Manufacturing method for molded products with fine irregularities on the surface

Abstract

To provide a method for manufacturing a molded article having minute bumps and dips on a surface that has excellent production efficiency.SOLUTION: A method for manufacturing a molded article having minute bumps and dips on a surface includes: a preparation step for preparing an injection molded body of a molding material in which a polymer material and a plurality of heat expandable capsules are mixed; and a heating step for heating the surface of the injection molded body using infrared rays emitted from an infrared ray emitting device to heat-expand the heat expandable capsules to provide minute bumps and dips onto the surface of the injection molded body. The injection molded body has a first surface nearest to the emitting part of the infrared ray emitting device, and a second surface being a surface other than the first surface. In the heating step, the first surface is irradiated with the infrared rays, and the outside of the first surface is also irradiated with the infrared rays. A reflection surface of a reflection tool is disposed on the outside of the first surface irradiated with the infrared rays and at least a part of the infrared rays emitted to the outside of the first surface is reflected by the reflection surface of the reflection tool, to be applied to at least a part of the second surface to provide minute bumps and dips onto the first surface and the second surface.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for producing a molded article having fine irregularities on its surface. More specifically, the present invention relates to a method for producing a molded article by heating an injection-molded article of a molding material, in which a polymer material and a plurality of thermally expandable capsules are mixed, with infrared radiation to expand the thermally expandable capsules, thereby forming fine irregularities on at least a portion of the surface. [Background technology]

[0002] Design is required for molded articles such as vehicle interior parts such as console boxes, instrument panels, and cover members, as well as building interior parts. To improve the design of molded articles, fine irregularities are imparted to the surfaces of the molded articles to impart a matte or fabric-like appearance.

[0003] As one method for producing a molded article having a finely textured surface, Patent Document 1 discloses a method in which a molding material in which a polymer material and a plurality of thermally expandable capsules are mixed is injection-molded, and the surface of the obtained injection-molded article is irradiated with infrared rays to expand the thermally expandable capsules, thereby imparting a finely textured surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2013 / 150916 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with the technology described in Patent Document 1, in order to impart irregularities to two or more surfaces of an injection-molded article, it is basically necessary to irradiate the injection-molded article with infrared rays two or more times, which leaves room for improvement in production efficiency.

[0006] In view of the above circumstances, an object of the present invention is to provide a method for producing a molded article having fine irregularities on its surface, which method is excellent in production efficiency. [Means for solving the problem]

[0007] The invention of claim 1, created to solve the above-mentioned problems, is a method for manufacturing a molded product having a finely textured surface, the method comprising: a preparation step of preparing an injection-molded product made of a molding material in which a polymer material and a plurality of thermally expandable capsules are mixed; and a heating step of heating the surface of the injection-molded product with infrared rays irradiated from an infrared irradiator to thermally expand the thermally expandable capsules and impart finely textured surfaces to the surface of the injection-molded product. The injection-molded product has a first surface closest to the irradiation unit of the infrared irradiator and a second surface other than the first surface. In the heating step, infrared rays are irradiated onto the first surface, and infrared rays are also irradiated onto the outside of the first surface. The method is characterized in that a reflecting surface of a reflecting jig is disposed outside the first surface onto which infrared rays are irradiated, and at least a portion of the infrared rays irradiated onto the outside of the first surface are reflected by the reflecting surface of the reflecting jig and directed onto at least a portion of the second surface, thereby imparting finely textured surfaces to the first surface and the second surface.

[0008] According to this configuration, by utilizing infrared reflection by the reflecting jig, two or more surfaces of an injection-molded body made of a molding material in which a polymer material and a plurality of thermally expandable capsules are mixed can be efficiently heated by a single infrared irradiation. Therefore, by a single infrared irradiation, the thermally expandable capsules can be expanded on two or more surfaces of the injection-molded body, and fine irregularities can be imparted to the surface. Therefore, according to the invention of claim 1, it is possible to obtain the effect of manufacturing molded articles having fine irregularities on the surface with excellent production efficiency.

[0009] The invention of claim 2 is the invention of claim 1, wherein the intensity of the infrared rays irradiated to the outside of the first surface is greater than the intensity of the infrared rays irradiated to the first surface.

[0010] Although the second surface is farther from the irradiation unit of the infrared irradiation device than the first surface, this configuration allows the intensity of infrared rays irradiated from the irradiation unit of the infrared irradiation device to the second surface to be increased. This allows the intensity of infrared rays hitting the first surface and the intensity of infrared rays hitting the second surface to be approximately the same, making the shapes of the fine irregularities formed on the first surface and the second surface (particularly the pattern created by the fine irregularities) identical or similar. Therefore, according to the invention of claim 2, in addition to the effect of the invention of claim 1, the effect of being able to uniform the shapes of the fine irregularities formed on the first surface and the second surface can be obtained.

[0011] The invention of claim 3 is the invention of claim 1 or 2, wherein when a plane perpendicular to the direction of infrared radiation from the radiation unit of the infrared radiation device is used as a reference plane, the angle of the second surface relative to the reference plane is θ, and the angle of the reflecting surface of the reflecting jig relative to the reference plane is α, the angle θ is in the range of more than 20° and less than 180°, and the angle α is (90°-θ / 2)±10°.

[0012] With this configuration, the infrared rays reflected by the reflecting jig can be directed substantially perpendicularly to the second surface, and therefore, in addition to the effects of the first or second invention, the third invention has the effect of more efficiently heating the second surface.

