Composite films, laminates, molded articles, vehicle exterior parts, and methods for manufacturing laminates.

Abstract

The objective is to provide a composite film that can reduce or prevent the occurrence of wrinkles and delamination (specifically, delamination of the composite film from the metal plate) when the composite film is heat-pressed onto a metal plate, and moreover, can reduce or prevent the occurrence of surface roughness of the paint substitute film during that process (i.e., when the composite film is heat-pressed onto the metal plate). The objective is also to provide laminates, molded products, and vehicle exterior parts. [Solution] A composite film 7 comprising a paint substitute film 8 and a protective film 9, wherein the difference between the sum of the 230°C shrinkage stresses of the paint substitute film 8 and the sum of the 230°C shrinkage stresses of the protective film 9 is 1.5 MPa or less in absolute value, and the difference between the sum of the 150°C heat shrinkage rates of the paint substitute film 8 and the sum of the 150°C heat shrinkage rates of the protective film 9 is 3.0% or less in absolute value.

Description

Technical Field

[0001] The present invention relates to a composite film, a laminate, a molded product, an automotive exterior part, and a method for producing a laminate.

Background Art

[0002] Automotive exterior parts, such as door panels, front fenders, roofs, back doors, hoods, etc., are painted. Spraying paint onto a metal plate, that is, spray painting, is generally performed for painting.

[0003] However, since the paint used in spray painting contains volatile organic compounds (VOCs), spray painting has a large environmental impact. Moreover, since spray painting is performed repeatedly, a large space is required for performing spray painting.

[0004] Instead of painting a metal plate, a method of laminating a paint replacement film on the metal plate has been proposed (see Patent Document 1). According to this, it is possible to omit spray painting.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] There is a case where a composite film including a paint replacement film and a protective film provided on the paint replacement film is thermocompression-bonded to a metal plate. When the composite film is thermocompression-bonded to the metal plate, wrinkles or peeling (specifically, peeling of the composite film from the metal plate) may occur.

[0007] The present invention aims to provide a composite film that can reduce or prevent the occurrence of wrinkles and delamination (specifically, delamination of the composite film from the metal plate) when a composite film is heat-pressed onto a metal plate, and that can also reduce or prevent the occurrence of surface roughness of the paint substitute film during the process (i.e., when the composite film is heat-pressed onto the metal plate). The present invention also aims to provide a laminate and a method for manufacturing the same. The present invention also aims to provide a molded product obtained by press-forming a laminate. The present invention also aims to provide a vehicle exterior part. [Means for solving the problem]

[0008] To solve this problem, the present invention comprises the configuration described in [1] below. [1] Paint replacement film and A composite film including a protective film, The aforementioned paint substitute film includes a biaxially oriented polyester film, a coloring layer, and a surface protective layer. At least the biaxially oriented polyester film, the colored layer, the surface protective layer, and the protective film are stacked in this order. The aforementioned coating substitute film has a first sum of the shrinkage stress in the TD direction and the shrinkage stress in the MD direction at 230°C of 0.3 MPa or more. The protective film has a second sum of the shrinkage stress in the TD direction and the shrinkage stress in the MD direction at 230°C of 0.3 MPa or more. The difference between the first sum and the second sum is 1.5 MPa or less in absolute value. The difference between the third sum and the fourth sum is 3.0% or less in absolute value. The third sum is the sum of the thermal shrinkage rate of the coating substitute film in the TD direction and the thermal shrinkage rate of the coating substitute film in the MD direction when the coating substitute film is heated at 150°C for 15 minutes. The sum of the fourth is the sum of the thermal shrinkage rate of the protective film in the TD direction and the thermal shrinkage rate of the protective film in the MD direction when the protective film is heated at 150°C for 15 minutes. Composite film. Here, the MD direction of the protective film is the direction determined by the paint substitute film. Specifically, the MD direction of the protective film refers to the direction that coincides with the MD direction of the paint substitute film among the directions included on the surface of the protective film (which can also be said to be the direction along the surface of the protective film). The TD direction of the protective film is the direction determined by the paint substitute film. Specifically, the TD direction of the protective film refers to the direction that coincides with the TD direction of the paint substitute film among the directions included on the surface of the protective film. Hereafter, the difference between the first sum and the second sum is sometimes referred to as the "shrinkage stress difference." The difference between the third sum and the fourth sum is sometimes called the "difference in thermal shrinkage coefficient."

[0009] [1] According to [1], since the paint substitute film contains a colored layer, the paint substitute film can be used to decorate or protect metal plates.

[0010] Furthermore, since the paint substitute film includes a surface protection layer, the colored layer can be protected by the surface protection layer.

[0011] Furthermore, since the composite film includes a protective film, the protective film can protect the paint-alternative film.

[0012] Furthermore, since the difference in shrinkage stress is 1.5 MPa or less in absolute value, and the difference in thermal shrinkage rate is 3.0% or less in absolute value, it is possible to prevent the occurrence of wrinkles when the composite film is heat-pressed onto the metal plate, and therefore, the occurrence of delamination (specifically, delamination of the composite film from the metal plate) can be reduced or prevented. This will be explained below. Since the difference in shrinkage stress is 1.5 MPa or less in absolute value, it is possible to avoid the shrinkage stress that may occur in the paint substitute film due to heat pressing being excessively large or excessively small compared to the shrinkage stress that may occur in the protective film due to heat pressing. Since the difference in thermal shrinkage rate is 3.0% or less in absolute value, it is possible to avoid the shrinkage of the paint substitute film during heat pressing being excessively large or excessively small compared to the shrinkage of the protective film during heat pressing. As a result, it is possible to prevent the occurrence of wrinkles when the composite film is heat-pressed onto the metal plate. Therefore, it is possible to avoid a reduction in the bonding area (specifically, the bonding area between the metal plate and the composite film) due to wrinkles. In other words, it is possible to avoid a decrease in adhesion strength with the metal plate due to wrinkles. Therefore, it is possible to reduce or prevent the occurrence of peeling of the composite film from the metal plate.

[0013] Furthermore, since the second sum (i.e., the sum of the 230°C shrinkage stress in the TD direction of the protective film and the 230°C shrinkage stress in the MD direction of the protective film) is 0.3 MPa or more, and the first sum (i.e., the sum of the 230°C shrinkage stress in the TD direction of the paint substitute film and the 230°C shrinkage stress in the MD direction of the paint substitute film) is 0.3 MPa or more, the occurrence of surface roughness in the paint substitute film when the composite film is heat-pressed onto the metal plate can be reduced or prevented. This will be explained below. Since the second sum is 0.3 MPa or more, the protective film can be prevented from melting at 230°C. Therefore, melting of the protective film during heat pressing can be avoided, and the occurrence of surface roughness in the paint substitute film due to the melting of the protective film can be avoided. Since the first sum is 0.3 MPa or more, the entire biaxially oriented polyester film can be prevented from melting at 230°C. Therefore, melting of the entire biaxially oriented polyester film during heat pressing can be avoided, and the occurrence of surface roughness in the paint substitute film due to the melting of the entire biaxially oriented polyester film can be avoided. As a result, it is possible to reduce or prevent surface roughness of the paint substitute film when the composite film is heat-pressed onto the metal plate.

[0014] The present invention prefers the configurations described in [2] to

[15] below. [2] The composite film according to [1], comprising polyethylene terephthalate as the protective film. [3] The composite film according to [1] or [2], wherein the protective film is a biaxially oriented film. [4] The composite film according to any one of [1] to [3], wherein the biaxially oriented polyester film comprises polyethylene terephthalate. [5] A composite film according to any one of [1] to [4], wherein the second sum is greater than the first sum. [6] A composite film according to any one of [1] to [5], wherein the sum of the third is greater than the sum of the fourth. [7] further comprising an adhesive layer, where at least the biaxially oriented polyester film, the adhesive layer, the colored layer, the surface protective layer, and the protective film are stacked in this order, The composite film according to any one of [1] to [6]. [8] The composite film according to [7], wherein the adhesive layer contains at least one functional group selected from the group consisting of an epoxy group, an oxazoline group, a silanol group, and an isocyanate group. [9] The composite film according to [7] or [8], wherein the thickness of the adhesive layer is 10 nm to 200 nm.

[10] The colored layer contains a colorant, where the content of the colorant is 0.5% by mass or more and 40% by mass or less in 100% by mass of the colored layer. The composite film according to any one of [1] to [9].

[11] The composite film according to any one of [1] to

[10] , wherein the surface protective layer contains at least one of a thermosetting resin and a photocurable resin.

[12] a metal plate, and the composite film according to any one of [1] to

[11] laminated on the metal plate, a laminate.

[13] A molded product obtained by press-molding the laminate according to

[12] .

[14] An exterior component of a vehicle including the laminate according to

[12] .

[15] a step of heating the metal plate, and a step of pressure-bonding the composite film according to any one of [1] to

[11] to the heated metal plate, A method for manufacturing a laminate.

[0015] The present invention also preferably has the following configuration.

[16] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, according to any of the above configurations, wherein the difference between the first sum and the second sum is 1.2 MPa or less in absolute value, or 1.0 MPa or less.

[17] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, according to any of the above configurations, wherein the difference between the first sum and the second sum is 0.8 MPa or less in absolute value.

[18] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, according to any of the above configurations, wherein the difference between the first sum and the second sum is 0.1 MPa or more or 0.2 MPa or more in absolute value.

[19] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, according to any of the above configurations, wherein the difference between the first sum and the second sum is 0.3 MPa or more in absolute value.

[20] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, wherein the sum of the second is 0.8 MPa or more or 1.0 MPa or more, according to any of the above configurations. [twenty one] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, according to any of the above configurations, wherein the sum of the second is 1.2 MPa or more. [twenty two] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, wherein the sum of the second is 2.5 MPa or less or 2.3 MPa or less, according to either of the above configurations. [twenty three] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, according to either of the above configurations, wherein the sum of the second is 2.1 MPa or less or 2.0 MPa or less. [twenty four] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the difference between the third sum and the fourth sum is 2.5% or less in absolute value or 2.0% or less. [twenty five] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the difference between the sum of the third and the sum of the fourth is 1.5% or less in absolute value.

