Method for producing molded body and method for molding laminated sheet

Abstract

This laminated sheet is obtained by laminating a base material and a functional film that has a smaller thickness than the base material. This method for producing a molded body includes a step for thermoforming a laminated sheet so that at least one curved surface is formed, the curved surface being recessed from the functional film-side surface of the laminated sheet toward the surface on the reverse side from the functional film. In the thermoforming step, the laminated sheet is molded in a state in which the tensile strain and the compressive strain of the functional film satisfy the relationship of formula (i) in a portion where the radius R of curvature of the functional film-side surface in at least one curved surface is minimum.　(i): |tensile strain| ≥ |compressive strain|

Description

Method for manufacturing a molded article and method for molding a laminated sheet

[0001] The present invention relates to a method for manufacturing a molded article and a method for molding a laminated sheet.

[0002] It is known that a molded body can be obtained by thermoforming a laminated sheet in which two or more layers are stacked (for example, Japanese Patent Application Publication No. 2006-341595 (Patent Document 1)).

[0003] Japanese Patent Publication No. 2006-341595

[0004] In molded products made from laminated sheets, minute wrinkles and other defects sometimes occurred in the layers constituting the laminated sheets, resulting in appearance defects.

[0005] This disclosure aims to provide a method for manufacturing a molded article in which the occurrence of wrinkles is suppressed, and a method for molding a laminated sheet that can suppress the occurrence of wrinkles.

[0006] The present disclosure is a method for manufacturing a molded article of a laminated sheet, comprising: a method for manufacturing a molded article by thermoforming a laminated sheet, wherein the laminated sheet comprises a base material and a functional film having a thickness less than that of the base material; the manufacturing method includes a step of thermoforming the laminated sheet such that at least one concave curved surface is formed from the surface of the laminated sheet on the functional film side toward the surface opposite to the functional film; and the thermoforming step involves molding the laminated sheet in such a state that the tensile strain and compressive strain of the functional film satisfy the following equation (i) at the portion where the radius of curvature R of the functional film side surface of at least one of the curved surfaces is minimized: |Tensile Strain| ≥ |Compressive Strain| (i) [In equation (i), |Tensile Strain| represents the absolute value of the tensile strain in the functional film, and |Compressive Strain| represents the absolute value of the compressive strain in the functional film.]

[0007] The present disclosure's method for forming a laminated sheet comprises a laminated base material and a functional film having a thickness less than that of the base material, and the forming method includes a step of thermoforming the laminated sheet such that at least one concave curved surface is formed from the surface of the laminated sheet on the functional film side toward the surface opposite to the functional film, and the thermoforming step is to form the laminated sheet such that the tensile strain and compressive strain of the functional film satisfy the following equation (i) at the portion where the radius of curvature R of the functional film side surface of at least one of the curved surfaces is smallest: |Tensile Strain| ≥ |Compressive Strain| (i) [In equation (i), |Tensile Strain| represents the absolute value of the tensile strain in the functional film, and |Compressive Strain| represents the absolute value of the compressive strain in the functional film.]

[0008] According to the method for manufacturing a molded article of this disclosure, a molded article in which the occurrence of wrinkles is suppressed can be manufactured. According to the method for molding a laminated sheet of this disclosure, a laminated sheet can be molded while suppressing the occurrence of wrinkles.

[0009] This is a schematic cross-sectional view showing an example of a laminated sheet. This is a schematic cross-sectional view showing an example of a molded article. This is a schematic cross-sectional view illustrating an example of a method for manufacturing a molded article. This is a schematic cross-sectional view illustrating another example of a method for manufacturing a molded article. This is a schematic cross-sectional view illustrating yet another example of a method for manufacturing a molded article.

[0010] Embodiments of the present invention will be described below with reference to the drawings. In this specification and drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions may not be repeated. In this specification, numerical ranges such as "m to n" include upper and lower limits unless otherwise specified, and represent a numerical range of "m or more and n or less".

[0011] <Method for Manufacturing Molded Articles> The method for manufacturing molded articles in this embodiment (hereinafter also referred to as "this method") is a method for manufacturing molded articles by thermoforming laminated sheets.

[0012] (Laminated Sheet) Figure 1 is a schematic cross-sectional view showing an example of a laminated sheet. As shown in Figure 1, the laminated sheet 10 consists of a base material 12 and a functional film 11 which is thinner than the base material 12. Therefore, it is preferable that the center of the laminated sheet 10 in the thickness direction is located on the base material 12.

[0013] The laminated sheet 10 shown in Figure 1 has a functional film 11 on one side of the base material 12, but the laminated sheet 10 may have functional films 11 on both sides of the base material 12. The functional films 11 arranged on both sides of the base material 12 may be functional films 11 having the same function, or functional films 11 having different functions. In the case where the laminated sheet 10 has functional films 11 on both sides of the base material 12, the thickness of each of the two functional films 11 arranged on both sides of the base material 12 will be smaller than the thickness of the base material 12, but the thicknesses of the two functional films 11 may be the same, or they may be different.

[0014] The functional film 11 may be disposed on at least one surface of the laminated sheet 10, or one surface of the laminated sheet 10 may be the functional film 11. The functional film 11 may be disposed on both surfaces of the laminated sheet 10. If the functional film 11 is not disposed on the surface of the laminated sheet 10, the surface of the laminated sheet 10 may be another layer laminated on the functional film 11, rather than the functional film 11. If the surface of the laminated sheet 10 is another layer instead of the functional film 11, it is preferable to select the thickness of the other layer and the thickness of the base material 12 such that the center of the laminated sheet 10 in the thickness direction lies on the base material 12.

[0015] In the laminated sheet 10, it is preferable that the base material 12 and the functional film 11 are laminated with a laminating layer (not shown) that bonds the base material 12 and the functional film 11 together. In this case, it is preferable that the laminating layer is in direct contact with both the base material and the functional film.

[0016] The bonding layer may be an adhesive layer or a tack layer, but an adhesive layer is preferred. The bonding layer can be formed using known adhesives and tacks. The bonding layer may be an adhesive layer formed using, for example, an epoxy adhesive. The thickness of the bonding layer is preferably less than the thickness of the base material 12, and more preferably less than the thickness of the functional film 11.

