Laminated metal sheet, method for manufacturing a laminated metal sheet, and laminated metal container

Abstract

Provided is a laminate metal plate which is exceptional in both primary adhesion and adhesion after retort sterilization treatment, and does not undergo deterioration of appearance due to whitening even after retort sterilization treatment. A laminate metal plate 10 according to the present invention is configured such that a first film 31 is laminated on at least one surface of a metal plate 20. The first film 31 is a polyester film in which a polyester component is composed of a prescribed first polyester and second polyester. The mass ratio of the first polyester and the second polyester is 20:80 to 50:50, where 100 represents the entire amount of polyester in the first film 31. Two characteristic widths w1 and w2 calculated from an image obtained by binarizing a phase image, which is obtained by observing a cross-sectional part of the first film 31 using a dynamic force mode of a scanning probe microscope, satisfy a prescribed relationship.

Description

[Technical Field]

[0001] This invention relates to laminated metal sheets, a method for manufacturing laminated metal sheets, and laminated metal containers. [Background technology]

[0002] Metal containers such as food cans, beverage cans, and 18L cans are made from tin-free steel (TFS) or aluminum sheets. These metal sheets are painted and baked to provide corrosion resistance, durability, and weather resistance. Baking metal sheets is a complex process that requires a considerable amount of processing time. In addition, a large amount of solvent is discharged when painting metal sheets. Therefore, as an alternative to painted metal sheets, laminated metal sheets, in which a thermoplastic resin film is laminated onto the metal sheet, are used.

[0003] Thermoplastic resin films used for laminated metal sheets include polypropylene (PP), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT). These thermoplastic resin films are required to have good adhesion between the thermoplastic resin film and the metal sheet when molded into a laminated metal sheet, corrosion resistance, and moldability when the laminated metal sheet is formed into a container.

[0004] Metal containers are broadly classified into two-piece cans and three-piece cans. A two-piece can consists of two components: a cylindrical can body with a bottom, and a lid that closes the opening at one end of the can body in the axial direction. A three-piece can consists of three components: a cylindrical can body, a top lid that closes the opening at one end of the can body, and a bottom lid that closes the opening at the other end of the can body.

[0005] The can body of a three-piece can is often formed by cylindrical molding and welding. Furthermore, because the thermoplastic resin film covering the laminated metal sheet in a three-piece can is generally an insulator, welding is technically challenging. For this reason, the laminated metal sheet is often used for the bottom or top lid in three-piece cans.

[0006] Laminated metal sheets are often used for the can body in the case of two-piece cans. There are various molding methods for the can body of a two-piece can, including Draw and Redraw (DRD) molding, Draw and Ironing (DI) molding, and Draw and Thin Redraw (DTR) molding. All of these molding methods involve deep drawing and, if necessary, ironing. For this reason, laminated metal sheets require high workability. In particular, for laminated metal sheets used for the can body of a two-piece can, polyester films, mainly PET, are often used as the thermoplastic resin film.

[0007] Incidentally, canned food products are often subjected to retort sterilization, which involves heating with high-temperature steam for sterilization. In thermoplastic resin films, retort sterilization can sometimes cause tiny bubbles to form inside the film. Because these bubbles have the property of scattering light, thermoplastic resin films that have developed bubbles due to retort sterilization appear cloudy and whitish, which can impair the appearance of canned food products.

[0008] Attempts have been made to suppress the whitening of such thermoplastic resin films. For example, Patent Documents 1 and 2 disclose a polyester film and a laminated metal plate containing PET-based polyester and PBT-based polyester in specific ratios and having a specific orientation state. Patent Document 3 discloses a laminated metal plate containing a resin layer that includes crystals made of PBT resin but does not have stretch orientation. Furthermore, Patent Document 4 discloses a laminated metal plate in which a polyester film containing PET-based polyester and PBT-based polyester in specific ratios is laminated on the outer surface of the can, and a PET-based film is laminated on the inner surface of the can, and the residual orientation degree of each film is kept below a specific value. [Prior art documents] [Patent Documents]

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0010] As described above, for a laminated metal plate, it is required to suppress the adhesion (primary adhesion) between the thermoplastic resin film and the metal plate, the adhesion between the thermoplastic resin film and the metal plate after retort sterilization treatment, and the whitening of the thermoplastic resin film after retort sterilization treatment. However, as a result of the study by the present inventors, it has been found that there is room for improvement in the laminated metal plates of the above documents from the viewpoint of suppressing whitening after retort sterilization treatment.

[0011] In view of the above problems, an object of the present invention is to provide a laminated metal plate that is excellent in primary adhesion and adhesion after retort sterilization treatment, and does not cause deterioration of appearance due to whitening even after retort sterilization treatment. Another object of the present invention is to provide a method for manufacturing the laminated metal plate and a laminated metal container using the laminated metal plate.

Means for Solving the Problems

[0012] As a result of intensive studies to solve the above problems, the present inventors have obtained the following findings. When the film laminated on the metal plate contains PET and PBT in a specific mass ratio, it is possible to ensure primary adhesion and adhesion after retort sterilization treatment. Further, in the case where the microscopic dispersion state of PET and PBT in the film is in a specific state, it is possible to suppress deterioration of appearance due to whitening even after retort sterilization treatment.

[0013] This invention was completed based on the aforementioned findings and further investigations, and the gist of this invention is as follows.

[0014] [1] A laminated metal plate in which a first film is laminated on at least one surface of a metal plate, The first film is a polyester film whose polyester component consists of a first polyester and a second polyester. The first polyester consists of one or both of homopolyethylene terephthalate and copolymerized polyethylene terephthalate. The second polyester consists of one or both of homopolybutylene terephthalate and copolymerized polybutylene terephthalate. With the total amount of polyester in the first film set to 100, the mass ratio of the first polyester to the second polyester is 20:80 to 50:50. A laminated metal plate wherein two characteristic widths w1 and w2, calculated from a binarized image of a phase image obtained by observing the cross-section of the first film using the dynamic force mode of a scanning probe microscope, satisfy the following equations (1) and (2). 10.0nm≦w1≦25.0nm (1) 10.0nm≦w2≦25.0nm (2) However, the threshold value in the binarization is determined by applying the percentile method to the phase lag such that, when areas with small phase lag are shown as dark, the area % of the dark area is equal to the mass % of the first polyester relative to the total amount of polyester in the first film. The characteristic width w1 is the value obtained by dividing the area A1 of the dark region after binarization by the length l1 of the thin line obtained by applying a thinning process to the dark region. The characteristic width w2 is the value obtained by dividing the area A2 of the bright area after binarization by the length l2 of the thin line obtained by applying a thinning process to the bright area.

[0015] [2] The laminated metal plate according to [1], wherein the wide-angle X-ray diffraction spectrum for at least one surface of the metal plate on which the first film is laminated satisfies the following formula (3). I(1) 100 / I(1) amorphous ≤1.5 ···(3) Here, the wide-angle X-ray diffraction spectrum is measured using the θ-2θ method with CuKα rays at a sample angle where the plane formed by the incident X-rays and reflected X-rays is perpendicular to the plane of the first film. I(1) 100 This is the net intensity of the 100 diffraction peak of polyethylene terephthalate appearing at 2θ = 26.5 ± 1.0°. I(1) amorphous This represents the net strength of the amorphous halo that appears at 2θ = 20.0 ± 5.0°.

[0016] [3] The second film is laminated on the other side of the metal plate, The second film comprises a polyester component consisting of one or both of homopolyethylene terephthalate and copolymerized polyethylene terephthalate. In differential scanning thermal analysis of the second film, the highest endothermic peak temperature in the temperature range of 280°C or less was 220°C or higher. The laminated metal plate according to [1] or [2] above, wherein the wide-angle X-ray diffraction spectrum for the other surface of the metal plate on which the second film is laminated satisfies the following formula (4). I(2) 100 / I(2) amorphous ≤1.5 ···(4) Here, the wide-angle X-ray diffraction spectrum is measured using the θ-2θ method with CuKα rays at a sample angle where the plane formed by the incident X-rays and reflected X-rays is perpendicular to the plane of the second film. I(2) 100 This is the net intensity of the 100 diffraction peak of polyethylene terephthalate appearing at 2θ = 26.5 ± 1.0°. I(2) amorphous This represents the net strength of the amorphous halo that appears at 2θ = 20.0 ± 5.0°.

[0017] [4] A step of preheating the metal plate to a preheating temperature of 300°C or less, Subsequently, a heat-pressing process is performed in which film A is heat-pressed onto at least one surface of the metal plate using a laminating roll to form a heat-pressed body. A cooling step in which the heat-sealed body is liquid-cooled to form a laminated metal plate, It has, The aforementioned film A is a polyester film whose polyester component consists of a first polyester and a second polyester. The first polyester consists of one or both of homopolyethylene terephthalate and copolymerized polyethylene terephthalate. The second polyester consists of one or both of homopolybutylene terephthalate and copolymerized polybutylene terephthalate. With the total amount of polyester in film A set to 100, the mass ratio of the first polyester to the second polyester is 20:80 to 50:50. A method for manufacturing a laminated metal sheet, wherein the surface temperature of the film A on the thermocompressed body immediately before being cooled in the cooling step is 205°C or lower.

[0018] [5] The method for manufacturing a laminated metal plate according to [4], wherein the preheating temperature is between -10°C and +50°C relative to the highest endothermic peak temperature in the temperature range of 280°C or less in differential scanning thermal analysis of the film A.

[0019] [6] In the heat-pressing process, the film B is heat-pressed onto the other side of the metal plate. The aforementioned film B consists of one or both of homopolyethylene terephthalate and copolymerized polyethylene terephthalate as its polyester component. In differential scanning thermal analysis of the aforementioned film B, the highest endothermic peak temperature in the temperature range of 280°C or less was 220°C or higher. The method for manufacturing a laminated metal plate according to [4] or [5] above, wherein the preheating temperature of the metal plate is -5°C or more and +60°C or less relative to the endothermic peak temperature of the film B.

