Laminated polyester film, laminate, and method for producing laminated polyester film

Abstract

Provided are a laminated polyester film having exceptional adhesiveness and uniformity in application of a water-based coating, a laminate in which the laminated polyester film is used, and a method for producing the laminated polyester film.　This laminated polyester film has an easy-adhesion layer (X) on at least one outermost surface of a polyester substrate, the ratio (γh / γd) of the hydrogen cohesion (γh) and the dispersive force (γd) in energy derived from the surface of the easy-adhesion layer (X) being 0.250 or less.　Additionally, the laminated polyester film according to another embodiment of the present invention has an easy-adhesion layer (X) on at least one outermost surface of a polyester substrate, the lead angle θa of water on the easy-adhesion layer (X) being 75.0-110.0° (inclusive), and the trailing angle θr of water on the easy-adhesion layer (X) being 5.0-40.0° (inclusive).

Description

Laminated polyester film, laminate, and method for producing laminated polyester film

[0001] The present invention relates to a laminated polyester film that is excellent in coating uniformity and adhesion of a water-based coating material, a laminate using the same, and a method for producing the laminated polyester film.

[0002] Thermoplastic resin films, particularly polyester films, have excellent properties such as mechanical properties, electrical properties, dimensional stability, transparency, and chemical resistance, and are therefore widely used in magnetic recording materials, packaging materials, optical films such as antireflection films, diffusion sheets, and prism sheets used in flat displays, etc., transparent touch panels, etc. However, when other materials are coated and laminated onto the polyester film to form a layer having a desired function in order to suitably use it for these applications, there is a drawback in that adhesion is poor depending on the material used.

[0003] Therefore, as a method for imparting adhesiveness to the surface of a polyester film, a method of applying various resins to the surface of the polyester film to provide a coating layer having adhesive properties (an easy-adhesion layer) is known. Specific examples include a method of improving adhesiveness by providing a coating layer made of a polyurethane resin or an acrylic resin or polyester resin having a hydrophilic functional group on the surface of the polyester film (Patent Documents 1, 2, 3, and 4).

[0004] In particular, in recent years, when various functional materials are coated and laminated onto polyester films, water-based coating materials that use water as the main solvent or dispersion medium and reduce organic solvents are often used to reduce environmental impact. On the other hand, the conventional easy-adhesion layer described above not only does not provide sufficient adhesion to such water-based coating materials, but also has the problem of not being able to wet and spread the coating layer sufficiently, resulting in holes in some parts of the layer or uneven thickness, which causes coating repellency.

[0005] To address these issues, as techniques for ensuring adhesion to water-based coating materials, for example, Patent Document 5 proposes a technique for imparting adhesion to water-based inks by blending a water-soluble polymer material into the easy-adhesion layer, and Patent Document 6 proposes a technique for imparting adhesion to hydrophilic adhesives by using a combination of carboxyl group-containing polyurethane and a crosslinking agent.

[0006] JP 2009-214531 A JP 2011-140140 A International Publication WO2014 / 156411 A JP 2008-280421 A JP 2002-234960 A JP 2019-28385 A

[0007] First, the inventors of the present invention verified the adhesion of the technologies of Patent Documents 1 to 4 to water-based coating materials and found that it is difficult to control adhesion to water-based paints simply by changing the functional groups, molecular weight, main chain structure, etc. of the acrylic resin or polyester resin, and that even when the same polyester resin is used, adhesion can change depending on the manufacturing conditions, making it difficult to consistently obtain sufficient adhesion.

[0008] For example, the polyester resin of Patent Document 2, which has substantially no carboxylic acid group, makes it difficult to uniformly apply a water-based coating material. Furthermore, the technology of Patent Document 3 shows a decrease in adhesion due to the presence of acrylic urethane resin. Furthermore, it has become clear that the adhesion of water-based coating materials varies greatly depending on the presence or absence of melamine compounds, even within the same design.

[0009] On the other hand, in the hydrophilic film containing the block copolymer of Patent Document 4, which is designed with a focus on the advancing and receding angles of water, the receding angle is high before deprotection, making it prone to repelling, while after deprotection the advancing angle is low, making it easy to apply water-based coating materials, but it has become clear that sufficient adhesion cannot be obtained.

[0010] On the other hand, with regard to the technology of Patent Document 5, although adhesion with specific ink materials was confirmed, it was found that the water-soluble material was easily dissolved when the water-based coating material was applied, so that it was not possible to wet and spread sufficiently, making it difficult to obtain a uniform coating film, and that transparency was easily lost when a colorless and transparent functional layer was formed, and that blocking, in which the front and back surfaces adhered to each other when the film was rolled up, was likely to occur due to the contribution of moisture in the air. Furthermore, with regard to the technology of Patent Document 6, the challenge was to improve the applicability of water-based coating materials, particularly those with low viscosity.

[0011] Therefore, an object of the present invention is to overcome the above drawbacks and to provide a laminated polyester film, a laminate, and a method for producing a laminated polyester film that are excellent in coating uniformity and adhesion of a water-based coating material.

[0012] The present invention comprises the following configurations.

[0013] [1] A laminated polyester film having an easy-adhesion layer (X) on the outermost surface of at least one side of a polyester substrate, wherein the ratio (γh / γd) of the dispersion force (γd) to the hydrogen bonding force (γh) in the surface free energy of the easy-adhesion layer (X) is 0.250 or less. (Hereinafter, this may be referred to as the "first embodiment.") [2] A laminated polyester film having an easy-adhesion layer (X) on the outermost surface of at least one side of a polyester substrate, wherein the easy-adhesion layer (X) has a water advancing angle θa of 75.0° or more and a water receding angle θr of 5.0° or more and 40.0° or less. (Hereinafter, this may be referred to as the "second embodiment.") [3] The laminated polyester film according to [2] above, having an easy-adhesion layer (X) on the outermost surface of at least one side of the polyester substrate, wherein the ratio (γh / γd) of the dispersion force (γd) to the hydrogen bonding force (γh) in the surface free energy of the easy-adhesion layer (X) is 0.250 or less.

[0014] [4] The laminated polyester film according to any one of [1] to [3], wherein the dispersion force (γd) on the surface of the adhesive layer (X) is 32.0 mN / m or more.

[0015] [5] The laminated polyester film according to any one of [1] to [4], wherein the adhesive layer (X) has an average elastic modulus of 1.0 GPa or more in a 5 μm square area measured by AFM.

[0016] [6] The domain area of ​​the adhesive layer (X) in a 1 μm square elastic modulus variation image measured by AFM is 500 nm ２ The laminated polyester film according to any one of [1] to [5], which is:

[0017] [7] The laminated polyester film according to any one of [1] to [6] above, which has a haze value of 2.0% or less.

[0018] [8] The laminated polyester film according to any one of [1] to [7], wherein the easy-adhesion layer (X) contains at least two kinds of resins or compounds selected from polyester resins, oxazoline compounds, and carbodiimide compounds.

[0019] [9] The laminated polyester film according to any one of [1] to [8], wherein at least one surface of the laminated polyester film satisfies (1) and (2): (1) the average roughness Ra is 1.0 nm or more and 20.0 nm or less, and (2) the 10-point average roughness Rz is 50.0 nm or more and 400.0 nm or less.

[0020]

[10] The laminated polyester film according to any one of [1] to [9], wherein the polyester base material contains at least one of a biomass raw material and a recycled raw material.

[0021]

[11] A laminate having a processing layer (Y) on the surface of the adhesive layer (X) of the laminated polyester film according to any one of [1] to

[10] .

[0022]

[12] The laminate according to

[11] , wherein the processing layer (Y) has a moisture content of 50 wtppm or more.

[0023]

[13] The laminate according to

[11] or

[12] , wherein the processing layer (Y) contains at least one of a hard coating agent, an adhesive, and a printing ink, and also contains a dispersant (D).

[0024]

[14] A method for producing the laminated polyester film according to any one of [1] to

[10] , comprising a step of forming the easy-adhesion layer (X) by thermally curing the coating composition at 170°C or higher.

[0025] According to the present invention, it is possible to provide a laminated polyester film that is particularly excellent in coating uniformity and adhesion of water-based coating materials.

[0026] 1 is an image of the elastic modulus variation on the surface of an easily adhesive layer (X) according to one embodiment of the present invention. 2 is an image of the elastic modulus variation on the surface of a laminated polyester film having a problem to be solved by the present invention.

[0027] Water-based coating materials generally have better environmental compatibility than organic solvent-based coating materials. However, the high surface free energy of the liquid components makes them difficult to wet and spread on many surfaces, including polyester film surfaces. The inventors of the present invention have studied easy-adhesion layers suitable for the application of such water-based coating materials and found that simple control of surface free energy is difficult to explain. By satisfying certain preferred conditions, it is possible to form easy-adhesion layers with improved coatability and adhesion. In other words, in a first aspect, the inventors discovered that wettability and post-dry adhesion can be controlled by controlling the dispersion force (γd) and hydrogen bonding strength (γh) of the surface free energy within specific ranges, leading to the development of the laminated polyester film of the present invention. Details are described below. Hereinafter, the solution or dispersion used to form the easy-adhesion layer (X) of the present invention will be referred to as the "coating composition." Meanwhile, the solution or dispersion applied to form a layer with the desired functionality on the easy-adhesion layer (X) of the laminated polyester film of the present invention will be referred to as the "water-based coating material."

[0028] The laminated polyester film in this first aspect is characterized in that it has an easy-adhesion layer (X) on the outermost surface of at least one side of a polyester base material, and the ratio (γh / γd) of the dispersion force (γd) to the hydrogen bonding force (γh) in the surface free energy of the easy-adhesion layer (X) is 0.250 or less.

