End face light-emitting type light guide rod and manufacturing method thereof

Abstract

[Problem] To provide: an end-face light-emitting type light guide rod in which a light-emitting element and a light-emitting part can be arranged at different positions without causing light to leak from a peripheral surface part, and in which the light-emitting element and the light-emitting part can be arranged at different positions; and a method for manufacturing the end-face light-emitting type light guide rod at low cost. And light emitted from the light-emitting element can be efficiently guided. [Solution] An end face light-emitting type light guide rod (100) is provided with: a rod-shaped core layer (1) having a translucent resin as a main material; and a cladding layer (2) which is disposed on the outer periphery of the core layer (1) and which is mainly composed of a resin having a refractive index smaller than that of the core layer (1), and which emits light incident from one end surface (111) of the core layer (1) from the other end surface (2), and is configured in such a manner that a light shielding layer (3) is provided on the outer periphery of the cladding layer (2). The light-shielding layer (3) is mainly composed of a resin having the property of absorbing the wavelength of light penetrating through the core layer (1), and the light-shielding layer (3) and the cladding layer (2) are integrally fused.

Description

Technical Field

[0001] The present invention relates to an end-face emitting light guide rod and a method for manufacturing the same. The end-face emitting light guide rod can arrange a light emitting element and a light emitting portion at different positions by emitting light incident from one end face from another end face. Background Art

[0002] Most electrical products such as industrial machinery, electrical products, and automobiles have indicators that emit light of a predetermined color for the purpose of notifying the operating status or for decoration. Among the light-emitting elements of these indicators, LEDs (light-emitting diodes) are mostly used from the perspective of reducing current consumption and extending life. In order to make LEDs emit light, it is necessary to have a printed circuit board with a circuit for driving the LED, wiring, and peripheral components such as a bracket for fixing the LED. However, due to the size of the product and the space where the indicator is mounted, it is sometimes difficult to arrange the LED in the part that becomes the light-emitting part.

[0003] In products with such constraints, light emitted from an LED is sometimes guided to a light-emitting portion by a light-guiding component (so-called light guide). Generally, a light guide is designed by calculating reflection and diffusion in order to effectively guide light emitted from an LED. That is, since the shape is optimized for each product, a designed light guide can only be used for one product and cannot be used in common for multiple different products.

[0004] To solve the above problem, there is a method as follows: LEDs are arranged in places with ample space, and light emitted from the LEDs is guided by light guide rods to emit light at any place. Light guide rods are generally represented by optical fibers, which are thin and flexible and can be slightly bent, so they can be arranged in a winding manner even in narrow places.

[0005] The light guide rod transmits light through the core layer, and guides light incident from one end face of the light guide rod to the other end face and emits it. Here, light is not only incident parallel to the light guide rod, but sometimes also incident at a specified angle. However, among such light, light with an angle exceeding the critical angle is totally reflected at the boundary surface due to the difference in refractive index between the core layer and the material outside the core layer. As a result, the light intensity will not be attenuated by scattering at the boundary surface, and the light can be guided to a distant place without attenuating the light.

[0006] As a specific structure of the light guide rod, there is a structure that utilizes the difference in refractive index between the core layer and the air layer outside it. However, if the core layer is exposed to the outside, the boundary surface between the core layer and the air layer is easily damaged during use, which causes the light to be scattered and attenuated due to the unevenness caused by the damage. Therefore, most of them use a structure in which a layer of a predetermined thickness called a cladding layer (covering layer) with a lower refractive index than the core layer is covered on the periphery of the core layer so that the boundary surface is not exposed.

[0007] However, since the LED used as a light-emitting element has a wide directivity of the light emitted in its structure, light at an angle lower than the critical angle based on the difference in the refractive index between the core layer and the cladding also enters the core layer. In addition, sometimes a part of the light reaching the boundary surface of the core layer and the cladding will be scattered. In such light, the light at an angle lower than the critical angle does not undergo total reflection at the boundary surface of the core layer and the cladding, but is refracted and enters the cladding from the core layer. The light entering the cladding reaches the boundary surface between the cladding and the external air layer, but most of the light will be emitted from the cladding to the outside. This leaked light will illuminate unnecessary places for the product, which is not preferred in appearance and function.

[0008] Therefore, conventionally, a light guide rod configured to prevent light from leaking from the cladding to the outside has been developed. Patent Document 1 discloses a plastic optical fiber technology in which the cladding "is composed of a transparent inner cladding and a colored opaque outer cladding."

