Decorative sheet, molded article, and method for manufacturing molded article

Abstract

[Problem] To provide technology that makes it possible to omit a process for adhering a protective film to the surface of a decorative sheet after injection molding. [Solution] A decorative sheet 1 that comprises a peelable protective film 40 that covers the surface of a top layer 30. It is thus possible to perform injection molding in a state in which the decorative sheet 1 that includes the projective film 40 has been inserted into a cavity in a metal mold. As a result, it is possible to omit a process for adhering the protective film 40 to the surface of the decorative sheet 1 after injection molding.

Description

Decorative sheet, molded article, and method for producing molded article

[0001] The present disclosure relates to a decorative sheet, a molded article provided with the decorative sheet, and a method for producing the molded article.

[0002] Conventionally, a decorative molding technique is known in which the surface of a molded article is decorated with a decorative sheet by performing injection molding in a state where the decorative sheet is inserted into a mold. Conventional decorative molding techniques are described, for example, in Patent Document 1. In Patent Document 1, a part of the surface of the molding resin is covered with the decorative sheet, and another part of the surface of the molding resin is exposed from the decorative sheet.

[0003] In the case where coating is performed on an exposed portion of the surface of the molding resin as in Patent Document 1, first, the surface of the decorative sheet is masked with a protective film. Then, after coating the surface of the molding resin, the protective film is peeled off from the surface of the decorative sheet. Conventional techniques related to masking during coating are described, for example, in Patent Document 2.

[0004] Japanese Patent No. 4459585 Japanese Unexamined Patent Application Publication No. 2022-114654

[0005] However, conventional coating methods require a step of masking the surface of the decorative sheet with a protective film after injection molding. This increases the number of manufacturing steps for the product. Further, when the surface of the decorative sheet has a complex three-dimensional shape, masking with a protective film may be difficult in some cases.

[0006] Accordingly, an object of the present disclosure is to provide a technique that can omit the step of attaching a protective film to the surface of a decorative sheet after injection molding.

[0007] The present disclosure provides a decorative sheet inserted into a cavity of a molding die, comprising: a backer layer; a design layer covering a surface of the backer layer; a top layer covering a surface of the design layer; and a peelable protective film covering a surface of the top layer.

[0008] The decorative sheet may be shaped into a three-dimensional shape.

[0009] It is preferable that a melting point of the protective film is 140°C or higher.

[0010] It is desirable that the protective film can stretch by 120% or more in the direction along its surface without tearing.

[0011] The top layer is formed from a mixed resin containing PVDF (polyvinylidene fluoride) and PMMA (polymethyl methacrylate), and it is desirable that the mass percentage concentration of PVDF on the protective film side of the top layer is greater than the mass percentage concentration of PMMA.

[0012] On the surface of the top layer facing the design layer, it is desirable that the mass percentage concentration of PMMA is greater than the mass percentage concentration of PVDF.

[0013] Furthermore, this disclosure relates to a molded article comprising the decorative sheet and a resin part, wherein a portion of the surface of the resin part may be covered by the decorative sheet, and the other portion of the surface of the resin part may be exposed from the decorative sheet.

[0014] Furthermore, this disclosure provides a method for manufacturing a molded article, comprising: a) the step of manufacturing a decorative sheet having a backer layer, a design layer covering the surface of the backer layer, a top layer covering the surface of the design layer, and a protective film covering the surface of the top layer; b) the step of inserting the decorative sheet into the cavity of a molding die; and c) the step of filling the cavity with molten resin and curing it to obtain a molded article comprising the decorative sheet and a resin portion.

[0015] In the molded product obtained by step c), a portion of the surface of the resin part may be covered by the decorative sheet, while the other portion of the surface of the resin part may be exposed from the decorative sheet.

[0016] The process may include, after step c), d) a step of applying paint to the portion of the resin surface exposed from the decorative sheet, and e) a step of peeling the protective film from the top layer after step d).

[0017] According to this disclosure, injection molding can be performed with a decorative sheet having a protective film inserted into the cavity of the mold. This eliminates the need to apply a protective film to the surface of the decorative sheet after injection molding.

[0018] This is a perspective view of a molded product with a decorative sheet. This is a cross-sectional view of the molded product. This is a cross-sectional view showing the layer structure of the decorative sheet. This is a flowchart showing the manufacturing procedure of the molded product. This is a diagram showing the heating process during the shaping of the decorative sheet. This is a diagram showing the forming process during the shaping of the decorative sheet. This is a diagram showing the trimming process after the shaping of the decorative sheet. This is a diagram showing the insertion of the decorative sheet into the molding die. This is a diagram showing the clamping of the molding die. This is a diagram showing the injection molding process. This is a diagram showing the release of the molded product from the molding die.

[0019] The embodiments of this disclosure will be described below with reference to the drawings. Note that in some cases, the dimensions of the parts in the drawings of this disclosure may be exaggerated for ease of understanding.

