Light guide and method for manufacturing the light guide

Abstract

To provide a light guide which has transparency when not lit, does not impair the aesthetic appearance of an area where it is attached, and can emit light approximately uniformly when lit. [Solution] The present invention is a light guide M having a core 1 for guiding light and a cladding 2 that surrounds the core 1 and radiates light to the outside, in which the core 1 is made of an acrylic resin and the cladding 2 is a light guide M in which hollow particles are uniformly dispersed in a polymer of a trifunctional monomer that serves as a base material, and the polymer of the trifunctional monomer and the hollow particles are composed of the same mass %.

Description

[Technical field]

[0001] The present invention relates to a light guide that emits light all around. [Background technology]

[0002] Conventionally, light guides that are formed in a round rod shape and emit light from their outer surface have a two-layer structure having a core layer for guiding light emitted from a light source and a cladding layer that is provided to cover the outer surface of the core layer and protects the core layer while outputting the light that enters the core layer to the outside.

[0003] The cladding layer is made of a compound containing fluorine to diffuse the light incident from the core layer. The compound containing fluorine is formed around the core layer by melting a resin formed in a pellet shape, and the light guide is formed in a state where the compound shrinks during the cooling process after melting and adheres closely to the core layer. The compound containing fluorine exists in the form of fine particles, and therefore has the property of scattering light, allowing the light guide to emit light evenly and without unevenness.

[0004] For example, Patent Document 1 describes a light guide in which the core layer is made of an acrylic resin and the clad layer is made of a fluororesin. With the clad layer made of a fluororesin, the light transmitted from the core layer to the clad layer is diffused by the clad layer, allowing the entire light guide to emit light uniformly. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-112616 A Summary of the Invention [Problem to be solved by the invention]

[0006] In this way, the light guide described in Patent Document 1 has a cladding layer from which light is emitted that is formed of a compound containing fluorine, so that the light passing through the cladding layer is easily reflected or scattered, and can be uniformly emitted from the outer circumferential surface of the light guide. However, when a compound containing fluorine is used for the cladding layer, the light incident from the outside of the light guide is scattered by the cladding layer when the light guide is not emitting light due to the light scattering effect of this compound, and as a result, it appears cloudy. In other words, when a compound containing fluorine is used for the cladding layer, there is a risk that the clouding of the light guide will impair the aesthetic appearance of the part to which the light guide is attached.

[0007] In recent years, it has been pointed out that fluorine-containing compounds such as perfluorooctanoic acid (PFAS) may affect health, and many countries have begun to restrict the use of these compounds. Many light guides contain perfluorooctanoic acid (PFAS) in the cladding layer to ensure uniform light emission, and if the use of perfluorooctanoic acid (PFAS) were banned, it would be difficult to provide a light guide that emits light uniformly.

[0008] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a light guide that is capable of uniform light emission when lit, is transparent when not lit, and does not risk compromising the aesthetic appearance of the area in which it is attached. [Means for solving the problem]

[0009] A first aspect of the present invention is a light guide having a core and a cladding surrounding the core, the cladding being composed of a polymer of a trifunctional monomer and hollow particles.

[0010] In another aspect of the present invention, the hollow particles are silica particles having an air layer therein and are formed to have a constant particle size.

[0011] In another aspect of the present invention, the hollow particles are silica particles having an air layer therein, and are formed by mixing particles of different diameters.

[0012] In another aspect of the present invention, the clad is characterized in that the hollow particles and the polymer of the trifunctional monomer are composed of approximately the same mass %.

[0013] In another aspect of the present invention, the particle diameter of the hollow particles is within the range of 50 nm to 100 nm.

[0014] In another aspect of the present invention, the core is formed mainly from an acrylic resin. Effect of the Invention

[0015] According to a first aspect of the present invention, there is provided a light guide having a core and a cladding surrounding the core, wherein the cladding is composed of a polymer of a trifunctional monomer and hollow particles, and therefore has transparency when not lit and does not impair the aesthetic appearance of the area in which it is attached, and can emit light uniformly when lit.

[0016] According to another aspect of the present invention, the hollow particles are silica particles having an air layer inside and are formed with a constant particle diameter, so that they have high transparency when not lit and there is no risk of them impairing the aesthetic appearance of the area in which they are attached.

