Coating replacement film, laminate, metal member, vehicle exterior part, and method for producing laminate

Abstract

A coating replacement film including a laminated film including a layer A and a layer B, the layer B having a planar orientation coefficient of 1.65-1.80, the melting point TmB of the layer B being higher than the melting point TmA of the layer A, the difference in melting point TmB-TmA being 25-35 DEG C, the difference in melting point TmB-TmA being greater than the difference in melting point TmB-TmA being greater than the difference in melting point TmB-TmA in any of the flow direction and the width direction of the laminated film. The residual rate of internal stress (specifically the residual rate of internal stress determined by 1-(Ub / Ua) * 100) in a tensile test at 100 DEG C is 25% or less.

Description

Technical Field

[0001] The present invention relates to a paint-substitute film that replaces painting of metal such as an outer panel of a vehicle such as an automobile by covering it with a film, thereby exhibiting good adhesion to the metal and excellent appearance design. Background Art

[0002] In the past, spray painting was usually used to improve the design of metal exterior parts of vehicles. However, in recent years, in the painting process including such spray painting, painting and drying are repeated, so large equipment and space are required, and productivity is reduced. Therefore, in order to rationalize the painting process, a method of sticking a decorative film (hereinafter referred to as a paint replacement film) on the aforementioned exterior parts to improve the appearance of the product has been studied.

[0003] Patent Document 1 proposes a heat-sealable film as a film for physically bonding metal foils and metal plates. Specifically, by using a polyester B layer with a refractive index in the thickness direction of "1.500 or more" and a heat-seal layer with a thickness of 4 to 40 μm formed of a polymer with a number average molecular weight of 15,000 or more in contact with the polyester B layer, interlayer delamination in the B layer is suppressed, and the decrease in adhesive strength is reduced.

[0004] Patent document 2 proposes that in a two-layer polyester film consisting of a B layer and an adhesive layer, by making the refractive index of the B layer in the thickness direction less than 1.500 and making the melting point difference between the aforementioned B layer and the adhesive layer more than 20°C, the film has an excellent appearance design required for the outer panels of automobiles, etc., and can exhibit good adhesion to metals.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2006-1114

[0008] Patent Document 2: Japanese Patent Application Publication No. 2020-192787 Summary of the invention

[0009] Problem that the invention aims to solve

[0010] When a laminated metal sheet obtained by laminating a coating alternative film on a metal sheet for a vehicle, such as a steel sheet, an aluminum alloy sheet, etc., is press-formed into a vehicle exterior component, if the metal sheet and the coating alternative film are not sufficiently adhered to each other, the film may be damaged or peeled off due to a springback phenomenon immediately after forming. The main object of the present invention is to provide a coating alternative film that exhibits excellent adhesion to a metal sheet during press forming and shows an excellent appearance design for the purpose of a vehicle exterior component.

[0011] Solutions for solving problems

[0012] The inventors of the present invention have conducted in-depth research to achieve the above-mentioned problems, and as a result, found that in a laminated film including a B layer (hereinafter sometimes referred to as a "forming layer") and an A layer (hereinafter sometimes referred to as a "bonding layer"), by making the laminated film show characteristics of a stress-strain curve close to that of a metal plate, and making the bonding layer show a lower melting point than the forming layer, the adhesion between the laminated film and the metal is ensured and excellent formability is shown. In addition, the inventors of the present invention have further repeatedly studied and improved, and thus completed the invention represented by the following technical solution.

[0013] [1] A coating-substitute film, which is a laminated film of at least two layers including a layer A and a layer B,

[0014] The aforementioned A layer is a layer containing a crystalline polyester as a main constituent component,

[0015] The B layer is a layer containing a crystalline polyester as a main constituent component, the plane orientation coefficient of the B layer is 0.165 or more and 0.180 or less, the melting point TmB of the B layer is higher than the melting point TmA of the A layer, and the melting point difference TmB-TmA is 25° C. or more and 35° C. or less,

[0016] The stress F20 value at 20% elongation in a tensile test at 100°C is 60 MPa or more and 110 MPa or less in either the flow direction or the width direction of the laminated film.

[0017] In both the flow direction and the width direction of the laminated film, the residual rate of the internal stress represented by the following formula 1 in a tensile test at 100° C. is 25% or less.

[0018] Formula 1: Residual rate of internal stress (%) = |1-(Ub / Ua)| × 100

[0019] Here, the tensile test is performed by the following method: using a sample with a test piece width of 15 mm, the sample is stretched to 20% under the conditions of a distance between clamps of 50 mm and a stretching speed of 1000 mm / min. After the elongation of 20%, the distance between clamps is restored to 50 mm at a speed of 2000 mm / min.

[0020] The above-mentioned Ua refers to the elastic strain energy from the starting point 0 to the yield point in the stress-strain curve obtained by the above-mentioned tensile test, and the above-mentioned Ub refers to the elastic strain energy from the elongation of 20% to the recovery to the distance between the clamps in the stress-strain curve obtained by the above-mentioned tensile test.

[0021] [2] The coating alternative film according to [1], wherein the plane orientation coefficient of the A layer is smaller than the plane orientation coefficient of the B layer by 0.03 or more.

[0022] [3] The coating alternative film according to [1] or [2], wherein the sum of the shrinkage rate in the flow direction and the shrinkage rate in the width direction of the laminated film is 1.0% or more and 5.0% or less.

[0023] [4] The coating alternative film according to any one of [1] to [3], wherein the peel strength of the surface of the layer A of the laminated film and the metal substrate laminated at 230° C. is 10 N / 20 mm or more.

[0024] [5] A coating replacement film according to any one of [1] to [4], wherein an easy-adhesion layer and a functional layer are sequentially laminated on the surface of the B layer side of the aforementioned laminated film, the easy-adhesion layer having at least one functional group selected from the group consisting of an epoxy group, an oxazoline group, a silanol group and an isocyanate group, and the functional layer is at least one selected from the group consisting of a surface protection layer and a coloring layer.

[0025] [6] The coating alternative film according to [5], wherein the colored layer contains 0.5% by mass or more and less than 40% by mass of the colorant based on 100% by mass of the resin composition constituting the colored layer.

[0026] [7] The coating-substitute film according to [5] or [6], wherein the surface protective layer contains at least one selected from the group consisting of thermosetting resins and photocurable resins as a main constituent.

[0027] [8] The coating alternative film according to any one of [5] to [7], wherein the thickness of the easy-adhesion layer is 10 nm to 200 nm.

[0028] [9] A coating alternative film according to any one of [1] to [8], wherein an easy-adhesion layer, a coloring layer and a surface protection layer are sequentially stacked on the surface of the B layer side of the aforementioned laminated film, and the easy-adhesion layer has at least one functional group selected from the group consisting of an epoxy group, an oxazoline group, a silanol group and an isocyanate group.

[0029]

[10] The coating alternative film according to [9], wherein the colored layer contains 0.5% by mass or more and less than 40% by mass of a colorant based on 100% by mass of a resin composition constituting the colored layer.

[0030]

[11] The coating-substitute film according to [9] or

[10] , wherein the surface protective layer contains at least one selected from the group consisting of thermosetting resins and photocurable resins as a main constituent component.

[0031]

[12] The coating alternative film according to any one of [9] to

[11] , wherein the thickness of the easy-adhesion layer is 10 nm to 200 nm.

[0032]

[13] A film-coated metal laminate, wherein a metal plate is laminated on the paint-substitute film according to any one of [1] to

[12] .

[0033]

[14] A metal component obtained by press-molding the film-coated metal laminate described in

[13] .

[0034]

[15] A vehicle exterior part using the film-coated metal laminate described in

[13] .

[0035]

[16] A method for producing a thin film-coated metal laminate, characterized in that it is a method for producing a thin film-coated metal laminate using the coating alternative film described in any one of [1] to

[12] , wherein a metal plate is heated to a temperature T that is greater than the melting point TmA of the aforementioned layer A of the aforementioned coating alternative film and less than the melting point TmB of the aforementioned layer B, so that the side surface of the layer A of the aforementioned coating alternative film is hot-pressed to the metal plate.

[0036] The present invention can also be described as having the following structure

[21] .

[0037]

[21] A coating replacement film comprising a laminated film, wherein the laminated film comprises a layer A and a layer B,

[0038] The layer A comprises a first crystalline polyester as a main constituent component,

[0039] The layer B comprises a second crystalline polyester as a main constituent component,

[0040] The plane orientation coefficient of the B layer is 0.165 or more and 0.180 or less,

[0041] The melting point of the layer B is higher than the melting point of the layer A, and the difference between the melting point of the layer B and the melting point of the layer A is 25° C. or more and 35° C. or less,

[0042] When the laminated film is subjected to a tensile test, the residual index rate of the internal stress in the flow direction and the width direction of the laminated film is 25% or less.

[0043] The above residual index rate is expressed by |1-(Ub / Ua)|×100,

[0044] The tensile test was conducted by the following method: a 15 mm wide test piece was clamped by a pair of clamps with a distance between the clamps of 50 mm, the distance between the clamps was widened at a tensile speed of 1000 mm / min at 100°C until a strain of 20% was generated, and then the distance between the clamps was restored to 50 mm at a speed of 2000 mm / min at 100°C.

