Injection molded article, injection molding die, and injection molding method

Abstract

Provided is an injection molded article with which it is possible to reduce component cost by dispensing with an expensive die and a die drive controller due to the shape of a molded article. A lens (1) serves as the injection molded article, which is molded from a material having shrinkage anisotropy. The injection molded article has one material inflow part (10) in an outer peripheral part (3). A thin part (4) thinner than at least the outer peripheral part (3) is provided between the material inflow part (10) of the injection molded article and a lens part (2) positioned at the center of the injection molded article.

Description

Injection molded product, injection mold, and injection molding method

[0001] The present invention relates to an injection-molded product, an injection-molding mold, and an injection-molding method.

[0002] Conventionally, resins with shrinkage anisotropy, such as crystalline resins, have been used to produce resin molded products (hereinafter also referred to as molded articles, injection-molded articles, or parts) for a variety of applications, including everyday items, automobile parts, and electrical appliance parts. Crystalline resins have the property of shrinking along the resin flow direction (shrinkage anisotropy). This results in large dimensional differences between the length and width of the molded article due to shrinkage along the filling direction. For this reason, a method has been proposed for forming orientation in multiple directions within an injection-molded article using a general injection molding machine (see Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2002-086514

[0004] However, the invention described in Patent Document 1 requires a complex gate opening and closing mechanism because multiple gates are provided and resin is filled sequentially. Furthermore, when filling resin in different directions, it is necessary to create a space that allows resin flow. This requires a drive mechanism, which increases mold costs and requires the introduction of an expensive mold drive control device. Therefore, further improvements are needed to reduce the component costs of molded products.

[0005] The injection-molded product of the present invention has been made in view of the above-mentioned background. That is, an object of the present invention is to reduce the cost of parts by eliminating the need for expensive molds and mold drive control devices depending on the shape of the molded product.

[0006] The above-mentioned object of the present invention is achieved by the following configuration: (1) An injection-molded product is an injection-molded product molded from a material having shrinkage anisotropy, and has one material inlet portion at the outer periphery. The injection-molded product has a thin-walled portion thinner than at least the outer periphery between the material inlet portion and the center of the injection-molded product.

[0007] (2) The injection-molded product according to (1), wherein the thin-walled portion, which is thinner than the outer peripheral portion, is located so as to include the center of the injection-molded product.

[0008] (3) The injection-molded product according to (1), wherein the thin-walled portion, which is thinner than the outer peripheral portion, surrounds the center of the injection-molded product and is thinner than the center.

[0009] (4) An injection-molded product according to (1), wherein the thin-walled portion, which is thinner than the outer peripheral portion, is located on a line connecting the center of the injection-molded product and the material inlet portion.

[0010] (5) An injection-molded product according to (1), wherein the center is thicker than the thin-walled portion.

[0011] (6) The injection-molded product according to (1), wherein the outer peripheral portion has a thickness that is 3.25 times or more the thickness of the thin-walled portion.

[0012] (7) The injection-molded product according to (1), wherein the thickness of the thin-walled portion is 0.08 mm or more and 0.15 mm or less.

[0013] (8) An injection-molded product according to (1), wherein the center is filled with the material up to the center.

[0014] (9) The injection-molded product according to (1), wherein there is no hole in either the center or the thin-walled portion of the injection-molded product.

[0015] (10) The injection-molded product according to (1), wherein the viscosity of the material during molding is 1000 g / (cm s) or more and 55000 g / (cm s) or less, and the thickness of the thin-walled portion or the center is 0.08 mm or more and 0.15 mm or less.

[0016] (11) The injection-molded product according to (1), wherein the viscosity of the material during molding is 380 g / (cm s) or more and 1000 g / (cm s) or less, and the thickness of the thin-walled portion or the center is 0.08 mm or more and 0.20 mm or less.

[0017] (12) The injection-molded product according to (1), wherein the viscosity of the material during molding is 20 g / (cm s) or more and 380 g / (cm s) or less, and the thickness of the thin-walled portion or the center is 0.08 mm or more and 0.25 mm or less.

[0018] (13) The injection-molded product according to (1), wherein the molding is injection molding.