[0017] According to another aspect of the present invention, the hollow particles are silica particles having an air layer inside, and different particle sizes are mixed to form the cladding. By improving the light scattering effect, refraction and reflection are more likely to occur within the cladding, thereby improving the uniformity of the light emitted from the light guide.

[0018] According to another aspect of the present invention, the cladding is composed of the hollow particles and the trifunctional monomer in approximately the same mass percentages, so that the hollow particles can be uniformly dispersed within the cladding, and the light radiated to the outside from the light guide can be made uniform.

[0019] According to another aspect of the present invention, the particle diameter of the hollow particles is within the range of 50 nm or more and 100 nm or less, so that the refractive index of the entire cladding can be kept constant, the amount of light leaking from the core to the cladding can be made constant, and the outer peripheral surface of the light guide can be made to emit light uniformly.

[0020] According to another aspect of the present invention, the core is formed mainly from an acrylic resin, so that transparency when the lamp is not lit can be improved, and the aesthetic appearance of the part in which the lamp is attached can be improved. [Brief description of the drawings]

[0021] [Figure 1] 1 is a perspective view showing an entire light guide according to an embodiment of the present invention; [Diagram 2] 2 is a cross-sectional view taken along line AA in FIG. 1. [Diagram 3] FIG. 2 is a cross-sectional view taken along line BB in FIG. [Figure 4] 4 is a schematic diagram showing an enlarged view of line C in FIG. 3. FIG. [Diagram 5] 3A to 3C are schematic diagrams illustrating a manufacturing procedure for a light guide according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The present invention provides a light guide consisting of a core and a clad, which has transparency when not lit and improves the aesthetic appearance when worn, and can emit light uniformly over the entire outer circumferential surface of the clad when lit, by devising the configuration of the clad. Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, the extension direction of the light guide shown in FIG. 1 is the front-rear direction, and the direction perpendicular to the extension direction of the light guide is the left-right direction.

[0023] FIG. 1 is a perspective view showing the configuration of a light guide M according to one embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB in FIG. 1. FIG. 4 is an enlarged view of a portion of FIG. 3, and is a schematic diagram showing the internal configuration of the cladding, and is illustrated without hatching showing a cross section in order to show the internal configuration. FIG. 5 is a schematic diagram showing the procedure for forming a light guide M according to one embodiment of the present invention, and is formed in the order of thick black arrows from top to bottom. Note that the hollow particles 20 shown in FIG. 4 and FIG. 5 are not as large as the particle diameter shown in the drawings due to the relationship with other members, but are illustrated for understanding the invention.

[0024] As shown in FIG. 1, the light guide M has a core 1 to which light from a light source is incident, and a cladding 2 that surrounds the core 1 and forms a light emitting layer of the light guide M.

[0025] The core 1 is formed in a solid cylindrical shape and has flexibility. The core 1 is mainly composed of an acrylic resin. Examples of the acrylic resin constituting the core 1 include acrylic block copolymers obtained by mixing acrylate (e.g., butyl acrylate or 2-ethylhexyl acrylate) with polymethyl methacrylate (PMMA) or methyl methacrylate (MAM). The core 1 may be composed of any resin as long as it has high transparency, can transmit light incident from a light source, and has appropriate flexibility. A light source is connected to one end of the core 1, and light is incident from one end to the other end, i.e., in the direction along the longitudinal direction of the core 1.

[0026] The clad 2 is provided in close contact with the outer peripheral surface of the core 1 as shown in FIG. 2 and FIG. 3. The clad 2 is formed to have a substantially uniform thickness along the extension direction of the core 1, with the radial direction of the core 1 being the thickness direction. The clad 2 is composed of hollow particles 20 and a polymer of a trifunctional monomer 21 as shown in FIG. 4. The hollow particles 20 are composed of particles having a hollow portion with a particle diameter of 50 to 100 nm. The refractive index nd of the clad 2 is reduced by mixing the hollow particles 20 with the trifunctional monomer 21. In this embodiment, the hollow particles 20 and the polymer of the trifunctional monomer 21 are composed of the same mass %. That is, the clad 2 is composed of the hollow particles 20 and the trifunctional monomer 21 in a 1:1 ratio. In FIG. 4, the wavy line W indicates the boundary between the core 1 and the clad 2.