[0045] The above-mentioned Ua is a value obtained by calculating the stress-strain curve obtained by the above-mentioned tensile test from the 0% strain integral value to the yield strain.

[0046] The above-mentioned Ub is a value obtained by tracking the above-mentioned stress-strain curve from the point where the 20% strain integrated value stress shows a strain of 0 MPa.

[0047] The present invention preferably also includes the following structure

[22] and thereafter.

[0048]

[22] The coating alternative film according to

[21] , wherein the 20% strain tensile stress in the tensile test in both the flow direction and the width direction of the laminated film is 60 MPa or more and 110 MPa or less.

[0049]

[23] The coating replacement film according to

[21] or

[22] , wherein the plane orientation coefficient of the aforementioned B layer is greater than the plane orientation coefficient of the aforementioned A layer, and the difference between the plane orientation coefficient of the aforementioned B layer and the plane orientation coefficient of the aforementioned A layer is greater than 0.03.

[0050]

[24] A coating replacement film according to any one of

[21] to

[23] , wherein when the laminated film is heat treated at 150°C for 15 minutes, the sum of the heat shrinkage in the flow direction and the heat shrinkage in the width direction is greater than or equal to 1.0% and less than or equal to 5.0%.

[0051]

[25] A coating alternative film according to any one of

[21] to

[24] , wherein after the coating alternative film is laminated on the metal substrate at 230°C in a manner such that the A layer contacts the metal substrate, the coating alternative film has a peel strength of 10N / 20mm or more when it is peeled off from the metal substrate at a tensile speed of 50mm / min and 180°.

[0052]

[26] The coating alternative film according to any one of

[21] to

[25] , further comprising an easy-adhesion layer and a functional layer, wherein the easy-adhesion layer is provided on the surface of the layer B of the laminated film,

[0053] The aforementioned A layer, the aforementioned B layer, the aforementioned easy-adhesion layer and the aforementioned functional layer are arranged in sequence,

[0054] The functional layer includes at least one of a coloring layer and a surface protection layer.

[0055]

[27] The coating alternative film according to

[26] , wherein the easy-adhesion layer comprises a resin having at least one functional group selected from the group consisting of an epoxy group, an oxazoline group, a silanol group, and an isocyanate group.

[0056]

[28] The coating alternative film according to

[26] or

[27] , wherein the functional layer comprises the coloring layer and the surface protection layer,

[0057] The A layer, the B layer, the easy-adhesion layer, the colored layer, and the surface protective layer are arranged in this order.

[0058]

[29] The coating alternative film according to any one of

[26] to

[28] , wherein the functional layer includes the colored layer.

[0059] The colored layer contains a colorant in an amount of 0.5% by mass or more and less than 40% by mass based on 100% by mass of the resin composition constituting the colored layer.

[0060]

[30] The coating alternative film according to any one of

[26] to

[29] , wherein the functional layer includes the surface protective layer.

[0061] The surface protection layer includes at least one of a thermosetting resin and a photocurable resin.

[0062]

[31] The coating alternative film according to any one of

[26] to

[30] , wherein the thickness of the easy-adhesion layer is 10 nm to 200 nm.

[0063]

[32] A laminate comprising:

[0064] Metal sheets; and

[0065] The paint-substitute film according to any one of

[21] to

[31] laminated on the metal plate.

[0066]

[33] A metal component obtained by press-molding the laminate described in

[32] .

[0067]

[34] A vehicle exterior component comprising the laminate described in

[32] .

[0068]

[35] A method for producing a laminate, comprising:

[0069] A step of heating the metal plate to a temperature not less than the melting point of the layer A and not more than the melting point of the layer B in the paint-substitute film according to any one of

[21] to

[31] ; and

[0070] A step of pressure-bonding the metal plate heated to the temperature and the coating-substitute film so that the metal plate contacts the A layer.

[0071]

[36] The coating alternative film according to any one of

[21] to

[31] , wherein the sum of the heat shrinkage rate in the flow direction and the heat shrinkage rate in the width direction is 4.8% or less.

[0072]

[37] The coating alternative film according to any one of

[21] to

[31] , wherein the sum of the heat shrinkage rate in the flow direction and the heat shrinkage rate in the width direction is 4.5% or less.

[0073]

[38] The coating alternative film according to any one of

[21] to

[31] , wherein the sum of the heat shrinkage rate in the flow direction and the heat shrinkage rate in the width direction is 4.2% or less.

[0074]

[39] The coating alternative film according to any one of

[21] to

[31] , wherein the sum of the heat shrinkage rate in the flow direction and the heat shrinkage rate in the width direction is 4.0% or less.

[0075] Effects of the Invention

[0076] According to the coating alternative film of the present invention, it is possible to provide a metal component that has excellent adhesion and excellent formability to various metals, has no appearance defects caused by film breakage or peeling after press molding, and has excellent appearance design. The coating alternative film of the present invention can provide the value of omitting the coating process in the manufacture of metal components. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 This is a diagram showing the concept of a calculation formula for the residual rate of internal stress. DETAILED DESCRIPTION

[0078] The coating replacement film according to the embodiment of the present invention comprises a laminated film, wherein the laminated film comprises an A layer and a B layer.

[0079] The layer A comprises a first crystalline polyester as a main constituent component,

[0080] The layer B comprises a second crystalline polyester as a main constituent component,

[0081] The plane orientation coefficient of the B layer is 0.165 or more and 0.180 or less,

[0082] The melting point of the layer B is higher than the melting point of the layer A, and the difference between the melting point of the layer B and the melting point of the layer A is 25° C. or more and 35° C. or less,

[0083] When the laminated film is subjected to a tensile test, the residual index rate of the internal stress in the flow direction and the width direction of the laminated film is 25% or less.

[0084] The above residual index rate is expressed by |1-(Ub / Ua)|×100,

[0085] The tensile test was conducted by the following method: a 15 mm wide test piece was clamped by a pair of clamps with a distance between the clamps of 50 mm, the distance between the clamps was widened at a tensile speed of 1000 mm / min at 100°C until a strain of 20% was generated, and then the distance between the clamps was restored to 50 mm at a speed of 2000 mm / min at 100°C.

[0086] The above-mentioned Ua is a value obtained by integrating the stress-strain curve obtained by the above-mentioned tensile test from 0% strain to yield strain.

[0087] The above-mentioned Ub is a value obtained by integrating the above-mentioned stress-strain curve from 20% strain to the strain at which the stress shows 0 MPa.

[0088] Since the difference between the melting points of layer B and layer A in the coating alternative film of this embodiment is greater than 25°C, the fluidity of layer A when the coating alternative film of this embodiment is pressed onto a metal plate can be improved, thereby improving the peel strength (specifically, the peel strength when the coating alternative film is peeled off from the metal plate).

[0089] Moreover, since the residual index rate of internal stress is less than 25% (specifically, when performing a tensile test on the laminated film, the residual index rate of internal stress is less than 25% in both the flow direction and the width direction of the laminated film), it is possible to reduce or prevent the peeling of the coating substitute film from the metal plate that may occur during or after press forming. Specifically, it is possible to reduce or prevent the peeling of the coating substitute film that may occur during press forming of the laminated metal plate (such as a steel plate, an aluminum alloy plate, etc.) that includes the metal plate and the coating substitute film laminated on the metal plate (hereinafter sometimes referred to as a "film-coated metal laminate", "laminated body") after the coating substitute film of the present embodiment is hot-pressed to the metal plate (such as a steel plate, an aluminum alloy plate, etc.), and the peeling of the coating substitute film that may occur after press forming. This is described below.

[0090] The residual index rate of internal stress is expressed by the following formula.

[0091] Residual index rate of internal stress = |1-(Ub / Ua)|×100

[0092] =|(Ua-Ub) / Ua|×100

[0093] Ua and Ub of this formula can be obtained from the stress-strain curve obtained by a tensile test (specifically, a tensile test performed according to the following steps: a 15 mm wide test piece is clamped with a pair of clamps at a distance of 50 mm between the clamps, the distance between the clamps is widened at a tensile speed of 1000 mm / min at 100°C until a strain of 20% occurs, and the distance between the clamps is restored to 50 mm at a speed of 2000 mm / min at 100°C). Here, the stress-strain curve is a graph in which stress is plotted on the vertical axis and strain is plotted on the horizontal axis (see Figure 1 ).

[0094] like Figure 1 As shown in FIG. 1 , Ua is a value obtained by integrating the stress-strain curve from 0% strain to the yield strain, i.e., the strain showing the yield point. If the period from the start of stretching to the occurrence of the yield strain is regarded as elastic deformation, Ua can be regarded as the elastic strain energy accumulated in the laminated film by stretching.