[0017] (Base material) The base material 12 is preferably a resin base material, and more preferably a transparent resin base material. The resin base material is preferably a thermoplastic resin base material. Examples of resin base materials include polycarbonate base materials; thermoplastic polyester base materials formed from polyester such as polyethylene terephthalate, polybutylene terephthalate, or polyethylene naphthalate; polyolefin base materials formed from polypropylene or chain polyolefins such as ethylene vinyl acetate, or cyclopolyolefins such as norbornene; polyamide base materials formed from polyamides such as nylon 6, nylon 11, nylon 12, and nylon 66; polyimide base materials; polyamide-imide base materials; polyethersulfone base materials; polyphenyl ether base materials; polyarylate base materials; polyetheretherketone base materials; polyetherketoneketone base materials; polyvinyl chloride base materials; styrene-based resin base materials formed from polystyrene, etc.; phenoxy resin base materials; (meth)acrylic resin base materials, etc. The resin base material is preferably a polycarbonate base material.

[0018] The base material 12 may have a single-layer structure or a multi-layer structure, but a single-layer structure is preferred.

[0019] The thickness of the base material 12 is not limited as long as it is greater than the thickness of the functional film 11. The thickness of the base material 12 may be, for example, 0.1 to 50.0 mm, 0.5 to 40.0 mm, 1.0 to 30.0 mm, 2.0 to 20.0 mm, or 5.0 to 12.0 mm.

[0020] The tensile modulus of the base material 12 may be less than, greater than, or the same as the tensile modulus of the functional film 11, but it is preferable that it be less than the tensile modulus of the functional film 11. The tensile modulus of the base material 12 is, for example, 800 to 8000 N / mm². ２ The range is 1000 to 6000 N / mm ２ It may also be 1200 to 5000 N / mm ２ It may also be 1500-4000 N / mm ２ It may also be 2000-3000 N / mm ２ This may also be the case. The tensile modulus of the base material 12 can be measured at 23±2℃ in accordance with JIS K 7161:2014, as described in the examples below.

[0021] It is preferable that the product of the thickness of the base material 12 and its tensile modulus is greater than the product of the thickness of the functional film 11 and its tensile modulus. The product of the thickness of the base material 12 and its tensile modulus is, for example, 0.1 to 300 kN / mm, may be 0.5 to 200 kN / mm, 1.0 to 100 kN / mm, 3.0 to 80 kN / mm, 5.0 to 50 kN / mm, or 8.0 to 40 kN / mm.

[0022] (Functional Films) Examples of functional films 11 include one or more selected from the group consisting of heat-reflective films, anti-fog films, anti-glare films, hard-coat films, conductive films, antistatic films, anti-fouling films, decorative films, light-adjusting films, polarizing films, visible light-scattering films, projection films, light-emitting films, electric heating films, anti-reflective films, perovskite solar cell films, and antenna films. Known films can be used for these functional films 11.

[0023] The functional film 11 may have a single-layer structure or a multilayer structure. The functional film 11 may be a single-layer resin film, a laminated film formed by bonding two or more resin films together, or it may have a multilayer structure of two or more layers on a support film, with a functional layer that performs the function of the functional film 11 as described above, or it may have a multilayer structure in which two or more functional layers are laminated. The functional film 11 may be a film in which two or more functional layers having two or more different functions are laminated.

[0024] The functional film 11 preferably has a heat-reflective layer, and more preferably has a heat-reflective layer on a support film.

[0025] A heat-reflective film may, for example, have a support film and a heat-reflective layer formed on the support film. The heat-reflective layer may be a layer formed by alternately laminating two or more layers with different refractive indices. The two or more layers with different refractive indices may be layers formed by vapor deposition of metal or metal oxide, or layers formed from organic materials.

[0026] A hard coat film may have, for example, a support film and a hard coat layer formed on the support film. The hard coat layer can be formed, for example, by applying a hard coat composition onto the support film and drying and curing it.

[0027] The functional film 11 may have, for example, a heat-reflective layer and a hard coat layer. In this case, the heat-reflective film and the hard coat film may be laminated, or the hard coat layer may be formed on the outermost surface of the heat-reflective layer of the heat-reflective film.

[0028] The thickness of the functional film 11 is, for example, 1 to 500 μm, and may be 5 to 400 μm, may be 10 to 300 μm, may be 30 to 200 μm, or may be 50 to 100 μm. The thickness of the functional film 11 refers to the total thickness including the support film and the functional layer. When the functional film 11 is a laminated film formed by laminating two or more resin films, it refers to the total thickness of the laminated film including the two or more resin films and the lamination layer for laminating the resin films.

[0029] The tensile elastic modulus of the functional film 11 is, for example, 1000 to 8000 N / mm ２ and may be 2000 to 7000 N / mm ２ and may be 3000 to 6000 N / mm ２ and may be 4000 to 5000 N / mm ２ and may be 2000 to 3000 N / mm ２ and may be 2000 to 3000 N / mm. The above tensile elastic modulus of the functional film 11 may be the tensile elastic modulus in any direction. For example, the above tensile elastic modulus of the functional film 11 may be the tensile elastic modulus in the MD direction, or may be the tensile elastic modulus in the TD direction perpendicular to the MD direction. However, it is preferable that the larger of the tensile elastic moduli in the MD direction and the TD direction is within the above range. The tensile elastic modulus of the functional film 11 can be measured in accordance with JIS K 7161:2014 at 23 ± 2°C as described in the examples below.

[0030] The product of the thickness and the tensile elastic modulus of the functional film 11 is, for example, 0.001 to 4.0 kN / mm, and may be 0.005 to 2.0 kN / mm, may be 0.01 to 1.0 kN / mm, may be 0.05 to 0.80 kN / mm, may be 0.10 to 0.60 kN / mm, or may be 0.20 to 0.50 kN / mm. The product of the thickness and the tensile elastic modulus of the functional film 11 may be within the range of the product of the larger of the tensile elastic moduli in the MD direction and the TD direction of the functional film 11 and the thickness.

