a side-emitting type.

[0031] As a method for forming the aforementioned uneven shape, for example, by forming unevenness on the entire surface of a plastic optical fiber during the spinning stage, it is possible to manufacture an optical fiber that emits light from its entire side surface.

[0032] Furthermore, if a surface treatment is applied after forming a woven or knitted fabric with optical fibers to remove a portion of the cladding only from the surface side of the fabric, an uneven shape is formed only on the side of the optical fiber exposed on the surface side of the fabric, causing side-emitting light, which is preferable because it allows for effective use of the light input to the optical fiber. In other words, it is preferable that the portion where the uneven shape exists corresponds to the portion that is exposed on the surface of the woven or knitted fabric when the optical fiber is made into a woven or knitted fabric.

[0033] Surface treatment methods that remove a portion of the cladding only from the surface side of a fabric or knitted fabric after forming it with optical fibers include, for example, blasting, sanding the surface of the fabric or knitted fabric, and heat treatment with laser light.

[0034] Among the methods of the surface treatment, the blasting treatment is preferable in terms of the uniformity of the treatment. The blasting treatment is a method of spraying fine particles onto an object by air pressure to roughen the surface of the object. The roughness of the surface of the object can be controlled by the type of the fine particles, the particle size, and the time for spraying the fine particles. Examples of the fine particles include silica, alumina, dry ice, etc., but the method is not limited in this patent.

[0035] It is preferable that the maximum roughness Rz of the surface of the portion where the uneven shape exists is 3.0 μm or more and 7.0 μm or less. When the maximum roughness Rz is 3.0 μm or more, the light emission in the lateral direction of the optical fiber increases. Also, if the maximum roughness Rz is 7.0 μm or less, the exposure ratio of the core described below is maintained at 10% or less, and the heat resistance is maintained.

[0036] The exposure of the core in the portion where the uneven shape exists is 0 to 10%. When the side surface of the optical fiber is subjected to sandblasting treatment, scratched using a file or a cutter, or unevenness is formed by removing a part of the cladding, the core existing inside the cladding layer on the surface of the plastic optical fiber may be exposed. When the exposure is 10% or less, preferably 5% or less, more preferably 2% or less, the cladding that serves to protect the core from external environments such as heat and moisture remains appropriately, and even when the core is exposed to heat and moisture during use, the decrease in the lateral luminance can be suppressed, that is, the heat resistance is excellent.

[0037] The measurement of the exposure ratio of the core can be calculated, for example, by observing the surface of the plastic optical fiber after forming the unevenness with a microscope and calculating from the ratio of the area where the core portion is exposed within the visual field.

[0038] The breaking strength of the plastic optical fiber by the tensile test is 6.6 N or more and 9.0 N or less. When the breaking strength is 6.6 N or more, it becomes possible to create a fabric using the plastic optical fiber of the present invention in an automatic loom. Also, when the breaking strength of the plastic optical fiber of the present invention is 9.0 N or less, the optical fiber has flexibility, and problems such as the fabric curling are less likely to occur.

[0039] In order to make the breaking strength 6.6 N or more, it is effective to adjust the materials of the raw materials used for the core and the cladding, and the stretching process during spinning. The draw ratio is preferably 1.75 times or more and 3.0 times or less, and more preferably 1.9 times or more and 2.5 times or less.

[0040] When light is input from the end of the plastic optical fiber, it is preferable that the light is emitted from the side surface. In a general optical fiber, when light is input from one end, the input light repeatedly undergoes total reflection inside the core, and most of it is emitted from the other end. Even if a fabric is made using this general optical fiber and light is input from one end of the optical fiber, the fabric hardly becomes bright. By using the plastic optical fiber of the present invention for a fabric or a knitted fabric, when light is input from the end thereof, light is emitted from the side surface of the plastic optical fiber, and the fabric or the knitted fabric glows, so that a fabric or a knitted fabric excellent in design can be provided.

[0041] The side surface of the plastic optical fiber of the present invention emits light, and since the outer diameter is as thin as 50.0 μm or more and 300.0 μm or less, it can be freely bent. Therefore, it is preferably used for a fabric or a knitted fabric. When the plastic optical fiber of the present invention is applied to a fabric or a knitted fabric and light is input from the end of the plastic optical fiber, the fabric or the knitted fabric emits light, and a fabric or a knitted fabric excellent in design can be provided. That is, the fabric of the present invention is made using the plastic optical fiber of the present invention. Also, the knitted fabric of the present invention is also made using the plastic optical fiber of the present invention. Further, since the plastic optical fiber of the present invention has excellent heat resistance, its characteristics hardly change even in an environment exposed to direct sunlight or moisture, and it is suitable for applications that require heat resistance, such as the interior of an automobile.