[0095] On the other hand, Ub is a value obtained by integrating from 20% strain to the strain at which the stress shows 0 MPa (hereinafter sometimes referred to as "recovery strain" or "recovery strain amount"). Ub is the energy released when the distance between the clamps at which the 20% strain is applied is restored to the distance between the clamps at the start of stretching of 50 mm, that is, when the deformation of the laminated film (specifically, the deformation applied to the laminated film by stretching) is restored, and therefore, it can be said to be elastic strain energy.

[0096] Assuming that the balance between Ua and Ub deteriorates excessively, the elastic strain energy of the laminated film (specifically, the elastic strain energy accumulated in the laminated film due to press molding) will not be effectively released through the rebound that occurs when the laminated metal plates are press molded. In other words, the elastic strain energy will not be effectively reduced, and therefore, excessive internal stress will remain in the laminated film.

[0097] In contrast, according to the present embodiment, since the value calculated by |(Ua-Ub) / Ua|×100 (i.e., the residual index rate of internal stress) is 25% or less, the elastic strain energy of the laminated film can be effectively released by the springback that occurs when the laminated metal plate is press-formed, and thus, excessive internal stress can be avoided from remaining in the laminated film. As a result, the peeling of the coating replacement film that may occur during or after press-forming can be reduced or prevented.

[0098] It should be noted that, by hot pressing the coating replacement film of this embodiment to a metal plate for a vehicle (such as a steel plate, an aluminum alloy plate, etc.) to obtain a laminated metal plate, and then press-forming the laminated metal plate into a vehicle exterior part, the peeling of the coating replacement film can be further reduced or prevented. It is believed that this is because: when the laminated metal plate is press-formed, when the coating replacement film is locally elongated, its elongation is usually at most about 20% in the vehicle exterior part. It should be noted that the vehicle is preferably a car, and more preferably a four-wheeled car.

[0099] The residual index rate of internal stress can be controlled by, for example, the plane orientation coefficient of the B layer, the ratio of the thickness of the B layer to the thickness of the laminated film, etc. There is a tendency that the higher the plane orientation coefficient of the B layer, the smaller the residual index rate of internal stress. There is a tendency that the larger the ratio (specifically, the ratio of the thickness of the B layer to the thickness of the laminated film), the smaller the residual index rate of internal stress.

[0100] Furthermore, since the plane orientation coefficient of the B layer is 0.165 or more, the generation of wrinkles and bubbles that may occur when the coating alternative film of this embodiment is thermally pressed onto a metal plate can be reduced. In other words, the appearance design of the laminated metal plate can be improved.

[0101] Therefore, according to the coating alternative film of this embodiment, the generation of wrinkles or bubbles during hot pressing can be reduced, and the peeling from the metal plate that may occur during or after press forming can be reduced or prevented. That is, the coating alternative film of this embodiment can show excellent adhesion to the metal plate and can also show an excellent appearance design when hot pressing is performed on the metal plate.

[0102] Hereinafter, the embodiments of the present invention will be described in more detail. It should be noted that the flow direction is sometimes referred to as the Machine Direction or the MD direction. The width direction is sometimes referred to as the Transverse Direction or the TD direction. The stress at 20% elongation is sometimes referred to as the F20 value or the 20% strain tensile stress. Strain is sometimes referred to as the strain amount.

[0103] The coating alternative film of the present embodiment includes a laminated film, and the laminated film includes an A layer and a B layer. The A layer may have a function of mainly showing adhesion to the metal plate. That is, the A layer may function as an adhesive layer. On the other hand, the B layer may have a function of mainly following the deformation of the metal plate during press forming. That is, the B layer may function as a forming layer. It should be noted that in the coating alternative film of the present embodiment, on the basis of the A layer and the B layer, other layers may be further included. It should be noted that the other layers are preferably based on polyester, preferably based on crystalline polyester. It should be noted that the crystalline polyester will be described in detail later.

[0104] Layer A and layer B are mainly composed of polyester. Here, "mainly" means that based on the mass of the entire film, polyester is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and further preferably 90% by mass or more.

[0105] The polyester constituting the A layer is preferably a crystalline polyester. The crystalline polyester mentioned here means: using a DSC-60 differential scanning calorimeter, 10 mg of the polyester composition cut from the A layer is heated to 290°C at a rate of 20°C / min, isothermally maintained for 3 minutes, and then quenched at a rate of 200°C / min. When the temperature is again raised to 290°C at a rate of 10°C / min, a baseline shift corresponding to the glass transition temperature is observed, and an endothermic peak of 0.05 J / g or more associated with crystalline melting is observed on the side closer to the high temperature than the baseline shift. The polyester constituting the A layer can be a homopolymer polyester or a copolyester. Preferably, a copolyester having a eutectic point of 160°C to 250°C is used, and more preferably a copolyester having a melting point of 180°C to 250°C is used. The copolyester preferably has ethylene terephthalate units as the main body. Here, "mainly composed of" means that in the copolyester, the ethylene terephthalate unit is preferably 60 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more.

[0106] The copolymer component of the copolyester may be an acid component or an alcohol component. As the acid component, aromatic dicarboxylic acids other than the main acid components such as isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalene dicarboxylic acid, etc.; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, etc., etc., as the alcohol component, ethylene glycol, trimethylene glycol, tetramethylene glycol, etc., polyoxyalkylene glycols such as diethylene glycol, etc., etc., may be listed. In addition, aliphatic diols such as 1,6-hexanediol, alicyclic diols such as 1,4-cyclohexanedimethanol, etc., may be listed. They may be used alone or in combination of two or more. Among these, isophthalic acid and sebacic acid are preferred, and isophthalic acid is particularly preferred.

[0107] The content of the crystalline polyester in the layer A is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and further preferably 90% by mass or more, based on 100% by mass of the layer A.

[0108] The polyester constituting the B layer is preferably a crystalline polyester. The crystalline polyester mentioned here means that when 10 mg of the polyester composition cut from the B layer is heated to 290°C at a rate of 20°C / min using a DSC-60 differential scanning calorimeter, the temperature is kept isothermally for 3 minutes, and then quenched at a rate of 200°C / min and heated to 290°C again at a rate of 10°C / min, a baseline shift corresponding to the glass transition temperature is observed, and an endothermic peak of 0.05 J / g or more accompanying crystalline melting is observed on the higher temperature side than the baseline shift.

[0109] The polyester constituting layer B may be a homopolymer polyester or a copolymer polyester. A polyester having a melting point of more than 250° C. and less than 260° C. is preferred, and a homopolymer polyethylene terephthalate is particularly preferred. It should be noted that the homopolymer polyethylene terephthalate herein does not exclude the case where it contains the inevitably contained diethylene glycol component.

[0110] The content of the crystalline polyester in the layer B is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and further preferably 90% by mass or more, based on 100% by mass of the layer B.

[0111] In order to fully ensure melt wetting with the metal when laminating by heat fusion and maintain good molding during cold press molding, the coating alternative film of the present invention preferably has a melting point TmB of the B layer higher than the melting point TmA of the A layer, and the melting point difference TmB-TmA is preferably 25°C or more and 35°C or less. By making the above melting point difference 25°C or more, sufficient melt wetting with the metal can be ensured even when the temperature during lamination of the coating alternative film and the metal plate is low. On the other hand, by making the above melting point difference 35°C or less, the refractive index of the A layer and the B layer can be controlled within a specified range, and the influence caused by shear heat can be suppressed during cold press molding to achieve uniform molding, which helps to improve the adhesion and molding properties with the metal plate.

[0112] The intrinsic viscosity (i.e. IV) of the polyester used in the A layer and the B layer is preferably 0.60 or more and less than 0.95. When the intrinsic viscosity is above the lower limit, the film-making operability of the film is good, and the generation of thermal degradation products originating from low molecular weight substances can be suppressed. In addition, it is possible to prevent the internal stress generated during the cold press forming of the metal from being excessively retained in the laminated film, and it is possible to show excellent adhesion and excellent formability for various metals, so it is preferred. On the other hand, when it is below the upper limit, the adhesion becomes good, and the lamination processability with the metal plate is improved.

[0113] The surface orientation coefficient of the B layer in the present invention is preferably 0.165 or more, more preferably 0.166 or more, further preferably 0.167 or more, further preferably 0.168 or more, and further preferably 0.170 or more. By making the surface orientation coefficient of the B layer 0.165 or more, it is possible to prevent the internal stress generated during the cold press forming of the metal from being excessively retained in the laminated film. The surface orientation coefficient of the B layer is preferably 0.180 or less, more preferably 0.178 or less. Preferably, the surface orientation coefficient of the A layer is less than the surface orientation coefficient of the B layer, and the difference between the surface orientation coefficient of the B layer and the surface orientation coefficient of the A layer is preferably 0.030 or more.

[0114] Regarding the coating alternative film in the present invention, in any direction of the flow direction and the width direction of the laminated film including the A layer and the B layer, the stress F20 value at 20% elongation in the tensile test under 100°C is preferably 60MPa or more. More preferably, it is 65MPa or more, and further preferably 70MPa or more. By setting it to 60MPa or more, the stress of the coating alternative film can be maintained under the heating applied by the shear heat generated during the cold press forming of the metal, and uniform formability can be ensured. The upper limit of the F20 value is not particularly limited, but is preferably 110MPa or less, and more preferably 105MPa or less.