[0020] <1. Embodiments> Figure 1 is a perspective view of a molded product 100 equipped with a decorative sheet 1 according to one embodiment. Figure 2 is a cross-sectional view of the molded product 100. This molded product 100 is a resin product partially decorated with a decorative sheet 1. The molded product 100 is used, for example, as an exterior panel for an automobile. However, the molded product 100 may also be used for the interior of an automobile or for applications other than automobiles.

[0021] As shown in Figure 1, the molded product 100 has a decorative sheet 1 and a resin part 101. During the manufacturing of the molded product 100, the decorative sheet 1 is inserted into the mold, and molten resin is injected into the mold. The resin part 101 is then molded by curing the resin in the mold. The decorative sheet 1 is fixed to the surface of the resin when the resin hardens in the mold. The detailed manufacturing procedure of the molded product 100 will be described later.

[0022] The decorative sheet 1 covers a portion of the surface of the resin part 101. That is, the surface of the resin part 101 has a portion covered by the decorative sheet 1 and a portion exposed from the decorative sheet 1. The portion exposed from the decorative sheet 1 is painted. By making the portion covered by the decorative sheet 1 and the portion exposed from the decorative sheet 1 into a single molded product 100, rather than separate molded products, the number of molded parts can be reduced. In addition, the number of injection molding steps in the manufacturing process can be reduced.

[0023] Figure 3 is a cross-sectional view showing the layer structure of the decorative sheet 1. As shown in Figure 3, the decorative sheet 1 has a decorative sheet body 2 composed of a backer layer 10, a design layer 20, and a top layer 30, and a protective film 40.

[0024] The backer layer 10 is a resin base film. For example, polypropylene resin is used as the material for the backer layer 10. However, polyester resin, vinyl chloride resin, acrylic resin, polycarbonate resin, polyethylene resin, polyurethane resin, polystyrene resin, acetate resin, polyamide resin, etc. may also be used as the material for the backer layer 10. Furthermore, the backer layer 10 may be a mixture of two or more of these materials.

[0025] The backer layer 10 plays a role in maintaining the shape of the decorative sheet 1. The thickness of the backer layer 10 is set to a thickness that allows for good shaping, injection molding, handling, etc. For example, it is desirable that the thickness of the backer layer 10 be 100 μm or more and 500 μm or less.

[0026] The design layer 20 is a layer for adding decorations such as patterns and colors to the molded product 100. The design layer 20 covers the surface of the backer layer 10 (the surface opposite to the surface on which the resin portion 101 is provided). As shown in Figure 3, the design layer 20 in this embodiment has an adhesive layer 21, a pattern layer 22, and a release layer 23.

[0027] The pattern layer 22 is a layer of ink on which the design to be decorated is formed. The pattern layer 22 is formed, for example, by gravure printing. The pattern layer 22 may also contain a metal film such as aluminum. The adhesive layer 21 is an adhesive layer interposed between the pattern layer 22 and the backer layer 10. The pattern layer 22 is bonded to the surface of the backer layer 10 by the adhesive layer 21. The release layer 23 covers the surface of the pattern layer 22 (the side opposite to the adhesive layer 21). The release layer 23 is a layer that facilitates the peeling of the design layer 20 from the base film that holds the design layer 20 in step S1 of the manufacturing process described later.

[0028] The top layer 30 is a film that covers the surface of the design layer 20 (the side opposite to the backer layer 10). To ensure the visibility of the design layer 20, the top layer 30 is made of a transparent material. For example, a mixed resin containing PVDF (polyvinylidene fluoride) and PMMA (polymethyl methacrylate) is used as the material for the top layer 30. However, the top layer 30 may be made of other resins. The surface of the top layer 30 may have fine irregularities to express a matte texture.

[0029] If the top layer 30 is a mixed resin containing PVDF and PMMA, it is preferable to make the mass percentage concentration of PMMA higher than that of PVDF on the surface of the top layer 30 facing the design layer 20. This will improve the adhesion between the top layer 30 and the design layer 20 due to the action of PMMA containing acrylic components. Specifically, it is desirable to make the mass percentage concentration of PMMA at least 5 mass% higher than that of PVDF on the surface of the top layer 30 facing the design layer 20. On the surface of the top layer 30 facing the design layer 20, the PVDF concentration may be 0 mass% and the PMMA concentration 100 mass%.

[0030] Furthermore, if the top layer 30 is a mixed resin containing PVDF and PMMA, it is preferable to make the mass percentage concentration of PVDF greater than the mass percentage concentration of PMMA on the side of the top layer 30 facing the protective film 40. This will allow the protective film 40 to be easily peeled off the top layer 30 due to the action of the PVDF containing fluorine in step S7 of the manufacturing process described later. Specifically, it is desirable to make the mass percentage concentration of PVDF greater than the mass percentage concentration of PMMA by 5% or more on the side of the top layer 30 facing the protective film 40.

