Illumination waveguide and method for manufacturing the same

Abstract

To provide an illumination waveguide that exhibits high lateral emission along its length without using fluorine-based materials. [Solution] An illumination waveguide comprising a core and a cladding surrounding the core, containing a non-fluorinated polymer and having a smooth inner surface, wherein the core and cladding are directly adjacent, the surface roughness Ra of the inner surface of the cladding is less than 300 nm, the refractive index n1 of the core is 1.44 or greater, the refractive index n2 of the cladding is 1.39 or greater, the Δn defined by the refractive index difference n1-n2 between the core and cladding is 0.05-0.20, and the luminance at a position 100 mm from the end when straight light is incident from the end of the illumination waveguide is L1 (cd / m²). 2 ), the brightness at a position 400 mm from the edge is L2 (cd / m²). 2 An illumination waveguide in which L2 / L1 is 0.1 or greater when )

Description

[Technical Field]

[0001] This disclosure relates to an illumination waveguide and a method for manufacturing the same.

[0002] An illumination waveguide comprises a core formed of a high refractive index material and a cladding formed of a low refractive index material surrounding the core. Light incident from one end of the illumination waveguide propagates through the core along the length of the waveguide, reaching the other end to function as a point light source, or is radiated outwards from the side in a predetermined area of ​​the illumination waveguide, exhibiting side emission. Illumination waveguides can be used as lighting fixtures or auxiliary lighting fixtures for vehicles, buildings, etc., where the light source is positioned at a distance from the location where illumination or display is desired.

[0003] Patent Document 1 (Japanese Patent Publication No. 2001-519050) describes an illumination waveguide comprising a solid core having a minimum cross-sectional dimension of at least 1 mm, and cladding surrounding the core, containing a polymer and having an optically smooth inner surface.

[0004] Patent Document 2 (Japanese Patent Publication No. 2002-202415) describes a side-emitting optical fiber comprising a central core and a cladding arranged around the core, characterized in that the cladding consists of a transparent first layer in contact with the core and a light-diffusing second layer formed on the outside of the first layer, and both layers are integrally molded.

[0005] Patent Document 3 (Japanese Patent Publication No. 2009-276651) describes a side-emitting optical fiber having a core containing a first light scatterer and a cladding containing a second light scatterer arranged substantially concentrically around the core, wherein the optical transmittance of the cladding at an optical wavelength of 550 nm is 70% to 90%. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Special Publication No. 2001-519050 [Patent Document 2] Japanese Patent Publication No. 2002-202415 [Patent Document 3] Japanese Patent Publication No. 2009-276651 [Overview of the project] [Problems that the invention aims to solve]

[0007] Illumination waveguides utilize total internal reflection at the interface, caused by the refractive index difference between the core and cladding materials, to propagate light along the length of the waveguide within the core. The larger the refractive index difference, the more light incident at the core-cladding interface undergoes total internal reflection over a wide range of incident angles, allowing for efficient light propagation over long distances. Fluoropolymers are generally used as cladding materials due to their excellent low refractive index. However, depending on the application, it may be desirable to avoid the use of fluorine-based materials such as fluoropolymers.

[0008] This disclosure provides an illumination waveguide that can exhibit high lateral emission along its length without using fluorine-based materials. [Means for solving the problem]

[0009] According to one embodiment of this disclosure, An illumination waveguide comprising a core and a cladding surrounding the core, comprising a non-fluorinated polymer and having a smooth inner surface, The core and the cladding are directly adjacent to each other. The surface roughness Ra of the inner surface of the cladding is less than 300 nm. The refractive index n1 of the core is 1.44 or greater. The refractive index n2 of the cladding is 1.39 or higher. The Δn defined by the refractive index difference n1-n2 between the core and the cladding is 0.05-0.20. When a straight beam of light is incident from the end of the aforementioned illumination waveguide, the luminance at a position 100 mm from the end is L1 (cd / m²). 2) The luminance at a position 400 mm from the end is L2 (cd / m 2 ) and when L2 / L1 is 0.1 or more, an illumination light guide tube is provided.