[0115] Regarding the coating alternative film in the present invention, in any direction of the flow direction and the width direction of the laminated film including the A layer and the B layer, the residual rate of the internal stress represented by the following formula 1 in a tensile test under 100°C (i.e., the residual index rate) is preferably 25% or less.

[0116] (Formula 1): Residual rate of internal stress (%) = |1-(Ub / Ua)| × 100

[0117] Here, the above-mentioned tensile test is carried out by the following method: using a sample with a test piece width of 15 mm, stretching it to an elongation of 20% under the conditions of a clamp distance of 50 mm and a stretching speed of 1000 mm / min, and after elongation of 20%, the clamp distance is restored to 50 mm at a speed of 2000 mm / min. The above-mentioned Ua refers to the elastic strain energy from the starting point 0 to the yield point in the stress-strain curve obtained by the above-mentioned tensile test, and the above-mentioned Ub refers to the elastic strain energy from the elongation of 20% to the recovery to the clamp distance in the stress-strain curve obtained by the above-mentioned tensile test.

[0118] That is, when a tensile test is conducted on a laminated film (specifically, a tensile test is conducted by the following method: a 15 mm wide test piece cut from the laminated film is clamped using a pair of clamps with an inter-clamp distance of 50 mm, the inter-clamp distance is widened at a tensile speed of 1000 mm / min at 100°C until a 20% strain is generated, and the inter-clamp distance is then restored to 50 mm at a speed of 2000 mm / min at 100°C), the residual index rate of the internal stress represented by Formula 1 is less than 25% in both the flow direction and the width direction of the laminated film.

[0119] Ua is a value obtained by integrating the stress-strain curve obtained by the tensile test from 0% strain to the yield strain (i.e., the strain showing the yield point). In other words, it is the area of ​​the region surrounded by the stress-strain curve and the portion from 0% strain to the yield strain on the horizontal axis.

[0120] Ub is a value obtained by integrating the stress-strain curve from 20% strain to the strain where the stress shows 0 MPa (i.e., "recovery strain"). In other words, it is the area of ​​the region surrounded by the stress-strain curve and the portion from 20% strain to the recovery strain on the horizontal axis.

[0121] Note that the above-mentioned tensile test for obtaining Ua and Ub is a 100° C. tensile test in view of the heat generated by shearing when the laminated metal sheet is press-formed.

[0122] The residual index rate of the internal stress, that is, the residual rate, in both the flow direction and the width direction of the laminated film may be 23% or less, 20% or less, or 17% or less.

[0123] It should be noted that, in the flow direction of the laminated film, Ub may be greater than Ua or less than Ua.

[0124] In the width direction of the laminated film, Ub may be larger than Ua or smaller than Ua.

[0125] In both the flow direction and the width direction of the laminated film, Ub may be larger than Ua or smaller than Ua.

[0126] When a metal plate laminated with a coating substitute film is subjected to cold pressing, a load is applied until a specified deformation amount is reached. When the load is subsequently removed, a rebound phenomenon occurs that attempts to restore the original state along the slope of the elastic deformation region in the stress-strain curve. At this time, if the residual rate of the internal stress of the coating substitute film is high, the film sometimes cannot follow the rebound, and the film is damaged or peeled off. It can be inferred that by making the residual rate of the above-mentioned internal stress of the coating substitute film less than 25%, it is possible to prevent the internal stress generated during cold pressing from being excessively retained in the laminated film, thereby being able to exhibit excellent adhesion and excellent formability for various metals. The residual rate of the above-mentioned internal stress is set within the above-mentioned range by controlling the characteristic viscosity and the plane orientation coefficient of the A layer and the B layer to a specified range.

[0127] Regarding the coating replacement film of the present invention, the sum of the heat shrinkage in the flow direction and the heat shrinkage in the width direction of the laminated film comprising layer A and layer B after heat treatment at 150°C for 15 minutes is preferably 5.0% or less. If it exceeds 5.0%, the adhesion during heat lamination is low, and a high lamination temperature near or above the melting point is required, which is not preferred in practical use. In addition, it is not preferred from the perspective of dimensional stability during thermoforming. The sum of the heat shrinkage is preferably 4.8% or less. The sum of the heat shrinkage can be, for example, 4.5% or less, 4.2% or less, or 4.0% or less. As methods for achieving the above-mentioned heat shrinkage, methods such as appropriately setting stretching conditions and heat fixing treatment conditions can be listed. The sum of the heat shrinkage in the flow direction and the heat shrinkage in the width direction can be 1.0% or more, 2.0% or more, or 3.0% or more.

[0128] In addition, the heat shrinkage rate can be calculated|required by the following formula.

[0129] Thermal shrinkage (%) = {(L0-L) / L0} × 100

[0130] Here, L is the distance between the marking lines after heat treatment (specifically, heat treatment at 150° C. for 15 minutes), and L0 is the distance between the marking lines before heat treatment (specifically, heat treatment at 150° C. for 15 minutes).

[0131] The coating alternative film of the present invention preferably has a peel strength of 10.0N / 20mm or more when the A layer is laminated with the metal substrate at 230°C. That is, after the aforementioned coating alternative film is laminated to the metal substrate at 230°C in a manner that the A layer is in contact with the metal substrate, the peel strength when the coating alternative film is peeled off from the metal substrate at a tensile speed of 50mm / min and 180° is preferably 10.0N / 20mm or more. By being 10.0N / 20mm or more, the adhesion and formability during cold press molding can be maintained. The peel strength is more preferably 13.0N / 20mm or more, and more preferably 15.0N / 20mm or more. The upper limit is not particularly limited, and is preferably 35.0N / 20mm or less, more preferably 30.0N / 20mm or less, and more preferably 25.0N / 20mm or less.

[0132] The thickness of the laminated film of the present invention can be appropriately changed as needed, and is suitable for the range of 15 to 200 μm in terms of overall thickness, preferably 20 to 150 μm, and particularly preferably 30 to 100 μm. By making the thickness 15 μm or more, the operability in the film-making, functional layer lamination, and lamination process is good. On the other hand, by being 200 μm or less, the load during the molding process can be suppressed from becoming too large.

[0133] The thickness of the A layer is preferably 5 μm or more, more preferably 8 μm or more. By making the A layer 5 μm or more, the melt wetting is fully ensured when laminating with the steel plate, and the adhesion between the film and the metal plate is easily exhibited. Furthermore, from the viewpoint of improving the adhesion between the film and the metal plate and maintaining a good appearance, the thickness ratio of the A layer to the B layer (XB / XA: wherein XA is the total thickness of the A layer and XB is the total thickness of the B layer) is preferably 1.5 or more, more preferably 2.0 or more.

[0134] The ratio of the thickness of the B layer to the thickness of the laminated film, i.e., the thickness of the B layer / the thickness of the laminated film, is preferably 0.50 or more, more preferably 0.60 or more, further preferably 0.65 or more, further preferably 0.70 or more. On the other hand, the ratio is preferably 0.95 or less, more preferably 0.90 or less.

[0135] Without prejudice to the purpose of the present invention, other additives such as coloring pigments (i.e., colorants), fluorescent whitening agents, antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents, etc. can be added to the above-mentioned A layer and B layer as needed. In the case where the laminated film is used as a shielding layer for the metal, it is preferred to add a coloring pigment, which can be any of an inorganic system and an organic system, preferably an inorganic system. As inorganic pigments, preferred examples include aluminum oxide, titanium dioxide, calcium carbonate, barium sulfate, etc., among which titanium dioxide is more preferred. The content of the coloring pigment is preferably more than 2% by mass and less than 50% by mass based on the mass of the B layer, and the content is more preferably 5 to 40% by mass, and further preferably in the range of 10 to 35% by mass. In particular, a fluorescent whitening agent can be used to improve the whiteness. In addition, in order to improve the operability in the film-making process and the molding process, inactive particles can be added. As the inactive particles contained, there is no particular limitation as long as they can stably exist in the polymer, and particles known per se can be used, preferably, for example, polymers or copolymers of each monomer selected from polystyrene, polymethyl acrylate, polyethyl acrylate, polymethyl methacrylate, polyethyl methacrylate and divinylbenzene, polytetrafluoroethylene, polyacrylonitrile, benzoguanamine, organic silicon and other organic substances; any of inorganic substances such as silica, kaolin, talc, graphite, etc. The preferred particle size of these inactive particles is 0.1 to 10 μm. The B layer may contain the inactive particles, the A layer may contain the inactive particles, or both may contain the inactive particles. The content of the inactive particles in the laminated film is preferably in the range of 0.002 to 0.5 mass % in 100 mass % of the laminated film. In the case where the B layer contains inactive particles, the content of the inactive particles is preferably in the range of 0.002 to 0.5 mass % in 100 mass % of the B layer. On the other hand, when the A layer contains inactive particles, the content of the inactive particles is preferably in the range of 0.002 to 0.5% by mass based on 100% by mass of the A layer.