[0013] The invention of claim 4 is the invention of any one of claims 1 to 3, wherein the reflectance of the reflecting surface of the reflecting jig to infrared rays is 80% or more.

[0014] With this configuration, the infrared rays irradiated to the outside of the first surface can be more efficiently directed to the second surface by the reflecting jig. Therefore, according to the invention of claim 4, in addition to the effect of any one of the inventions of claims 1 to 3, the effect of more efficiently heating the second surface can be obtained.

[0015] The invention of claim 5 is the invention of any one of claims 1 to 4, wherein the material of at least the reflective surface of the reflecting jig is any one of gold, aluminum, silver, and copper.

[0016] These materials are easy to obtain and process, so this configuration makes it easy to manufacture the reflecting jig. Therefore, the invention of claim 5 has the effect of making the manufacturing method more suitable for industrial production in addition to the effect of any one of the inventions of claims 1 to 4. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 2 is a cross-sectional view showing an injection mold used to prepare an injection molded article in one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 2 is a perspective view showing an example of a heating step in a manufacturing method according to an embodiment of the present invention. [Figure 4] FIG. 10 is a schematic view (front view) showing a heating step in a method for producing a molded article according to another embodiment of the present invention. [Figure 5] FIG. 5 is an enlarged view of the left reflecting surface and its vicinity in FIG. 4. [Figure 6] FIG. 10 is a schematic diagram (front view) showing a modified example (when θ=30° and α=75°) of one embodiment of the present invention. [Figure 7] FIG. 10 is a schematic diagram (front view) showing a modified example (when θ=120° and α=30°) of one embodiment of the present invention. [Figure 8] FIG. 10 is a schematic diagram (front view) showing a modified example of an embodiment of the present invention in which fine irregularities are simultaneously formed on many surfaces. [Figure 9] FIG. 10 is a schematic diagram (front view) showing a modified example of an embodiment of the present invention in which an injection-molded body is arranged at an angle. [Figure 10] FIG. 3 is a cross-sectional view of the same portion as FIG. 2 of a molded product obtained according to one embodiment of the present invention. [Figure 11]1 is a photograph of the top surface of the injection-molded article used in Example 1 (before infrared irradiation). [Figure 12] 1 is a photograph of the side of the injection-molded article used in Example 1 (before infrared irradiation). [Figure 13] 1 is a photograph of the top surface of the molded article obtained in Example 1 (after infrared irradiation). [Figure 14] 1 is a photograph of the side of the molded article obtained in Example 1 (after infrared irradiation). [Figure 15] 1 is a photograph of the top surface of the molded article obtained in Comparative Example 1 (after infrared irradiation). [Figure 16] 1 is a photograph of the side of the molded article obtained in Comparative Example 1 (after infrared irradiation). DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described. It should be noted that matters necessary for carrying out the present invention other than those mentioned in this specification can be understood as design matters for a person skilled in the art based on the prior art. The present invention can be carried out based on the matters disclosed in this specification and drawings and the common general technical knowledge in the relevant field. In the following drawings, components and parts that perform the same function are denoted by the same reference numerals. Furthermore, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relationships.

[0019] The method for manufacturing a molded product having a finely textured surface according to this embodiment includes a preparation step of preparing an injection-molded product made of a molding material containing a polymer material and a plurality of thermally expandable capsules, and a heating step of heating the surface of the injection-molded product with infrared rays emitted from an infrared irradiation device, thereby thermally expanding the thermally expandable capsules and imparting a finely textured surface to the injection-molded product. The injection-molded product has a first surface closest to the irradiation unit of the infrared irradiation device and a second surface other than the first surface. In the heating step, infrared rays are irradiated onto the first surface, and infrared rays are also irradiated onto the outside of the first surface. Furthermore, a reflecting surface of a reflecting jig is disposed outside the first surface, onto which the infrared rays are irradiated. At least a portion of the infrared rays irradiated onto the outside of the first surface are reflected by the reflecting surface of the reflecting jig and directed toward at least a portion of the second surface. This imparts a finely textured surface to the first and second surfaces of the molded product. Each step is described in detail below.

[0020] [Preparation process] In the preparation step, an injection-molded body of a molding material in which a polymer material and a plurality of thermally expandable capsules are mixed is prepared. The preparation step can be performed according to a known method, for example, the method described in the above-mentioned Patent Document 1. Specifically, for example, first, a molding material in which a polymer material and a plurality of thermally expandable capsules are mixed is prepared.

[0021] The polymer material contained in the molding material serves as a matrix (base material) in which the thermally expandable capsules are dispersed. Materials conventionally used in injection-molded products can be used as the polymer material without any particular limitations. For example, various thermoplastic resins and various thermoplastic elastomers can be used. Examples of thermoplastic resins include polyolefin-based resins such as polyethylene and polypropylene; styrene-based resins such as polystyrene and acrylonitrile-styrene-butadiene resin (ABS); and vinyl chloride resins. Examples of thermoplastic elastomers include various thermoplastic elastomers such as styrene-based, olefin-based, ester-based, polyamide-based, vinyl chloride-based, and urethane-based elastomers. Thermoplastic elastomers are preferably used as the polymer material.