[0020] A method for manufacturing a laminated metal plate according to any one of the above [4] to [6], wherein two characteristic widths w'1 and w'2, calculated from a binarized image of a phase image obtained by observing the cross-section of the film A using the dynamic force mode of a scanning probe microscope prior to the thermocompression bonding step, satisfy the following equations (5) and (6). 8.0nm≦w'1≦17.0nm (5) 8.0nm≦w'2≦17.0nm (6) However, the threshold value in the binarization is determined by applying the percentile method to the phase lag such that, when areas with small phase lag are shown as dark, the area percentage of the dark area is equal to the mass percentage of the first polyester relative to the total amount of polyester in the film A. The characteristic width w'1 is the value obtained by dividing the area A'1 of the dark region after binarization by the length l'1 of the thin line obtained by applying a thinning process to the dark region. The characteristic width w'2 is the value obtained by dividing the area A'2 of the bright area after binarization by the length l'2 of the thin line obtained by applying a thinning process to the bright area.

[0021] [8] A laminated metal container including a laminated metal plate as described in any one of [1] to [3] above. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a laminated metal sheet, a method for manufacturing the same, and a laminated metal container using the laminated metal sheet, which have excellent primary adhesion and adhesion after retort sterilization, and which do not deteriorate in appearance due to whitening even after retort sterilization. [Brief explanation of the drawing]

[0023] [Figure 1] These are schematic diagrams and enlarged cross-sectional views of a laminated metal container according to one embodiment of the present invention. [Figure 2] This is a phase image obtained for the cross-sectional view of the first film in Invention Example 1. [Figure 3]This is the binarized image of the phase image in Figure 2. [Figure 4] This is a phase image obtained for the cross-sectional view of the first film in Comparative Example 1. [Modes for carrying out the invention]

[0024] The following describes a laminated metal plate according to one embodiment of the present invention. Note that the embodiments described below are examples that embody the present invention, and these specific examples do not limit the configuration of the present invention.

[0025] (Laminated metal plate) The left side of Figure 1 shows the structure of the laminated metal container 100, and the right side of Figure 1 shows an enlarged cross-section of the wall portion of the laminated metal container 100. As shown in the enlarged cross-sectional view of Figure 1, the laminated metal container 100 includes a laminated metal plate 10 as a material. The laminated metal plate 10 has a front surface 21 which is the outer surface of the laminated metal container 100, and a back surface 22 which is the inner surface of the laminated metal container 100. The laminated metal plate 10 includes a first film 31 which is bonded to at least one of the front surface 21 and back surface 22 of the metal plate 20. Alternatively, the laminated metal plate 10 may have the first film 31 on one of the front surface 21 and back surface 22 of the metal plate 20, and a second film 32 on the other surface. In Figure 1, the metal plate 20 has the first film 31 on the front surface 21 and the second film 32 on the back surface 22.

[0026] [Metal plate] The metal sheet is not particularly limited, but can be an aluminum sheet, a steel sheet, or a sheet of these materials that has undergone various surface treatments, which are widely used as materials for metal containers. In particular, it is preferable to use a surface-treated steel sheet (TFS: Tin Free Steel) on which a film of metallic chromium and chromium hydrate oxide has been formed.

[0027] The steel sheet corresponding to the subway of TFS is not particularly limited as long as it can be formed into a shape corresponding to a laminated metal container, but it is preferably obtained by recrystallization annealing of low-carbon steel or IF (Interstitial Free) steel and then performing rolling such as temper rolling. The steel sheet corresponding to the subway of TFS may be subjected to overaging treatment as necessary. Further, the steel sheet corresponding to the subway of TFS may be subjected to secondary cold rolling.

[0028] As the low-carbon steel, for example, those with a carbon content of 0.010 mass% or more and 0.10 mass% or less can be used. As the IF steel, for example, those obtained by adding Nb, Ti, etc. to extra-low-carbon steel with a carbon content of 0.003 mass% or less can be used. Examples of recrystallization annealing include continuous annealing, tight annealing, open annealing, etc.

[0029] The mechanical properties of the steel sheet corresponding to the subway of TFS are not particularly limited as long as it can be formed into a shape corresponding to a laminated metal container. The yield point of the steel sheet is preferably 220 MPa or more and 580 MPa or less. The r-value of the steel sheet is preferably 0.8 or more. Also, the absolute value of the in-plane anisotropy of the r-value of the steel sheet is preferably 0.7 or less, and more preferably 0.0. The adhesion amounts of the metal chromium layer and chromium hydrated oxide layer of TFS are not particularly limited, but in terms of Cr conversion, the metal chromium layer is 50 - 200 mg / m 2 and the chromium hydrated oxide layer is 3 - 30 mg / m 2 within the range is preferred. When the adhesion amounts of the metal chromium layer and chromium hydrated oxide layer are within the above range, the film and TFS are likely to adhere well, and the corrosion resistance is improved.

[0030] The thickness of the metal plate is not particularly limited, but if the thickness of the metal plate is 0.10 mm or more, the rigidity when formed into a laminated metal container is improved. Therefore, the thickness of the metal plate is preferably 0.10 mm or more. On the other hand, if the thickness of the metal plate is 0.35 mm or less, the energy consumption when forming into a laminated metal container can be reduced. Therefore, the thickness of the metal plate is preferably 0.35 mm or less.

[0031] [First film] The first film is a polyester film whose polyester component consists of a first polyester and a second polyester.

[0032] The first polyester consists of either homopolyethylene terephthalate or copolymerized polyethylene terephthalate, or both. If the first polyester contains copolymerized polyethylene terephthalate, the content of the copolymerized component is preferably 1 mol% or more, and more preferably 3 mol% or more. On the other hand, the content of the copolymerized component is preferably 15 mol% or less, more preferably 14 mol% or less, and even more preferably 8 mol% or less.

[0033] The copolymer components of the first polyester include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenyl etherdicarboxylic acid, diphenyl sulfondicarboxylic acid, diphenoxyethanedicarboxylic acid, and 5-sodium sulfisophthalic acid, as well as aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, suberic acid, sebacic acid, dimer acid, maleic acid, fumaric acid, dodecanedionic acid, and cyclohexanedicarboxylic acid, and their ester derivatives, as acid components.

[0034] Examples of copolymer components of the first polyester include propanediol, butanediol, pentanediol, hexanediol, neopentyl glycol, cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis(4-hydroxyethoxyphenyl)propane, isosorbide (1,4:3,6-dianhydroglucitol, 1,4:3,6-dianhydro-D-sorbitol), spiroglycol, bisphenol A, bisphenol S, etc., as alcohol components.

[0035] The copolymer component of the first polyester may be one or more of the aforementioned types. It is preferable to use isophthalic acid as the copolymer component of the first polyester. When isophthalic acid is contained in a copolymer component of 1 mol% or more, good adhesion between the first film and the metal plate is obtained. Therefore, the content of isophthalic acid as the copolymer component of the first polyester is preferably 1 mol% or more, more preferably 2 mol% or more, and even more preferably 3 mol% or more. On the other hand, when isophthalic acid is contained in a copolymer component of 15 mol% or less, the first film becomes easier to mold. Therefore, the content of isophthalic acid as the copolymer component of the first polyester is preferably 15 mol% or less, more preferably 14 mol% or less, and even more preferably 8 mol% or less.

[0036] If the intrinsic viscosity of the first polyester is 0.65 dL / g or higher, the formability of the laminated metal sheet can be suitably obtained. Therefore, the intrinsic viscosity of the first polyester is preferably 0.65 dL / g or higher, and more preferably 0.70 dL / g or higher. On the other hand, if the intrinsic viscosity of the first polyester is 1.00 dL / g or lower, energy consumption in the polymerization and extrusion processes can be suitably suppressed. Therefore, the intrinsic viscosity of the first polyester is preferably 1.00 dL / g or lower, and more preferably 0.90 dL / g or lower.

[0037] The second polyester consists of either homopolybutylene terephthalate or copolymerized polybutylene terephthalate, or both. When the second polyester contains copolymerized polybutylene terephthalate, the content of the copolymerized component is preferably 1 mol% or more. On the other hand, if the content of the copolymerized component is 15 mol% or less, the crystallization rate of the first film is improved, and the deterioration of appearance due to whitening during retort sterilization treatment can be suppressed more effectively. Therefore, when the second polyester contains copolymerized polybutylene terephthalate, the content of the copolymerized component is preferably 15 mol% or less, and more preferably 10 mol% or less.

[0038] The copolymer components of the second polyester can be the acid and alcohol components described for the first polyester. Alternatively, ethylene glycol, the main component of the first polyester, can be used as the copolymer component. The copolymer components of the second polyester may consist of one or more of the aforementioned components.

[0039] If the intrinsic viscosity of the second polyester is 0.75 dL / g or higher, the formability of the laminated metal sheet can be suitably obtained. Therefore, the intrinsic viscosity of the second polyester is preferably 0.75 dL / g or higher, and more preferably 0.95 dL / g or higher. On the other hand, if the intrinsic viscosity of the second polyester is 1.30 dL / g or lower, energy consumption in the polymerization and extrusion processes can be suitably suppressed. Therefore, the intrinsic viscosity of the second polyester is preferably 1.30 dL / g or lower, and more preferably 1.20 dL / g or lower.

[0040] With the total amount of polyester in the first film set to 100, the mass ratio of the first polyester to the second polyester should be between 20:80 and 50:50.

[0041] If the content of the first polyester relative to the total polyester amount in the first film is less than 20% by mass, the adhesion between the first film and the metal plate will decrease. In this case, the first film may peel off from the metal plate when forming a laminated metal container or during retort sterilization. Therefore, the content of the first polyester relative to the total polyester amount in the first film should be 20% by mass or more, preferably 30% by mass or more. On the other hand, if the content of the first polyester relative to the total polyester amount exceeds 50% by mass, the crystallization rate of the first film will decrease, and the appearance of the film will deteriorate during retort sterilization. Therefore, the content of the first polyester relative to the total polyester amount in the first film should be 50% by mass or less, preferably 45% by mass or less.