[0136] In addition, when the laminated film contains a coloring pigment, that is, a colorant, the A layer may contain the colorant, the B layer may contain the colorant, or both the A layer and the B layer may contain the colorant.

[0137] Of course, the laminated film may not contain a colorant, that is, both the A layer and the B layer may not contain a colorant.

[0138] The method for producing the A layer and the B layer in the present invention is not particularly limited, and any known film-making method can be applied. As an example, in the case of producing a biaxially oriented laminated film, an unstretched laminated sheet is first produced, and then stretched in two directions. Representative examples are shown below.

[0139] For example, a polyester composition in which inactive particles are added to the polyester for layer A is prepared and fully dried, and then melted in an extruder at a temperature of melting point to (melting point + 50) ° C. It should be noted that the melting point here is the melting point of the polyester used. At the same time, a polyester composition in which inactive particles are added to the crystalline polyester for layer B is prepared and fully dried, and then supplied to another extruder to melt at a temperature of melting point to (melting point + 50) ° C. Next, a laminated unstretched laminated sheet is manufactured by a method of laminating two molten resins inside a mold, such as a simultaneous lamination extrusion method using a multi-manifold mold. According to the simultaneous lamination extrusion method, the melt of the resin forming one layer and the melt of the resin forming another layer are laminated inside the mold, and are formed into a sheet from the mold while maintaining the laminated shape.

[0140] Next, the unstretched laminate can be manufactured by a method of sequentially or simultaneously biaxially stretching and heat fixing the unstretched laminate. In the case of film formation by sequential biaxial stretching, the unstretched laminate is heated by roller heating, infrared heating, etc., first stretched in the flow direction, and then stretched transversely by a tenter. At this time, the lower limit of the stretching temperature in the flow direction is preferably 70°C, and more preferably 80°C. If it is lower than 70°C, not only is it easy to break, but the stretching at low temperature causes the orientation in the flow direction to become stronger. Therefore, the shrinkage stress during the heat fixation treatment becomes larger, and thus the strain of the molecular orientation in the width direction becomes larger, resulting in the possibility of reduced processability during molding. The upper limit of the stretching temperature in the flow direction is preferably 110°C, and more preferably 100°C. If it exceeds 110°C, the orientation is reduced, and therefore, the processability during molding may be reduced.

[0141] The lower limit of the stretch ratio in the flow direction is preferably 3 times, particularly preferably 3.5 times. If it is less than the above lower limit, the orientation is reduced, and therefore, in addition to the reduced processability during molding, the film roll is sometimes relaxed due to uneven thickness. The upper limit of the stretch ratio in the flow direction is preferably 5.0 times, more preferably 4.5 times, and particularly preferably 4.0 times. If it exceeds the above upper limit, the effect of improving mechanical strength and uneven thickness is sometimes saturated. The stretching in the flow direction can, for example, be performed in a roller stretching machine by heating the unstretched film using a heating roller or infrared radiation heat, and the speed difference between the rollers is used for stretching.

[0142] The lower limit of the stretching temperature in the width direction is preferably 90°C. If it is lower than the lower limit, breakage may occur easily. The upper limit of the TD stretching temperature is preferably 130°C. If it exceeds the upper limit, orientation decreases, so the processability during molding may decrease.

[0143] The lower limit of the stretch ratio in the width direction is preferably 3.0 times, and more preferably 3.5 times. If it is lower than the above lower limit, the orientation degree in the width direction becomes small, so in addition to the reduction of processability during molding, the film roll sometimes relaxes due to uneven thickness. The upper limit of the stretch ratio in the width direction is preferably 5.0 times, and more preferably 4.5 times. If it exceeds the above upper limit, the effect of improving processability during molding and uneven thickness may be saturated.

[0144] After the above-mentioned biaxial stretching, a heat fixation treatment is preferably performed. In order to adjust the film quality, the heat fixation temperature is preferably selected in the range of 150 to 230°C according to the melting point of the polyester. At this time, if it is too low, the adhesion to the metal deteriorates, and if it is too high, the surface orientation coefficient decreases, and thus, the function of suppressing elastic strain energy cannot be exhibited, resulting in deterioration of adhesion to the metal and formability. In view of this, the heat fixation temperature is preferably above 205°C, more preferably above 210°C, and further preferably above 215°C.

[0145] It is preferred to perform heat relaxation treatment together with heat fixation treatment or to perform heat relaxation treatment separately from heat fixation treatment. In the heat relaxation treatment, it is preferred to relax in at least one of the flow direction (i.e., MD direction) and the width direction (i.e., TD direction). Among them, it is preferred to relax in the width direction. When relaxation is performed in the width direction, the relaxation rate in the width direction is preferably 3% or more, more preferably 4% or more. If it is 3% or more, the heat shrinkage rate can be effectively reduced. On the other hand, the relaxation rate in the width direction is preferably 8% or less, more preferably 7% or less.

[0146] One of the preferred embodiments of the present invention is a coating alternative film, wherein an easy bonding layer is stacked on the B layer side surface of the laminated film of at least two layers including an A layer and a B layer. The above-mentioned easy bonding layer has a function of making the laminated film and the surface protection layer and the coloring layer described later have good adhesion. The above-mentioned easy bonding layer preferably includes a resin having at least one functional group selected from the group consisting of an epoxy group, an oxazoline group, a silanol group and an isocyanate group. Among these, from the viewpoint of being able to obtain excellent adhesion and distinctness of image with the above-mentioned B layer (with reference to patent document 2, i.e., Japanese Patent Publication No. 2020-192787), it is preferably containing an epoxy group or an oxazoline group. From the viewpoint of adhesion, the thickness of the above-mentioned easy bonding layer is preferably more than 10nm, more preferably more than 15nm, further preferably 20nm, particularly preferably more than 40nm. On the other hand, from the viewpoint of reducing uneven thickness during coating and adhesiveness, the upper limit of the thickness is preferably 200 nm or less, more preferably 180 nm, further preferably 150 nm, and particularly preferably 120 nm or less.

[0147] As described above, the above-mentioned easy-adhesive layer preferably contains at least one functional group selected from the group consisting of epoxy, oxazoline, silanol, and isocyanate. If the resin forming the easy-adhesive layer itself has excellent adhesion to the laminated film and the functional layer, then the material known to itself can be used. In order to adjust the adhesive force, the operation of copolymerizing each resin or blending different resins to improve the adhesive force can be suitably utilized. For example, any material in polyurethane resin, vinyl chloride / vinyl acetate copolymer resin, vinyl chloride / vinyl acetate / acrylic copolymer resin, chlorinated polypropylene resin, acrylic resin, polyester resin, polyamide resin, butyral resin, polystyrene resin, nitrocellulose resin, cellulose acetate resin, etc. can be used alone or in combination with more than two kinds. In the molding based on cold pressing in the present invention, the molding temperature preferably reaches about 150°C, so it is preferably designed to be in a state where the glass transition temperature is lower than the temperature, and acrylic resin and polyester resin can be preferably used.

[0148] The above-mentioned easy-adhesion layer may be provided by in-line coating during film formation of the laminated film, or may be provided by once rolling up the laminated film after film formation and then unwinding it again for off-line coating.

[0149] The thus obtained easy-adhesion layer contributes to improving the adhesion between the laminated film and each layer by forming bonds between functional groups, reducing interlayer interface energy, and interlayer interface mixing effects when laminating the surface protection layer and / or coloring layer described later.

[0150] One of other preferred embodiments of the present invention is a coating replacement film, wherein, on the B layer side surface of a laminated film of at least two layers including an A layer and a B layer, at least one functional layer selected from the group consisting of a surface protection layer and a coloring layer is provided via an easy-adhesion layer.

[0151] One of the other preferred embodiments of the present invention is a coating replacement film, wherein a coloring layer and a surface protection layer are sequentially laminated via an easy-adhesion layer on the B-layer side surface of a laminated film of at least two layers including an A layer and a B layer. By sequentially laminating each layer, the laminated film and the functional layer are well adhered, and an excellent appearance design can be exhibited, which is preferred.

[0152] The above-mentioned colored layer preferably contains a binder resin and at least one colorant selected from the group consisting of a pigment and a dye. From the viewpoint of designability, based on the mass of the composition used in the colored layer, it is preferably contained more than 0.5% by mass and less than 40% by mass. As a further preferred range, it is more than 2% by mass and less than 30% by mass, and as a particularly preferred range, it is more than 5% by mass and less than 25% by mass. When a binder resin is not used, the colored layer is prone to cracks due to the elongation during molding, and the result is likely to be damaged in terms of appearance. In addition, by using a pigment or a dye, it is possible to form an appearance that is excellent in appearance. The pigment or dye used is preferably selected from more than one of the group consisting of carbon black (ink), iron black, titanium white, antimony white, chrome yellow, titanium yellow, iron oxide red, cadmium red, ultramarine, cobalt blue, quinacridone red, isoindolinone yellow, phthalocyanine blue, aluminum, brass, titanium dioxide and pearlescent luster pigment. In order to color, in the scope that does not damage the effect of the present invention, it is a preferred mode to use other pigments and additives.