[0029] Here, dispersion strength (γd) is a parameter related to the dispersion of water-based coating material components, i.e., wettability and spreadability. The higher its value, the easier it is to ensure the wettability of the water-based coating material. On the other hand, hydrogen bonding strength (γh) is a parameter that indicates the strength of interaction with water molecules. Generally, because water molecules interact more strongly with each other, this value generally increases when using materials that are compatible with water. However, as a result of the inventors' research, it has been discovered that a smaller hydrogen bonding strength (γh) makes it easier to achieve high wettability and adhesion. It is speculated that this is because, on surfaces with high hydrogen bonding strength (γh), the water-based coating material is strongly attracted to the surface, preventing it from sufficiently wettability and spreadability. Several factors, such as material design and manufacturing method, are thought to be factors that increase hydrogen bonding strength (γh), but the two most significant factors are thought to be: A. Limiting the amount of specific water-compatible materials below a certain level; and B. Sufficient progress in the crosslinking reaction of the adhesive layer to suppress the penetration of the water-based coating material. In the following description, the dispersion force (γd) may be simply referred to as dispersion force or γd, and the hydrogen bonding force (γh) may be simply referred to as hydrogen bonding force or γh.

[0030] The laminated polyester film in this first aspect has an easy-adhesion layer (X) on the outermost surface of at least one side of the polyester substrate, and it is important that the ratio (γh / γd) of the dispersion force (γd) and the hydrogen bonding force (γh) in the surface free energy of the easy-adhesion layer (X) is 0.250 or less. By having the γh / γd of the easy-adhesion layer (X) be 0.250 or less, sufficient wettability and adhesion can be achieved at the same time. From the above viewpoint, the γh / γd of the easy-adhesion layer (X) is preferably 0.200 or less, more preferably 0.140 or less, and even more preferably 0.130 or less. When the γh / γd of the easy-adhesion layer (X) exceeds 0.250, it becomes difficult to uniformly blend the water-based coating material into the surface, and as a result, partial peeling tends to occur. On the other hand, the lower limit of the γh / γd of the easy-adhesion layer (X) is not particularly limited, but is 0.001 because theoretically the values ​​of each component do not take negative values ​​and effective measurement accuracy.

[0031] Furthermore, in the laminated polyester film of the present invention, the dispersion force (γd) on the surface of the easy-adhesion layer (X) is preferably 32.0 mN / m or more, more preferably 35.0 mN / m or more. By having the dispersion force (γd) on the surface of the easy-adhesion layer (X) be 32.0 mN / m or more, the effect of spreading the water-based coating material can be sufficiently ensured, and as a result, sufficient coating properties and adhesion can be achieved. Note that there is no preferred value for the upper limit of the dispersion force (γd) of the easy-adhesion layer (X) in terms of characteristics, but from the range that can be practically achieved with the coating composition and manufacturing method preferred for forming the easy-adhesion layer (X) in the laminated polyester film of the present invention, it is 60.0 mN / m.

[0032] The details of the measurement and calculation method of the dispersion force (γd) and hydrogen bond strength (γh) of the easy-adhesion layer (X) will be described later, but this value can be controlled by the constituent components contained in the easy-adhesion layer (X), manufacturing method and their combination.Specifically, it is possible to adjust the wettability of water-based coating material by the functional group species that the resin or compound of the constituent components has in the side chain, the molecular weight of the unit structure when using polymer, the progress of crosslinking reaction etc.Preferred constituent materials and manufacturing method will be described later in detail.

[0033] Furthermore, in a second aspect, the present inventors have found the following characteristic of the easy-adhesion layer (X) that correlates with the preferred range of the surface energy described above. That is, they have found that by controlling the advancing angle of water (advancing contact angle) and the receding angle of water (receding contact angle) of the easy-adhesion layer (X) within specific ranges, it is possible to control the wettability and adhesion after drying. The details are described below.

[0034] The laminated polyester film of the present invention is characterized in that it has an easy-adhesion layer (X) on the outermost surface of at least one side of a polyester base material, and the easy-adhesion layer (X) has a water-advancing angle θa of 75.0° or more and 110.0° or less and a water-receding angle θr of 5.0° or more and 40.0° or less.

[0035] The advancing water angle θa refers to the contact angle in the process of expanding a water droplet when water is continuously supplied to the adhesion layer (X). The receding water angle θr refers to the contact angle in the process of shrinking a water droplet when water is sucked from a water droplet previously formed on the adhesion layer (X). The advancing water angle θa and receding water angle θr of the adhesion layer (X) are measured by the expansion-contraction method, and a contact angle Drop Master DM-501 manufactured by Kyowa Interface Science Co., Ltd. can be used as the measuring device. Details of the measurement method and conditions when using this device are shown in the examples.

[0036] The higher the numerical value of the water advancing angle θa of the easy-adhesion layer (X), the lower the fluidity of the water-based coating agent on the easy-adhesion layer (X). Therefore, by increasing the water advancing angle θa, once the water-based coating agent comes into contact with the easy-adhesion layer (X), it will adhere to the easy-adhesion layer (X), and in the subsequent drying process, it becomes easier to develop good adhesion between the easy-adhesion layer (X) and the layer formed from the water-based coating agent. On the other hand, the lower the numerical value of the water receding angle θr, once the easy-adhesion layer (X) and the water-based coating agent come into contact, the easier it is for the easy-adhesion layer (X) to become wet instantly. Therefore, by lowering the water receding angle θr, the repelling of the water-based coating agent during the drying process is reduced, making it easier to develop good applicability.

[0037] The laminated polyester film of the present invention has an easy-adhesion layer (X) on the outermost surface of at least one side of the polyester substrate, and it is important that the water advancing angle θa of the easy-adhesion layer (X) is 75.0 ° or more and 110.0 ° or less θr. By having the water advancing angle θa of the easy-adhesion layer (X) be 75.0 ° or more and 110.0 ° or less, the fluidity of water on the easy-adhesion layer (X) is suppressed, and good adhesion between the easy-adhesion layer (X) and the water-based coating material can be exhibited. From the above viewpoint, the water advancing angle θa of the easy-adhesion layer (X) is preferably 75.0 ° or more and 100.0 ° or less. When the water advancing angle θa is less than 75.0 °, the flow of the water-based coating material on the easy-adhesion layer (X) increases, and the adhesion between the easy-adhesion layer (X) and the water-based coating material decreases. On the other hand, when the water advancing angle θa is greater than 110.0 °, the water-based coating material is repelled on the easy-adhesion layer (X), and local adhesion deteriorates.

[0038] Furthermore, it is important that the receding water angle θr of the adhesive layer (X) of the laminated polyester film of the present invention is 5.0° or more and 40.0° or less. By having the receding water angle θr of the adhesive layer (X) of 5.0° or more and 40.0° or less, the wettability when water is brought into contact with the adhesive layer (X) is improved, and good applicability between the adhesive layer (X) and the water-based coating material can be achieved. From the above viewpoint, the receding water angle θr of the adhesive layer (X) is preferably 10.0° or more and 30.0° or less. When the receding water angle θr of the water is less than 5.0°, the water droplets used for measurement cannot maintain their shape, and are difficult to evaluate because they fall outside the measurable range. On the other hand, if the receding water angle θr of the adhesive layer (X) is greater than 40.0°, the water-based coating material will be repelled when applied to the adhesive layer (X) or during the subsequent drying process, resulting in localized deterioration of adhesion.

[0039] The water advancing angle θa and water receding angle θr of the easy-adhesion layer (X) can be controlled by the constituent components contained in the easy-adhesion layer (X), the manufacturing method, and a combination thereof. Specifically, the water advancing angle θa and water receding angle θr can be adjusted by the type of functional group on the side chain of the resin or compound that is a constituent of the easy-adhesion layer (X), the molecular weight of the unit structure when a polymer is used, the progress of the crosslinking reaction (which can be increased by thermally curing the coating composition at 170 ° C. or higher), the surface roughness of the polyester substrate and the easy-adhesion layer (X), etc. Then, by adjusting the water advancing angle θa and the water receding angle θr, it is possible to adjust the wettability with respect to water-based coating materials. Details of the preferred constituent materials, coating compositions, and manufacturing methods from the above perspectives will be described later.

[0040] In the present invention, it is preferable that the water advancing angle θa and water receding angle θr of the easy-adhesion layer (X) satisfy the above-mentioned ranges, and that the ratio (γh / γd) of the dispersion force (γd) to the hydrogen bonding force (γh) in the surface free energy of the easy-adhesion layer (X) satisfies the above-mentioned ranges.

[0041] In the present invention, it is preferable that the advancing water angle θa and the receding water angle θr of the easy-adhesion layer (X) satisfy the above ranges, and that the dispersion force (γd) on the surface of the easy-adhesion layer (X) satisfies the above ranges.

[0042] Furthermore, in the present invention, it is preferable that the water advancing angle θa and water receding angle θr of the easy-adhesion layer (X) satisfy the above-mentioned ranges, and that the ratio (γh / γd) of the dispersion force (γd) to the hydrogen bonding force (γh) in the surface free energy of the easy-adhesion layer (X) and the dispersion force (γd) on the surface of the easy-adhesion layer (X) satisfy the above-mentioned ranges.

[0043] Preferred embodiments of the laminated polyester film of the present invention will be described in detail below.