[0042] If the content of the second polyester relative to the total polyester amount in the first film is less than 50% by mass, the crystallization rate of the first film decreases, and the appearance of the film deteriorates during retort sterilization. Therefore, the content of the second polyester relative to the total polyester amount in the first film should be 50% by mass or more, preferably 55% by mass or more. On the other hand, if the content of the second polyester relative to the total polyester amount exceeds 80% by mass, the adhesion between the first film and the metal plate decreases. In this case, the first film may peel off from the metal plate when forming a laminated metal container or during retort sterilization. Therefore, the content of the second polyester relative to the total polyester amount in the first film should be 80% by mass or less, preferably 70% by mass or less.

[0043] The two characteristic widths w1 and w2, calculated from the binarized images obtained by observing the cross-section of the first film using the dynamic force mode of a scanning probe microscope, shall satisfy the following equations (1) and (2). 10.0nm≦w1≦25.0nm (1) 10.0nm≦w2≦25.0nm (2) However, the threshold for binarization is determined by applying the percentile method to the phase lag such that, when areas with small phase lag are shown as dark, the area percentage of the dark area is equal to the mass percentage of the first polyester relative to the total amount of polyester in the first film. The characteristic width w1 is the value obtained by dividing the area of ​​the dark area after binarization by the length l1 of the thin wire obtained by performing a thin wire treatment on the dark area, and the characteristic width w2 is the value obtained by dividing the area of ​​the bright area after binarization by the length l2 of the thin wire obtained by performing a thin wire treatment on the bright area. The thin wire treatment can be performed using the Zhang-Suen method.

[0044] Figure 2 shows an example of a phase image obtained for the cross-section of the first film. Figure 3 shows the image obtained by binarizing Figure 2 using the method described above. In Figures 2 and 3, areas with small phase lag are shown as dark areas. Since polyethylene terephthalate has a higher elastic modulus than polybutylene terephthalate, the first polyester exhibits smaller phase lag compared to the second polyester. Therefore, the dark areas in Figures 2 and 3 correspond to the first polyester.

[0045] The characteristic width w1 is a value that represents the width of the dark area in Figure 3 and represents the dispersion state of the first polyester. Similarly, the characteristic width w2 is a value that represents the width of the bright area in Figure 3 and represents the dispersion state of the second polyester.

[0046] If the characteristic width w1 is less than 10.0 nm, the polyethylene terephthalate molecules and polybutylene terephthalate molecules are finely dispersed and nearly miscible, which reduces the crystallization rate of the first film and causes deterioration of the film's appearance due to whitening during retort sterilization. Therefore, the characteristic width w1 should be 10.0 nm or more, preferably 12.0 nm or more. On the other hand, if the characteristic width w1 exceeds 25.0 nm, the polyethylene terephthalate molecules and polybutylene terephthalate molecules are unevenly dispersed, which locally reduces the crystallization rate in the first film and causes deterioration of the film's appearance due to whitening during retort sterilization. Therefore, the characteristic width w1 should be 25.0 nm or less, preferably 20.0 nm or less.

[0047] If the characteristic width w2 is less than 10.0 nm, the polyethylene terephthalate molecules and polybutylene terephthalate molecules are finely dispersed and nearly miscible, which reduces the crystallization rate of the first film and causes deterioration of the film's appearance due to whitening during retort sterilization. Therefore, the characteristic width w2 should be 10.0 nm or more, preferably 12.0 nm or more. If the characteristic width w2 exceeds 25.0 nm, the polyethylene terephthalate molecules and polybutylene terephthalate molecules are unevenly dispersed, which locally reduces the crystallization rate in the first film and causes deterioration of the film's appearance due to whitening during retort sterilization. Therefore, the characteristic width w2 should be 25.0 nm or less, preferably 20.0 nm or less.

[0048] If one of the characteristic widths w1 and w2 is between 10.0 nm and 25.0 nm, and the other is less than 10.0 nm or greater than 25.0 nm, the polybutylene terephthalate molecules and polyethylene terephthalate molecules tend to adopt a dispersion state other than a co-continuous structure. As a result, the crystallization rate decreases, and the film appearance may deteriorate due to whitening during retort sterilization.

[0049] Preferably, the first polyester and the second polyester are dispersed in a co-continuous structure as shown in Figure 2 or Figure 3. The typical width of the co-continuous structure can be expressed as the ratio of the area of ​​each element constituting the co-continuous structure to the length of the fine wire when each element is finely thinned, which corresponds to the characteristic width of the present invention. Preferably, the typical width of the co-continuous structure is 10.0 nm or more and 25.0 nm or less. When the first polyester and the second polyester are dispersed in a co-continuous structure with a typical width of 10.0 nm or more and 25.0 nm or less, the first polyester, which has a slow crystallization rate, and the second polyester, which has a fast crystallization rate, are not compatible. Therefore, the crystallization rate of the entire first film is improved. In addition, in the above case, uneven dispersion of the first polyester and the second polyester can be suppressed, so a localized decrease in the crystallization rate can be suppressed, and deterioration of appearance due to whitening during retort sterilization can be suitably suppressed.

[0050] The characteristic width can be determined as follows: Observe the cross-section of the first film using a scanning probe microscope AFM5300E manufactured by Hitachi High-Tech Science Co., Ltd. Dissolve the laminated metal plate by immersing it in hydrochloric acid, and prepare an MD cross-section of the isolated first film using a microtome as a sample. A cantilever made of back-coated Al Si, manufactured by Hitachi High-Tech Fielding Co., Ltd., is used for the scanning probe microscope cantilever, and a 1 μm MD × 0.5 μmt field of view in the center of the film thickness direction is observed in DFM mode to obtain a phase image. Note that the phase image is observed so that areas with small phase lag are shown as darker.

[0051] For the obtained phase image, the percentile method is applied to the phase delay to determine the binarization threshold so that the area percentage equal to the mass percentage of the first polyester relative to the total amount of polyester in the first film becomes the dark area, and a binarized image is obtained. For the binarized image, the area A1 of the dark area is calculated using a program. The binarized image is then thinned using the Zhang-Suen method, and the length l1 of the thin lines is calculated. By dividing A1 by l1, the characteristic width w1 of the dark area is obtained. Similarly, for the binarized image, the area A2 of the bright area and the length l2 of the thin lines are calculated, and the characteristic width w2 of the bright area is obtained.

[0052] Further investigations by the inventors have led to the following findings: Laminated metal plates that show diffraction intensity below a certain magnification relative to the intensity of the amorphous halo in the wide-angle X-ray diffraction spectrum of a film on a laminated metal plate retain their film coverage even after advanced processing. Furthermore, in order to manufacture laminated metal plates that show only such weak diffraction intensity, it is preferable that the preheating temperature of the metal plate during lamination is a certain degree higher than the melting peak of the film.

[0053] It is preferable that the wide-angle X-ray diffraction spectrum for one side of the laminated metal plate with the first film attached satisfies the following equation (3). I(1) 100 / I(1) amorphous≤1.5 ···(3) Here, the wide-angle X-ray diffraction spectrum is measured using the θ-2θ method with CuKα rays at a sample angle where the plane formed by the incident and reflected X-rays is perpendicular to the plane of the first film. I(1) 100 This is the net intensity of the 100 diffraction peak of polyethylene terephthalate appearing at 2θ = 26.5 ± 1.0°, and I(1) amorphous This represents the net strength of the amorphous halo that appears at 2θ = 20.0 ± 5.0°.

[0054] I(1) 100 / I(1) amorphous When equation (3) is satisfied, the amount of polyethylene terephthalate crystals is small, and the moldability of the first film is improved. As a result, the breakage of the first film and metal plate when forming the laminated metal plate into a laminated metal container can be suitably suppressed, and the corrosion resistance of the laminated metal container can be suitably improved. Therefore, I(1) 100 / I(1) amorphous It is preferably 1.5 or less, and more preferably 1.0 or less. On the other hand, I(1) 100 / I(1) amorphous The lower limit is not particularly limited, but it is generally 0.2 or higher.

[0055] It is more preferable that the wide-angle X-ray diffraction spectrum for one side of the laminated metal plate with the first film attached satisfies the following equation (7). I(1') 100 / I(1) amorphous ≤1.5 ···(7) However, I(1') 100 This represents the net intensity of the 100-diffraction peak of polybutylene terephthalate appearing at 2θ = 23.5 ± 1.0°.

[0056] I(1') 100 / I(1) amorphousWhen equation (7) is satisfied, the amount of polybutylene terephthalate crystals is small, and the moldability of the first film is improved. As a result, the breakage of the first film and metal plate when forming the laminated metal plate into a laminated metal container can be suitably suppressed, and the corrosion resistance of the laminated metal container can be suitably improved. Therefore, I(1') 100 / I(1) amorphous It is preferably 1.5 or less, and more preferably 1.0 or less. On the other hand, I(1') 100 / I(1) amorphous The lower limit is not particularly limited, but I(1') 100 / I(1) amorphous The value is generally 0.7 or higher.

[0057] It is even more preferable that the first film does not show diffraction peaks other than amorphous halos in the wide-angle X-ray diffraction spectrum at 2θ = 10.0 to 30.0°. When no diffraction peaks other than amorphous halos are observed at 2θ = 10.0 to 30.0°, the amount of crystalline polyethylene terephthalate and polybutylene terephthalate is extremely small, which particularly improves the moldability of the first film. As a result, it is possible to suitably suppress the breakage of the first film and metal plate when forming the laminated metal plate into a laminated metal container, and also suitably improve the corrosion resistance of the laminated metal container.

