Method for producing laminated film for decoration

Abstract

To provide a method for producing a laminated film for decoration which is formed by laminating an acrylic resin film and a vinylidene fluoride-based resin film, has high stretchability, and has good transparency of the vinylidene fluoride-based resin film even after stretching.SOLUTION: A method for producing a laminated film for decoration includes the steps of: heating and melting a vinylidene fluoride-based resin composition containing a vinylidene fluoride-based resin, and 0.3 pts.mass or more and 5.0 pts.mass or less of an alkyl quaternary ammonium sulfate, with respect to 100 pts.mass of the vinylidene fluoride-based resin; heating and melting an acrylic resin composition containing an acrylic resin; coextruding the heated and melted vinylidene fluoride-based resin composition and the heated and melted acrylic resin composition, and forming a laminated film; and bringing the formed laminated film into contact with a cooling roll having a surface temperature of 125°C or lower while keeping the temperature of the laminated film at 150°C or higher, and cooling the laminated film.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a decorative laminate film. [Background technology]

[0002] Decorative films are often applied to automobiles, home appliances, furniture, buildings, etc. to improve durability and decoration. In particular, for the interior and exterior of automobiles, replacing the conventional paint with decorative films is expected to improve design, reduce weight, simplify the manufacturing process, and reduce environmental pollution caused by solvents contained in paint.

[0003] As a decorative film, a highly transparent acrylic resin film (hereinafter, acrylic resin may be referred to as "AC resin," acrylic resin film may be referred to as "AC resin film," and acrylic resin composition may be referred to as "AC resin composition") is used so as not to impair the design expression of the substrate. On the other hand, AC resin films have poor chemical resistance, so laminate films are used in which vinylidene fluoride resin films (hereinafter, vinylidene fluoride resin may be referred to as "VDF resin," vinylidene fluoride resin film may be referred to as "VDF resin film," and vinylidene fluoride resin composition may be referred to as "VDF resin composition"), which have excellent chemical resistance, weather resistance, scratch resistance, etc., are laminated onto AC resin films (Patent Document 1, Patent Document 2, etc.).

[0004] The decorative film is attached to the surface of the substrate while being heated and stretched by a method such as vacuum forming or pressure forming (Patent Document 1, Patent Document 2, etc.). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-187934 [Patent Document 2] International Publication No. 2021 / 161899 Summary of the Invention [Problem to be solved by the invention]

[0006] Although VDF-based resin films generally do not lose transparency (do not become hazy) when stretched while heated, the inventors have found that a laminate film in which a VDF-based resin film is laminated with an AC-based resin film has a problem in that the transparency of the VDF-based resin film decreases when stretched while heated.

[0007] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a method for producing a decorative laminate film in which an AC-based resin film and a VDF-based resin film are laminated together, wherein the transparency of the VDF-based resin film remains good even after stretching. [Means for solving the problem]

[0008] One embodiment of the present invention for solving the above problems relates to the following methods [1] to [5] for producing a decorative laminate film. [1] A method for producing a decorative laminate film, comprising the steps of: heat-melting a vinylidene fluoride resin composition containing a vinylidene fluoride resin and 0.3 to 5.0 parts by mass of an alkyl quaternary ammonium sulfate per 100 parts by mass of the vinylidene fluoride resin; heat-melting an acrylic resin composition containing an acrylic resin; co-extruding the heat-melted vinylidene fluoride resin composition and the heat-melted acrylic resin composition to form a laminate film; and cooling the formed laminate film by contacting it with a cooling roll having a surface temperature of 125°C or less while maintaining the temperature at 150°C or higher. [2] The method for producing a decorative laminate film according to [1], wherein the acrylic resin is a methacrylic acid ester resin. [3] The method for producing a decorative laminate film according to [1] or [2], wherein the vinylidene fluoride resin composition contains a vinylidene fluoride resin having an inherent viscosity of 0.80 dL / g or more and 1.20 dL / g or less. [4] The method for producing a decorative laminate film according to any one of [1] to [3], wherein the alkyl quaternary ammonium sulfate is tetrabutylammonium hydrogen sulfate. [5] The method for producing a decorative laminate film according to any one of [1] to [4], wherein the vinylidene fluoride resin composition has a melting temperature of 210°C or higher and 260°C or lower. [Effects of the Invention]