[0022] The thermally expandable capsules contained in the molding material are typically configured as particles containing an encapsulated substance (usually a gas, solid, or liquid that vaporizes (gasifies) when heated) that expands its volume when heated, enclosed within a thermoplastic resin shell. Examples of materials that can be used to construct the shell of such thermally expandable capsules include thermoplastic resins such as polyvinylidene chloride, vinylidene chloride-acrylonitrile copolymer, polyacrylonitrile, acrylonitrile copolymer, acrylic (co)polymers such as polymethyl methacrylate, and polyvinyl chloride. Examples of the encapsulated substance include low-boiling hydrocarbons such as n-pentane, n-hexane, n-butane, isobutane, and isopentane. Inert gases such as air, carbon dioxide, nitrogen, and argon (which may be partially or completely liquefied) can also be used as the encapsulated substance. When such a thermally expandable capsule is heated, the thermoplastic resin constituting the outer shell of the thermally expandable capsule softens, and the encapsulated substance contained inside the outer shell expands in volume (i.e., the encapsulated substance functions as an expanding agent), causing the thermally expandable capsule. Furthermore, the outer shell may be partially or entirely stretched beyond its expansion limit, causing the thermally expandable capsule to burst. Such capsule expansion and capsule rupture after expansion form fine irregularities on the surface of the injection-molded product.

[0023] The shape of the thermally expandable capsules before thermal expansion is not particularly limited. For example, they may be of various shapes such as a substantially spherical shape, a spindle shape, an irregular shape, or a cylindrical shape. From the viewpoint of dispersibility of the thermally expandable capsules and the decorative effect after thermal expansion, the thermally expandable capsules are preferably substantially spherical. The average particle size of the thermally expandable capsules before thermal expansion is approximately 15 μm or more and 40 μm or less. Furthermore, the average particle size of the thermally expandable capsules after thermal expansion is approximately 50 μm or more.

[0024] The average particle size is the average particle size of the thermally expandable capsules. This average particle size can be easily determined by observation using an optical microscope or an electron microscope (e.g., a transmission electron microscope or a scanning electron microscope). For example, a predetermined number (e.g., about 40) of thermally expandable capsules are randomly selected from a micrograph of the cross section of an injection-molded product, and the particle size of each thermally expandable capsule is measured. Here, if the thermally expandable capsules are spherical, the diameter is the particle size; if they are non-spherical, the particle size is the arithmetic mean of the longest and shortest lengths of the thermally expandable capsules. The average value of the measured particle sizes of the thermally expandable capsules is then defined as the average particle size of the thermally expandable capsules. The average particle size of the thermally expandable capsules before thermal expansion can be determined from a cross-sectional photograph of a region of the injection-molded product where the thermally expandable capsules have not thermally expanded, and the average particle size of the thermally expandable capsules after thermal expansion can be determined from a cross-sectional photograph of a region of the injection-molded product where the thermally expandable capsules have thermally expanded.

[0025] Examples of commercially available thermally expandable capsules (including those commercially available in a masterbatch form) that are preferably used include those manufactured by Sekisui Chemical Co., Ltd. under the trade name "ADVANCELL (registered trademark)", those manufactured by Akzo Nobel under the trade name "EXPANCEL (registered trademark) Microsphere", those manufactured by Matsumoto Yushi Seiyaku Co., Ltd. under the trade name "Matsumoto Microsphere (registered trademark)", and those manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd. under the trade name "Daiform (registered trademark)".

[0026] The amount of the thermally expandable capsules to be blended is, for example, about 0.1% by mass to 10% by mass when the total amount of the molding material is taken as 100% by mass, but is not particularly limited to this amount.

[0027] In addition to the polymer material and thermally expandable capsules, the molding material may contain various auxiliary components as needed. Examples of such auxiliary components include powdery and / or fibrous solid fillers. Examples of such solid fillers include ceramic powders (including various inorganic compound powders such as talc; the same applies hereinafter), carbon powders (e.g., carbon black), wood flour, ceramic fibers, and carbon fibers. The amount of filler to be added varies depending on the type of filler used and the intended use of the injection-molded product. Typically, the amount is 1 to 60% by mass, where the total amount of the molding material is 100% by mass. Alternatively, the molding material may be substantially filler-free. In addition to the solid fillers, the molding material may contain additives as auxiliary components as needed. Examples of such additives include antioxidants, light stabilizers, UV absorbers, plasticizers, lubricants, colorants (pigments, dyes), flame retardants, dispersants, antibacterial agents, and antistatic agents.

[0028] The molding material can be prepared by mixing the above polymer material, the above thermally expandable capsules, and, if necessary, the above subcomponents, according to a known method.

[0029] The prepared molding material is then injection-molded using an injection molding machine. Injection molding can be carried out according to a known method, an example of which is shown below.

[0030] FIG. 1 is a schematic cross-sectional view of an injection molding die 10, which is an example of an injection molding die used in injection molding, as exemplified below. The injection molding die 10 has a pair of dies 12, 14 that can be opened and closed. The pair of dies 12, 14 is composed of a fixed die 12 and a movable die 14, and a predetermined molding cavity 26 is formed inside when the dies are closed. The fixed die 12 of the injection molding die 10 has a locating ring 16 for inserting an injection nozzle (not shown) of an injection molding machine, and a sprue bushing 20 with a sprue 18 formed inside. A sprue 22, an injection gate 24, and a molding cavity 26 are roughly formed on the inner surfaces (parting surfaces) of the fixed die 12 and the movable die 14 of the injection molding die 10, respectively, when the dies are closed.