[0058] Wide-angle X-ray diffraction spectra can be measured as follows. Measurements are performed using the θ-2θ method under the following conditions with a Rigaku SmartLab wide-angle goniometer. The laminated metal plate sample is rotated during the measurement. X-ray source: CuKα ray Tube voltage: 40kV Tube current: 40mA Entrance slit: 0.5° Incident parallel slit: 5.0° Light-receiving slit: 0.6mm Light-receiving parallel slit: 5.0° Monochromator slit: BBM Longitudinal limiting slit: 10.0 mm 2θ = 10.0 to 30.0° (0.1° / Step) Counting time: 8.0 seconds / step

[0059] For the obtained wide-angle X-ray diffraction spectrum, the background intensity, represented by the straight line connecting the diffraction intensities at 2θ=10.0° and 2θ=30.0°, is subtracted from the diffraction intensities at each 2θ to obtain the net intensity. In the measurement results, the peak appearing at 2θ=26.5±1.0° is attributed to the 100 diffraction of polyethylene terephthalate, and its intensity is defined as I(1). 100 This is assumed. Furthermore, if no clear peak appears at 2θ = 26.5 ± 1.0°, the maximum net intensity in the range of 2θ between 25.5° and 27.5° is used as I(1). 100 Let's assume that the intensity of the amorphous halo that appeared at 2θ = 20.0 ± 5.0° is I(1). amorphous Let's assume that.

[0060] Furthermore, in the measurement results, the peak that appeared at 2θ = 23.5 ± 1.0° was attributed to the 100-degree diffraction of polybutylene terephthalate, and its intensity was defined as I(1'). 100 This is assumed. Furthermore, if no clear peak appears at 2θ = 23.5 ± 1.0°, the maximum net intensity in the range of 2θ between 22.5° and 24.5° is used as I(1'). 100 Let's assume that.

[0061] Preferably, the first film has at least one melting peak temperature between 200°C and 230°C. The melting peak temperature is determined by differential scanning thermal analysis (DSC). If at least one melting peak temperature is 200°C or higher, the heat resistance of the first film is improved. Furthermore, if at least one melting peak temperature is 230°C or lower, deterioration of appearance due to whitening during retort sterilization can be suppressed.

[0062] Differential scanning thermal analysis can be performed as follows: The thermal properties of the first film are measured using a differential scanning thermal analyzer DSCQ100 manufactured by T.A. Instruments Japan Co., Ltd. The laminated metal plate is immersed in hydrochloric acid to dissolve the metal plate, and the isolated first film is used as a sample for analysis. 5 mg of film is taken as a sample, cut, and placed in an aluminum dish. The sample is cooled to -50°C under a nitrogen atmosphere, and the 1st Run is measured while raising the temperature to 290°C at a rate of 10°C / min. After measurement, the sample is held at 290°C for 5 minutes and then rapidly cooled with liquid nitrogen. Subsequently, the 2nd Run is measured again while raising the temperature from -50°C to 290°C at a rate of 10°C / min. From the chart obtained in the 2nd Run, the endothermic peak temperature between 120°C and 280°C is defined as the melting peak temperature.

[0063] In addition to the first polyester and the second polyester, the first film may also contain additives such as antioxidants, inorganic lubricants, organic lubricants, nucleating agents, heat stabilizers, antistatic agents, and coloring pigments.

[0064] The first film has suitable heat resistance when it contains an antioxidant in an amount of 0.0001% to 1.0000% by mass. Therefore, it is preferable to contain an antioxidant in an amount of 0.0001% to 1.0000% by mass. The antioxidant is not particularly limited, but known antioxidants such as hindered phenols, hydrazines, and phosphites can be used.

[0065] The handling properties of the first film are preferably obtained by containing an inorganic lubricant in an amount of 0.01% to 0.50% by mass. Therefore, it is preferable that the inorganic lubricant be contained in an amount of 0.01% to 0.50% by mass. The inorganic lubricant is not particularly limited, but known inorganic lubricants such as silicon dioxide, diatomaceous earth, and talc can be used.

[0066] Incidentally, the first film can also be composed of multiple layers in the thickness direction. Known methods can be used for laminating multiple layers, such as co-extrusion using a feed block or multi-manifold, laminating multiple films together, or directly laminating molten resin onto a film. To increase productivity and reduce energy consumption, it is preferable to use co-extrusion for laminating the first film.

[0067] When the first film is composed of multiple layers, it is preferable that the outermost layer contains an inorganic lubricant in an amount of 0.01% by mass or more and 0.50% by mass or less, while the layers other than the outermost layer either do not contain an inorganic lubricant or contain one in an amount of 0.01% by mass or less. For example, when the first film is composed of three layers: an air-side surface layer, a core layer, and a metal plate-side surface layer, an example configuration can be given in which the air-side surface layer and the metal plate-side surface layer contain an inorganic lubricant, while the core layer does not. By containing an inorganic lubricant only in the outermost layer, the amount of inorganic lubricant used can be reduced, making it economical.

[0068] The formability of the laminated metal sheet is improved by the inclusion of an organic lubricant in the first film in an amount of 0.01% to 1.00% by mass. Therefore, it is preferable that the first film contains an organic lubricant in an amount of 0.01% to 1.00% by mass. If the first film is composed of multiple layers, it is preferable that the outermost layer contains an organic lubricant in an amount of 0.01% to 1.00% by mass. The organic lubricant is not particularly limited, but known organic lubricants such as carnauba wax, polyolefin wax, and modified polyolefin wax can be used.

[0069] If the average thickness of the first film is 8 μm or more, better corrosion resistance can be ensured when the laminated metal sheet is formed into a laminated metal container. Therefore, the average thickness of the first film is preferably 8 μm or more, more preferably 10 μm or more, and even more preferably 13 μm or more. On the other hand, if the average thickness of the first film is 50 μm or less, the energy consumption required for heating during the manufacturing of the first film and the laminated metal sheet can be suitably suppressed. Therefore, the average thickness of the first film is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 25 μm or less.

[0070] If the sample standard deviation of the thickness of the first film is 10% or less of the average thickness of the first film, it is possible to suppress the breakage of the first film or metal plate when forming the laminated metal plate into a laminated metal container. Therefore, the sample standard deviation of the thickness of the first film is preferably 10% or less of the average thickness of the first film, and more preferably 5% or less. On the other hand, there is no particular lower limit to the sample standard deviation of the thickness of the first film, but this sample standard deviation is generally 0.05% or more.

[0071] The average and sample standard deviation of the first film's thickness can be determined as follows: Measure the thickness of the first film at 1 mm intervals along its longitudinal direction using a constant-pressure thickness gauge for a total length of 1,000 mm. The sample standard deviation and average can then be calculated from the measurement results.

[0072] [Second film] The second film consists of one or both of homopolyethylene terephthalate and copolymerized polyethylene terephthalate as polyester components. The total content of homopolyethylene terephthalate and copolymerized polyethylene terephthalate in the second film is preferably 70% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and may be 100% by mass. If the total content of homopolyethylene terephthalate and copolymerized polyethylene terephthalate in the second film is 70% by mass or more, the breakage of the second film and the metal sheet can be suitably suppressed when forming the laminated metal sheet into a laminated metal container.

[0073] If the second film contains copolymerized polyethylene terephthalate, the copolymer content is preferably 20 mol% or less, and more preferably 2 mol% or more and 16 mol% or less. The copolymer component of polyethylene terephthalate in the second film can be the acid component and alcohol component described for the first polyester. The copolymer component of polyethylene terephthalate in the second film may be only one of the above, or two or more may be used.

[0074] In differential scanning thermal analysis of the second film, if the highest endothermic peak temperature in the temperature range of 280°C or below is 220°C or higher, the heat resistance of the second film is improved. Therefore, it is preferable that the endothermic peak temperature of the second film is 220°C or higher. On the other hand, in the second film, the endothermic peak temperature is generally 260°C or lower. Note that differential scanning thermal analysis can be performed in the same manner as for the first film.

[0075] The wide-angle X-ray diffraction spectrum for the other side of the metal plate laminated with the second film preferably satisfies the following equation (4). I(2) 100 / I(2) amorphous ≤1.5 ···(4) However, the wide-angle X-ray diffraction spectrum is measured using the θ-2θ method with CuKα rays at a sample angle where the plane formed by the incident and reflected X-rays is perpendicular to the plane of the second film. I(2) 100 This is the net intensity of the 100 diffraction peak of polyethylene terephthalate appearing at 2θ = 26.5 ± 1.0°, and I(2) amorphous This represents the net strength of the amorphous halo that appears at 2θ = 20.0 ± 5.0°.

[0076] I(2) 100 / I(2) amorphous The value is preferably 1.5 or less, and more preferably 1.0 or less. When the wide-angle X-ray diffraction spectrum of the laminated metal sheet satisfies equation (4), the amount of polyethylene terephthalate crystals is small, which improves the moldability of the second film. As a result, it is possible to suppress the breakage of the second film and metal sheet when forming the laminated metal sheet into a laminated metal container, and also improve the corrosion resistance of the laminated metal container. On the other hand, I(2) 100 / I(2) amorphous The lower limit is not particularly limited, but I(2) 100 / I(2) amorphous The value is generally 0.2 or higher.

[0077] It is even more preferable that the second film does not show diffraction peaks other than amorphous halos in the wide-angle X-ray diffraction spectrum at 2θ = 10.0 to 30.0°. When no diffraction peaks other than amorphous halos are observed at 2θ = 10.0 to 30.0°, the amount of polyethylene terephthalate crystals is extremely small, which particularly improves the moldability of the second film. As a result, it is possible to effectively suppress the breakage of the second film and metal plate when forming the laminated metal plate into a laminated metal container, and to effectively improve the corrosion resistance of the laminated metal container.

[0078] The wide-angle X-ray diffraction spectrum of the second film can be measured in the same manner as the first film. If a clear peak does not appear at 2θ = 26.5 ± 1.0°, the maximum net intensity in the range of 2θ between 25.5° and 27.5° is used as I(2). 100 Let's assume that.

[0079] If the intrinsic viscosity of the second film is 0.60 dL / g or higher, the formation of minute cracks in the second film during the molding of the laminated metal sheet into a laminated metal container can be effectively suppressed. Therefore, the intrinsic viscosity of the second film is preferably 0.60 dL / g or higher, and more preferably 0.62 dL / g or higher. On the other hand, if the intrinsic viscosity of the second film is 1.10 dL / g or lower, the energy consumption in the polymerization and extrusion processes can be effectively suppressed. Therefore, the intrinsic viscosity of the second film is preferably 1.10 dL / g or lower, and more preferably 0.80 dL / g or lower.

