Light guide rod

Abstract

[Problem] To provide a light guide rod capable of solving the problem of adverse health and / or environmental effects due to fluorine in plastic light guide rods used in linear luminous bodies or the like. [Solution] A light guide rod B is constituted by including: a core layer 1 in the center thereof, said core layer having a transparent resin as a main material; and a clad layer 2 on the outer periphery thereof, said clad layer having a resin with a refractive index lower than that of the core layer 1 as a main material. A non-fluororesin is used as the material of the clad layer 1. Thus, adverse health and / or environmental effects due to fluorine, which have been a cause for concern regarding conventional fluororesin, are eliminated.

Description

light guide rod

[0001] The present invention relates to a plastic light guide rod used as a linear light emitter.

[0002] Plastic light guide rods that can be used for illumination, etc., by making light incident on the end surface from a light source and emitting light from the outer periphery are known (see, for example, Patent Document 1). As such plastic light guide rods, those that use a transparent acrylic resin for the core layer and a fluorine-based resin for the clad layer are commonly known, and the applicant of the present application has also filed a patent application for such a light guide rod.

[0003] However, the organic fluorine compounds such as fluorine-based resins used in the cladding layer are difficult to decompose in the environment and tend to remain in the environment for a long period of time, so restrictions on their production and use are being considered both domestically and internationally. Under these circumstances, there is a demand for the use of fluorine-free resins as an alternative material to the fluorine-based resins used in the cladding layer of plastic light guide rods.

[0004] Regarding non-fluorine-based resins that can be used in place of the fluorine-based resins in the cladding layer, polymethylpentene and the like are known in the field of plastic optical fibers in the optical transmission field, which have a refractive index lower than that of acrylic resins and are also highly transparent (see, for example, Patent Document 2), but there are no known examples of non-fluorine-based resins used in the field of peripheral light-emitting light guide rods.

[0005] JP 2020-166067 A JP 2004-70070 A

[0006] The present invention aims to solve the above-mentioned problems of the prior art, and in summary, to provide a light guide rod that can eliminate the problems of fluorine's adverse effects on health and the environment.

[0007] In order to solve the above problems, the present invention constructs a light guide rod B including a central core layer 1 made primarily of transparent resin, and an outer clad layer 2 made primarily of resin having a lower refractive index than the core layer 1, and uses a non-fluorine-based resin as the material for the clad layer 1 (the effects will be described later).

[0008] In the present invention, an acrylic resin can be used as the transparent resin that is the main material of the core layer 1 .

[0009] In the present invention, polymethylpentene, which has a suitable refractive index and excellent light-emitting and light-guiding properties among non-fluorine-based resins, can be used as the main material of the cladding layer 2 .

[0010] In the present invention, an intermediate layer 3 is provided between the core layer 1 and the clad layer 2, and the main material of the intermediate layer 2 is a block copolymer, so that the intermediate layer 3 can prevent peeling between the core layer 1 and the clad layer 2.

[0011] In the present invention, the block copolymer for the mid layer 3 can be at least one of a styrene elastomer, a hydrogenated styrene thermoplastic elastomer, and a modified polyolefin.

[0012] In the present invention, it is preferable to use, as the block copolymer of the intermediate layer 3, an acrylic thermoplastic elastomer having a smaller tensile stress at 100% elongation as defined by ISO 37 than the main material of the core layer.

[0013] In the present invention, it is preferable to use, as the block copolymer of the mid layer 3, an acrylic thermoplastic elastomer having a lower hardness than the main material of the core layer.

[0014] In the present invention, it is preferable to use hydrogenated styrene-olefin rubber as the block copolymer for the intermediate layer 3 in order to achieve both a high flexural modulus and light-guiding performance.

[0015] In the present invention, an ionomer may also be used for the mid layer 3 .

[0016] In the present invention, it is preferable that a peeling prevention layer 4 is provided on the outer periphery of the clad layer 2, so that peeling between the core layer 1 and the clad layer 2 can be prevented by the peeling prevention layer 4.

[0017] In the present invention, a styrene-based elastomer can be suitably used as the main material of the anti-peeling layer 4 .

[0018] In the present invention, the core layer 1 preferably uses a material in which a hard acrylic resin is mixed with an acrylic elastomer, and the mixing ratio is preferably within the range of 95:5 to 50:50.