[0044] <Polyester Film> The laminated polyester film of the present invention has an easy-adhesion layer (X) on at least one surface of a polyester substrate. Polyester is a general term for polymers in which an ester bond is the main bonding chain in the main chain, and those containing at least one component selected from ethylene terephthalate, propylene terephthalate, ethylene-2,6-naphthalate, butylene terephthalate, propylene-2,6-naphthalate, ethylene-α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate, etc. as a main component can be preferably used.

[0045] Here, the term "major component" refers to a component unit that is contained in an amount of more than 50 mol% but not more than 100 mol% when all the component units constituting the resin are taken as 100 mol%. It is preferable that the component unit contained in the major component is more than 70 mol%. Furthermore, the term "laminated polyester film" refers to a sheet-like material having at least two layers and containing polyester as the main component. The term "major component" refers to a component that is contained in an amount of more than 50 mass% but not more than 100 mass% of all the component components. The term "polyester substrate" refers to a sheet-like material that constitutes the laminated polyester film and that is mainly composed of polyester. Furthermore, the above-mentioned polyester can contain 30 mol% or less of a copolymer component in all the component components, if necessary.

[0046] As the polyester substrate in the laminated polyester film of the present invention, a polyethylene terephthalate film is preferably used from the viewpoints of heat resistance and smoothness. Furthermore, when the laminated polyester film is subjected to heat, shrinkage stress, or the like, a polyethylene-2,6-naphthalate film, which has excellent heat resistance and rigidity, is preferably used. Here, a polyethylene terephthalate film refers to a film in which polyethylene terephthalate (including copolymers) accounts for more than 50% by mass and not more than 100% by mass of all components constituting the film, and the same can be said for a polyethylene-2,6-naphthalate film.

[0047] From the viewpoints of thermal stability and mechanical strength, the polyester substrate is preferably biaxially oriented. A biaxially oriented polyester film is a polyester film that exhibits a pattern of orientation along two orthogonal axes in wide-angle X-ray diffraction. Generally, biaxially oriented polyester films are obtained by stretching an unstretched polyester sheet in two orthogonal directions. For example, the film is stretched approximately 2.5 to 5.0 times in each of the longitudinal and width directions, and then heat-treated to complete the crystal orientation. Using a biaxially oriented polyester film as the polyester substrate improves the thermal stability, particularly the dimensional stability and mechanical strength, of the laminated polyester film, as well as its flatness. Here, the longitudinal direction refers to the direction in which the film runs during the manufacturing process (equivalent to the winding direction of the film in a film roll), and the width direction refers to the direction perpendicular to the longitudinal direction within the film plane.

[0048] The polyester substrate may also contain various additives, such as antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents, and nucleating agents, to the extent that they do not deteriorate the properties of the polyester substrate.

[0049] The thickness of the polyester substrate is not particularly limited and may be appropriately selected depending on the application and type, but is usually preferably 10 to 500 μm, more preferably 20 to 250 μm, and particularly preferably 30 to 150 μm, from the viewpoints of mechanical strength, handleability, etc. The polyester substrate may be a composite film obtained by coextrusion, or may be a film obtained by laminating obtained films by various methods.

[0050] The laminated polyester film of the present invention preferably has a total light transmittance of 88% or more, more preferably 90% or more. Since the laminated polyester film has a total light transmittance of 88% or more, it can be suitably used as an optical film such as an easy-adhesion film for a prism. Furthermore, since the upper limit of the substantial total light transmittance of a polyester film is 94%, it is preferably 88% or more but less than 94%.

[0051] The total light transmittance of the laminated polyester film can be measured using a measuring device in accordance with JIS "Determination of Haze of Transparent Materials" (K7136, 2000 edition). Methods for making the total light transmittance of the laminated polyester film 88% or more include, for example, improving the flatness by the above-mentioned biaxial stretching, and forming a smooth coating layer on the outermost surface of the laminated polyester film to reduce the reflectance with the air layer.

[0052] Furthermore, the laminated polyester film of the present invention preferably has a haze value of 2.0% or less, particularly preferably 1.0% or less. By setting the haze value of the laminated polyester film within the above range, transparency is increased, making it suitable for use in optical films that require transparency. The lower the haze value, the better, and there is no particular lower limit, but from the perspective of feasibility, the lower limit is 0.1%. The haze value is sometimes called "haze."

[0053] The haze value of the laminated polyester film can be measured by a method conforming to JIS "Method for Determining Haze of Transparent Materials" (K7136 2000 edition), and details thereof are shown in the Examples. Furthermore, a method for making the haze value of the laminated polyester film 2.0% or less can be exemplified by a method for reducing the reflectance at the interface with air by adjusting the surface shape or refractive index of a coating layer formed on the outermost surface of the polyester film.

[0054] <Easy-Adhesion Layer (X)> The laminated polyester film of the present invention has an easy-adhesion layer (X) on the outermost surface of at least one side of the polyester substrate. Here, when another layer (a post-processing layer, corresponding to the processing layer (Y) described below) is formed by post-processing, the easy-adhesion layer (X) is located between the polyester substrate and the post-processing layer, and plays a role in improving the adhesion between them. The easy-adhesion layer (X) satisfies at least one of the following on the surface of the easy-adhesion layer (X): "the ratio (γh / γd) of the dispersion force (γd) to the hydrogen bonding force (γh) is 0.250 or less" and "the water advancing angle θa is 75.0° or more and 110.0° or less, and the water receding angle θr is 5.0° or more and 40.0° or less." Preferably, both are satisfied. The definitions of each parameter are as described above.

[0055] From the viewpoint that the easy-adhesion layer (X) plays such a role, in the laminated polyester film of the present invention, at least one outermost surface of the polyester substrate, preferably one outermost surface, becomes the easy-adhesion layer (X).By adopting such an embodiment, when the polyester substrate and the post-processing layer are laminated via the easy-adhesion layer (X), it becomes easy to handle the laminate as an integrated laminate.In addition, the easy-adhesion layer (X) can be designed in consideration of the applicability and adhesion of the water-based coating material (details will be described later).

[0056] The thickness of the easy-adhesion layer (X) (coating thickness after drying) is preferably 10 to 200 nm, more preferably 40 to 150 nm. A coating thickness of 10 nm or more can sufficiently ensure the above-mentioned adhesion. On the other hand, a thickness of the easy-adhesion layer (X) of 200 nm or less makes it easy to maintain high appearance quality, such as transparency. The thickness of the easy-adhesion layer (X) can be measured by observing a cross section in a direction perpendicular to the film surface (thickness direction) using a transmission electron microscope (TEM).

[0057] In the laminated polyester film of the present invention, from the viewpoint of improving coatability and adhesion, the average modulus of elasticity of the easy-adhesion layer (X) measured by AFM (Atomic Force Microscope) in a 5 μm square area is preferably 1.0 GPa or more, more preferably 1.5 GPa or more, and particularly preferably 2.0 GPa or more (hereinafter, the "average modulus of elasticity of 5 μm square measured by AFM" may be referred to as the average modulus.). By having the average modulus of elasticity of the easy-adhesion layer (X) be 1.0 GPa or more, the crosslinking reaction proceeds sufficiently when forming the easy-adhesion layer (X) from the coating composition, and the effect of suppressing the penetration of the water-based coating material is sufficiently obtained, thereby promoting the wetting and spreading of water on the surface, and as a result, particularly improving coatability. On the other hand, there is no particular restriction on the upper limit of the average modulus of elasticity of the easy-adhesion layer (X), but from the perspective of the achievability of the preferred coating composition and manufacturing method of the present invention, it is 20 GPa as a realistic range.

[0058] The average elastic modulus can be measured and calculated by a force curve method using an AFM followed by analysis based on the JKR contact theory, and detailed methods and conditions are shown in the Examples. Furthermore, an example of a method for making the average elastic modulus 1.0 GPa or more is to form a resin layer with a higher crosslink density on the outermost surface of the laminated polyester film by coating or the like.

[0059] Furthermore, there is a preferred form in the elastic modulus distribution of 1 μm square measured by AFM (Atomic Force Microscope). Specifically, there is a preferred form in the "elastic modulus variation image" obtained by smoothing the elastic modulus image (i.e., DMT Modulus channel data) measured by the measurement method described below in the Flatten mode of the analysis software "NanoScopeAnalysis V1.40" at Order: 3rd and offsetting the average value to 0 MPa. Specifically, in the above-mentioned "elastic modulus variation image", it is preferable that the elastic modulus variation width is small, and it does not have coarse domains. This is particularly preferable in order to maintain the coatability and adhesion of the easy-adhesion layer (X) surface uniformly and to stably express the properties.

[0060] FIG. 1 is an image of the elastic modulus variation on the surface of an easy-adhesion layer (X) according to one embodiment of the present invention. Specifically, it is an image of the elastic modulus variation on the surface of an easy-adhesion layer (X) of a laminated polyester film prepared in Example 1 as an example of a preferred form of an "elastic modulus variation image." FIG. 2 shows an "elastic modulus variation image" of a commercially available conventional laminated polyester film for comparison. The black areas in the "elastic modulus variation image" (representative black areas in the elastic modulus variation image 1 in FIGS. 1 and 2) represent areas with relatively low elastic modulus, and the white areas (representative white areas in the elastic modulus variation image 2 in FIGS. 1 and 2) represent areas with relatively high elastic modulus. Each domain in the elastic modulus variation image is formed by localized aggregation of the binder resin or reactive compound used. When the domains become coarse as shown in FIG. 2, i.e., when aggregation of the constituent materials is observed, the applicability and adhesion of the aqueous coating to the easy-adhesion layer (X) tends to decrease.