[0031] The top layer 30 may consist of a single layer having the concentration changes described above, or it may consist of multiple layers with different concentrations.

[0032] The protective film 40 is a film that covers the surface of the decorative sheet body 2. The protective film 40 is laminated to the surface of the top layer 30, which is the outermost surface of the decorative sheet body 2. The protective film 40 masks the surface of the decorative sheet body 2 when painting the surface of the resin part 101 of the molded product 100. This prevents paint from adhering to the surface of the decorative sheet body 2. After painting, the protective film 40 can be peeled off from the top layer 30.

[0033] The protective film 40 is a resin film. The type of resin constituting the protective film 40 is selected considering factors such as adhesion and release properties to the top layer 30, heat resistance and stretchability to withstand shaping, and corrosion resistance to paint. The protective film 40 is formed from, for example, an olefin resin, an ester resin, or a thermoplastic elastomer. Specifically, PE (polyethylene), PC (polycarbonate), PET (polyethylene terephthalate), TPEE (polyester elastomer), EVA (ethylene vinyl acetate copolymer resin), etc., can be used as the material for the protective film 40. The protective film 40 may also be a mixture of two or more resins.

[0034] The melting point of the protective film 40 is preferably 140°C or higher. This prevents the protective film 40 from melting due to the heat generated when shaping the decorative sheet 1 in step S3, which will be described later. However, if the melting point of the protective film 40 is too high, it becomes difficult to manufacture the protective film 40 itself. For this reason, the melting point of the protective film 40 is preferably, for example, 140°C or higher and 200°C or lower.

[0035] Furthermore, it is desirable that the protective film 40 has sufficient stretchability to withstand the shaping of the decorative sheet 1. For example, it is desirable that the protective film 40 can stretch by 120% or more in the direction along its surface without tearing. This suppresses the tearing of the protective film 40 when the decorative sheet 1 is shaped in step S3, which will be described later. It is even more desirable that the protective film 40 can stretch by 170% or more in the direction along its surface without tearing. However, since stretchability significantly exceeding the elongation during shaping is not necessary, the elongation rate of the protective film 40 should be, for example, 120% or more and 350% or less. The above elongation rate can be measured by the film tensile test method of ASTM D882.

[0036] Next, a method for manufacturing the molded product 100 having the decorative sheet 1 described above will be explained. Figure 4 is a flowchart showing the manufacturing procedure for the molded product 100. Figures 5 to 11 show the process of manufacturing the molded product 100.

[0037] When manufacturing the molded product 100, the decorative sheet body 2 is manufactured first (step S1). Specifically, a transfer foil is first manufactured by forming a design layer 20 on the surface of a base film such as PET (polyethylene terephthalate). Then, the side of the transfer foil on which the design layer 20 is formed is adhered to the backer layer 10, and the base film is peeled off to transfer the design layer 20 to the surface of the backer layer 10. After that, a top layer 30 is laminated onto the surface of the design layer 20. This manufactures a decorative sheet body 2 having a backer layer 10, a design layer 20, and a top layer 30.

[0038] Next, a protective film 40 is applied to the surface of the decorative sheet body 2 (step S2). Specifically, the protective film 40 is laminated to the surface of the top layer 30. This produces a decorative sheet 1 having a backer layer 10, a design layer 20, a top layer 30, and a protective film 40.

[0039] Next, the planar decorative sheet 1 is shaped into a three-dimensional shape (step S3). In step S3, first, as shown in Figure 5, the decorative sheet 1 is heated by the heater 90. This softens the decorative sheet 1. Then, as shown in Figure 6, the decorative sheet 1 is shaped into a predetermined shape by vacuum forming or pressure forming. At this time, the protective film 40 is shaped together with the decorative sheet body 2. After that, as shown in Figure 7, the unnecessary portion of the outer periphery of the shaped decorative sheet 1 is trimmed with the cutter 80.

[0040] Next, the shaped decorative sheet 1 is inserted into the molding die 70 (step S4). As shown in Figure 8, the molding die 70 has a first mold 71 and a second mold 72. The decorative sheet 1 is placed in a portion of the concave surface 711 that forms the cavity 73 of the first mold 71. Then, as shown in Figure 9, the first mold 71 and the second mold 72 are clamped together. As a result, a cavity 73 is formed between the first mold 71 and the second mold 72, and the decorative sheet 1 is inserted into the cavity 73.

[0041] In this state, injection molding is performed using the molding die 70 (step S5). Specifically, as shown in Figure 10, molten resin injected from the gate 74 provided in the second mold 72 fills the cavity 73. Then, the resin part 101 is formed by curing the molten resin in the molding die 70. The decorative sheet 1 is fixed to the surface of the resin when the resin hardens in the mold.