[0019] In the present invention, a light guide rod having a core layer primarily made of transparent resin uses a non-fluorine-based resin as the material for the clad layer, thereby eliminating concerns about the adverse effects of fluorine on health and the environment that were a concern with conventional fluorine-based resins.

[0020] It is an overall perspective view showing a light guiding rod of a first embodiment of the present invention. It is an X-X cross-sectional view showing a light guiding rod of a first embodiment of the present invention. It is a cross-sectional view showing a light guiding rod of a second embodiment of the present invention.

[0021] "First embodiment" Next, a first embodiment of the present invention will be described with reference to Figures 1 and 2. In the figures, the symbol B indicates a light guide rod, the symbol 1 indicates a core layer of the light guide rod, the symbol 2 indicates a cladding layer of the light guide rod, and the symbol 3 indicates an intermediate layer of the light guide rod.

[0022] "Configuration and Usage of Light Guide Rod" [1] Basic Configuration of Light Guide Rod The basic configuration of the light guide rod B of this embodiment will be described. In this embodiment, as shown in Figure 1, the light guide rod B is configured by providing an intermediate layer 3 mainly made of a block copolymer between a central core layer 1 mainly made of acrylic resin and an outer clad layer 2 mainly made of a non-fluorine-based resin that has a lower refractive index than the core layer 1. This makes it possible to configure a peripheral surface-emitting light guide rod B that does not suffer from the problem of the adverse environmental effects of fluorine.

[0023] [2] Core Layer [2-1] Transparent Resin Next, each component of the light guide rod B will be described. Regarding the material of the core layer 1, a transparent resin is used in this embodiment. Examples of the transparent resin that can be used include acrylic resin (including acrylic elastomer), styrene resin (including styrene elastomer), polycarbonate, polyurethane, and cyclic olefin resin. Among these, the use of acrylic resin is preferred.

[0024] [2-2] Acrylic Thermoplastic Elastomer: Regarding the material for the core layer 1, an acrylic thermoplastic elastomer with a refractive index of 1.49 can be used as the acrylic resin. Examples of suitable acrylic thermoplastic elastomers include methyl methacrylate and butyl acrylate or block copolymers of methyl acrylate and butyl acrylate with a flexural modulus (ASTM D790) of 50 to 500 MPa, with methyl methacrylate and butyl acrylate being preferred. Specifically, it is preferable to use one with a PMMA content of 10 to 40 wt% and an MFR (JIS K 7210 / ISO 1133) of 2 to 10 g / min under test conditions of 190°C and a 5 kg load.

[0025] The acrylic thermoplastic elastomer used in the core layer 1 preferably has a tensile stress at 100% elongation as defined by ISO 37 greater than that of the intermediate layer, specifically, a tensile stress of 15 MPa or more. The acrylic thermoplastic elastomer used in the core layer 1 preferably has a hardness greater than that of the intermediate layer, specifically, a Shore A of 80 (ISO 7619-1 (Type A)) or more.

[0026] [2-3] Hard acrylic resins can also be used as the material for the core layer 1. Suitable hard acrylic resins include one or more of polymethyl methacrylate, polyethyl methacrylate, polyisobutyl methacrylate, and polyt-butyl methacrylate. In this specification, the term "hard acrylic resin" refers to an acrylic resin whose glass transition temperature (Tg) is equal to or higher than room temperature (25°C).

[0027] The core layer 1 may be made of a material obtained by mixing a hard acrylic resin with an acrylic elastomer. This not only allows the light guide rod B to emit light more uniformly, but also provides it with adequate flexibility, making it easier to wrap around a rope or the like and less likely to become loose. In this case, the mixing ratio of the hard acrylic resin to the acrylic elastomer is preferably 95:5 to 50:50 (more preferably 80:20 to 60:40).

[0028] As the acrylic elastomer to be mixed with the above-mentioned hard acrylic resin, one or more of a block copolymer of methyl methacrylate and butyl acrylate (MMA-BA block copolymer), which is a thermoplastic elastomer, or a block copolymer of methyl acrylate and butyl acrylate can be suitably used.