[0009] According to the present invention, there is provided a method for producing a decorative laminated film in which an AC-based resin film and a VDF-based resin film are laminated, and the VDF-based resin film has good transparency even after stretching. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Laminated film manufacturing method] One embodiment of the present invention relates to a method for producing a decorative laminated film (hereinafter sometimes simply referred to as "laminate film") in which a VDF-based resin film and an AC-based resin film are laminated together.

[0011] The laminate film is produced by heat-melting a VDF-based resin composition (first heat-melting step), heat-melting an AC-based resin composition (second heat-melting step), co-extruding the heat-melted VDF-based resin composition and AC-based resin composition to form a laminate film (film-forming step), and cooling the formed laminate film by contact with a cooling roll (cooling step). The first heat-melting step is performed by a first extruder, and the second heat-melting step is performed by a second extruder simultaneously with the first heat-melting step. The VDF-based resin composition and AC-based resin composition heat-melted in these heat-melting steps are then co-extruded in the film-forming step.

[0012] (First heat melting step) In the first heat-melting step, a VDF-based resin composition containing a VDF-based resin is heat-melted in a first extruder.

[0013] The heating temperature (cylinder temperature) in the first kneader is preferably 210°C or higher and 260°C or lower, and more preferably 210°C or higher and 240°C or lower. By setting the heating temperature to 210°C or higher, the VDF-based resin can be melted and thoroughly kneaded. By setting the heating temperature to 260°C or lower, yellowing and deterioration of transparency due to decomposition of alkyl quaternary ammonium sulfate and the like can be suppressed.

[0014] The VDF resin composition has a wavelength of 1700 cm in the infrared absorption spectrum when made into a VDF resin film. -1 ~1740cm -1 The absorbance A of the peak measured in the range of 860 cm -1 ~880cm -1 The ratio (A / B) of the absorbance A of the peak measured in the range of A to the absorbance B of the peak measured in the range of A is preferably 0.12 or less. The absorbance A corresponds to the content of the AC resin contained in the VDF resin composition and the VDF resin film. The absorbance B corresponds to the content of the VDF resin contained in the VDF resin composition and the VDF resin film. A VDF resin film with a small ratio A / B and a low content of AC resin, etc., is less likely to suffer from a decrease in chemical resistance due to the AC resin, etc., after stretching. The ratio A / B is preferably 0.00 or more and 0.12 or less, and more preferably 0.00 or more and 0.07 or less.

[0015] In this embodiment, the crystallinity of the VDF-based resin is maintained while the microstructure, such as the crystal size and crystal arrangement, is appropriately controlled by adding alkyl quaternary ammonium sulfate to the VDF-based resin and optimizing the cooling rate of the film during production. This reduces the tensile modulus and increases the elongation at break while maintaining the hardness of the VDF-based resin film. The microstructure may also be further controlled by copolymerizing vinylidene fluoride with a fluorinated olefin or by the inherent viscosity of the VDF-based resin.