[26] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the difference between the sum of the third and the sum of the fourth is 0.2% or more or 0.4% or more in absolute value.

[27] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the difference between the sum of the third and the sum of the fourth is 0.6% or more in absolute value.

[28] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to either of the above configurations, wherein the sum of the third is 5.0% or less or 4.5% or less.

[29] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the sum of the third is 4.0% or less or 3.5% or less.

[30] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the sum of the third is 1.0% or more or 1.3% or more.

[31] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the sum of the third is 1.5% or more.

[32] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, according to any of the above configurations, wherein the thickness of the biaxially oriented polyester film is 10 μm or more or 15 μm or more.

[33] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, wherein the thickness of the biaxially oriented polyester film is 20 μm or more or 30 μm or more, according to any of the above configurations.

[34] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, wherein the thickness of the biaxially oriented polyester film is 200 μm or less or 150 μm or less, according to either of the above configurations.

[35] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, wherein the thickness of the biaxially oriented polyester film is 100 μm or less or 75 μm or less, according to either of the above configurations.

[36] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the polyethylene terephthalate in the biaxially oriented polyester film includes at least one of homopolyethylene terephthalate and copolymerized polyethylene terephthalate.

[37] The composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the copolymerized polyethylene terephthalate of the biaxially oriented polyester film is polyethylene terephthalate copolymerized with at least isophthalic acid.

[38] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the biaxially oriented polyester film comprises a first layer and a second layer.

[39] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the first layer is located closer to the colored layer than the second layer.

[40] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the first layer is located between the second layer and the adhesive layer.

[41] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the melting point of the first layer is higher than the melting point of the second layer.

[42] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, wherein the difference between the melting point of the first layer and the melting point of the second layer is 20°C or more or 25°C or more, according to any of the above configurations.

[43] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, wherein the difference between the melting point of the first layer and the melting point of the second layer is 70°C or less or 60°C or less, according to any of the above configurations.

[44] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, wherein the ratio of the thickness of the first layer to the thickness of the second layer (i.e., thickness of the first layer / thickness of the second layer) is 1.5 or more or 2.0 or more, according to any of the above configurations.

[45] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, according to any of the above configurations, wherein the ratio of the thickness of the first layer to the thickness of the second layer is 10 or less or 8 or less.

[46] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, wherein the second layer comprises copolymerized polyethylene terephthalate, preferably polyethylene terephthalate copolymerized with at least isophthalic acid, according to any of the above configurations.

[47] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the adhesive layer contains a resin.

[48] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, wherein the resin of the adhesive layer has at least one functional group selected from the group consisting of epoxy groups, oxazoline groups, silanol groups, and isocyanate groups, according to any of the above configurations.

[49] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the thickness of the colored layer is 2 μm or more or 5 μm or more.

[50] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to either of the above configurations, wherein the thickness of the colored layer is 100 μm or less or 75 μm or less.

[51] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the colored layer comprises a resin, preferably an acrylic resin.

[52] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, wherein the thickness of the surface protective layer is 5 μm or more or 10 μm or more, according to any of the above configurations.

[53] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, wherein the thickness of the surface protective layer is 80 μm or less or 60 μm or less, according to either of the above configurations.

[54] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the surface protective layer includes the thermosetting resin.

[55] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, wherein the thickness of the protective film is 10 μm or more or 25 μm or more, according to any of the above configurations.

[56] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, according to any of the above configurations, wherein the thickness of the protective film is 38 μm or more.

[57] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, wherein the thickness of the protective film is 150 μm or less or 100 μm or less, according to either of the above configurations.

[58] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate, wherein the thickness of the protective film is 75 μm or less or 50 μm or less, according to either of the above configurations.

[59] A composite film, laminate, molded article, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the protective film is a biaxially oriented film.

[60] A laminate, molded product, vehicle exterior part, or method for manufacturing a laminate according to any of the above configurations, wherein the metal plate includes a steel plate that has been plated with a zinc alloy. [Effects of the Invention]

[0016] The present invention makes it possible to reduce or prevent the occurrence of wrinkles and peeling (specifically, peeling of the composite film from the metal plate) when a composite film is heat-pressed onto a metal plate, and moreover, it is possible to provide a composite film that can reduce or prevent the occurrence of surface roughness of the paint substitute film during that process (i.e., when the composite film is heat-pressed onto a metal plate). The present invention also makes it possible to provide a laminate and a method for manufacturing the same. The present invention also aims to provide a molded product obtained by press-forming a laminate. The present invention also aims to provide a vehicle exterior part. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic cross-sectional view of the composite film in this embodiment. [Figure 2] This is a schematic cross-sectional view of the laminate in this embodiment. [Modes for carrying out the invention]

[0018] Embodiments of the present invention will be described in detail below.

[0019] <1. Composite film> As shown in Figure 1, the composite film 7 includes a paint substitute film 8 and a protective film 9. In the composite film 7, the protective film 9 is provided on top of the paint substitute film 8.

[0020] The difference between the first sum (i.e., the sum of the 230°C shrinkage stress in the TD direction of the coating substitute film 8 and the 230°C shrinkage stress in the MD direction of the coating substitute film 8) and the second sum (i.e., the sum of the 230°C shrinkage stress in the TD direction of the protective film 9 and the 230°C shrinkage stress in the MD direction of the protective film 9) of the composite film 7 is 1.5 MPa or less in absolute value. In other words, the shrinkage stress difference is 1.5 MPa or less in absolute value. Since it is 1.5 MPa or less, it is possible to avoid the shrinkage stress that may be generated in the coating substitute film 8 by thermocompression bonding being excessively large or excessively small compared to the shrinkage stress that may be generated in the protective film 9 by thermocompression bonding. The shrinkage stress difference is an absolute value and may be, for example, 1.2 MPa or less, 1.0 MPa or less, or 0.8 MPa or less. The shrinkage stress difference is an absolute value and may be, for example, 0.1 MPa or more, 0.2 MPa or more, or 0.3 MPa or more.

[0021] The second sum (i.e., the sum of the 230°C shrinkage stress in the TD direction of the protective film 9 and the 230°C shrinkage stress in the MD direction of the protective film 9) may be greater than or less than the first sum (i.e., the sum of the 230°C shrinkage stress in the TD direction of the coating substitute film 8 and the 230°C shrinkage stress in the MD direction of the coating substitute film 8), but it is preferable that it be greater.

[0022] The difference between the third sum (i.e., the sum of the TD-direction 150°C heat shrinkage rate of the coating substitute film 8 and the MD-direction 150°C heat shrinkage rate of the coating substitute film 8) and the fourth sum (i.e., the sum of the TD-direction 150°C heat shrinkage rate of the protective film 9 and the MD-direction 150°C heat shrinkage rate of the protective film 9) of the composite film 7 is 3.0% or less in absolute value. In other words, the difference in heat shrinkage rate is 3.0% or less in absolute value. Since it is 3.0% or less, it is possible to avoid the shrinkage of the coating substitute film 8 during heat bonding being excessively large or excessively small compared to the shrinkage of the protective film 9 during heat bonding. The difference in heat shrinkage rate is an absolute value and may be, for example, 2.5% or less, 2.0% or less, or 1.5% or less. The difference in heat shrinkage rate is an absolute value and may be, for example, 0.2% or more, 0.4% or more, or 0.6% or more.

[0023] The third sum (i.e., the sum of the 150°C heat shrinkage rate in the TD direction of the coating substitute film 8 and the 150°C heat shrinkage rate in the MD direction of the coating substitute film 8) may be greater than or less than the fourth sum (i.e., the sum of the 150°C heat shrinkage rate in the TD direction of the protective film 9 and the 150°C heat shrinkage rate in the MD direction of the protective film 9), but it is preferable that it be greater.

[0024] <1.1. Paint Replacement Film> The paint-alternative film 8 includes a biaxially oriented polyester film 81, an adhesive layer 82, a coloring layer 83, and a surface protection layer (hereinafter sometimes referred to as the "hard coat layer") 84. In the paint-alternative film 8, the biaxially oriented polyester film 81, adhesive layer 82, coloring layer 83, and surface protection layer 84 are stacked in this order.

[0025] The paint substitute film 8 has a first sum (i.e., the sum of the shrinkage stress in the TD direction and the shrinkage stress in the MD direction at 230°C) of 0.3 MPa or more. Since the first sum is 0.3 MPa or more, it is possible to prevent the entire biaxially oriented polyester film 81 from melting at 230°C. Therefore, it is possible to avoid the melting of the entire biaxially oriented polyester film 81 during heat bonding, and to avoid the occurrence of surface roughness of the paint substitute film 8 that would result from the melting of the entire biaxially oriented polyester film 81.

[0026] When the coating substitute film 8 is heated at 150°C for 15 minutes, the sum of the thermal shrinkage rate in the TD direction and the thermal shrinkage rate in the MD direction of the coating substitute film 8 (i.e., the third sum) is preferably 5.0% or less, more preferably 4.5% or less, even more preferably 4.0% or less, and even more preferably 3.5% or less. The smaller the third sum, the less thermal shrinkage of the coating substitute film 8 that may occur due to the heat received by the coating substitute film 8 during lamination (specifically during heat bonding), and therefore the reduction in adhesion strength with the metal plate 5 that may result from such thermal shrinkage can be further suppressed. On the other hand, the third sum may be 1.0% or more, 1.3% or more, or 1.5% or more. The third sum can be controlled, for example, by stretching conditions, heat setting treatment conditions, and the annealing treatment described later. The thermal shrinkage rate of the paint substitute film 8 can be determined by the following formula. Thermal shrinkage rate (%) = {(L0 - L) / L0} × 100 Here, L is the gauge length after heat treatment (specifically, heat treatment at 150°C for 15 minutes), and L0 is the gauge length before heat treatment (specifically, heat treatment at 150°C for 15 minutes). Incidentally, the thermal shrinkage rate of protective film 9 can also be determined using this formula.