[0031] A heated and melted molding material 30 is injected into the injection mold 10, filling the molding cavity 26 of a predetermined shape with the molding material 30. At this time, the melted molding material 30 passes through the sprues 18 and 22 and enters the molding cavity 26 from the injection gate 24, and is filled inside the molding cavity 26.

[0032] Next, the filled molding material 30 is cooled and solidified in the molding cavity to obtain the injection-molded article 40. Specifically, for example, as shown in Fig. 1, the molding material 30 filled in the molding cavity 26 of the injection molding die 10 is cooled to a temperature below the glass transition temperature of the polymer material and solidified.

[0033] After cooling and solidifying, the movable die 14 of the injection molding die 10 shown in Figure 1 is moved to open the injection molding die 10, and the injection molded article 40 formed in the molding cavity 26 is removed. This allows the injection molded article 40 to be obtained. In other words, the injection molded article 40 can be prepared.

[0034] FIG. 2 shows a cross section taken along the II-II direction in FIG. 1. In FIG. 2, thermally expandable capsules 60, each having an outer shell 62 and an encapsulated substance 64 housed within the shell, are dispersed in a polymer material 50. Typically, the thermally expandable capsules 60 contained in the molding material 30 have a softening temperature (expansion start temperature: generally 160°C to 180°C) lower than the injection molding temperature of the molding material 30 (generally 150°C to 250°C). However, the thermally expandable capsules 60 barely undergo thermal expansion. This is for the following reason: The molding material 30 filled in the molding cavity 26 is under internal pressure. Therefore, if the movable mold 14 is opened before the molding material 30 cools and solidifies, the pressure applied to the molding material 30 is released, causing the thermally expandable capsules 60 in the molding material 30 to thermally expand. However, by cooling and solidifying the molding material 30 while the internal pressure is still applied to the molding material 30, thermal expansion of the thermally expandable capsules 60 is substantially prevented.

[0035] [Heating process] In the heating step, the surface of the injection-molded body is heated by infrared rays irradiated from an infrared irradiation device, causing the thermally expandable capsules to thermally expand and imparting fine irregularities to the surface of the injection-molded body. An example of how to carry out the heating step is shown in Figures 3 to 5. Note that Figure 3 is a perspective view, and Figure 4 is a view from the downstream direction of the belt conveyor (referred to as a front view in this specification).

[0036] 3, a reflecting jig 70 is placed below the injection-molded body 40, and these are placed on a belt conveyor 80. Above the belt conveyor 80, an infrared irradiation device 90 is installed.

[0037] The infrared irradiating device 90 has an irradiating section 92 in which infrared light sources (e.g., infrared lamps, infrared lasers) are arranged in a row, and can irradiate infrared rays in a line. However, the configuration of the irradiating section 92 of the infrared irradiating device 90 is not limited to this. For example, the irradiating section 92 of the infrared irradiating device 90 may be capable of irradiating infrared rays in a planar manner.

[0038] The infrared rays irradiated from the infrared irradiating device 90 may be any of near-infrared rays (i.e., infrared rays with a wavelength of 0.7 μm or more and 2.5 μm or less), mid-infrared rays (i.e., infrared rays with a wavelength of more than 2.5 μm and 4.0 μm or less), and far-infrared rays (i.e., infrared rays with a wavelength of more than 4.0 μm and 1000 μm or less), but shorter wavelengths are preferred because they can heat the surface of the injection-molded body 40 in a short period of time. In other words, near-infrared rays are preferred as the infrared rays.

[0039] The amount of infrared radiation emitted by the infrared radiation device 90 is selected appropriately so as to heat the first surface 42 and the second surface 44 of the injection-molded body 40 to a temperature that is equal to or higher than the temperature at which the thermally expandable capsule 60 can thermally expand, but lower than the temperature at which the injection-molded body 40 does not undergo thermal decomposition. The amount of infrared radiation emitted by the infrared radiation device 90 can be controlled by adjusting the settings of the infrared radiation device 90 and the distance between the radiation unit 92 of the infrared radiation device 90 and the injection-molded body (particularly the position of the radiation unit 92 in the vertical direction in the drawing).

[0040] In the illustrated example, the infrared irradiation device 90 is positioned above the belt conveyor 80 in order to irradiate the injection-molded body 40 with infrared rays from above. However, the positioning of the infrared irradiation device 90 is not limited to this, and the infrared irradiation device 90 can also be positioned so as to irradiate the injection-molded body 40 with infrared rays from the side or below.

[0041] In the illustrated example, injection-molded body 40 has a trapezoidal prism shape in which two opposing side surfaces of a quadrangular prism are inclined. As shown in FIG. 4, the top surface 42 of injection-molded body 40 is the first surface 42 that is closest to the irradiation unit 92 of the infrared irradiation device 90 when viewed as a whole. The two inclined side surfaces 44 of injection-molded body 40 are the second surface 44, which is the surface other than first surface 42. Note that the shape of injection-molded body 40 is not limited to that shown in the illustrated example. The shape of injection-molded body 40 is arbitrary as long as it has two or more surfaces. In addition, in the illustrated example, the first surface and second surface are flat, but they may also be curved.

[0042] Reflecting jig 70 has a flat plate portion 72 opposed to injection molded body 40, and a pair of bent portions 74 bent on the outside of bottom surface 46 of injection molded body 40. Surface 74A of bent portions 74 facing injection molded body 40 is configured as a reflective surface capable of reflecting infrared rays.