[0019] (14) The injection-molded product according to (1), wherein the molding is injection compression molding.

[0020] (15) The injection-molded product according to (1), which has a lens portion used for focusing far-infrared rays.

[0021] (16) The injection molded product according to (15), wherein the diameter of the lens portion is 10 mm or less.

[0022] (17) The injection molded product according to (1), wherein the outer peripheral portion has an attachment portion for attachment to an attachment portion.

[0023] (18) An injection mold for molding the injection molded article according to any one of (1) to (17).

[0024] (19) An injection molding method for molding an injection-molded product from a material with shrinkage anisotropy. In the injection molding method, the material is introduced through a material inlet provided in the outer peripheral space of a mold. Then, in the injection molding method for an injection-molded product, the material is caused to flow from the outer peripheral space to the center by a thin-walled space between the material inlet and the center.

[0025] According to the present invention, expensive dies and die drive control devices are not required depending on the shape of the molded product, thereby reducing the cost of parts.

[0026] 1 is a plan view showing the internal configuration of an injection compression mold for molding an injection-molded product according to a first embodiment. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1 showing the configuration of the injection-molded product according to the first embodiment. FIG. 3 is a table showing the resin fluidity for each ratio of the outer periphery to the thin-walled portion in the injection-molded product according to the first embodiment. FIG. 4 is a table showing whether or not resin flows for each resin viscosity relative to the dimension in the thickness direction of the thin-walled portion in the first embodiment. FIG. 5 is a cross-sectional view taken along line VI-VI in FIG. 5 showing the configuration of the injection-molded product according to the second embodiment. FIG. 6 is a plan view showing the internal configuration of an injection compression mold for molding an injection-molded product according to a third embodiment. FIG. 7 is a cross-sectional view taken along line IIX-IIX in FIG. 7 showing the configuration of the injection-molded product according to the third embodiment.

[0027] First Embodiment Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. [Configuration of Injection-Molded Product] Fig. 1 is a structural diagram of the internal space formed in an injection-molded compression mold 41 for molding an injection-molded product according to this embodiment. The injection-molded product of the first embodiment is a lens 1 molded from a material with shrinkage anisotropy. To injection-mold this, the injection-molded compression mold 41 is provided with one material inlet hole 40 in the outer peripheral space 43. No other material inlet holes are formed in the injection-molded compression mold 41 other than the material inlet hole 40 in the outer peripheral space 43.

[0028] The injection molding compression mold 41 includes a thin-walled space 44 and a lens space. The material 8 flows from the material inlet hole 40 along the outer peripheral space 43 and from the outer peripheral space 43 toward the central lens space. The material injected into the injection molding compression mold 41 is, for example, a crystalline resin. Alternatively, a resin material with shrinkage anisotropy, such as a filler-containing resin or a fiber-containing resin, may be used. During injection molding, the resin material is melted to a desired viscosity at a predetermined temperature.

[0029] Fig. 2 is a diagram showing the configuration of an injection-molded product according to this embodiment. The lens 1 shown in Fig. 2 is substantially circular in plan view, and has a lens portion 2 used to focus far-infrared rays at its radial center. The diameter d of the lens portion 2 is 10 mm or less. As shown in Fig. 2, the lens portion 2 becomes thicker toward the center of the circle, and bulges out into a hemispherical shape having a height dimension h2.

[0030] The lens portion 2 is used to collect far-infrared rays and has a diameter of 10 mm or less.

[0031] The lens 1 also has an annular outer peripheral portion 3 that surrounds the lens portion 2. When the lens 1 is attached as a component to a mounting portion of an optical device or the like, the outer peripheral portion 3 serves as a mounting portion that engages with or is gripped by the mounting portion. In the first embodiment, the height dimension h3 of the outer peripheral portion 3 is set to be 0.26 mm or more and 0.36 mm or less. The height dimension h3 of the outer peripheral portion 3 is the same height around the entire circumference, and is formed to have a constant thickness.

[0032] The lens 1 of the first embodiment has one material inlet portion 10 on the outer surface of the outer peripheral portion 3. The lens 1 does not have any material inlet portions in either the lens portion 2 or the thin-walled portion 4 other than the material inlet portion 10 in the outer peripheral portion 3.