[0016] The transparency of a polymer film can be evaluated by its haze. Higher haze indicates lower transparency. VDF-based resin films do not easily increase in haze when stretched alone. On the other hand, when a VDF-based resin film is laminated to an AC-based resin film, the haze of the laminated film increases during stretching. The increase in haze is primarily due to an increase in the haze of the VDF-based resin film. The reason why the haze of the laminated film increases upon stretching is unclear, but the inventors believe the reason is as follows. Because the VDF-based resin and the AC-based resin are compatible at the interface of the laminated film, the polymer chains of the VDF-based resin are bound to the polymer chains of the AC-based resin. In particular, the constraint of the polymer chains between the crystals of the VDF-based resin prevents stress relaxation during stretching, resulting in stress concentration. In contrast, stress concentration due to stretching is low within the VDF-based resin film away from the interface with the AC-based resin. It is believed that the coexistence of areas in the film where stress concentration occurs during stretching and areas where stress concentration is relatively low causes voids to form between the molecular chains that make up the film, resulting in high haze in the VDF-based resin film. On the other hand, in this embodiment, by appropriately controlling the microstructure, such as by loosening the arrangement of the VDF-based resin molecular chains, stress concentration is suppressed, and the occurrence of cracks and surface irregularities that increase haze when stretched is suppressed, making it possible to produce a laminated film that also suppresses a decrease in transparency after stretching.

[0017] The VDF-based resin may be a homopolymer of vinylidene fluoride (hereinafter sometimes abbreviated as "VDF") or a copolymer containing VDF as the main component. "Containing VDF as the main component" means that the mass ratio of VDF-derived structural units to the total mass of the VDF-based resin is 50% by mass or more. From the viewpoint of improving the stretchability of the laminated film, a copolymer is preferred. Examples of the copolymer include VDF-hexafluoropropylene copolymer, VDF-tetrafluoroethylene copolymer, and VDF-tetrafluoroethylene-hexafluoropropylene copolymer, with VDF-hexafluoropropylene copolymer being particularly preferred from the viewpoint of further improving the stretchability. The content of other structural units (i.e., structural units derived from hexafluoropropylene or tetrafluoroethylene) in the copolymer is preferably 1.0% by mass or more and 12.0% by mass or less, more preferably 1.0% by mass or more and 5.0% by mass or less, and even more preferably 1.5% by mass or more and 3.0% by mass or less. When the amount of other structural units is 1.0% by mass or more, the stretchability of the laminated film is improved, resulting in a high breaking elongation. Furthermore, since the crystallinity of the VDF-based resin is appropriately reduced, cracks are less likely to occur during stretching, and a decrease in transparency after stretching due to cracks (increases in internal and external haze) is less likely to occur. When the amount of other structural units is 12.0% by mass or less, slight irregularities caused by the cooling roll with which the laminated film comes into contact during production are less likely to form on the surface. These irregularities are less likely to spread during stretching, causing surface roughness and resulting in a decrease in transparency (increases in external haze). The VDF-based resin may be commercially available or may be obtained by polymerization using a conventional method.

[0018] The content of structural units derived from hexafluoropropylene (hereinafter sometimes abbreviated as "HFP") in a VDF-based resin is defined as the ratio of the content of fluorine atoms derived from HFP to the content of all fluorine atoms in the resin. 19 The content of structural units derived from HFP contained in a VDF-based resin can be determined by F-NMR measurement.

[0019] The inherent viscosity of the VDF-based resin is preferably 0.80 dl / g or more but 1.20 dl / g or less, and more preferably 0.80 dl / g or more but 1.05 dl / g or less. Generally, as the molecular weight decreases, thermal molecular motion tends to become easier. Even in polymer compounds, the lower the degree of polymerization, the easier the molecular chain motion. Therefore, the lower the inherent viscosity, the lower the degree of polymerization, which facilitates polymer chain rearrangement upon cooling, resulting in faster crystallization and easier crystal growth. Therefore, it tends to be difficult to control the microstructure, such as by loosening the molecular chains to alleviate stress concentration during stretching. If the inherent viscosity is 0.80 dl / g or less, it becomes difficult to control the microstructure. Stress concentration due to constraints at the interface of the laminated film during stretching tends to lead to the generation of microvoids in the VDF-based resin film, resulting in increased haze. If the inherent viscosity is 0.80 dl / g or more, the stretchability of the laminated film improves, resulting in a higher breaking elongation. If the inherent viscosity exceeds 1.20 dl / g, the stretchability of the laminated film decreases, resulting in a low elongation at break, which is undesirable.