[0061] The variation width of the elastic modulus corresponds to the Image Rmax obtained by analyzing the above-mentioned "elastic modulus variation image" in Roughness mode, and is preferably less than 5 GPa, particularly preferably less than 2 GPa. On the other hand, the size of the coarse domain is expressed as the average area of ​​each domain colored at Bearing Area Percent: 10% in Bearing Analysis mode, and is 500 nm ２ Preferably, it is 300 nm or less. ２More preferably, it is 100 nm or less. ２ It is particularly preferable that the following conditions are satisfied: The details of the method for measuring the variation width of the elastic modulus and the domain area will be described later.

[0062] In the laminated polyester film of the present invention, there are preferred ranges for the average roughness Ra and 10-point average roughness of each surface from the viewpoints of controlling the water advancing angle θa and water receding angle θr of the adhesive layer (X) and of improving lubricity and blocking resistance. Specifically, from the viewpoints of improving lubricity and blocking resistance, it is preferable that at least one surface satisfies (1) and (2). Furthermore, from the viewpoint of controlling the water advancing angle θa and water receding angle θr of the adhesive layer (X), it is preferable that the surface of the adhesive layer (X) satisfies (1) and (2). (1) The average roughness Ra is 1.0 nm or more and 20.0 nm or less. (2) The 10-point average roughness Rz is 50.0 nm or more and 400.0 nm or less.

[0063] From the viewpoint of easy sliding property and blocking resistance, the average roughness Ra of at least one surface is more preferably 3.0 nm to 10.0 nm, and the 10-point average roughness Rz is more preferably 100.0 nm to 250.0 nm. By making the average roughness Ra of at least one surface 1.0 nm or more or making the 10-point average roughness Rz 50.0 nm or more, blocking resistance can be imparted to the laminated polyester film. On the other hand, by making the average roughness Ra 20.0 nm or less or making the 10-point average roughness Rz 400.0 nm or less, particle detachment and deterioration of appearance can be reduced.

[0064] From the viewpoint of suitably controlling the water advancing angle θa and water receding angle θr of the adhesion layer (X), the average roughness Ra of the surface of the adhesion layer (X) is more preferably 3.0 nm or more and 10.0 nm or less, and the 10-point average roughness Rz is more preferably 100.0 nm or more and 250.0 nm or less. By making the average roughness Ra of the surface of the adhesion layer (X) 1.0 nm or more, the surface area of ​​the adhesion layer (X) is appropriately increased, so that even when a coating composition is used in which the water advancing angle θa and the water receding angle θr do not fall within the desired range on a smooth surface, it may be possible to control the water advancing angle θa and the water receding angle θr within the desired range, and the adhesion layer (X) can also be imparted with slipperiness and abrasion resistance. Furthermore, by making the 10-point average roughness Rz of the adhesion layer (X) 50.0 nm or more, blocking resistance can be imparted to the laminated polyester film. On the other hand, by making the average roughness Ra of the easy-adhesion layer (X) 20.0 nm or less and making the 10-point average roughness Rz 400.0 nm or less, it is possible to reduce particle dropping and deterioration of appearance.

[0065] <Coating Composition> Here, a preferred coating composition for forming the easy-adhesion layer (X) of the laminated polyester film of the present invention will be described. The easy-adhesion layer (X) of the laminated polyester film of the present invention is preferably formed from a coating composition containing various binder resins (A) such as polyester resins, urethane resins, and acrylic resins, and a reactive compound (B) selected from oxazoline compounds and carbodiimide compounds, and more preferably contains at least two components selected from polyester resins, oxazoline compounds, and carbodiimide compounds. That is, the easy-adhesion layer (X) of the laminated polyester film of the present invention more preferably contains at least two components selected from polyester resins, oxazoline compounds, and carbodiimide compounds. The type and content of each component constituting the coating composition are selected so that the easy-adhesion layer (X) formed using the coating composition satisfies at least one of the following conditions on the surface of the easy-adhesion layer (X) specified in the present invention: "the ratio (γh / γd) of the dispersion force (γd) to the hydrogen bonding force (γh) is 0.250 or less" and "the advancing angle θa of water is 75.0° or more and 110.0° or less, and the receding angle θr of water is 5.0° or more and 40.0° or less."

[0066] Here, the embodiment "containing at least two components selected from a polyester resin, an oxazoline compound, and a carbodiimide compound" refers to an embodiment containing a polyester resin and an oxazoline compound, an embodiment containing a polyester resin and a carbodiimide compound, an embodiment containing an oxazoline compound and a carbodiimide compound, and an embodiment containing all of a polyester resin, an oxazoline compound, and a carbodiimide compound. Even if a composition contains multiple components, if all of these components fall into the same category (e.g., a composition containing multiple oxazoline compounds but not a polyester resin or a carbodiimide compound), this is not considered to fall under the embodiment "containing at least two components selected from a polyester resin, an oxazoline compound, and a carbodiimide compound." It should be noted that the above requirement can also be satisfied when a polyester resin reacts with an oxazoline compound or a carbodiimide compound to form a new chemical structure. In the above, when two types of reactive compounds (B), an oxazoline compound and a carbodiimide compound, are selected, the adhesive layer (X) may be composed only of a resin obtained by a crosslinking reaction of the reactive compound (B), or may further contain a binder resin (A). When the binder resin (A) is used in combination, a preferred embodiment is one in which the two types of reactive compounds (B) and the binder resin other than the polyester resin are selected so as to fall within the ranges specified in the present invention to form a coating composition.

[0067] <Binder resin (A)> As the binder resin (A) forming the easy-adhesion layer (X) in the laminated polyester film of the present invention, the above-mentioned surface free energy parameter γh / γd is 0.250 or less, and / or the water advancing angle θa is 75.0 ° or more and 110.0 ° or less, and the water receding angle θr is 5.0 ° or more and 40.0 ° or less, any material can be used, for example, polyester resin, acrylic resin, urethane resin, epoxy resin, etc., can be used alone or in combination with a plurality of types, so as to satisfy the above range. On the other hand, from the viewpoint of adjusting the compatibility with water-based coating materials, it is particularly preferable to use polyester resin.

[0068] As the dicarboxylic acid component serving as a raw material for the polyester resin, aromatic, aliphatic, and alicyclic dicarboxylic acids can be used. Examples of aromatic dicarboxylic acids that can be used include terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 2,5-dimethylterephthalic acid, 1,4-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2-bisphenoxyethane-pp'-dicarboxylic acid, and phenylindanedicarboxylic acid. Examples of aliphatic and alicyclic dicarboxylic acids that can be used include succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, dimer acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid, as well as ester-forming derivatives thereof.

[0069] Diol components that are raw materials for polyester resins include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl- 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 4,4'-thiodiphenol, bisphenol A, 4,4'-methylenediphenol, 4,4'-(2-norbornylidene)diphenol, 4,4'-dihydroxybiphenol, o-, m-, and p-dihydroxybenzene, 4,4'-isopropylidenephenol, 4,4'-isopropylidenebindiol, cyclopentane-1,2-diol, cyclohexane-1,2'-diol, cyclohexane-1,2-diol, cyclohexane-1,4-diol, and the like can be used.

[0070] As the polyester resin, it is also possible to use modified polyester copolymers, such as block copolymers and graft copolymers modified with acrylic, urethane, epoxy, or the like.

[0071] It is particularly preferable that the polyester resin has a functional group in the side chain, from the viewpoint of forming a dense coating film by a crosslinking reaction with the reactive compound (B) described below and optimally adjusting the ratio (γh / γd) of the dispersion force (γd) to the hydrogen bonding force (γh) in the surface free energy, as well as the advancing water angle θa and the receding water angle θr. Examples of functional groups include hydroxyl groups, carboxylic acid groups, amide groups, glycidyl groups, isocyanate groups, and sulfonic acid groups. The amount of functional groups can be determined by selecting the acid value or hydroxyl value as a representative value. For example, if the acid value of the polyester resin is less than 5 KOH / mg, the coatability and adhesion of the water-based coating material may be reduced.

[0072] The acrylic resin is not particularly limited, but is preferably composed of alkyl methacrylate and / or alkyl acrylate.

[0073] The alkyl methacrylate and / or alkyl acrylate preferably includes methacrylic acid, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, acrylic acid, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, maleic acid, itaconic acid, acrylamide, N-methylolacrylamide, diacetone acrylamide, etc. These may be used alone or in combination of two or more.

[0074] Since the acrylic resin is a hydrophobic resin, it is considered to contribute to increasing the dispersion force (γd) of the adhesive layer (X), the advancing angle θa of water, and the receding angle θ of water, although it is also affected by the structure of the side chain.

[0075] The urethane resin is preferably a resin obtained by reacting a polyhydroxy compound with a polyisocyanate compound by a known urethane resin polymerization method such as emulsion polymerization or suspension polymerization.

[0076] Examples of polyhydroxy compounds include polyethylene glycol, polypropylene glycol, polyethylene-propylene glycol, polytetramethylene glycol, hexamethylene glycol, tetramethylene glycol, 1,5-pentanediol, diethylene glycol, triethylene glycol, polycaprolactone, polyhexamethylene adipate, polyhexamethylene sebacate, polytetramethylene adipate, polytetramethylene sebacate, trimethylolpropane, trimethylolethane, pentaerythritol, polycarbonate diol, glycerin, etc. Examples of polyisocyanate compounds that can be used include hexamethylene diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate, an adduct of tolylene diisocyanate and trimethylenepropane, an adduct of hexamethylene diisocyanate and trimethylolethane, etc.

