Manufacturing method of resin molded products, manufacturing equipment, manufacturing method of equipment

Abstract

To provide a technology advantageous for improving the quality of resin molded products.SOLUTION: A method for manufacturing a resin molded product involves by using a manufacturing apparatus comprising a first mold having a flow path for a molten resin and forming a first surface of the resin molded product, a second mold forming a second surface opposite to the first surface of the resin molded product, and a valve pin capable of moving forward and backward in a prescribed direction and opening and closing the flow path. A part of the first mold is positioned between the valve pin and the second mold in the prescribed direction when the molten resin is injected from the flow path into a cavity formed between the first mold and the second mold.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a resin molded product and a manufacturing apparatus for manufacturing a resin molded product. , etc. Regarding. [Background technology]

[0002] Resin molded products are often used as decorative articles and exterior components, such as exterior covers for products. It is particularly desirable for such resin molded products to have high-quality exterior surfaces that are visible to users under normal use conditions. Of course, even for components that are not visible to users under normal use conditions, having a high-quality exterior contributes to improved product value and user satisfaction.

[0003] Patent Document 1 proposes a method for preventing the appearance of synthetic resin flow marks (weld lines) on the exterior surface of a front body when injection molding a combustion operating tool (front body) for a gas stove. Specifically, it proposes that when injection molding a front body comprising a disk-shaped main body and a cone, a cylindrical gate communicating with a hot runner is connected to the tip of the cavity that forms the cone so that the gate axis coincides with the central axis of the cone. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-87641 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the investigations of the present inventors, it has been found that there is room for improvement in the quality of conventional resin molded products. Therefore, an object of the present invention is to provide a technique that is advantageous in improving the quality of resin molded products. [Means for solving the problem]

[0006] A first aspect of the present invention is a method for manufacturing a resin molded product using a manufacturing device including a first mold having a flow path for molten resin and forming a first surface of the resin molded product, a second mold forming a second surface of the resin molded product opposite to the first surface, and a valve pin that can advance and retreat in a predetermined direction and open and close the flow path, wherein when molten resin is injected from the flow path into a cavity formed between the first mold and the second mold, a part of the first mold is positioned in a part between a tip surface of the valve pin and the second mold in the predetermined direction, and the first mold is not positioned in a part other than the part between the tip surface of the valve pin and the second mold in the predetermined direction. Without, before When opening the flow path, the tip surface of the valve pin is moved away from the part of the first mold so that the part of the first mold is positioned on an extension of the central axis of the valve pin.

[0007] In addition, a second aspect of the present invention is a method for manufacturing a resin molded product using a manufacturing device including: a first mold having a flow path for molten resin and forming a first surface of the resin molded product; a second mold forming a second surface of the resin molded product opposite to the first surface; and a valve pin that can advance and retreat in a predetermined direction and open and close the flow path, wherein, when molten resin is injected from the flow path into a cavity formed between the first mold and the second mold, a part of the first mold is positioned between a tip surface of the valve pin and the second mold in the predetermined direction, and the first mold is not positioned in any part other than the part between the tip surface of the valve pin and the second mold in the predetermined direction, and when the flow path is closed, at least a part of the tip surface of the valve pin that includes a central axis of the valve pin is abutted against the part of the first mold; A manufacturing method characterized by is .

[0008] A third aspect of the present invention is a manufacturing apparatus for manufacturing a resin molded product, comprising: a first mold having a flow path for molten resin and forming a first surface of the resin molded product; a second mold forming a second surface of the resin molded product opposite to the first surface; and a valve pin that can advance and retreat in a predetermined direction and open and close the flow path, wherein, in the predetermined direction, a part of the first mold is disposed between a tip surface of the valve pin on the side of a cavity formed between the first mold and the second mold and a part of the second mold, and the first mold is disposed in a part other than the part between the tip surface of the valve pin and the second mold. Not in front When the flow path is opened, the tip surface of the valve pin is separated from the portion of the first mold, and when the flow path is closed, at least a portion of the tip surface of the valve pin that includes the central axis of the valve pin abuts against the portion of the first mold.

[0009] A fourth aspect of the present invention is a resin molded product having a first surface on which a convex portion is provided and a second surface opposite to the first surface, wherein the convex portion has a molding mark formed by a valve pin of a manufacturing device that produced the resin molded product, and at least a portion of the tip surface of the valve pin is not transferred to the molding mark. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a technique that is advantageous in improving the quality of resin molded products. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view of an injection molding apparatus according to a first embodiment. [Figure 2] 1A is a diagram showing a closed state of the hot runner gate in the first embodiment, and FIG. 1B is a diagram showing an open state of the hot runner gate in the first embodiment. [Figure 3] 1A is a diagram showing a stage in which resin continues to be injected into the cavity CAV from the resin nozzle 1 in embodiment 1. FIG. 1B is a diagram showing a stage in which the resin has completely filled the cavity CAV and solidified in embodiment 1. [Figure 4] 1A is a perspective view of the resin molded product 40 according to the first embodiment, seen from the side opposite to the exterior surface, and FIG. 1B is a perspective view of the resin molded product 40 according to the first embodiment, seen from the exterior side. [Figure 5] 3 is an enlarged perspective view of the vicinity of a protrusion EX of the resin molded product 40 according to the first embodiment. FIG. [Figure 6] FIG. 6 is a schematic cross-sectional view of an injection molding apparatus according to a second embodiment. [Figure 7] (a) A perspective view of a resin molded product 70 according to embodiment 2, seen from the opposite side to the exterior surface. (b) A view showing an example of the cross-sectional shape of a dividing line 602. (c) A view showing another example of the cross-sectional shape of a dividing line 602. (d) A view showing yet another example of the cross-sectional shape of a dividing line 602. [Figure 8] FIG. 10 is a schematic cross-sectional view of an injection molding apparatus according to a third embodiment. [Figure 9]10(a) is a schematic cross-sectional view of an injection molding apparatus according to embodiment 4. FIG. 10(b) is a perspective view of a resin molded product 90 according to embodiment 4, seen from the opposite side to the exterior surface. [Figure 10] 10(a) is a schematic cross-sectional view of an injection molding apparatus according to embodiment 5. FIG. 10(b) is a perspective view of a resin molded product 100 according to embodiment 5, seen from the side opposite to the exterior surface. [Figure 11] 10(a) is a schematic cross-sectional view of an injection molding apparatus according to embodiment 6. FIG. 10(b) is a perspective view of a resin molded product 110 according to embodiment 6, viewed from the opposite side to the exterior surface. [Figure 12] FIG. 11 is a perspective view of a resin molded product 120 according to a seventh embodiment, seen from the opposite side to the exterior surface. [Figure 13] 10A is a schematic cross-sectional view showing an X-direction cross section of an injection molding apparatus according to embodiment 7 in a gate valve closed state, and FIG. 10B is a schematic cross-sectional view showing a Y-direction cross section of an injection molding apparatus according to embodiment 7 in a gate valve closed state. [Figure 14] 10A is a schematic cross-sectional view showing an X-direction cross section of an injection molding apparatus according to embodiment 7 in a gate valve open state, and FIG. 10B is a schematic cross-sectional view showing a Y-direction cross section of an injection molding apparatus according to embodiment 7 in a gate valve open state. [Figure 15] 1A is a schematic cross-sectional view showing a gate valve of an injection molding apparatus according to a comparative example in a closed state, FIG. 1B is a schematic cross-sectional view showing a gate valve of an injection molding apparatus according to a comparative example in an open state, and FIG. 1C is a view showing a stage in which the resin has been filled into the cavity CAV and solidified in the comparative example. [Figure 16] FIG. 10 is a perspective view of a resin molded product according to a comparative example, viewed from the exterior surface OS side. [Figure 17] FIG. 1 is a perspective view of a printer that uses a resin molded product according to an embodiment as an exterior component. [Figure 18] (a) is a front view showing the main surface of the protrusion EX of the resin molded product according to embodiment 1. (b) is a side view of the protrusion EX of the resin molded product according to embodiment 1. (c) is a plan view of the protrusion EX of the resin molded product according to embodiment 1. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following describes embodiments of the present invention, including a resin molded product, a method for manufacturing a resin molded product, and a resin molding device, with reference to the drawings. Note that the following embodiments and examples are merely illustrative, and those skilled in the art can appropriately modify and implement the detailed configurations, for example, without departing from the spirit and scope of the present invention. In addition, in the drawings referred to in the following description of the embodiments, elements denoted by the same reference numerals have the same functions unless otherwise specified.