[0031] (Molded body) Figure 2 is a schematic cross-sectional view showing an example of a molded body. The molded body 20 manufactured by this method has at least one curved surface 22 formed by thermoforming the laminated sheet 10. The curved surface 22 is concave from the surface of the laminated sheet 10 on the functional film 11 side toward the surface on the opposite side of the functional film 11 (also called the "anti-functional film side"). The shape of the molded body 20 is not particularly limited as long as it has a curved surface 22, and may have one curved surface 22 or two or more curved surfaces 22.

[0032] At least one curved surface 22 of the molded body 20 may have flat portions 25 at both ends of a recess, as shown in Figure 2, for example, and may have one flat portion 25, a convex R portion 26, a concave R portion 27, a concave flat portion 28, a concave R portion 27, a convex R portion 26, and the other flat portion in this order. In the molded body 20 having the curved surface 22 shown in Figure 2, the portion where the radius of curvature R on the functional film 11 side of the curved surface 22 is smallest is located in the concave R portion 27 (described later).

[0033] The molded body 20 may be a roof member that constitutes the roof of a vehicle such as an automobile. In the case of a molded body 20 that is a roof member, it is preferable that the functional film 11 is positioned on the outer surface side of the roof member of the vehicle, rather than on the base material 12. The molded body 20 that is a roof member may have a shape (a so-called pagoda shape) in which the central part in the width direction of the vehicle roof is recessed to form a recess, as shown in Figure 2, for example. The width direction of the vehicle roof is the direction perpendicular to the front-rear direction of the vehicle and perpendicular to the up-down direction of the vehicle.

[0034] (Manufacturing Method (1)) Manufacturing Method (1), which is an example of this manufacturing method, will be described below. Figure 3 is a schematic cross-sectional view illustrating an example of a method for manufacturing a molded body (Manufacturing Method (1)). Manufacturing Method (1) is a method for manufacturing a molded body 20 using the laminated sheet 10 described above. Manufacturing Method (1) includes a step of thermoforming the laminated sheet 10 such that at least one concave curved surface 22 is formed from the functional film 11 side surface of the laminated sheet 10 toward the non-functional film side surface. The thermoforming step involves molding the laminated sheet 10 in a state where the tensile strain and compressive strain of the functional film 11 satisfy the relationship of the following formula (i) at the portion where the radius of curvature R of the functional film 11 side surface of at least one curved surface 22 is minimized (hereinafter also referred to as the "minimum R portion"). |Tensile strain| ≥ |Compressive strain| (i) [In equation (i), |Tensile strain| represents the absolute value of the tensile strain in the functional film 11, and |Compressive strain| represents the absolute value of the compressive strain in the functional film 11.]

[0035] In this specification, the minimum portion of R is the portion of the laminated sheet 10 on the functional film 11 side of the curved surface 22 that has the minimum radius of curvature on the functional film 11 surface (the surface opposite to the substrate 12).

[0036] The tensile strain [%] applied to the functional film 11 is the strain generated inside the functional film 11 at the minimum R portion as it is stretched when the laminated sheet 10 is deformed to form a curved surface 22. Tensile strain is expressed as a positive value. The compressive strain [%] applied to the functional film 11 is the strain generated inside the functional film 11 at the minimum R portion as it is compressed when the laminated sheet 10 is deformed to form a curved surface 22. Compressive strain is expressed as a negative value.

[0037] In this specification, the compressive strain [%] at the minimum portion of R in the functional film 11 is a theoretical value calculated by the following formula (x). [In formula (x), ε represents the compressive strain [%] at the minimum portion of R on the curved surface 22 of the molded body 20 (the portion where the radius of curvature R of the surface on the functional film 11 side is minimized), θ is the central angle [°] of the first sector assuming a first sector with an arc on the surface opposite to the base material 12 of the functional film 11 at the minimum portion of the above R, and R ｏｕｔ is the arc length [mm] of the second sector having the same central angle as the first sector and with an arc on the surface on the anti-functional film side of the laminated sheet 10 (the side opposite to the surface on the functional film 11 side of the laminated sheet 10) at the minimum portion of the above R, and t is the thickness [mm] of the minimum portion of the above R. ]

[0038] Each parameter in formula (x) is determined in the cross-section of the curved surface 22 of the molded body 20. In formula (x), it is assumed that the neutral axis at the minimum portion of R is at the position of the center in the thickness direction of the minimum portion of R. The thickness of the minimum portion of R represented by t in formula (x) is calculated as the thickness of the laminated sheet 10.

[0039] In this specification, the tensile strain [%] at the minimum portion of R in the functional film 11 is the value obtained by subtracting the absolute value of the compressive strain ε calculated by formula (x) from the strain of the minimum portion of R of the functional film 11 in the molded body 20. The strain of the minimum portion of R is a value calculated by applying the initial line length L0 and the post-formed line length L1 of the minimum portion of R measured using a three-dimensional measuring device to the formula {(L1 - L0) / L0} × 100. As the three-dimensional measuring device, for example, LJ-X8000 manufactured by Keyence Corporation can be used.

[0040] As described above, the conditions for forming the laminated sheet 10 in a state where the tensile strain and compressive strain of the functional film 11 satisfy the relationship of the following formula (i) can be set as follows, for example. The above conditions may be set by determining the strain at the minimum portion of R of the functional film in the step of thermoforming the molded body 20 using the above-described apparatus and comparing the determined strain with the compressive strain ε represented by the formula (x). Alternatively, the above conditions may be set so that a tensile strain equal to or greater than the absolute value of the compressive strain ε can be imparted to the functional film 11 based on the compressive strain ε represented by the formula (x). These conditions can be adjusted, for example, by the magnitude of the tensile force applied to the functional film 11 (described later).

[0041] When forming two or more curved surfaces 22 on the laminated sheet 10 by the thermoforming step of the manufacturing method (1), the laminated sheet 10 may be formed in a state where the relationship of the formula (i) is satisfied at the minimum portion of R of at least one curved surface 22, or the laminated sheet 10 may be formed in a state where the relationship of the formula (i) is satisfied at the minimum portion of R of all the curved surfaces 22.