[0009] In the technology of Patent Document 1, first, "an inner cladding resin is extruded into a tubular shape, and at the same time, an outer cladding resin containing a colorant in the resin fused with the inner cladding resin is extruded concentrically on the outer circumference thereof, thereby forming a tubular cladding in which the inner cladding and the outer cladding are fused and integrated." Then, the cladding is manufactured by a method of "supplying a core resin precursor to the cladding tube under pressure while heating and polymerizing it." That is, the core layer and the cladding layer are not formed at the same time, but the cladding layer is previously formed into a tubular shape, and a resin serving as the core layer is injected into the hollow interior under pressure to form the cladding layer. Previous technical literature Patent Literature

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 1-229206 Summary of the invention Problems to be solved by the invention

[0011] However, the prior art described in Patent Document 1 requires pre-molding of the tubular cladding layer, which can maintain the tubular shape after molding, and needs to have a thickness and strength that can withstand the pressurized injection of the resin that becomes the core layer. Therefore, the cladding layer and the light shielding layer cannot be made too thin. When the cladding layer and the light shielding layer become thicker, there is a problem that the diameter of the entire light guide rod becomes larger, the flexibility decreases, and it is difficult to install it inside the product. In addition, when the design upper limit of the outermost diameter of the light guide rod is determined, the cladding and the light shielding layer must be thickened on the one hand, and the diameter of the core layer must be relatively small on the other hand. Therefore, there is a problem that the area of ​​the end face of the core layer on which the light emitted from the LED is incident becomes smaller, the incident efficiency is reduced, and the luminous intensity of the light-emitting portion is reduced.

[0012] Furthermore, in the embodiment described in Patent Document 1, since the cladding is relatively thin, it is considered that the cladding will expand when the core layer is pressurized and injected. Therefore, there is a problem that the diameter of the entire light guide rod becomes thicker than the diameter of the single cladding, and there is a possibility that the outermost diameter of the light guide rod acceptable in design may not be satisfied. Furthermore, since the forming of the clad layer and the forming of the core layer must be performed as separate processes, there is also a problem that the manufacturing efficiency is deteriorated and the product price increases.

[0013] The present invention is completed in view of the above-mentioned problems, and its purpose is to provide an end-face emitting light guide rod in which light will not leak from the peripheral surface, the light-emitting element and the light-emitting part can be arranged at different positions, and the light emitted from the light-emitting element can be efficiently guided. Another object of the present invention is to provide a method for manufacturing an end-face emitting light guide rod, which can manufacture the end-face emitting light guide rod at a low cost. Means of solving problems

[0014] Means taken by the present inventors to solve the above-mentioned problems will be described below. The basic structure of the end-face emitting light guide rod of the present invention is: it has a rod-shaped core layer mainly made of a light-transmitting resin, and a cladding layer mainly made of a resin arranged on the periphery of the core layer and having a smaller refractive index than the core layer. It is an end-face emitting light guide rod having the function of emitting light incident from one end face of the core layer from the other end face.

[0015] Here, the so-called "light-transmitting" means that it has a sufficient degree of light transmittance to guide light for the product using the light guide rod, and includes not only visible light, but also light other than visible light such as ultraviolet rays and infrared rays for decorative and functional purposes. Furthermore, "serving as a main material" means that the resin has the highest ratio in the whole, and also includes the case where other materials are contained.

[0016] The end-emitting light guide rod of the present invention is characterized in that, relative to the above-mentioned basic structure, a shading layer made mainly of a resin having the property of absorbing the wavelength of light passing through the above-mentioned core layer is further provided on the periphery of the above-mentioned cladding, and the above-mentioned shading layer is fused integrally with the above-mentioned cladding. By providing a light shielding layer on the periphery of the cladding, light incident at an angle equal to or less than the critical angle and part of light scattered at the boundary between the core layer and the cladding are absorbed, thereby preventing light from leaking from the cladding to the outside.

[0017] Furthermore, since the light shielding layer and the cladding layer are integrally formed by melting, even if they have different linear expansion coefficients, the problem of separation due to the difference in the amount of expansion and contraction of each layer caused by changes in ambient temperature etc. is unlikely to occur. In addition, by forming it into a fused whole, it is easier to ensure strength and can be formed thinner than when it is formed separately. Therefore, the diameter of the light guide rod as a whole can be reduced, it is easy to bend softly, and it is easy to assemble into the product. In addition, if the strength is the same, each layer can be made thinner, and the diameter of the core layer can be relatively increased, so that light emitted at a large angle can also enter the core layer, which can improve the incident efficiency.

[0018] Here, the so-called "property of absorbing the wavelength of light passing through the core layer" is not limited to black that absorbs the entire wavelength range of visible light. In the case where the light passing through the core layer is a single wavelength or a specific range of wavelengths, it also includes the property of only absorbing light of these wavelengths and reflecting or transmitting light of other wavelengths.

[0019] In order to solve the above-mentioned problems, as a method adopted by the present invention, in addition to the above-mentioned means, the thickness of the cladding layer may be set to 0.15 mm or less, and the thickness of the light shielding layer may be set to 0.25 mm or less. The outermost diameter of the light guide rod is sometimes required to be set to a specific diameter based on the size of the space of the product to be installed and the specifications of the ferrule when the ferrule is connected. If the outermost diameter is the same, by setting the thickness of the cladding to less than 0.15 mm and the thickness of the light shielding layer to less than 0.25 mm, that is, by making both very thin, the diameter of the core layer can be relatively increased, thereby improving the incident efficiency. In addition, when the core layer diameter is predetermined according to the size of the light-emitting element, the outermost diameter of the light guide rod can be further reduced, so that it can be flexibly bent and easily installed on the product.