[0013] [Regarding the quality of resin molded products] First, the quality of a resin molded product will be described. When a resin molded product is injection molded, a gate mark (gate mark) from the gate used to inject molten resin into a cavity may be formed on the resin molded product. Improving the appearance quality of the surface of the resin molded product that does not have the gate mark is effective in improving the quality of the resin molded product. Therefore, in the following description, the surface of the resin molded product that does not have the gate mark will be described as the appearance surface whose quality should be improved, and the surface with the gate mark will be described as the non-appearance surface. However, the surface of the resin molded product that has the gate mark may be visible, and the appearance surface of the resin molded product whose quality should be improved may be a surface that is not visible to the user of a product that includes the resin molded product under normal usage conditions.

[0014] The inventors discovered that when a gate communicating with a hot runner is located in a cavity on the opposite side of the appearance surface of a resin molded product, a localized area with a different glossiness from the surrounding area may occur on the appearance surface, degrading the quality of the appearance surface. This localized area with a different glossiness is different from a flow mark (weld line), and the method described in Patent Document 1 could not prevent its occurrence.

[0015] Therefore, the inventors have thoroughly investigated methods for suppressing the occurrence of localized areas on the exterior surface that have a different glossiness from the surrounding area when injection molding is performed by placing a gate that communicates with a hot runner at a cavity position corresponding to the opposite side of the exterior surface of a resin molded product. Here, we will explain the phenomenon in which a local area that appears to have a different gloss (or color) from the surrounding area is formed on the exterior surface of a resin molded product. In the following explanation, for convenience, the local area that appears to have a different gloss (or color) will be referred to as a "different gloss area."

[0016] The differential gloss area is an area that exhibits a different appearance defect from the conventionally known flow marks (weld lines). The inventors discovered that the differential gloss area forms on the exterior surface of a resin molded product on the side opposite the hot runner gate, i.e., the side opposite the injection port through which the molten resin is injected into the cavity. Furthermore, when the condition of the differential gloss area and its surrounding exterior surface were compared, no significant difference was found in the material composition of the solidified resin. However, there were differences in the surface structure observed microscopically between the differential gloss area and its surrounding area, and it was found that this subtle difference in surface structure was visually recognized as a difference in gloss (or color). Furthermore, to investigate the cause of the subtle difference in surface structure, the surface condition of the mold transfer surface at the location where the differential gloss area occurs and the mold transfer surface around it was examined, and it was confirmed that there was no significant difference in the flatness (or surface roughness) of the two.

[0017] The inventors conducted extensive research focusing on the fact that regions of different gloss are formed at specific locations despite no significant difference in the surface flatness (or surface roughness) of the mold transfer surface. As a result, they discovered that the regions of different gloss are caused by differences in the transferability of the mold surface shape. Specifically, in the mold portion opposite the gate, the high-temperature molten resin immediately after being injected from the hot runner continues to flow from the start of injection of the molten resin until the entire cavity is completely filled, resulting in a relatively higher temperature than the surrounding mold surfaces. As a result, the mold surface opposite the gate has a higher transferability (fidelity) of the surface shape compared to the surrounding area, while the transferability (fidelity) of the surface shape is relatively lower on the surrounding mold surfaces, which are cooler. As a result, different microstructures are formed on the surface of the resin molded product between the regions of different gloss, where the flatness of the mold surface is transferred with high fidelity, and the surrounding area, where the transferability is relatively low.

[0018] Based on the above-mentioned findings, the inventors have invented a technology that can reduce the temperature distribution within the mold surface to which the exterior surface shape is transferred, thereby suppressing the occurrence of areas with a different gloss.A desirable embodiment of the manufacturing method is a manufacturing method that prevents the occurrence of areas where the temperature is equal to or higher than the glass transition point (Tg point) of the resin material on the mold surface to which the exterior surface shape is transferred, by devising a flow path shape for the molten resin in the gate bush.A desirable embodiment of the resin molded product is a resin molded product that has a convex portion on the side opposite the exterior surface, and in which a contact mark is formed on the convex portion where the tip of the valve pin that opens and closes the gate came into contact with a portion that does not include the central axis.

[0019] [Embodiment 1] FIG. 1 is a schematic cross-sectional view illustrating an injection-molded product manufacturing apparatus according to a first embodiment. The injection-molded product manufacturing apparatus is an injection molding apparatus 10 including an injection molding machine having an injection unit and a clamping unit, and a molding mold mounted on the clamping unit. The portion of the injection molding apparatus 10 corresponding to the molding mold is shown in FIG. 1. An apparatus that combines an injection molding machine and a molding mold can be called an injection-molded product manufacturing apparatus, as can an apparatus consisting of only an injection molding machine or only a molding mold. The injection molding apparatus 10, which serves as a molding mold, includes a resin nozzle 1, a valve pin 2, a gate bush 3, a movable mold 4, a fixed block 5, and a fixed block 6. The resin nozzle 1 is, for example, a cylindrical member made of metal, and serves as a supply path for supplying molten resin MR to a cavity CAV, which is connected to the gate bush 3. The cavity CAV, which defines the shape of the resin molded product, is formed by the movable mold 4, the fixed block 5, the fixed block 6, and the gate bush 3. The movable mold 4, fixed block 5, fixed block 6, and gate bush 3 can be made of a material such as pre-hardened steel. The cavity CAV includes a cavity portion CAV-EX whose shape is defined by the gate bush 3. Of the mold surfaces that define the cavity CAV, the mold surface OSM (second surface) of the movable mold 4 transfers and molds the exterior surface of the resin molded product. The mold surfaces ISM (first surface) of the fixed block 5, fixed block 6, gate bush 3, and the tip of the valve pin 2 transfer and mold the non-exterior surface opposite the exterior surface of the resin molded product.

[0020] The mold surface OSM of the movable mold 4, which transfers the exterior surface of the resin molded product, may be decorated to impart a beautiful appearance to the resin molded product. Adding a decorative aesthetic includes transferring and forming, for example, a grained (uneven pattern) or a mirrored finish on the exterior surface of the resin molded product. Specifically, the mold surface OSM may have an area to transfer an uneven pattern such as a matte finish, matte finish, hairline finish, lattice pattern, wood grain, or leather pattern, or a mirrored finish. By combining such a mold with an appropriate resin material and performing injection molding, it is possible to form an exterior surface of a resin molded product with a piano black, metallic, marbled finish, or other finish.