[0042] When thermoforming is performed so that the curved surface 22 is formed on the laminated sheet 10, the absolute value of the tensile strain of the functional film 11 may become smaller than the absolute value of the compressive strain of the functional film 11. Since the functional film 11 is thinner and more likely to deform than the base material 12, when the absolute value of the tensile strain of the functional film 11 is smaller than the compressive strain, wrinkles are likely to occur in the functional film 11. At the minimum portion of R when the curved surface 22 is formed on the laminated sheet 10, the compressive strain tends to increase, and wrinkles are likely to occur in the functional film 1. When wrinkles occur in the functional film 11, depending on the type of the functional film, appearance defects such as color unevenness may occur. According to the manufacturing method (1), since the laminated sheet 10 is formed in a state where the functional film 11 satisfies the relationship of the formula (i) at the minimum portion of R of the curved surface 22, it is possible to suppress the occurrence of wrinkles in the functional film 11 during molding.

[0043] The absolute value of the tensile strain at the minimum R portion of the functional film 11 may be the same as the absolute value of the compressive strain, or it may be greater than the absolute value of the compressive strain. If the absolute value of the tensile strain is greater than the absolute value of the compressive strain, the difference between the absolute value of the tensile strain and the absolute value of the compressive strain may be adjusted according to the type of functional film 11 and the material used to form the functional film 11. The difference between the absolute value of the tensile strain and the absolute value of the compressive strain at the minimum R portion of the functional film 11 (|tensile strain| - |compressive strain|) may be, for example, greater than 0% and 10% or less, and may be 0.1 to 8%, 0.2 to 5%, 0.5 to 4%, or 1 to 3%.

[0044] If the tensile strain at the minimum radius of the functional film 11 becomes too large, while wrinkles in the functional film 11 can be suppressed, cracks may occur in the functional layer of the functional film 11. Also, depending on the type of functional film 11, the color tone of the molded body 20 may change. Therefore, it is preferable that the absolute value of the tensile strain be such that, when forming the curved surface 22 on the laminated sheet 10, cracks in the layers constituting the functional film 11 at the minimum radius and changes in the color tone of the molded body 20 are suppressed.

[0045] The thermoforming process can be a process of thermoforming by hot press molding. In this case, the thermoforming process involves pressing the laminated sheet 10 between a concave mold 35 and a convex mold 36 to form a curved surface 22 (Figure 3(c)). The concave mold 35 has a recess that can accommodate the convex portion of the convex mold 36. By sandwiching the laminated sheet 10 between the recess of the concave mold 35 and the convex portion of the convex mold 36, a curved surface 22 can be formed.

[0046] If the thermoforming process is hot press molding, it is preferable to include a step of holding the laminated sheet 10 between the concave mold 35 and the convex mold 36 before the thermoforming process, such that the functional film 11 side faces the convex mold 36 (Figure 3(a)). In the holding step, the laminated sheet 10 may be held between the concave mold 35 and the convex mold 36 by gripping the end of the laminated sheet 10 with a clamp 31. By arranging the laminated sheet 10 so that the functional film 11 side faces the convex mold 36, a concave curved surface 22 can be formed in the thermoforming process from the functional film 11 side toward the non-functional film side.

[0047] The manufacturing method (1) may include a step of heating and softening the laminated sheet 10 before or after the holding step. The softening of the laminated sheet 10 by heating may be performed either before or after placing the laminated sheet 10 between the concave mold 35 and the convex mold 36, or it may be performed both times.

[0048] The thermoforming process may involve sandwiching the laminated sheet 10 between a concave mold 35 and a convex mold 36 and holding it in a press-formed state for a predetermined time. After press forming, the press between the concave mold 35 and the convex mold 36 is released, and the molded body 20 obtained by forming the laminated sheet 10 is removed and cooled.

[0049] In manufacturing method (1), for example, as shown in Figure 3, the laminated sheet 10 held in the holding step (Figure 3(a)) and the concave mold 35 are moved relative to each other, and the concave mold 35 is pressed into the laminated sheet 10 to apply tensile strain to the functional film 11 (Figure 3(b)), and then the thermoforming step is performed to press-form the laminated sheet 10 and form a curved surface 22 (Figure 3(c)). From the start of pressing the concave mold 35 into the laminated sheet 10 until the laminated sheet is press-formed by the concave mold 35 and the convex mold 36, it is preferable to hold the ends of the laminated sheet 10 with clamps 31. This makes it possible to apply tensile force to the functional film 11 by pressing the concave mold 35 into the laminated sheet 10.

[0050] As described above, the concave mold 35 is pressed into the laminated sheet 10 from the base material 12 side, and tensile strain is generated in the functional film 11 by adjusting the amount of pressing at this time. By adjusting the magnitude of this tensile strain so that the functional film 11 satisfies the relationship of equation (i) when the laminated sheet 10 is press-molded, a molded body can be obtained in which the occurrence of wrinkles at the minimum part of R is suppressed. By adjusting the amount of pressing as described above, the occurrence of defects such as cracks in the layers constituting the functional film 11 and changes in the color tone of the molded body can also be suppressed at the minimum part of R.

[0051] In manufacturing method (1), after press-molding the laminated sheet 10 as described above, it is preferable to apply tensile force to the functional film 11 when cooling the molded body 20, for example, by gripping the end of the laminated sheet 10 with a clamp 31. Preferably, the tensile force applied when cooling the molded body 20 is applied from the time of molding until the molded body 20 is cooled to a temperature below the glass transition temperature (Tg) of the functional film 11. This suppresses the occurrence of wrinkles at the smallest part of R, and makes it possible to obtain a molded body in which defects such as cracks in the layers constituting the functional film 11 and changes in the color tone of the molded body are suppressed. It is also preferable that the functional film 11 satisfies the relationship of formula (i) in the molded body 20 manufactured by manufacturing method (1).

[0052] The relative movement between the laminated sheet 10 and the concave mold 35 may be performed by fixing one of the laminated sheet 10 and the concave mold 35 and moving the other, or by moving both. The concave mold 35 can usually press the laminated sheet 10 into a position other than the recessed portion.

[0053] When press-forming the laminated sheet 10, the concave mold 35, the laminated sheet 10, and the convex mold 36 can be moved relative to each other. This relative movement can be performed, for example, by moving the convex mold 36 closer to the laminated sheet 10 and the concave mold 35 without moving the concave mold 35, which is in a state of pressing the laminated sheet 10 into it, or by moving the concave mold 35 and the laminated sheet 10 closer to the convex mold 36 while maintaining the state of the concave mold 35 pressing the laminated sheet 10 into it, without moving the convex mold 36. Alternatively, the relative movement can be performed by moving the concave mold 35, the laminated sheet 10, and the convex mold 36 individually.