[0043] Therefore, the reflecting surface 74A is made of a material capable of reflecting infrared rays. The material is not particularly limited as long as it is capable of reflecting infrared rays, but is preferably one of gold, aluminum, silver, and copper. These materials are easy to obtain and process, so this configuration makes it easy to manufacture the reflecting jig 70.

[0044] As a specific operation of the heating step, first, a reflecting jig 70 is placed on a belt conveyor 80, and then the injection-molded body 40 is placed thereon. Then, the belt conveyor 80 is operated, and the injection-molded body 40 is moved together with the reflecting jig 70 in the direction of the arrow in Fig. 3. An infrared irradiator 90 is fixed, and when the injection-molded body 40 comes below the infrared irradiator 90, infrared rays are irradiated onto the injection-molded body 40. Note that X in Fig. 4 indicates the direction of infrared irradiation, which is perpendicular to the first surface 42 of the injection-molded body 40 in the illustrated example.

[0045] Here, the first surface 42 of the injection-molded body 40 is closest to the irradiation unit 92 of the infrared irradiation device 90, while the second surface 44 is inclined. Therefore, when viewed as a whole, the second surface 44 is farther from the irradiation unit 92 of the infrared irradiation device 90 than the first surface 42. Therefore, it is difficult for a sufficient amount of infrared rays to reach the second surface 44. When the reflecting jig 70 is not used, i.e., in the conventional technology, when the infrared irradiation device 90 irradiates the first surface 42 and the second surface 44 with infrared rays, a difference in temperature occurs between the first surface 42 and the second surface 44 due to the difference in distance from the irradiation unit 92 of the infrared irradiation device 90. Therefore, it is difficult to simultaneously expand the thermally expandable capsules of the first surface 42 and the second surface 44 in order to impart irregularities to the surfaces of the first and second surfaces. As a result, in the prior art, in order to expand the thermally expandable capsules on the first surface 42 and the second surface 44, it was necessary to irradiate the first surface 42 with infrared light and the second surface 44 with infrared light separately, which increased the number of processes and was detrimental to production efficiency.

[0046] However, in this embodiment, a reflecting jig 70 is used. Specifically, a reflecting surface 74A of the reflecting jig 70 is disposed on the outer side of the first surface 42 of the injection-molded body 40, which is irradiated with infrared rays. Therefore, in the heating step, infrared rays are irradiated onto the first surface 42, and also onto the outer side of the first surface 42. At least a portion of the infrared rays irradiated onto the outer side of the first surface 42 is reflected by the reflecting surface 74A of the reflecting jig 70 and directed onto at least a portion of the second surface 44. This allows not only the first surface 42 but also the second surface 44 to be heated to a temperature at which the thermally expandable capsule can expand. In this way, in this embodiment, the thermally expandable capsule is expanded on two or more surfaces (in the illustrated example, on the first surface 42 and two second surfaces 44) in the heating step, and fine irregularities are imparted to the surface.

[0047] In this way, by utilizing the infrared reflection by the reflecting jig 70, two or more surfaces can be efficiently heated with a single infrared irradiation, and therefore, according to the method for manufacturing a molded product of this embodiment, it is possible to obtain the effect of manufacturing a molded product having fine irregularities on the surface with excellent production efficiency.

[0048] Here, the higher the infrared reflectivity of the reflecting surface 74A of the reflecting jig 70, the more efficiently the infrared rays irradiated to the outside of the first surface can be directed onto the second surface by the reflecting jig. Therefore, the infrared reflectivity of the reflecting surface 74A of the reflecting jig 70 is preferably 50% or more, and more preferably 80% or more. Such a reflectivity has the effect of more efficiently heating the second surface 44 of the injection-molded body 40.

[0049] FIG. 5 shows an enlarged view of the left-hand reflecting surface 74A in FIG. 4 and its vicinity. As shown in FIG. 5, a plane perpendicular to the irradiation direction X of the infrared rays from the irradiation unit 92 of the infrared irradiator 90 is defined as a reference plane S. The angle of the second surface 44 of the injection-molded body 40 relative to the reference plane S is defined as θ (note that angle θ is the angle on the injection-molded body 40 side). The angle of the reflecting surface 74A of the reflecting jig 70 relative to the reference plane S is defined as α (note that angle α is the angle on the side farther from the injection-molded body 40). In this embodiment, angles α and θ are not particularly limited as long as the infrared rays can be reflected by the reflecting surface 74A to the second surface 44. Here, when angle α is (90°-θ / 2), the infrared rays from the irradiation unit 92 of the infrared irradiator 90 can be applied perpendicularly to the second surface 44.

[0050] Here, when θ is 20° or less, second surface 44 is close to horizontal, and infrared rays from irradiation unit 92 of infrared irradiation device 90 are likely to hit second surface 44 directly. Also, in order to reflect infrared rays from second surface 44, angle α between reference plane S and reflecting surface 74A becomes close to vertical. Also, for injection-molded body 40, angle θ does not become 0° or 180°.

[0051] Therefore, from the viewpoint of efficiently heating the second surface 44 of the injection molded body 40, it is preferable that the angle θ is in the range of more than 20° and less than 180°, and the angle α is in the range of (90°-θ / 2)±10°, more preferably in the range of (90°-θ / 2)±5°, and even more preferably in the range of (90°-θ / 2)±3°.