[0077] The above-mentioned urethane resins and their copolymers (e.g., acrylic-urethane copolymers and urethane-modified polyesters) have highly hydrophilic crosslinked structures, and therefore, when added in excess, the hydrogen bonding strength (γh) of the present invention tends to increase. Although the specific upper limit of the amount added is affected by the combination with other binder resins, if the amount of urethane resin added exceeds 5% by mass of the total binder resin, adhesion may be affected.

[0078] As the epoxy resin, for example, a sorbitol polyglycidyl ether crosslinking agent, a polyglycerol polyglycidyl ether crosslinking agent, a diglycerol polyglycidyl ether crosslinking agent, a polyethylene glycol diglycidyl ether crosslinking agent, or the like can be used. As the epoxy resin, commercially available epoxy resins may be used. For example, epoxy compounds "Denacol" (registered trademark) EX-611, EX-614, EX-614B, EX-512, EX-521, EX-421, EX-313, EX-810, EX-830, EX-850, etc., manufactured by Nagase Chemtec Corporation; diepoxy / polyepoxy compounds (SR-EG, SR-8EG, SR-GLG, etc.) manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.; and epoxy crosslinking agents "EPICLON" (registered trademark) EM-85-75W or CR-5L, manufactured by Dainippon Ink Mfg. Co., Ltd., can be suitably used. Among these, water-soluble epoxy resins are preferably used.

[0079] Since the above-mentioned epoxy resin is a hydrophilic resin, it is thought that, although it is also affected by the structure of the side chain, it increases the hydrogen bonding strength (γh) of the easy-adhesion layer (X) and contributes to reducing the water advancing angle θa and the water receding angle θr.

[0080] <Reactive compound (B)> The adhesive layer (X) of the present invention preferably contains a reactive compound (B), particularly from the viewpoint of sufficiently promoting the crosslinking reaction of the adhesive layer and suppressing the penetration of water-based coating materials.As the reactive compound (B), any compound such as an oxazoline compound, a carbodiimide compound, a melamine compound, an isocyanate compound and a combination thereof can be used to satisfy the range specified in the present invention, but from the viewpoint of designing the above-mentioned surface free energy and / or the advancing angle θa of water, the receding angle θr of water, it is preferable to use an oxazoline compound, a carbodiimide compound alone or in combination to be configured to be within the range specified in the present invention.In addition, the reactive compound (B) forms a separate chemical structure derived from the compound between the resin component by crosslinking reaction etc., and even if the reactive compound (B) does not exist in the adhesive layer (X) as a single substance, it can be interpreted that the adhesive layer (X) contains a reactive compound (B).

[0081] The oxazoline compound is preferably one having an oxazoline group as a functional group therein, and is preferably an oxazoline group-containing copolymer obtained by copolymerizing at least one monomer containing an oxazoline group and at least one other monomer.

[0082] In the oxazoline compound, at least one other monomer used for the monomer containing an oxazoline group is a monomer copolymerizable with the monomer containing an oxazoline group, and examples thereof include acrylic acid esters or methacrylic acid esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, and 2-ethylhexyl methacrylate; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, and maleic acid; unsaturated nitriles such as acrylonitrile and methacrylonitrile; Examples of suitable monomers that can be used include unsaturated amides such as vinyl esters, acrylamide, methacrylamide, N-methylol acrylamide, and N-methylol methacrylamide; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; olefins such as ethylene and propylene; halogen-containing α,β-unsaturated monomers such as vinyl chloride, vinylidene chloride, and vinyl fluoride; and α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene. These may be used alone or in combination as long as the scope of the present invention is met.

[0083] Specific oxazoline compounds are not particularly limited, but addition-polymerizable oxazoline group-containing monomers are preferred, and examples thereof include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. These may be used alone or in combination as long as they satisfy the scope of the present invention.

[0084] The carbodiimide compound is a compound having at least one carbodiimide group or a cyanamide group, which is a tautomeric form of the carbodiimide group, as a functional group in the molecule. Specific examples of such carbodiimide compounds include dicyclohexylmethanecarbodiimide, dicyclohexylcarbodiimide, tetramethylxylylenecarbodiimide, and urea-modified carbodiimide. These may be used alone or in combination as long as they satisfy the scope of the present invention.

[0085] The melamine compound that can be used in the laminated polyester film of the present invention is a melamine compound having one or more triazine rings and one or more methylol groups in one molecule. By using such a melamine compound, a crosslinked structure between methylol groups can be formed in the adhesive layer (X).

[0086] Examples of melamine compounds that can be used include melamine, methylolated melamine derivatives obtained by condensing melamine with formaldehyde, compounds obtained by reacting methylolated melamine with a lower alcohol to partially or completely etherify the melamine, and mixtures thereof. The melamine compound may be a condensate of a monomer or a dimer or higher polymer, or a mixture thereof. Examples of lower alcohols used for etherification include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, and isobutanol. The functional group may be an imino group, a methylol group, or an alkoxymethyl group such as a methoxymethyl group or a butoxymethyl group per molecule. Examples of such functional groups include imino-type methylated melamine compounds, methylol-type melamine compounds, methylol-type methylated melamine compounds, and fully alkylated methylated melamine compounds. In particular, examples of methylol melamine compounds include monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, and hexamethylol melamine. These may be used alone or in combination as long as they satisfy the scope of the present invention.

[0087] Since melamine compounds are materials that are compatible with water, when the coating composition contains a melamine compound, the content is preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less, per 100 parts by mass of the binder resin (A). By having the melamine compound content be 10 parts by mass or less per 100 parts by mass of the binder resin (A), the applicability of the water-based coating material is improved.

[0088] <Method for preparing coating composition> When preparing a coating composition, a solvent or a dispersion medium (hereinafter collectively referred to as solvent) may be contained. That is, various components may be dissolved or dispersed in a solvent to form a coating composition, which may then be applied to a polyester substrate. When such a method is adopted, a laminated polyester film in which an easy-adhesion layer (X) is laminated on a polyester substrate can be obtained by drying the solvent after application and heating.

[0089] In the laminated polyester film of the present invention, it is preferable to use an aqueous solvent (C) as the solvent. Here, the aqueous solvent (C) refers to a mixture of water or water and a water-soluble organic solvent, such as an alcohol (e.g., methanol, ethanol, isopropyl alcohol, butanol), a ketone (e.g., acetone, methyl ethyl ketone), or a glycol (e.g., ethylene glycol, diethylene glycol, propylene glycol), in any ratio. The use of an aqueous solvent not only prevents the solvent from rapidly evaporating during the heating step, allowing for the formation of a more uniform adhesive layer (X), but also provides an advantage in terms of environmental impact.

[0090] In the present invention, a preferred coating composition for forming the easy-adhesion layer (X) can be prepared by mixing and stirring the binder resin (A), reactive compound (B), and aqueous solvent (C) as needed, which are water-dispersed or water-soluble, in any order at a desired mass ratio. Next, various additives such as lubricants, inorganic particles, organic particles, surfactants, antioxidants, and thermal initiators can be added as needed, in any order, so long as they do not deteriorate the properties of the easy-adhesion layer (X) formed by the coating composition. The mixing and stirring method can be, for example, shaking the container by hand, stirring with a magnetic stirrer or stirring blade, or using ultrasonic irradiation, vibration dispersion, etc.

[0091] Examples of particles that can be used include inorganic particles such as colloidal silica, titanium oxide, aluminum oxide, zirconium oxide, calcium carbonate, carbon black, and zeolite particles, and organic particles such as acrylic particles, silicone particles, polyimide particles, Teflon® particles, crosslinked polyester particles, crosslinked polystyrene particles, crosslinked polymer particles, and core-shell particles. These may be used alone or in combination. Among these, inorganic particles are preferred, and colloidal silica is more preferred, from the viewpoints of hardness for achieving the blocking suppression effect and thermal stability in a preferred manufacturing method for the laminated polyester film. When the above-mentioned colloidal silica is used as the inorganic particles, the inorganic particles are well dispersed in the adhesion layer (X), and the average roughness Ra of the adhesion layer (X) can easily be set to 20 nm or less. Suitable colloidal silicas include, for example, the "Snowtex"® series manufactured by Nissan Chemical Industries, Ltd. and the "Cataloid®" series manufactured by JGC Catalysts and Chemicals Co., Ltd.

[0092] The number-average particle size of these particles is preferably in the range of 30 nm to 1000 nm. Here, the number-average particle size is the sum of the particle sizes of primary particles, defined in JIS H7008 (2002) as particles generated by the growth of a single crystal nucleus, divided by the number (number average). The number-average particle size of the particles is more preferably in the range of 80 nm to 450 nm, and even more preferably in the range of 100 nm to 300 nm. The particles may be monodisperse particles or agglomerated particles formed by agglomeration of multiple particles. In some cases, multiple types of particles with different number-average particle sizes may be used in combination. The number-average particle size of the particles can be measured by particle size distribution analysis using dynamic light scattering in the case of a coating composition, or by shape analysis using SEM-EDX in the case of a laminated polyester film.

[0093] In addition, in the present invention, a preferred coating composition for forming the easy-adhesion layer (X) specifically contains at least two types of resins or compounds selected from polyester resins, oxazoline compounds, and carbodiimide compounds. By satisfying the above combination, it becomes easier to control the γh / γd and / or water advancing angle θa and water receding angle θr of the easy-adhesion layer (X) formed within the above-mentioned range, and the applicability and adhesion of the water-based coating material are improved.