[0027] Moreover, the cladding 2 is set to have a lower refractive index of light than the core 1. In this embodiment, the refractive index ne of the core 1 is set to 1.49, and the refractive index nd of the cladding 2 is set to 1.38. However, the refractive index nd of the cladding 2 and the refractive index ne of the core 1 are not limited to these values, and are not limited to the above-mentioned refractive indices as long as the refractive index ne of the core 1 is set to be higher than the refractive index nd of the cladding 2.

[0028] The clad 2 is made of a resin containing hollow particles 20 having a hollow portion. The clad 2 has a hollow portion, which reduces the refractive index nd and has high transparency. The principle by which the refractive index is reduced by having a hollow portion is that the hollow portion has an air layer with a low refractive index, and the refractive index nd of the clad 2 can be changed by changing the amount of hollow portions contained in the resin. In other words, since the thickness of the shell film surrounding the hollow portion of the hollow particle 20 is formed to be approximately constant, the volume of the hollow portion changes by changing the particle diameter, and the refractive index nd of the clad 2 can be changed. In other words, the refractive index nd of the clad 2 can be reduced by enlarging the particle diameter of the hollow particle 20.

[0029] The hollow particles 20 constituting the clad 2 are composed of hollow silica having a hollow portion. The hollow particles 20 have a particle diameter formed within a range of 50 to 100 nm, and the hollow particles 20 throughout the clad 2 are composed of approximately the same particle diameter. By having the hollow particles 20 constituting the clad 2 be composed of approximately the same particle diameter in this manner, scattering of the light passing through the clad 2 is reduced, and the linearity of the light passing through the clad 2 is improved, thereby achieving high transparency of the light guide M.

[0030] Furthermore, the hollow particles 20 constituting the clad 2 may be a mixture of particles having any particle diameter within the range of 50 to 100 nm. When hollow particles 20 having different particle diameters are mixed in the clad 2, a difference in the local refractive index occurs in the clad 2 due to the difference in particle diameter of the hollow particles 20, and the scattering effect in the clad 2 can be improved. In other words, the uniformity of the light emitted from the light guide can be improved by scattering the light passing through the clad 2.

[0031] In addition, the hollow particles 20 are preferably uniformly dispersed in the base resin (trifunctional monomer 21) in the clad 2, and are preferably dispersed in the form of primary particles without forming aggregated secondary particles (granules). The means for uniformly dispersing the hollow particles 20 in the polymer of the base trifunctional monomer 21 will be described later.

[0032] As described above, the light guide M has a core 1 made of an acrylic resin and a clad 2 containing hollow particles 20 uniformly dispersed in a base resin (a polymer of a trifunctional monomer 21). By surrounding the entire core 1 in a tightly adhered manner with the clad 2, light incident from the side end face of the core 1 can be uniformly radiated to the outside from the outer surface of the clad 2 via the clad 2.

[0033] Furthermore, by making the refractive index nd of the cladding 2 smaller than the refractive index ne of the core 1, the critical angle at the interface between the core 1 and the cladding 2 is reduced, and the amount of light entering the cladding 2 from the core 1 is controlled, making it possible to make the entire light guide M illuminate approximately uniformly.

[0034] Furthermore, the light guide M is configured such that the polymer of the trifunctional monomer 21 forming the resin body serving as the base material for the cladding 2 and the hollow particles 20 are formed at substantially the same mass %, so that the hollow particles 20 can be substantially uniformly dispersed in the polymer of the trifunctional monomer 21. This allows the entire light guide M to emit light substantially uniformly.

[0035] In addition, since the hollow particles 20 are uniformly dispersed in the polymer of the trifunctional monomer 21, when the light is not lit, the cladding 2 can have high transparency due to the hollow portions of the hollow particles 20. Furthermore, since the hollow particles 20 are made of hollow nanosilica having a particle diameter of 50 to 100 nm and having hollow portions, the transparency can be further improved.