[0010] According to another embodiment of the present disclosure, An illumination light guide tube including a core and a clad that surrounds the core and has a smooth inner surface and contains a non-fluorine-based polymer, The core and the clad are directly adjacent to each other, The surface roughness Ra of the inner surface of the clad is less than 300 nm, The core contains an acrylic resin, The clad contains a polyolefin or a silicone resin, Δn defined by the refractive index difference n1−n2 between the core and the clad is 0.05 to 0.20, When the luminance at a position 100 mm from the end when linearly polarized light is incident from the end of the illumination light guide tube is L1 (cd / m 2 ) and the luminance at a position 400 mm from the end is L2 (cd / m 2 ) and when L2 / L1 is 0.1 or more, an illumination light guide tube is provided.

[0011] According to still another embodiment of the present disclosure, Extruding a polymer composition to form a clad having an internal space, Filling the internal space of the clad with a polymerizable composition, and Curing the polymerizable composition to form a core, A method for manufacturing the above illumination light guide tube including the above is provided.

Advantages of the Invention

[0012] According to the present disclosure, an illumination light guide tube that can exhibit high side surface light emission along the length direction without using a fluorine-based material is provided.

[0013] The above description should not be regarded as disclosing all embodiments of the present invention and all advantages related to the present invention.

Brief Description of the Drawings

[0014] [Figure 1] It is a perspective view of an illumination light guide tube of one embodiment.

Modes for Carrying Out the Invention

[0015] Hereinafter, for the purpose of exemplifying representative embodiments of the present invention, a more detailed description will be given with reference to the drawings as necessary, but the present invention is not limited to these embodiments.

[0016] In the present disclosure, “(meth)acrylic” refers to acrylic or methacrylic, and (meth)acrylate refers to acrylate or methacrylate.

[0017] The illumination light guide tube of the first embodiment includes a core and a clad that surrounds the core, contains a non-fluorine-based polymer, and has a smooth inner surface. The core and the clad are directly adjacent to each other, the surface roughness Ra of the inner surface of the clad is less than 300 nm, the refractive index n1 of the core is 1.44 or more, the refractive index n2 of the clad is 1.39 or more, and Δn defined by the refractive index difference n1 - n2 between the core and the clad is 0.05 to 0.20. When direct light is incident from the end of the illumination light guide tube, the luminance at a position 100 mm from the end is L1 (cd / m 2 ), and the luminance at a position 400 mm from the end is L2 (cd / m 2 ), and L2 / L1 is 0.1 or more.

[0018] The illumination light guide tube of the second embodiment includes a core and a clad that surrounds the core, contains a non-fluorine-based polymer, and has a smooth inner surface. The core and the clad are directly adjacent to each other, the surface roughness Ra of the inner surface of the clad is less than 300 nm, the core contains an acrylic resin, the clad contains a polyolefin or a silicone resin, and Δn defined by the refractive index difference n1 - n2 between the core and the clad is 0.05 to 0.20. When direct light is incident from the end of the illumination light guide tube, the luminance at a position 100 mm from the end is L1 (cd / m 2), the brightness at a position 400 mm from the edge is L2 (cd / m²). 2 When this is the case, L2 / L1 is 0.1 or greater.

[0019] By setting the surface roughness Ra of the inner surface of the cladding directly adjacent to the core to less than 300 nm, and the Δn defined by the refractive index difference n1-n2 between the core and the cladding to 0.05-0.20, it is possible to obtain an illumination waveguide that emits high-brightness light from the sides over long distances along the length, even when using cladding containing a non-fluorinated polymer.

[0020] Figure 1 shows a perspective view of an illumination waveguide according to one embodiment. The illumination waveguide 10 includes a core 12 and a cladding 14 surrounding the core 12. By illuminating the illumination waveguide 10 with light from at least one end using a light source (not shown), such as an LED or laser, light can be emitted from the side of the illumination waveguide 10.