[0033] Furthermore, an annular thin-walled portion 4 is provided between the material inlet portion 10 of the lens 1 and the lens portion 2 formed at the center of the lens 1. As shown in FIG. 2 , the thin-walled portion 4 is formed to be thinner than at least the height dimension h3 of the outer peripheral portion 3. Specifically, the height dimension h1 of the thin-walled portion 4 is set to be 0.08 mm or more and 0.15 mm or less. The height dimension h1 of the thin-walled portion 4 is also formed to be the same height and constant thickness around the entire periphery of the lens portion 2. As a result, the thin-walled portion 4 is thinner than the outer peripheral portion 3 located radially outward at any point in the circumferential direction. Note that the lens 1 of the first embodiment is formed so that the height dimension h1 of the thin-walled portion 4 is smaller and thinner than the height dimension h2 of the lens portion 2 located radially inward.

[0034] The resin flow of the molten material 8 can be adjusted by adjusting the ratio between the height dimension h1 of the thin-walled portion 4 located toward the center and the height dimension h3 of the outer peripheral portion 3. Specifically, if the dimension h1 of the thin-walled portion 4 is not sufficiently smaller than the dimension h3 of the outer peripheral portion 3, the molten material flowing through the material inlet 40 of the injection molding compression mold 41 will flow straight toward the center. If the material has the property of shrinking along the resin flow direction (shrinkage anisotropy), such as a crystalline resin, the dimensional difference between the vertical and horizontal directions along the flow direction will be large. On the other hand, if the dimension h1 of the thin-walled portion 4, i.e., the height dimension h1 of the thin-walled space 44, is made too small, the necessary flow toward the center may be hindered depending on the viscosity of the molten resin and the injection pressure. Therefore, the lens 1 of embodiment 1 optimizes the ratio between the height dimension h1 of the thin-walled portion 4 and the height dimension h3 of the outer peripheral portion 3. In this way, in the first embodiment, some dimensional relationships within the shape of the injection-molded product are set by ratio. This makes it possible to easily obtain the desired resin flow without using an expensive molding machine, thereby reducing the cost of the part.

[0035] Figure 3 is a table showing the resin fluidity for each ratio of the outer peripheral portion 3 to the thin-walled portion 4 in the lens 1 of the first embodiment. The table shows the experimental results for the flow direction when the viscosity of the material is 10243 (g / cm s) and the stress in the inflow direction is 80 (MPa). As shown in Figure 3, even if the dimension h1 of the thin-walled portion 4 located toward the center is 0.08 mm, if the dimension h3 in the height direction of the outer peripheral portion 3 is thin, for example, 0.21 mm or less, the ratio is less than 3.25.

[0036] Under these conditions, the molten material flowing through the material inlet 40 of the injection molding compression mold 41 flows straight toward the center. This prevents the desired resin flow (shown as "x" in Figure 3). It is desirable for the resin to flow toward the center from any point on the entire periphery of the outer peripheral portion 3. To achieve this resin flow (shown as "o" in Figure 3), it is desirable for the thickness dimension h3 of the outer peripheral portion 3 to be at least 3.25 times the thickness dimension h1 of the thin-walled portion 4. In other words, in the injection molding compression mold 41, it is desirable for the height dimension h3 of the outer peripheral space 43 to be at least 3.25 times the height dimension h1 of the thin-walled space 44 that forms the thin-walled portion 4. If the height of the outer peripheral space 43 is at least 3.25 times the height of the thin-walled space 44, the molten material 8 flowing through the material inlet 40 will not flow straight toward the center. In other words, the outer peripheral space 43 can be filled by flowing evenly toward the center from any point on the entire periphery. For this reason, in the lens 1 of this embodiment, the height dimension h3 of the outer circumferential portion 3 is set to be 3.25 times or more the thickness of the thin portion 4.