[0153] The method for forming the colored layer is not particularly limited, but lamination by coating is simple and therefore preferred. The adhesion between the colored layer and the layer B can be appropriately adjusted by the types of the layer B and the adhesive layer C, and the binder resin used in the colored layer.

[0154] The thickness of the coloring layer is preferably 2 μm or more, more preferably 5 μm or more, and further preferably 10 μm or more. The upper limit of the thickness is preferably 100 μm or less, more preferably 75 μm or less, further preferably 50 μm or less, further preferably 45 μm or less, and further preferably 30 μm or less. The coloring layer can be multi-layered in order to express a beautiful design when used on the exterior of a vehicle. For example, it is also preferred to form a two-layer coloring layer by providing a coloring layer containing a bright material pigment in a binder resin on a coloring layer formed of a pigment. In addition, considering the reflection characteristics from the visual recognition side, it is also preferred to form a three-layer coloring layer such that the side of the coloring layer closest to the laminated film is a colored reflection layer formed of an aluminum pigment, a colored pigment layer, and a bright material pigment layer of a transparent coating. In terms of imparting the necessary design, using the coloring layer in the form of a single layer or in the form of multiple layers does not negate the purpose of the present invention at all.

[0155] From the perspective of adaptability in the manufacturing process from the manufacture of the coating alternative film to the molding of the metal component, the resin used in the above-mentioned surface protection layer is preferably mainly formed of at least one resin selected from the group consisting of a thermosetting resin or a photocurable resin. In other words, the surface protection layer preferably has thermosetting or photocurable properties. Among them, thermosetting is preferred. The surface protection layer is required to have the functions of weather resistance, damage resistance, and transparency. As an example, an acrylic resin can be used.

[0156] The thickness of the surface protection layer is preferably 5 to 80 μm in terms of the film thickness after drying. By making the thickness of the surface protection layer above the above lower limit, the resin material is less and the economy is excellent, but the inner coloring layer, laminated film, and the protection performance against damage and chemicals after the component is formed cannot be highly maintained. On the other hand, by making the above thickness below the upper limit, it is excellent in terms of gloss and protective performance as a hard coating film, but it is not excellent in terms of economy because more resin than necessary is used. The lower limit of the thickness of the surface protection layer is preferably 10 μm, more preferably 15 μm, and on the other hand, the upper limit is preferably 60 μm, more preferably 50 μm.

[0157] The surface protection layer may be composed of a single layer or multiple layers. For example, when the same resin is applied twice in multiple layers, the degree of curing can be adjusted by making the drying conditions different, and the adhesion can be improved when a functional layer such as an antifouling layer is provided outside the surface protection layer. In addition, by forming multiple layers within the above range, a glossy surface can be produced.

[0158] The surface protection layer is preferably laminated on the easy-adhesion layer or the coloring layer by coating. The method may be a known coating method, preferably rolled into a roll in a state where thermal curing is not completed (hereinafter sometimes referred to as a "semi-cured state"). When the hard coating is dried, a primary reaction is carried out by heat, and the hard coating forms a coating film in a semi-cured state, which can be rolled up. The surface protection layer in the semi-cured state is designed in such a way that a secondary reaction is carried out thereafter, that is, the reaction is carried out at a temperature higher than the aforementioned drying temperature, so that the degree of effect of changing from semi-curing to curing due to the heat when the metal plates are laminated and the components are formed can be promoted.

[0159] As one of the preferred modes in the present invention, the coating replacement film of the present invention can further laminate the surface of the functional layer composed of the coloring layer and / or the surface protection layer as needed. Examples include antifouling layers to prevent dirt when used outdoors and lamination of protective films for improving the operability of the manufacturing process. In particular, when the surface protection layer is laminated in a semi-cured state, in order to improve the operability of the subsequent process, a laminated protective film is preferably used. The protective film can be peeled off at any time. From the perspective of damage resistance, it is preferably peeled off after undergoing hot compression lamination with a metal plate and cold press molding of a film-covered metal laminate. As the type of protective film, examples include films formed by polyethylene resins, polyester resins, copolyester resins, polypropylene resins, polyvinyl chloride resins and mixtures thereof. From the perspective of formability, polyethylene resins, polyvinyl chloride resins and copolyester resins are preferred. The thickness of the protective film is not particularly limited. In order to give full play to the protective function, the thickness is preferably 15 to 150 μm.

[0160] The present invention also provides a film-coated metal laminate, wherein a metal plate is laminated on the above-mentioned coating alternative film. The film-coated metal laminate in the present invention can be laminated by thermally pressing the metal plate and the A layer side of the above-mentioned laminated film, and an adhesive for lamination may not be used in particular. The metal plate is usually rolled into a roll, and the coating alternative film can also be made into a product in the form of a roll, so if they are used, roll-to-roll lamination can be used.

[0161] As a preferred manufacturing method for the above-mentioned film-coated metal laminate, for example, by heating the metal plate and using a roller to press the A layer side of the supplied coating alternative film to the metal plate, the coating alternative film is pasted to the metal plate. In other words, in order to obtain a laminate, the heated metal plate and the coating alternative film can be pressed. At this time, by setting the temperature T of the metal plate during hot pressing to the melting point TmA of the laminated film A layer and within the melting point TmB of the laminated film B layer, it is possible to ensure the melt infiltration between the metal plate and the A layer and suppress the melting of the B layer, so that excellent adhesion and excellent processing formability with the metal plate can be obtained. The hot-pressed coating alternative film is partially molten due to the heat from the metal plate, but it solidifies and recrystallizes during the cooling process, thereby reducing the subsequent molding processability. In order to prevent this situation, it is preferred to quench the film-covered metal laminate after hot pressing. The quenching method is not particularly limited, and known methods such as immersion in a cold water tank and blowing cold water can be used. The time from thermocompression bonding to rapid cooling may be as short as possible, preferably within 5 seconds, more preferably within 3 seconds, and particularly preferably within 1 second.

[0162] The metal plate used in the hot pressing can be appropriately selected from known metal plates according to the purpose of use of the metal component, and examples include steel plates, galvanized steel plates, tin-free steel (chrome-plated steel plates), tinplates, aluminum plates, stainless steel plates, etc., but are not limited to them. Usually, a metal plate with good formability and a thickness of about 0.3 to 1.0 mm is used, so it is preferred to use such a level. For example, if it is a metal plate used in a vehicle exterior, a steel plate with a thickness of 0.4 to 0.8 mm and an aluminum plate with a thickness of 0.6 to 1.2 mm, which is applied as a rust-proof treatment, are preferred.

[0163] The present invention also provides a metal component, i.e., a processed product, which is obtained by molding the above-mentioned film-covered metal laminate by press molding. As a press molding method, cold press molding is preferred. When cold press molding is performed using the above-mentioned film-covered metal laminate, whether it is a protruding molding to maintain the end of the metal plate with high pressure, or a molding to maintain it with low pressure and gradually absorb the metal plate through molding (deep drawing molding), by pre-hot pressing to the surface of the metal plate as described above, the surface of the metal component can be covered with a coating substitute film.

[0164] The metal component is preferably used for vehicle exterior parts of vehicles such as automobiles and motorcycles. The present invention can be suitably used for vehicle exterior parts that require excellent appearance design. As a vehicle exterior part, a shell panel is preferred. The present invention is not limited thereto and can be used for ships (speedboats, etc.), home appliances, audio products, construction components, steel plate products, etc.

[0165] Example

[0166] Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to these examples. It should be noted that each characteristic value is measured by the following method. In addition, the parts and % in the examples refer to parts by mass and mass % respectively unless otherwise specified.

[0167] (A) Method for measuring intrinsic viscosity

[0168] 0.2 g of the polyester resin was dissolved in 50 ml of a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (60 / 40 (mass ratio)), and the viscosity was measured using an Ostwald viscometer at 30° C. The unit is dl / g.

[0169] (B) Method for determining melting point (Tm)

[0170] The measurement was performed using a DSC-60 differential scanning calorimeter (manufactured by Shimadzu Corporation). After heating and melting the polyester resin at 300°C for 5 minutes, it was quenched with liquid nitrogen. 10 mg of the quenched polyester resin was used as a sample, and the temperature was raised at a rate of 20°C / min. The endothermic peak temperature (melting point) was measured based on the crystalline melting that occurred at this time. The melting points of the A and B layers of the polyester film were measured in the same manner as above using samples cut from the respective surfaces of the A and B layers of the polyester film. Here, the melting point peak is set as an endothermic peak of 0.05 J / g or more accompanied by crystalline melting on the side closer to the high temperature than the baseline shift corresponding to the glass transition temperature.