[0052] In addition, when the second surface 44 is a curved surface, the angle α may be determined based on (90°-θ / 2), where θ is the angle between the plane connecting the upper and lower ends of the second surface 44 (or the line connecting the upper and lower ends of the second surface 44 in the cross section) and the reference plane S.

[0053] As a modified example of this embodiment, FIG. 6 shows an example where the angle θ is 30°, and FIG. 7 shows an example where the angle θ is 120°. In FIG. 6, the angle α is 75° according to the formula: (90°-θ / 2). It can be seen that when the angle θ is small, the dimension of the bending portion 74 of the reflecting jig 70 in the extension direction (the direction perpendicular to the bending line of the reflecting jig 70) (i.e., the dimension of the reflecting surface 74A in that direction) should be increased. In this way, by appropriately adjusting the dimension of the reflecting surface 74A of the reflecting jig 70 according to the angle θ of the injection-molded body 40, infrared rays can be reflected by the reflecting surface 74A of the reflecting jig 70 and applied to the second surface 44. Note that when the angle θ is an acute angle, the second surface 44 is typically heated by infrared rays from the infrared irradiation device 90 and infrared rays reflected by the reflecting surface 74A.

[0054] In Figure 7, angle α is 30° according to the formula: (90°-θ / 2). From Figure 7, it can be seen that angle θ may be an obtuse angle. Furthermore, as shown in the figure, by placing injection-molded body 40 on stage 110, it is possible to apply infrared rays reflected by reflecting surface 74A to the entire surface of second surface 44. Note that when angle θ is an obtuse angle or a right angle, all of the infrared rays that strike second surface 44 will normally be reflected by reflecting surface 74A of reflecting jig 70.

[0055] As described above, the second surface 44 is farther from the irradiation unit 92 of the infrared irradiation device 90 than the first surface 42, making it difficult for a sufficient amount of infrared light to strike the second surface 44. Therefore, the intensity of the infrared light irradiated from the irradiation unit 92 of the infrared irradiation device 90 toward the outside of the first surface 42 may be made greater than the intensity of the infrared light irradiated toward the first surface 42. In this case, the intensity of the infrared light striking the second surface can be increased. As a result, the intensity of the infrared light striking the first surface and the intensity of the infrared light striking the second surface can be easily made to be approximately the same, making it easier to make the shapes of the fine irregularities formed on the first surface and the second surface (especially the pattern created by the fine irregularities) identical or similar. That is, the effect is achieved of making the shapes of the fine irregularities formed on the first surface and the second surface uniform. Furthermore, by changing the intensity of the infrared light irradiated toward the outside of the first surface 42, it becomes easier to adjust the intensity of the infrared light striking the second surface, thereby increasing the degree of freedom in designing the reflecting surface 74A of the reflecting jig 70.

[0056] In the example described above, the reflecting surface 74A of the reflecting jig 70 is a single flat surface, but this is not limited to this. For example, the reflecting surface 74A may be a surface formed by combining two or more flat surfaces. Furthermore, for example, the reflecting surface 74A may be a concave surface in order to increase the amount of infrared light reflected to the second surface.

[0057] Furthermore, in the example described above, the reflecting jig 70 is a single member having a flat plate portion 72 and a pair of bent portions 74. However, the form of the reflecting jig 70 is not limited to this. For example, the reflecting jig 70 may be composed of two independent reflecting plates, which may be arranged on either side of a pair of second surfaces 44 of the injection-molded body 40. Specifically, for example, in FIG. 3, a pair of reflecting plates may be arranged on both ends of the belt conveyor 80 in a direction perpendicular to the flow direction. Furthermore, the injection-molded body 40 does not have to be arranged on the reflecting jig 70.

[0058] In the example described above, fine irregularities are simultaneously provided on a total of three surfaces, namely, the first surface 42 and the pair of second surfaces 44. However, the number of surfaces to which fine irregularities are provided is not limited to this, as long as there are two or more surfaces. For example, fine irregularities may be simultaneously provided on the first surface 42 and one of the pair of second surfaces 44.

[0059] FIG. 8 shows a modified example of simultaneously imparting fine irregularities to many surfaces. In the example shown in FIG. 8, injection-molded body 40 further has first surface 42 and two second surfaces, second surface 44A and second second surface 44B. Correspondingly, reflecting jig 70 has first reflecting surface 74A and second reflecting surface 74B. As can be seen from FIG. 8, infrared rays reflected by first reflecting surface 74A can be directed to second surface 44A, and infrared rays reflected by second reflecting surface 74B can be directed to second surface 44B. In this way, by increasing the number of reflecting surfaces of the reflecting jig, it is possible to simultaneously impart fine irregularities to many surfaces.

[0060] In particular, in FIG. 8, two reference planes perpendicular to the infrared irradiation direction X are designated as reference plane S1 and reference plane S2, respectively. The angle between reference plane S1 and second surface 44A is designated as θ1. The angle between reference plane S1 and first reflecting surface 74A is designated as α1. The angle between reference plane S2 and second surface 44B is designated as θ2. The angle between reference plane S2 and second reflecting surface 74B is designated as α2. In FIG. 8, θ1 = 60°, α1 = 60°, θ2 = 120°, and α2 = 30°. The angles α1 and α2 respectively satisfy the formulas: {90° - (θ1) / 2} and {90° - (θ2) / 2}. Since θ2 is an obtuse angle, the injection-molded body 40 is placed on a stage 110. This configuration allows the reflected infrared light to efficiently strike second surface 44A and second second surface 44B.