[0029] [2-4] Shape of Core Layer Regarding the shape of the core layer 1, in this embodiment, a circular cross-sectional shape is adopted as shown in FIG. 1, but the cross-sectional shape of the core layer 1 may also be a semi-elliptical, semicircular, polygonal, or other shape.

[0030] [3] Clad Layer [3-1] Clad Layer Material Polymethylpentene, a non-fluorinated resin with a lower refractive index than acrylic resin and excellent light-emitting and light-guiding properties, can be used as the material for the clad layer 2. Polymethylpentene has a refractive index of 1.46, lower than the refractive index of acrylic resin (1.49), and is a crystalline olefin polymer made primarily from 4-methylpentene-1. It has excellent chemical and oil resistance and is transparent, with a visible light transmittance of 90% or more.

[0031] [3-2] Shape of the Clad Layer The shape of the clad layer 2 may be any shape as long as it is formed with a predetermined thickness around the outer periphery of the core layer 1, and may be a single-layer structure as in this embodiment or a multi-layer structure consisting of multiple clad layers 2. The thickness of the clad layer 2 is preferably limited to the range of 0.1 mm to 1.0 mm in order to obtain weather resistance.

[0032] [4] Intermediate Layer [4-1] Acrylic Thermoplastic Elastomer The same acrylic thermoplastic elastomer as the main material of the core layer can be used as the block copolymer for the intermediate layer 3. Specifically, the MFR (JIS K 7210 / ISO 1133) under test conditions of 190°C and 2.16 kg load is 3 to 80 g / 10 min (preferably 10 to 60 g / 10 min), and the MFR (JIS K 7210 / ISO 1133) under test conditions of 230°C and 2.16 kg load is 50 to 800 g / 10 min (preferably 100 to 700 g / 10 min).

[0033] The acrylic thermoplastic elastomer for the intermediate layer 3 preferably has a lower tensile stress at 100% elongation as defined by ISO 37 than the main material of the core layer, specifically a tensile stress of less than 15 MPa. Furthermore, the acrylic thermoplastic elastomer for the intermediate layer 3 preferably has a lower hardness than the main material of the core layer, specifically a Shore hardness of less than A80 (ISO 7619-1 (Type A)).

[0034] [4-2] Ionomer An ionomer can also be used for the mid layer 3. Specifically, a Zn metal ion type ionomer having an MFR (JIS K 7210 / ISO 1133) of 0.5 to 10 g / 10 min (preferably 0.5 to 3 g / 10 min) under test conditions of a temperature of 190°C and a load of 2.16 kg can be preferably used. Metal ion types other than Zn can also be used as the metal ion.

[0035] [4-3] Styrene-based elastomer A styrene-based elastomer can also be used as the block copolymer for the mid layer 3. Specifically, a styrene-based elastomer having an MFR (ASTM1238) of 10 to 50 g / 10 min (preferably 10 to 30 g / 10 min) under test conditions of a temperature of 190°C and a load of 21.2 N can be suitably used.

[0036] [4-4] Hydrogenated styrene-based thermoplastic elastomer A hydrogenated styrene-based thermoplastic elastomer with excellent adhesiveness can also be used as the block copolymer for the mid layer 3. Specifically, it is preferable to use one with a styrene content of 5 to 60 wt % (preferably 10 to 40 wt %) and an MFR (ASTM1238) of 1 to 40 g / 10 min (preferably 1 to 10 g / 10 min) under test conditions of a temperature of 230°C and a load of 21.2 N.

[0037] As the hydrogenated styrene-based thermoplastic elastomer for the intermediate layer 3, hydrogenated styrene-olefin rubber (hydrogenated styrene-olefin rubber) can be used, but other materials such as SEPS, SEP, SEBS, and SEEPS, which have excellent weather resistance, can also be used. For example, hydrogenated styrene-olefin rubber can be suitably used as the hydrogenated styrene-based thermoplastic elastomer for the intermediate layer 3.

[0038] [4-5] Modified Polyolefin: A modified polyolefin (adhesive polyolefin) with excellent adhesive properties can be used as the material for the intermediate layer 3. Adhesive polyolefins are polyolefins with functional groups that contribute to adhesion, and those in which the functional groups have been introduced by copolymerization or graft polymerization can be used. Specifically, those with an MFR (ASTM 1238) of 1 to 40 g / 10 min (preferably 1 to 10 g / 10 min) under test conditions of a temperature of 190°C and a load of 21.2 N are suitable.