[0021] The length of the illumination waveguide can be appropriately determined according to the application, for example, from 50 cm to 10 m. The outer diameter of the illumination waveguide can be appropriately determined according to the application, for example, from 1 mm to 50 mm.

[0022] In one embodiment, the core includes a polymer. Examples of polymers include acrylic resins, polycarbonate (PC), ethylene-vinyl acetate copolymer (EVA), vinyl acetate-vinyl chloride copolymer, and styrene-ethylene-butadiene-styrene block polymer (SEBS).

[0023] The core preferably contains an acrylic resin. Examples of acrylic resins include a monomer homopolymer or copolymer containing at least one selected from the group consisting of (meth)acrylate and (meth)acrylic acid.

[0024] Examples of (meth)acrylates include aliphatic or alicyclic (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate. Aliphatic or alicyclic (meth)acrylates can be used alone or in combination of two or more types.

[0025] The monomer preferably contains an aromatic ring-containing (meth)acrylate. The aromatic ring-containing (meth)acrylate can effectively increase the refractive index of the core. Examples of aromatic ring-containing (meth)acrylates include phenyl(meth)acrylate, benzyl(meth)acrylate, phenylethyl(meth)acrylate, ethoxylated-o-phenylphenol(meth)acrylate, and 4-phenylbenzyl(meth)acrylate. The aromatic ring-containing (meth)acrylate can be used alone or in combination of two or more types. The content of aromatic ring-containing (meth)acrylate in the monomer is preferably 35 to 95% by mass, more preferably 40 to 90% by mass, and even more preferably 45 to 85% by mass.

[0026] The monomer preferably contains a hydroxyl-containing (meth)acrylate. The hydroxyl-containing (meth)acrylate can improve the appearance stability of the illumination waveguide under high humidity conditions. Although not bound by any theory, if the cladding has high humidity permeability, moisture can easily penetrate into the illumination waveguide under high humidity conditions. A core formed using a hydroxyl-containing (meth)acrylate can reduce the clouding that may occur due to the penetration of moisture. Examples of hydroxyl-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, diethylene glycol mono(meth)acrylate, and triethylene glycol mono(meth)acrylate. The hydroxyl-containing (meth)acrylate can be used alone or in combination of two or more types. The content of (meth)acrylate having a hydroxyl group in the monomer is preferably 5 to 30% by mass, more preferably 7 to 25% by mass, and even more preferably 10 to 20% by mass.

[0027] From the viewpoint of the mechanical strength of the core, it is preferable that the acrylic resin is crosslinked. Examples of crosslinking agents include polyfunctional monomers such as hexanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, trimethylolpropane di(meth)acrylate, diallyl phthalate, diethylene glycol bisallyl carbonate, ethoxylated bisphenol A di(meth)acrylate, diprenyl glycerin ether, and isoprenyl(meth)acrylate. The crosslinking agent can be used alone or in combination of two or more. The content of the crosslinking agent is preferably 0.01 to 5 parts by mass, more preferably 0.1 to 4.5 parts by mass, and even more preferably 0.5 to 2.0 parts by mass, based on 100 parts by mass of monomer.

[0028] The refractive index n1 of the core is preferably 1.44 or higher. Preferably, the refractive index n1 of the core is 1.44 to 1.66, more preferably 1.49 to 1.62, and even more preferably 1.53 to 1.58.

[0029] The light transmittance of the core is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more. In this disclosure, the light transmittance is a value measured with respect to light at a wavelength of 550 nm using a spectrophotometer.

[0030] The radial cross-section of the core is usually circular or elliptical. The radial cross-section of the core may have other shapes, such as rectangular, as long as they do not impair the effects of the present invention. The diameter of the core is not particularly limited, but can be, for example, 1 mm to 30 mm. For cores with a radial cross-section other than circular, the diameter is defined as the shortest distance between two points where a line passing through the center of the radial cross-section of the core intersects the outer edge.