[0094] <Method for producing laminated polyester film> The method for forming the easy-adhesion layer (X) of the present invention is preferably a method comprising the steps of applying the above-mentioned preferred coating composition to at least one surface of a polyester substrate and heating the coating composition to form the easy-adhesion layer (X). In this formation method, the coating composition may contain various binder resins (A) such as polyester resins, urethane resins, and acrylic resins, at least one compound (B) selected from melamine compounds, oxazoline compounds, and carbodiimide compounds, and various additives such as a crosslinking catalyst, a lubricant, inorganic particles, organic particles, a surfactant, an antioxidant, and a thermal initiator.

[0095] The coating composition can be applied to a polyester substrate by either an in-line coating method or an off-coating method, but the in-line coating method is preferred. The in-line coating method is a method in which the coating composition is applied during the manufacturing process of a polyester substrate (polyester film). Specifically, it refers to a method in which the coating is applied at any stage from melt extrusion of a polyester resin to biaxially stretching, followed by heat treatment and winding up. Typically, the coating is applied to either a substantially amorphous unstretched (unoriented) polyester film obtained by melt extrusion and quenching (hereinafter sometimes referred to as A film), a uniaxially stretched (uniaxially oriented) polyester film (hereinafter sometimes referred to as B film) that has been subsequently stretched in the longitudinal direction, or a biaxially stretched (biaxially oriented) polyester film (hereinafter sometimes referred to as C film) that has been further stretched in the width direction and before heat treatment.

[0096] In the present invention, a preferred method is to apply a coating composition to either the A film or the B film of a polyester film before the crystal orientation is complete, evaporate the solvent, and then stretch the polyester film uniaxially or biaxially and heat it to complete the crystal orientation of the polyester film, thereby providing an easy-adhesion layer (X). This method allows the production of a polyester film (corresponding to the polyester substrate of the laminated polyester film of the present invention), the application of the coating composition, the drying of the solvent, and heating (i.e., the formation of the easy-adhesion layer (X)) to be carried out in a continuous process. In particular, when coating is carried out on the B film, the heat treatment process (thermal setting) after stretching the polyester film in the width direction, and the drying and heating of the coating composition (i.e., the formation of the easy-adhesion layer (X) by heat curing) can be carried out in the same process. This not only has advantages in terms of production cost, but also allows the coating layer to be subjected to high-temperature heat treatment while reducing deformation and thermal shrinkage of the substrate by completing the crystal orientation of the polyester substrate after drying. As a result, crosslinking of the adhesive layer (X) formed by coating is promoted, and coating unevenness due to penetration is less likely to occur when an aqueous functional material is coated.Furthermore, there is also an advantage that the thickness of the adhesive layer (X) can be easily made thinner and more uniform by stretching it after coating.

[0097] In addition, there are preferable temperature conditions for the heat treatment (thermal curing) of the coating layer from the viewpoint of sufficiently promoting the crosslinking reaction of the aforementioned easy-adhesion layer (X) and suppressing the penetration of the water-based coating material.Specifically, the heat treatment temperature is preferably 170 ° C or higher to form the easy-adhesion layer (X), and the heat curing temperature is more preferably 180 ° C or higher, even more preferably 200 ° C or higher, and particularly preferably 230 ° C or higher.In addition, the upper limit of the heat treatment temperature is preferably 260 ° C from the heat resistance temperature of the polyester film.By setting the heat treatment temperature to 260 ° C or lower, deformation of the polyester film is suppressed, making it easier to obtain a more uniform laminated polyester film.

[0098] Among these, a method in which a coating composition is applied to a film (film B) uniaxially stretched in the longitudinal direction, the solvent is dried, and then the film is stretched in the width direction and heated is excellent. This is because, compared with a method in which a coating composition is applied to an unstretched film and then biaxially stretched, this method requires one less stretching step for the layer formed from the coating composition, making it less likely for defects or cracks to occur in the easy-adhesion layer (X) due to stretching, and making it possible to form an easy-adhesion layer (X) with excellent transparency and smoothness.

[0099] On the other hand, the offline coating method is a method in which the above-mentioned A film is stretched uniaxially or biaxially, and subjected to heat treatment to complete the crystal orientation of the polyester film, or the A film itself, is coated with a coating composition in a process separate from the film production process. In the present invention, from the various advantages described above, it is preferable to use the in-line coating method. However, even when the easy-adhesion layer (X) is formed by the offline coating method, the processing temperature is preferably 170 ° C or higher, more preferably 180 ° C or higher, and even more preferably 200 ° C or higher. By setting the processing temperature to 170 ° C or higher, the crosslinking reaction can be promoted and the thin-film easy-adhesion layer (X) can be sufficiently cured.

[0100] In particular, from the viewpoint of sufficiently promoting the crosslinking reaction of the aforementioned easy-adhesion layer (X) to suppress the penetration of the water-based coating material, even when the same formulation is used, it may be impossible to control γh / γd and the water receding angle θr within the above-mentioned range unless the processing temperature is 170 ° C. or higher. Note that the upper limit of the processing temperature is preferably 260 ° C. from the heat resistance temperature of the polyester film. By setting the processing temperature to 260 ° C. or less, deformation of the polyester film is suppressed, making it easier to obtain a uniform laminated polyester film.

[0101] Here, the coating method for the coating composition on the polyester film can be any method selected from known coating methods, such as bar coating, reverse coating, gravure coating, die coating, blade coating, etc., for both in-line coating and offline coating.

[0102] Therefore, a preferred method for forming the easy-adhesion layer (X) in the present invention is a method in which a coating composition using an aqueous solvent is applied to a polyester substrate using an in-line coating method, followed by drying and heat treatment. A more preferred method is a method in which the coating composition is in-line coated onto the uniaxially stretched B film. In the method for producing the laminated polyester film of the present invention, drying is preferably carried out at a temperature range of 80 to 130°C to complete removal of the solvent from the coating composition. Furthermore, heat treatment is preferably carried out at a temperature range of 170 to 260°C to complete the crystal orientation of the polyester film and the thermal curing of the coating composition, thereby completing the formation of the easy-adhesion layer (X).

[0103] Next, the method for producing the laminated polyester film of the present invention will be explained in more detail using an example in which a polyethylene terephthalate (hereinafter, PET) film is used as the polyester substrate, but the laminated polyester film of the present invention and its production method are not limited to this.

[0104] First, PET pellets are thoroughly vacuum-dried, then fed into an extruder, melt-extruded into a sheet at 260°C to 280°C, and cooled to solidify, producing an unstretched (unoriented) PET film (Film A). (In this case, the melt-extruded sheet is preferably cooled and solidified using a cast drum at a temperature of 10°C to 40°C.) This unstretched PET film is stretched 2.5 to 5.0 times in the longitudinal direction using a roll heated to 80 to 120°C to produce a uniaxially oriented PET film (Film B). Furthermore, the aforementioned coating composition, prepared to a predetermined concentration, is applied to one side of Film B.

[0105] In this case, the surface of the uniaxially oriented PET film to be coated may be subjected to a surface treatment such as corona discharge treatment before applying the coating composition. Surface treatment such as corona discharge treatment improves the wettability of the coating composition to the uniaxially oriented PET film, preventing repellency of the coating composition and allowing the formation of an easily adherent layer (X) with a more uniform coating thickness. After applying the coating composition, the edges of the uniaxially oriented PET film are held with clips, and the solvent of the coating composition is dried in a heat treatment zone (preheating zone) at 80 to 130°C. In particular, when sending the uniaxially oriented PET film coated with the coating composition to the heat treatment zone, it is preferable to hold the uncoated portions of both widthwise ends of the uniaxially oriented PET film with clips and guide it to a tenter. After drying, the film is stretched widthwise by 1.1 to 5.0 times, and subsequently introduced into a heat treatment zone (thermal setting zone) at 170 to 260°C, where it is heat-treated for 1 to 30 seconds to complete the crystal orientation.

[0106] During this heat treatment process (thermal setting process), a relaxation treatment of 3 to 15% may be performed in the width direction or longitudinal direction as needed. The laminated polyester film is then cooled to room temperature and cut parallel to the longitudinal direction with a known razor blade or the like to remove the uncoated portions at both ends of the width direction that were gripped by the clips, and the film can then be wound into a roll. The resulting laminated polyester film exhibits excellent applicability, adhesion, and transparency for water-based coating materials. The uncoated portions of the film at both ends of the width direction cut and removed with a slitter can be used as recycled raw materials, as described below.

[0107] In the laminated polyester film of the present invention, an intermediate layer may be provided between the easy-adhesion layer (X) and the polyester base material, but when an intermediate layer is provided, the film may be scratched when the film having the intermediate layer laminated thereon is taken up or in the subsequent process up to the provision of the easy-adhesion layer (X) of the present invention. Therefore, in the present invention, it is preferable that the easy-adhesion layer (X) and the polyester base material are directly laminated.

[0108] The polyester base material constituting the laminated polyester film of the present invention is not limited in its layer configuration, and examples thereof include a single-layer configuration consisting of only Layer A, a laminate configuration of Layer A / Layer B, i.e., a two-type two-layer laminate configuration, a laminate configuration of Layer A / Layer B / Layer A, i.e., a two-type three-layer laminate configuration, and a laminate configuration of Layer A / Layer B / Layer C, i.e., a three-type three-layer laminate configuration.

[0109] The lamination method for the polyester substrate constituting the laminated polyester film of the present invention is not limited, and examples thereof include a lamination method using a coextrusion method, a lamination method using lamination, and a combination thereof. However, from the viewpoints of transparency and manufacturing stability, it is preferable to adopt a coextrusion method. When forming a laminate, different resin structures may be used to impart different functions to each layer. For example, in the case of a laminate structure of A layer / B layer / A layer, i.e., a two-type three-layer laminate structure, a method in which the B layer is made of homopolyethylene terephthalate from the viewpoint of transparency, and particles are added to the A layer to impart easy slippage, can be exemplified.