[0054] (Manufacturing Method (2)) Another example of the present manufacturing method, manufacturing method (2), will be described. Figure 4 is a schematic cross-sectional view illustrating another example of the manufacturing method of a molded body (manufacturing method (2)). Manufacturing method (2), like manufacturing method (1), is a method of manufacturing a molded body 20 using the laminated sheet 10 described above, and includes a step of thermoforming the laminated sheet 10 such that at least one concave curved surface 22 is formed from the functional film 11 side surface of the laminated sheet 10 toward the non-functional film side surface. Since manufacturing method (2) also includes a step of thermoforming by hot press molding, manufacturing method (2), like manufacturing method (1), in the thermoforming step, forms the laminated sheet 10 such that the tensile strain and compressive strain of the functional film 11 at the portion where the radius of curvature R of the surface on the functional film 11 side of at least one curved surface 22 is smallest (the portion of R smallest) satisfies the relationship of formula (i) above. The thermoforming step forms the curved surface 22 by pressing the laminated sheet 10 between a concave mold 35 and a convex mold 36 (Figure 4(c)). Prior to the thermoforming step, the step includes holding the laminated sheet 10 between the concave mold 35 and the convex mold 36 so that the functional film 11 side faces the convex mold 36 (Figure 4(a)). These methods and steps have been described above, so no further explanation will be given.

[0055] Manufacturing method (2) may include the softening step described above, and may be held in the press-molded state for a predetermined time, or the molded body 20 may be removed after press molding and the molded body may be cooled. These steps and methods are as described above and will not be repeated.

[0056] In manufacturing method (2), for example, as shown in Figure 4, the laminated sheet 10 held in the holding step (Figure 4(a)) is subjected to a tensile force (Figure 4(b)), and then the thermoforming step is carried out to press-form the laminated sheet 10 (Figure 4(c)). The tensile force to the laminated sheet 10 can be applied by gripping the end of the laminated sheet 10 with a clamp 31 and pulling the laminated sheet 10 to stretch it using the clamp 31.

[0057] As described above, a tensile force is applied to the laminated sheet 10, causing tensile strain in the functional film 11. By adjusting the tensile force applied to the laminated sheet 10 so that the functional film 11 satisfies the relationship of equation (i) when the laminated sheet 10 is press-molded, a molded body can be obtained in which the occurrence of wrinkles at the minimum part of R is suppressed. By adjusting the tensile force applied to the laminated sheet 10, as explained in manufacturing method (1), the occurrence of defects such as cracking of the layers constituting the functional film 11 and changes in the color tone of the molded body at the minimum part of R can also be suppressed.

[0058] In manufacturing method (2), as in manufacturing method (1), it is preferable that the functional film 11 satisfies the relationship of formula (i) when the molded body 20 is cooled after press molding of the laminated sheet 10, and it is also preferable that the functional film 11 satisfies the relationship of formula (i) in the molded body 20. A method for ensuring that the functional film 11 satisfies the relationship of formula (i) when the molded body 20 is cooled is the method described in manufacturing method (1).

[0059] When press-forming the laminated sheet 10, the concave mold 35, the laminated sheet 10, and the convex mold 36 can be moved relative to each other. This relative movement can be, for example, by moving the concave mold 35 and the convex mold 36 closer to the laminated sheet 10 without moving the laminated sheet 10, or by fixing the position of one of the concave mold 35 and the convex mold 36 and moving the other mold and the laminated sheet 10 closer to the fixed mold.

[0060] (Manufacturing Method (3)) Manufacturing Method (3), which is yet another example of the present manufacturing method, will be described. Figure 5 is a schematic cross-sectional view illustrating yet another example of the manufacturing method of a molded body (Manufacturing Method (3)). Manufacturing Method (3), like Manufacturing Methods (1) and (2), is a method of manufacturing a molded body 20 using the laminated sheet 10 described above, and includes a step of thermoforming the laminated sheet 10 so that at least one concave curved surface 22 is formed from the functional film 11 side surface of the laminated sheet 10 toward the non-functional film side surface. Manufacturing Method (3), like Manufacturing Methods (1) and (2), in the thermoforming step, the laminated sheet 10 is molded such that the tensile strain and compressive strain of the functional film 11 at the portion where the radius of curvature R of the functional film 11 side surface of at least one curved surface 22 is minimized (the portion of R that is minimized) satisfy the relationship of formula (i) above. This method has been described above, so no further explanation will be given.

[0061] Manufacturing method (3) includes a step of thermoforming by vacuum forming. For example, as shown in Figure 5, the thermoforming step in manufacturing method (3) involves forming the laminated sheet 10 in close contact with the molding die 37. This forms a curved surface 22 on the laminated sheet 10 (Figure 5). In the thermoforming step, when the laminated sheet 10 is in close contact with the molding die 37, it is sufficient to ensure that the tensile strain and compressive strain of the functional film 11 satisfy the relationship of equation (i) above. In the thermoforming step of manufacturing method (3), for example, as shown in Figure 5, air is sucked from the space between the molding die 37 and the laminated sheet 10 using a suction pump such as a vacuum pump, and the space is reduced in pressure or under vacuum, thereby making the laminated sheet 10 in close contact with the molding die 37.

[0062] In manufacturing method (3), the laminated sheet 10 may be positioned facing the molding die 37 before the thermoforming step. In this case, for example, the end of the laminated sheet 10 can be gripped by the clamp 31 to bring the laminated sheet 10 and the molding die 37 facing each other. When manufacturing method (3) is carried out using the molding die 37 shown in Figure 5, the laminated sheet 10 should be held so that the recessed portion of the molding die 37 faces the side of the laminated sheet 10 opposite to the functional film 11 (the side facing the base material 12 in Figure 5).