[0027] The composite film 7 may be annealed. Annealing can remove or reduce any residual distortion in the composite film 7.

[0028] Annealing can reduce the first sum (i.e., the sum of the 230° shrinkage stress in the TD direction and the 230° shrinkage stress in the MD direction of the coating substitute film 8). Annealing may also reduce the second sum (i.e., the sum of the 230° shrinkage stress in the TD direction and the 230° shrinkage stress in the MD direction of the protective film 9). Therefore, annealing may reduce the absolute value of the shrinkage stress difference.

[0029] Annealing can reduce the third sum (i.e., the sum of the 150°C heat shrinkage rate in the TD direction of the coating substitute film 8 and the 150°C heat shrinkage rate in the MD direction of the coating substitute film 8). Annealing may also reduce the fourth sum (i.e., the sum of the 150°C heat shrinkage rate in the TD direction of the protective film 9 and the 150°C heat shrinkage rate in the MD direction of the protective film 9). Therefore, annealing may reduce the absolute value of the difference in heat shrinkage rates.

[0030] The annealing temperature can be appropriately set depending on, for example, the type of resin (i.e., polyester) contained in the biaxially oriented polyester film 81 and the type of resin (i.e., polyester) contained in the protective film 9. The annealing temperature is preferably near the crystallization temperature of the resin. As an example, 150°C to 170°C is preferred. Below 170°C, excessive acceleration of thermal crystallization can be avoided. On the other hand, above 150°C, the annealing time can be avoided. The annealing time is preferably within 10 minutes, and more preferably within 5 minutes.

[0031] <1.1.1. Biaxially oriented polyester film> The thickness of the biaxially oriented polyester film 81 is preferably 10 μm or more, more preferably 15 μm or more, even more preferably 20 μm or more, and even more preferably 30 μm or more. A thickness of 10 μm or more facilitates film formation and also facilitates the formation of functional layers such as the colored layer 83 and the surface protection layer 84. In addition, the handling properties of these layers when laminating the composite film 7 to the metal plate 5 are also good. On the other hand, the thickness of the biaxially oriented polyester film 81 is preferably 200 μm or less, more preferably 150 μm or less, even more preferably 125 μm or less, even more preferably 100 μm or less, and even more preferably 75 μm or less. A thickness of 200 μm or less prevents the load required for press molding of the laminate 4 from becoming excessively large.

[0032] The biaxially oriented polyester film 81 includes a B layer (i.e., the first layer) 811 and an A layer (i.e., the second layer) 812. The B layer 811 is located closer to the colored layer 83 than the A layer 812. The B layer 811 is located between the A layer 812 and the adhesive layer 82.

[0033] The melting point of layer B 811 (hereinafter sometimes referred to as "TmB") is preferably higher than the melting point of layer A 812 (hereinafter sometimes referred to as "TmA"). In other words, it is preferable that the melting point of layer A 812 is lower than the melting point of layer B 811. This makes it possible to lower the lamination temperature (specifically the thermocompression temperature) compared to the case where the biaxially oriented polyester film 81 consists only of layer B 811.

[0034] The difference between the melting point of layer B 811 and the melting point of layer A 812 is preferably 20°C or higher, more preferably 25°C or higher, even more preferably 28°C or higher, and even more preferably 30°C or higher. A difference of 20°C or higher reduces the deterioration of the surface shape of the biaxially oriented polyester film 81 that may occur due to the heat received by the coating substitute film 8 during lamination (specifically during heat bonding), and also reduces the viscosity of layer A 812 during lamination (specifically during heat bonding). On the other hand, the difference between the melting point of layer B 811 and the melting point of layer A 812 is preferably 70°C or lower, more preferably 60°C or lower, and even more preferably 50°C or lower. A difference of 70°C or lower results in good handling during film formation.

[0035] The ratio of the thickness of layer B 811 to the thickness of layer A 812 (i.e., thickness of layer B 811 / thickness of layer A 812) is preferably 1.5 or more, and more preferably 2.0 or more. A ratio of 1.5 or more reduces the deterioration of the appearance of the coating substitute film 8 that may occur due to the heat received by the coating substitute film 8 during lamination (specifically during heat bonding). In addition, it reduces or prevents the deterioration of the appearance of the coating substitute film 8 that may occur due to the heat received by the coating substitute film 8 when the laminate 4 is press-molded. On the other hand, the ratio of the thickness of layer B 811 to the thickness of layer A 812 (i.e., thickness of layer B 811 / thickness of layer A 812) is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less.

[0036] The thickness of layer B 811 is preferably 20 μm or more, more preferably 25 μm or more, and even more preferably 30 μm or more. A thickness of 20 μm or more reduces the deterioration of the surface shape of the biaxially oriented polyester film 81 that may occur due to the heat received by the coating substitute film 8 during lamination (specifically during heat bonding). In addition, it reduces or prevents the deterioration of the appearance of the coating substitute film 8 that may occur due to the heat received by the coating substitute film 8 when the laminate 4 is press-molded. The thickness of layer B 811 is preferably 150 μm or less, more preferably 100 μm or less, even more preferably 75 μm or less, and even more preferably 50 μm or less.

[0037] The melting point of layer B 811 is preferably 250°C or higher, more preferably 252°C or higher, and even more preferably 253°C or higher. On the other hand, the melting point of layer B 811 may be 260°C or lower, or 258°C or lower.

[0038] Layer B 811 contains a first polyester, i.e., a first polyester resin. The intrinsic viscosity, i.e., the intrinsic viscosity of the first polyester, is preferably 0.60 or higher. A viscosity of 0.60 or higher reduces the generation of thermally degraded products derived from low molecular weight components. On the other hand, the intrinsic viscosity of the first polyester is preferably less than 0.95.

[0039] The first polyester is preferably a crystalline polyester. If the first polyester is a crystalline polyester, it is possible to reduce uneven stretching of the paint substitute film 8 that may occur when the laminate 4 is press-molded. This will be explained. When the laminate 4 is press-molded, the paint substitute film 8 is partially stretched by the press molding. If the B layer 811 of the biaxially oriented polyester film 81 contains crystalline polyester, it is possible for the crystallization of the crystalline polyester to progress more in the part that is stretched the most (i.e., the part with the greatest deformation) than in the surrounding area (i.e., the area around the part with the greatest deformation). Therefore, at the beginning of press molding, the paint substitute film 8 stretches easily in the part with the greatest deformation, but as press molding progresses, the part with the greatest deformation itself becomes less stretchable. As a result, the surrounding area (i.e., the area around the part with the greatest deformation) stretches. Therefore, it is possible to prevent the thickness of the part with the greatest deformation from becoming excessively thin. Hence, uneven stretching of the paint substitute film 8 can be reduced. Crystalline polyester refers to polyester in which an endothermic peak of 0.05 J / g or more appears in the differential scanning calorimetry (DSC) curve at a temperature higher than the baseline shift corresponding to the glass transition point, due to crystal melting. In differential scanning calorimetry to obtain the DSC curve, a sample is scraped from layer B 811, 10 mg of the sample is heated to 290°C at 20°C / min, isothermal for 3 minutes, rapidly cooled at 200°C / min, and heated to 290°C at 10°C / min. A DSC-60 differential scanning calorimeter is used for differential scanning calorimetry.

[0040] Examples of the first polyester include polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. Among these, polyethylene terephthalate and polybutylene terephthalate are preferred, and polyethylene terephthalate is more preferred. Examples of polyethylene terephthalate include homo-polyethylene terephthalate and copolymerized polyethylene terephthalate. Among these, homo-polyethylene terephthalate is preferred. Homo-polyethylene terephthalate may contain diethylene glycol components that may be produced as by-products during its manufacture. On the other hand, examples of copolymerization components for obtaining copolymerized polyethylene terephthalate, particularly dicarboxylic acids, include aromatic carboxylic acids such as isophthalic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid; and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. One or more of these can be used. Copolymerization components for obtaining copolymerized polyethylene terephthalate, particularly diols, include aliphatic diols such as trimethylene glycol (propanediol), butanediol, and hexanediol; and alicyclic diols such as cyclohexanedimethanol. One or more of these can be used. Among these, isophthalic acid and sebacic acid are preferred, with isophthalic acid being more preferred.

[0041] Therefore, the first polyester may have at least one of butylene terephthalate units and ethylene isophthalate units. Preferably, the total amount of butylene terephthalate units and ethylene isophthalate units in the first polyester is 80 mol% or more.

[0042] The content of the first polyester is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 75% by mass or more, when the B layer 811 is considered to be 100% by mass. The content of the first polyester is, for example, 80% by mass or more, 90% by mass or more, or 95% by mass or more, when the B layer 811 is considered to be 100% by mass. On the other hand, the content of the first polyester is, for example, 100% by mass, 99% by mass or less, 98% by mass or less, 95% by mass or less, or 90% by mass or less, when the B layer 811 is considered to be 100% by mass.

[0043] Layer B 811 may contain additives. Examples of additives include coloring pigments, fluorescent whitening agents, inert particles, antioxidants, heat stabilizers, ultraviolet absorbers, and antistatic agents. Examples of coloring pigments include inorganic pigments and organic pigments. Inorganic pigments are preferred among these. Examples of inorganic pigments include alumina, titanium dioxide, calcium carbonate, and barium sulfate. Titanium dioxide is preferred among these when imparting opacity to layer B 811. The content of the coloring pigment may be 2% by mass or more, 4% by mass or more, or 10% by mass or more, when layer B 811 is considered to be 100% by mass. On the other hand, the content of the coloring pigment may be 50% by mass or less, 40% by mass or less, or 35% by mass or less, when layer B 811 is considered to be 100% by mass. Fluorescent whitening agents can improve whiteness.

