Method for producing retroreflective stereo molded body

Abstract

To provide a method for producing a retroreflective stereo molded body having extensibility, easy to follow a stereo shape and easy to hold a stereo shape.SOLUTION: A method for producing a retroreflective stereo molded body comprises: a step of preparing a retroreflective material having a retroreflective region 2 with an adhesive layer 21, transparent microbeads 23 embedded in the adhesive layer 21, and a reflective layer 22 provided between the adhesive layer 21 and the transparent microbeads 23, and a non-retroreflective region 3 without the adhesive layer 21, transparent microbeads 23, and reflective layer 22; a step of preparing a support 1 made of a stretchable knitted fabric produced from core-sheath type multifilament yarns, in which the core component is polyethylene terephthalate and the sheath component is a low-melting-point polyester copolymer; a step of laminating the support 1 on the adhesive layer 21 side of the retroreflective material to obtain a laminate; and a step of providing heat to the laminate to soften or melt the sheath component, thereby fusing the core-sheath type multifilament yarns together and molding the laminate into a three-dimensional shape.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a three-dimensional retroreflective molded article, and more particularly to a method for molding a retroreflective material into a three-dimensional object without impairing the retroreflective function. [Background technology]

[0002] Retroreflective materials have been widely used for indicating traffic signs, etc. Furthermore, from the perspective of ensuring the safety of people working at night, it is common for police, fire departments, civil engineering and construction workers, etc. to wear retroreflective materials in the form of sashes or armbands. All of these retroreflective materials are supplied in flat shapes.

[0003] A planar retroreflective material comprises an adhesive resin layer made of a synthetic resin such as polyethylene terephthalate, transparent microspheres embedded in the adhesive resin layer, and a reflective layer disposed between the transparent microspheres and the adhesive resin layer. The support for this retroreflective material is made of a polyester-cotton taffeta fabric laminated and bonded to the adhesive resin layer (see Patent Document 1, Example 1). Therefore, when attempting to mold this into a three-dimensional shape, the adhesive resin layer is destroyed, resulting in reduced retroreflectivity, particularly in curved sections. Furthermore, because the support is made of taffeta fabric, it is difficult to conform to a three-dimensional shape, making it difficult to maintain the three-dimensional shape, and the support is prone to tearing and wrinkling.

[0004] On the other hand, Patent Document 2 proposes a retroreflective material that has retroreflective areas and non-retroreflective areas. The presence of the non-retroreflective areas in this retroreflective material gives the material flexibility and flexibility.

[0005] [Patent Document 1] Patent No. 5612790 [Patent Document 2] Patent No. 6630338 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0006] The object of the present invention is to provide a method for producing a three-dimensional retroreflective molded body by imparting extensibility to the retroreflective material described in Patent Document 2, which can easily conform to a three-dimensional shape and easily maintain the three-dimensional shape. [Means for solving the problem]

[0007] The present invention solves the above-mentioned problems by employing a specific support. Specifically, the present invention relates to a method for producing a three-dimensional retroreflective body, comprising the steps of: preparing a retroreflective material having a retroreflective region with an adhesive layer, transparent microspheres embedded in the adhesive layer, and a reflective layer provided between the adhesive layer and the transparent microspheres; and a non-retroreflective region without the adhesive layer, the transparent microspheres, or the reflective layer; preparing a support made of an extensible knitted fabric knitted with sheath-core multifilament yarns having a core component made of a high-melting-point polyester polymer and a sheath component made of a low-melting-point polyester polymer, the core components of which are not fused together; laminating the support on the adhesive layer side of the retroreflective material to obtain a laminate; and applying heat to the laminate to soften or melt the sheath component, thereby fusing the core-sheath multifilament yarns together and molding the laminate into a three-dimensional shape.

[0008] The fixing layer 21 used in the retroreflective region 2 of the present invention may be a conventionally known material. Specifically, urethane-based resins, polyolefin-based resins (polyethylene, polypropylene, etc.), ethylene-vinyl acetate copolymer resins, polyvinyl alcohol, acrylic resins, urethane-based resins, ester-based resins, etc. may be used. Alternatively, the fixing layer 21 may be made of a pressure-sensitive adhesive, such as an acrylic pressure-sensitive adhesive. The resin forming the fixing layer 21 may be copolymerized with a silane coupling agent, if necessary. By copolymerizing the silane coupling agent in this manner, the fixing layer 21 can be endowed with durability, adhesiveness, etc. The resin forming the fixing layer 21 may also be crosslinked with a crosslinking agent, such as a polyisocyanate-based crosslinking agent, an epoxy-based crosslinking agent, or a melamine-based resin, if necessary. By crosslinking with a crosslinking agent in this manner, the fixing layer 21 can be endowed with heat resistance, washing resistance, etc. The fixing layer 21 may contain additives, such as dyes, pigments, phosphorescent pigments, or inorganic fillers, depending on the intended use and desired functions of the resulting three-dimensional retroreflective molded article. The thickness of the fixing layer 21 is, for example, about 15 to 300 μm, preferably about 20 to 200 μm, as long as the transparent microspheres 23 can be embedded and held therein.