[0031] The cladding contains a non-fluorinated polymer. The non-fluorinated polymer is preferably a heat-shrinkable material or an elastomer. Examples of non-fluorinated polymer materials include polyolefins such as polyethylene and polypropylene; polyamides; polyurethanes; and silicone resins.

[0032] From the viewpoint of processability, availability, and durability, the cladding preferably contains polyolefin or silicone resin, more preferably polyolefin, and even more preferably polypropylene.

[0033] The refractive index n2 of the cladding is preferably 1.39 or higher. The refractive index n1 of the cladding is preferably 1.39 to 1.63, more preferably 1.42 to 1.59, and even more preferably 1.45 to 1.55.

[0034] The light transmittance of the cladding is preferably 60% or more, more preferably 70% or more, and even more preferably 90% or more.

[0035] The cladding thickness is typically 50 μm to 2 mm, preferably 70 μm to 1.5 mm, and more preferably 100 μm to 1 mm. The cladding may be a single layer or a multilayer.

[0036] The core and cladding are directly adjacent. In this disclosure, “directly adjacent” includes not only embodiments in which no other layers or materials are interposed between the core and cladding, but also embodiments in which there are primer layers provided on the surface of the core or cladding, material alterations on the surface of the core or cladding, etc., between the core and cladding, but these do not substantially affect the optical performance of the illumination waveguide. The cladding may completely surround the core, or the core may be exposed to the outside at selected locations for the purpose of optical coupling with other illumination waveguides or localized light extraction.

[0037] The refractive index difference Δn, defined by the refractive index difference n1-n2 between the core and cladding, is 0.05 to 0.20, preferably 0.05 to 0.15, and more preferably 0.05 to 0.12. By setting Δn to 0.05 or higher, high-brightness illumination can be achieved from the sides over long distances along the length of the illumination waveguide. By setting Δn to 0.20 or lower, the amount of high refractive index components such as (meth)acrylate having aromatic rings can be reduced, thereby suppressing yellowing of the illumination waveguide during manufacturing or use.

[0038] The surface roughness Ra of the inner surface of the cladding is less than 300 nm, preferably less than 200 nm, and more preferably less than 150 nm. Since the core and cladding are directly adjacent, the surface roughness Ra of the outer surface of the core is substantially equivalent to the surface roughness Ra of the inner surface of the cladding. By setting the surface roughness Ra of the inner surface of the cladding to less than 300 nm, light can be propagated inside the core over long distances along the length of the illumination waveguide, even if the refractive index difference Δn between the core and cladding is a relatively small value of 0.20 or less. The surface roughness Ra of the inner surface of the cladding is a value measured by the method described in the examples.

[0039] When linearly polarized light is incident from the end of the lighting light guide tube, the luminance at a position 100 mm from the end is L1 (cd / m 2 2), when the luminance at a position 400 mm from the end is L2 (cd / m2), L2 / L1 is 0.1 or more, preferably 0.2 or more, and more preferably 0.3 or more. By L2 / L1 being 0.1 or more, it is possible to emit light from the side surface with high luminance over a long distance along the length direction of the lighting light guide tube. L2 / L1 is preferably 0.5 or less, more preferably 0.7 or less, and still more preferably 1 or less. In the present disclosure, L2 / L1 is also referred to as the luminance retention rate, and L2 / L1 is a value measured by the method described in the examples.

[0040] The cladding, the core, or both may contain a light scatterer. Examples of the light scatterer include inorganic particles such as titanium oxide particles, zinc oxide particles, alumina particles, and silicon oxide particles; and organic particles such as polystyrene resin particles and silicone resin particles. The light scatterer can be used alone or in combination of two or more.

[0041] The average particle size of the light scatterer is preferably 0.1 to 30 μm, more preferably 1 to 15 μm. By setting the average particle size to 30 μm or less, the light scatterer can be more uniformly dispersed in the cladding or the core. By setting the average particle size to 0.1 μm or more, the wavelength dependence in the scattering of visible light can be suppressed.