[0037] Furthermore, the thin-walled portion 4 in the first embodiment is formed in an annular shape surrounding the lens portion 2 located at the center of the lens 1, and is formed thinner than the lens portion 2. That is, in the lens space of the injection molding compression mold 41, the height dimension h2 of the center 42 is set larger than the height dimension h1 of the thin-walled space 44. As a result, the center of the lens portion 2 is formed to be thicker than the thin-walled portion 4. As a result, the material 8 flowing from each location through the thin-walled space 44 from the peripheral space 43 flows toward the center of the lens space from all four sides with even pressure. Therefore, the material 8 is further evenly filled up to the center of the lens space.

[0038] Next, the effects of the injection-molded product of the first embodiment will be described. [Injection Molding] The lens 1 as the injection-molded product of the first embodiment is molded, for example, using an injection compression molding method for molding an injection-molded product from a material 8 having shrinkage anisotropy. First, an injection compression mold 41 for molding the lens 1 is set in an injection compression molding machine. Then, heated molten resin is injected into the injection compression mold from a single material inlet 40 provided in the outer peripheral space 43 of the injection compression mold 41. The material 8 flows into the clamped injection compression mold 41, fills it, and is compressed to be molded. Then, as the temperature drops, the material 8 hardens and takes on the desired shape of the lens 1.

[0039] In the injection compression molding method of the first embodiment, material 8 is flowed toward the center of the lens space from a single material inlet provided in the peripheral space 43 of the injection compression mold corresponding to the outer periphery 3 of the lens 1. The injection compression mold 41 for the lens 1 has a height dimension h3 of the peripheral space 43 that is set to be at least 3.25 times the height dimension h1 of the thin-walled space 44. Therefore, the material 8 flowing into the injection compression mold 41 is partially blocked by the thin-walled space 44 from traveling in a straight line, preventing it from directly reaching the center. Therefore, most of the material 8 is divided into left and right parts along the outer periphery of the thin-walled space 44, and each flows around the periphery of the peripheral space 43, tracing an arc toward the opposite side of the material inlet 40. The material 8, which is filled in the peripheral space 43 and has its pressure increased, flows evenly inward from each circumferential location of the peripheral space 43 toward the center of the lens space, filling the center 42 of the lens space.

[0040] Figure 4 is a table showing whether resin flow occurs for each resin viscosity relative to the thickness dimension of the thin-walled portion in the first embodiment. In Figure 4, the horizontal axis represents the viscosity (g / cm*s) of the material 8, and the vertical axis represents the distance (mm) from the lower bottom surface of the mold contact portion. It is desirable to obtain the desired resin flow, which flows evenly from any point on the entire periphery of the outer periphery 3 toward the center. Cases where the desired flow is obtained are indicated by a circle. Cases where the desired flow is not obtained are indicated by an x.

[0041] 4, the viscosity of the material 8 during molding is 1,000 g / (cm s) or more and 55,000 g / (cm s) or less. The thickness of the thin-walled portion 4 (or the center 22 in the second embodiment described below, the same applies below) may be 0.08 mm or more and 0.15 mm or less. In this case, it can be seen that the desired resin fluidity can be obtained regardless of the viscosity and thickness.

[0042] Furthermore, the viscosity of the material 8 during molding may be 380 g / (cm s) or more and 1000 g / (cm s) or less, and the thickness of the thin-walled portion 4 may be 0.08 mm or more and 0.20 mm or less. In this case, it is understood that the desired resin fluidity can be obtained regardless of the viscosity and thickness dimension.

[0043] Furthermore, the viscosity of the material during molding may be 20 g / (cm s) or more and 380 g / (cm s) or less, and the thickness of the thin-walled portion 4 may be 0.08 mm or more and 0.25 mm or less. In this case, it is understood that the desired resin fluidity can be obtained regardless of the viscosity and thickness dimension.