[0110] <Biomass raw materials and recycled raw materials> In the laminated polyester film of the present invention, it is preferable that the polyester substrate contains at least one of biomass raw materials and recycled raw materials from the viewpoint of reducing the environmental load. Here, biomass refers to an organic compound photosynthesized from carbon dioxide and water. When biomass is burned, it usually becomes carbon dioxide and water again, so biomass can be used as so-called carbon-neutral renewable energy.

[0111] When the biomass degree is defined as the ratio of plant-derived carbon atoms to the total carbon atoms, for example, in an ethylene terephthalate unit, if only the ethylene glycol component is entirely plant-derived, the biomass degree is theoretically 20%. To increase the biomass degree beyond that, the terephthalic acid must also be plant-derived, which would increase the environmental impact reduction effect but would increase production costs. The ethylene glycol component and the terephthalic acid component may be a combination of petroleum-derived and plant-derived components. From the viewpoint of achieving an environmental impact reduction effect, the lower limit of the biomass degree of the polyester constituting the film is preferably 5%, more preferably 10%, and even more preferably 13%. A biomass degree of 5% or more can be expected to reduce the environmental impact. On the other hand, when only considering the reduction of the environmental impact, the higher the upper limit of the biomass degree, the better, with 100% being the upper limit. From the viewpoint of achieving both production costs and environmental impact reduction, a practical setting of 20% or less is preferred.

[0112] As a known method for analyzing the presence or absence of biomass raw materials, for example, the carbon isotope ( １４ C).

[0113] Recycled raw materials are raw materials obtained by recovering, decomposing, and reusing polyesters that have been produced as chemical products once or multiple times. Examples of recycled raw materials for the laminated polyester film of the present invention include uncoated sections at both ends in the width direction cut and removed during the production process of the laminated polyester film of the present invention, recovered polyester films from other polyesters, and polyesters distributed in forms other than films, such as PET bottles. When producing a laminated polyester film, it is preferable to use recycled raw materials in an amount of 90% by mass or less of 100% by mass of polyester raw materials. Limiting the use of recycled raw materials to 90% by mass or less reduces the amount of highly crystalline polyesters that have once been converted into chemical products, thereby reducing the deterioration of the thermal properties and transparency of the resulting laminated polyester film and reducing coloration.

[0114] <Laminate, Processing Layer (Y)> The laminate of the present invention will be described below. The laminate of the present invention has a processing layer (Y) on the surface of the easy-adhesion layer (X) of the laminated polyester film of the present invention. That is, the laminated polyester film of the present invention is preferably used to manufacture a laminate in which a processing layer (Y) is further formed on the easy-adhesion layer (X). In addition, a wet coating method is preferably used to form the processing layer (Y), and the coating material for forming the processing layer (Y) is preferably an "aqueous coating material" in which water is the main solvent or dispersion medium. Here, "water is the main solvent or dispersion medium" means that the proportion of water in 100% by mass of the materials constituting the solvent or dispersion medium exceeds 50% by mass. The processing layer (Y) can be formed by any method selected from known coating methods, such as bar coating, reverse coating, gravure coating, die coating, blade coating, etc.

[0115] The processing layer (Y) is preferably a function-imparting layer that imparts different physical properties to the polyester film. Examples of the functions imparted include scratch prevention, electrical conductivity and antistatic properties, adhesive properties, prevention of various adhesions such as stains, transmission and absorption of various light rays from infrared to visible to ultraviolet, and easy peeling properties that can be used for protecting adherends and transfer processing. In particular, in the laminate of the present invention, it is particularly preferred that the processing layer (Y) contains at least one of a hard coating agent, an adhesive, and a printing ink, for example, for applications in which the laminated polyester film has adhesion and transparency.

[0116] On the other hand, it is more preferable that the processing layer (Y) contains a dispersant (D). By containing the dispersant (D), it is possible to disperse various compositions that realize the above-mentioned functionalization in water, which is the main solvent, and to improve the uniformity of application when forming the processing layer (Y) by a wet coating method. Details of the dispersant (D) will be described later.

[0117] In the laminate of the present invention, the moisture content of the processed layer (Y) is preferably 50 wtppm or more. When the moisture content of the processed layer (Y) is 50 wtppm or more, the dispersant (D) described below is present in the processed layer (Y) in a uniformly dispersed state, so that the processed layer (Y) can satisfactorily exhibit the various functions described below. On the other hand, when the moisture content of the processed layer (Y) is less than 50 wtppm, this means that the functional components are in an aggregated state when the processed layer (Y) is formed by the wet coating method, and in such cases, the processed layer (Y) may not be able to satisfactorily exhibit various functions.

[0118] One method for making the moisture content of the processed layer (Y) 50 wtppm or more is to use an "aqueous coating agent" as the coating agent for forming the processed layer (Y). By using an aqueous coating agent, the environmental impact during the formation of the processed layer can be reduced.

[0119] <Dispersant (D)> From the viewpoint of uniformly dispersing the various compositions that realize the above-mentioned functionalization, it is preferable that the processing layer (Y) contains a dispersant (D). That is, it is preferable that the water-based coating material for forming the processing layer (Y) contains a dispersant (D). The dispersant (D) is a material that assists the dissolution or dispersion of the various compositions that realize the above-mentioned functionalization in water, which is the main solvent or dispersion medium. Examples of the dispersant (D) include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants and other emulsifying dispersants, etc., and these can be used alone or in combination of two or more.

[0120] Examples of nonionic surfactants include (poly)alkylene oxide (AO) adduct nonionic surfactants and polyhydric alcohol nonionic surfactants. Examples of AO adducts include (poly)ethylene oxide (EO) adducts of C10-20 aliphatic alcohols, EO adducts of phenols, EO adducts of nonylphenols, EO adducts of C8-22 alkylamines, and EO adducts of poly(oxypropylene)glycols. Examples of polyhydric alcohol surfactants include fatty acid (8-24 carbon atoms) esters of polyhydric (tri- to octahydric or higher) alcohols (2-30 carbon atoms) (e.g., glycerin monostearate, glycerin monooleate, sorbitan monolaurate, sorbitan monooleate, etc.) and alkyl (4-24 carbon atoms) poly(degree of polymerization 1-10) glycosides.

[0121] Examples of anionic surfactants include ether carboxylic acids or salts thereof having a hydrocarbon group having 8 to 24 carbon atoms [such as sodium lauryl ether acetate and (poly)oxyethylene (addition mole number 1 to 100) sodium lauryl ether acetate]; sulfates or ether sulfates or salts thereof having a hydrocarbon group having 8 to 24 carbon atoms [such as sodium lauryl sulfate, (poly)oxyethylene (addition mole number 1 to 100) sodium lauryl sulfate, (poly)oxyethylene (addition mole number 1 to 100) triethanolamine lauryl sulfate and (poly)oxyethylene (addition mole number 1 to 100) sodium coconut oil fatty acid monoethanolamide sulfate]; sulfonates having a hydrocarbon group having 8 to 24 carbon atoms [such as sodium dodecylbenzenesulfonate]; (C10-C20 alkyl esters), sulfosuccinates having one or two of the following substituents; phosphate esters or ether phosphate esters having a hydrocarbon group having 8 to 24 carbon atoms or salts thereof [such as sodium lauryl phosphate and (poly)oxyethylene (molar addition number 1 to 100) sodium lauryl ether phosphate]; fatty acid salts having a hydrocarbon group having 8 to 24 carbon atoms [such as sodium laurate and triethanolamine laurate]; and acylated amino acid salts having a hydrocarbon group having 8 to 24 carbon atoms [sodium coconut oil fatty acid methyl taurate, sodium coconut oil fatty acid sarcosine, triethanolamine coconut oil fatty acid sarcosine, triethanolamine N-coconut oil fatty acid acyl-L-glutamate, sodium N-coconut oil fatty acid acyl-L-glutamate, sodium lauroylmethyl-β-alanine, etc.].

[0122] Examples of cationic surfactants include quaternary ammonium salt types [stearyltrimethylammonium chloride, behenyltrimethylammonium chloride, distearyldimethylammonium chloride, lanolin fatty acid aminopropylethyldimethylammonium ethyl sulfate, etc.] and amine salt types [stearic acid diethylaminoethylamide lactate, dilaurylamine hydrochloride, oleylamine lactate, etc.].

[0123] Examples of amphoteric surfactants include betaine-type amphoteric surfactants [such as coconut oil fatty acid amidopropyl dimethylaminoacetic acid betaine, lauryl dimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, lauryl hydroxysulfobetaine, and sodium lauroyl amidoethyl hydroxyethyl carboxymethyl betaine hydroxypropyl phosphate] and amino acid-type amphoteric surfactants [such as sodium β-laurylaminopropionate].

[0124] Other emulsifying dispersants include, for example, polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as carboxymethyl cellulose, methyl cellulose, and hydroxyethyl cellulose, carboxyl group-containing (co)polymers such as poly(sodium acrylate), and emulsifying dispersants having a urethane group or an ester group described in U.S. Pat. No. 5,906,704 [for example, a polycaprolactone polyol and a polyether diol linked with a polyisocyanate].

[0125] The presence or absence of the dispersant (D) is difficult to completely remove even from a coating material or a laminate, and can be confirmed by a combination of known organic substance identification methods such as nuclear magnetic resonance (NMR), gas chromatography-mass spectrometry (GC-MS), and Freefield transform infrared spectroscopy (FT-IR).