[0020] The inherent viscosity of VDF-based resin is measured in accordance with JIS K 7367-1:2002. Specifically, 80 mg of VDF-based resin is dissolved in 20 ml of N,N-dimethylformamide, and the viscosity η of the polymer solution is measured using an Ubbelohde viscometer in a thermostatic bath at 30°C. The viscosity η of the polymer solution and the viscosity η of N,N-dimethylformamide used as a solvent are then calculated. o Based on the solution concentration C (g / dl), the inherent viscosity η is calculated using the following formula: i Calculate (dl / g). η i =(1 / C)·ln(η / η o ) Here, the concentration of the solution is 0.4 (g / dl)

[0021] The VDF resin film contains an alkyl quaternary ammonium sulfate, which is a compound represented by the following formula (1):

[0022] [ka]

[0023] In formula (1), R 1 ~R 4 are independently alkyl groups having 1 to 10 carbon atoms. 1 ~R 4 Examples of the alkyl group in R include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group. 1 ~R 4 The total number of carbon atoms in the alkyl group is preferably 6 or more and 30 or less, more preferably 6 or more and 24 or less, and even more preferably 8 or more and 20 or less.

[0024] In formula (1), R 5 R is an alkyl group having 1 to 10 carbon atoms, a fluoroalkyl group having 1 to 10 carbon atoms, or a hydrogen atom. 5 Examples of the alkyl group in R include a methyl group and an ethyl group. 5 Examples of fluoroalkyl groups in R include CF3 and C2F5. 5 is preferably hydrogen.

[0025] Examples of alkyl quaternary ammonium sulfates include (C2H5)4N + , (C3H7)4N + , (C4H9)4N + , and (CH 11 )4N + and alkyl quaternary ammonium cations such as CF3SO4 - , CH3SO4 - , and HSO4 - These compounds may be used alone or in combination of two or more.

[0026] The alkyl quaternary ammonium sulfate is preferably an alkyl quaternary ammonium hydrogen sulfate. Examples of the alkyl quaternary ammonium hydrogen sulfate include tetraethylammonium hydrogen sulfate, tetrapropylammonium hydrogen sulfate, tetrabutylammonium hydrogen sulfate, tetrapentylammonium hydrogen sulfate, and tetrahexylammonium hydrogen sulfate.

[0027] The amount of alkyl quaternary ammonium sulfate is 0.3 to 5.0 parts by weight, preferably 0.4 to 2.0 parts by weight, and more preferably 0.6 to 1.3 parts by weight, per 100 parts by weight of VDF-based resin. When the amount of alkyl quaternary ammonium sulfate is 0.3 parts by weight or more, the microstructure of the VDF-based resin is likely appropriately controlled, thereby improving the stretchability of the VDF-based resin film. Furthermore, appropriately controlling the microstructure of the VDF-based resin is thought to reduce the occurrence of cracks in the VDF-based resin film during stretching, thereby reducing the likelihood of a decrease in transparency (increase in internal haze and external haze) after stretching. When the amount of alkyl quaternary ammonium sulfate is 5.0 parts by weight or less, the alkyl quaternary ammonium sulfate and VDF-based resin can be thoroughly mixed during the production of the VDF-based resin.

[0028] The VDF resin film may contain antioxidants, ultraviolet absorbers, light stabilizers, lubricants, release agents, antistatic agents, flame retardants, reinforcing agents, nucleating agents, bluing agents, and the like, as long as the laminated film satisfies the properties described below.

[0029] (Second heat melting process) In the second heat-melting step, the AC resin composition containing the AC resin is heat-melted in a second extruder.

[0030] The heating temperature (cylinder temperature) in the second kneader is preferably 200°C or higher and 260°C or lower, and more preferably 200°C or higher and 240°C or lower. By setting the heating temperature to 200°C or higher, the AC-based resin can be melted and thoroughly kneaded. By setting the heating temperature to 260°C or lower, yellowing and deterioration of transparency due to decomposition of the AC-based resin and additives can be suppressed.