[0044] Inert particles can improve the handling, specifically the slipperiness, of the biaxially oriented polyester film 81. Examples of inert particles include polymers or copolymers of monomers selected from polystyrene, methyl polyacrylate, ethyl polyacrylate, methyl polymethacrylate, ethyl polymethacrylate, and divinylbenzene, as well as organic materials such as polytetrafluoroethylene, polyacrylonitrile, benzoguanamine, and silicone. Inorganic materials such as silica, kaolin, talc, and graphite can also be used. Among these, inorganic materials are preferred, and silica, i.e., silica particles, are more preferred. The particle size of the inert particles is preferably 0.02 μm or larger, and more preferably 0.1 μm or larger. On the other hand, the particle size of the inert particles is preferably 10 μm or smaller, and more preferably 2 μm or smaller. The content of inert particles is preferably 0.002% to 0.5% by mass, when the B layer 811 is considered as 100% by mass.

[0045] The thickness of layer A 812 is preferably 5 μm or more, more preferably 8 μm or more, and even more preferably 10 μm or more. If it is 5 μm or more, it is possible to fill any irregularities that may exist on the metal plate 5, and therefore the adhesion strength with the metal plate 5 can be improved. The thickness of layer A 812 is preferably 30 μm or less, more preferably 25 μm or less, even more preferably 20 μm or less, and even more preferably 15 μm or less.

[0046] The melting point of layer A 812 is preferably 160°C or higher, more preferably 180°C or higher, and even more preferably 200°C or higher. On the other hand, the melting point of layer A 812 is preferably 250°C or lower, more preferably 240°C or lower, and even more preferably 230°C or lower.

[0047] Layer A 812 contains a second polyester, i.e., a second polyester resin. The intrinsic viscosity of the second polyester is preferably 0.60 or higher. On the other hand, the intrinsic viscosity of the first polyester is preferably less than 0.95. If it is less than 0.95, it is possible to reduce the viscosity of layer A 812 during lamination (specifically during heat bonding), and therefore, the adhesion strength to the metal plate 5 can be improved.

[0048] The second polyester is preferably a crystalline polyester. A crystalline polyester is a polyester that, in the differential scanning calorimetry (DSC) curve, exhibits an endothermic peak of 0.05 J / g or more at a temperature higher than the temperature at which the baseline shift corresponding to the glass transition occurs, due to crystal melting. For differential scanning calorimetry to obtain the DSC curve, a sample is scraped from layer A 812, 10 mg of the sample is heated to 290°C at 20°C / min, isothermal for 3 minutes, rapidly cooled at 200°C / min, and heated to 290°C at 10°C / min. A DSC-60 differential scanning calorimeter is used for differential scanning calorimetry.

[0049] Examples of the second polyester include polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. Among these, polyethylene terephthalate is preferred. Examples of polyethylene terephthalate include homopolymer polyethylene terephthalate and copolymerized polyethylene terephthalate. Among these, copolymerized polyethylene terephthalate is preferred. The explanation of copolymerized polyethylene terephthalate in the second polyester overlaps with the explanation of copolymerized polyethylene terephthalate in the first polyester, so it is omitted. Therefore, the explanation of copolymerized polyethylene terephthalate in the first polyester can also be treated as the explanation of copolymerized polyethylene terephthalate in the second polyester.

[0050] Therefore, the second polyester may have at least one of butylene terephthalate units and ethylene isophthalate units. Preferably, the total amount of butylene terephthalate units and ethylene isophthalate units in the second polyester is 80 mol% or more.

[0051] The content of the second polyester is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, when the A layer 812 is considered to be 100% by mass. On the other hand, the content of the second polyester may be, for example, 100% by mass, 99% by mass or less, 98% by mass or less, or 95% by mass or less, when the A layer 812 is considered to be 100% by mass.

[0052] Layer A 812 may contain additives. Examples of additives include coloring pigments, fluorescent whitening agents, inert particles, antioxidants, heat stabilizers, ultraviolet absorbers, and antistatic agents.

[0053] The biaxially oriented polyester film 81 can be produced by a procedure in which an unstretched polyester film is prepared, and then the unstretched polyester film is biaxially stretched. For example, the biaxially oriented polyester film 81 can be produced by a procedure in which a molding material for forming layer B 811 (i.e., a polyester composition containing a first polyester) is supplied to a first extruder, and a molding material for forming layer A 812 (specifically, a polyester composition containing a second polyester) is supplied to a second extruder, then the molding material is guided from the first extruder to a feed block, and the molding material is guided from the second extruder to a feed block, and these molding materials are laminated in the feed block, then the unstretched polyester film (hereinafter sometimes referred to as "sheet") is melt-extruded from the die, then the unstretched polyester film is solidified in a cooling drum, the unstretched polyester film is biaxially stretched, and then heat-fixed. Alternatively, the film can be manufactured by supplying raw materials for forming layer B 811 to a first extruder and raw materials for forming layer A 812 to a second extruder, then guiding the molding material from the first extruder to a multi-manifold die and guiding the molding material from the second extruder to a multi-manifold die, laminating these molding materials in the multi-manifold die, then melt-extruding the unstretched polyester film from the multi-manifold die, then solidifying the unstretched polyester film in a cooling drum, biaxially stretching the unstretched polyester film, and heat-setting it. The biaxial stretching may be simultaneous biaxial stretching in the longitudinal and transverse directions, or sequential biaxial stretching. Sequential biaxial stretching is preferred. In sequential biaxial stretching, for example, it is preferable to stretch the sheet that has passed through the cooling roll in the flow direction, i.e., the Machine Direction (i.e., MD direction), and then stretch the sheet after stretching in the MD direction in the width direction, i.e., the Transverse Direction (i.e., TD direction). Furthermore, a surface treatment may be applied to the sheet between the first stretching (for example, stretching in the flow direction) and the second stretching (for example, stretching in the width direction). For example, an adhesive layer 82 may be formed between the first stretching and the second stretching.

[0054] Regarding extrusion, in the first extruder, it is preferable to supply the molding material for forming layer B 811, i.e., the polyester composition containing the first polyester, to the first extruder after it has been thoroughly dried, and to melt it at a temperature of ~(melting point + 50)°C of the first polyester. On the other hand, in the second extruder, it is preferable to supply the molding material for forming layer A 812, i.e., the polyester composition containing the second polyester, to the second extruder after it has been thoroughly dried, and to melt it at a temperature of ~(melting point + 50)°C of the second polyester. At least one of the molding material for forming layer B 811 and the molding material for forming layer A 812 may contain inert particles.

[0055] When biaxial stretching is sequential biaxial stretching, the unstretched polyester film can be heated and stretched in the flow direction. Examples of heating methods for the unstretched polyester film include roll heating and infrared heating. The stretching temperature in the flow direction is preferably 70°C or higher, and more preferably 80°C or higher. A temperature of 70°C or higher can reduce the occurrence of breakage. On the other hand, the stretching temperature in the flow direction is preferably 110°C or lower, and more preferably 100°C or lower. A temperature of 110°C or lower can avoid excessively low orientation.

[0056] The stretching ratio in the flow direction is preferably 3.0 times or more, and more preferably 3.5 times or more. A ratio of 3.0 times or more makes it possible to avoid excessively low orientation. In addition, it is possible to reduce or avoid the occurrence of excessive thickness unevenness, and to reduce or avoid the occurrence of excessive looseness that may occur when the biaxially oriented polyester film 81 is wound into a roll. On the other hand, the stretching ratio in the flow direction is preferably 5.0 times or less, more preferably 4.5 times or less, and even more preferably 4.0 times or less. A ratio of 5.0 times or less allows for effective enjoyment of the effect of improving thickness unevenness due to stretching. As an example of a method for stretching in the flow direction, one can cite a method in which a heated unstretched polyester film is stretched by the speed difference between rolls.

[0057] A polyester film stretched in the flow direction can be stretched in the width direction. A stretching temperature of 90°C or higher is preferable, as this reduces the occurrence of breakage. On the other hand, a stretching temperature of 130°C or lower is preferable, as this avoids excessively low orientation.

[0058] The stretching ratio in the width direction is preferably 3.0 times or more, and more preferably 3.5 times or more. A ratio of 3.0 times or more makes it possible to avoid excessively low orientation. In addition, it is possible to reduce or avoid the occurrence of excessive thickness unevenness, and to reduce or avoid the occurrence of excessive looseness that may occur when the biaxially oriented polyester film 81 is wound into a roll. On the other hand, the stretching ratio in the width direction is preferably 5.0 times or less, and more preferably 4.5 times or less. A ratio of 5.0 times or less makes it possible to effectively enjoy the effect of improving thickness unevenness due to stretching.

[0059] It is preferable to perform a heat-setting treatment after biaxial stretching. The higher the heat-setting temperature, the smaller the first sum (i.e., the sum of the 230°C shrinkage stress in the TD direction of the coating substitute film 8 and the 230°C shrinkage stress in the MD direction of the coating substitute film 8) and the third sum (i.e., the sum of the 150°C heat shrinkage rate in the TD direction of the coating substitute film 8 and the 150°C heat shrinkage rate in the MD direction of the coating substitute film 8) tend to be. The heat-setting temperature is preferably 205°C or higher, more preferably 210°C or higher, even more preferably 213°C or higher, and even more preferably 215°C or higher. On the other hand, the heat-setting temperature may be 240°C or lower, 235°C or lower, or 230°C or lower. The heat-setting treatment time may be, for example, 2 seconds or more, or 5 seconds or more. The heat-setting treatment time may be, for example, 20 seconds or less, or 10 seconds or less.