[0009] The transparent microspheres 23 are laid out over the entire surface of the adhesive layer 21 without overlapping. The refractive index of the transparent microspheres 23 is approximately 1.6 to 2.5. By using transparent microspheres 23 with such a refractive index, light can be focused on the reflective layer 22, providing excellent retroreflective performance. From the viewpoint of providing even better retroreflective performance, the refractive index of the transparent microspheres 23 is preferably 1.8 to 2.2, and more preferably 1.9 to 2.1. The average particle size of the transparent microspheres 23 is preferably 30 to 200 μm, and preferably a fine average particle size of approximately 45 to 80 μm. Transparent microspheres 23 with a fine average particle size exhibit better retroreflective performance at curved portions of the resulting three-dimensional retroreflective molded body. The average particle size of the transparent microspheres 23 is determined by measuring the maximum diameter of 30 transparent microspheres 23 using a microscope at a magnification of 500x and calculating the average value.

[0010] The material of the transparent microspheres 23 is not particularly limited as long as it has the refractive index described above, and may be made of glass, resin, or the like. However, glass transparent microspheres 23 are excellent in transparency, chemical resistance, washing resistance, weather resistance, etc., and are therefore preferably used in the present invention. The number of transparent microspheres 23 embedded per unit area may be appropriately determined depending on the retroreflective performance to be provided. For example, 2 The number of transparent microspheres 23 may be about 50 to 500, preferably about 100 to 250.

[0011] The reflective layer 22 is disposed between the transparent microspheres 23 and the adhesive layer 21 and serves to retroreflect light incident from the transparent microspheres 23. While the material of the reflective layer 22 is not particularly limited, it is preferably a metal film. Specific examples of metals that can be used to form the metal film include aluminum, zinc oxide, titanium, zinc, silica, tin, nickel, and silver. Among these metals, aluminum is preferred for its superior retroreflective performance. While the thickness of the reflective layer 22 is not particularly limited, it is preferably approximately 100 to 2000 Å, and more preferably approximately 600 to 1500 Å. A transparent resin layer (not shown) may be disposed between the transparent microspheres 23 and the reflective layer 22. By providing the transparent resin layer, it is possible to adjust the reflective brightness and change the color tone of the emitted light. Furthermore, when the reflective layer 22 is a metal film, the transparent resin layer makes the reflective layer 22 less susceptible to corrosion. The retroreflective area 2 of the retroreflective material used in the present invention is composed of the transparent microspheres 23, the reflective layer 22, and the adhesive layer 21, as described above.

[0012] On the other hand, the non-retroreflective region 3 of the retroreflective material used in the present invention does not have transparent microspheres 23, a reflective layer 22, or an adhesive layer 21. The shapes of the non-retroreflective region 3 and the retroreflective region 2 are arbitrary. For example, the retroreflective region 2 may be a plurality of circles, triangles, or rectangles, with the remaining area being the non-retroreflective region 3. The non-retroreflective region 3 can be located anywhere on the retroreflective material, but is preferably provided so that it stretches in both the vertical and horizontal directions. Specifically, the non-retroreflective region 3 is preferably provided in the bias direction, as shown in Figures 2 and 3. When the non-retroreflective region 3 is provided in a linear shape, its width may be approximately 0.5 to 3 mm. It is also preferable to form the retroreflective region 2 in a polka dot pattern, as shown in Figure 4. In this case, the non-retroreflective region 3 is more likely to stretch in both directions. The diameter of each dot (bead) is preferably approximately 0.5 cm to 2.0 cm. In the case of an embodiment such as that shown in FIG. 2 or FIG. 3, the area ratio of the retroreflective region 2 to the non-retroreflective region 3 (area of ​​retroreflective region / area of ​​non-retroreflective region) is preferably approximately 80 / 20 to 90 / 10. In the case of an embodiment such as that shown in FIG. 4, the area ratio is preferably approximately 20 / 80 to 50 / 50. It is preferable to laminate a transparent synthetic resin film as a release substrate on the surface of the transparent microspheres 4 in the retroreflective region 2. The presence of such a release substrate allows the retroreflective material having the retroreflective region 2 and the non-retroreflective region 3 to be handled as a single unit in the form of a sheet or tape.