[0042] Next, an example of a method for manufacturing an illuminated plastic optical fiber according to an embodiment of the present invention will be described.

[0043] The plastic optical fiber of the present invention can be manufactured by a composite spinning method using a core-sheath type composite spinning die. Further, in this composite spinning method, the cross-sectional shapes of the core and the cladding can be made exactly the same in any cross-section in the longitudinal direction.

[0044] Next, a general stretching process is performed to improve the mechanical properties, resulting in a plastic optical fiber. As mentioned above, the stretching ratio is preferably 1.75 times or more and 3.0 times or less, and more preferably 1.9 times or more and 2.5 times or less.

[0045] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples.

[0046] [Measurement and Evaluation Method] (1) Cladding composition ratio (mass%) For the cladding used in each example and comparative example, solid １９ The composition ratio (mass %) was determined using F-NMR (AVANCENEO400, Bruker) and FT-IR (FT-IR, Bio-RadDigilab).

[0047] (2) Diameter of optical fiber (μm) The diameter of the plastic optical fiber obtained in each example and comparative example was measured using a micrometer.

[0048] (3) Cladding thickness of optical fiber (μm) The thickness of the cladding was measured by cross-sectional observation of the plastic optical fiber obtained in each example and comparative example using a digital microscope (Keyence VHX-6000).

[0049] (4) Tensile strength (N) For each example and comparative example, a 10 cm sample was taken from the optical fiber obtained, and the breaking stress was measured at a rate of 10 cm / min using a desktop precision universal tester (Autograph AGS-10kNX, manufactured by Shimadzu Corporation), and this was defined as the tensile strength.

[0050] (5) Weaving properties The plastic optical fibers obtained in each example and comparative example were used as weft threads in an automatic loom and tested for weaving properties. If thread breakage occurred during weaving, it was judged as NG, and if weaving was possible without thread breakage, it was judged as Good.

[0051] (6) Fabric Appearance The appearance of the fabrics made from the plastic optical fibers obtained in each example and comparative example was checked in the weaving properties section. Fabrics that were flat and free of distortion were judged as Good, while fabrics that were distorted or curled significantly were judged as NG.

[0052] (Evaluation after blasting) The following evaluations were performed after using the plastic optical fibers obtained in each example and comparative example as weft yarn, creating fabrics using plastic optical fibers on an automatic loom, and then performing blasting on the surface of the fabrics. The blasting was performed using alumina particles (WA220, manufactured by Fuji Seisakusho) with an average particle size of 60 μm at a pressure of 0.2 MPa for 1 to 3 seconds. The blasting times for each example and comparative example are shown in Tables 1 and 2.

[0053] (7) Core exposure rate (%) The plastic optical fibers obtained in each example and comparative example were woven into fabric using the method described above, and their surfaces were subjected to blast treatment. The blast-treated areas of the obtained samples were observed on the surface of the optical fibers at 500x magnification using a digital microscope (Keyence VHX-6000). The core exposure rate was defined as the ratio of the area of ​​the core exposed portion to the total area within the field of view of the observation screen, and the core exposure rate of the samples in each example and comparative example was calculated.

[0054] (8) Maximum surface roughness Rz (μm) The plastic optical fibers obtained in each example and comparative example were woven into fabric using the method described above, and their surfaces were subjected to blast treatment. The blast-treated areas of the obtained samples were observed at 500x magnification using a digital microscope (Keyence VHX-6000), and the maximum surface roughness Rz (μm) was measured using the software installed on the microscope.

[0055] (9) Side luminance (CD / cm²) ２The plastic optical fibers obtained in each example and comparative example were woven into fabric using the method described above, and their surfaces were subjected to blast treatment. For the blast-treated areas of the obtained samples, a white LED light source (Kenko Tokina KTL-100) with a power supply of DC 24V and a power consumption of 20W was used as a light source, with the brightness adjustment scale set to 5. A colorimeter (Konica Minolta CS-100) was used to measure the lateral brightness at a position 30 cm from the light source along the length of the optical fiber connected to the light source.