[0044] In the first embodiment, as shown in FIG. 1 or FIG. 2 , the shape of the lens 1 eliminates the need for expensive molds and mold drive control devices, thereby reducing component costs. Specifically, the thin-walled portion 4 of the lens 1 is located between the material inlet portion 10 and the lens portion 2, preventing the material 8 flowing from the material inlet portion 10 from directly reaching the lens portion 2 and reducing the amount of material passing through. As a result, a portion of the material 8 passes linearly through the thin-walled portion 4 to reach the lens portion 2. The remaining majority of the material 8 splits into left and right portions, wraps around the outer periphery 3 on both sides, and flows toward the center of the lens portion 2 from various positions around the periphery 3. Therefore, the amount of resin flowing linearly from the material inlet portion 10 toward the center is reduced or equalized with the resin flowing from the outer periphery toward the center. Then, as shown in FIG. 2 , the material 8 flowing from the outer periphery 3 to each portion through the thin-walled portion 4 flows toward the center of the lens portion 2 from all four sides with even pressure. This allows the material 8 to be more uniformly filled within the lens 1. Therefore, even when a molded product is formed using a resin with anisotropic shrinkage as material 8, differences in the length and width of the molded product are unlikely to occur. This makes it possible to reduce the cost of molded products by using a general injection molding machine or injection compression molding machine without using expensive molds and mold drive control devices.

[0045] Second Embodiment Fig. 5 shows the configuration of an injection-molded compression die 51 for molding an injection-molded product 21 of a second embodiment. Fig. 6 shows the configuration of an injection-molded product 21 of the second embodiment. Here, differences from the lens 1 of the first embodiment will be mainly described, and descriptions of identical or equivalent parts will be omitted. In the injection-molded compression die 51 for the injection-molded product 21 of the second embodiment, a thin-walled space 54 that is thinner than the peripheral space 53 is located so as to include a center 52 of the injection-molded compression die 51. Therefore, as shown in Fig. 7, the thin-walled portion 24 is molded to have a circular shape with a constant height dimension h.

[0046] The injection-molded product 21 of the second embodiment configured in this manner exhibits the following effect in addition to the effect of the lens 1 of the first embodiment. Specifically, the material 8 flowing from the material inlet hole 50 of the injection compression mold 51 into the material inlet portion 20 is prevented from moving in a straight line by the thin-walled space 54, making it difficult for the material 8 to flow directly into the center 52. Therefore, the material 8 flows along the outer periphery of the thin-walled space 54, which is circular and has a constant height dimension h1, and is divided into left and right halves within the outer periphery space 53. Therefore, in the injection compression mold 51 of the second embodiment, the flow of material 8 from the outer periphery space 53 toward the center is more uniform, allowing the material 8 to be stably filled up to the center 52. The other configurations and effects are similar to those of the lens 1 of the first embodiment, and therefore will not be described here.

[0047] Third Embodiment Fig. 7 shows the configuration of an injection-molded compression die 61 for molding an injection-molded product 31 of a third embodiment. Fig. 8 shows the configuration of injection-molded product 31 of the third embodiment. Here, the following description will focus on the differences from lens 1 of the first embodiment and injection-molded product 21 of the second embodiment, and some descriptions of the same or equivalent parts will be omitted.

[0048] In the injection molding compression mold 61 for molding the injection molded product 31 of the third embodiment, a thin-walled space 64 that is thinner than the outer peripheral space 63 is located between the material inlet hole 60 and the center 62 in the radial direction.

[0049] As shown in Fig. 8, the thin-walled portion 34 of the injection-molded product 31 is located at the bottom of a rectangular parallelepiped groove formed inside the outer peripheral portion 33. As shown in Fig. 7, the thin-walled space 64 is rectangular in plan view, with its longitudinal direction aligned with the circumferential direction of the outer peripheral space 63, and is located between the radial center 32 and the material inlet hole 60. The thin-walled space 64 shown in Fig. 7 is arranged so that a line L connecting the center 62 and the material inlet hole 60 is perpendicular to the longitudinal direction of the rectangular parallelepiped and passes through the middle portion in the longitudinal direction. In this example, the thin-walled space 64 is located only on line L and is not formed in the circumferential direction of the other outer peripheral spaces 63.

[0050] In addition to the effects of the first embodiment, this injection molding compression mold 61 also makes it difficult for the material 8 flowing through the material inlet port 60 to move in a straight line due to the thin-walled space 64. As a result, the material 8 splits into left and right sides of the thin-walled space 64 and flows around to the opposite side of the material inlet port 60. The other configurations and effects are the same as those of the injection-molded product of the first embodiment and the injection-molded product 21 of the second embodiment, so a description thereof will be omitted.

