Light guide, and method for manufacturing a light guide

Abstract

This light guide is transparent when not illuminated, so as not to detract from the aesthetics of the area it is attached to, and when illuminated, it provides nearly uniform illumination. [Solution] The present invention relates to a light guide M having a core 1 for guiding light and a cladding 2 surrounding the core 1 and radiating light to the outside, wherein the core 1 is made of an acrylic resin and the cladding 2 is made of a polymer of a trifunctional monomer as a base material in which hollow particles are uniformly dispersed, and the polymer of the trifunctional monomer and the hollow particles are made in the same mass %.

Description

Technical Field

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

Background Art

[0002] Conventionally, a light guide formed in a round bar shape and emitting light from its outer peripheral surface has a two-layer structure having a core layer for guiding light emitted from a light source and a cladding layer provided so as to cover the outer peripheral surface of the core layer and outputting the light incident on the core layer to the outside while protecting the core layer.

[0003] And the cladding layer is formed of a fluorine-containing compound in order to diffuse the light incident from the core layer. Since the fluorine-containing compound is formed by melting a resin formed in a pellet shape around the core layer, the light guide is formed in a state of adhering to the core layer by shrinking in the cooling process after melting. And since the fluorine-containing compound exists in a fine particle state, it has the property of scattering light and can emit light uniformly without unevenness in the light guide.

[0004] For example, Patent Document 1 describes a light guide in which the core layer is formed of an acrylic resin and the cladding layer is formed of a fluorine resin. With such a configuration in which the cladding layer is formed of a fluorine resin, the light transmitted from the core layer to the cladding layer is diffused in the cladding layer, and the entire light guide can emit light uniformly.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Thus, the light guide described in Patent Document 1 has a cladding layer from which light is emitted made of a fluorine-containing compound. As a result, light passing through the cladding layer is easily reflected or scattered, and can be uniformly emitted from the outer surface of the light guide. However, when a fluorine-containing compound is used in the cladding layer, the light scattering effect of this compound causes light incident from outside the light guide to be scattered by the cladding layer when the light guide is not emitting light, resulting in a cloudy appearance. In other words, using a fluorine-containing compound in the cladding layer could impair the aesthetic appearance of the area where the light guide is attached due to the clouding of the light guide.

[0007] Furthermore, in recent years, it has been pointed out that perfluorinated compounds (PFAS), among fluorine-containing compounds, may have adverse health effects, and as a result, many countries have begun to regulate the use of these PFAS. In many light guides, perfluorinated compounds (PFAS) are contained in the cladding layer to ensure uniform and even illumination. If the use of perfluorinated compounds (PFAS) is prohibited, it will be difficult to provide light guides that emit uniform and even illumination.

[0008] This invention has been made in view of the above-mentioned problems, and aims to provide a light guide that enables uniform illumination when lit, is transparent when not lit, and does not impair the aesthetic appearance of the part to 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, wherein the cladding is composed of a polymer of a trifunctional monomer and hollow particles.

[0010] Another aspect of the present invention is characterized in that the hollow particles are silica particles having an air layer inside, and are formed with a constant particle size.

[0011] Another aspect of the present invention is characterized in that the hollow particles are silica particles having an air layer inside, and are formed by mixing particles of different sizes.

[0012] Another aspect of the present invention is characterized in that the cladding is composed of the hollow particles and the polymer of the trifunctional monomer in substantially the same mass percentage.

[0013] Another aspect of the present invention is characterized in that the particle diameter of the hollow particles is in the range of 50 nm to 100 nm.

[0014] Another aspect of the present invention is characterized in that the core is formed mainly of an acrylic resin. [Effects of the Invention]

[0015] According to a first aspect of the present invention, 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, so that when not lit, it is transparent and does not impair the aesthetic appearance of the part to which it is attached, and when lit, it can emit light uniformly.