[0021] The parts other than the valve pin 2 (fixed pieces 5, 6 and gate bush 3) that are used to transfer mold the non-exterior surface are collectively referred to as the fixed mold or non-exterior surface forming mold (first mold). The part that is used to transfer mold the exterior surface (movable mold 4) is collectively referred to as the exterior surface forming mold (second mold). Here, the non-exterior surface forming mold (fixed mold) is made up of multiple parts (fixed pieces 5, 6 and gate bush 3), but it can also be made up of a single part. Here, the exterior surface forming mold is made up of a single part (movable mold 4), but it can also be made up of multiple parts.

[0022] Cold runner molds and hot runner molds are known as molding dies for injection molding thermoplastic resins such as plastics. Cold runner molds have the advantage of being simple in structure, but the resin that solidifies in the runner section becomes waste. Therefore, from the perspectives of improving economic efficiency and reducing environmental impact, it is desirable to use hot runner molds, which produce less waste resin. By using a hot runner mold, whose runner section is entirely heated, it is possible to produce resin molded products with almost no waste resin. This embodiment is particularly suitable for producing resin molded products using a hot runner mold, where the resin temperature near the gate tends to be high.

[0023] In a first example, the molding mold in the injection molding apparatus 10 is a hot runner mold, and the resin nozzle 1 is a hot runner nozzle in the hot runner mold. The gate bush 3 may also serve as a hot runner bush in the hot runner mold. In a second example, the molding mold in the injection molding apparatus 10 is a cold runner mold, and the resin nozzle 1 is an injection nozzle in the injection unit of the injection molding machine. The gate bush 3 may also serve as a sprue bush in the cold runner mold.

[0024] The valve pin 2 can move up and down within the resin nozzle 1 in the vertical direction in the figure, opening and closing the flow path of the molten resin from the resin nozzle 1 to the cavity CAV. When the valve pin 2 opens and closes the flow path, the direction in which the valve pin 2 moves up and down (vertical direction in the figure) is referred to as the "moving and retracting direction" or "predetermined direction." When the valve pin 2 moves up and retracts into the resin nozzle 1, the molten resin MR is injected from the resin nozzle 1 into the cavity CAV, and the hot runner gate is opened. As shown in FIG. 1 , when the valve pin 2 moves down and advances and hits the gate bush 3, the flow path of the molten resin MR from the resin nozzle 1 to the cavity CAV is closed and the gate is closed. In this embodiment, the tip of the valve pin 2 has a cylindrical shape with a circular cross section perpendicular to its axis. Note that the tip of the valve pin 2 may refer to the portion of the valve pin 2 that protrudes beyond the tip of the resin nozzle 1 when the valve pin 2 advances, i.e., the portion that is positioned outside the resin nozzle 1 when the valve pin 2 advances. The tip surface of the valve pin 2 is the surface of the tip of the valve pin 2, including the very tip of the valve pin 2. The very tip of the valve pin 2 is a point, a line or a surface, and in this example is a circular surface.

[0025] 1 is a schematic diagram, and the various parts of the apparatus are not necessarily shown to scale. Furthermore, the configuration of the injection molding apparatus 10 of the embodiment is not limited to the example shown in Fig. 1. For example, the movable and fixed molds may be configured with multiple detachable pieces, or an ejector pin may be provided for releasing the solidified resin molded product.

[0026] Next, we will explain a manufacturing method for manufacturing a resin molded product using the injection molding apparatus 10. Figures 2(a) to 2(b) and 3(a) to 3(b) are schematic cross-sectional views for explaining each step of the manufacturing method, and show an enlarged view of the vicinity of the gate bush 3 of the injection molding apparatus 10.

[0027] FIG. 2(a) shows a state (gate closed state) in which, prior to the start of injection molding, the valve pin 2 moves downward and abuts against the gate bush 3, blocking the flow path of the molten resin MR from the resin nozzle 1 to the cavity CAV. In the injection molding apparatus of this embodiment, a portion 3S of the gate bush 3 is located on an extension of the direction in which the valve pin 2 moves back and forth. Therefore, the portion 3S of the gate bush 3, which is part of the exterior surface forming mold (movable mold 4), is located between the tip surface of the valve pin 2 and the exterior surface forming mold (movable mold 4) in the direction in which the valve pin 2 moves back and forth. More specifically, the portion 3S of the gate bush 3 is located on an extension of the central axis CX. Since the central axis CX of the valve pin 2 coincides with the central axis of the resin nozzle 1, it can also be said that the portion 3S of the gate bush 3 is located on an extension of the central axis of the resin nozzle 1. Therefore, in the gate closed state, the portion of the tip of the valve pin 2 through which the central axis passes abuts against the portion 3S of the gate bush 3, and the portion through which the central axis passes is not exposed to the space of the cavity CAV. When the flow path of the molten resin MR is closed, the distance from the tip surface of the valve pin 2 to the outer surface forming mold (second mold) is 2.5 mm or more and 15 mm or less.

[0028] Next, Figure 2(b) shows the initial stage when the valve pin 2 retracts into the resin nozzle 1 and separates from the gate bush 3, and the molten resin MR begins to be injected from the resin nozzle 1 into the cavity CAV (gate open state). The molten resin MR is injected from the resin nozzle 1 into the flow path within the gate bush 3, but the portion 3S of the gate bush 3 is located on an extension of the central axis CX of the valve pin 2. Therefore, the molten resin MR cannot travel the shortest distance from the outlet of the resin nozzle 1 to the mold surface OSM. Instead, the flow direction is changed by the portion 3S and it flows into the cavity portion CAV-EX. The molten resin MR follows a curved flow path by passing through the cavity portion CAV-EX, and during this time, heat is absorbed by the gate bush 3, causing its temperature to drop below that when it was stored in the resin nozzle 1. In other words, after the temperature of the molten resin MR drops, it reaches the mold surface OSM (molding surface), which transfers the appearance of the resin molded product.

[0029] Next, Figure 3(a) shows the stage where the molten resin MR continues to be injected from the resin nozzle 1 into the cavity CAV. In this embodiment, the molten resin MR is configured to pass through the cavity portion CAV-EX, where its temperature is reduced, before reaching the mold surface OSM. Therefore, the temperature of the mold surface OSM, which transfers the appearance surface of the resin molded product, is maintained below the glass transition point (Tg point) of the resin material, even in the region HA closest to the gate exit. It goes without saying that the temperature of the mold surface OSM excluding the region HA is maintained below the glass transition point (Tg point).

[0030] Next, Figure 3(b) shows the state in which the resin filling of the cavity CAV is complete, the valve pin 2 moves downward, abutting against the gate bush 3 and closing the flow path (gate closed state). When the flow path of the molten resin MR is closed, the distance from the tip of the valve pin 2 to the exterior surface forming mold (second mold) is 2.5 mm or more and 15 mm or less. The molten resin filling the cavity CAV is cooled and solidified by the mold, becoming solidified resin SR. However, as mentioned above, the temperature of the mold surface OSM, which transfers the exterior surface of the resin molded product, is kept below the glass transition point of the resin material. Therefore, there is no significant difference in the surface shape transferability (transfer fidelity) between the area HA closest to the gate exit and its surroundings on the mold surface OSM, and there is almost no difference in the flatness (or surface roughness) of the solidified resin SR surface.