[0051] As described above, an injection-molded product is an injection-molded product molded from a material with shrinkage anisotropy. The injection-molded product has one material inlet port at the outer periphery. A thin-walled portion thinner than at least the outer periphery is provided between the material inlet port and the center of the injection-molded product. In other words, the injection-molded compression mold for the injection-molded product has one material inlet port in the outer periphery space. A thin-walled space thinner than at least the outer periphery space is provided between the material inlet port and the center of the injection-molded compression mold.

[0052] Injection-molded products constructed in this manner eliminate the need for expensive molds and mold drive control devices depending on the molded product's shape, thereby reducing component costs. Specifically, the thin-walled space of the injection compression mold is located between the material inlet and the center, preventing the resin flowing through the material inlet from reaching the center directly, thereby reducing the amount of flow passing through. As a result, the resin flows around the outer peripheral space and toward the center from various positions on the periphery of the outer peripheral space. Therefore, the amount of resin flowing linearly from the material inlet toward the center is reduced, or is equalized with the resin flowing from the outer peripheral space toward the center. Therefore, even when a molded product is produced using a resin with shrinkage anisotropy using this injection compression mold, the longitudinal and lateral dimensional differences of the molded product are unlikely to occur. This reduces component costs.

[0053] 5, the thin-walled space 54, which is thinner than the outer peripheral space 53 of the injection-molded product, is located so as to include the center of the injection-molded product. This prevents the flow of the material 8 toward the center of the injection-molding compression mold 51, making the flow even more uniform.

[0054] 2, the thin-walled portion 4, which is thinner than the peripheral portion 3, surrounds the lens portion 2 located at the center of the lens 1 and is thinner than the center. As shown in FIG. 1, the amount of material 8 flowing linearly from the peripheral thin-walled space 44 toward the center is reduced or equalized with the material 8 flowing toward the center from each position in the peripheral space 43.

[0055] 7, a thin-walled space 64, which is thinner than the outer peripheral space 63, is located between the center 62 of the injection molding compression mold 61 and the material inlet hole 60. As a result, the flow of material 8 toward the center 62 of the injection molding compression mold 61 is obstructed by the thin-walled space 64, and the flow is divided into two parts, which are then routed around to the left and right, and are then equalized.

[0056] 2 or the center 32 shown in FIG. 8 is thicker than the thin-walled portion 4 or 34. Therefore, the material 8 that is distributed evenly along the outer periphery 3 by the thin-walled portion 4 or 34 flows smoothly toward the center of the lens portion 2 or the center 32. This allows the lens 1, etc. to be filled evenly.

[0057] Furthermore, the thickness of the outer peripheral portion 3 is at least 3.25 times the thickness of the thin-walled portion 4. This makes it easy to optimize the ratio between the height dimension h1 of the thin-walled portion 4 of the lens 1 and the height dimension h3 of the outer peripheral portion 3.

[0058] The height of the thin-walled space, i.e., the thickness of the thin-walled portion, is 0.08 mm or more and 0.15 mm or less, so that the viscosity of the material 8 can be optimized even when resin materials with various viscosities are used, ranging from low to high.

[0059] Furthermore, the lens portion 2 is filled with the material 8 up to the center, which further reduces uneven distribution of the material 8 within the lens 1.

[0060] Furthermore, there are no holes in the center or in the thin-walled portions of the injection-molded product. This excludes parts with shaft holes, such as gears. Parts with shaft holes, such as gears, can be easily manufactured into products by performing secondary processing to drill additional shaft holes.

[0061] As shown in Figure 4, the viscosity of the material 8 during molding is 1,000 g / (cm s) or more and 55,000 g / (cm s) or less. The thickness of the thin-walled portion 4 (or the center 22 in Figure 6, the same applies below) is 0.08 mm or more and 0.15 mm or less. In this case, the desired resin fluidity can be obtained regardless of the viscosity and thickness.

[0062] The viscosity of the material 8 during molding is 380 g / (cm s) or more and 1000 g / (cm s) or less, and the thickness of the thin-walled portion 4 is 0.08 mm or more and 0.20 mm or less. In this case, the desired resin fluidity can be obtained regardless of the viscosity and thickness.