[0020] In addition, a resin containing 0.01 wt % or more of carbon black may be used in the light-shielding layer. Carbon black is a fine carbon particle, and has the property of strongly absorbing the entire wavelength range of visible light. If the content of the carbon black is less than 0.01% by weight, the proportion of light passing through the light-shielding layer increases, and it is difficult to obtain sufficient light-shielding properties. However, by containing 0.01% by weight or more of carbon black in the resin constituting the light-shielding layer, sufficient light-shielding properties can be obtained regardless of the color of the light-emitting element used. On the other hand, if the carbon black content exceeds 5.0 wt % of the resin constituting the light shielding layer, surface cracks may occur during molding. Therefore, the content of carbon black is preferably 5.0 wt % or less of the resin constituting the light shielding layer.

[0021] When the above means are adopted, the core layer may be formed by using a resin mainly composed of an acrylic elastomer and the cladding layer may be formed by using a resin mainly composed of a fluorine-based resin. In this case, the light-shielding layer may be formed by using a resin having a glass transition temperature that allows co-extrusion molding with the cladding layer. By using a resin with acrylic elastomer as the main material in the core layer, the light guide rod can be flexibly bent and can be bent according to the shape of the product. In addition, by using a fluorine-based resin in the cladding and using a resin with a glass transition temperature that can be co-extruded with the cladding in the light-shielding layer, it can be melt-integrated in the molding process under the same conditions.

[0022] Furthermore, by setting the thickness of the light-shielding layer to be greater than 0.1 mm, in a three-point bending test based on JIS K6911, the value of a in the following formula representing the relationship between the overall diameter of the light guide rod and the bending modulus can be greater than 550 and less than 3000. [Number 1] y=-43.054x+a y: bending elastic modulus [MPa]; x: diameter of the entire light guide rod [mm].

[0023] By setting the thickness of the light shielding layer to be 0.1 mm or more, it is possible to reliably prevent light from leaking from the peripheral surface, and at the same time, the light shielding layer becomes hard due to the carbon black contained in the light shielding layer. However, by setting the bending modulus during three-point bending so that the value of a in the above formula is within the range of 550 or more and less than 3000, a light guide rod that is easily bendable and flexible can be obtained, and light leakage from the peripheral surface can be reliably prevented.

[0024] Here, in a method for manufacturing a light guide rod having a rod-shaped core layer mainly made of a light-transmitting resin and a cladding layer mainly made of a resin arranged on the periphery of the core layer and having a smaller refractive index than the core layer, a manufacturing method with the following structure (characteristics) can be adopted. In the manufacturing method of the present invention, a mold is used, which is configured so that a light shielding layer is also provided on the periphery of the cladding layer, and the light shielding layer is mainly made of a resin having a property of absorbing the wavelength of light passing through the core layer. The core layer, the cladding layer and the light shielding layer are integrally molded by co-extrusion molding.

[0025] As described above, in addition to the core layer and the cladding layer, the light shielding layer mainly made of a resin having the property of absorbing the wavelength of light transmitted through the core layer can be melt-integrated in a molding process under the same conditions by co-extrusion molding using a single die. Thus, as described above, the diameter of the core layer can be relatively increased while forming a thin cladding layer and a light shielding layer, thereby improving the incident efficiency. In addition, since the cladding layer and the light shielding layer are melt-integrated in a molding process under the same conditions, the manufacturing process can be simplified. Effects of the Invention

[0026] As described above, in the end-emitting light guide rod of the present invention, a light shielding layer mainly made of a resin having a property of absorbing the wavelength of light transmitted through the core layer is provided on the periphery of the cladding layer. With these structures, since the light leaking to the outside of the cladding is absorbed by the light shielding layer, it is possible to prevent the light from leaking to the outside from the cladding. In addition, by melting the cladding and the light shielding layer into one piece, even if each layer is formed thinner, the shape can be maintained, so the overall diameter of the light guide rod can be reduced, and it can become softer and easier to bend. In addition, since the diameter of the core layer can be relatively increased, the incident efficiency can be improved. Through the above-mentioned effects, the present invention has the following effects: light will not leak from the peripheral surface, the light-emitting element and the light-emitting portion can be arranged at different positions, and on this basis, an end-face emitting light guide rod can be formed that can efficiently guide the light emitted from the light-emitting element.