[0056] After the above measurements, each sample was heat-treated in a hot air oven (manufactured by ESPEC) at 95°C for 24 hours, and then the same side brightness measurements as above were performed to obtain the side brightness after heat treatment.

[0057] [Example 1] Ethylene (Et) / tetrafluoroethylene (4F) / hexafluoropropylene (6F) / monomer A (CH) as the polymer forming the cladding, with the composition shown in Table 1. ２ = CF (CF ２ ) ３ A copolymer consisting of H) with a melting point of 162°C was supplied to a composite spinning machine. Furthermore, PMMA with a Tg of 122°C, produced by continuous soul polymerization, was supplied to the composite spinning machine as the polymer forming the core, and core-sheath composite melt spinning was performed at 235°C. After spinning, the fibers were stretched to twice their original size at an oven temperature of 150°C to obtain a plastic optical fiber with an outer diameter of 260 μm, a core diameter of 240 μm, and a cladding thickness of 10.0 μm.

[0058] [Examples 2-5] Plastic optical fibers were prepared in the same manner as in Example 1, except that the core diameter, cladding thickness, outer diameter, or blasting time were changed as shown in Table 1.

[0059] [Example 6] A plastic optical fiber was prepared in the same manner as in Example 1, except that a layer of cladding 2, made of vinylidene fluoride (2F) with a melting point of 168°C, was further formed on the inside of cladding 1, resulting in a three-layer structure with an outer diameter of 260 μm, a core diameter of 236 μm, a cladding 2 thickness of 2.0 μm, and a cladding 1 thickness of 10.0 μm. The spinning temperature and drawing conditions were the same as in Example 1.

[0060] [Comparative Examples 1-4] Plastic optical fibers were prepared in the same manner as in Example 1, except that the cladding composition, thickness, or blasting time was changed as shown in Table 2.

[0061]

[0062]

[0063] The plastic optical fiber of the present invention emits light from its sides and has a small outer diameter, making it suitable for use in woven and knitted fabrics. When light is shone from the end of the plastic optical fiber, the woven or knitted fabric emits light, providing a woven or knitted fabric with excellent design. Furthermore, the plastic optical fiber of the present invention has excellent heat resistance, so its properties do not easily change even in environments exposed to direct sunlight and moisture, making it suitable for use in applications requiring heat resistance, such as automotive interiors.

Claims

1. A plastic optical fiber having a core and at least one cladding layer, wherein the resin used for the core is polymethyl methacrylate, the glass transition temperature Tg of the polymethyl methacrylate is 115°C to 130°C, the melting point of the resin used for the outermost cladding layer of the at least one cladding layer is 150°C to 200°C, the outer diameter of the plastic optical fiber is 50 μm to 300 μm, the thickness of the outermost cladding layer is 7.5 μm to 20.0 μm, at least a portion of the surface of the plastic optical fiber has an uneven shape, the exposure of the core in the portion with the uneven shape is 0% to 10%, and the breaking strength of the plastic optical fiber by tensile test is 6.6 N to 9.0 N.

2. The plastic optical fiber according to claim 1, wherein the plastic optical fiber emits light from its side.

3. The plastic optical fiber according to claim 1 or 2, wherein the outermost cladding contains 10 to 35% by mass of ethylene, 45 to 69% by mass of tetrafluoroethylene, 20 to 45% by mass of hexafluoropropylene, and 0.01 to 10% by mass of a fluorovinyl compound represented by formula (1) as copolymer components. ２ = CX １ (CF ２ )nX ２ Formula (1) In formula (1), X １ X is a fluorine atom or a hydrogen atom. ２ represents a fluorine atom, a hydrogen atom, or a hydrocarbon group, and n represents an integer from 1 to 10.

4. The plastic optical fiber according to claim 1 or 2, wherein the inner layer of the outermost cladding is another cladding layer.

5. The plastic optical fiber according to claim 1 or 2, wherein the maximum surface roughness Rz of the portion where the uneven shape exists is 3.0 μm or more and 7.0 μm or less.

6. The plastic optical fiber according to claim 1 or 2, wherein the uneven surface shape of the plastic optical fiber is obtained by removing a portion of the outermost cladding.

7. The plastic optical fiber according to claim 1 or 2, wherein the uneven surface shape of the plastic optical fiber is formed by blast treatment.

8. A fabric made using the plastic optical fiber described in claim 1 or 2.

9. A knitted fabric made using the plastic optical fiber described in claim 1 or 2.

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