[0063] Furthermore, the viscosity of the material during molding is 20 g / (cm s) or more and 380 g / (cm s) or less, and the thickness of the thin-walled portion 4 is 0.08 mm or more and 0.25 mm or less. In this case, the desired resin fluidity can be obtained regardless of the viscosity and thickness.

[0064] Furthermore, the molding is injection molding, which allows the use of a general injection molding machine that does not require a complex mechanism, thereby reducing the cost of molded products.

[0065] Furthermore, the molding is injection compression molding, which allows the use of a general injection compression molding machine that does not require a complex mechanism, thereby reducing the part cost of the molded product.

[0066] 2, the injection molded product has a lens portion 2 used to collect far-infrared rays. This allows the molding of a lens 1 having a highly accurate lens portion 2.

[0067] The diameter of the lens portion 2 is 10 mm or less. In this way, the lens 1 having a small, highly accurate lens portion 2 can be molded.

[0068] 2, the outer peripheral portion 3 has a mounting portion for mounting to a mounting target portion, thereby enabling an injection molded product having the outer peripheral portion 3 to have improved mounting accuracy.

[0069] Furthermore, injection molded products are produced using an injection mold, which allows material to be injected from a single material inlet, thereby further reducing the part cost of the injection molded product.

[0070] The injection molding method is for molding an injection-molded product from a material 8 having shrinkage anisotropy. In the injection molding method, the material 8 is introduced through one material inlet portion 10 provided in the outer peripheral portion 3. The injection molding method exhibits a practically beneficial effect in that the material 8 can be filled from each position in the outer peripheral portion 3 toward the center in a desired flow direction and flow amount due to the thin-walled portion 24 set between the material inlet portion 10 and the central lens portion 2.

[0071] Although the embodiments and their modifications of the present invention have been described above, these embodiments are merely illustrative and do not limit the technical scope of the present invention. The present invention can take on various other embodiments, and various modifications such as omissions and substitutions can be made without departing from the spirit of the present invention. These embodiments and their modifications are included within the scope and spirit of the invention described in this specification, etc., and are included in the invention described in the claims and their equivalents.

[0072] For example, in the first to third embodiments, injection compression molding has been used to form the injection-molded product, but the present invention is not limited to this. For example, the injection-molded product may be formed by an injection molding method using an injection mold. In other words, any molding method for a molded product, such as press-fit molding including filling molding, may be used as long as the molding method has one material inlet hole on the outer periphery.

[0073] The material may be a crystalline resin such as PE (polyethylene), PP (polypropylene), olefin, PA (polyamide: trademark name: nylon), or POM (polyacetal) as long as it has shrinkage anisotropy. Furthermore, the material may be PBT (polybutylene), PPS (polyphenyl sulfide), or PEEK (polyether ether ketone) as long as it has shrinkage anisotropy. The material may also be a mixture of these materials or a mixture containing filler or fiber.

[0074] Furthermore, as shown in FIG. 2 , in the lens 1 of the first embodiment, the height dimension h1 of the thin-walled portion 4 is set to be smaller than the height dimension h3 of the outer peripheral portion 3 and smaller than the height dimension h2 of the lens portion 2. However, this is not particularly limited. For example, as in the injection-molded product 21 of the second embodiment shown in FIG. 6 , the thin-walled portion 24 may be set to be thinner than the outer peripheral portion 23. Furthermore, as in the injection-molded product 31 of the third embodiment shown in FIG. 8 , it is sufficient that at least a portion of the height dimension h1 of the thin-walled portion 34 is set to be smaller and thinner than the height dimension h2 of the center 32. In other words, it is sufficient that the thickness dimension of the thin-walled portion is smaller and thinner than the height dimension of at least one of the outer peripheral portion or the center.

[0075] Furthermore, the injection-molded product 21 of the second embodiment and the injection-molded product 31 of the third embodiment are not limited to the lens 1, and may be any product molded from a material with anisotropic shrinkage. In other words, the injection-molded products 21 and 31 may be any other optical components, such as a filter.