[0013] The support 1 laminated to the retroreflective material is made of an extensible knitted fabric. The extensible knitted fabric is preferably a weft knitted fabric, and particularly preferably a circular knitted fabric. A weft knitted fabric is made by connecting loops, which are stitches, in the weft direction, and is easily stretchable in both the weft and warp directions due to deformation of each loop, making it preferable for use in the present invention. An extensible knitted fabric can be obtained by knitting a core-sheath multifilament yarn on a knitting machine such as a weft knitting machine, such as a circular knitting machine.

[0014] The sheath-core multifilament yarn constituting the stretchable knitted fabric is formed by bundling multiple sheath-core filaments whose core component is made of a high-melting-point polymer and whose sheath component is made of a low-melting-point polymer. The difference in melting point between the high-melting-point polymer and the low-melting-point polymer is preferably 50°C or more. If the difference in melting point is less than 50°C, when the low-melting-point polymer is softened or melted, the high-melting-point polymer may also soften, making it difficult to maintain the original fiber shape. Specific examples of combinations of high-melting-point polymer and low-melting-point polymer include polyethylene terephthalate / low-melting-point polyester copolymer, polyethylene terephthalate / polypropylene, polyethylene terephthalate / polyethylene, nylon 6 / low-melting-point polyester copolymer, and polypropylene / polyethylene, with polyethylene terephthalate / low-melting-point polyester copolymer being particularly preferred. Any low-melting-point polyester copolymer can be used as long as it has a melting point lower than that of polyethylene terephthalate. Generally, it is preferable to use a copolymer containing ethylene glycol, terephthalic acid, 1,4-butanediol, and diethylene glycol, and optionally caprolactone, as the low-melting point polyester copolymer. In the sheath-core filament, the weight ratio of the core component to the sheath component is approximately 0.3 to 3:1 (weight ratio). If the weight ratio of the core component is too low, the mechanical strength of the resulting three-dimensional retroreflective molded body tends to decrease. If the weight ratio of the core component is too high, the degree of fusion between the sheath-core multifilament yarns decreases, and the shape retention of the resulting three-dimensional retroreflective molded body tends to decrease. The core component and sheath component are preferably arranged concentrically. If they are arranged eccentrically, shrinkage is more likely to occur when heat is applied, which tends to cause the resulting three-dimensional retroreflective molded body to shrink. In general, a core-sheath multifilament yarn has a filament fineness of about 3 to 15 decitex, and is formed by bundling about 20 to 70 of these filaments together, with a total fineness of about 100 to 500 decitex.

[0015] A support 1 is laminated on the fixing layer 21 side of the retroreflective material to obtain a laminate in which the retroreflective material and support 1 are bonded together. The retroreflective material and support 1 may be bonded together with an adhesive such as a hot melt adhesive. Alternatively, the sheath component of the core-sheath multifilament yarn that constitutes the stretchable knitted fabric that is the support 1 may be softened and used as an adhesive to bond them together. Furthermore, if the fixing layer 21 is adhesive, the retroreflective material and support 1 may be bonded together by applying pressure without using an adhesive.

[0016] This laminate is heated to form it into a predetermined three-dimensional shape. Specifically, the laminate is deformed into the predetermined three-dimensional shape and then heated. Alternatively, the laminate may be deformed into the predetermined three-dimensional shape after being heated. Furthermore, pressure may be applied in addition to heat. The heat applied to the laminate is a temperature at which the sheath components of the sheath-core multifilament yarns that make up the stretchable knitted fabric, which is the support 1, soften or melt. Specifically, when heated to a temperature of 170°C to 210°C, the sheath components soften or melt. As the sheath components soften or melt, they fuse together, causing the sheath-core multifilament yarns to fuse together, and then the laminate is cooled to obtain a three-dimensional retroreflective molded body that retains the predetermined three-dimensional shape.

[0017] The retroreflective three-dimensional molded articles obtained by the method of the present invention can be used for a variety of purposes, particularly as equipment for nighttime performances such as plays, concerts, and sports events. They can also be used as outdoor exteriors or three-dimensional structures (objects). They can also be used as indoor interior materials, decorations, lighting covers, etc. [Effects of the Invention]

[0018] The method for producing a three-dimensional retroreflective molded body according to the present invention uses a laminate formed by laminating a support body that is an extensible knit fabric to a retroreflective material having retroreflective regions and non-retroreflective regions. Therefore, the extensible knit fabric stretches in the non-retroreflective regions, allowing both the retroreflective material and the support body to conform well to the three-dimensional shape during three-dimensional molding. This results in less deterioration of retroreflectivity and less wrinkling in curved portions of the three-dimensional shape. Furthermore, because sheath-core multifilament yarns are used as the yarns constituting the extensible knitted fabric and these sheath-core multifilament yarns are fused together, the resulting three-dimensional retroreflective molded body also has the advantage of good shape retention.