[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 size, so they have high transparency when not lit and do not impair the aesthetic appearance of the part to 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 by mixing particles of different sizes to form a cladding, the scattering of light is improved, making it easier for refraction and reflection 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, since the clad is composed of the hollow particles and the trifunctional monomer in substantially the same mass percentage, the hollow particles can be uniformly dispersed in the clad, and the light radiated from the light guide to the outside can be made uniform.

[0019] According to another aspect of the present invention, since the particle diameter of the hollow particles is in the range of 50 nm or more and 100 nm or less, the refractive index of the entire clad can be kept constant, the amount of light leaking from the core to the clad 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, since the core is formed mainly of an acrylic resin, the transparency when not lit can be improved, and the aesthetics of the mounted part can be improved.

Brief Description of the Drawings

[0021] [Figure 1] It is a perspective view showing the whole light guide according to an embodiment of the present invention. [Figure 2] It is a cross-sectional view taken along line A-A of FIG. 1. [Figure 3] It is a cross-sectional view taken along line B-B of FIG. 1. [Figure 4] It is a schematic view showing an enlarged state of line C in FIG. 3. [Figure 5] It is a schematic view showing the manufacturing procedure of the light guide according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0022] The present invention provides a light guide composed of a core and a clad. By devising the configuration of the clad, the light guide has transparency when not lit and improves the aesthetics when mounted, and when emitting light, the entire outer peripheral surface of the clad can emit light uniformly. Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, the extending direction of the light guide shown in FIG. 1 is defined as the front-rear direction, and the direction orthogonal to the extending direction of the light guide is defined as the left-right direction.

[0023] Figure 1 is a perspective view showing the configuration of a light guide M according to one embodiment of the present invention. Figure 2 is a cross-sectional view along line AA in Figure 1, and Figure 3 is a cross-sectional view along line BB in Figure 1. Figure 4 is an enlarged view of a part of Figure 3, and is a schematic diagram showing the internal configuration of the cladding. In order to show the internal configuration, the hatching indicating the cross-section is omitted. Figure 5 is a schematic diagram showing the procedure for forming the light guide M according to one embodiment of the present invention, and is formed in the order of the thick black arrows from top to bottom. Note that the hollow particles 20 shown in Figures 4 and 5 do not have a particle size large enough to be shown due to their relationship with other components, but are shown for the purpose of understanding the invention.

[0024] As shown in Figure 1, the light guide M has a core 1 into which light from a light source is incident, and a cladding 2 surrounding the core 1 to form the light-emitting layer of the light guide M.

[0025] Core 1 is formed in a solid cylindrical shape and is flexible. Core 1 is mainly composed of an acrylic resin. Examples of acrylic resins that make up Core 1 include acrylic block copolymers obtained by mixing polymethyl methacrylate (PMMA) or methyl methacrylate (MAM) with acrylate (e.g., butyl acrylate or 2-ethylhexyl acrylate). 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 Core 1, and light is incident from one end to the other, that is, in a direction along the longitudinal direction of Core 1.

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

[0027] Furthermore, the cladding 2 is set to have a lower refractive index compared to the core 1. In this embodiment, the refractive index ne of the core 1 is 1.49, and the refractive index nd of the cladding 2 is 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; as long as the refractive index ne of the core 1 is set higher than the refractive index nd of the cladding 2, the refractive index is not limited to the above values.

[0028] Clad 2 is composed of a resin containing hollow particles 20 having a hollow portion. Due to its hollow structure, Clad 2 has a reduced refractive index nd and high transparency. The principle that 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 Clad 2 can be changed by changing the amount of hollow portion contained in the resin. In other words, since the thickness of the shell membrane surrounding the hollow portion of the hollow particle 20 is formed to be approximately constant, changing the particle size changes the volume of the hollow portion, and thus the refractive index nd of Clad 2 can be changed. To put it another way, the refractive index nd of Clad 2 can be reduced by increasing the particle size of the hollow particle 20.