[0042] Subsequently, as shown in Figure 11, the first mold 71 and the second mold 72 are opened, and the molded product 100 is released from the molding die 70. This results in a molded product 100 having a resin part 101 and a decorative sheet 1.

[0043] A molded article 100 obtained in step S5 has a part of the surface of a resin portion 101 covered by the decorative sheet 1, and the other part of the surface of the resin portion 101 is exposed from the decorative sheet 1. The surface of the decorative sheet main body 2 is covered by a protective film 40. Therefore, it is not necessary to attach the protective film 40 to the surface of the decorative sheet main body 2 after injection molding.

[0044] Subsequently, the molded article 100 is coated (step S6). Specifically, coating is applied to the portion of the surface of the resin portion 101 exposed from the decorative sheet 1. At this time, the surface of the decorative sheet main body 2 is covered by the protective film 40. Therefore, adhesion of coating material to the surface of the decorative sheet main body 2 can be prevented. Accordingly, it is possible to prevent the pattern and color tone provided by the design layer 20 from being impaired by the coating material. Moreover, even when the surface of the top layer 30 has fine irregularities that exhibit a matte texture, it is also possible to prevent such texture from being impaired by the coating material.

[0045] Thereafter, the protective film 40 is peeled off from the decorative sheet main body 2 (step S7). In this way, the molded article 100 in which a part of the surface is decorated by the decorative sheet 1 and the other part is coated can be obtained.

[0046] <2. Modifications> Although one embodiment has been described above, the present disclosure is not limited to the above embodiment.

[0047] In the above embodiment, the decorative sheet 1 is shaped. However, the decorative sheet 1 may also be used without being shaped. In addition, the "decorative sheet" of the present invention may be unshaped or shaped.

[0048] In addition, in the above embodiment, the decorative sheet 1 covers a part of the surface of the molded article 100. However, the decorative sheet 1 may also cover the entire surface of the molded article 100. Regardless of whether the resin portion 101 is coated or not, since the decorative sheet 1 includes the protective film 40 that covers the surface of the decorative sheet main body 2, the step of attaching the protective film 40 to the surface of the decorative sheet main body 2 after injection molding can be omitted.

[0049] Furthermore, the elements appearing in the above embodiments and modifications may be combined or partially deleted to the extent that no inconsistencies arise. In addition, known elements may be added to the configurations appearing in the above embodiments and modifications as appropriate.

[0050] 1: Decorative sheet 2: Decorative sheet body 10: Backer layer 20: Design layer 21: Adhesive layer 22: Pattern layer 23: Release layer 30: Top layer 40: Protective film 70: Molding die 71: First mold 72: Second mold 73: Cavity 74: Gate 80: Cutter 90: Heater 100: Molded product 101: Resin part 711: Concave surface

Claims

1. A decorative sheet to be inserted into the cavity of a molding die, comprising: a backer layer; a design layer covering the surface of the backer layer; a top layer covering the surface of the design layer; and a peelable protective film covering the surface of the top layer.

2. The decorative sheet according to claim 1, which is shaped into a three-dimensional form.

3. The decorative sheet according to claim 1, wherein the melting point of the protective film is 140°C or higher.

4. The decorative sheet according to claim 1, wherein the protective film is capable of stretching by 120% or more in the direction along its surface without tearing.

5. The decorative sheet according to claim 1, wherein the top layer is formed from a mixed resin containing PVDF (polyvinylidene fluoride) and PMMA (polymethyl methacrylate), and the mass percentage concentration of PVDF on the protective film side of the top layer is greater than the mass percentage concentration of PMMA.

6. The decorative sheet according to claim 5, wherein the mass percentage concentration of PMMA on the design layer side of the top layer is greater than the mass percentage concentration of PVDF.

7. A molded article comprising a decorative sheet according to any one of claims 1 to 6 and a resin part, wherein a portion of the surface of the resin part is covered by the decorative sheet, and the other portion of the surface of the resin part is exposed from the decorative sheet.

8. A method for manufacturing a molded article, comprising: a) the step of manufacturing a decorative sheet having a backer layer, a design layer covering the surface of the backer layer, a top layer covering the surface of the design layer, and a protective film covering the surface of the top layer; b) the step of inserting the decorative sheet into the cavity of a molding die; and c) the step of filling the cavity with molten resin and curing it to obtain a molded article comprising the decorative sheet and a resin part.

9. The manufacturing method according to claim 8, wherein the molded product obtained by step c) has a portion of the surface of the resin part covered by the decorative sheet, and the other portion of the surface of the resin part exposed from the decorative sheet.

10. The manufacturing method according to claim 9, further comprising: d) a step of applying paint to the portion of the surface of the resin part exposed from the decorative sheet after step c); and e) a step of peeling the protective film from the top layer after step d).

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