[0042] By including a light scatterer in the cladding, the generation of bright spots in side emission can be suppressed, and light can be emitted more uniformly from the side surface. The content of the light scatterer in the cladding can be, for example, 0.0005 to 0.1% by mass, 0.0008 to 0.08% by mass, or 0.001 to 0.005% by mass.

[0043] When a light scatterer is included in the core, the lateral emission brightness near the light source tends to increase, while the lateral emission brightness at locations far from the light source tends to decrease. Therefore, the content of the light scatterer in the core is preferably less than 0.0005% by mass, more preferably less than 0.0002% by mass, and even more preferably less than 0.0001% by mass. It is most preferable that the core does not contain any light scatterer, i.e., the content of the light scatterer in the core is 0% by mass.

[0044] The cladding, core, or both may contain antioxidants. Cores containing aromatic rings may yellow during the manufacture or use of illumination waveguides, so it is preferable that they contain antioxidants. The antioxidants are not particularly limited, but include phenolic antioxidants such as octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane; 2,2'-methylenebis(4,6-di-tert-butylphenyl)2-ethylhexyl phosphite, tetra-C 12-15 Examples of antioxidants include phosphite-based antioxidants such as alkyl(propane-2,2-diylbis(4,1-phenylene))bis(phosphine) and triisodecyl phosphine; and sulfur-based antioxidants such as di(tridecyl)3,3'-thiodipropionate. The antioxidant content of the core is preferably 0.005 to 0.8% by mass, more preferably 0.01 to 0.6% by mass, and even more preferably 0.05 to 0.4% by mass.

[0045] The cladding, core, or both may contain other additives such as plasticizers, surfactants, pigments, dyes, and UV stabilizers, provided that they do not impair the effects of the present invention.

[0046] One embodiment of the method for manufacturing an illumination waveguide is: Extruding a polymer composition to form a cladding having an internal space, Filling the internal space of the cladding with a polymerizable composition, and The polymerizable composition is cured to form a core. Includes.

[0047] The polymer composition includes the non-fluorinated polymer described above for the cladding. In addition to the non-fluorinated polymer, the polymer composition may also include the light scatterers, antioxidants, other additives, or a combination thereof.

[0048] A cladding with an internal space is formed by extruding a polymer composition. The extrusion conditions are not particularly limited as long as the surface roughness Ra of the inner surface of the cladding is within the above range, but for example, the temperature can be 190 to 240°C and the pressure can be 0.5 to 9.0 MPa.

[0049] The polymerizable composition is filled into the internal space of the resulting cladding. The polymerizable composition comprises the monomers and polymerization initiators described above for the core, and optionally further comprises a crosslinking agent. A photopolymerization initiator or a thermal polymerization initiator can be used as the polymerization initiator.

[0050] Examples of photopolymerization initiators include benzoethyl ether, diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)-benzyl]-phenyl}-2-methylpropan-1-one, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinop Examples include ropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-ylphenyl)-butan-1-one, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and ethyl(2,4,6-trimethylbenzoyl)phenylphosphenate. The photopolymerization initiators can be used alone or in combination of two or more.

[0051] Examples of thermal polymerization initiators include organic peroxides such as benzoyl peroxide, dilauroyl peroxide, t-butylperoxy-2-ethylhexanoate, and bis(4-t-butylcyclohexyl)peroxydicarbonate; and azo-based thermal polymerization initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), dimethyl-2,2-azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-methylpropionic acid)dimethyl, and azobis(2,4-dimethylvaleronitrile) (AVN). Thermal polymerization initiators can be used alone or in combination of two or more.

[0052] The total amount of polymerization initiator used is generally about 0.01 parts by mass or more, or about 0.05 parts by mass or more, and about 5 parts by mass or less, or about 3 parts by mass or less, per 100 parts by mass of the total amount of monomer and crosslinking agent.