[0027] In addition, in the manufacturing method of the end-light-emitting light-guiding rod of the present invention, the following structure is also adopted: in addition to the core layer and the cladding layer, a light-shielding layer mainly made of a resin having the property of absorbing the wavelength of light passing through the core layer is also co-extruded through a single die. With this structure, it is possible to melt-integrate in the molding process under the same conditions. Due to the above-mentioned effects, in the present invention, there is an effect that the end-face emitting light guide rod can be manufactured at low cost. BRIEF DESCRIPTION OF THE DRAWINGS [ Figure 1 ] is a stereoscopic view and an enlarged cross-sectional view showing the end-face emitting light guide rod of the present invention. [ Figure 2 ] is an explanatory diagram showing the state of light traveling within the end-face emitting light guide rod of the present invention. [ Figure 3 ] is a cross-sectional view showing an example of a product using the end-face emitting light guide rod of the present invention. [ Figure 4 ] is an explanatory diagram showing the manufacturing method of the end-face emitting light guide rod of the present invention. [ Figure 5] are a stereoscopic view and an enlarged cross-sectional view showing a modified example of the end-face emitting light guide rod of the present invention. [ Figure 6 ] is a graph showing the distribution of the bending elastic modulus of the end-face emitting light guide rod of the present invention and the previous comparative example. DETAILED DESCRIPTION

[0029] The following is based on Figures 1 to 4 Embodiments of the present invention will be described. In addition, the drawings are schematically shown for the purpose of explanation, and the sizes and shapes are different from the actual ones.

[0030] like Figure 1 As shown, an end-emitting light guide rod 100 as an example of an embodiment of the present invention includes: a rod-shaped core layer 1 mainly made of a light-transmitting resin; and a cladding layer 2 mainly made of a resin arranged on the periphery of the core layer 1 and having a lower refractive index than the core layer 1. Furthermore, a light shielding layer 3 mainly made of a resin having a property of absorbing the wavelength of light transmitted through the core layer is provided on the outer peripheral side of the cladding layer 2 . The core layer 1 , the cladding layer 2 , and the light shielding layer 3 are melt-integrated by a production method described later.

[0031] exist Figure 1 In the embodiment, the main material of the core layer 1 uses a block copolymer of methyl methacrylate-n-butyl acrylate-benzyl acrylate as a soft acrylic elastomer, but one or more of the following can be appropriately used: a block copolymer of methyl methacrylate and butyl acrylate (MMA-BA block copolymer) as a thermoplastic elastomer, or a block copolymer of methyl acrylate and butyl acrylate, or an acrylic block copolymer composed of methyl methacrylate (methyl acrylate), acrylate and aromatic acrylate, polymethyl methacrylate (PMMA: refractive index 1.49), thermoplastic polyurethane (TPU: refractive index 1.49), cyclic olefin (refractive index 1.50), amorphous polyamide (PA: refractive index 1.51), polycarbonate (PC: refractive index 1.56). In addition, a mixed material of a flexible acrylic elastomer and a hard acrylic resin having a glass transition temperature (Tg) of room temperature (25°C) or above can be used. When the content ratio of the acrylic elastomer is higher than that of the hard acrylic resin, the flexibility becomes higher. In addition, other thermoplastic resins or thermosetting resins can be used as long as they are extrudable resins.

[0032] Regarding the shape of the core layer 1, Figure 1In the embodiment, a core layer with a circular cross-sectional shape is used, and the diameter is arbitrary, preferably 6.3 mm, 3.5 mm, 2.5 mm, etc., which matches the size of the light-emitting surface of the cannonball-shaped LED or chip LED. The shape of the core layer 1 can be a fish cake-shaped semi-elliptical shape or a shape that is easy to fit into the internal structure of the product. In addition, an elliptical shape, a semicircular shape, a polygonal shape, etc. can also be used. In addition, the core layer 1 is configured to be concentric with the cladding layer 2 and the light shielding layer 3, but the core layer 1 may be eccentric relative to the center of the cladding layer 2 and the light shielding layer 3. In this case, the light shielding property relative to a specific direction can be improved, or it can be easily bent in only one direction.

[0033] On the other hand, Figure 1 In the embodiment, the main material of the cladding 2 uses a copolymer of ethylene and tetrafluoroethylene (ETFE: refractive index 1.40) as a fluorine-based resin, but one or more of the following can be used appropriately: hexafluoropropylene, a copolymer of tetrafluoroethylene and ethylene (EFEP: refractive index 1.38), polyvinylidene fluoride (PVDF: refractive index 1.42), a copolymer of tetrafluoroethylene and perfluoroalkoxyethylene (PFA: refractive index 1.34), a copolymer of tetrafluoroethylene and hexafluoropropylene (FEP: refractive index 1.34), and polymethylpentene (TPX: refractive index 1.46). By using a fluorine-based resin with a small friction coefficient as the main material of the cladding 2 and using the same resin in the light shielding layer 3 described later, it is easy to insert or sandwich it into the internal structure of the product and meander. In addition, as long as it is a resin that can be extruded and has a lower refractive index than the core layer, thermoplastic resins such as polymethyl methacrylate (PMMA: refractive index 1.49), thermoplastic polyurethane (TPU: refractive index 1.49), cyclic olefin (refractive index 1.50), amorphous polyamide (PA: refractive index 1.51) or other thermosetting resins may also be used.