[0019] Example 1 [Preparing retroreflective materials] A release substrate consisting of a 75 μm-thick polyester film laminated with a 40 μm-thick polyethylene film was heated at 200°C for 2 minutes to melt the polyethylene film. Transparent microspheres with an average particle size of 70 μm and a refractive index of 1.93 were spread over the molten polyethylene film without overlapping, and the polyethylene film was allowed to cool and solidify. Aluminum was then vapor-deposited onto the transparent microspheres by vacuum deposition to form a 700 Å-thick reflective layer. A 25 μm-thick polyurethane resin was applied to the reflective layer to form an adhesive layer. A hot-melt adhesive (polyester urethane resin) was then applied to the adhesive layer and dried to produce an intermediate with a retroreflective region covering the entire surface. The intermediate was cut with a plotter cutter from the adhesive resin layer side to the interface with the polyethylene film on the side where the transparent microspheres were embedded, and the adhesive resin layer, adhesive layer, reflective layer, and transparent microspheres were peeled off together in the region that formed the non-retroreflective region (line width approximately 1 mm) as shown in Figure 2, yielding a retroreflective material with both a retroreflective region and a non-retroreflective region.

[0020] [Preparation of support] The core component was polyethylene terephthalate, a copolymer of ethylene glycol and terephthalic acid (melting point 256°C, intrinsic viscosity [η] 0.75). The sheath component was a low-melting-point polyester copolymer containing terephthalic acid, ε-caprolactone, ethylene glycol, 1,4-butanediol, and diethylene glycol (melting point 160°C, intrinsic viscosity [η] 0.65). The copolymer molar ratios were 86.8 mol% terephthalic acid, 13.2 mol% ε-caprolactone, 50.0 mol% ethylene glycol, 49.2 mol% 1,4-butanediol, and 0.8 mol% diethylene glycol. The intrinsic viscosity [η] was measured using an equal weight mixture of phenol and tetrachloroethane as the solvent at a concentration of 0.5 g / dL and a liquid temperature of 20°C. The above-mentioned polyethylene terephthalate and low-melting point polyester copolymer were fed into a composite melt spinning apparatus equipped with a core-sheath composite spinneret with a hole diameter of 0.6 mm and 48 holes, and composite melt spinning was carried out at a nozzle temperature of 280°C with a polyethylene terephthalate:low-melting point polyester copolymer weight ratio of 2.7:1 to obtain concentric core-sheath filaments. The resulting yarn, in which 48 core-sheath filaments were bundled, was subjected to cooling, drawing, and relaxation treatments in the usual manner to obtain a core-sheath multifilament yarn of 280 dtex / 48 filaments. This core-sheath multifilament yarn was threaded on a 22-gauge circular knitting machine with a 33-inch pot diameter, and spun to a weight of 198 g / m. 2 A stretchable circular knitted fabric of 100g was obtained.

[0021] [Preparation of laminate and production of retroreflective three-dimensional molded body] A stretchable circular knit fabric was laminated on the adhesive layer side of the retroreflective material, and heated and pressurized at 110°C, 40 psi, and for 20 seconds to bond the retroreflective material and the stretchable circular knit fabric. The release substrate was then removed to obtain a laminate. This laminate was placed over the outside of a stainless steel bowl with a top diameter of 120 mm, a bottom diameter of 80 mm, and a height of 45 mm. The laminate was secured to the top of the bowl with metal clips, adjusting the size to avoid wrinkles. The product was then placed in an oven heated to 180°C and heat-treated at 180°C for 15 minutes. After heat treatment, the product was cooled to room temperature, and the bowl was removed to obtain a three-dimensional retroreflective molded product. The resulting three-dimensional retroreflective molded product was wrinkle-free and had good retroreflectivity on its curved surface.