[0053] The polymerizable composition is typically filled into the internal space of the cladding under pressure. For example, by sealing one end of the cladding and filling the other end with the polymerizable composition under pressure, the polymerizable composition can be filled more uniformly into the internal space of the cladding while suppressing the inclusion of air bubbles. It is preferable to use nitrogen gas for pressurization.

[0054] The polymerizable composition is cured to form a core. This allows for the manufacture of an illumination waveguide. The polymerizable composition can be cured by photopolymerization or thermal polymerization, with photopolymerization being preferable. Since photopolymerization can be carried out at relatively low temperatures, it is possible to suppress the increase in surface roughness Ra of the inner surface of the cladding during the curing of the polymerizable composition, i.e., the roughening of the inner surface of the cladding.

[0055] The conditions for photopolymerization and thermal polymerization are not particularly limited. Photopolymerization can be performed using a light source such as an ultraviolet lamp or LED, with a wavelength of 300-400 nm and an irradiation intensity of 0.1-20 mW / cm². 2 This can be carried out by irradiating the polymerizable composition with light for 5 seconds to 30 minutes. Thermal polymerization can be carried out, for example, by submerging a cladding filled with the polymerizable composition in a heated bath, such as a water bath at 35 to 90°C, and leaving it in the heated bath for 2 minutes to 1 hour.

[0056] Since polymerizable compositions may shrink upon curing, it is preferable to cure them under pressure. This helps to prevent the formation of gaps between the cladding and the core.

[0057] Another embodiment of a method for manufacturing an illumination waveguide includes, for example, co-extrusion molding, which involves simultaneously extruding the core material into the internal space of the cladding during the cladding extrusion process.

[0058] The illumination waveguides of this disclosure can be used in decorative lighting devices for vehicles or buildings, and in information display devices such as advertising signs, variable displays, and road signs. [Examples]

[0059] The following examples illustrate specific embodiments of the present disclosure, but the present invention is not limited thereto. All parts and percentages are by mass unless otherwise specified. Numerical values ​​include errors inherent to the measurement principle and measuring device. Numerical values ​​are shown with significant figures after normal rounding.

[0060] Table 1 shows the materials, reagents, etc., used in the examples and comparative examples.

[0061] [Table 1]

[0062] (1) Manufacturing of illumination waveguides The illumination waveguides for Examples 1-2 and Comparative Examples 1-6 were manufactured according to the following procedure.

[0063] (A) Formation of cladding A masterbatch was obtained by mixing 100 parts by mass of polypropylene (PP) PC630A with 1 part by mass of TiO2 powder and mixing at a temperature exceeding the melting point of polypropylene. The masterbatch and PP pellets PC630A were mixed in a ratio of 1:29 (mass / mass) to prepare the clad material. A hollow tubular PP clad with a thickness of 250 μm and an outer diameter of 3.5 mm was manufactured by extruding the clad material at a temperature of 200 °C and a pressure of 5.0 MPa.

[0064] A cladding material was prepared by mixing 100 parts by mass of fluorinated ethylene propylene (FEP) resin with 0.1 parts by mass of ZnO powder and mixing at a temperature exceeding the melting point of FEP. A hollow tubular FEP cladding material with a thickness of 250 μm and an outer diameter of 3.5 mm was produced by extrusion molding of the cladding material at a temperature of 350 °C and a pressure of 5.0 MPa.

[0065] (B) Core formation Acrylic monomer, crosslinking agent, polymerization initiator, and photodispersant were mixed according to the composition shown in Table 2. Bubbles were removed by allowing the mixture to stand under a pressure of 10.0 kPa or less to obtain a polymerizable composition. The polymerizable composition was injected into the interior of the cladding from one end at room temperature. The polymerizable composition was filled into the interior of the cladding by sealing one end of the cladding and applying a pressure of 0.2 MPa with nitrogen gas to the polymerizable composition from the other end. The polymerizable composition was cured by the following thermosetting or UV curing methods.