[0080] The second film may contain additives such as antioxidants, inorganic lubricants, organic lubricants, nucleating agents, heat stabilizers, antistatic agents, and coloring pigments, in addition to homopolyethylene terephthalate and copolymerized polyethylene terephthalate.

[0081] If the second film contains an antioxidant in an amount of 0.0001% to 1.0000% by mass, the heat resistance of the second film can be preferably obtained. Therefore, it is preferable that the second film contains an antioxidant in an amount of 0.0001% to 1.0000% by mass. The antioxidant is not particularly limited, but known antioxidants such as hindered phenols, hydrazines, and phosphites can be used.

[0082] If the second film contains an inorganic lubricant in an amount of 0.01% to 0.50% by mass, the handling properties of the second film can be preferably obtained. Therefore, it is preferable that the second film contains an inorganic lubricant in an amount of 0.01% to 0.50% by mass. The inorganic lubricant is not particularly limited, but known inorganic lubricants such as silicon dioxide, diatomaceous earth, and talc can be used.

[0083] Incidentally, the second film can also be composed of multiple layers in the thickness direction. Known methods can be used for laminating multiple layers, such as co-extrusion using a feed block or multi-manifold, laminating multiple films together, or directly laminating molten resin onto a film. To increase productivity and reduce energy consumption, it is preferable to use co-extrusion for laminating the second film.

[0084] When the second film is composed of multiple layers, it is preferable that the outermost layer contains an inorganic lubricant in an amount of 0.01% by mass or more and 0.50% by mass or less, while the layers other than the outermost layer either do not contain an inorganic lubricant or contain one in an amount of 0.01% by mass or less. For example, when the second film is composed of three layers: an air-side surface layer, a core layer, and a metal plate-side surface layer, an example configuration can be given in which the air-side surface layer and the metal plate-side surface layer contain an inorganic lubricant, while the core layer does not. By containing an inorganic lubricant only in the outermost layer, the amount of inorganic lubricant used can be reduced, making it economical.

[0085] If the second film contains an organic lubricant in an amount of 0.01% to 3.00% by mass, the ease of removing contents from the laminated metal container is improved. Therefore, it is preferable that the second film contains an organic lubricant in an amount of 0.01% to 3.00% by mass. If the second film is composed of multiple layers, it is preferable that the outermost layer contains an organic lubricant in an amount of 0.01% to 3.00% by mass. The organic lubricant is not particularly limited, but known organic lubricants such as carnauba wax, polyolefin wax, and modified polyolefin wax can be used.

[0086] Furthermore, the second film may also contain a coloring pigment. By containing a coloring pigment in the second film, the underlying metal plate can be concealed, thereby enhancing the design. The coloring pigment is not particularly limited, but for example, white pigments, yellow pigments, etc., can be used.

[0087] As white pigments, for example, oxide ceramics such as aluminum oxide, titanium oxide, and zinc oxide, as well as talc, calcium carbonate, and barium sulfate can be used. From the viewpoint of dispersibility and whiteness, titanium oxide is particularly preferred as a white pigment, and rutile-type titanium oxide is more preferred.

[0088] As a yellow pigment, for example, isoindolinone yellow, disazo yellow, etc., can be used. From the viewpoint of heat resistance, disazo yellow is particularly preferred as the yellow pigment.

[0089] Furthermore, if the second film is composed of multiple layers, it is preferable to include coloring pigments in layers other than the outermost layer. By including coloring pigments in layers other than the outermost layer, it is possible to reduce manufacturing costs while maintaining the coloring effect, and it is also possible to prevent hygiene from being compromised by the pigments coming into contact with the contents.

[0090] The average thickness of the second film is preferably 8 μm or more, more preferably 10 μm or more, and even more preferably 13 μm or more, similar to the first film. On the other hand, the average thickness of the second film is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 25 μm or less, similar to the first film.

[0091] The sample standard deviation of the thickness of the second film is preferably 10% or less of the average thickness of the second film, and more preferably 5% or less, similar to the first film. On the other hand, there is no particular lower limit to the sample standard deviation of the thickness of the second film, but this sample standard deviation is generally 0.05% or more.

[0092] The mean and sample standard deviation of the second film's thickness can be determined in the same manner as the mean and sample standard deviation of the first film's thickness described above.

[0093] (Method of manufacturing laminated metal sheets) Next, a method for manufacturing a laminated metal sheet will be described. The method for manufacturing a laminated metal sheet includes the steps of: preheating a metal sheet to 300°C or below; then, using a laminating roll, heat-pressing film A onto at least one side of the metal sheet to form a heat-pressed body; and liquid-cooling the heat-pressed body to form a laminated metal sheet. A first film is obtained by applying the heat-pressing and cooling steps to film A, and a second film is obtained from film B in the same manner.

[0094] First, prepare a metal plate and film A, which will serve as the laminate base. Film A is a polyester film whose polyester component consists of a first polyester and a second polyester. The mass ratio of the first polyester to the second polyester in film A is set to 20:80 to 50:50, similar to the first film described above, with the total amount of polyester in film A set to 100.

[0095] It is preferable that the two characteristic widths w'1 and w'2, calculated from the binarized image of the phase image obtained by observing the cross-section of film A using the dynamic force mode of a scanning probe microscope before the thermocompression bonding process described later, satisfy the following equations (5) and (6). 8.0nm≦w'1≦17.0nm (5) 8.0nm≦w'2≦17.0nm (6)

[0096] The characteristic widths w'1 and w'2 can be determined in the same manner as the characteristic widths w'1 and w'2 in the first film described above. Specifically, the threshold value in binarization is determined by applying the percentile method to the phase lag such that, when areas with small phase lag are shown as dark, the area % of the dark area is equal to the mass % of the first polyester relative to the total amount of polyester in film A. The characteristic width w'1 is the value obtained by dividing the area A'1 of the dark area after binarization by the length l'1 of the fine lines obtained by performing a fine-line treatment on the dark area. The characteristic width w'2 is the value obtained by dividing the area A'2 of the bright area after binarization by the length l'2 of the fine lines obtained by performing a fine-line treatment on the bright area.

[0097] If the characteristic width w'1 or w'2 in film A of the laminate base is less than 8.0 nm, the polyethylene terephthalate molecules and polybutylene terephthalate molecules are finely dispersed and in a near-miscible state. Therefore, the characteristic widths w1 and w2 in the first film obtained from film A through the heat-sealing and cooling processes described later may not satisfy formulas (1) and (2). For this reason, characteristic widths w'1 and w'2 are preferably 8.0 nm or more. On the other hand, if the characteristic width w'1 or w'2 in film A of the laminate base exceeds 17.0 nm, the polyethylene terephthalate molecules and polybutylene terephthalate molecules are unevenly dispersed. Therefore, the characteristic widths w1 and w2 in the first film obtained from film A through the heat-sealing and cooling processes described later may not satisfy formulas (1) and (2). For this reason, characteristic widths w'1 and w'2 are preferably 17.0 nm or less.

[0098] Film A can be manufactured using various known methods. When manufacturing a laminated metal sheet by laminating film A onto a metal sheet, an extrusion coating method may be used in which the molten film A extruded from the T-die of an extruder is directly heat-pressed onto the metal sheet. Alternatively, film A may be manufactured on a separate film manufacturing line from the laminated metal sheet manufacturing line, and then film A and the metal sheet may be laminated on the laminated metal sheet manufacturing line. The method of manufacturing film A on a film manufacturing line will be described below. However, the present invention is not limited to the following description.

[0099] The production line for film A consists of, for example, an unstretched film production step in which an unstretched film is obtained from a resin composition using an extruder, a stretched film production step in which a stretched film is obtained by stretching the unstretched film, and a winding step in which the film is wound into a roll.

[0100] In the process of producing an unoriented film, raw material resins for the first polyester and the second polyester are used, along with additives such as antioxidants, inorganic lubricants, organic lubricants, nucleating agents, heat stabilizers, antistatic agents, and coloring pigments as needed. The raw material resins for the first polyester and the second polyester are preferably in pellet form. From the viewpoint of handling, the additives are preferably in the form of masterbatch pellets in which the additives are dispersed in the resin. The resin in which the additives are dispersed in the masterbatch pellets may be the first polyester or the second polyester, but from the viewpoint of economy, homopolyethylene terephthalate, which is used in general, is preferred. The pellets of raw material resin and additives can be mixed by dry blending to form a resin mixture. The resin mixture is dried under hot air or vacuum as needed before being supplied to an extruder.

[0101] The raw resin supplied to the extruder is heated above its melting point and melted. The additives and the molten raw resin are kneaded in the extruder to form a resin composition in which the first polyester, second polyester, and additives are dispersed. After foreign matter and modified resin are removed by filtering, the resin composition is extruded from a T-die and formed into a molten resin sheet. To improve the metering accuracy of the extrusion, it is preferable to install a feeder and a gear pump in the extruder. To omit the drying process of the resin mixture and to suppress hydrolysis during extrusion, it is preferable to install vacuum piping to reduce the pressure inside the extruder.

[0102] In this case, when forming film A with multiple layers, for example, film A can be formed by laminating multiple layers using a co-extrusion method. In this case, several extruders can be used, and feed blocks or multi-manifold dies can be used to melt-extrude the resin composition and other materials that will form each layer.

[0103] The molten resin sheet discharged from the T-die is cooled and solidified by a cooling device such as a cast roll to form an unstretched film. When cooling and solidifying the molten resin sheet, it is preferable to use electrostatic pinning or a vacuum chamber. By using these devices, the adhesion between the cast roll and the molten resin sheet can be improved, and a homogeneous unstretched film can be obtained.

[0104] In film A, for characteristic widths w'1 and w'2 to satisfy equations (5) and (6), it is preferable that the time from when the molten resin sheet is ejected from the T-die until it comes into contact with the cooling device is 0.20 to 0.80 seconds.