[0063] As an example of a method for thermoforming the laminated sheet 10 using a molding die 37 so that the functional film 11 satisfies the relationship of formula (i) above, the following method can be used. The laminated sheet 10 is held by the clamp 31 as described above and brought facing the molding die 37. Then, while maintaining the grip of the laminated sheet 10 by the clamp 31, the laminated sheet 10 is brought into close contact with the molding die 37. The ends of the laminated sheet 10 are held by the clamp 31 so that tensile force is applied to the functional film 11 when the laminated sheet 10 is brought into close contact with the molding die 37. This makes it possible to generate tensile strain in the functional film 11 by bringing the laminated sheet 10 into close contact with the molding die 37. As a result, it becomes easier to mold the laminated sheet 10 so that the functional film 11 satisfies the relationship of formula (i) above, and it becomes easier to obtain a molded body in which the occurrence of wrinkles at the smallest part of R is suppressed.

[0064] By adjusting the tensile force applied to the functional film 11, as described in manufacturing methods (1) and (2), the occurrence of defects such as cracking of the layers constituting the functional film 11 and changes in the color tone of the molded body can be suppressed at the smallest part of R. The tensile force applied to the functional film 11 can be adjusted, for example, by the shape of the recess in the molding die 37, the magnitude of the tensile force applied to the laminated sheet 10 before it is brought into contact with the molding die 37, etc. When the laminated sheet 10 is gripped with the clamp 31 as described above, it is not necessary to apply tensile force to the laminated sheet 10 before it is brought into contact with the molding die 37, but it is also possible to apply tensile force.

[0065] Manufacturing method (3) may include a step of heating and softening the laminated sheet 10 before the thermoforming step. The softening of the laminated sheet 10 by heating may be performed either before or after positioning the laminated sheet 10 so as to face the molding die 37, or it may be performed both times.

[0066] In manufacturing method (3), as in manufacturing methods (1) and (2), it is preferable that the functional film 11 satisfies the relationship of formula (i) when the molded body 20 is cooled after press molding of the laminated sheet 10, and it is also preferable that the functional film 11 satisfies the relationship of formula (i) in the molded body 20. A method for ensuring that the functional film 11 satisfies the relationship of formula (i) when the molded body 20 is cooled is the method described in manufacturing method (1).

[0067] In the vacuum forming shown in Figure 5, a method for manufacturing the molded body 20 has been described in which the molding die 37 has a recessed portion, and the recessed portion of the molding die 37 faces the side of the laminated sheet 10 opposite to the functional film 11. However, the method is not limited to this. For example, a molding die having a convex portion may be used, and the laminated sheet 10 may be placed in the molding die such that the convex portion faces the side of the laminated sheet 10 that faces the functional film 11, and molded in close contact with the molding die. In this case, by adjusting the tensile force applied to the laminated sheet 10, etc., the functional film 11 can be made to satisfy the relationship of formula (i) when the laminated sheet 10 is in close contact with the molding die having a convex portion, thereby obtaining a molded body in which the occurrence of wrinkles at the minimum part of R is suppressed. Similarly, it is preferable that the functional film 11 satisfies the relationship of formula (i) when the molded body 20 is cooled after press molding of the laminated sheet 10, and also in the molded body 20.

[0068] <Method for forming a laminated sheet> The method for forming a laminated sheet according to this embodiment (hereinafter also referred to as "this forming method") is a method for forming a laminated sheet. This forming method is a method for forming the above-described laminated sheet 10 and includes a step of thermoforming the laminated sheet 10 such that at least one concave curved surface 22 is formed from the functional film 11 side surface of the laminated sheet 10 toward the non-functional film side surface. The thermoforming step forms the laminated sheet 10 in such a state that the tensile strain and compressive strain of the functional film 11 at the portion where the radius of curvature R on the concave functional film 11 side of at least one curved surface 22 is minimized (the portion of R that is minimized) satisfy the relationship of formula (i) above.

[0069] The specific method of this molding method is the same as the method of thermoforming the laminated sheet described in manufacturing methods (1) to (3) above, so the explanation will not be repeated. This molding method is preferably carried out by the method of thermoforming the laminated sheet described in manufacturing method (1) or (2).

[0070] The present invention will be described in more detail below with reference to examples and comparative examples. [Example 1] (Preparation of laminated sheet) A sheet-shaped polycarbonate substrate was prepared as the base material, with a rectangular shape in plan view of 0.395 m in length and 0.4 m in width, and a thickness of 5 mm. The tensile modulus of the substrate, measured at 23 ± 2°C in accordance with JIS K 7161:2014, was 2200 N / mm². ２ That was all.

[0071] As a functional film, a heat-reflective film having a heat-reflective layer on a support film was prepared. The heat-reflective layer consisted of multiple layers of organic material. The thickness of the functional film was 77 μm. When the tensile modulus of the functional film was measured at 23 ± 2°C in accordance with JIS K 7161:2014, the tensile modulus in the MD direction was 4400 N / mm². ２ The tensile modulus in the TD direction is 5200 N / mm². ２ That was the case.

[0072] A functional film with a PC film was obtained by laminating a polycarbonate film (hereinafter also referred to as "PC film") to the heat-reflective layer side of a functional film via an epoxy adhesive. The support film side of this functional film with a PC film was then laminated to one surface of a substrate via an epoxy adhesive. Subsequently, a composition for forming a hard coat layer (hereinafter also referred to as "HC layer") was applied to the surface of the PC film and the other surface of the substrate, and the applied composition was cured to form an HC layer, which is a cured layer of acrylic resin, thereby obtaining a laminated sheet. The center of the laminated sheet in the thickness direction was located on the substrate 12. In this embodiment, the PC film and the HC layer are not included in the functional film.

[0073] (Preparation of molds) In order to mold the laminated sheet into a pagoda shape (a shape in which the central part in the width direction is recessed to form a recess) which is a type of roof member used in automobiles, a concave mold 35 and a convex mold 36, as shown in Figure 3, were prepared. The concave mold has flat parts at both ends of the recess in the width direction cross-section (cross-section shown in Figure 3) of the molded body obtained by molding the laminated sheet, and the recess has a convex R part, a recess R part, a recessed flat part, a recess R part, and a convex R part in this order from one flat part side to the other flat part side. The concave mold has the shape of the width direction cross-section described above in the central region in the planar direction of the laminated sheet and in the direction perpendicular to the width direction of the molded body (hereinafter also referred to as the "orthogonal direction"), and the depth of the recess gradually becomes shallower from the central region in the orthogonal direction toward the ends, and the end in the orthogonal direction has no recess formed. The convex mold has a convex part that can be fitted into the recess of the concave mold.