[0031] As the AC-based resin, a known homopolymer or copolymer of (meth)acrylic acid ester can be used. In this specification, (meth)acrylic means acrylic or methacrylic.

[0032] From the viewpoint of increasing the surface hardness of the laminated film, the AC resin is preferably a methacrylic acid ester resin (a homopolymer or copolymer of a methacrylic acid ester). The methacrylic acid ester preferably has an alkyl group having 1 to 4 carbon atoms, such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, or t-butyl methacrylate, with methyl methacrylate being more preferred. The AC resin may be a copolymer of these methacrylic acid esters with other AC acid esters or vinyl monomers, but the amount of structural units derived from the methacrylic acid esters is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 80 to 100% by mass. The AC resin may be commercially available or may be obtained by polymerization using a conventional method.

[0033] The AC-based resin composition may contain a fluororesin such as a VDF-based resin, or other resins, but the amount of AC-based resin in the AC-based resin composition is from 50% to 100% by mass, preferably from 70% to 100% by mass, and more preferably from 80% to 100% by mass.

[0034] The AC resin composition may contain ultraviolet absorbers, other resins, plasticizers, heat stabilizers, antioxidants, light stabilizers, crystal nucleating agents, antiblocking agents, sealability improvers, mold release agents, colorants, pigments, foaming agents, flame retardants, and the like, as long as the laminate film satisfies the properties described below.

[0035] (Film forming process) In the film-forming process, the VDF resin and AC resin that have been melt-kneaded in both the first and second heat-melting processes are co-extruded from a feedblock T-die or multi-manifold T-die connected to the first and second extruders, resulting in a molten extrudate in which the VDF resin and AC resin are laminated, which is then formed into a film.

[0036] Co-extrusion from a T-die is preferably carried out so that the thickness (T1) of the VDF-based resin film is preferably 1 μm or more and 30 μm or less, more preferably 1 μm or more and 20 μm or less, even more preferably 2 μm or more and 15 μm or less, and particularly preferably 2 μm or more and 10 μm or less. When the thickness (T1) is 1 μm or more, it is possible to prevent a decrease in transparency after stretching. When the thickness (T1) is 30 μm or less, it is possible to sufficiently increase the hardness of the laminated film.

[0037] Furthermore, coextrusion from a T-die is preferably carried out so that the thickness (T2) of the AC resin film is preferably 25 μm or more and 200 μm or less, more preferably 25 μm or more and 150 μm or less, even more preferably 30 μm or more and 100 μm or less, and particularly preferably 30 μm or more and 75 μm or less. When the thickness (T2) is 25 μm or more, the hardness of the laminated film can be sufficiently increased. When the thickness (T2) is 200 μm or less, the formability, stretchability, and transparency of the laminated film can be improved.

[0038] Furthermore, the ratio (T1 / T2) of the thickness of the VDF resin film (T1) to the thickness of the AC resin film (T2) in the produced laminate film is preferably 1 / 20 to 1 / 4, more preferably 1 / 18 to 1 / 5, even more preferably 1 / 15 to 1 / 8, and particularly preferably 1 / 12 to 1 / 9. Increasing T1 / T2 (increasing the proportion of the VDF resin film thickness) can improve the chemical resistance of the laminate film. Decreasing T1 / T2 (increasing the proportion of the AC resin film thickness) can improve the scratch resistance of the laminate film.

[0039] (cooling process) In the cooling step, the film-formed molten extrudate is cooled by contacting it with a cooling roll while maintaining the temperature at 150° C. or higher. The cooling roll can be a metal mirror-surface touch roll or a metal endless belt.