[0034] Regarding the shape of the cladding 2, Figure 1 In the embodiment, it is sufficient to form a prescribed thickness on the periphery of the core layer 1. In order to reduce the overall diameter of the light guide rod to make it easier to bend, or to relatively increase the diameter of the core layer 1 to improve the incident efficiency, the thickness is preferably less than 0.15 mm, more preferably less than 0.1 mm, and more preferably less than 0.05 mm. The layer structure of the cladding 2 may be a single-layer structure or a multi-layer structure composed of a plurality of claddings 2·2···.

[0035] When the refractive index difference between the core layer 1 and the cladding layer 2 is 0.01 or more, total reflection is likely to occur, and light can be guided efficiently. The refractive index difference is more preferably 0.07 or more.

[0036] In addition, a resin containing 0.01 wt% of carbon black is used for the light shielding layer 3. Carbon black is a fine carbon powder with a particle size of several nanometers to hundreds of nanometers, and any carbon black can be used as long as it has the property of strongly absorbing a predetermined wavelength range of light. Carbon black composed of a single carbon atom can be used, and other carbon blacks having a composition with various functional groups bonded to the surface can also be used. From the viewpoint of light-shielding performance and prevention of molding defects such as cracks, the carbon black content is 0.01 wt% to 5.0 wt%, preferably 0.2 wt% to 5.0 wt%, and more preferably 0.8 wt% to 5.0 wt%. In addition, as the black coloring material contained in the shading layer 3, for example, copper oxide or iron oxide composite oxides, titanium black pigments, etc. can be used. If the light guided in the core layer 1 is, for example, monochromatic light composed of a specific narrow wavelength region, a colored pigment that only absorbs light in this wavelength region can also be used.

[0037] For the main material of the light-shielding layer 3, it is necessary that it can be melt-molded together with the cladding 2 by co-extrusion molding. As mentioned above, the copolymer of ethylene and tetrafluoroethylene (ETFE) which is the same fluorine-based resin as the cladding 2 can be used. In addition, one or more of the following can be appropriately used: hexafluoropropylene, copolymer of tetrafluoroethylene and ethylene (EFEP), polyvinylidene fluoride (PVDF), copolymer of tetrafluoroethylene and perfluoroalkoxyethylene (PFA), copolymer of tetrafluoroethylene and hexafluoropropylene (FEP), etc. In addition, as long as it is a resin that can be extruded, thermoplastic resins such as soft polyvinyl chloride (PVC), olefin thermoplastic elastomer (TPO), styrene thermoplastic elastomer (TPS), thermoplastic polyurethane (TPU), thermoplastic elastomer (TPE), polyamide thermoplastic elastomer (TPA) or other thermosetting resins can be used. Other resins may also be used as long as they have the same glass transition temperature and can be co-extruded with the cladding 2 by co-extrusion molding.

[0038] Regarding the shape of the light shielding layer 3, Figure 1 In the embodiment, it is sufficient to form the cladding 2 with a specified thickness at the periphery. Considering the reasons for selecting the thickness of the cladding 2 and the balance for obtaining sufficient light-shielding properties, the thickness is preferably less than 0.25 mm, and more preferably less than 0.2 mm. The layer structure of the light shielding layer 3 may be a single layer structure or a multilayer structure composed of a plurality of light shielding layers 3·3 . . . .

[0039] It should be noted that the purpose of the end-face emitting light guide rod 100 of the present invention is to prevent light from being emitted from the peripheral surface and to emit light only from the end surface. Figure 1In the embodiment, light scattering agents such as titanium oxide are not contained in the core layer 1 and the cladding layer 2. However, since light emitted from the peripheral surface is blocked by the light shielding layer 3, a light scattering agent may be contained in the core layer 1 in order to emit uniform diffused light from the end surface.

[0040] In addition, when the end-face emitting light guide rod 100 of the present invention is not used outdoors in a state where it is exposed to sunlight, Figure 1 In the embodiment, it is not necessary to contain a colorant in the core layer 1. However, in the case of using an ultraviolet LED and a visible light LED in combination, since the ultraviolet light turns the core layer 1 yellow, the color tone sometimes changes when the visible light is emitted, so the core layer 1 may contain a blueing agent such as a blue pigment.

[0041] Next, based on Figure 2 The movement of light traveling inside the end-emitting light guide rod 100 of the present invention will be described. Figure 2 In the embodiment, light emitted by the light emitting element LED4 is incident on an end face 11 of the core layer 1. Among the incident light, parallel light 41 incident in a direction parallel to the length direction of the core layer 1 travels straight in the core layer 1. In addition, among the light incident at a predetermined angle relative to the length direction of the core layer 1, light 42 exceeding the critical angle is repeatedly totally reflected at the boundary surface between the core layer 1 and the cladding layer 2 and travels in the core layer 1.