[0074] When the laminated sheet is formed using the concave and convex molds described above, with the functional film side of the laminated sheet facing the convex mold, a concave curved surface is formed from the functional film side of the laminated sheet toward the surface opposite the functional film. The portion of this curved surface where the radius of curvature R of the functional film surface is smallest (the portion with the minimum R) is the portion formed by the concave R portion of the concave mold. The portion of the functional film surface with the minimum R on the curved surface formed on the laminated sheet has a radius of curvature of 55 mmR.

[0075] (Preparation of molded body) After heating and softening the laminated sheet prepared above (softening step), the laminated sheet was set between a concave mold and a convex mold while its four sides were fixed with clamps to maintain a nearly horizontal position (holding step). At this time, the functional film side of the laminated sheet was placed facing the convex mold, and the width direction of the concave mold was aligned with the TD direction of the laminated sheet. The position where the clamped laminated sheet and the concave mold made contact was set as the 0 mm indentation position of the concave mold, and the concave mold was moved toward the laminated sheet and pressed until the indentation position of the concave mold was 20 mm. After that, the convex mold was moved toward the laminated sheet, and the laminated sheet was press-molded between the concave mold and the convex mold (thermoforming step) to obtain a molded body in the shape of a pagoda.

[0076] As described above, when forming the molded body, a three-dimensional measuring device (LJ-X8000, manufactured by Keyence Corporation) was used to measure the initial wire length L0 and the wire length L1 after molding at the minimum portion of the radius R on the functional film surface of the curved surface formed on the laminated sheet. These values ​​were then applied to the formula {(L1 - L0) / L0} × 100 to calculate the strain (hereinafter also referred to as "strain ε1") [%]. The compressive strain ε at the minimum portion of the radius R of the molded body was calculated based on the formula (x) described above, and the calculated value was taken as the compressive strain [%] at the minimum portion of the radius R. The value obtained by subtracting the absolute value of the compressive strain ε from the strain ε1 (ε1 - |ε|) was taken as the tensile strain [%]. As a result, the tensile strain was 6.6% and the compressive strain was -4.3%.

[0077] When the molded body was cut along the width direction (TD direction of the laminated sheet) at the central part of the concave mold in the direction perpendicular to the above, and the cross-section was observed with a microscope, no wrinkles were found in the functional film. Furthermore, when the appearance of the molded body was visually observed, no color unevenness or changes in color tone were observed.

[0078] [Example 2] A molded body formed into a pagoda shape was obtained in the same manner as in Example 1, except that the concave mold was pressed into the laminated sheet until the indentation depth of the concave mold reached 30 mm. When the laminated sheet was formed in this manner, the tensile strain and compressive strain applied to the functional film at the minimum portion of the radius R on the curved surface of the functional film formed on the laminated sheet were calculated using the procedure described in Example 1. The tensile strain was 8.0%, and the compressive strain was -4.3%.

[0079] When the cross-section of the molded body was observed using the procedure described in Example 1, no wrinkles were observed in the functional film. Furthermore, when the appearance of the molded body was visually inspected, no color unevenness was observed, but the molded body had a reddish tint.

[0080] [Example 3] A molded body formed into a pagoda shape was obtained in the same manner as in Example 1, except that the concave mold was pressed into the laminated sheet until the indentation depth of the concave mold reached 10 mm. When the laminated sheet was formed in this manner, the tensile strain and compressive strain applied to the functional film at the minimum portion of the radius R on the curved surface of the functional film formed on the laminated sheet were calculated using the procedure described in Example 1. The tensile strain was 4.6%, and the compressive strain was -4.3%.

[0081] When the cross-section of the molded body was observed using the procedure described in Example 1, no wrinkles were observed in the functional film. Furthermore, when the appearance of the molded body was visually inspected, no color unevenness or changes in color tone were observed.

[0082] [Comparative Example 1] A molded body formed into a pagoda shape was obtained in the same manner as in Example 1, except that the laminated sheet was not fixed on all four sides with clamps, the laminated sheet was set between a concave mold and a convex mold, and the laminated sheet was pressed by the concave mold and the convex mold. When the laminated sheet was formed in this way, the tensile strain and compressive strain applied to the functional film at the minimum part of the radius R on the curved surface of the functional film surface formed on the laminated sheet were calculated using the procedure described in Example 1, and the absolute value of the tensile strain was smaller than the absolute value of the compressive strain.

[0083] When the cross-section of the molded body was observed using the procedure described in Example 1, wrinkles were found in the functional film. Furthermore, visual inspection of the molded body's appearance revealed color unevenness, but no change in color tone was observed.