[0171] (C) Thickness of each layer of polyester film

[0172] The polyester film was cut into 2 mm in the flow direction and 2 cm in the width direction, and then fixed in an embedding capsule and embedded with epoxy resin. In addition, the embedded sample was cut perpendicularly to the width direction using a slicer (Reichert-Jung, Supercut) to make a 50 μm thick film slice. A scanning electron microscope (Hitachi 4300SE / N) was used to observe and photograph at an accelerating voltage of 20 kV, and the thickness of each layer was measured based on the photographs to obtain the average thickness of 5 points.

[0173] (D) Plane orientation coefficient

[0174] The refractive index in the flow direction (Nx), the refractive index in the width direction (Ny), and the refractive index in the thickness direction (Nz) of the polyester film were measured using an Abbe refractometer using sodium D-rays as a light source according to JIS K 7142-1996A method, and the plane orientation coefficient ΔP was calculated using the following formula 2.

[0175] Formula 2: Plane orientation coefficient ΔP = (Nx + Ny) / 2 - Nz

[0176] (E) Thermal shrinkage

[0177] According to the size of 10mm width × 150mm length, 5 points are cut out from the flow direction and width direction of the polyester film as test pieces. For each test piece, a marking line with an interval of 100mm±2mm is marked with the center of the test piece as the center. The marking line interval of the test piece before heating is measured with an accuracy of 0.1mm. The test piece is suspended in a hot air dryer (made by ESPEC, PHH-202) in a load-free state and heat treated at 150°C for 15 minutes. After the test piece is taken out of the constant temperature bath and cooled to room temperature, the length and width are measured for the same part as the initial measurement. Regarding the heat shrinkage rate, that is, the dimensional change rate of each test piece, the dimensional change is calculated as a percentage of the initial value in the flow direction and the width direction. The dimensional change rate in each direction is set to the average of the measured values ​​in that direction.

[0178] In other words, the heat shrinkage rate in each direction is calculated using the following formula.

[0179] Thermal shrinkage (%) = {(L0-L) / L0} × 100

[0180] Here, L is the distance between the marking lines after the heat treatment (in other words, the distance between a pair of marking lines), and L0 is the distance between the marking lines before the heat treatment. As described above, L and L0 are substituted with the average values ​​of five test pieces.

[0181] (F) Elastic strain energy

[0182] According to JIS K 7127, test samples with a width of 15 mm and a length of 100 mm were cut out in the flow direction and the width direction of the polyester film, respectively. The tensile test was carried out under the following conditions using a tensile testing machine (Autograph AG-I, manufactured by Shimadzu Corporation): the film was stretched to 20% elongation at a distance of 50 mm between the clamps and a tensile speed of 1000 mm / min, and after 20% elongation, the distance between the clamps was restored to 50 mm at a speed of 2000 mm / min. The tensile test was carried out using a thermostatic bath at 100°C. Based on the obtained stress-strain curve, the stress F20 value of the test sample at 20% elongation, and the calculation formulas of Formula 3 and Formula 4 were used to calculate the elastic strain energy Ua from the test start point 0 to the yield point and the elastic strain energy Ub of the recovery strain from the elongation of 20% to the distance between the clamps of 50 mm.

[0183] (Formula 3)

[0184]

[0185] (Formula 4)

[0186]

[0187] Here, if Figure 1 As shown, a refers to the strain at the yield point (%), and P1 refers to the stress at the yield point (MPa). b refers to the strain at which the stress shows 0 MPa after 20% elongation, that is, the recovery strain (%). That is, b refers to the strain at which the stress shows 0 MPa when the distance between the clamps is restored to 50 mm (%). P2 refers to the stress at 20% elongation (MPa). P refers to stress. λ refers to the strain (%).

[0188] It should be noted that, using the stress-strain curve, the initial stress at which the stress increase reaches 0.010MPa or less for every 0.3% increase in strain is obtained as the yield point. Specifically, first, in the stress-strain curve, from 1.0% strain, the stress is read for every 0.3% increase in strain. That is, the stress is obtained for strains of 1.0%, 1.3%, 1.6%, 1.9%, 2.2%, 2.5%, 2.8%, 3.1%..., respectively. In addition, the initial stress at which the stress increase reaches 0.010MPa or less for every 0.3% increase in strain is obtained as the yield point.

[0189] (G) Evaluation of the lamination appearance of film and metal plate (lamination evaluation)

[0190] The A layer side of the polyester film and a 0.6 mm thick zinc alloy plated steel plate were thermocompression bonded at 260° C., and the appearance was visually evaluated according to the following evaluation criteria.

[0191] Judgement A: No wrinkles or bubbles were observed.

[0192] C: At least one of wrinkles and bubbles can be clearly observed.

[0193] (H) Peel strength between film and metal plate

[0194] When the A layer side of the polyester film is thermocompressed with an aluminum metal plate having a thickness of 0.9 mm at 230°C, a heat-resistant paper is clamped to make a peeling end. The film-coated metal laminate with the obtained peeling end is cut into a size of 20 mm in width and 150 mm in length. A tensile tester is used, with one clamp clamping the aluminum metal plate and the other clamp clamping the film peeling end. Three tensile tests are performed along the 180° direction, and the average value of the maximum load at this time is set as the peeling strength. The distance between the clamps is set to 50 mm, and the tensile speed is set to 50 mm / min.

[0195] (I) Evaluation of Adhesion after Cold Press Forming

[0196] The A layer side of the polyester film is hot-pressed with a steel plate having a thickness of 0.6 mm and zinc alloy plating, and the obtained film-coated metal laminate is cut into a size of 180 mm in width and 180 mm in length, and then cold press forming is performed. A mold with a drawing ratio of 1.3 is used, and the surrounding part of the steel plate is clamped with a load of 15 tons, and the center of the steel plate is pressurized at room temperature with 100 tons for deep drawing. A scratch with an × (cross) mark is made in the center of the obtained metal molded product (i.e., the film-coated metal laminate formed by deep drawing). Specifically, a cutting knife is used to make an X-shaped cut that reaches not only the polyester film but also the steel plate (specifically, the steel plate plated with zinc alloy). In addition, a cooking processor is used to perform a treatment at 120°C, 0.2Mpa, and 2hr. For the film bonded to the molded product, the bonding strength of the bonding part is determined as follows.

[0197] Judgement A: No peeling

[0198] Judgment B: Local peeling (whitening is observed locally)

[0199] Judgment C: Peeling exists (whitening is observed as a whole)

[0200] In Examples and Comparative Examples, the following resins were used as the resin constituting the layer B of the laminated film.

[0201] (Resin composition A)

[0202] As the resin composition A, a mixture of the following resin B and resin C was used.

[0203] Resin B: PET resin, IV = 0.75 dl / g, melting point: 255°C 97.0 parts by mass

[0204] Resin C: PET resin containing 0.036% by mass of silica particles (average particle size: 1.7 μm) in 100% by mass of the resin, IV = 0.75 dl / g, melting point: 255°C, 3.0 parts by mass

[0205] (Resin composition D)

[0206] As the resin composition D, a mixture of the following resin E and resin F was used.

[0207] Resin E: PET resin, IV = 0.62 dl / g, melting point: 255°C, 90.0 parts by mass

[0208] Resin F: PET resin containing 0.72% by mass of silica particles (average particle size: 2.7 μm) in 100% by mass of the resin, IV = 0.62 dl / g, melting point: 255°C, 10.0 parts by mass

[0209] (Resin composition G)

[0210] PET resin, IV = 0.69 dl / g, melting point: 225°C 100.0 parts by mass

[0211] (Resin composition H)

[0212] As the resin composition H, a mixture of the following resin I and resin J was used.

[0213] Resin I: Copolymerized polyester resin containing 89.2 mol% of ethylene terephthalate units and 10.8 mol% of ethylene isophthalate units, IV = 0.71 dl / g, melting point: 225°C 55.0 parts by mass

[0214] Resin J: PBT resin, IV = 0.67 dl / g, melting point: 225°C, 45.0 parts by mass

[0215] In Examples and Comparative Examples, the following resins were used as the resin constituting the layer A of the laminated film.

[0216] (Resin K)

[0217] Copolymerized polyester resin containing 89.2 mol% of ethylene terephthalate units and 10.8 mol% of ethylene isophthalate units, IV = 0.63 dl / g, melting point: 225°C

[0218] (Resin L)

[0219] Copolymerized polyester resin containing 86.0 mol% of ethylene terephthalate units and 14.0 mol% of ethylene isophthalate units, IV = 0.70 dl / g, melting point: 217°C

[0220] (Resin M)

[0221] Copolymerized polyester resin containing 80.0 mol% of ethylene terephthalate units and 20.0 mol% of ethylene isophthalate units, IV = 0.63 dl / g, melting point 198°C

[0222] (Resin N)

[0223] Copolymerized polyester resin containing 92.1 mol% of ethylene terephthalate units and 7.9 mol% of ethylene isophthalate units, IV = 0.62 dl / g, melting point: 233°C

[0224] [Example 1]

[0225] The resin composition A for the B layer and the resin K for the A layer are supplied to their respective hoppers. After the A layer and the B layer are melted at 280°C, they are merged into two layers in the mold and extruded onto a cooling drum to form an unstretched sheet. Thereafter, the unstretched sheet is stretched 3.2 times along the flow direction at 80°C, and then stretched 3.0 times along the width direction at 130°C. After heat fixing at 215°C, a process of relaxing 5% along the width direction is implemented. In this way, a polyester film consisting of two layers of A layer and B layer with a thickness of 10μm for the A layer, a thickness of 40μm for the B layer, and a total thickness of 50μm is produced.