[0042] However, light 43 below the critical angle is not totally reflected at the boundary surface between the core layer 1 and the cladding layer 2, but refracted and enters the interior of the cladding layer 2. In addition, even if the incident light is at an angle exceeding the critical angle, a lot of scattering will occur at the boundary surface between the core layer 1 and the cladding layer 2. Part of this scattered light travels toward the interior of the cladding 2. For this reason, the light that enters the interior of the cladding 2 reaches the boundary between the cladding 2 and the light-shielding layer 3. At this time, the particles of carbon black or colored pigment contained in the resin of the light-shielding layer 3 absorb the light that reaches the boundary between the cladding 2 and the light-shielding layer 3. Thus, by absorbing the light reaching the light shielding layer 3 from the cladding 2, it is possible to prevent the light from leaking to the outside and to return the light to the core 1. Therefore, it is possible to prevent the directivity of the light emitted from the end face from becoming an undesirable characteristic.

[0043] like Figure 3 As shown, the end-face emitting light guide rod 100 having the above-mentioned features is incorporated in a product 200 and constitutes a part of an indicator that emits light at an arbitrary location. exist Figure 3In the embodiment, the product 200 is, for example, a part of a housing of an electrical product. Most of the internal space of the product 200 is configured to be wide, but the space at the right end where the indicator is arranged becomes extremely narrow. If the LED 4 is arranged in such a narrow space, even if the LED 4 is a small chip LED, the printed circuit board 210 for driving the LED 4 cannot be arranged.

[0044] Therefore, the printed circuit board 210 equipped with the LED 4 is arranged in the large space portion of the product 200. The end-face emitting light guide rod 100 is arranged close to one end face 11 on the light-emitting surface of the LED 4. Then, the end-face emitting light guide rod 100 is made to meander inside the product 200 so that the other end face 12 is arranged opposite to the light-emitting unit 220.

[0045] By adopting such a structure, the light emitting unit 220 can be provided even in a narrow internal structure such as a printed circuit board 210 that cannot be configured with the LED 4 and the drive thereof, and any place can be used as an indicator. In addition, since the end-light emitting light guide rod 100 is flexible and its length can be easily changed, it is not necessary to design and manufacture a light guide as a light guide component for each product. Therefore, the end-light emitting light guide rod 100 can be used as a common component in a plurality of various products, which can reduce manufacturing costs and component management man-hours.

[0046] Next, based on Figure 4 The method for manufacturing the end-emitting light guide rod 100 of the present invention will be described. The end-emitting light guide rod 100 of the present invention is obtained by simultaneously melting and integrating the core layer 1, the cladding layer 2, and the light shielding layer 3 by co-extrusion molding. The manufacturing method of the present invention uses Figure 4 The manufacturing device 5 shown in the figure uses a mold 51 whose structure allows the core layer 1, the cladding layer 2 and the light shielding layer 3 to be concentric circles. Cylinders 52, 52' and 52" for injecting corresponding resins are respectively connected to the part of the mold 51 that becomes the core layer 1, the part that becomes the cladding layer 2, and the part that becomes the light shielding layer 3. Resins are injected into each hopper, and the molten resin is sent into the mold 51 by a screw.

[0047] In the mold 51, the core layer 1, the cladding layer 2 and the light shielding layer 3 are formed according to the shape of the mold by the molten resin, and these layers are melted and integrated and then extruded. After being extruded and formed in this way, they are cooled and solidified by the cooling water tank 53, pulled by the puller 54, and cut into a specified length by the cutter 55. As described above, by simultaneously melting and integrating the core layer 1 , the cladding layer 2 , and the light shielding layer 3 through co-extrusion molding, the end-emission type light guide rod 100 can be manufactured in one manufacturing process, and can be manufactured at low cost.

[0048] [Modifications] However, the end-face emitting light guide rod of the present invention is not limited to the above-mentioned embodiment, and may also be implemented in other ways. Figure 5 In the end-emitting light guide rod 101 of the modified example, Figure 1 The difference is that one end face 11 is polished into a convex lens shape. In order to improve the transmission efficiency of the light guide rod, it is necessary to make as much light as possible enter at an angle exceeding the critical angle. However, LEDs generally emit light in all directions from the semiconductor. The emitted light has a wider directivity, although its directivity is slightly reduced depending on the shape of the reflector or resin package. Therefore, if the end face of the core layer 1 is flat, a large proportion of the light below the critical angle enters the core layer 1, and the light cannot be totally reflected, so the efficiency of the light guide is reduced.

[0049] Therefore, if one end face 11 where light is incident is polished to form a convex lens, the light incident through the convex shape is refracted and the directivity becomes narrower. In other words, since the incident angle relative to the cladding 2 becomes larger, the proportion of light exceeding the critical angle becomes larger. Therefore, more light can be guided by total reflection.