[0040] The surface temperature of the chill roll is 125°C or lower, preferably 30°C or higher and 100°C or lower, and more preferably 30°C or higher and 70°C or lower. The VDF resin side of the molten extrudate is preferably brought into contact with the chill roll. By bringing the VDF resin into contact with a chill roll set at a relatively low temperature and quenching it, crystallization of the VDF resin is appropriately suppressed, and the crystalline structure of the VDF resin is appropriately controlled. This allows the hardness of the VDF resin film to be maintained, while the tensile modulus is reduced and the elongation at break to be increased.

[0041] The laminated film that has been cooled and solidified can be wound into a roll for storage, transportation, and the like.

[0042] (Laminated film) The laminated film thus produced is composed of an AC resin film and a VDF resin film laminated together, and by appropriately controlling the microstructure of the VDF resin in the VDF resin film, the hardness of the VDF resin film is maintained while the tensile modulus is reduced and the elongation at break is increased, thereby improving the stretchability.

[0043] The laminate film is attached to the surface of a preformed substrate by methods such as vacuum forming or pressure forming, while being heated and stretched. The laminate film has high stretchability, making it easy to attach to the surface shape of the substrate. Furthermore, despite its high stretchability, the laminate film also has high hardness, resulting in high scratch resistance after stretching. Furthermore, despite being laminated with an AC-based resin film, the transparency of the VDF-based resin film is not easily reduced even after stretching, so the laminate film maintains high transparency even after stretching. Furthermore, since the VDF-based resin film contains almost no AC resin, the laminate film also has high chemical resistance after attachment.

[0044] Specifically, the haze of the laminated film measured in an unstretched state is preferably 0.0% or more and 10.0% or less, more preferably 0.0% or more and 6.0% or less, and more preferably 1.0% or more and 4.0% or less.

[0045] The haze is a value measured based on JIS K 7136: 2000 (ISO 14782: 1999).

[0046] Furthermore, the laminated film has a breaking elongation at 23°C measured in an unstretched state in accordance with JIS K 7161-1:2014 (ISO 527-1:2012) of 100% or more and 400% or less, preferably 100% or more and 300% or less, more preferably 130% or more and 300% or less, and even more preferably 130% or more and 250% or less.

[0047] Furthermore, the laminated film preferably has a tensile modulus at 23°C measured in an unstretched state in accordance with JIS K 7161-1:2014 (ISO 527-1:2012) of 500 MPa or more and 1500 MPa or less, more preferably 800 MPa or more and 1400 MPa or less, and even more preferably 1000 MPa or more and 1350 MPa or less.

[0048] Furthermore, the scratch hardness (pencil method) of the laminate film, measured on the VDF resin film side in an unstretched state in accordance with ISO 15184:2020, is preferably HB or more and 6H or less, more preferably HB or more and 2H or less, and even more preferably HB or more and F or less. By sufficiently increasing the hardness in the unstretched state, the scratch resistance after stretching can also be improved.

[0049] The thicknesses T1 and T2 are values ​​measured by observing the cross section of the laminated film cut with a single-edged knife perpendicular to the thickness direction so as to have a smooth cross section.

[0050] The haze of the laminated film when stretched 140% at 120°C is 0.0% or more and 10.0% or less, preferably 0.0% or more and 7.0% or less, more preferably 0.0% or more and 5.0% or less, even more preferably 0.0% or more and 4.0% or less, and particularly preferably 0.0% or more and 3.0% or less. The stretching direction at this time may be either the MD direction or the TD direction of the laminated film. In this embodiment, it is sufficient that the haze when stretched 140% at 120°C in at least one of the MD direction and the TD direction is within the above range.

[0051] [Application] The laminated film produced by the above-mentioned method can be used as a decorative film to be attached by vacuum forming or pressure forming to the surface of interior or exterior substrates of automobiles, railway vehicles, aircraft, ships, spacecraft, home appliances, furniture, buildings, etc. When attaching, the VDF-based resin film is attached to the surface of the substrate so that the VDF-based resin film side faces outward.