[0060] It is preferable to perform a thermal relaxation treatment in conjunction with or separately from the thermal setting treatment. In the thermal relaxation treatment, it is preferable to relax in at least one of the flow direction (i.e., MD direction) and the width direction (i.e., TD direction). In particular, relaxation in the width direction is preferable. When relaxation occurs in the width direction, the relaxation rate in the width direction is preferably 3% or more, and more preferably 4% or more. On the other hand, the relaxation rate in the width direction is preferably 8% or less, and more preferably 7% or less.

[0061] <1.1.2. Adhesive layer> The adhesive layer 82 is located between the biaxially oriented polyester film 81 and the colored layer 83. Specifically, the adhesive layer 82 is located between the B layer 811 of the biaxially oriented polyester film 81 and the colored layer 83. The adhesive layer 82 can improve the adhesion between the biaxially oriented polyester film 81 and the colored layer 83. Mechanisms for improving adhesion include, for example, bond formation between functional groups, reduction of interlayer interface energy, and interlayer interface mixing. The adhesive layer 82 can also be referred to as the easy-adhesion layer 82.

[0062] From the viewpoint of adhesion, the thickness of the adhesive layer 82 is preferably 10 nm or more, more preferably 15 nm or more, even more preferably 20 nm, and even more preferably 40 nm or more. On the other hand, from the viewpoint of thickness uniformity and adhesion, the thickness of the adhesive layer 82 is preferably 200 nm or less, more preferably 180 nm, even more preferably 150 nm, and even more preferably 120 nm or less.

[0063] The adhesive layer 82 contains a resin. Examples of resins include polyurethane resins, vinyl chloride / vinyl acetate copolymer resins, vinyl chloride / vinyl acetate / acrylic copolymer resins, chlorinated polypropylene resins, acrylic resins, polyester resins, polyamide resins, butyral resins, polystyrene resins, nitrocellulose resins, and cellulose acetate resins. One or more of these can be used. Among these, acrylic resins and polyester resins are preferred. Considering that heat is generated by shear during press molding of the laminate 4, and the laminate 4 may reach a temperature of about 150°C, the glass transition temperature of the resin is preferably 150°C or lower.

[0064] The resin preferably has at least one functional group selected from the group consisting of epoxy groups, oxazoline groups, silanol groups, and isocyanate groups. Among these, epoxy groups and oxazoline groups are preferred as functional groups because they can further improve adhesion with layer B 811.

[0065] The adhesive layer 82 can be formed on the biaxially oriented polyester film 81 by any method. For example, the adhesive layer 82 may be formed by in-line coating, where the coating is applied while the biaxially oriented polyester film 81 is being formed. Alternatively, the adhesive layer 82 may be formed by off-line coating, where the biaxially oriented polyester film 81 is formed, wound into a roll, and then unwound and coated.

[0066] <1.1.3. Colored layer> The colored layer 83 is located between the adhesive layer 82 and the surface protection layer 84. The colored layer 83 is provided on the adhesive layer 82. The colored layer 83 can be used to decorate or protect the metal plate 5.

[0067] The thickness of the colored layer 83 is preferably 2 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. On the other hand, the thickness of the colored layer 83 is preferably 100 μm or less, more preferably 75 μm or less, even more preferably 50 μm or less, even more preferably 40 μm or less, and even more preferably 30 μm or less. The colored layer 83 may be a single layer or a multi-layer structure.

[0068] The colored layer 83 contains a coloring agent. Examples of coloring agents include pigments and dyes. Examples of pigments and dyes include carbon black (ink), iron black, titanium white, antimony white, lead yellow, titanium yellow, reddish-brown, cadmium red, ultramarine, cobalt blue, quinacridone red, isoindolinone yellow, phthalocyanine blue, aluminum, brass, titanium dioxide, and pearlescent pigments. As described above, the colored layer 83 may be a single layer or a multi-layer structure. For example, if the colored layer 83 is a two-layer structure, it may be preferable that one of the two layers contains a luminescent pigment. For example, if the colored layer 83 is a two-layer structure, it may be preferable that the layer closer to the biaxially oriented polyester film 81 contains an aluminum pigment and the layer closer to the surface protection layer 84 contains a pigment.

[0069] The coloring agent content is preferably 0.5% by mass or more, more preferably 2% by mass or more, and even more preferably 5% by mass or more, when the colored layer 83 is considered to be 100% by mass. On the other hand, the coloring agent content is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less, when the colored layer 83 is considered to be 100% by mass.

[0070] It is preferable that the colored layer 83 contains a resin (hereinafter sometimes referred to as "binder resin"). Because the colored layer 83 contains a binder resin, the occurrence of cracks in the colored layer 83 can be reduced when the laminate 4 is press-molded. Examples of binder resins include acrylic resin, urethane resin, polyester resin, and PVDF (polyvinylidene fluoride). One or more of these can be used. Among these, acrylic resin is preferred. It is preferable that the colored layer 83 does not contain polyester containing alkylene terephthalate units.

[0071] The colored layer 83 can be formed on the adhesive layer 82 by any method. Coating is preferred because it allows for easy formation of the colored layer 83.

[0072] <1.1.4.Surface protective layer> The surface protection layer 84 is provided on the colored layer 83. The surface protection layer 84 can reduce scratches on the colored layer 83 and the biaxially oriented polyester film 81 (i.e., it can improve scratch resistance). In addition, the surface protection layer 84 may improve adhesion with the protective film 9. The surface protection layer 84 is preferably transparent. The surface protection layer 84 is preferably weather resistant. The surface protection layer 84 may also be glossy.

[0073] The thickness of the surface protection layer 84 is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more. This is because the thicker the surface protection layer 84, the more it is possible to reduce scratches on the colored layer 83 and the biaxially oriented polyester film 81 (i.e., to improve scratch resistance), and also to improve chemical resistance. On the other hand, the thickness of the surface protection layer 84 is preferably 80 μm or less, more preferably 60 μm or less, and even more preferably 50 μm or less. This is because the thinner the surface protection layer 84, the more economical it is. The surface protection layer 84 may be a single layer or a multi-layer structure.

[0074] It is preferable that the surface protection layer 84 contains at least one of a thermosetting resin and a photocurable resin. In other words, it is preferable that the surface protection layer 84 is thermosetting or photocurable. Thermosetting is preferred. That is, it is preferable that the surface protection layer 84 contains a thermosetting resin. This is because the heat generated by shearing when the laminate 4 is press-molded can promote thermosetting. Examples of thermosetting resins include acrylic resin, melamine resin, and urethane resin. Acrylic resin is preferred among these. One or more of these can be used. It is preferable that the surface protection layer 84 does not contain polyester containing alkylene terephthalate units. It is preferable that the surface protection layer 84 contains a crosslinking agent. The surface protection layer 84 may also contain other additives.

[0075] The degree of curing in the surface protection layer 84 may be, for example, fully cured or incompletely cured. Here, fully cured is the state in which curing has reached its final stage. On the other hand, incompletely cured is the state in which curing has not reached its final stage. Incomplete curing is preferred because, when the laminate 4 is press-molded, the surface protection layer 84 can effectively follow the deformation of the metal plate 5. If the surface protection layer 84 contains a thermosetting resin, the degree of curing in the surface protection layer 84 is preferably incompletely thermosetting. The degree of curing can be, for example, stage B.

[0076] The surface protection layer 84 can be formed on the colored layer 83 by any method. For example, the surface protection layer 84 can be formed by coating, melt extrusion, lamination, etc. Among these, coating is preferred because it allows for easy formation of the surface protection layer 84. When forming a two-layer surface protection layer 84, that is, when coating the surface protection layer 84 with paint twice, the drying conditions for the first and second coats may be changed to adjust the degree of hardening of each layer.

[0077] <1.2. Protective film> A protective film 9 is provided on the surface protective layer 84 of the paint substitute film 8. The protective film 9 prevents the paint substitute film 8 from being scratched and also prevents dirt from adhering to the paint substitute film 8.

[0078] The protective film 9 has a second sum (i.e., the sum of the shrinkage stress in the TD direction and the shrinkage stress in the MD direction at 230°C) of 0.3 MPa or more. Since the second sum is 0.3 MPa or more, it is possible to prevent the protective film 9 from melting at 230°C. Therefore, it is possible to avoid melting of the protective film 9 during thermocompression bonding, and to avoid the occurrence of surface roughness of the coating substitute film 8 due to the melting of the protective film 9. The second sum may be, for example, 0.8 MPa or more, 1.0 MPa or more, or 1.2 MPa or more. On the other hand, the second sum is preferably 2.5 MPa or less, more preferably 2.3 MPa or less, even more preferably 2.1 MPa or less, and still more preferably 2.0 MPa or less.

[0079] The thickness of the protective film 9 is preferably 10 μm or more, more preferably 25 μm or more, and even more preferably 38 μm or more. A thickness of 10 μm or more provides excellent rigidity. The thickness of the protective film 9 is preferably 150 μm or less, more preferably 100 μm or less, even more preferably 75 μm or less, and even more preferably 50 μm or less. This is because the thinner the protective film 9, the more economical it is. The protective film 9 may be a single-layer structure or a multi-layer structure.

[0080] The protective film 9 is preferably a biaxially oriented film. In other words, the protective film 9 is preferably a biaxially stretched film. This is because biaxial stretching improves the heat resistance of the protective film 9. The protective film 9 may be, for example, a biaxially stretched polyester film or a biaxially stretched polyethylene terephthalate film. Here, the polyethylene terephthalate may be homo-polyethylene terephthalate or copolymerized polyethylene terephthalate, as will be described later. Homo-polyethylene terephthalate may contain diethylene glycol components that may be produced as a by-product during its manufacture.