[0061] In the example described above, all of the first surfaces 42 are perpendicular (i.e., horizontal) to the direction of infrared light emitted from the infrared light irradiation device, but the first surfaces 42 may be tilted from the horizontal. The injection-molded body 40 may also be arranged at an angle. Arranging the injection-molded body 40 at an angle is effective when the first surface 42 (top surface) of the injection-molded body 40 and the surface 46 (bottom surface) opposite thereto are not parallel.

[0062] FIG. 9 shows a modified example in which the injection-molded body 40 is arranged at an angle. In the example shown in FIG. 9, the first surface 42 (top surface) and the bottom surface 46 of the injection-molded body 40 are not parallel. A stand 110 is installed below the bottom surface 46 of the injection-molded body 40. Therefore, the first surface 42 of the injection-molded body 40 is close to horizontal. By making the first surface 42 of the injection-molded body 40 close to horizontal in this way, it becomes easier to uniformly expand the thermally expandable capsules over the entire first surface 42. In particular, it is preferable that the angle between the first surface 42 and a plane perpendicular to the irradiation direction of the infrared rays irradiated from the infrared irradiation device 90 is 10° or less.

[0063] In addition, by tilting the injection molded body 40 using a table 110 or the like in this manner, the angle θ between the reference plane S and the second surface 44 can be adjusted, and the second surface 44 can also be heated efficiently.

[0064] In the above, infrared rays are applied to the entire surfaces of both the first surface 42 and the second surface 44. If there are areas on the first surface 42 and the second surface 44 where irregularities should not be provided, a heat-shielding material or the like can be placed on those areas to prevent irregularities from being provided in those areas.

[0065] In the above, the infrared irradiation device 90 is fixed and the injection-molded body 40 is moved by the belt conveyor 80, but the present embodiment is not limited to this. A mode in which the injection-molded body 40 is fixed and the infrared irradiation device 90 is moved, and a mode in which both the injection-molded body 40 and the infrared irradiation device 90 are moved are also possible.

[0066] When the infrared light is infrared laser light, since laser light has a high degree of linearity, it is possible to homogenize the light that strikes the first surface 42 and the light that strikes the second surface 44 of the injection-molded body 40. This makes it possible to improve the quality of the fine irregularities formed on the first surface 42 and the second surface 44.

[0067] In this embodiment, although minute irregularities can be formed on two or more surfaces by a single infrared irradiation, infrared irradiation may be performed two or more times. When infrared irradiation is performed two or more times, infrared rays may be irradiated onto at least one of the first surface 42 and the second surface 44, or may be irradiated onto a surface other than the first surface 42 and the second surface 44.

[0068] In this manner, a molded article having fine irregularities on the surface can be obtained. Figure 10 shows a cross-sectional view of an example of a molded article corresponding to Figure 2.

[0069] As shown in Fig. 10, in a molded article 100, thermally expandable capsules 60 each having an outer shell 62 and an encapsulated substance 64 housed therein are dispersed in a polymer material 50. In Fig. 10, the upper surface (i.e., the top surface) of the molded article 100 is the surface that is exposed to infrared rays. The temperature of the surface layer portion 102 on the upper surface side is more likely to increase due to infrared rays. Therefore, in the surface layer portion 102, the encapsulated substance 64 expands in volume, stretching the outer shell 62 and causing the thermally expandable capsules 60 to expand. The expansion of the thermally expandable capsules 60 creates fine irregularities on the top surface.

[0070] On the other hand, in the portion (lower portion) 104 below the surface portion, the temperature does not rise to a temperature sufficient to expand the thermally expandable capsule 60. Therefore, the thermally expandable capsule 60 hardly expands.

[0071] In the surface layer portion 102, the average particle size of the thermally expandable capsules 60 may be 50 μm or more (for example, approximately 50 μm or more and 150 μm or less). In the lower layer portion 104, the average particle size of the thermally expandable capsules 60 may be 50 μm or less. With this average particle size range, good irregularities are formed in the surface layer portion 102, and a decrease in density is suppressed in the portion below the surface layer portion 102, ensuring the rigidity of the molded product 100.

[0072] The above is just one example, and all of the thermally expandable capsules 60 contained in the molded product 100 may be expanded. Furthermore, some of the thermally expandable capsules 60 may have expanded too much and burst in the molded product 100. When a thermally expandable capsule 60 bursts, a recess is formed corresponding to the burst outer shell 62 of that thermally expandable capsule 60.

[0073] The molded article 100 can have a cloth-like appearance due to the fine irregularities imparted to the surface. The molded article 100 can be used in a variety of applications in which injection-molded articles are used, and suitable applications include vehicle interior parts such as console boxes, instrument panels, and cover members, as well as building interior parts. [Example]

[0074] Examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples.

[0075] Example 1 A molding material was prepared by mixing the styrene-based thermoplastic elastomer "Actimer" (manufactured by Riken Technos Corporation) as a polymer material with the thermally expandable microcapsules "ADVANCELL" (manufactured by Sekisui Chemical Co., Ltd.) This molding material was molded using an injection molding machine to obtain an injection-molded product.