[0031] In this embodiment, at least two techniques are employed to maintain the temperature of region HA below the glass transition point (Tg) of the resin material. As a first technique, a portion 3S of the gate bush 3 is provided to prevent high-temperature (e.g., above the glass transition point) resin in the resin nozzle 1 from reaching the mold surface OSM in the shortest distance from directly below the resin nozzle 1 (directly below the valve pin 2). As a second technique, the molten resin MR passes through the cavity portion CAV-EX, thereby lowering the temperature of the molten resin through a curved flow path. However, techniques for maintaining the temperature of region HA below the glass transition point (Tg) of the resin material are not limited to these first and second techniques. For example, a technique can be employed in which the resin temperature in the resin nozzle 1 is kept low enough to maintain the temperature of region HA below the glass transition point (Tg) of the resin material. Alternatively, a temperature maintenance mechanism (cooling mechanism) can be provided in the exterior surface forming mold (movable mold 4) to suppress temperature increases in region HA.

[0032] When the resin in the cavity CAV is hardened, the movable mold 4 is moved downward in the drawing to open the cavity. Furthermore, an ejector pin (not shown) is used to push out the solidified resin SR (resin molded product) that is in close contact with the fixed piece 5, the fixed piece 6, the gate bush 3, and the valve pin 2 downward, and release it from the mold. A resin molded product is formed by the above series of steps, and by repeating the same steps, a large number of resin molded products can be mass-produced.

[0033] Figures 4(a) and 4(b) illustrate a resin molded product 40 according to this embodiment, with Figure 4(a) being a perspective view of the resin molded product 40 seen from the side opposite to the exterior surface, and Figure 4(b) being a perspective view of the resin molded product 40 seen from the exterior surface side. Note that Figures 1, 2(a) to 2(b), and 3(a) to 3(b), which have been described above, correspond to cross-sectional views taken along the A-A' plane in Figure 4(a).

[0034] The resin molded product 40 according to this embodiment has an appearance surface OS that is visible to the user when the resin molded product 40 is mounted on a product, and a non-appearance surface IS that is invisible to the user. The appearance surface OS is the surface to which the mold surface OSM of the movable mold 4 is transferred, and is formed on the opposite side of the non-appearance surface IS to which the mold surface ISM is transferred. A protrusion EX formed by the cavity portion CAV-EX is formed on the non-appearance surface IS side. A gate mark 41 is formed at the tip of the protrusion EX.

[0035] FIG. 5 shows an enlarged perspective view of the vicinity of the protrusion EX. The gate mark 41 includes a dividing line 53 (boundary mark) formed at the boundary between the valve pin 2 and the gate bush 3 (FIG. 3(b)). The gate mark 41 also includes a first surface 51 onto which the shape of the tip surface of the valve pin 2 is transferred, and a second surface 52 onto which a sliding mark from sliding against the side surface of the valve pin 2 remains when the valve pin 2 is released from the mold. As can be easily seen from FIG. 3(b), the shape of the portion of the tip surface of the valve pin 2 through which the central axis CX of the valve pin 2 passes is not transferred to the first surface 51. In this way, the resin molded product 40 of this embodiment has a protrusion EX on which a molding mark formed by a portion of the tip of the valve pin that opens and closes the gate that does not include the central axis, in other words, a contact mark formed from contact with the portion that does not include the central axis, is formed.

[0036] In the resin molded product 40 of this embodiment, which has a convex portion EX of such a configuration on the non-exterior surface IS opposite the exterior surface OS, the formation of local areas on the exterior surface OS that appear to have a different gloss (or color) from the surrounding area is suppressed, resulting in the formation of a high-quality exterior surface.

[0037] Referring to FIGS. 18(a) to 18(c), the specific form of the convex portion EX will be described. FIG. 18(a) is a front view in which the main surface of the convex portion EX can be seen, FIG. 18(b) is a side view, and FIG. 18(c) is a plan view. In order to suppress the formation of local regions on the outer surface OS of the resin molded product that are visually recognized with different glossiness (or color), it is preferable that the convex portion EX has the following dimensions. L is 2.5 mm or more and 20 mm or less, H is 2 mm or more and 10 mm or less, h is 2 mm or more and 10 mm or less, T is 0.5 mm or more and 5 mm or less, Wa and Wb are 1 mm or more and 5 mm or less, and the radius r of the valve pin is 0.5 mm or more and 5 mm or less. Further, the distance g between the parting line 53 formed at the boundary between the valve pin 2 and the gate bushing 3 (see FIG. 3(b)) and the edge mark of the valve pin 2 is 0.5 mm or more and 5 mm or less. The height a of the second surface 52 where a sliding mark remains after sliding on the side surface of the valve pin 2 during mold release is 1 mm or more and 8 mm or less. Also, the angle α is 45 degrees or more and 90 degrees or less, and the angle β is 0 degrees or more and 45 degrees or less. Within the above numerical ranges, the magnitude relationship between Wa and Wb and the magnitude relationship between H and h are arbitrary. For example, the convex portion EX can be formed into a polyhedron shape composed of a plurality of planes, but it is desirable to satisfy Wb ≤ 2 × Wa. In this embodiment, since the shape of the portion of the tip surface of the valve pin 2 through which the central axis CX of the valve pin 2 passes is not transferred to the resin molded product, the relationships a < H and g < r hold. In addition, β ≤ α, Wb ≤ 2 × r, h ≤ H, Wa ≤ Wb, Wb ≤ L, T ≤ H, etc. may hold. Note that the equal sign does not necessarily hold for these relationships.

[0038] FIG. 17 is a perspective view of a printer using the resin molded product 40 of this embodiment as an exterior component. In FIG. 17, 170 is a composite printer, and the original document cover 712 and the housing 710 are molded from, for example, black or white resin. Since the upper surface and side surfaces of the printer are places that come into contact with the user's eyes as the outer surface, it is required that there are no local regions with a particularly strange glossiness (or color), and the resin molded product 40 of this embodiment is preferably used.

[0039] [Embodiment 2] FIG. 6 is a schematic cross-sectional view illustrating an injection molding apparatus according to embodiment 2, corresponding to FIG. 3(b) in the description of embodiment 1. Regarding this embodiment, the description of matters common to embodiment 1 will be simplified or omitted. In this embodiment, too, portion 63S, which is part of gate bush 63, is disposed on an extension of the central axis CX of valve pin 2. Because the central axis CX of valve pin 2 coincides with the central axis of resin nozzle 1, portion 63S of gate bush 63 can also be said to be disposed on an extension of the central axis of resin nozzle 1. The tip of valve pin 2 in this embodiment has a prismatic shape with a rectangular cross section perpendicular to the axis. When the width of the tip of valve pin 2 is D and the width of portion 63S is d, D = d is set, excluding error.

[0040] In this embodiment, too, the molten resin cannot travel the shortest distance from the outlet of the resin nozzle 1 to the mold surface OSM. Instead, its flow direction is changed by the portion 63S and it flows into the cavity portion CAV-EX60. By passing through the cavity portion CAV-EX60, the molten resin follows a curved flow path, during which heat is absorbed by the gate bush 63, causing the temperature to drop below that when the molten resin was stored in the resin nozzle 1. That is, after the temperature of the molten resin drops, it reaches the mold surface OSM, onto which the exterior surface of the resin molded product is transferred. Therefore, the temperature of the mold surface OSM, onto which the exterior surface of the resin molded product is transferred, is maintained below the glass transition point (Tg point) of the resin material, even in the region HA closest to the gate outlet.