[0105] In the stretched film manufacturing process, the unstretched film is stretched in the film transport direction and / or the film width direction. Stretching in the film transport direction is called longitudinal stretching, and stretching in the film width direction is called transverse stretching. In the stretched film manufacturing process, either longitudinal stretching or transverse stretching alone may be performed, but sequential biaxial stretching, where longitudinal and transverse stretching are performed consecutively, or simultaneous biaxial stretching, where longitudinal and transverse stretching are performed simultaneously, may also be performed. Furthermore, the stretched film manufacturing process may be omitted.

[0106] Longitudinal stretching is performed, for example, in a longitudinal stretching machine equipped with a preheating roll and a stretching roll. The film before stretching is heated to a predetermined temperature as it passes through the preheating roll while being conveyed in the longitudinal direction. The film before stretching, which has been heated to the predetermined temperature by the preheating roll, is stretched in the longitudinal direction by a stretching roll that rotates at a faster conveying speed than the preceding roll. In addition to the preheating roll, an infrared heater may also be used to heat the film. It is preferable to install the infrared heater between the stretching roll and the roll immediately preceding it. By installing the infrared heater in this position, it is possible to suppress adhesion of the film to the preheating roll and reduce the torque during stretching.

[0107] Transverse stretching is performed, for example, by gripping the widthwise ends of the film with clips and widening the clip spacing in the film widthwise direction in a heating furnace. Preferably, the heating furnace is divided into several temperature zones from the inlet to the outlet.

[0108] Sequential biaxial stretching can be performed by carrying out the longitudinal stretching and the transverse stretching consecutively. The order in which the longitudinal and transverse stretching are performed can be determined as appropriate, and for example, longitudinal stretching can be performed once each, followed by another longitudinal stretching.

[0109] Simultaneous biaxial stretching can be performed, for example, by widening the clip spacing in the film's width direction and simultaneously widening the clip spacing in the film's longitudinal direction during the transverse stretching process.

[0110] In all stretching methods, including longitudinal stretching, transverse stretching, sequential biaxial stretching, and simultaneous biaxial stretching, the maximum temperature of the film is preferably above the glass transition temperature of the unstretched film. Furthermore, the ratio of the length of the film before and after stretching in the stretching direction is called the stretching ratio, and the stretching ratio is preferably between 2.0 and 9.0.

[0111] In the stretched film manufacturing process, a heat-setting treatment may be performed. This treatment can be carried out, for example, by sequentially biaxial stretching the film, then raising its temperature to a level higher than the film's highest temperature during stretching, and loosening the tension of the film as needed. Heat-setting treatment can improve the film's heat resistance and suppress dimensional changes over time.

[0112] In the winding process, the unstretched or stretched film is wound into a roll to obtain a film roll. Before winding into a roll, it is preferable to use quality inspection equipment such as a thickness gauge or defect detector to inspect the quality of the film. The quality inspection equipment may be installed in the unstretched film production process or the stretched film production process, but it is more effective to install it in the winding process, which is the final process in the film manufacturing line.

[0113] Furthermore, it is preferable to use a trimmer to remove the widthwise edges of the film before winding it into a roll. Applying a trimmer helps to standardize the width of the film, contributes to the stable manufacturing of laminated metal sheets, and suppresses fold defects at the widthwise edges of the film.

[0114] In trimmers, the application of oscillation rolling, which causes the film to pass through while oscillating in the width direction, is preferable. Oscillation rolling can suppress gauge band defects, which occur when thickness variations in the width direction of the film accumulate, resulting in unevenness in the width direction of the film roll.

[0115] Film B, like film A described above, can be manufactured using various known methods. Furthermore, it is preferable that the polyester component of film B consists of one or both of homopolyethylene terephthalate and copolymerized polyethylene terephthalate.

[0116] [Thermocompression bonding process] In the thermocompression bonding process, a preheated metal plate and film A are thermocompressed together using a laminating roll to create a thermocompressed body. The thermocompression bonding process is carried out by thermocompressing film A onto at least one of the front or back surfaces of the metal plate. The metal plate used is cast and rolled to a predetermined thickness and width, and then subjected to surface treatments such as annealing, temper rolling, and plating as needed.

[0117] The heat-pressing process involves placing film A between a metal plate preheated to a predetermined temperature and a laminating roll, and then pressing film A against the metal plate with the laminating roll. During this process, film A melts due to the heat of the metal plate and is pressed against it.

[0118] The surface temperature of the metal plate 0.5 seconds before it comes into contact with film A is called the preheating temperature of the metal plate. If the preheating temperature of the metal plate exceeds 300°C, there is a risk that film A will completely melt and adhere to the laminating roll while it is in contact with the laminating roll. If the film adheres to the laminating roll, irregularities will be created on the roll surface, and these irregularities may be transferred to the subsequent laminated metal plate, creating a pattern. Therefore, the preheating temperature of the metal plate is preferably 300°C or lower. In addition, the preheating temperature of the metal plate is generally 230°C or higher.

[0119] The preheating temperature of the metal plate is preferably -10°C or higher than the highest endothermic peak temperature in the temperature range of 280°C or lower as measured by differential scanning thermal analysis of film A. When the preheating temperature of the metal plate is -10°C or higher than the said endothermic peak temperature, it is possible to effectively prevent crystals of the first polyester or second polyester in film A from remaining on the laminated metal plate and reducing processability. On the other hand, when the preheating temperature of the metal plate is +50°C or lower than the said endothermic peak temperature, it is possible to effectively prevent film A from completely melting and adhering to the laminate roll while in contact with it. If film A adheres to the laminate roll, irregularities will be created on the roll surface, and these irregularities may be transferred to the subsequent laminated metal plate, potentially creating a pattern. Therefore, it is preferable that the preheating temperature of the metal plate is +50°C or lower than the said endothermic peak temperature. The preheating temperature of the metal plate is more preferably between -10°C and +50°C relative to the highest endothermic peak temperature in the temperature range of 280°C or less observed in the differential scanning thermal analysis of film A.

[0120] In differential scanning thermal analysis of film A, the endothermic peak temperature, which is the highest temperature below 280°C, corresponds to the melting peak temperature of the first polyester in film A. The differential scanning thermal analysis is described above.

[0121] In the heat-pressing process, film A, a preheated metal plate, and film B may be heat-pressed together in this order to form a heat-pressed body. In this case, the heat-pressing process is carried out by heat-pressing film A onto one side of the metal plate (either the front or back surface) and heat-pressing film B onto the other side.

[0122] When heat-pressing film A and film B onto a metal plate, they may be heat-pressed sequentially, but it is preferable to heat-press them onto the metal plate simultaneously. Heat-pressing film A and film B onto the metal plate simultaneously has the effect of suppressing the energy consumption required to heat the metal plate and simplifying the equipment configuration.

[0123] When heat-pressing film A and film B onto a metal plate, it is preferable to preheat the metal plate to a temperature of 300°C or lower, as this prevents film A and film B from completely melting and adhering to the laminating roll while they are in contact with it.

[0124] The preheating temperature of the metal plate is preferably between -5°C and +60°C relative to the highest endothermic peak temperature in the temperature range of 280°C or less as measured by differential scanning thermal analysis of film B. If the preheating temperature of the metal plate is between -5°C and +60°C relative to the endothermic peak temperature, it is possible to effectively prevent film B from completely melting and adhering to the laminating roll while in contact with it. Furthermore, the polyethylene terephthalate in film B can be sufficiently amorphous, improving the processability of the laminated metal plate. The differential scanning thermal analysis is as described above.

[0125] Films A and B used in the heat-sealing process may be preheated. It is preferable to preheat film A to a temperature of 40°C to 150°C. It is preferable to preheat film B to a temperature of 70°C to 180°C. Preheating film A or film B within these temperature ranges allows for smooth transport of film A or film B and suppresses the preheating temperature of the metal plate.

[0126] If the pressure applied by the laminating roll is 0.35 MPa or higher, it is possible to suppress the entrapment of air bubbles at the interface between the metal plate and film A or film B, thereby improving the adhesion between the metal plate and film A or film B. Therefore, the pressure applied by the laminating roll is preferably 0.35 MPa or higher, and more preferably 0.40 MPa or higher. On the other hand, if the pressure applied by the laminating roll is 1.50 MPa or lower, it is possible to suppress the amount of heat transferred from the metal plate through film A or film B to the laminating roll, thereby effectively suppressing energy consumption and wear of the laminating roll. Therefore, the pressure applied by the laminating roll is preferably 1.50 MPa or lower, and more preferably 1.40 MPa or lower.

[0127] The laminating roll is preferably heated to a temperature in the range of -20°C to +50°C relative to the glass transition temperature of film A. Heating the laminating roll mitigates spontaneous temperature rise due to heat input from the metal plate, thereby suppressing variations in the properties of film A in the longitudinal direction. The glass transition temperature of film A is determined as follows: Film A is heated from -50°C to 290°C at a rate of 10°C / min, and differential scanning thermal analysis is performed. The average temperature is calculated from the two intersection points (glass transition start temperature and glass transition end temperature) of the baseline before and after the shift, and the tangent line at the inflection point during the shift, and this is defined as the glass transition temperature.

[0128] Furthermore, it is preferable that the laminating roll in contact with film B be heated to a temperature in the range of -20°C to +50°C relative to the glass transition temperature of film B. By heating the laminating roll in contact with film B in this manner, spontaneous temperature rise due to heat input from the metal plate can be mitigated, and variations in the properties of film B in the longitudinal direction can be suppressed. The glass transition temperature of film B can be determined in the same manner as the glass transition temperature of film A.

[0129] [Cooling process] In the cooling process, the heat-sealed body is liquid-cooled within 2 seconds of the heat-sealing process. In the cooling process, the heat-sealed body may be cooled by spraying it with a coolant or by immersing it in a coolant. Examples of coolants used for cooling include water, oils such as silicone oil, and organic solvents, but water is particularly preferred, and deionized water or distilled water is more preferred. When deionized water or distilled water is used as a coolant, the amount of impurities such as minerals is low, so the precipitation of impurities can be suppressed even when drying is performed after the cooling process. When industrial water or tap water is used as a coolant, it is preferable to rinse with deionized water or distilled water after rapid cooling to prevent appearance defects due to the precipitation of impurities.