[0022] Example 2 A retroreflective material was obtained using the same method as in Example 1, except that transparent microspheres with an average particle size of 55 μm were used and zinc oxide was vapor-deposited onto the transparent microspheres by vacuum deposition to form a reflective layer 1500 Å thick. The stretchable circular knit fabric used in Example 1 was laminated to the adhesive layer of this retroreflective material, and heated and pressurized at a temperature of 120°C, a pressure of 40 psi, and a time of 25 seconds to bond the retroreflective material and the stretchable circular knit fabric. The release substrate was then removed to obtain a laminate. This laminate was used to obtain a three-dimensional retroreflective molded body using the same method as in Example 1. The resulting three-dimensional retroreflective molded body was wrinkle-free and had good retroreflectivity on its curved surface.

[0023] Example 3 A retroreflective material was obtained using the same method as in Example 2, except that a polyurethane resin containing added carbon black was used. The stretchable circular knit fabric used in Example 1 was laminated to the adhesive layer of this retroreflective material, and heated and pressed at a temperature of 115°C, a pressure of 40 psi, and a time of 25 seconds to bond the retroreflective material and the stretchable circular knit fabric. The release substrate was then removed to obtain a laminate. This laminate was used to obtain a three-dimensional retroreflective molded body using the same method as in Example 1. The resulting three-dimensional retroreflective molded body was wrinkle-free and had good retroreflectivity on its curved surface.

[0024] Comparative Example 1 The intermediate obtained in Example 1 and the stretchable knit fabric used in Example 1 were laminated together via an adhesive resin layer, and heated and pressurized at a temperature of 110°C, a pressure of 40 psi, and a time of 20 seconds to bond the intermediate and the stretchable circular knit fabric. The release substrate was then removed to obtain a laminate. When this laminate was molded into a three-dimensional shape using the same method as in Example 1, numerous wrinkles were observed in some areas, making it unsuitable for practical use. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a schematic cross-sectional view of an example of a laminate used in the present invention. [Figure 2] FIG. 2 is a schematic plan view showing an example of an arrangement pattern of retroreflective areas and non-retroreflective areas in the retroreflective material used in the present invention. [Figure 3] FIG. 2 is a schematic plan view showing another example of the arrangement pattern of retroreflective areas and non-retroreflective areas in the retroreflective material used in the present invention. [Figure 4] FIG. 2 is a schematic plan view showing another example of the arrangement pattern of retroreflective areas and non-retroreflective areas in the retroreflective material used in the present invention. [Explanation of symbols]

[0026] 1 Support 2 Retroreflective Area 3 Non-retroreflective area 21 Adhesive layer 22 Reflective layer 23 Transparent microspheres

Claims

1. preparing a retroreflective material having a retroreflective area that has an adhesive layer, transparent microspheres embedded in the adhesive layer, and a reflective layer provided between the adhesive layer and the transparent microspheres, and a non-retroreflective area that does not have the adhesive layer, the transparent microspheres, or the reflective layer; a step of preparing a support made of an extensible knitted fabric which is knitted with a sheath-core multifilament yarn having a core component made of a high-melting point polymer and a sheath component made of a low-melting point polymer, and in which the sheath-core multifilament yarns are not fused to each other; a step of laminating the support on the adhesive layer side of the retroreflective material to obtain a laminate; A method for producing a retroreflective three-dimensional molded body, characterized in that heat is applied to the laminate to soften or melt the sheath component, thereby fusing the core-sheath multifilament yarns together and molding the laminate into a three-dimensional shape.

2. 2. The method for producing a retroreflective three-dimensional molded article according to claim 1, wherein the non-retroreflective areas are provided in a bias direction.

3. 2. The method for producing a three-dimensional retroreflective molded body according to claim 1, wherein the laminate is obtained by laminating a support on the adhesive layer side of the retroreflective material using the sheath component in the support as an adhesive.

4. 2. The method for producing a three-dimensional retroreflective molded article according to claim 1, wherein the stretchable knitted fabric is a weft knitted fabric.

5. 5. The method for producing a three-dimensional retroreflective molded article according to claim 4, wherein the weft knitted fabric is a circular knitted fabric.

6. A laminate comprising a retroreflective area having an adhesive layer, transparent microspheres embedded in the adhesive layer, and a reflective layer provided between the adhesive layer and the transparent microspheres, and a support laminated on the adhesive layer side of a retroreflective material having a non-retroreflective area not having the adhesive layer, the transparent microspheres, or the reflective layer, The support is a laminate used in the manufacturing method of a retroreflective three-dimensional molded body described in claim 1, which is an extensible knitted fabric knitted with a core-sheath multifilament yarn whose core component is made of a high-melting point polymer and whose sheath component is made of a low-melting point polymer, and in which the core-sheath multifilament yarns are not fused to each other.

7. 7. The laminate according to claim 6, wherein the support laminated on the fixing layer side is bonded to the retroreflective material using the sheath component as an adhesive.

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