[0036] In addition, since the resin body constituting the clad 2 is formed of a polymer of the trifunctional monomer 21, it has a high cross-link density and has a large number of cross-linking points per unit volume, and therefore has a high elastic modulus and can transform the light guide M to match the shape of the installation location. In addition, since the trifunctional monomer 21 constituting the clad 2 has a low shrinkage rate in the process of forming a polymer, the hollow particles 20 are less likely to become biased within the polymer of the trifunctional monomer 21, and the high transparency of the clad 2 can be maintained. In other words, the configuration in which the clad 2 is formed of hollow particles 20 having hollow portions and a polymer of the trifunctional monomer 21 makes it possible to provide a light guide M that does not impair the aesthetic appearance when installed and can emit light uniformly when turned on.

[0037] <Light guide manufacturing method> The light guide M is configured as described above, and is manufactured by the following procedure. The manufacturing procedure of this light guide M will be described with reference to FIG. 5. The light guide M can form a clad 2 with a uniform thickness on the outer peripheral surface of the core 1 by dipping the core 1 in a coating agent (hereinafter referred to as fluid 23) that forms a clad 2, and curing it with ultraviolet light. The details of this dipping will be described below.

[0038] First, hollow particles 20 and trifunctional monomers 21 for forming the clad 2 are melted in a solvent 22 to form a fluid 23 for dipping the core 1. The formed fluid 23 is contained in a vertically long container C. The fluid 23 is formed by mixing 45 mass % of trifunctional monomers 21, 45 mass % of hollow particles 20, and 10 mass % of solvent 22 for mixing them. Note that the mixing ratio of hollow particles 20, trifunctional monomers 21, and solvent 22 constituting the fluid 23 is not limited to the above ratio and can be set arbitrarily as long as the solvent 22 is constituted in the range of 5 to 20 mass % and the hollow particles 20 and trifunctional monomers 21 are constituted in the same mixing ratio.

[0039] Here, the trifunctional monomer 21 constituting the fluid 23 is composed of trimethylolpropane triacrylate (TMPTA), ethoxylated trimethylolpropane triacrylate (TNPEOTA), tris(2-acryloxyethyl)isocyanurate, ethoxylated glycerin triacrylate, etc. The trifunctional monomer 21 is not limited to the above-mentioned ones, and may be composed of any one that has high viscosity and hardens when irradiated with UV light.

[0040] The solvent 22 constituting the fluid 23 is composed of methyl isobutyl ketone (MIBK). The solvent 22 is not limited to methyl isobutyl ketone (MIBK), and may be composed of acetone, isopropyl alcohol (IPA), or the like having similar properties. In other words, the solvent 22 may be composed of any material as long as it has the properties of imparting an appropriate viscosity to the fluid 23 to be applied to the outer peripheral surface of the core 1, dispersing the trifunctional monomer 21 and the hollow particles 20 uniformly in the solvent 22, and volatilizing and separating from the clad 2 after being applied to the core 1.

[0041] Then, the core 1 formed in a longitudinal round rod shape is immersed perpendicularly to the liquid surface F of the fluid 23 in the container C containing the fluid 23 configured in this manner.

[0042] Thereafter, the core 1 is pulled upward while being kept perpendicular to the liquid surface F of the fluid 23. At this time, the core 1 is pulled up at a speed of 0.5-2.0 cm / s. The pulling speed of the core 1 is varied according to the ratio of the solvent 22 constituting the fluid 23. That is, when the ratio of the solvent 22 constituting the fluid 23 is high, the viscosity of the fluid 23 decreases, so the pulling speed of the core 1 is increased so that the fluid 23 applied around the core 1 has a predetermined film thickness. Also, when the ratio of the solvent 22 constituting the fluid 23 is low, the viscosity of the fluid 23 increases, so the pulling speed of the core 1 is decreased so that the fluid 23 applied around the core 1 has a predetermined film thickness. That is, when the ratio of the solvent 22 constituting the fluid 23 is high (20 mass%), the pulling speed of the core 1 pulled up from the fluid 23 is set to 2 cm / s, and when the ratio of the solvent 22 is low (5 mass%), the pulling speed of the core 1 pulled up from the fluid 23 is set to 0.5 m / s.