[0029] The hollow particles 20 constituting cladding 2 are made of hollow silica having a hollow portion. The hollow particles 20 have a particle diameter formed in the range of 50 to 100 nm, and the hollow particles 20 throughout cladding 2 are composed of approximately the same particle diameter. By having the hollow particles 20 constituting cladding 2 be composed of approximately the same particle diameter in this way, the scattering of light passing through cladding 2 is reduced, the straightness of the light passing through cladding 2 is improved, and high transparency of the light guide M can be achieved.

[0030] Furthermore, the hollow particles 20 constituting the cladding 2 can be a mixture of particles with any particle size within the range of 50 to 100 nm. When hollow particles 20 with different particle sizes are mixed within the cladding 2, local differences in refractive index occur within the cladding 2 due to the differences in particle sizes of the hollow particles 20, thereby improving the scattering effect within the cladding 2. In other words, the scattering of light passing through the cladding 2 improves the uniformity of the light emitted from the light guide.

[0031] Furthermore, it is preferable that the hollow particles 20 are uniformly dispersed within the cladding 2 in the base resin (trifunctional monomer 21), and that they are dispersed in a primary particle state 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 acrylic resin and a cladding 2 containing hollow particles 20 uniformly dispersed in a base resin (a polymer of trifunctional monomer 21). The cladding 2 tightly surrounds the entire core 1, allowing light incident from the side end face of the core 1 to be uniformly radiated outwards from the outer surface of the cladding 2 through the cladding 2.

[0033] Furthermore, by making the refractive index nd of cladding 2 smaller than the refractive index ne of core 1, the critical angle at the interface between core 1 and cladding 2 is reduced, thereby controlling the amount of light entering cladding 2 from core 1 and allowing the entire light guide M to be illuminated almost uniformly.

[0034] Furthermore, the light guide M is constructed by forming a polymer of the trifunctional monomer 21 that forms the base resin material of the cladding 2 and hollow particles 20 in approximately the same mass percentage. This allows the hollow particles 20 to be dispersed almost uniformly within the polymer of the trifunctional monomer 21. As a result, the entire light guide M can emit light almost uniformly.

[0035] Furthermore, since the hollow particles 20 are uniformly dispersed in the polymer of the trifunctional monomer 21, the cladding 2 can have high transparency when not lit due to the hollow portions of the hollow particles 20. In addition, by forming the hollow particles 20 with a particle size of 50 to 100 nm using hollow nanosilica with hollow portions, transparency can be further enhanced.

[0036] Furthermore, since the resin body constituting the cladding 2 is formed from a polymer of trifunctional monomers 21, it has a high crosslinking density and a large number of crosslinking points per unit volume, resulting in a high elastic modulus that allows the light guide M to transform to suit the shape of the installation site. In addition, because the trifunctional monomers 21 constituting the cladding 2 have a low shrinkage rate during the polymer formation process, uneven distribution of hollow particles 20 within the polymer of trifunctional monomers 21 is less likely to occur, and the high transparency of the cladding 2 can be maintained. In other words, by forming the cladding 2 with a polymer of hollow particles 20 having hollow parts and trifunctional monomers 21, it is possible to provide a light guide M that does not impair aesthetics when installed and emits light uniformly when lit.

[0037] ≪Manufacturing Method for Light Guides≫ As described above, the light guide M is constructed and manufactured by the following procedure. The manufacturing procedure for this light guide M will be explained with reference to Figure 5. The light guide M is manufactured by dipping the core 1 into a coating agent that forms the cladding 2 (hereinafter referred to as fluid 23) and curing it with ultraviolet light, thereby forming cladding 2 with a uniform film thickness on the outer surface of the core 1. The details of this dipping will be explained below.

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

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

[0040] Furthermore, the solvent 22 constituting the fluid 23 is composed of methyl isobutyl ketone (MIBK). However, the solvent 22 is not limited to methyl isobutyl ketone (MIBK), and may be composed of acetone, isopropyl alcohol (IPA), or other substances having similar properties. In other words, the solvent 22 can be composed of any substance that imparts appropriate viscosity to the fluid 23 applied to the outer surface of the core 1, allows the trifunctional monomer 21 and hollow particles 20 to be uniformly dispersed in the solvent 22, and has the property of volatilizing and detaching from the cladding 2 after being applied to the core 1.