[0052] [Other embodiments] It should be noted that the above-described embodiments are exemplary embodiments of the present invention, and it goes without saying that the present invention may include embodiments other than the above-described embodiments within the scope of its core technical concept. [Example]

[0053] The present invention will be described in detail based on examples, but the present invention is not limited to these examples.

[0054] 1. Preparation of laminated film To 100 parts by mass of a VDF homopolymer having an inherent viscosity of 0.85 dl / g was added 1.0 part by mass of tetrabutylammonium hydrogen sulfate (manufactured by Koei Chemical Industry Co., Ltd., hereinafter abbreviated as "TBAHS") The VDF homopolymer to which TBAHS had been added was melt-kneaded at a cylinder temperature of 190°C using a co-rotating twin-screw extruder (manufactured by Shibaura Machine Co., Ltd., TEM-26) to obtain a pelletized VDF-based resin composition 1.

[0055] Various VDF-based resin compositions were obtained in the same manner by varying the inherent viscosity of the VDF-based polymer, the presence or absence and ratio of copolymerization with HFP, and the amount of TBAHS added.

[0056] The VDF-based resin composition obtained above was thermally melted in a 30 mm diameter first extruder with a cylinder temperature set to 230°C. Methyl methacrylate resin (Parapet GR-F, manufactured by Kuraray Co., Ltd.) was thermally melted in a 30 mm diameter second extruder with a cylinder temperature set to 230°C. The thermally melted VDF-based resin composition and methacrylic resin were then co-extruded from a multi-manifold T-die connected to the first and second extruders. The VDF-based resin composition side was then brought into contact with a cooling roll whose surface was set to 98°C for cooling, yielding a laminated film 1 consisting of a 5 μm-thick VDF-based resin layer and a 45 μm-thick methacrylic resin layer (hereinafter referred to as the "AC layer").

[0057] Laminated films 2 to 11 were obtained in the same manner except that the type of VDF resin composition, the melting temperature of each resin, and the surface temperature of the cooling roll were changed.

[0058] The inherent viscosity of the VDF resin was measured in accordance with JIS K 7367-1:2002. Specifically, 80 mg of the VDF resin was dissolved in 20 ml of N,N-dimethylformamide, and the viscosity η of the polymer solution was measured using an Ubbelohde viscometer in a thermostatic bath at 30°C. The viscosity η of the polymer solution and the viscosity η of N,N-dimethylformamide used as the solvent were then calculated. oBased on the solution concentration C (g / dl), the inherent viscosity η is calculated using the following formula: i asked for. η i =(1 / C)·ln(η / η o ) Here, the concentration of the solution is 0.4 g / dl.

[0059] The content of structural units derived from HFP in a VDF-based resin is the ratio of the content of fluorine atoms derived from HFP to the content of all fluorine atoms in the resin. 19 The content of structural units derived from HFP contained in the VDF-based resin was determined by F-NMR measurement.

[0060] 2. Evaluation of laminated film (before stretching) The obtained laminated film was evaluated as follows without being stretched.

[0061] 2-1.Thickness The laminate film was cut perpendicular to the thickness direction using a single-edged knife so that the cross section was smooth. The film cross section was observed at 800x magnification using a digital microscope (Keyence Corporation, VHX-700F) to measure the thicknesses of the VDF-based resin layer and the AC-based resin layer, and the thickness of the VDF-based resin layer (T1) and the thickness of the AC layer (T2) were measured. The thickness was measured at a total of five points: a measurement point set in the center of the laminate film and four other points set at least 50 mm away from the other measurement points, and the average of these measurements was used as the thickness of each layer in the laminate film.

[0062] 2-2. Hayes The haze of the laminated film was measured using a haze meter (NDH4000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7136: 2000 (ISO 14782: 1999). Haze measurements were taken at a total of five locations: a measurement point set at the center of the laminated film and four other locations arbitrarily set at least 50 mm away from the other measurement points, and the average of these measurements was taken as the haze of the laminated film.