[0041] FIG. 7(a) illustrates a resin molded product 70 according to this embodiment. It is a perspective view of the resin molded product 70 as viewed from the non-exterior surface IS, opposite the exterior surface. A protrusion EX70 formed by the cavity portion CAV-EX60 is formed on the non-exterior surface IS. A gate mark is formed at the tip of the protrusion EX70. The gate mark includes a dividing line 602 formed at the boundary between the valve pin 2 and the gate bush 63 (see FIG. 6) and a surface where a sliding mark 72 remains due to sliding with the side surface of the valve pin 2 during mold release. In the explanation of FIG. 6, it was stated that D = d, excluding errors. However, even if D and d are identical, if a small gap exists at the contact point between the valve pin 2 and the portion 63S, the cross-sectional shape of the dividing line 602 may be the shape illustrated in FIG. 7(b). Furthermore, if there is an error between D and d, the cross-sectional shape of the dividing line 602 may be the shape illustrated in FIG. 7(c) or FIG. 7(d). As described above, the resin molded product 70 of this embodiment has the protrusions EX70 on which contact marks are formed from contact with the valve pin that opens and closes the gate.

[0042] In the resin molded product 70 of this embodiment, which has a convex portion EX70 of such a configuration on the non-exterior surface IS opposite the exterior surface OS, the formation of local areas on the exterior surface OS that appear to have a different gloss (or color) from the surrounding area is suppressed, resulting in the formation of a high-quality exterior surface.

[0043] [Embodiment 3] 8 is a schematic cross-sectional view illustrating an injection molding apparatus according to embodiment 3, and corresponds to FIG. 3(b) in the description of embodiment 1. Regarding this embodiment, the description of matters common to embodiment 1 will be simplified or omitted. In this embodiment as well, portion 83S of gate bush 83 is disposed on an extension of the central axis CX of valve pin 2. Since the central axis CX of valve pin 2 coincides with the central axis of resin nozzle 1, it can also be said that portion 83S of gate bush 83 is disposed on an extension of the central axis of resin nozzle 1.

[0044] In this embodiment as well, the molten resin cannot travel the shortest distance from the outlet of the resin nozzle 1 to the mold surface OSM, but its flow direction is changed by the portion 83S and it flows into the cavity portion CAV-EX80.

[0045] The molten resin travels a curved path through the cavity portion CAV-EX80, during which heat is absorbed by the gate bush 83, resulting in a temperature drop below that when the resin was stored in the resin nozzle 1. In this embodiment, the cavity portion CAV-EX80 is defined by a curved surface SL, which provides a large contact area between the molten resin and the gate bush 83. This effectively reduces the temperature of the molten resin before it reaches the mold surface OSM, which transfers the exterior surface of the resin molded product. Therefore, the temperature of the mold surface OSM, which transfers the exterior surface of the resin molded product, is kept below the glass transition point (Tg point) of the resin material, even in the region HA closest to the gate exit. Therefore, there is no significant difference in the surface shape transferability (transfer fidelity) between the region HA closest to the gate exit and its surroundings on the mold surface OSM, and there is almost no difference in the flatness (or surface roughness) of the solidified resin SR surface.

[0046] The resin molded product according to this embodiment also has a convex portion formed by the cavity portion CAV-EX80 on the non-appearance surface side, and a gate mark is formed at the tip of the convex portion. In the resin molded product according to this embodiment, which has a convex portion of this configuration on the non-appearance surface IS opposite the appearance surface OS, the formation of a local area on the appearance surface OS that is visually perceived as having a different gloss (or color) from the surrounding area is suppressed, and a high-quality appearance surface is formed.

[0047] [Embodiment 4] FIG. 9(a) is a schematic cross-sectional view illustrating an injection molding apparatus according to embodiment 4, and corresponds to FIG. 3(b) in the description of embodiment 1. Regarding this embodiment, the description of matters common to embodiment 1 will be simplified or omitted. In this embodiment, too, a portion 93S, which is part of the gate bush 93, is disposed on an extension of the central axis CX of the valve pin 2. Since the central axis CX of the valve pin 2 coincides with the central axis of the resin nozzle 1, it can also be said that the portion 93S of the gate bush 93 is disposed on an extension of the central axis of the resin nozzle 1. The tip of the valve pin 2 in this embodiment has a cylindrical shape whose cross section in a direction perpendicular to the axis is circular.

[0048] In this embodiment, the molten resin cannot travel the shortest distance from the outlet of the resin nozzle 1 to the mold surface OSM, but instead its flow direction is changed by the portion 93S and it flows into the cavity portion CAV-EX90. In this embodiment, the cavity portion CAV-EX90 is configured in a substantially rectangular parallelepiped shape.

[0049] The molten resin travels a curved path through the cavity portion CAV-EX90, and during this time, heat is removed by the gate bushing 93, causing the temperature to drop below that when it was stored in the resin nozzle 1. In other words, after the temperature of the molten resin drops, it reaches the mold surface OSM, which transfers the exterior surface of the resin molded product. For this reason, the temperature of the mold surface OSM, which transfers the exterior surface of the resin molded product, is kept below the glass transition point (Tg point) of the resin material, even in the area HA closest to the gate exit. Therefore, on the mold surface OSM, there is no significant difference in the transferability of the surface shape (transfer fidelity) between the area HA closest to the gate exit and its surrounding area, and there is almost no difference in the flatness (or surface roughness) of the solidified resin SR surface.

[0050] FIG. 9(b) illustrates a resin molded product 90 according to this embodiment, showing a perspective view of the resin molded product 90 from the non-exterior surface IS, opposite the exterior surface. A rib-shaped protrusion EX90 formed by the cavity portion CAV-EX90 is formed on the non-exterior surface IS. A gate mark is formed at the tip of the protrusion EX90. The gate mark includes a dividing line 930 formed at the interface between the valve pin 2 and the gate bush 93, a surface 910 onto which the shape of the tip surface of the valve pin 2 is transferred, and a surface bearing a sliding mark 920 from sliding against the side surface of the valve pin 2 during mold release. Thus, the resin molded product 90 of this embodiment includes a protrusion EX90 bearing a contact mark formed from contact with the valve pin that opens and closes the gate.

[0051] In the resin molded product 90 of this embodiment, which has a convex portion EX90 of such a configuration on the non-exterior surface IS opposite the exterior surface OS, the formation of local areas on the exterior surface OS that appear to have a different gloss (or color) from the surrounding area is suppressed, resulting in the formation of a high-quality exterior surface.

[0052] [Embodiment 5] FIG. 10(a) is a schematic cross-sectional view illustrating an injection molding apparatus according to embodiment 5, and corresponds to FIG. 3(b) in the description of embodiment 1. Regarding this embodiment, the description of matters common to embodiment 1 will be simplified or omitted. In this embodiment, too, a portion 103S, which is part of the gate bush 103, is disposed on an extension of the central axis CX of the valve pin 2. Since the central axis CX of the valve pin 2 coincides with the central axis of the resin nozzle 1, it can also be said that the portion 103S of the gate bush 103 is disposed on an extension of the central axis of the resin nozzle 1. The tip of the valve pin 2 in this embodiment has a cylindrical shape whose cross section in a direction perpendicular to the axis is circular.