[0066] (B-1) Heat curing The polymerizable composition was thermocured by applying a pressure of 0.2 MPa to the polymerizable composition and immersing the cladding filled with the polymerizable composition in 90°C water for 15 minutes. This process was carried out sequentially from the sealed end of the cladding to produce the illumination waveguide.

[0067] (B-2) UV curing While applying a pressure of 0.2 MPa to the polymerizable composition, the cladding filled with the polymerizable composition was irradiated using an LED at a wavelength of 365 nm and an irradiation intensity of 5 mW / cm². 2 The light was applied for 5 minutes. This process was carried out sequentially from the end of the cladding to produce the illumination waveguide.

[0068] (2) Refractive index difference Δn The refractive index n1 of the core was determined by preparing a test specimen with a width of 10 mm, a length of 30 mm, and a thickness of 1 mm using a polymerizable composition, and measuring the sample using an Abbe refractometer (NAR-1T, manufactured by Atago Co., Ltd.). The refractive index n2 of the cladding was determined by preparing a test specimen with a width of 10 mm, a length of 30 mm, and a thickness of 1 mm using the cladding material, and measuring the sample using an Abbe refractometer (NAR-1T, manufactured by Atago Co., Ltd.). The refractive index difference Δn is defined by the following formula. Δn = n1 - n2

[0069] (3) Surface roughness Ra The surface roughness Ra of the inner surface of the cladding was measured using a laser microscope (OLS40-SU, manufactured by Olympus Corporation) after cutting a hollow tubular cladding to prepare a square sample of approximately 6.0 mm on each side.

[0070] (4) Brightness retention A 1.0 m length of illumination waveguide was cut. Light from a light source (LS-LHA, manufactured by Sumida Optical Glass Co., Ltd.) was converted into a straight beam using an optical fiber cable (length 1.0 m or more, outer diameter within ±20% of the diameter of the light guide tube), and the straight beam was incident on one end of the illumination waveguide. Using a colorimeter (CS-150, manufactured by Konica Minolta, Inc.), the luminance L1 (cd / m²) at a position 100 mm from the light incident end was measured. 2 ), and the luminance L2 (cd / m²) at a position 400 mm from the light incident end. 2 The luminance retention rate was measured. The luminance retention rate is defined by the following formula. Brightness retention rate=L1 / L2

[0071] The composition of the polymerizable composition is shown in Table 2.

[0072] [Table 2]

[0073] Table 3 shows the configuration of the illumination waveguide and the manufacturing conditions for the core.

[0074] [Table 3]

[0075] The evaluation results for the illumination waveguide are shown in Table 4.

[0076] [Table 4]