[0050] It should be noted that in this modified example, the other end face 12 remains flat, but it can also be processed into a pear-shaped shape. By setting it in this way, the light emitted from the other end face 12 can be diffused. Therefore, when assembled into a product, there is no need to set a separate window component or lens component as an indicator, and the other end face 12 can be directly exposed as a window of the indicator.

[0051] As described above, the end-emitting light guide rod of the present invention allows light incident from one end face to be emitted from the other end face, so that the LED and the light-emitting part can be arranged at different positions even in a product having a structure in which the LED or its peripheral components cannot be assembled in the light-emitting part. In addition, by melting the light-shielding layer and the cladding together, it is possible to prevent light from leaking from the peripheral surface, and the cladding and the light-shielding layer can be formed as thin as possible. Therefore, the diameter of the light guide rod as a whole can be configured to be thin and flexible. On the other hand, if the entire light guide rod has the same diameter, the diameter of the core layer can be relatively increased, thereby improving the light incident efficiency and making the light-emitting portion brighter. Example

[0052] Next, a specific example of the light guide rod of the present invention and a comparative example of a light guide rod of the prior art were subjected to a bending resistance test and a three-point bending test, and the results were compared.

[0053] [Example 1] The overall diameter of Example 1 is 2.5 mm, and its structure is as follows: a core layer with a circular cross-section and a diameter of 2 mm is used, a cladding layer with a thickness of 0.05 mm is provided around the core layer, and a light shielding layer with a thickness of 0.2 mm is provided around the cladding layer. The core layer uses a colorless and transparent polymethyl methacrylate (PMMA) elastomer resin, the cladding layer uses a colorless and transparent tetrafluoroethylene-ethylene copolymer (ETFE resin), and the light shielding layer uses a fluorine-based resin in which the carbon black content in the entire product is 0.9 weight %.

[0054] [Example 2] The structure of Example 2 is the same as that of Example 1 except that the overall diameter is 2 mm and the diameter of the core layer is 1.5 mm.

[0055] [Example 3] The structure of Example 3 is the same as that of Example 1 except that the overall diameter is 3.5 mm and the diameter of the core layer is 3 mm.

[0056] [Example 4] The structure of Example 4 is the same as that of Example 1 except that the overall diameter is 4 mm and the diameter of the core layer is 3.5 mm.

[0057] [Example 5] The structure of Example 5 is the same as that of Example 1 except that the overall diameter is 6.3 mm and the diameter of the core layer is 5.8 mm.

[0058] [Comparative Example 1] The overall diameter of Comparative Example 1 was 2.04 mm, and the structure was such that a core layer with a circular cross section and a diameter of 2 mm was used, and a cladding layer with a thickness of 0.02 mm was provided around the core layer. It should be noted that no light shielding layer was provided. The core layer uses colorless and transparent PMMA resin, and the cladding layer uses colorless and transparent PVDF (polyvinylidene fluoride) resin.

[0059] [Comparative Example 2] The overall diameter of Comparative Example 2 was 3 mm, and the structure was as follows: a core layer with a circular cross section and a diameter of 2.98 mm was used, and a cladding layer with a thickness of 0.01 mm was provided around the core layer. It should be noted that no light shielding layer was provided. The core layer uses colorless and transparent PMMA resin, and the cladding layer uses colorless and transparent fluorine-based resin.

[0060] [Comparative Example 3] The overall diameter of Comparative Example 3 is 2.2 mm, and its structure is as follows: a core layer with a circular cross-section and a diameter of 0.98 mm is used, a cladding layer with a thickness of 0.01 mm is provided around the core layer, and a light shielding layer with a thickness of 0.6 mm is provided around the cladding layer. The core layer uses colorless and transparent PMMA resin, the cladding layer uses colorless and transparent fluorine resin, and the light shielding layer uses black polyethylene resin.

[0061] [Bending test] Three types of samples of the bending test, 100 mm, 200 mm, and 300 mm in length, were prepared under the above-mentioned conditions. The bending test method is as follows: Hold the two ends of the sample with your hands, fold it back 180 degrees so that one end is aligned with the other end, and then pinch the bent part with your fingers to press the folded part as tightly as possible. Do the same in the opposite direction and repeat alternately 5 times. The test samples were Example 1, Comparative Example 1 and Comparative Example 2, and the test was carried out with N=3 for each. In addition, the attenuation of the amount of transmitted light before and after the test was measured. The measurement was performed using a spectroradiometer, a red light source with a drive current of 300 mA and a light intensity of 3.634 lm, and the measurement was performed at a position 200 mm from the radiation end surface.

[0062] [Test results] Example 1: For any length of the sample, no breakage occurred after the test, and the light shielding layer had no cracks or fissures. The amount of light after the test was 92% of that before the test on average. On the other hand, Comparative Examples 1 and 2 broke when bent in the opposite direction during the first bending.