[0226] [Example 2]

[0227] A polyester film consisting of two layers, the A layer and the B layer, was produced in the same manner as in Example 1 except that the film was stretched 3.9 times in the flow direction and 3.5 times in the width direction.

[0228] [Example 3]

[0229] A polyester film consisting of two layers, A layer and B layer, was prepared in the same manner as in Example 1 except that the resin composition D was used as the B layer resin and the film was stretched 3.5 times in the flow direction and 3.3 times in the width direction.

[0230] [Comparative Example 1]

[0231] A polyester film consisting of two layers, A layer and B layer, was prepared in the same manner as in Example 1 except that the resin L was used as the A layer resin and the film was stretched 3.0 times in the flow direction and 3.5 times in the width direction.

[0232] [Comparative Example 2]

[0233] Resin composition D was used as the resin for layer B, stretched 3.5 times in the flow direction and 3.3 times in the width direction, and the heat fixing temperature was set to 235°C. Except for this, a polyester film consisting of two layers, layer A and layer B, was prepared using the same method as in Example 1.

[0234] [Comparative Example 3]

[0235] Resin composition D was used as the resin for layer B, and resin L was used as the resin for layer A. The films were stretched 3.8 times in the flow direction and 3.3 times in the width direction. In addition, a polyester film consisting of two layers, layer A and layer B, was prepared using the same method as in Example 1.

[0236] [Comparative Example 4]

[0237] Resin composition D was used as the resin for layer B, and resin M was used as the resin for layer A. The films were stretched 3.5 times in the flow direction and 3.3 times in the width direction. In addition, a polyester film consisting of two layers, layer A and layer B, was prepared using the same method as in Example 1.

[0238] [Comparative Example 5]

[0239] A polyester film consisting of two layers, A layer and B layer, was prepared in the same manner as in Example 1 except that resin N was used as the A layer resin and the film was stretched 3.0 times in the flow direction and 3.5 times in the width direction.

[0240] [Comparative Example 6]

[0241] Resin composition H is used as the resin for layer B and layer A, and is stretched 3.0 times along the flow direction and 3.0 times along the width direction. The heat fixing temperature is set to 205°C. Except for this, the same method as in Example 1 is used to prepare a polyester film in which layer A and layer B are both composed of a single layer of the same raw material.

[0242] [Comparative Example 7]

[0243] Resin composition G is used as the resin for layer B and layer A, and is stretched 3.1 times along the flow direction and 3.5 times along the width direction. The heat fixing temperature is set to 180°C. Except for this, the same method as in Example 1 is used to prepare a polyester film in which layer A and layer B are both composed of a single layer of the same raw material.

[0244] [Comparative Example 8]

[0245] The polyester film was produced by the method described in Example 7 of Patent Document 2 (ie, Japanese Patent Application Laid-Open No. 2020-192787). The production conditions such as the resin used in the A layer and the stretch ratio are shown in Table 1C below.

[0246] The evaluation results of the polyester films produced in Examples 1 to 3 and Comparative Examples 1 to 8 are shown in Table 1. In the evaluation of adhesion after cold press forming, the thermal compression bonding of the film and the zinc alloy plated steel plate was performed by heating the metal plates to the temperatures shown in Table 1, respectively.

[0247] [Table 1A]

[0248]

[0249] [Table 1B]

[0250]

[0251] [Table 1C]

[0252]

[0253] As shown in Table 1, the polyester film produced in the example has good lamination properties for metal plate lamination and good adhesion to metal molded products. On the other hand, the polyester film produced in the comparative example shows poor results in either or both of the lamination properties for metal plates and the adhesion to metal molded products, and is not suitable as a coating replacement film. In particular, the residual index rate of internal stress in Comparative Examples 1 to 4, 6 and 7 is significantly greater than that in Examples 1 to 3, and the adhesion determination results in these comparative examples are also worse than those in Examples 1 to 3. On the other hand, the residual index rate of internal stress in Comparative Example 5 is a value similar to that in Example 2, but in the 260°C hot pressing, the polyester film is not firmly bonded to the metal plate, so the peel strength is poor and the adhesion determination result is poor. It should be noted that in the preliminary experiment, it has been confirmed that wrinkles and bubbles will be generated when the polyester film of Comparative Example 5 is hot pressed to the metal plate at 280°C in order to make it firmly bonded to the metal plate. The residual index rate of internal stress in Comparative Example 8 was similar to that in Example 1, but the thermal shrinkage was large (ie, the thermal shrinkage rate was large), and wrinkles and bubbles were generated during thermal compression bonding at 260° C. In addition, the peel strength in Comparative Example 8 was poor, and the adhesiveness evaluation result was poor.

Claims

1. A coating replacement film comprising a laminated film, wherein the laminated film comprises an A layer and a B layer, The A layer comprises a first crystalline polyester as a main constituent component, The B layer contains a second crystalline polyester as a main constituent component, The plane orientation coefficient of the B layer is 0.165 or more and 0.180 or less, The melting point of the B layer is higher than the melting point of the A layer, and the difference between the melting point of the B layer and the melting point of the A layer is 25° C. or more and 35° C. or less, When the laminate film is subjected to a tensile test, the residual index rate of the internal stress in the flow direction and the width direction of the laminate film is 25% or less. The residual index rate is represented by |1-(Ub / Ua)|×100, The tensile test was conducted by the following method: a 15 mm wide test piece was clamped by a pair of clamps with a distance between the clamps of 50 mm, the distance between the clamps was widened at a tensile speed of 1000 mm / min at 100°C until a strain of 20% was generated, and then the distance between the clamps was restored to 50 mm at a speed of 2000 mm / min at 100°C. The Ua is a value obtained by integrating the stress-strain curve obtained by the tensile test from 0% strain to yield strain. The Ub is a value obtained by integrating the stress-strain curve from a strain of 20% to a strain at which the stress shows 0 MPa.

2. The coating replacement film according to claim 1, wherein: In the flow direction and the width direction of the laminated film, the 20% strain tensile stress in the tensile test is 60 MPa or more and 110 MPa or less.

3. The coating replacement film according to claim 1, wherein: The plane orientation coefficient of the B layer is greater than the plane orientation coefficient of the A layer, and the difference between the plane orientation coefficient of the B layer and the plane orientation coefficient of the A layer is greater than or equal to 0.

03.

4. The coating replacement film according to claim 1, wherein: When the laminated film is heat-treated at 150° C. for 15 minutes, the sum of the heat shrinkage in the flow direction and the heat shrinkage in the width direction is 1.0% or more and 5.0% or less.

5. The coating replacement film according to claim 1, wherein: After the coating alternative film is laminated on the metal substrate at 230° C. in such a manner that the A layer contacts the metal substrate, the coating alternative film has a peel strength of 10 N / 20 mm or more when peeled off from the metal substrate at a tensile speed of 50 mm / min and 180°.

6. The coating-substitute film according to claim 1, further comprising an easy-adhesion layer and a functional layer, wherein the easy-adhesion layer is provided on the surface of the B layer of the laminated film, The A layer, the B layer, the easy-adhesion layer and the functional layer are arranged in sequence, The functional layer includes at least one of a coloring layer and a surface protection layer.

7. The coating replacement film according to claim 6, wherein: The easy-adhesion layer includes a resin having at least one functional group selected from the group consisting of an epoxy group, an oxazoline group, a silanol group, and an isocyanate group.

8. The coating replacement film according to claim 6, wherein: The functional layer includes the coloring layer and the surface protection layer, The A layer, the B layer, the easy-adhesion layer, the coloring layer, and the surface protection layer are arranged in this order.

9. The coating replacement film according to claim 6, wherein: The functional layer includes the colored layer, The colored layer contains a colorant in an amount of 0.5% by mass or more and less than 40% by mass based on 100% by mass of the resin composition constituting the colored layer.

10. The coating replacement film according to claim 6, wherein: The functional layer includes the surface protection layer, The surface protection layer includes at least one of a thermosetting resin and a photocurable resin.

11. The coating replacement film according to claim 6, wherein: The thickness of the easy-adhesion layer is 10 nm to 200 nm.

12. A laminate comprising: Metal sheets; and The paint-substitute film according to any one of claims 1 to 11 laminated on the metal plate.

13. A metal member obtained by press-molding the laminate according to claim 12. 14 . A vehicle exterior component comprising the laminate according to claim 12 .

15. A method for producing a laminate, comprising: A step of heating a metal plate to a temperature not less than the melting point of the A layer and not more than the melting point of the B layer in the paint-substitute film according to any one of claims 1 to 11; as well as A step of pressure-bonding the metal plate heated to the temperature and the paint-substitute film so that the metal plate contacts the A layer.

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