[0076] 8, in the injection-molded product 31 of the third embodiment, the thin-walled portion 34 is formed in a rectangular shape in plan view at the bottom of the recessed groove located inside the outer periphery 33. However, the shape of the thin-walled portion 34 is not limited to a rectangle. For example, the thin-walled portion 34 may be square, oval, semicircular, crescent-shaped, or the like. In other words, the thin-walled portion 34 may have any shape, any number, or a combination of multiple shapes, as long as it is thinner than the outer periphery 33 and located between the center 32 of the injection-molded product 31 and the material inlet portion 30.

[0077] REFERENCE SIGNS LIST 1 Lens (injection molded product) 2 Lens portion (center) 3, 23, 33 Peripheral portion 4, 24, 34 Thin-walled portion 8 Material 10, 20, 30 Material inlet portion 21, 31 Injection molded product 22, 32 Center 41, 51, 61 Injection molding compression mold (mold) 43, 53, 63 Peripheral space 44, 54, 64 Thin-walled space 40, 50, 60 Material inlet hole 42, 52, 62 Center

Claims

1. An injection-molded product made from a material with shrinkage anisotropy, which has one material inlet at the outer periphery, and a thin-walled section that is thinner than at least the outer periphery between the material inlet and the center of the injection-molded product.

2. The injection-molded product according to claim 1, wherein the thin-walled portion, which is thinner than the outer periphery, is located including the center of the injection-molded product.

3. The injection-molded product according to claim 1, wherein the thin-walled portion, which is thinner than the outer peripheral portion, surrounds the center of the injection-molded product and is thinner than the center.

4. An injection-molded product according to claim 1, wherein the thin-walled portion, which is thinner than the outer peripheral portion, is located on a line connecting the center of the injection-molded product and the material inlet portion.

5. The injection molded product according to claim 1, wherein the center is thicker than the thin-walled portion.

6. The injection molded product according to claim 1, wherein the thickness of the outer peripheral portion is at least 3.25 times the thickness of the thin-walled portion.

7. The injection molded product according to claim 1, wherein the thickness of the thin-walled portion is 0.08 mm or more and 0.15 mm or less.

8. The injection molded article of claim 1, wherein the center is filled to the center with the material.

9. The injection molded product according to claim 1, wherein neither the center nor the thin-walled portion of the injection molded product has any holes.

10. The injection-molded product according to claim 1, wherein the viscosity of the material during molding is 1,000 g / (cm s) or more and 55,000 g / (cm s) or less, and the thickness of the thin-walled portion or center is 0.08 mm or more and 0.15 mm or less.

11. The injection-molded product according to claim 1, wherein the viscosity of the material during molding is 380 g / (cm s) or more and 1000 g / (cm s) or less, and the thickness of the thin-walled portion or center is 0.08 mm or more and 0.20 mm or less.

12. The injection-molded product according to claim 1, wherein the viscosity of the material during molding is 20 g / (cm s) or more and 380 g / (cm s) or less, and the thickness of the thin-walled portion or center is 0.08 mm or more and 0.25 mm or less.

13. The injection-molded article according to claim 1, wherein the injection-molded article is formed by injection molding.

14. The injection-molded article according to claim 1, wherein the injection-molded article is molded by injection compression molding.

15. The injection molded product according to claim 1, which has a lens portion used to focus far infrared rays.

16. The injection molded product according to claim 15, wherein the diameter of the lens portion is 10 mm or less.

17. The injection molded product according to claim 1, wherein the outer peripheral portion has a mounting portion for mounting to a mounting portion.

18. An injection mold for molding the injection molded article according to any one of claims 1 to 17.

19. An injection molding method for molding an injection-molded product from a material with anisotropic shrinkage, comprising: injecting the material through a material inlet provided in the outer peripheral space of an injection mold; and allowing the material to flow from the outer peripheral space to the center through a thin-walled space between the material inlet and the center.

20. An injection molding mold for molding injection-molded products using a material with shrinkage anisotropy, which has one material inlet hole in the outer peripheral space, and a thin-walled space that is at least thinner than the outer peripheral space is provided between the material inlet hole and the center of the mold space.

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