[0063] [3-point bending test] For each sample for the three-point bending test, a sample having a length of 100 mm was prepared under the above-mentioned conditions. The three-point bending test was performed according to JIS K 6911. The stroke and load of the pressure head are measured in the test, and the bending strain and bending stress are calculated to obtain a stress-strain curve. The bending modulus is calculated from the stress values ​​at 0.05% strain and 0.25% strain of the stress-strain curve (secant method). The bending modulus can also be calculated from the linear gradient of the load between predetermined strokes (tangent method).

[0064] [Test results] The test results of each sample are shown in the following table. [Table 1]

[0065] The bending elastic modulus of the above curve is plotted in a scatter plot, such as Figure 6 shown. The thickness of the cladding layer and the light shielding layer of Examples 1-5 are the same, but the diameter of the core layer is different. Since the core layer uses an acrylic elastomer and is therefore soft, the larger the diameter of the core layer and the greater the proportion of the core layer to the whole, the more the bending modulus tends to decrease.

[0066] In the embodiment of the present invention, the thickness of the light shielding layer is 0.2 mm, which is relatively thick. Since it contains carbon black, it is not easy to bend. However, according to the results of the above bending test and the three-point bending test, in the embodiment of the present invention, the light shielding property is improved by adding a predetermined amount of carbon black to the fluorine-based resin, and the material and diameter of the core layer are skillfully adjusted to distribute the carbon black in the fluorine-based resin. Figure 6 The range is such that the value of a in the following formula is greater than or equal to 550 and less than 3000. [Number 2] y=-43.054x+a y: bending elastic modulus [MPa]; x: diameter of the entire light guide rod [mm].

[0067] When the value of a is 550 or more and less than 3000, it is not only soft and easy to bend, but also will not break or damage the light shielding layer due to bending to cause light leakage. In particular, from the viewpoint of both flexibility and bending resistance, the value of a is preferably 600 or more and less than 2000, more preferably 650 or more and less than 1000, and further preferably 700 or more and less than 900.

[0068] Thus, in the present invention, although the light-shielding layer containing carbon black having light-shielding properties and curability is provided, it has the characteristics of being soft and not easy to break. Therefore, light will not leak from the peripheral surface, and the light-emitting element and the light-emitting part can be arranged at different positions, and on this basis, the light emitted from the light-emitting element can be efficiently guided.

[0069] Description of Reference Numerals 100, 101 end-emitting light guide rod 1 Core layer 11 One end face 12 The other end 2 Cladding 3 Shading layer 4 LED 41 parallel light 42 Light exceeding the critical angle 43 Light below the critical angle 5. Manufacturing equipment 51 Mould 52 cylinders 53 cooling water tank 54 Puller 55 Knife 200 Products 210 Printed substrate 220 Light-emitting part

Claims

1. An end-emitting light-guiding rod, comprising: a rod-shaped core layer mainly made of a light-transmitting resin; and a cladding layer mainly made of a resin arranged on the periphery of the core layer and having a smaller refractive index than the core layer, wherein light incident from one end face of the core layer is emitted from the other end face, characterized in that: A light shielding layer is further provided on the periphery of the cladding layer, wherein the light shielding layer is mainly made of a resin having a property of absorbing the wavelength of light passing through the core layer. The light shielding layer and the cladding layer are fused together to form an integral whole.

2. The end-emitting light guide rod according to claim 1, characterized in that: The thickness of the cladding layer is less than 0.15 mm, and the thickness of the light shielding layer is less than 0.25 mm.

3. The end-emitting light guide rod according to claim 1 or 2, characterized in that: The light shielding layer uses a resin containing 0.01 wt % or more of carbon black.

4. The end-emitting light guide rod according to claim 1 or 2, characterized in that: The core layer uses a resin mainly composed of acrylic elastomer, and the cladding layer uses a resin mainly composed of fluorine resin. On the other hand, the light shielding layer uses a resin having a glass transition temperature that can be co-extruded with the cladding layer.

5. The end-emitting light guide rod according to claim 3 or 4, characterized in that: The thickness of the light shielding layer is greater than 0.1 mm. In a three-point bending test, the value of a in the following formula representing the relationship between the diameter of the entire light guide rod and the bending elastic modulus is 550 or more and less than 3000, y=-43.054x+a y: bending elastic modulus [MPa]; x: diameter of the entire light guide rod [mm].

6. A method for manufacturing an end-emitting light guide rod, wherein: The end-light-emitting light-guiding rod comprises: a rod-shaped core layer mainly made of a light-transmitting resin; and a cladding layer mainly made of a resin arranged on the periphery of the core layer and having a smaller refractive index than the core layer, and emits light incident from one end face of the core layer from the other end face. The manufacturing method is characterized in that A mold is used, and the mold is configured such that: a light shielding layer is further provided on the periphery of the cladding layer, and the light shielding layer is mainly made of a resin having a property of absorbing the wavelength of light passing through the core layer, The core layer, the cladding layer, and the light shielding layer are integrally formed by co-extrusion molding.

Images