[0130] If the surface temperature of film A in the heat-sealed body exceeds 205°C immediately before cooling in the cooling process, the first polyester and second polyester in film A will remain miscible during the heat-sealing process and their dispersion state will be fixed. As a result, the crystallization rate of the entire film A will decrease, and the appearance of the film may deteriorate due to whitening during retort sterilization. Therefore, the surface temperature should be 205°C or lower, preferably 200°C or lower, and more preferably 195°C or lower. On the other hand, if the surface temperature of film A in the heat-sealed body is 170°C or higher immediately before cooling in the cooling process, it is possible to effectively prevent the crystallization of polyethylene terephthalate molecules in film A from progressing and deteriorating the processability of the laminated metal plate. Therefore, the surface temperature should be 170°C or higher, more preferably 180°C or higher, and even more preferably 185°C or higher.

[0131] In the cooling process, the surface temperature of film A on the heat-sealed body immediately before cooling is preferably 170°C to 210°C, more preferably 180°C to 200°C, and even more preferably 185°C to 195°C. The surface temperature of film A on the heat-sealed body immediately before cooling is the surface temperature measured 0.2 seconds before cooling.

[0132] In the heat-pressing process, if the time from when film A is separated from the laminating roll until film A is cooled in the cooling process is 2.0 seconds or less, the crystallization of polyethylene terephthalate molecules in film A can be suitably suppressed. In addition, the processability of the laminated metal sheet can be improved. Therefore, the time is preferably 2.0 seconds or less, and more preferably 1.5 seconds or less. On the other hand, if the time is 0.2 seconds or more, the temperature difference that occurred in the thickness direction within film A while in contact with the laminating roll is eliminated when it is separated from the laminating roll, and the temperature distribution in the thickness direction within film A becomes uniform. Therefore, variations in the physical properties within film A can be effectively suppressed, and the processability of the laminated metal sheet can be suitably obtained. Therefore, the time is preferably 0.2 seconds or more, more preferably 0.5 seconds or more, and even more preferably 0.8 seconds or more. Furthermore, the time is preferably 0.2 seconds or more and 2.0 seconds or less, and more preferably 0.5 seconds or more and 1.5 seconds or less.

[0133] During the cooling process, the refrigerant may be heated to ensure operational stability. If the refrigerant temperature is 10°C or higher, freezing in the refrigerant tank and contamination due to condensation in the piping can be effectively suppressed. Therefore, it is preferable that the refrigerant temperature be 10°C or higher. On the other hand, if the refrigerant temperature is 40°C or less above the glass transition temperature of film A, film A can be smoothly conveyed to the pass line roll installed after the cooling process without sticking. Therefore, it is preferable that the refrigerant temperature is 40°C or less above the glass transition temperature of film A.

[0134] After cooling, the refrigerant is removed from the heat-sealed body by a squeezing roll. The heat-sealed body is subjected to post-heat treatment and oiling treatment as needed. After being inspected for surface defects, internal defects, plate thickness, etc., as needed, the heat-sealed body is wound into a coil shape on a tension reel, for example, to become a laminated metal sheet. The heat-sealed body may also be formed into a sheet-like laminated metal sheet by slitting or shearing.

[0135] (Laminated metal container) The left side of Figure 1 shows the structure of the laminated metal container 100. The laminated metal container 100 is formed in a cylindrical shape with a bottom and is equipped with a lid that closes the container as needed. The laminated metal container 100 can be used, for example, for canned food, beverage cans, 18L cans, etc.

[0136] The laminated metal container may be either a three-piece can made by joining three components: a lid, a body, and a bottom, or a two-piece can made by joining two components: a lid and a body. Furthermore, the laminated metal container may have an opening on one end of the body, for example, by omitting the lid.

[0137] The laminated metal container includes the laminated metal sheet described above. The laminated metal container is formed using the laminated metal sheet as the material for at least one of its constituent components.

[0138] The body of a two-piece can is formed by various molding methods such as DRD molding, DI molding, and DTR molding. In particular, DI molding and DTR molding are molding methods that involve ironing, and the laminated metal sheet before molding requires high workability. The laminated metal sheet of the present invention has high formability and can be suitably used in any of the above molding methods. Forming into a laminated metal container is done by known methods. Laminated metal containers can be efficiently formed, for example, by using a can-making machine.

[0139] Laminated metal containers may be painted, printed, or wrapped in paper. Laminated metal containers are particularly suitable for use as containers that are subjected to retort sterilization.

[0140] In the above-described embodiment, an example was explained in which the laminated metal plate has a front surface, which is the outer surface of the laminated metal container, and a back surface, which is the inner surface. The laminated metal plate can be freely provided according to the mode of implementation. For example, the front surface of the metal plate may be provided as the inner surface of the laminated metal container, and the back surface may be provided as the outer surface of the laminated metal container. In this case, the first film may be provided only on the front surface, which is the inner surface of the laminated metal container.

[0141] As described above, the laminated metal sheet according to the present invention can maintain the coating properties of the first film and / or the second film on the metal sheet even after undergoing advanced processing. Furthermore, the laminated metal container according to the present invention can suppress deterioration of appearance due to whitening even after retort sterilization treatment.

[0142] For processes and conditions not described in this specification, conventional methods may be used. [Examples]

[0143] The present invention will be described in more detail below with reference to examples, but is not necessarily limited thereto.

[0144] (Example of Invention 1) TFS was used as the metal sheet. As the base metal for the TFS, a low-carbon steel with a temper grade of T3CA and a thickness of 0.22 mm was used, which had undergone cold rolling, annealing, and temper rolling. The low-carbon steel was degreased, pickled, and then chromium-plated to produce the TFS. The amount of chromium plating on the TFS was 120 mg / m² in terms of metallic chromium (Cr equivalent). 2 Chromium hydrated oxide is 10 mg / m³ 2 That was it.

[0145] A polyester film containing a first polyester and a second polyester was prepared as film A to be laminated on the surface of a metal plate. As the raw material for the first polyester, a first pellet made of copolymerized polyethylene terephthalate obtained by copolymerizing isophthalic acid and diethylene glycol was prepared. As the raw material for the second polyester, a second pellet made of homopolybutylene terephthalate was prepared. As an additive, an inorganic lubricant masterbatch pellet was prepared in which 0.8% by mass of silicon dioxide was dispersed in homopolyethylene terephthalate. Each pellet was dry-blended in the mass ratios shown in Table 1 to form a resin mixture, which was then heated to 150°C under vacuum and dried for 3 hours.

[0146] The dried resin mixture was fed into an extruder and melt-kneaded at 275°C. Next, after removing foreign matter through a sintering filter, the mixture was extruded from a T-die and cooled and solidified on a cast roll with a controlled surface temperature of 30°C 0.45 seconds later to obtain an unstretched film. Then, longitudinal stretching was performed to obtain a stretched film. The stretching temperature was 70°C and the stretching ratio was 4.0 times. Finally, the stretched film was trimmed to remove uneven thickness at the widthwise edges, and the film was wound into a roll to obtain film A with a thickness of 20 μm. The sample standard deviation of the thickness of film A was 4%.

[0147] A copolymerized polyethylene terephthalate film was prepared as film B to be laminated on the back surface of a metal plate. As raw materials, a first pellet consisting of copolymerized polyethylene terephthalate obtained by copolymerizing isophthalic acid and diethylene glycol was prepared. As an additive, an inorganic lubricant masterbatch pellet was prepared in which 0.8% by mass of silicon dioxide was dispersed in homopolyethylene terephthalate. The copolymerized polyethylene terephthalate resin pellet and the inorganic lubricant masterbatch pellet were dry-blended in a ratio of 95% by mass and 5% by mass to form a resin mixture, which was then heated to 150°C under vacuum and dried for 3 hours.

[0148] The dried resin mixture was fed into an extruder and melt-kneaded at 275°C. Next, after removing foreign matter through a sintering filter, the mixture was extruded from the T-die and cooled and solidified on a cast roll with a controlled surface temperature of 30°C 0.45 seconds later to obtain an unstretched film. Then, longitudinal stretching was performed to obtain a stretched film. The stretching temperature was 90°C and the stretching ratio was 4.5 times. Finally, the stretched film was trimmed to remove uneven thickness at the widthwise edges, and the film was wound into a roll to obtain film B with a thickness of 20 μm. The sample standard deviation of the thickness of film B was 3%.

[0149] Next, the metal plate, film A, and film B were laminated using a thermocompression lamination method. A pair of laminating rolls were positioned to sandwich the front and back surfaces of the metal plate. Film A was placed between the front surface of the metal plate and the laminating roll on the front side, and film B was placed between the back surface of the metal plate and the laminating roll on the back side. Lamination was performed by passing the preheated metal plate between the laminating rolls. The preheating temperature of the metal plate was 241°C, film A was 50°C, film B was 80°C, and the temperature of the laminating rolls was 80°C.

[0150] After the metal plate passed through the laminating roll and film A separated from the laminating roll on the front side, tap water heated to 60°C was sprayed to cool it 1.0 second later, resulting in a laminated metal plate with the first film and the second film laminated on the front and back surfaces, respectively. The pressure applied by the laminating roll was adjusted so that the surface temperature of film A immediately before cooling (temperature just before cooling) was 198°C. At this time, the pressure applied by the laminating roll was 0.60 MPa.

[0151] (Examples 2-6 of the invention, Comparative Examples 1-3) Laminated metal sheets were obtained using the conditions shown in Tables 1 and 2, respectively, for the types, mass ratios, and intrinsic viscosity of the first and second polyester raw materials in film A, the types and intrinsic viscosity of the raw materials in film B, the preheating temperature of the metal sheet in the thermocompression bonding process, and the temperature immediately before cooling. Other conditions were the same as in Invention Example 1. Note that "Polyester ratio" in Table 1 indicates the mass ratio to the total amount of polyester.

[0152] For each example, observation using a scanning probe microscope, measurement of wide-angle X-ray diffraction spectra, and differential scanning thermal analysis were performed using the methods described above. The results are shown in Tables 1 and 2.