[0053] In this embodiment, the molten resin cannot travel the shortest distance from the outlet of the resin nozzle 1 to the mold surface OSM, but instead its flow direction is changed by the portion 103S and it flows into the cavity portion CAV-EX100. In this embodiment, the cavity portion CAV-EX100 is configured to have a substantially cylindrical shape.

[0054] The molten resin travels a curved path through the cavity portion CAV-EX100, and during this time, heat is absorbed by the gate bush 103, causing the temperature to drop below that when it was stored in the resin nozzle 1. In other words, after the temperature of the molten resin drops, it reaches the mold surface OSM, which transfers the exterior surface of the resin molded product. Therefore, the temperature of the mold surface OSM, which transfers the exterior surface of the resin molded product, is kept below the glass transition point (Tg point) of the resin material, even in the area HA closest to the gate exit. Therefore, on the mold surface OSM, there is no significant difference in the transferability of the surface shape (transfer fidelity) between the area HA closest to the gate exit and its surrounding area, and there is almost no difference in the flatness (or surface roughness) of the solidified resin SR surface.

[0055] FIG. 10(b) illustrates a resin molded product 100 according to this embodiment, showing a perspective view of the resin molded product 100 from the non-exterior surface IS, opposite the exterior surface. A boss-shaped (cylindrical) protrusion EX100 formed by the cavity portion CAV-EX100 is formed on the non-exterior surface IS. The boss-shaped (cylindrical) protrusion EX100 preferably has an inner diameter of 3 mm to 5 mm and an outer diameter of 6 mm to 10 mm. A gate mark 101 is formed on the tip (edge of the cylinder) of the protrusion EX100. The gate mark 101 includes a dividing line 140 formed at the boundary between the valve pin 2 and the gate bush 93 and a surface bearing a sliding mark 150 formed by sliding against the side surface of the valve pin 2 during mold release. Thus, the resin molded product 100 of this embodiment includes a protrusion EX100 bearing a contact mark formed by contact with the valve pin that opens and closes the gate.

[0056] In the resin molded product 100 of this embodiment, which has a convex portion EX100 of such a configuration on the non-exterior surface IS opposite the exterior surface OS, the formation of local areas on the exterior surface OS that appear to have a different gloss (or color) from the surrounding area is suppressed, resulting in the formation of a high-quality exterior surface.

[0057] [Embodiment 6] FIG. 11(a) is a schematic cross-sectional view illustrating an injection molding apparatus according to embodiment 6, and corresponds to FIG. 3(b) in the description of embodiment 1. Regarding this embodiment, the description of matters common to embodiment 1 will be simplified or omitted. In this embodiment as well, portion 113S, which is part of gate bush 113, is disposed on an extension of the central axis CX of valve pin 2. Because the central axis CX of valve pin 2 coincides with the central axis of resin nozzle 1, it can also be said that portion 113S of gate bush 113 is disposed on an extension of the central axis of resin nozzle 1.

[0058] In this embodiment, too, the molten resin cannot travel the shortest distance from the outlet of the resin nozzle 1 to the mold surface OSM, but instead its flow direction is changed by the portion 113S and it flows into the cavity portion CAV-EX110. In this embodiment, the tip of the valve pin 2 is curved rather than flat, and the gate is closed when it comes into contact with the concave curved surface of the portion 113S. Furthermore, the surface (tip surface) of the cavity portion CAV-EX110 defined by the tip of the valve pin 2 is curved. The tip of the valve pin 2 can be a point.

[0059] The molten resin travels a curved path through the cavity portion CAV-EX110, and during this time, heat is removed by the gate bush 113, causing the temperature to drop below that when it was stored in the resin nozzle 1. In other words, after the temperature of the molten resin drops, it reaches the mold surface OSM, which transfers the exterior surface of the resin molded product. For this reason, the temperature of the mold surface OSM, which transfers the exterior surface of the resin molded product, is kept below the glass transition point (Tg point) of the resin material, even in the area HA closest to the gate exit. Therefore, on the mold surface OSM, there is no significant difference in the transferability of the surface shape (transfer fidelity) between the area HA closest to the gate exit and its surrounding area, and there is almost no difference in the flatness (or surface roughness) of the solidified resin SR surface.

[0060] FIG. 11(b) illustrates a resin molded product 110 according to this embodiment, and is a perspective view of the resin molded product 110 as viewed from the non-exterior surface IS, which is opposite the exterior surface. A protrusion EX110 formed by a cavity portion CAV-EX110 is formed on the non-exterior surface IS side. A gate mark 111 is formed at the tip of the protrusion EX110. The gate mark 111 includes a secant line 133 formed at the boundary between the valve pin 2 and the gate bush 93 and a surface 130 onto which the curved surface of the valve pin 2 is transferred. In this way, the resin molded product 110 of this embodiment includes a protrusion EX110 on which a contact mark is formed, which was formed when the valve pin that opened and closed the gate was in contact with the valve pin.

[0061] In the resin molded product 110 of this embodiment, which has a convex portion EX110 of such a configuration on the non-exterior surface IS opposite the exterior surface OS, the formation of local areas on the exterior surface OS that appear to have a different gloss (or color) from the surrounding area is suppressed, resulting in the formation of a high-quality exterior surface.

[0062] [Embodiment 7] FIG. 12 illustrates a resin molded product 120 according to the seventh embodiment, and is a perspective view of the resin molded product 120 as viewed from the non-exterior surface IS, opposite the exterior surface. FIGS. 13(a) and 13(b) are schematic cross-sectional views illustrating an injection molding apparatus according to the seventh embodiment, showing the gate valve in a closed state. FIG. 13(a) shows a cross-section along the X direction in FIG. 12, and FIG. 13(b) shows a cross-section along the Y direction in FIG. 12. FIGS. 14(a) and 14(b) are schematic cross-sectional views illustrating an injection molding apparatus according to the seventh embodiment, showing the gate valve in an open state. FIG. 14(a) shows a cross-section along the X direction in FIG. 12, and FIG. 14(b) shows a cross-section along the Y direction in FIG. 12. Regarding matters common to the first embodiment, descriptions of this embodiment will be simplified or omitted.

[0063] In this embodiment as well, portion 203S, which is a part of gate bush 203, is located on an extension of the central axis CX of valve pin 2. Because the central axis CX of valve pin 2 coincides with the central axis of resin nozzle 1, it can also be said that portion 203S of gate bush 203 is located on an extension of the central axis of resin nozzle 1. The tip of valve pin 2 in this embodiment has a prismatic shape with a rectangular cross section in a direction perpendicular to the axis.

[0064] In this embodiment, the molten resin cannot travel the shortest distance from the resin nozzle 1 to the mold surface OSM, and the flow direction is changed by the portion 203S. Specifically, the molten resin is diverted toward the cavity portion CAV-EX120A and the cavity portion CAV-EX120B. It is preferable that the cavity portion CAV-EX120A and the cavity portion CAV-EX120B are arranged symmetrically with respect to the central axis CX of the valve pin 2.

[0065] The molten resin travels a curved path by passing through cavity portion CAV-EX120A or cavity portion CAV-EX120B. During this time, heat is absorbed by the gate bush 203, causing the temperature to drop below that when the resin was stored in the resin nozzle 1. That is, after the temperature of the molten resin drops, it reaches the mold surface OSM, which transfers the exterior surface of the resin molded product. Therefore, the temperature of the mold surface OSM, which transfers the exterior surface of the resin molded product, is kept below the glass transition point (Tg point) of the resin material, even in the area HA closest to the gate exit. Therefore, on the mold surface OSM, there is no significant difference in the transferability (fidelity of transfer) of the surface of the solidified resin SR between the area HA closest to the gate exit and its surroundings. Furthermore, there is almost no difference in the flatness (or surface roughness) of the solidified resin SR surface.