[0081] The protective film 9 preferably contains polyester. Examples of polyester include polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. Polyethylene terephthalate is preferred among these. Examples of polyethylene terephthalate include homo-polyethylene terephthalate and copolymerized polyethylene terephthalate. Homo-polyethylene terephthalate and copolymerized polyethylene terephthalate are preferred among these, with homo-polyethylene terephthalate being more preferred. Homo-polyethylene terephthalate may contain diethylene glycol components that may be produced as by-products during its manufacture. On the other hand, examples of copolymerization components for obtaining copolymerized polyethylene terephthalate, particularly dicarboxylic acids, include aromatic carboxylic acids such as isophthalic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid; and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. One or more of these can be used. Copolymerization components for obtaining copolymerized polyethylene terephthalate, particularly diols, include aliphatic diols such as trimethylene glycol (propanediol), butanediol, and hexanediol; and alicyclic diols such as cyclohexanedimethanol. One or more of these can be used. Among these, isophthalic acid and sebacic acid are preferred, with isophthalic acid being more preferred.

[0082] Of the two surfaces of the protective film 9, the surface roughness of at least the surface in contact with the surface protective layer 84 is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 10 nm or more. A surface roughness of 10 nm or more results in good transportability of the protective film 9, thus providing good handling. Since the surface shape of the protective film 9 can be transferred to the surface protective layer 84, the surface roughness of the protective film 9 (specifically, the surface roughness of at least one of the two surfaces of the protective film 9 that is in contact with the surface protective layer 84) is preferably 1000 nm or less, more preferably 800 nm or less, and even more preferably 500 nm or less.

[0083] Preferably, at least one of the two surfaces of the protective film 9 that is in contact with the surface protective layer 84 is subjected to a delamination treatment. For example, silicone-based delaminating agents, fluorine-based delaminating agents, and long-chain aliphatic delaminating agents can be used for the delamination treatment. Among these, silicone-based delaminating agents are preferred because they are inexpensive.

[0084] The protective film 9 can be formed on the surface protective layer 84 of the paint-alternative film 8 by any method. For example, the protective film 9 can be formed by coating, melt extrusion, lamination, etc. Among these, lamination, i.e., laminating the protective film 9 onto the paint-alternative film 8, is preferred.

[0085] <2. Laminate> As shown in Figure 2, the laminate 4 includes a metal plate 5 and a composite film 7 laminated to the metal plate 5. In the laminate 4, the metal plate 5, the coating substitute film 8, and the protective film 9 are stacked in this order. In the laminate 4, a biaxially oriented polyester film 81 is provided on the metal plate 5. Layer A 812 of the biaxially oriented polyester film 81 is located between the metal plate 5 and layer B 811. Layer A 812 adheres the metal plate 5 and layer B 811.

[0086] <2.1. Metal plate> Examples of metal plates 5 include steel plates, aluminum alloy plates, and magnesium alloy plates. Among these, steel plates are preferred. Examples of steel plates include stainless steel plates. These may be pre-treated with zinc alloy plating or chromium plating. In other words, the steel plates may be surface-treated steel plates. Examples of surface-treated steel plates include tin-free steel plates and tinplate. In particular, when the laminate 4 is used to manufacture vehicle exterior parts, the metal plate 5 is preferably a steel plate with zinc alloy plating. Zinc alloy plating can improve corrosion resistance.

[0087] The thickness of the metal plate 5 may be, for example, 0.2 mm or more, 0.3 mm or more, 0.4 mm or more, or 0.6 mm or more. On the other hand, the thickness of the metal plate 5 may be, for example, 1.4 mm or less, 1.2 mm or less, 1.0 mm or less, or 0.8 mm or less. In particular, for good formability, the thickness of the metal plate 5 is preferably 0.2 mm or more and 1.4 mm or less, more preferably 0.3 mm or more and 1.2 mm or less, and even more preferably 0.3 mm or more and 1.0 mm or less. If the metal plate 5 is a steel plate with zinc alloy plating, the thickness of the metal plate 5 is preferably 0.4 mm or more and 0.8 mm or less. If the metal plate 5 is an aluminum alloy plate, the thickness of the metal plate 5 is preferably 0.6 mm or more and 1.2 mm or less.

[0088] <2.2. Method for Manufacturing Laminates> The method for manufacturing the laminate 4 includes a step of heating the metal plate 5 (hereinafter sometimes referred to as the "heating step") and a step of pressing the heated metal plate 5 and the composite film 7 together (hereinafter sometimes referred to as the "pressing step"). The method for manufacturing the laminate 4 may further include a step of cooling the metal plate 5 to which the composite film 7 has been pressed (hereinafter sometimes referred to as the "cooling step"). If the metal plate 5 is in the form of a roll and the composite film 7 is also in the form of a roll, the laminate 4 can be manufactured using a roll-to-roll method.

[0089] <2.2.1. Process of heating the metal plate> In this step, the metal plate 5 is heated. By heating the metal plate 5, it becomes possible to heat-press the metal plate 5 and the composite film 7 together.

[0090] <2.2.2. Crimping Process> In this process, the heated metal plate 5 and the composite film 7 are pressed together. Specifically, the A layer 812 of the composite film 7 is facing the heated metal plate 5 when the two are pressed together.

[0091] In this process, it is preferable that the temperature of the heated metal plate 5 is above the melting point of layer A 812. If the temperature is above the melting point of layer A 812, it is possible to melt layer A 812, and therefore the metal plate 5 and the composite film 7 can be heat-pressed together. The temperature of the heated metal plate 5 is more preferably above the sum of the melting point of layer A 812 and 20°C, even more preferably above the sum of the melting point of layer A 812 and 30°C, even more preferably above the sum of the melting point of layer A 812 and 35°C, and even more preferably above the sum of the melting point of layer A 812 and 40°C. Therefore, if the melting point of layer A 812 is 217°C, the temperature of the heated metal plate 5 is more preferably 237°C or higher, even more preferably 247°C or higher, even more preferably 252°C or higher, and even more preferably 257°C or higher. When the temperature of the heated metal plate 5 is equal to or greater than the sum of the melting point of layer A 812 and 20°C, it is possible to effectively reduce the viscosity of layer A 812, and therefore improve the adhesion strength to the metal plate 5.

[0092] The temperature of the heated metal plate 5 is preferably less than or equal to the sum of the melting point of layer B 811 and 10°C, more preferably less than or equal to the sum of the melting point of layer B 811 and 8°C, and even more preferably less than or equal to the sum of the melting point of layer B 811 and 7°C. Therefore, if the melting point of layer B 811 is 255°C, the temperature of the heated metal plate 5 is more preferably 265°C or less, more preferably 263°C or less, and even more preferably 262°C or less. If the temperature of the heated metal plate 5 is less than or equal to the sum of the melting point of layer B 811 and 10°C, it is possible to avoid excessive melting of the crystals of layer B 811, and therefore, it is possible to avoid an excessive decrease in the heat resistance of the biaxially oriented polyester film 81. Note that the temperature of the heated metal plate 5 may also be less than or equal to the melting point of layer B 811.

[0093] <2.2.3. Cooling process> In this step, the metal plate 5 to which the composite film 7 is pressed is cooled. Cooling suppresses recrystallization, thus preventing the crystallinity of at least layer A 812 from becoming excessively high after lamination. Therefore, it is possible to prevent the adhesion strength with the metal plate 5 from becoming excessively low. Thus, the occurrence of delamination of the paint substitute film 8 from the metal plate 5, in particular, the occurrence of delamination of the paint substitute film 8 from the metal plate 5 after the laminate 4 has been press-formed, can be further reduced or prevented. As an example of a cooling method, a method of water cooling the metal plate 5 to which the paint substitute film 8 or composite film 7 is pressed can be given. Examples of water cooling methods include immersing the metal plate 5 to which the paint substitute film 8 or composite film 7 is pressed in a water tank, or spraying water onto the metal plate 5 to which the paint substitute film 8 or composite film 7 is pressed. The water in the tank or the water sprayed can be, for example, tap water, well water, rainwater, or pure water. Chemicals may be added to the water. It is preferable that the water in the tank or the water sprayed is cold water. The water temperature may be, for example, 5°C or higher, or 15°C or higher. Preferably, the water temperature is 60°C or lower, more preferably 45°C or lower, even more preferably 35°C or lower, and still more preferably 30°C or lower.

[0094] To effectively suppress recrystallization, it is preferable to start cooling within 5 seconds of pressing the heated metal plate 5 and the composite film 7 together (for example, immersing the metal plate 5 with the coating substitute film 8 or composite film 7 pressed together in a water bath within 5 seconds of pressing), more preferably within 3 seconds, and even more preferably within 2 seconds.

[0095] <3. Molded products> The molded product of this embodiment can be obtained by press molding the laminate 4. Cold press molding is preferred as the press molding method. Cold press molding may be, for example, deep drawing, or stretch molding. If the surface protective layer 84 of the laminate 4 is not yet cured, the surface protective layer 84 may be cured after press molding as needed. After press molding, the protective film 9 may be peeled off from the paint substitute film 8 as needed.

[0096] The molded product can be used, for example, in vehicles, ships (e.g., motorboats), home appliances, and audio products. Vehicles are particularly preferred. Examples of vehicles include automobiles, motorcycles, railway vehicles, and airplanes. Automobiles and motorcycles are particularly preferred. When the molded product is used in a vehicle, it is preferable to use it as a vehicle exterior part. As a vehicle exterior part, an exterior panel is preferred, and an automobile exterior panel is more preferred. The molded product may also be used as a construction member or a steel plate product.

[0097] <4. Various modifications can be made to the embodiments described above.> Various modifications can be made to the embodiments described above. For example, one or more of the following modifications can be selected to modify the embodiments described above.

[0098] In the embodiments described above, a configuration was described in which the composite film 7 has only a coating substitute film 8 and a protective film 9. However, this embodiment is not limited to this configuration. The composite film 7 may further include other films.

[0099] In the above-described embodiment, a configuration was described in which the coating substitute film 8 includes an adhesive layer 82. However, this embodiment is not limited to this configuration. That is, the laminate 4 does not have to include an adhesive layer 82.