[0063] 2-3. Breaking elongation Tensile tests were performed in accordance with JIS K 7161-1:2014 (ISO 527-1:2012) to measure the tensile modulus and elongation at break using a universal testing machine (Shimadzu Corporation, Autograph AGS-J) at a temperature of 23°C and a tensile speed of 50 mm / min.

[0064] 3. Evaluation of laminated film (after stretching) The obtained laminated film was stretched by 140% at 120° C. The laminated film after stretching was evaluated as follows.

[0065] 3-1. Hayes The haze was measured in the same manner as for the laminated film before stretching.

[0066] 3-2.Chemical resistance A small amount of sunscreen cream (Neutrogena UltraSheer SPF45, manufactured by Johnson & Johnson) was applied to the VDF resin film side of the laminated film, the applied area was covered with a cover glass, and the film was left to stand at 80°C for 1 hour. After leaving the film to stand, the adhering sunscreen cream was wiped off, the film was washed with water, and the appearance of the applied area was evaluated according to the following evaluation criteria. ○ No change in appearance is observed. △: Minor application marks or minor wrinkles are observed. × Whitening or obvious deterioration of the surface is observed.

[0067] 4.Results Table 1 shows the preparation conditions and evaluation results of each laminated film.

[0068] [Table 1]

[0069] [Reference example] A VDF homopolymer having an inherent viscosity of 1.00 dl / g was melt-kneaded without adding TBAHS at a cylinder temperature of 190°C using a co-rotating twin-screw extruder (Shibaura Machine Co., Ltd., TEM-26) to obtain a pelletized VDF resin composition.

[0070] The VDF-based resin composition obtained above was heat-melted in a φ30 mm extruder with a cylinder temperature set to 240°C, extruded from a T-die connected to the extruder, and cooled by contacting it with a metal drum whose surface was set to 98°C, to obtain a monolayer film consisting of a 40 μm-thick VDF-based resin layer.

[0071] The haze of the obtained monolayer film was measured before and after stretching in the same manner as for the laminated film. The haze before stretching was 29.0%, and the haze after stretching was 14.0%.

[0072] The results of Comparative Examples 10 and 11 and Reference Example show that although VDF-based resin films do not normally exhibit high haze even when stretched while heated, when they are laminated with AC-based resin films and stretched while heated, the haze does increase. In contrast, the results of Examples 1 to 9 show that by appropriately controlling the microstructure through the addition of TBAHS and optimizing the cooling temperature, it is possible to produce laminated films that do not exhibit high haze even when stretched while heated. [Industrial Applicability]

[0073] The laminated film produced by the present invention has high stretchability, and the transparency of the VDF-based resin film is good even after stretching.

Claims

1. a step of thermally melting a vinylidene fluoride resin composition containing a vinylidene fluoride resin and 0.3 parts by mass or more and 5.0 parts by mass or less of an alkyl quaternary ammonium sulfate per 100 parts by mass of the vinylidene fluoride resin; a step of thermally melting an acrylic resin composition containing an acrylic resin; co-extruding the heat-molten vinylidene fluoride resin composition and the heat-molten acrylic resin composition to form a laminated film; a step of cooling the formed laminated film by contacting it with a cooling roll having a surface temperature of 125°C or less while maintaining the temperature at 150°C or more; A method for producing a decorative laminated film having the above-mentioned features.

2. The acrylic resin is a methacrylic acid ester resin. A method for producing the decorative laminate film according to claim 1.

3. The vinylidene fluoride resin composition contains a vinylidene fluoride resin having an inherent viscosity of 0.80 dL / g or more and 1.20 dL / g or less. A method for producing the decorative laminate film according to claim 1.

4. The alkyl quaternary ammonium sulfate is tetrabutylammonium hydrogen sulfate. A method for producing the decorative laminate film according to claim 1.

5. The melting temperature of the vinylidene fluoride resin composition is 210°C or higher and 260°C or lower. A method for producing the decorative laminate film according to claim 1.

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