[0043] Then, the core 1 coated with the fluid 23 is pulled up from the liquid surface F of the fluid 23, and at the same time, ultraviolet light L (e.g., ultraviolet light with a wavelength of 365 nm) is irradiated to form a clad 2 on the outer peripheral surface of the core 1. When the clad 2 is formed on the outer peripheral surface of the core 1, the solvent 22 volatilizes from the fluid 23, and the trifunctional monomer 21 shrinks due to a photopolymerization reaction, so that the clad 2 is formed in close contact with the outer peripheral surface of the core 1.

[0044] That is, the boundary between the core 1 and the clad 2 is in close contact, and no air layer is formed between the core 1 and the clad 2. Therefore, the refractive index of the light incident on the clad 2 from the core 1 can be changed approximately uniformly at the boundary between the core 1 and the clad 2, and the light emitted from the light guide M is also emitted approximately uniformly. In other words, the entire light guide M can emit light uniformly.

[0045] Then, by cutting off the portions of the outer peripheral surface of the core 1 where the cladding 2 is not formed or is not formed uniformly, specifically, the portion that holds the core 1 when the fluid 23 is dipped into the core 1, and the lower end of the core 1 where the fluid 23 is likely to flow down and become thick during dipping, a light guide M is completed in which the cladding 2 is coated around the core 1 with a uniform thickness and in a tightly adhered manner.

[0046] The light guide M is formed by the above-mentioned procedure, and is formed in such a manner that the clad 2 is in close contact with the outer peripheral surface of the core 1 and with a uniform film thickness due to the viscosity of the solvent 22 forming the fluid 23, the pulling speed of the core 1 during dipping, and the photopolymerization reaction of the trifunctional monomer 21. As a result, the light guide M consisting of the core 1 and the clad 2 has an elastic effect due to being formed by the photopolymerization of the trifunctional monomer 21, and hollow nanosilica with a particle diameter of 50-100 nm is uniformly dispersed in the clad 2 as hollow particles 20, ensuring the transparency of the clad 2, while the light guide M can emit light uniformly by utilizing the scattering effect of the hollow nanosilica.

[0047] In the drawings for explaining this embodiment, the hollow particles 20 are illustrated so as to be visible, but since the hollow particles 20 are formed with a very small particle diameter of 50 to 100 nm, they cannot actually be seen. The hollow particles 20 illustrated in Figs. 4 and 5 are merely shown diagrammatically so that the configuration of the clad 2 can be understood.

[0048] The present invention is not limited to the above-described embodiment, but includes configurations in which the configurations disclosed in the above-described embodiment are mutually substituted or the combinations are changed, known inventions, and configurations in which the configurations disclosed in the above-described embodiment are mutually substituted, etc. In addition, the technical scope of the present invention is not limited to the above-described embodiment, but extends to the matters described in the claims and their equivalents. [Explanation of symbols]

[0049] M Light Guide 1 core 2. Clad 20 hollow particles 21 Trifunctional Monomers 22 Solvent 23 Fluid ne,nd refractive index

Claims

1. A core, a cladding surrounding the core; A light guide having The cladding is The polymer is made of a trifunctional monomer and hollow particles. A light guide comprising said hollow particles and said polymer of said trifunctional monomer each occupying approximately half the mass % of the entire cladding.

2. 2. The light guide according to claim 1, wherein the hollow particles are silica particles having an air layer therein, and are formed with a constant particle diameter.

3. 2. The light guide according to claim 1, wherein the hollow particles are silica particles having an air layer therein, and are formed by mixing particles of different diameters.

4. 4. The light guide according to claim 3, wherein the particle diameter of the hollow particles is within a range of 50 nm to 100 nm.

5. The light guide according to claim 4 , wherein the core is formed mainly from an acrylic resin.

6. A method for manufacturing a light guide having a core and a cladding surrounding the core, the cladding being composed of a polymer of a trifunctional monomer and hollow particles, comprising: a first step of mixing the trifunctional monomer and the hollow particles in approximately the same mass percentage and stirring the mixture in a solvent to form a fluid; a second step of immersing the core vertically with respect to a liquid level of the fluid in a container containing the fluid formed in the first step; a third step of withdrawing the core immersed in the fluid at a constant speed while maintaining the core vertically; a fourth step of irradiating the fluid formed around the core pulled out of the fluid in the third step with ultraviolet light to volatilize the solvent from the fluid while polymerizing the trifunctional monomer; A method for manufacturing a light guide, comprising the steps of:

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