[0100] In the above-described embodiment, a configuration was described in which the colored layer 83 is provided on the adhesive layer 82. However, this embodiment is not limited to this configuration. Other layers may be present between the adhesive layer 82 and the colored layer 83.

[0101] In the above-described embodiment, a configuration was described in which the surface protection layer 84 is provided on the colored layer 83. However, this embodiment is not limited to this configuration. Other layers may be present between the colored layer 83 and the surface protection layer 84.

[0102] In the above-described embodiment, a configuration was described in which the protective film 9 is provided on the surface protective layer 84. However, this embodiment is not limited to this configuration. Other layers may be present between the surface protective layer 84 and the protective film 9.

[0103] In the above-described embodiment, a configuration was described in which the biaxially oriented polyester film 81 includes a B layer 811 and an A layer 812. However, this embodiment is not limited to this configuration. For example, the biaxially oriented polyester film 81 may include only one of the B layer 811 and the A layer 812. The biaxially oriented polyester film 81 may include other layers between the B layer 811 and the A layer 812. [Examples]

[0104] The present invention will be described in more detail below with reference to examples and comparative examples. Hereafter, unless otherwise specified, "parts" means "parts by mass" and "%" means "percent mass".

[0105] <Measurement methods for each physical property> <Intrinsic viscosity> 0.2 g of polyester resin was dissolved in 50 ml of a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (60 / 40 (mass ratio)), and the intrinsic viscosity (IV) was measured at 30°C using an Ostwald viscometer. The unit is dl / g.

[0106] <Thickness> Ultrathin cross-sectional sections cut from composite films were observed using a transmission electron microscope (HU-12 model) manufactured by Hitachi, Ltd., and the thicknesses of the protective film, the A layer of the easy-adhesion film, and the B layer of the easy-adhesion film were measured.

[0107] <Thermal shrinkage rate of paint substitute film> Five test specimens measuring 10 mm wide x 150 mm long (hereinafter sometimes referred to as "MD test specimens") were cut from the paint substitute film so that the MD direction of the paint substitute film was aligned with the length direction of the test specimen. A gauge mark was marked in the center of each MD test specimen at intervals of 100 mm ± 2 mm. At this time, the distance between the gauge marks, i.e., the distance between gauge marks, was measured with an accuracy of 0.1 mm. The MD test specimens were suspended without load in a constant temperature chamber of a hot air dryer (PHH-202 manufactured by ESPEC Corporation) and heated at 150°C for 15 minutes. The MD test specimens were removed from the constant temperature chamber, cooled to room temperature (specifically 23°C), and then the distance between the gauge marks was measured. The thermal shrinkage coefficient in the MD direction was calculated using the following formula. Thermal shrinkage rate (%) = {(L0 - L) / L0} × 100 Here, L is the gauge length after heating, and L0 is the gauge length before heating. The average values ​​of five MD test specimens were substituted for L and L0. Meanwhile, five test pieces measuring 10 mm wide x 150 mm long (hereinafter sometimes referred to as "TD test pieces") were cut from the paint substitute film so that the TD direction of the paint substitute film was the length direction of the test piece. A gauge mark was made in the center of each TD test piece at an interval of 100 mm ± 2 mm. At this time, the interval between the gauge marks, i.e., the distance between the gauge marks, was measured with an accuracy of 0.1 mm. The TD test pieces were suspended without load in a constant temperature chamber of a hot air dryer (PHH-202 manufactured by ESPEC), and heated at 150°C for 15 minutes. The TD test pieces were removed from the constant temperature chamber, cooled to room temperature (specifically 23°C), and then the distance between the gauge marks was measured. The thermal shrinkage coefficient in the TD direction was calculated using the following formula. Thermal shrinkage rate (%) = {(L0 - L) / L0} × 100 Here, L is the gauge length after heating, and L0 is the gauge length before heating. The average values ​​of five TD test specimens were substituted for L and L0.

[0108] <Thermal shrinkage rate of protective film> The thermal shrinkage rate of the protective film in the MD direction was determined using the same method as for the coating substitute film, except that the protective film was peeled off and five test pieces measuring 10 mm wide x 150 mm long were cut from the protective film so that the MD direction of the protective film was aligned with the length direction of the test piece. The thermal shrinkage rate of the protective film in the TD direction was determined using the same method as for the coating substitute film, except that the protective film was peeled off from the composite film, and five test pieces measuring 10 mm wide x 150 mm long were cut from the protective film so that the TD direction of the protective film was aligned with the length direction of the test piece.

[0109] <Shrinkage stress of paint-alternative films> Five test specimens, 4 mm wide and 10 mm long, were cut from the paint substitute film so that the median diameter (MD) direction of the film was aligned with the length direction of the test specimen. To perform thermomechanical analysis of the test specimens, a TMA-60 (Shimadzu Corporation) was used, with a sample holder spacing of 5 mm and an initial load of 54 mN, and the temperature was increased from 30°C at a rate of 10°C / min. The shrinkage stress at 230°C in the MD direction was determined from the average load of the five test specimens at 230°C. The shrinkage stress at 230°C in the TD direction was determined using the same method as for the shrinkage stress in the MD direction, except that five test pieces measuring 4 mm wide x 10 mm long were cut from the paint substitute film so that the TD direction of the paint substitute film was aligned with the length direction of the test piece.

[0110] <Shrinkage stress of protective film> The shrinkage stress of the protective film at 230°C in the MD direction was determined using the same method as for the paint substitute film, except that the protective film was peeled off and five test pieces measuring 4 mm wide x 10 mm long were cut from the protective film so that the MD direction of the protective film was aligned with the length direction of the test piece. The shrinkage stress of the protective film at 230°C in the TD direction was determined using the same method as for the paint substitute film, except that the protective film was peeled off and five test pieces measuring 4 mm wide x 10 mm long were cut from the protective film so that the TD direction of the protective film was aligned with the length direction of the test piece.

[0111] <Lamination Evaluation> The composite film and the steel plate were heat-pressed at 260°C with the A layer of the paint-alternative film facing a 0.6 mm thick steel plate coated with zinc alloy. The appearance of the resulting laminate was visually evaluated according to the following criteria. Rating A: No wrinkles or peeling, and no surface imperfections. Rating B: No wrinkles or peeling, but the surface is rough. Criteria C: At least one of the following is present: wrinkles and / or peeling. Here, "peeling" refers to the peeling of the composite film from the steel plate.

[0112] <Polyester resin> <Polyester resin used to form the B layer of the paint-alternative film> (Resin composition A) A mixture of resins B and C was used as resin composition A. Resin B: PET resin, IV = 0.75 dl / g, melting point 255°C, 97.0 parts by mass Resin C: PET resin containing 0.036% by mass of silica particles (average particle size 1.7 μm) in 100% by mass of Resin C, IV = 0.75 dl / g, melting point 255°C, 3.0 parts by mass

[0113] (Resin composition D) A mixture of the following resins E and F was used as resin composition D. Resin E: PET resin, IV = 0.62 dl / g, melting point 255°C, 90.0 parts by mass Resin F: PET resin containing 0.72% by mass of silica particles (average particle size 2.7 μm) in 100% by mass of resin F, IV = 0.62 dl / g, melting point 255°C, 10.0 parts by mass

[0114] <Polyester resin used to form layer A of the paint-alternative film> (Resin D) Copolymer polyester resin containing 86.0 mol% ethylene terephthalate units and 14.0 mol% ethylene isophthalate units, IV = 0.70 dl / g, melting point 217°C

[0115] (Resin K) Copolymer polyester resin containing 89.2 mol% ethylene terephthalate units and 10.8 mol% ethylene isophthalate units, IV = 0.63 dl / g, melting point 225°C

[0116] <Preparation of hard coat paints> 150 parts by mass of methyl isobutyl ketone were placed in a four-necked flask equipped with a condenser, stirrer, thermometer, and nitrogen inlet tube, and the mixture was heated while stirring under a nitrogen atmosphere. When the temperature in the flask reached 74°C, this temperature was maintained as the synthesis temperature, and a monomer solution consisting of 3 parts by mass of methyl methacrylate, 82.54 parts by mass of n-butyl methacrylate, 12.85 parts by mass of 4-hydroxybutyl acrylate, 0.61 parts by mass of methacrylic acid, 1 part by mass of Funcryl FA-711MM (manufactured by Hitachi Chemical Co., Ltd., pentamethylpiperidinyl methacrylate), and 0.1 parts by mass of azobisisobutyronitrile was added dropwise to the flask over 2 hours. Starting 1 hour after the end of monomer addition, 0.02 parts by mass of azobisisobutyronitrile were added every hour to continue the reaction until the amount of unreacted monomer in the monomer solution was 1% or less. When the amount of unreacted monomer was reduced to 1% or less, the reaction was terminated by cooling, yielding an acrylic copolymer solution with a solid content of approximately 40% by mass. To this acrylic copolymer solution, 59.9 parts by mass (solid mass) of Duranate "P301-75E" (manufactured by Asahi Kasei Chemicals, a polyisocyanate variant of hexamethylene diisocyanate) was added as a polyisocyanate compound, and then methyl isobutyl ketone was added to bring the solid content to 30% by mass, and the mixture was stirred to obtain a hard coat coating.

[0117] <Making protective film> (Protective film P1~P3) Except for changing the film formation conditions, protective films P1 to P3 were prepared in the same manner as the method for producing a release film described in Example 1 of Japanese Patent Publication No. 8-294988. Each protective film P1 to P3 comprises a biaxially oriented polyethylene terephthalate film and a silicone release layer formed on the biaxially oriented polyethylene terephthalate film. Here, the biaxially oriented polyethylene terephthalate film contains homopolyethylene terephthalate.