[0076] An aluminum reflecting jig with a pair of opposing ends bent was prepared. This reflecting jig was placed on a belt conveyor, and an injection-molded body was placed on top of it. A near-infrared irradiation device "HYW30-MR" (manufactured by Hibeck) was installed in front of and above the injection-molded body. When the injection-molded body was directly below the near-infrared irradiation device, the distance between the top surface of the injection-molded body and the near-infrared irradiation device was 40 mm, and the distance between the bottom edge of the side of the injection-molded body and the near-infrared irradiation device was 76 mm.

[0077] The belt conveyor was operated at a moving speed of 40 mm / sec, and the injection-molded body was irradiated with near-infrared rays using a near-infrared irradiation device. That is, near-infrared irradiation was performed in the manner shown in FIG. 3 . At this time, infrared rays were irradiated onto the top surface of the injection-molded body and the outer side of the top surface of the injection-molded body, and a portion of the infrared rays irradiated onto the outer side of the top surface was irradiated onto a pair of opposing side surfaces of the injection-molded body by the reflecting surface of the reflecting jig. Furthermore, in the near-infrared irradiation device, the ratio of the infrared radiation output toward the top surface of the injection-molded body to the infrared radiation output toward the outer side of the top surface was set to 3:7. When the temperatures of the top and side surfaces of the injection-molded body were measured, both were 143°C, confirming that the top and side surfaces of the injection-molded body were heated to the same degree. After infrared irradiation, it was visually confirmed that fine irregularities were formed on the top and side surfaces of the injection-molded body. In this manner, a molded product of Example 1 was obtained, in which fine irregularities were formed on the top and side surfaces.

[0078] For reference, photographs of the top and side of an injection-molded body before infrared irradiation and the top and side of a molded product (injection-molded body after infrared irradiation) are shown in Figures 11 to 14, respectively. In Figure 11 (top) and Figure 12 (side), which show the injection-molded body before infrared irradiation, the surface of the injection-molded body is smooth and glossy because there are no irregularities. However, in Figure 13 (top) and Figure 14 (side), which show the molded product (injection-molded body after infrared irradiation), it can be seen that the surface of the injection-molded body has been given irregularities, resulting in a matte surface.

[0079] Comparative Example 1 An injection-molded body identical to that of Example 1 was prepared. Infrared irradiation of the injection-molded body was carried out in the same manner as in Example 1, except that a reflecting jig was not used. As a result, it was visually confirmed that fine irregularities were formed on the top surface of the injection-molded body after infrared irradiation, but that fine irregularities were not formed on the side surface. For reference, photographs of the top and side surfaces of the injection-molded body after infrared irradiation are shown in Figures 15 and 16. From Figure 15, it can be seen that irregularities were imparted to the top surface of the injection-molded body after infrared irradiation. However, from Figure 16, it can be seen that irregularities were not imparted to the side surface of the injection-molded body after infrared irradiation, and that there was no change from before infrared irradiation.

[0080] From the above results, it can be seen that the production method disclosed herein can impart fine irregularities to two or more surfaces of an injection-molded article by a single infrared irradiation, resulting in excellent production efficiency.

[0081] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. [Explanation of symbols]

[0082] 10 injection mold 12 Fixed type 14 Movable type 16 Locate Ring 18 sprues 20 sprue bushing 22 sprues 24 Injection Gate 26 Molding cavity 30 Molding materials 40 Injection molded body 42 Page 1 44 Side 2 50 Polymer Materials 60 Thermally Expandable Capsule 62 Outer shell 64 Included substances 70 Reflector 74 Bend 74A Reflective surface 80 Conveyor Belt 90 Infrared irradiation device 92 Irradiation unit 100 Molded products 110 units

Claims

1. a preparation step of preparing an injection molded body of a molding material in which a polymer material and a plurality of thermally expandable capsules are mixed; a heating step of heating the surface of the injection molded body with infrared rays irradiated from an infrared irradiation device to thermally expand the thermally expandable capsules and impart fine irregularities to the surface of the injection molded body; A method for producing a molded article having fine irregularities on its surface, comprising: the injection-molded body has a first surface closest to the irradiation unit of the infrared irradiation device and a second surface other than the first surface, In the heating step, infrared rays are irradiated onto the first surface and also onto an outside of the first surface, an intensity of the infrared ray emitted from the irradiation unit of the infrared irradiator so as to be irradiated onto the outside of the first surface is greater than an intensity of the infrared ray emitted from the irradiation unit of the infrared irradiator so as to be irradiated onto the first surface; a reflecting surface of a reflecting jig is disposed outside the first surface onto which the infrared rays are irradiated, and at least a portion of the infrared rays irradiated onto the outside of the first surface is reflected by the reflecting surface of the reflecting jig and directed onto at least a portion of the second surface; A method for manufacturing a molded product, comprising imparting fine irregularities to the first surface and the second surface.

2. When a plane perpendicular to the irradiation direction of the infrared rays from the irradiation unit of the infrared irradiation device is used as a reference plane, the angle of the second surface with respect to the reference plane is θ, and the angle of the reflecting surface of the reflecting jig with respect to the reference plane is α, the angle θ is in the range of more than 20 ° and less than 180 °, and the angle α is (90 ° - θ / 2) ± 10 °. The method for producing a molded product according to claim 1.

3. The method for producing a molded product according to claim 1 or 2, wherein the reflecting surface of the reflecting jig has an infrared reflectance of 80% or more.

4. The method for manufacturing a molded product according to any one of claims 1 to 3, wherein a material of at least the reflective surface of the reflecting jig is any one of gold, aluminum, silver, and copper.

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