[0039] [4-6] Other Block Copolymers The block copolymer for the intermediate layer 3 can be any one of the resins listed above, or a combination of two or more resins. By forming the intermediate layer 3 using these block copolymers, peeling between the core layer 1 and the clad layer 2 can be suppressed.

[0040] [5] Shape of the light guide rod In this embodiment, the thermoplastic resin molded body F is in the shape of a round rod, but it can also be molded into a rod shape with a rectangular cross section or a complex cross section. The shape of the thermoplastic resin molded body F also includes a plate-like shape with a large aspect ratio of the cross section.

[0041] "Method of Manufacturing Light Guide Rod" Next, a method of manufacturing the light guide rod B will be described. The resins of the core layer 1, intermediate layer 3, and cladding layer 2 are heated to a predetermined temperature through the mold of an extrusion molding machine to melt them, and are co-extruded simultaneously to form a co-extrusion mold. The three layers are then cooled and shaped in an integrated state, and then cut to a predetermined length to manufacture the rod.

[0042] Second Embodiment "Configuration of a Light Guide Rod Having a Peel-Preventing Layer" [1] Basic Configuration of a Light Guide Rod Next, a second embodiment of the present invention will be described below with reference to FIG. 3. In the figure, the reference numeral 4 indicates a peel-preventing layer. In this embodiment, a clad layer 2 is formed on the outer periphery of a core layer 1 without an intermediate layer, and a peel-preventing layer 4 is provided on the outer periphery of the clad layer 2 to form a light guide rod B. This allows the peel-preventing layer 4 to suppress peeling between the core layer 1 and the clad layer 2. A styrene-based elastomer can be suitably used as the main material of the peel-preventing layer 4, but other resins can also be used. The conditions for the resin material that is the main material of the core layer 1 and the resin material that is the main material of the clad layer 2, as well as the manufacturing method by co-extrusion molding, are the same as those in the first embodiment.

[0043] Other Embodiments In the side-emitting type light guide rod B, a light diffusion layer made of polymethylpentene containing a diffusing agent or titanium oxide can be further formed on the outside of the cladding layer 2 of the first embodiment or the anti-peeling layer 4 of the second embodiment. In addition, a coating layer, a light-shielding layer, etc. can also be formed as the outermost layer.

[0044] [Tests demonstrating the effects] Next, tests demonstrating the effects of the present invention will be described. In these tests, multiple samples (Examples 1 to 7 and Comparative Examples 1 and 2 below) made from different materials were prepared, and each sample was evaluated by a peel test, a heat cycle test, a light emission test, and a yellowing test. Each test method and the manufacturing conditions for each sample are described below.

[0045] "Peeling test method" A light guide rod sample was cut into a length of 500 mm using a laser cutter, and the adhesion state of the core layer and clad layer was visually checked. As a result, those that did not peel were rated as "Good", those that peeled only at the end were rated as "Good", and those that peeled all over were rated as "Poor".

[0046] "Heat cycle test method" A light guide rod sample cut to a length of 500 mm using a laser cutter was placed in a high temperature and humidity environment (80°C, 90% RH) for 2 hours, then exposed to room temperature for 2 hours, placed in a low temperature environment (-30°C) for 2 hours, and then exposed to room temperature for another 2 hours, which constituted one cycle. After repeating this cycle for 10 cycles, the adhesion state of the core layer and clad layer was visually checked. As a result, samples that did not peel were evaluated as "Good", and samples that peeled were evaluated as "Poor".

[0047] "Luminescence test method" Light was applied from a white LED light source to the end of a light guide rod cut to a length of 300 mm using a laser cutter, and the light emission state of the light guide rod was visually confirmed. As a result, samples that emitted light throughout the length were rated as "Good", samples that emitted light overall but with poor light emission were rated as "Good", and samples that did not emit light overall were rated as "Poor".

[0048] "Yellowing test method" Light was applied from a white LED light source to the end of a light guide rod cut to a length of 300 mm using a laser cutter, and the yellowing of the light emitted from the light guide rod was visually confirmed. As a result, no yellowing was evaluated as "Good", slight yellowing was evaluated as "Good", and obvious yellowing was evaluated as "Poor".