[0153] [Table 1]

[0154] [Table 2]

[0155] (Primary adhesion) A sample measuring 120 mm in the transport direction and 15 mm in the width direction was cut from a laminated metal sheet. A portion of the film was peeled off from the long edge of the cut sample. The peeled film was opened in the opposite direction to the peeling direction (angle: 180°), and a peel test was performed using a tensile testing machine at a tensile speed of 30 mm / min. The adhesion strength per 15 mm width was evaluated according to the following scoring system. ◎: 10.0N / 15mm or more ○: 5.0N / 15mm or more, less than 10.0N / 15mm ×: 5.0N / less than 15mm

[0156] (Adhesion after retort sterilization) A sample measuring 100 mm in the transport direction and 30 mm in the width direction was cut from a laminated metal sheet. A portion of the film was peeled off from the long edge of the cut sample. The peeled film was opened in the opposite direction to the peeling direction (angle: 180°), a 100 g weight was fixed in place, and the sample was retort sterilized for 25 minutes under pressurized steam at 125°C. The peeled length of the film after retort sterilization was measured and evaluated according to the following scoring system. ◎: Less than 2mm ○: 2mm or more, less than 10mm ×: 10mm or more

[0157] (Appearance after retort sterilization) A φ48 sample was punched out from a laminated metal plate. The sample was attached to the bottom of a commercially available 350 mL negative-pressure steel can (φ66, height 122.2 mm) using a donut-shaped magnet with an outer diameter of φ50 and an inner diameter of φ30. The steel can with the attached sample was retort sterilized under pressurized steam at 130°C for 10 minutes. After retort sterilization, the sample was removed from the steel can, and the changes in appearance were observed visually and evaluated according to the following scoring system. ◎: No change in appearance ○: Slight whitening on the exterior (less than 5% of the area) ×: The appearance is cloudy (more than 5% by area).

[0158] (Processability of laminated metal sheets) After applying paraffin wax to a laminated metal sheet, a φ123 sample was punched out. The sample was then drawn to obtain a shallow-drawn metal container with an inner diameter of φ71 and a height of 36 mm. The obtained shallow-drawn can was loaded into a DI molding machine and molded with a punch speed of 200 mm / s and a stroke of 560 mm, using re-drawing and three stages of ironing to achieve a total reduction rate of 50%. Finally, a laminated metal container with an inner diameter of 52 mm and a height of 90 mm was obtained. Tap water was circulated at a temperature of 50°C during the DI molding process. After can manufacturing, the tear (scratch) area ratio of the first film was evaluated according to the following scoring system. ◎: Scratch area ratio less than 5% ○: Scratch area ratio 5% or more but less than 15% ×: Scratch area ratio of 15% or more

[0159] (Evaluation results) Table 3 shows the evaluation results of the laminated metal plates obtained for Invention Examples 1-5 and Comparative Examples 1-3. Furthermore, Figure 2 shows the phase image of the cross-section of the first film of Invention Example 1, obtained by observation using the dynamic force mode of a scanning probe microscope, and Figure 4 shows the phase image of the cross-section of the first film of Comparative Example 1.

[0160] [Table 3]

[0161] Examples 1 to 6 of the invention yielded good results in all evaluations of primary adhesion, adhesion after retort sterilization, and appearance after retort sterilization. On the other hand, Comparative Examples 1 to 3 showed deterioration in appearance after retort sterilization. Therefore, it was confirmed that the present invention can provide laminated metal sheets and laminated metal containers that have excellent primary adhesion and adhesion after retort sterilization, and do not show deterioration in appearance due to whitening after retort sterilization. Furthermore, in Examples 1 to 2, 5, and 6 of the invention, where the preheating temperature and wide-angle X-ray diffraction spectrum of the metal sheet were within a suitable range, good results were obtained in the evaluation of the processability of the laminated metal sheet. [Industrial applicability]

[0162] According to the present invention, it is possible to provide a laminated metal sheet, a method for manufacturing the same, and a laminated metal container using the laminated metal sheet, which have excellent primary adhesion and adhesion after retort sterilization, and which do not deteriorate in appearance due to whitening even after retort sterilization. [Explanation of symbols]

[0163] 100 Laminated metal containers 10 Laminated metal plate 20 metal plate 21 Front surface of the metal plate 22 Back side of the metal plate 31 Film No. 1 32. Second film

Claims

1. A laminated metal plate in which a first film is laminated on at least one surface of a metal plate, The first film is a polyester film whose polyester component consists of a first polyester and a second polyester. The first polyester consists of one or both of homopolyethylene terephthalate and copolymerized polyethylene terephthalate. The second polyester consists of one or both of homopolybutylene terephthalate and copolymerized polybutylene terephthalate. With the total amount of polyester in the first film set to 100, the mass ratio of the first polyester to the second polyester is 20:80 to 50:

50. A laminated metal plate wherein two characteristic widths w1 and w2, calculated from a binarized image of a phase image obtained by observing the cross-section of the first film using the dynamic force mode of a scanning probe microscope, satisfy the following equations (1) and (2). 10.0nm≦w1≦25.0nm...(1) 10.0nm≦w2≦25.0nm...(2) However, the threshold value in the binarization is determined by applying the percentile method to the phase lag such that, when areas with small phase lag are shown as dark, the area percentage of the dark area is equal to the mass percentage of the first polyester relative to the total amount of polyester in the first film. The characteristic width w1 is the value obtained by dividing the area A1 of the dark area after binarization by the length l1 of the thin line obtained by applying a thinning process to the dark area. The characteristic width w2 is the value obtained by dividing the area A2 of the bright area after binarization by the length l2 of the thin line obtained by applying a thinning process to the bright area.

2. The laminated metal plate according to claim 1, wherein the wide-angle X-ray diffraction spectrum for at least one surface of the metal plate on which the first film is laminated satisfies the following formula (3). I(1) １００ / I(1) ａｍｏｒｐｈｏｕｓ ≦1.5 ・・・(3) Here, the wide-angle X-ray diffraction spectrum is measured using the θ-2θ method with CuKα rays at a sample angle where the plane formed by the incident X-rays and reflected X-rays is perpendicular to the plane of the first film. I (1) １００ This is the net intensity of the 100 diffraction peak of polyethylene terephthalate appearing at 2θ = 26.5 ± 1.0°. I (1) ａｍｏｒｐｈｏｕｓ This represents the net strength of the amorphous halo that appears at 2θ = 20.0 ± 5.0°.

3. A second film is laminated on the other surface of the aforementioned metal plate. The second film comprises a polyester component consisting of one or both of homopolyethylene terephthalate and copolymerized polyethylene terephthalate. In differential scanning thermal analysis of the second film, the highest endothermic peak temperature in the temperature range of 280°C or less is 220°C or higher. The laminated metal plate according to claim 1 or 2, wherein the wide-angle X-ray diffraction spectrum of the other surface of the metal plate on which the second film is laminated satisfies the following formula (4). I(2) １００ / I(2) ａｍｏｒｐｈｏｕｓ ≦1.5 ・・・(4) Here, the wide-angle X-ray diffraction spectrum is measured using the θ-2θ method with CuKα rays at a sample angle where the plane formed by the incident X-rays and reflected X-rays is perpendicular to the plane of the second film. I (2) １００ This is the net intensity of the 100 diffraction peak of polyethylene terephthalate appearing at 2θ = 26.5 ± 1.0°. I (2) ａｍｏｒｐｈｏｕｓ This represents the net strength of the amorphous halo that appears at 2θ = 20.0 ± 5.0°.

4. A process of preheating a metal plate to a preheating temperature of 300°C or less, Subsequently, a heat-pressing step is performed in which film A is heat-pressed onto at least one surface of the metal plate using a laminating roll to form a heat-pressed body. A cooling step in which the heat-sealed body is liquid-cooled to form a laminated metal plate, It has, The aforementioned film A is a polyester film whose polyester component consists of a first polyester and a second polyester. The first polyester consists of one or both of homopolyethylene terephthalate and copolymerized polyethylene terephthalate. The second polyester consists of one or both of homopolybutylene terephthalate and copolymerized polybutylene terephthalate. With the total amount of polyester in film A set to 100, the mass ratio of the first polyester to the second polyester is 20:80 to 50:

50. In the cooling process, immediately before being cooled, the surface temperature of the film A on the heat-sealed body is 205°C or lower. A method for manufacturing a laminated metal plate, wherein two characteristic widths w'1 and w'2, calculated from a binarized image of a phase image obtained by observing the cross-section of the film A using the dynamic force mode of a scanning probe microscope prior to the thermocompression bonding step, satisfy the following equations (5) and (6). 8.0nm≦w'1≦17.0nm...(5) 8.0nm≦w'2≦17.0nm...(6) However, the threshold value in the binarization is determined by applying the percentile method to the phase lag such that, when areas with small phase lag are shown as dark, the area percentage of the dark area is equal to the mass percentage of the first polyester relative to the total amount of polyester in the film A. The characteristic width w'1 is the value obtained by dividing the area A'1 of the dark region after binarization by the length l'1 of the thin line obtained by applying a thinning process to the dark region. The characteristic width w'2 is the value obtained by dividing the area A'2 of the bright area after binarization by the length l'2 of the thin line obtained by applying a thinning process to the bright area.

5. The method for manufacturing a laminated metal plate according to claim 4, wherein the preheating temperature is between -10°C and +50°C relative to the highest endothermic peak temperature in the temperature range of 280°C or less as determined by differential scanning thermal analysis of the film A.

6. In the heat-pressing process, film B is heat-pressed onto the other side of the metal plate. The aforementioned film B consists of one or both of homopolyethylene terephthalate and copolymerized polyethylene terephthalate as its polyester component. In differential scanning thermal analysis of the aforementioned film B, the highest endothermic peak temperature in the temperature range of 280°C or less was 220°C or higher. The method for manufacturing a laminated metal plate according to claim 4 or 5, wherein the preheating temperature of the metal plate is -5°C or more and +60°C or less relative to the endothermic peak temperature of the film B.

7. A laminated metal container comprising a laminated metal plate according to claim 1 or 2.

8. A laminated metal container comprising the laminated metal plate described in claim 3.

Images