[0066] As shown in FIG. 12, on the non-exterior surface IS side of the resin molded product 120, a convex portion EX120A formed by the cavity portion CAV-EX120A and a convex portion EX120B formed by the cavity portion CAV-EX120B are formed.

[0067] A gate mark 121 is formed at the tip of each of the protrusions EX120A and EX120B. The gate mark 121 includes a dividing line formed at the boundary between the valve pin 2 and the gate bush 203, a surface onto which the shape of the tip surface of the valve pin 2 is transferred, and a surface on which a sliding mark from sliding against the side surface of the valve pin 2 remains when the mold is released. In this way, the resin molded product 120 of this embodiment includes the protrusions EX120A and EX120B on which a contact mark from contact with the valve pin that opens and closes the gate is formed.

[0068] In the resin molded product 120 of this embodiment, which has the convex portions EX120A and EX120B configured as described above on the non-exterior surface IS opposite the exterior surface OS, the formation of a local area on the exterior surface OS that is visually perceived as having a different gloss (or color) from the surrounding area is suppressed. In other words, the resin molded product 120 of this embodiment has a high-quality exterior surface. [Example]

[0069] The following describes specific examples and comparative examples. In each example and comparative example, resin molded products with the same external shape were produced by injection molding. All resin molded products were produced using an injection molding machine with the same basic configuration, but the valve pins and gate bushes corresponding to each example and comparative example were installed in the injection molding machine.

[0070] The examples and comparative examples have the following in common: A resin molded product for use in the exterior of the multifunction printer shown in Figure 17 was produced using PS (polystyrene) with a glass transition temperature (Tg point) of 90°C as the resin material. The resin molded product was a plate-shaped member with a thickness of 0.5 mm or more and 5 mm or less, and was molded by injecting the resin material from the non-exterior surface behind a position that would be approximately the center when the exterior surface was viewed in plan. In other words, the gate mark was located on the non-exterior surface behind a position that would be approximately the center when the exterior surface of the resin molded product was viewed in plan.

[0071] The molding conditions were as follows: The temperature of the hot runner of the injection molding machine was set to 230°C, and the temperature of the molten resin in the hot runner was adjusted to 230°C. The temperature setting of the mold temperature adjustment mechanism was set to 60°C, the filling time into the cavity was 2 seconds, and the cooling time after closing the gate was 10 seconds. The injection rate (volume flow rate) of the molten resin injected from the hot runner into the cavity was, for example, 20 to 450 cm 3 / second range.

[0072] [Example 1] The first embodiment was carried out under the molding conditions described above. The width of the tip surface of the valve pin in the direction perpendicular to the central axis is d, and the width of the portion 3S of the gate bush 3 is D, and the ratio d / D was set to 0.75. In the resin molded product of this example, the formation of a localized area in the appearance surface OS that appears to have a different gloss (or color) from the surrounding area was suppressed, and a high-quality appearance surface was formed.

[0073] [Example 2] Embodiment 2 was carried out under the molding conditions described above. When the width of the tip surface of the valve pin in the direction perpendicular to the central axis is D and the width of the portion 63S of the gate bush 3 is d, d / D was set to 0.75. In the resin molded product of this example, the formation of a localized area in the appearance surface OS that appears to have a different gloss (or color) from the surrounding area was suppressed, and a high-quality appearance surface was formed.

[0074] [Example 3] Embodiment 3 was carried out under the molding conditions described above. When the width of the tip surface of the valve pin in the direction perpendicular to the central axis is d and the width of the portion 83S of the gate bush 3 is D, d / D was set to 0.75. In the resin molded product of this example, the formation of a localized area in the appearance surface OS that is visually perceived as having a different gloss (or color) from the surrounding area was suppressed, and a high-quality appearance surface was formed.

[0075] [Example 4] Embodiment 4 was carried out under the molding conditions described above. When the width of the tip surface of the valve pin in the direction perpendicular to the central axis is d and the width of the portion 93S of the gate bush 3 is D, d / D was set to 0.9. In the resin molded product of this example, the formation of a localized area in the appearance surface OS that is visually perceived as having a different gloss (or color) from the surrounding area was suppressed, and a high-quality appearance surface was formed.

[0076] [Comparative Example] 15(a) to 15(c) are schematic cross-sectional views illustrating an injection molding apparatus according to a comparative example. FIG. 15(a) shows a state in which, before injection molding begins, the valve pin 152 has moved downward to close the flow path of the molten resin MR from the resin nozzle 1 to the cavity CAV (gate closed state). In the injection molding apparatus of the comparative example, the tip surface of the valve pin 2, including the portion through which the central axis CX passes, is exposed to the space of the cavity CAV. That is, in the comparative example, the gate bush 153 is not positioned on an extension of the central axis CX of the valve pin 2.

[0077] In the comparative example, when the valve pin 152 moves upward to open the flow path from the resin nozzle 1 to the cavity, the molten resin MR can travel the shortest distance from the gate opening toward the mold surface OSM without bending, as shown in Figure 15(b). Therefore, the molten resin flows into the cavity without decreasing in temperature much compared to when it was stored in the resin nozzle 1. In the mold surface OSM, a region 155 close to the gate opening continues to be exposed to the flow of molten resin injected at a locally high temperature from the start of injection of the molten resin until filling is complete. For this reason, even if the mold is equipped with a temperature adjustment mechanism, the temperature of the region 155 closest to the gate exit of the mold surface OSM, which transfers the exterior surface of the resin molded product, reaches or exceeds the glass transition point (Tg point) of the resin material.

[0078] 15(c), when the gate is closed and the resin in the cavity is solidified, there is a large difference in the transferability (fidelity of transfer) of the surface shape of the mold surface OSM between the region 162 closest to the gate exit and its surroundings on the mold surface OSM. As a result, there is a large difference in the surface flatness (or surface roughness) between the region 162 of the solidified resin SR and its surroundings.

[0079] 16 illustrates a resin molded product 160 of a comparative example, and is a perspective view of the resin molded product 160 as viewed from the side of the exterior surface OS. Gate marks 161 are formed on the side of the non-exterior surface IS. In the comparative example, an area 162 of the exterior surface OS has a large difference in surface flatness (or surface roughness) compared to its surroundings, and therefore appears to have a different gloss (or color), resulting in a resin molded product with low exterior quality.

[0080] As described above, in the resin molded products of Examples 1 to 5, the formation of localized areas in the appearance surface OS that are visually perceived as having a different gloss (or color) from the surrounding area was suppressed, and a high-quality appearance surface was formed. In contrast, in the resin molded product of the comparative example, an area with a different gloss (or color) from the surrounding area appeared on the appearance surface opposite the position where the gate mark 161 was formed, and a low-quality appearance surface was formed.

[0081] [Other embodiments] The present invention is not limited to the above-described embodiments and examples, and many modifications are possible within the technical concept of the present invention. For example, the resin molded product may be provided with one or two protrusions as in the above-described embodiment, or may be provided with three or more protrusions. Alternatively, an existing injection molding machine may be used and only the molding die portion may be replaced, or an existing molding die may be used and only the gate bush may be replaced.