[0049] 1 and 2, a light guiding rod B in the shape of a round rod (diameter: 3.5 mm) was composed of a core layer 1, a cladding layer 2, and an intermediate layer 3 therebetween. The transparent resin of the core layer 1 was an acrylic thermoplastic elastomer with an MFR of 3.1 g / 10 min, a flexural modulus of 400 MPa, a tensile stress of 19 MPa, and a Shore A of 92 under test conditions of a temperature of 190°C and a load of 2.16 kg, and the material of the cladding layer 2 was polymethylpentene with an MFR of 27 g / 10 min, a melting point of 223°C, and a flexural modulus of 530 MPa under test conditions of a temperature of 260°C and a load of 5 kg. The light guide rod B was produced by co-extrusion molding using an acrylic thermoplastic elastomer with an MFR of 53 g / 10 min under test conditions of a temperature of 190°C and a load of 2.16 kg, an MFR of 650 g / 10 min under test conditions of a temperature of 230°C and a load of 2.16 kg, a tensile stress of 3.6 MPa, and a Shore A of 68 as the material for the intermediate layer 3.

[0050] "Example 2" In Example 2, instead of the material of the intermediate layer 3 in Example 1, a light guide rod B was produced by co-extrusion molding using an acrylic thermoplastic elastomer with an MFR of 4.8 g / 10 min under test conditions of a temperature of 190°C and a load of 2.16 kg, an MFR of 93 g / 10 min under test conditions of a temperature of 230°C and a load of 2.16 kg, a tensile stress of 9.3 MPa, and a Shore A of 73.

[0051] Example 3 In Example 3, instead of the material of the intermediate layer 3 in Example 1, a light guide bar B was produced by co-extrusion molding using an ionomer having an MFR of 0.9 g / 10 min under test conditions of a temperature of 190° C. and a load of 2.16 kg.

[0052] Example 4 In Example 4, instead of the material of the intermediate layer 3 in Example 1, a styrene-based elastomer with an MFR of 24 g / 10 min under test conditions of a temperature of 190°C and a load of 21.2 N was used to produce a light guide rod B by co-extrusion molding.

[0053] "Example 5" In Example 5, instead of the material of the intermediate layer 3 in Example 1, a hydrogenated styrene-olefin rubber with a styrene content of 18 wt% and an MFR of 5.0 g / 10 min under test conditions of a temperature of 230°C and a load of 21.2 N was used to produce a light guide rod B by co-extrusion molding.

[0054] "Example 6" In Example 6, instead of the material of the intermediate layer 3 in Example 1, a light guide rod B was produced by co-extrusion molding using a modified polyolefin (adhesive polyolefin) with an MFR of 2 g / 10 min under test conditions of a temperature of 190°C and a load of 21.2 N.

[0055] Example 7 In Example 7, as shown in Figure 3, a light guide rod B in the shape of a round rod (diameter: 3.5 mm) was composed of a core layer 1, a cladding layer 2, and a peel-preventing layer 4 on the outside of the cladding layer 2. The transparent resin of the core layer 1 was an acrylic thermoplastic elastomer with an MFR of 3.1 g / 10 min and a flexural modulus of 400 MPa under test conditions of a temperature of 190°C and a load of 2.16 kg, and the material of the cladding layer 2 was polymethylpentene with an MFR of 27 g / 10 min, a melting point of 223°C, and a flexural modulus of 530 MPa under test conditions of a temperature of 260°C and a load of 5 kg. A styrene elastomer was used as the material of the peel-preventing layer 4, and the light guide rod B was produced by co-extrusion molding.

[0056] Comparative Example 1 In Comparative Example 1, a light guide rod (diameter: 3.5 mm) was made up of a core layer and a clad layer (not shown). The core layer was made of an acrylic thermoplastic elastomer with an MFR of 3.1 g / 10 min and a flexural modulus of 400 MPa under test conditions of a temperature of 190°C and a load of 2.16 kg. The clad layer 2 was made of a fluorine-based resin, and the light guide rod B was produced by co-extrusion molding.