[0118] (Protective film P4) Protective film P4 was prepared using the same method as protective film P1, except that copolymer polyethylene terephthalate containing 11.0 mol% ethylene isophthalate units was used instead of homopolymer polyethylene terephthalate, and the film formation conditions were changed.

[0119] <Example 1> Resin composition A was supplied to a first extruder, and resin D was supplied to a second extruder. Resin composition A was melted at 280°C in the first extruder, and resin D was melted at 270°C in the second extruder. These were then laminated in a die, and the unstretched film was extruded from the die into a cooling drum. The unstretched film was stretched 3.0 times in the MD direction at 80°C, and then an epoxy-based adhesive was coated onto the surface of the film after stretching in the MD direction using a reverse roll coater. Next, it was stretched 3.5 times in the TD direction at 130°C, heat-set at 215°C, heated air was blown onto it while relaxing it by 5% in the TD direction, and it was wound into a roll. This resulted in a 50 μm thick easy-adhesion treated film in which a 10 nm thick easy-adhesion layer, a 40 μm thick B layer containing resin composition A, and a 10 μm thick A layer containing resin D were arranged in this order. While unwinding the easy-adhesion treated film, a paint for forming a colored layer was applied to the easy-adhesion layer of the film using a comma coater. The paint used for forming the colored layer was a solvent-based paint containing an acrylic urethane resin and 10% by mass of aluminum pigment, with 35% by mass of non-volatile components. The coating was performed so that the thickness of the colored layer was 20 μm, and the film was dried in a drying oven at 90°C and then wound up. As the resulting raw material (i.e., the raw material with the colored layer) was unwound, a hard coat coating was applied to the colored layer using a comma coater so that the hard coat layer thickness was 30 μm, and then it was thoroughly dried in a drying oven at 90°C. This yielded a paint substitute film including an easy-adhesion treated film, a colored layer, and a hard coat layer. A protective film (specifically protective film P1) was laminated onto the hard coat layer of the paint-alternative film, and then an annealing treatment was performed at 170°C for 10 minutes to obtain a composite film. Furthermore, the hard coat layer of the composite film that had undergone annealing was in a semi-cured state, meaning it was not yet fully cured.

[0120] <Example 2> A composite film was prepared using the same method as in Example 1, except that resin composition D was used as the resin for layer B, resin K was used as the resin for layer A, the stretching conditions were changed, heat setting was performed at 235°C, protective film P2 was used instead of protective film P1, and annealing treatment was not performed.

[0121] <Example 3> A composite film was prepared using the same method as in Example 1, except that resin composition D was used as the resin for layer B, resin K was used as the resin for layer A, and the stretching conditions were changed.

[0122] <Example 4> A composite film was prepared using the same method as in Example 1, except that resin composition D was used as the resin for layer B, resin K was used as the resin for layer A, the stretching conditions were changed, and the film was heat-set at 235°C.

[0123] <Example 5> A composite film was prepared using the same method as in Example 1, except that resin composition D was used as the resin for layer B, resin K was used as the resin for layer A, the stretching conditions were changed, protective film P2 was used instead of protective film P1, and annealing treatment was not performed.

[0124] <Comparative Example 1> The composite film was prepared using the same method as in Example 1, except that protective film P2 was used instead of protective film P1, and annealing treatment was not performed.

[0125] <Comparative Example 2> A composite film was prepared using the same method as in Example 1, except that resin composition D was used as the resin for layer B, resin K was used as the resin for layer A, the stretching conditions were changed, and annealing treatment was not performed.

[0126] <Comparative Example 3> A composite film was prepared using the same method as in Example 1, except that resin composition D was used as the resin for layer B, resin K was used as the resin for layer A, the stretching conditions were changed, protective film P3 was used instead of protective film P1, and annealing treatment was not performed.

[0127] <Comparative Example 4> The composite film was prepared using the same method as in Example 1, except that protective film P3 was used instead of protective film P1, and annealing treatment was not performed.

[0128] <Comparative Example 5> A composite film was prepared using the same method as in Example 1, except that resin composition D was used as the resin for layer B, resin K was used as the resin for layer A, the stretching conditions were changed, heat setting was performed at 235°C, and annealing treatment was not performed.

[0129] <Comparative Example 6> A composite film was prepared using the same method as in Example 1, except that protective film P4 was used instead of protective film P1, resin composition D was used as the resin for layer B, resin K was used as the resin for layer A, the stretching conditions were changed, and annealing treatment was not performed.

[0130] [Table 1A] [Table 1B] Tables 1A and 1B are explained below. In Table 1, "PET" refers to homo-PET. The sum of PFS is the sum of the thermal shrinkage rate in the TD direction and the thermal shrinkage rate in the MD direction of the protective film. The sum of the PFSS is the sum of the shrinkage stress in the TD direction and the shrinkage stress in the MD direction of the protective film. S is the sum of the thermal shrinkage rate in the TD direction and the thermal shrinkage rate in the MD direction of the paint-alternative film. The sum of SS is the sum of the shrinkage stress in the TD direction and the shrinkage stress in the MD direction of the paint-alternating film. [Table 2]

[0131] In Comparative Example 1, where the sum S-sum PFS was 3.4% in absolute value, wrinkles and peeling occurred. In Comparative Example 1, it is thought that the shrinkage of the paint substitute film during heat bonding was excessively greater than the shrinkage of the protective film during heat bonding. It is thought that this (i.e., the shrinkage of the paint substitute film during heat bonding was excessively greater than the shrinkage of the protective film during heat bonding) caused the wrinkles and peeling.

[0132] In Comparative Example 3, where the sum of SS and PFSS was 1.7 MPa in absolute terms, wrinkles and delamination also occurred. In Comparative Example 3, it is thought that the shrinkage stress generated in the protective film by heat bonding was excessively large compared to the shrinkage stress generated in the paint substitute film by heat bonding. It is thought that this (i.e., the shrinkage stress generated in the protective film being excessively large compared to the shrinkage stress generated in the paint substitute film) caused the wrinkles and delamination. In Comparative Examples 2, 4, and 5, where the sum of SS and PFSS was greater than 1.7 MPa in absolute terms, wrinkles and delamination also occurred.

[0133] In Comparative Example 6, where the sum of PFSS was 0.0 MPa, surface roughness occurred. In Comparative Example 6, since the sum of PFSS of the protective film having a biaxially oriented polyethylene terephthalate film was 0.0 MPa, it is clear that the protective film melted at 230°C. Considering this, it is thought that in Comparative Example 6, the protective film melted during heat bonding. It is thought that this (i.e., the melting of the protective film during heat bonding) caused the surface of the coating substitute film to become rough.

[0134] On the other hand, in Examples 1-5, no wrinkles or peeling occurred in the composite film after heat bonding. In Examples 1-5, there was no surface roughness in the composite film after heat bonding.

[0135] Furthermore, the annealing treatment reduced the absolute values ​​of both the sum S - sum PFS and the sum SS - sum PFSS (see Example 3 and Comparative Example 2; see Example 4 and Comparative Example 5). [Industrial applicability]

[0136] Since this invention relates to composite films, laminates, molded articles, and vehicle exterior parts, it has industrial applicability. [Explanation of Symbols]

[0137] 7...Composite film, 8...Paint substitute film, 9...Protective film, 81...Biaxially oriented polyester film, 82...Adhesive layer, 83...Coloring layer, 84...Surface protective layer, 811...B layer, 812...A layer, 4...Laminate, 5...Metal plate

Claims

1. Paint substitute film, A composite film including a protective film, The aforementioned paint substitute film includes a biaxially oriented polyester film, a coloring layer, and a surface protective layer. At least the biaxially oriented polyester film, the colored layer, the surface protective layer, and the protective film are stacked in this order. The aforementioned coating substitute film has a first sum of the shrinkage stress in the TD direction and the shrinkage stress in the MD direction at 230°C of 0.3 MPa or more. The protective film has a second sum of the shrinkage stress in the TD direction and the shrinkage stress in the MD direction at 230°C of 0.3 MPa or more. The difference between the first sum and the second sum is 1.5 MPa or less in absolute value. The difference between the third sum and the fourth sum is 3.0% or less in absolute value. The third sum is the sum of the thermal shrinkage rate of the coating substitute film in the TD direction and the thermal shrinkage rate of the coating substitute film in the MD direction when the coating substitute film is heated at 150°C for 15 minutes. The fourth sum is the sum of the thermal shrinkage rate of the protective film in the TD direction and the thermal shrinkage rate of the protective film in the MD direction when the protective film is heated at 150°C for 15 minutes. Composite film.

2. The composite film according to claim 1, wherein the protective film comprises polyethylene terephthalate.

3. The composite film according to claim 1, wherein the biaxially oriented polyester film contains polyethylene terephthalate.

4. Further including an adhesive layer, At least the biaxially oriented polyester film, the adhesive layer, the coloring layer, the surface protective layer, and the protective film are stacked in this order. The composite film according to claim 1.

5. The composite film according to claim 4, wherein the adhesive layer comprises at least one functional group selected from the group consisting of epoxy groups, oxazoline groups, silanol groups, and isocyanate groups.

6. The composite film according to claim 4, wherein the thickness of the adhesive layer is 10 nm to 200 nm.

7. The aforementioned colored layer contains a coloring agent, The content of the coloring agent is 0.5% by mass or more and 40% by mass or less in 100% by mass of the colored layer. The composite film according to claim 1.

8. The composite film according to claim 1, wherein the surface protective layer comprises at least one of a thermosetting resin and a photocurable resin.

9. A metal plate and The composite film according to any one of claims 1 to 8 is laminated on the metal plate, Laminated structure.

10. A molded article obtained by press-molding the laminate described in claim 9.

11. A vehicle exterior component comprising the laminate described in claim 9.

12. The process of heating the metal plate, The process includes pressing the composite film according to any one of claims 1 to 8 onto the heated metal plate, A method for manufacturing laminates.

Images