[0084] [Note] The exemplary embodiments described above will be understood by those skilled in the art to be specific examples of the following embodiments. (Embodiment 1) A method for manufacturing a molded article by thermoforming a laminated sheet, wherein the laminated sheet comprises a base material and a functional film having a thickness less than that of the base material, the manufacturing method includes a step of thermoforming the laminated sheet such that at least one concave curved surface is formed from the surface of the laminated sheet on the functional film side toward the surface opposite to the functional film, and the thermoforming step is to mold the laminated sheet in such a state that the tensile strain and compressive strain of the functional film satisfy the following equation (i) at the portion where the radius of curvature R of the functional film side surface of at least one of the curved surfaces is smallest. |Tensile strain| ≥ |Compressive strain| (i) [In equation (i), |Tensile strain| represents the absolute value of the tensile strain in the functional film, and |Compressive strain| represents the absolute value of the compressive strain in the functional film. (Aspect 2) The method for manufacturing a molded article according to Aspect 1, wherein the thermoforming step includes a step of holding the laminated sheet between the concave mold and the convex mold so that the functional film side faces the convex mold, prior to the thermoforming step. (Aspect 3) The method for manufacturing a molded article according to Aspect 2, wherein the thermoforming step is carried out while the functional film is subjected to tensile strain by moving the laminated sheet held in the holding step and the concave mold relative to each other and pressing the concave mold into the laminated sheet. (Aspect 4) The method for manufacturing a molded article according to Aspect 2, wherein tension is applied to the laminated sheet held in the holding step. (Aspect 5) The method for manufacturing a molded article according to any one of Aspects 1 to 4, wherein the substrate is a resin substrate. (Aspect 6) The method for manufacturing a molded article according to Aspect 5, wherein the resin substrate is a polycarbonate substrate. (Aspect 7) A method for manufacturing a molded article according to any one of aspects 1 to 6, wherein the functional film has a heat-reflective layer.(Aspect 8) A method for manufacturing a molded article according to any one of aspects 1 to 7, wherein the base material and the functional film are laminated with a laminating layer that bonds the base material and the functional film together. (Aspect 9) A method for manufacturing a molded article according to any one of aspects 1 to 8, wherein the molded article is a roof member of a vehicle, and the functional film is positioned on the outer surface side of the roof member of the vehicle, relative to the base material. (Aspect 10) A method for molding a laminated sheet, wherein the laminated sheet comprises a base material and a functional film having a thickness less than that of the base material, and the molding method includes a step of thermoforming the laminated sheet such that at least one concave curved surface is formed from the surface of the laminated sheet on the functional film side toward the surface opposite to the functional film, and the thermoforming step comprises molding the laminated sheet such that the tensile strain and compressive strain of the functional film satisfy the relationship of formula (i) below in the portion where the radius of curvature R of the functional film side surface of at least one of the curved surfaces is smallest. |Tensile strain| ≥ |Compressive strain| (i) [In formula (i), |Tensile strain| represents the absolute value of the tensile strain in the functional film, and |Compressive strain| represents the absolute value of the compressive strain in the functional film.] (Aspect 11) The method for forming a laminated sheet according to aspect 10, wherein the thermoforming step includes forming the curved surface by pressing the laminated sheet between a concave mold and a convex mold, and before the thermoforming step, the step includes holding the laminated sheet between the concave mold and the convex mold such that the functional film side faces the convex mold. (Aspect 12) The method for forming a laminated sheet according to aspect 11, wherein the thermoforming step is performed while the functional film is subjected to tensile strain by relatively moving the laminated sheet and the concave mold held in the holding step and pressing the concave mold into the laminated sheet. (Aspect 13) The method for forming a laminated sheet according to aspect 11, wherein the thermoforming step is performed while tension is applied to the laminated sheet held in the holding step.

[0085] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than the foregoing description, and all modifications are intended to be in the sense and scope equivalent to the claims.

[0086] 10 Laminated sheet, 11 Functional film, 12 Substrate, 20 Molded body, 22 Curved surface, 25 Flat section, 26 Convex R section, 27 Concave R section, 28 Concave flat section, 31 Clamp, 35 Concave mold, 36 Convex mold, 37 Molding mold.

Claims

1. A method for manufacturing a molded body by thermoforming a laminated sheet, wherein the laminated sheet comprises a base material and a functional film having a thickness less than that of the base material, the manufacturing method includes a step of thermoforming the laminated sheet such that at least one concave curved surface is formed from the surface of the laminated sheet on the functional film side toward the surface opposite to the functional film, and the thermoforming step is to mold the laminated sheet in such a state that the tensile strain and compressive strain of the functional film satisfy the following equation (i) at the portion where the radius of curvature R of the functional film side surface of at least one of the curved surfaces is smallest: |Tensile strain| ≥ |Compressive strain| (i) [In equation (i), |Tensile strain| represents the absolute value of the tensile strain in the functional film, and |Compressive strain| represents the absolute value of the compressive strain in the functional film.] 2. The method for manufacturing a molded article according to claim 1, wherein the thermoforming step includes forming at least one curved surface by press molding with the laminated sheet sandwiched between a concave mold and a convex mold, and before the thermoforming step, the step of holding the laminated sheet between the concave mold and the convex mold such that the functional film side faces the convex mold.

3. The method for manufacturing a molded article according to claim 2, wherein the laminated sheet held in the holding step and the concave mold are moved relative to each other, and the concave mold is pressed into the laminated sheet, thereby applying tensile strain to the functional film, and the thermoforming step is carried out while the functional film is in this state.

4. The method for manufacturing a molded article according to claim 2, wherein the thermoforming step is carried out while tension is applied to the laminated sheet held in the holding step.

5. The method for manufacturing a molded article according to any one of claims 1 to 4, wherein the base material is a resin base material.

6. The method for manufacturing a molded article according to claim 5, wherein the resin substrate is a polycarbonate substrate.

7. The method for manufacturing a molded article according to any one of claims 1 to 6, wherein the functional film has a heat-reflective layer.

8. The method for manufacturing a molded article according to any one of claims 1 to 7, wherein the substrate and the functional film are laminated with a laminating layer that bonds the substrate and the functional film together.

9. The method for manufacturing a molded article according to any one of claims 1 to 8, wherein the molded article is a roof member of a vehicle, and the functional film is disposed on the outer surface side of the roof member of the vehicle, relative to the base material.

10. A method for forming a laminated sheet, wherein the laminated sheet comprises a base material and a functional film having a thickness less than that of the base material, and the forming method includes a step of thermoforming the laminated sheet such that at least one concave curved surface is formed from the surface of the laminated sheet on the functional film side toward the surface opposite to the functional film, and the thermoforming step is to form the laminated sheet such that the tensile strain and compressive strain of the functional film satisfy the following relationship at the portion where the radius of curvature R of the functional film side surface of at least one of the curved surfaces is smallest: |Tensile strain| ≥ |Compressive strain| (i) [In equation (i), |Tensile strain| represents the absolute value of the tensile strain in the functional film, and |Compressive strain| represents the absolute value of the compressive strain in the functional film.] 11. The method for forming a laminated sheet according to claim 10, wherein the thermoforming step includes forming at least one curved surface by press forming the laminated sheet by sandwiching it between a concave mold and a convex mold, and before the thermoforming step, the step includes holding the laminated sheet between the concave mold and the convex mold such that the functional film side faces the convex mold.

12. The method for forming a laminated sheet according to claim 11, wherein the laminated sheet held in the holding step and the concave mold are moved relative to each other, and the concave mold is pressed into the laminated sheet, thereby applying tensile strain to the functional film, and the thermoforming step is performed.

13. The method for forming a laminated sheet according to claim 11, wherein the thermoforming step is performed while tension is applied to the laminated sheet held in the holding step.

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