[0082] Resin molded products embodying the present invention can be used for the exterior of various devices, including electrical devices and mechanical devices, as well as the multifunction printer illustrated in FIG. 17. These devices include functional components (electrical components and mechanical components) that realize the device's functions, and exterior components that cover the functional components. Examples of such devices include video equipment, audio equipment, office equipment, medical equipment, industrial equipment, transportation equipment, and analytical equipment. The exterior components cover the functional components so that the non-exterior surface is positioned between the exterior surface and the functional components. Using a resin molded product embodying the present invention for an exterior component can improve the quality of the device's appearance. [Explanation of symbols]

[0083] 1. Resin nozzle / 2. Valve pin / 3. Gate bush / 3S. Gate bush part / 4. Movable mold / 5. Fixed block / 6. Fixed block / 10. Injection molding machine / 40. Resin molded product / 41. Gate mark / 51. First surface on which the shape of the tip of the valve pin 2 is transferred / 52. Second surface on which the sliding mark from the side of the valve pin 2 sliding against it when demolded remains / 53. Secant line / 63. Gate bush / 63S. Gate bush part / 93. Gate bush / 93S. Gate bush part / 100. Resin molded product / 101. Gate mark / 103. Gate bush / 103S. Gate bush part / 110···Resin molded product / 111···Gate mark / 113···Gate bush / 113S···Gate bush part / 120···Resin molded product / 121···Gate mark / 203···Gate bush / 203S···Gate bush part / 602···Secant line / CAV···Cavity / CAV-EX···Cavity part / CX···Central axis / d···Width of part 63S / D···Tip width of valve pin 2 / EX, EX70···Convex part / HA···Area closest to the gate exit / ISM···Mold surface to which the non-exterior surface is transferred / MR···Molten resin / OS···Exterior surface / OSM···Mold surface to which the exterior surface is transferred / SL···Curved surface / SR···Solidified resin

Claims

1. a first mold having a flow path for molten resin and forming a first surface of the resin molded product; a second mold for forming a second surface of the resin molded product opposite to the first surface; a valve pin that can move forward and backward in a predetermined direction and open and close the flow path, when the molten resin is injected from the flow path into the cavity formed between the first mold and the second mold, a part of the first mold is located in a part between the tip surface of the valve pin and the second mold in the predetermined direction, and the first mold is not located in a part other than the part between the tip surface of the valve pin and the second mold in the predetermined direction, When opening the flow path, the tip surface of the valve pin is separated from the part of the first mold so that the part of the first mold is positioned on an extension line of a central axis of the valve pin. A manufacturing method characterized by:

2. A first mold having a flow path for molten resin and forming a first surface of a resin molded product; a second mold for forming a second surface of the resin molded product opposite to the first surface; a valve pin that can move forward and backward in a predetermined direction and open and close the flow path, when the molten resin is injected from the flow path into the cavity formed between the first mold and the second mold, a part of the first mold is located in a part between the tip surface of the valve pin and the second mold in the predetermined direction, and the first mold is not located in a part other than the part between the tip surface of the valve pin and the second mold in the predetermined direction, When closing the flow path, a portion of the tip surface of the valve pin that includes at least a central axis of the valve pin is brought into contact with the portion of the first mold. A manufacturing method characterized by:

3. The manufacturing method according to claim 1 or 2, the resin injected from the resin nozzle accommodating the valve pin has its flow direction changed by the part of the first mold, and then reaches the molding surface of the second mold; A manufacturing method characterized by:

4. The manufacturing method according to any one of claims 1 to 3, the second mold is a movable mold, and when the resin molded product is released from the mold, the second mold is moved in a direction away from the first mold while the valve pin keeps the flow path closed. A manufacturing method characterized by:

5. The manufacturing method according to any one of claims 1 to 4, When the resin molded product is released from the mold, the resin molded product slides against the side surface of the valve pin. A manufacturing method characterized by:

6. The manufacturing method according to any one of claims 1 to 5, The side surface of the flow path has a portion inclined with respect to the predetermined direction. A manufacturing method characterized by:

7. The manufacturing method according to any one of claims 1 to 6, a distance from a tip surface of the valve pin to the second mold when the flow path is closed is 2.5 mm or more and 15 mm or less; A manufacturing method characterized by:

8. The manufacturing method according to any one of claims 1 to 7, The temperature of the region (HA) facing the flow path on the molding surface of the second mold is maintained below the glass transition point of the material of the resin molded product. A manufacturing method characterized by:

9. A manufacturing apparatus for manufacturing a resin molded product, a first mold having a flow path for molten resin and forming a first surface of the resin molded product; a second mold for forming a second surface of the resin molded product opposite to the first surface; a valve pin that can advance and retreat in a predetermined direction and open and close the flow path, a part of the first mold is disposed between a tip surface of the valve pin on a side of a cavity formed between the first mold and the second mold and the second mold in the predetermined direction; the first mold is not disposed in a portion other than the portion between the tip surface of the valve pin and the second mold in the predetermined direction, When the flow path is opened, the tip surface of the valve pin is separated from the part of the first mold; When closing the flow path, at least a portion of the tip surface of the valve pin that includes a central axis of the valve pin abuts against the portion of the first mold. A manufacturing apparatus characterized by:

10. 10. The manufacturing apparatus according to claim 9, The first mold comprises: a piece for forming a part of the first surface; a bushing that is detachable from the bridge; Including, the portion of the first mold and the flow path are provided in the bush; A manufacturing apparatus characterized by:

11. The manufacturing apparatus according to claim 9 or 10, The transfer surface of the second mold is decorated. A manufacturing apparatus characterized by:

12. The manufacturing apparatus according to any one of claims 9 to 11, a distance from a tip surface of the valve pin to the second mold when the flow path is closed is 2.5 mm or more and 15 mm or less; A manufacturing apparatus characterized by:

13. 13. The manufacturing apparatus according to claim 9, a hot runner nozzle that accommodates the valve pin; A manufacturing apparatus characterized by:

14. The manufacturing method according to any one of claims 1 to 8, the resin molded product has a first surface on which a convex portion is provided and a second surface opposite to the first surface, the protrusion has a molding mark formed by the valve pin, and at least a part of the tip end surface of the valve pin is not transferred to the molding mark; A manufacturing method characterized by:

15. The manufacturing method according to claim 14, The molding mark has a side surface of the valve pin transferred thereto. A manufacturing method characterized by:

16. 16. The method according to claim 14 or 15, the resin molded product includes a plate-like portion having the first surface and the second surface, the plate-like portion having a thickness of 0.5 mm or more and 5 mm or less, and the protrusion having a height of 2 mm or more and 10 mm or less; A manufacturing method characterized by:

17. 17. The method according to any one of claims 14 to 16, the protrusion is provided with a molding surface molded by the first mold, and the molding surface has a portion inclined with respect to the second surface; A manufacturing method characterized by:

18. 18. The method according to any one of claims 14 to 17, The convex portion has a polyhedral or cylindrical shape formed by four or more planes. A manufacturing method characterized by:

19. 19. The method according to any one of claims 14 to 18, The protrusions are provided in plural. A manufacturing method characterized by:

20. A method for manufacturing a device including a functional component and an exterior component that is a resin molded product and covers the functional component, The exterior component is manufactured by the manufacturing method according to any one of claims 1 to 7 or 14 to 18, and the exterior component is disposed so that the first surface is located between the second surface and the functional component. A method for manufacturing an equipment characterized by the above.

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