[0057] "Comparative Example 2" In Comparative Example 2, instead of the clad layer material of Comparative Example 1, polymethylpentene having an MFR of 27 g / 10 min, a melting point of 223°C, and a flexural modulus of 530 MPa under test conditions of a temperature of 260°C and a load of 5 kg was used, and light guide rod B was produced by co-extrusion molding.

[0058] The manufacturing conditions for each sample of Examples 1 to 7 and Comparative Examples 1 and 2 are summarized in the table below.

[0059] <Results of Peel Test> Next, a peel test was performed on the samples of Examples 1 to 7 and Comparative Examples 1 and 2. Peeling occurred overall in the sample of Comparative Example 2, in which a clad layer using polymethylpentene was formed directly on the outside of the core layer, but peeling did not occur in the samples of Examples 1 to 5, in which an intermediate layer was formed, and peeling only occurred at the edges in the samples of Examples 6 and 7. This confirmed that peeling was less likely to occur in Examples 1 to 7 than in Comparative Example 2.

[0060] <Results of Heat Cycle Test> Next, a heat cycle test was performed on the samples of Examples 1 to 5. No peeling occurred in the samples of Examples 1 to 5. This confirmed that Examples 1 to 5 have excellent resistance to peeling due to temperature changes.

[0061] <Results of the Light Emission Test> Next, a light emission test was conducted on the samples of Examples 1 to 7 and Comparative Examples 1 and 2. As with the sample of Comparative Example 1, the samples of Examples 1 to 5 emitted light from the entire light guide rod and the light emission state was good, whereas the sample of Example 7 emitted light from the entire rod but the light emission state was poor. Furthermore, the entire light guide rod of Example 6 did not emit light. This confirmed that the samples of Examples 1 to 5 had excellent light emission performance. However, the sample of Comparative Example 2 had severe peeling, so the light emission test could not be evaluated.

[0062] <Results of Yellowing Test> Next, the state of yellowing during light emission was checked for the samples of Examples 1 to 7 and Comparative Examples 1 and 2. No yellowing occurred in the samples of Examples 1 to 2 and 5 and Comparative Examples 1 and 2, whereas slight yellowing occurred in the samples of Examples 3 and 7. Furthermore, obvious yellowing occurred in the samples of Examples 4 and 6. This confirmed that Examples 1 to 2 and 5 have excellent yellowing suppression effects. The test results are summarized in a table below.

[0063] 1 Core layer 2 Clad layer 3 Intermediate layer 4 Anti-peeling layer B Light guide rod

Claims

1. A light guide rod comprising a central core layer primarily made of transparent resin and an outer clad layer primarily made of resin with a lower refractive index than the core layer, wherein a non-fluorine-based resin is used for the clad layer.

2. The light guide rod according to claim 1, wherein the core layer is mainly made of an acrylic resin.

3. A light guide rod according to claim 1 or 2, wherein the clad layer is mainly made of polymethylpentene.

4. A light guide rod according to claim 1 or 2, wherein an intermediate layer is provided between the core layer and the clad layer, and the intermediate layer is mainly made of a block copolymer.

5. The light guide rod according to claim 4, wherein the block copolymer of the intermediate layer is at least one of a styrene elastomer, a hydrogenated styrene thermoplastic elastomer, and a modified polyolefin.

6. A light guide rod as described in claim 4, wherein the block copolymer of the intermediate layer is an acrylic thermoplastic elastomer having a lower tensile stress at 100% elongation as specified in ISO 37 than the main material of the core layer.

7. The light guide rod according to claim 4, wherein the block copolymer used in the intermediate layer is an acrylic thermoplastic elastomer having a lower hardness than the main material of the core layer.

8. The light guide rod according to claim 4, wherein the block copolymer in the intermediate layer is a hydrogenated styrene-olefin rubber.

9. A light guide rod according to claim 1 or 2, wherein an intermediate layer is provided between the core layer and the clad layer, and the intermediate layer is made primarily of an ionomer.

10. A light guide rod according to claim 1 or 2, wherein an anti-peeling layer is provided on the outer periphery of the cladding layer.

11. The light guide rod according to claim 10, wherein the anti-peeling layer is mainly made of a styrene-based elastomer.

12. A light guide rod as described in claim 1 or 2, wherein the core layer is made of a material in which a hard acrylic resin is mixed with an acrylic elastomer, and the mixing ratio is within the range of 95:5 to 50:50.

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