[0077] It will be obvious to those skilled in the art that various improvements and modifications of the present invention are possible without departing from the scope and spirit of the invention. Some embodiments of this disclosure are described below. [Aspect 1] An illumination waveguide comprising a core and a cladding surrounding the core, comprising a non-fluorinated polymer and having a smooth inner surface, The core and the cladding are directly adjacent to each other. The surface roughness Ra of the inner surface of the cladding is less than 300 nm. The refractive index n1 of the core is 1.44 or greater. The refractive index n2 of the cladding is 1.39 or higher. The Δn defined by the refractive index difference n1-n2 between the core and the cladding is 0.05-0.20. When a straight beam of light is incident from the end of the aforementioned illumination waveguide, the luminance at a position 100 mm from the end is L1 (cd / m²). 2 ), and the luminance at a position 400 mm from the end is L2 (cd / m²). 2 An illumination waveguide in which L2 / L1 is 0.1 or greater when ) [Aspect 2] The illumination waveguide according to embodiment 1, wherein the core contains an acrylic resin and the cladding contains a polyolefin or silicone resin. [Aspect 3] An illumination waveguide comprising a core and a cladding surrounding the core, having a smooth inner surface and containing a non-fluorinated polymer, The core and the cladding are directly adjacent to each other. The surface roughness Ra of the inner surface of the cladding is less than 300 nm. The core contains an acrylic resin, The cladding comprises polyolefin or silicone resin, The Δn defined by the refractive index difference n1-n2 between the core and the cladding is 0.05-0.20. When a straight beam of light is incident from the end of the aforementioned illumination waveguide, the luminance at a position 100 mm from the end is L1 (cd / m²). 2 ), and the luminance at a position 400 mm from the end is L2 (cd / m²). 2 An illumination waveguide in which L2 / L1 is 0.1 or greater when ) [Aspect 4] An illumination waveguide according to any one of embodiments 1 to 3, wherein the cladding comprises a polyolefin. [Aspect 5] An illumination waveguide according to any one of embodiments 1 to 4, wherein Δn is 0.05 to 0.12. [Aspect 6] An illumination waveguide according to any one of embodiments 1 to 5, wherein the content of the light scatterer in the core is less than 0.0005 mass%. [Aspect 7] Extruding a polymer composition to form a cladding having an internal space, Filling the internal space of the cladding with a polymerizable composition, and The polymerizable composition is cured to form a core. A method for manufacturing an illumination waveguide according to any one of embodiments 1 to 6, including the above. [Aspect 8] The method according to embodiment 7, wherein the cladding comprises a polyolefin. [Aspect 9] The method according to embodiment 7 or 8, wherein the polymerizable composition is cured by photopolymerization or thermal polymerization. [Explanation of Symbols]

[0078] 10 Illumination waveguide 12 cores 14 Clad

Claims

1. An illumination waveguide comprising a core and a cladding surrounding the core, comprising a non-fluorinated polymer and having a smooth inner surface, The core and the cladding are directly adjacent to each other. The surface roughness Ra of the inner surface of the cladding is less than 300 nm. The refractive index n of the core １ The value is 1.44 or higher, The refractive index n of the cladding ２ The value is 1.39 or higher, The refractive index difference n between the core and the cladding １ -n ２ The Δn defined by is between 0.05 and 0.20, Let the luminance at a position 100 mm from the end of the lighting light guide tube when linearly polarized light is incident from the end of the lighting light guide tube be L １ (cd / m ２ ), and when the luminance at a position 400 mm from the end is L ２ (cd / m ２ ), L ２ / L １ is 0.1 or more, a lighting light guide tube.

2. The illumination waveguide according to claim 1, wherein the core comprises an acrylic resin and the cladding comprises a polyolefin or silicone resin.

3. An illumination waveguide comprising a core and a cladding surrounding the core, having a smooth inner surface and containing a non-fluorinated polymer, The core and the cladding are directly adjacent to each other. The surface roughness Ra of the inner surface of the cladding is less than 300 nm. The core contains an acrylic resin, The cladding comprises polyolefin or silicone resin, The refractive index difference n between the core and the cladding １ -n ２ The Δn defined by is between 0.05 and 0.20, When a straight beam of light is incident from the end of the aforementioned illumination waveguide, the luminance at a position 100 mm from the end is L. １ (cd / m ２ ), the brightness at a position 400 mm from the end is L ２ (cd / m ２ When L is set to ), ２ / L １ An illumination waveguide in which the value is 0.1 or greater.

4. The illumination waveguide according to any one of claims 1 to 3, wherein the cladding comprises a polyolefin.

5. An illumination waveguide according to any one of claims 1 to 3, wherein Δn is 0.05 to 0.

12.

6. The illumination waveguide according to any one of claims 1 to 3, wherein the content of the light scatterer in the core is less than 0.0005% by mass.

7. Extruding a polymer composition to form a cladding having an internal space, Filling the internal space of the cladding with a polymerizable composition, and The polymerizable composition is cured to form a core. A method for manufacturing an illumination waveguide according to any one of claims 1 to 3, including the method described in any one of claims 1 to 3.

8. The method according to claim 7, wherein the cladding comprises a polyolefin.

9. The method according to claim 7, wherein the polymerizable composition is cured by photopolymerization or thermal polymerization.

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