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

[0042] Subsequently, the core 1 is pulled upward while maintaining a position 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 proportion of solvent 22 that constitutes the fluid 23. That is, if the proportion of solvent 22 that constitutes 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 reaches a predetermined film thickness. Conversely, if the proportion of solvent 22 that constitutes 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 reaches a predetermined film thickness. In other words, if the proportion of solvent 22 that constitutes the fluid 23 is high (20 mass%), the pulling speed of the core 1 pulled from the fluid 23 is set to 2 cm / s, and if the proportion of solvent 22 is low (5 mass%), the pulling speed of the core 1 pulled from the fluid 23 is set to 0.5 m / s.

[0043] Then, as the core 1 coated with fluid 23 is lifted from the liquid surface F of the fluid 23, ultraviolet light L (for example, ultraviolet light with a wavelength of 365 nm) is irradiated onto the outer surface of the core 1, forming a cladding 2. When the cladding 2 is formed on the outer surface of the core 1, the solvent 22 evaporates from the fluid 23, and the trifunctional monomer 21 shrinks due to a photopolymerization reaction, so that the cladding 2 is formed in close contact with the outer surface of the core 1.

[0044] In other words, the boundary between core 1 and cladding 2 is tightly sealed, and no layer of air or other material forms between core 1 and cladding 2. Therefore, the refractive index of light incident from core 1 to cladding 2 can be changed almost uniformly at the boundary between core 1 and cladding 2, and the light emitted from light guide M is also emitted almost uniformly. In other words, the entire light guide M can emit light uniformly.

[0045] Then, by cutting off the parts of the outer surface of the core 1 where cladding 2 is not formed or is not formed uniformly, specifically the part that grips the core 1 when dipping the fluid 23 into the core 1, and the lower end of the core 1 where the fluid 23 tends to flow down and form a thicker film during dipping, a light guide M is completed in which cladding 2 is coated around the core 1 with a uniform thickness and in a tightly adhering manner.

[0046] The light guide M is formed by the procedure described above, and is formed in such a manner that the cladding 2 adheres closely to the outer surface of the core 1 and has a uniform film thickness, due to the viscosity of the solvent 22 that forms 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 cladding 2, has elastic properties because it is formed from the photopolymer of the trifunctional monomer 21, and hollow nanosilica with a particle size of 50-100 nm is uniformly dispersed in the cladding 2 as hollow particles 20, ensuring the transparency of the cladding 2, while the light guide M can emit light uniformly by utilizing the scattering effect of the hollow nanosilica.

[0047] In the diagrams illustrating this embodiment, the hollow particles 20 are shown to be visible, but since the hollow particles 20 are formed with a very small particle size of 50-100 nm, they cannot actually be seen. The hollow particles 20 shown in Figures 4 and 5 are merely schematic representations to illustrate the structure of the cladding 2.

[0048] Furthermore, the present invention is not limited to the embodiments described above, but also includes configurations in which the components disclosed in the embodiments described above are substituted for each other or their combinations are changed, known inventions and configurations in which the components disclosed in the embodiments described above are substituted for each other, and so on. In addition, the technical scope of the present invention is not limited to the embodiments described above, 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 3 Functional Monomers 22 Solvents 23 Fluid ne,nd refractive index

Claims

1. The core and A cladding surrounding the aforementioned core, A light guide having, The cladding is composed of a polymer of trifunctional monomers and hollow particles. Light guide.

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

3. The light guide according to claim 1, characterized in that the hollow particles are silica particles having an air layer inside, and are formed by mixing particles of different sizes.

4. The light guide according to any one of claims 1 to 3, characterized in that the cladding is composed of the hollow particles and the polymer of the trifunctional monomer in substantially the same mass percentage.

5. The light guide according to claim 4, characterized in that the particle diameter of the hollow particles is in the range of 50 nm to 100 nm.

6. The light guide according to claim 5, characterized in that the core is formed mainly of an acrylic resin.

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