[0126] Next, the present invention will be described in more detail based on examples, but the present invention is not necessarily limited thereto. The methods for measuring each property and evaluating each effect in the present invention are as follows.

[0127] [Methods for Measuring Characteristics and Effect Evaluation] (1) Surface Energy of the Easy-Adhesion Layer (X) First, the laminated polyester film was left for 24 hours in an atmosphere at room temperature of 23°C and a relative humidity of 65%. Thereafter, in the same atmosphere, the contact angles of four liquids, namely, pure water, ethylene glycol, formamide, and diiodomethane, were measured at five points on the easy-adhesion layer (X) (resin layer) using a contact angle meter DM-501 (manufactured by Kyowa Interface Science Co., Ltd.), and the average of the measured values ​​was taken as the contact angle of each liquid. Next, using the contact angles of the four liquids obtained, the surface free energy (γ) of the solid was calculated by the geometric mean method based on the "expanded Fowkes equation" proposed by Hata et al., and the dispersion force component (γ Ｓ ｄ ), polar force component (γ Ｓ ｐ ), and hydrogen bonding strength component (γ Ｓ ｈ The surface energy, which is the dispersion force, polar force, hydrogen bonding force, and the sum of the dispersion force and polar force, was calculated. The specific calculation method is shown below. The meaning of each symbol is explained below. γ Ｓ Ｌ γ: Surface energy of the resin layer and the known solution listed in Table 1 Ｓ　 : Surface energy of resin layer γ Ｌ　 : Surface energy γ of the known solution listed in Table 1 Ｓ ｄ : Dispersion force component of the surface energy of the resin layer γ Ｓ ｐ : Polar component of the surface energy of the resin layer γ Ｓ ｈ : Hydrogen bonding force component of the surface energy of the resin layer γ L ｄ γ: dispersion force component of the surface energy of the known solution listed in Table 1 L ｐ γ: Polar force component of the surface energy of the known solutions listed in Table 1 L ｈ : Hydrogen bonding force component of the surface energy of the known solution listed in Table 1, where γ Ｓ Ｌ When γ is the tension at the interface between the solid and the liquid, the following equation (1) holds:Ｓ Ｌ = γ Ｓ +γ Ｌ -2(γ Ｓ ｄ ・γ Ｌ ｄ ) １／２ -2(γ Ｓ ｐ ・γ Ｌ ｐ ) １／２ -2(γ Ｓ ｈ ・γ Ｌ ｈ ) １／２ ... Equation (1).

[0128] The state when a droplet is in contact with a smooth solid surface at a contact angle (θ) is expressed by the following equation (2) (Young's equation): γ Ｓ = γ Ｓ Ｌ +γ Ｌ cosθ... Equation (2).

[0129] Combining these formulas (1) and (2), the following formula is obtained: (γ Ｓ ｄ ・γ Ｌ ｄ ) １／２ +(γ Ｓ ｐ ・γ Ｌ ｐ ) １／２ +(γ Ｓ ｈ ・γ Ｌ ｈ ) １／２ = γ Ｌ (1+cosθ) / 2... Equation (3).

[0130]

[0131] In practice, the contact angle (θ) and the surface tension components (γ) of the known liquids listed in Table 1 were measured for four types of liquids: water, ethylene glycol, formamide, and diiodomethane. L ｄ , γ L ｐ , γ L ｈ) into Equation (3) and solve the four simultaneous equations. As a result, the surface energy of the solid (γ), the dispersion force component (γ Ｓ ｄ ), polar force component (γ Ｓ ｐ ), and hydrogen bonding strength component (γ Ｓ ｈ ) was calculated. The dispersion force γd of the present invention is the dispersion force component (γ Ｓ ｄ ), and the hydrogen bonding strength γh is the hydrogen bonding strength component (γ Ｓ ｈ ) and the ratio γh / γd between them was calculated as a control factor for wettability.

[0132] (2) Measurement of Advancing Angle and Receding Angle of Water of Adhesion Layer (X) The advancing angle θa and the receding angle θr of water of the adhesion layer (X) were measured by the expansion-contraction method. The measurement device used was a contact angle Drop Master DM-501 manufactured by Kyowa Interface Science Co., Ltd., and the measurement method followed the expansion-contraction method measurement manual for the device.

[0133] The advancing angle θa was measured by continuously supplying droplets to the adhesive layer (X) at a liquid discharge rate of 2.0 μL / sec up to a final droplet volume of 50 μL. Images of the droplets during their expansion process were taken from before the start of discharge to the end of discharge, and the contact angle was determined. Images were taken for a certain period of time before the start of supply and after the end of supply, but the analysis software excluded the data taken before and after the start of supply from the five data points used to calculate the contact angle. The contact angle during the droplet expansion process initially changes as the droplet expands, and then becomes almost constant. Therefore, the contact angles were measured in the direction of droplet expansion, and five consecutive points were selected in that order. The average value at which the standard deviation of the five consecutive points first became 1° or less was taken as the advancing angle for that measurement. This measurement was repeated five times, and the average value was taken as the advancing angle θa of the water for that sample.

[0134] Meanwhile, the receding angle θr was measured by continuously aspirating a droplet with an initial droplet volume of 50 μL and a liquid discharge rate of 2.0 μL / sec. Images of the droplet's contraction process were taken from before the start of discharge to the end of discharge, and the contact angle was calculated for each. Images were taken for a certain period before the start of suction and after the end of suction, but the analysis software excluded the images taken before and after the start of suction from the five data points used to calculate the contact angle. The contact angle during the droplet contraction process initially changes as the droplet shrinks, then becomes nearly constant. Therefore, the contact angles were measured in the direction of the droplet contraction, and five consecutive points were selected in that order. The average value at which the standard deviation of the five consecutive points first became 1° or less was taken as the receding angle for that measurement. This measurement was repeated five times, and the average value was taken as the receding angle θr of the water for that sample.

[0135] (3) Film Thickness of Easy-Adhesion Layer (X) The thickness of the easy-adhesion layer (X) (resin layer) on the polyester substrate was measured by observing the cross section using a transmission electron microscope (TEM). The thickness of the resin layer was read from an image taken with a TEM at a magnification of 200,000 times. The film thickness of the resin layer was measured at a total of 20 points, and the average value was taken as the film thickness of the easy-adhesion layer (X).

[0136] (4) Measurement of Elastic Modulus Using Atomic Force Microscope (AFM) The elastic modulus of the surface of the resin layer was measured using an AFM (DimensionIcon manufactured by Burker Corporation) in PeakForceQNM mode. Using the attached analysis software "NanoScopeAnalysis V1.40", an analysis based on the JKR contact theory was performed from the obtained force curve to determine the elastic modulus distribution. Specifically, first, the measurement surface of the laminated polyester film (the easy-adhesion layer (X) surface) was fixed to the sample stage using double-sided tape so that it was on top. Next, according to the PeakForceQNM mode manual, the cantilever warpage sensitivity, spring constant, and tip curvature were configured, and then measurements were carried out under the following conditions. The data from the obtained DMT Modulus channel was used as the elastic modulus of the resin layer. The measurement conditions are shown below. Measurement device: Atomic force microscope (AFM) manufactured by Bruker Corporation (Model number: DimensionIcon) Measurement mode: PeakForceQNM (force curve method) Cantilever: RTESPA-300 manufactured by Bruker AXS Measurement atmosphere: 23°C, in air Measurement range: 5 (μm) square Resolution: 512 x 512 Measurement speed: 0.977 Hz Cantilever movement speed: 10 (μm / s) Indentation load (Setpoint): 40 (nN) Poisson's ratio: 0.4.

[0137] Next, the obtained data of the DMT Modulus channel was analyzed using the analysis software "NanoScopeAnalysis V1.40" and processed using Roughness to obtain the Image Raw Mean value in the Results tab. The value was defined as the modulus of elasticity of the easy-adhesion layer (X).

[0138] (5) Measurement of Total Light Transmittance and Haze Five square laminated polyester film samples, each 5 cm on a side, were prepared. The samples were then left at room temperature (23°C, 50% relative humidity) for 40 hours. The total light transmittance and haze of each sample were measured using a turbidity meter "NDH5000" manufactured by Nippon Denshoku Industries Co., Ltd., in accordance with JIS "Determination of Haze of Transparent Materials" (K7136, 2000 edition). The total light transmittance and haze values ​​of each of the five samples were averaged to obtain the total light transmittance and haze values ​​of the laminated polyester film.

[0139] (6) Application of Water-Based Coating Material The non-volatile components of the water-based UV-curable hard coat component were adjusted as follows: - Water-based UV-curable resin WBR-8519D manufactured by Taisei Fine Chemical Co., Ltd.: 97 parts by weight - Photoinitiator "OMNIRAD" (registered trademark) 819DW manufactured by IGM Resin B.V.: 3 parts by weight Furthermore, pure water as a dispersion medium and a fluorine-based surfactant ("PLASCOAT" (registered trademark) RY-2 manufactured by GOO Chemical Industry Co., Ltd.) as a surfactant were mixed into the above water-based UV-curable hard coat component at 0.1% of the total coating material to prepare a water-based UV-curable hard coat coating material. The obtained water-based UV-curable hard coat coating material was applied to the surface of the easy-adhesion layer (X) of the laminated polyester film by a wire bar coating method to a thickness of about 1 μm, and after drying at 120 ° C. for 1 minute, it was subjected to irradiation using an ultraviolet lamp with an irradiation intensity of 120 W / cm, an irradiation distance (distance between the lamp and the coated surface of the water-based coating material) of 12 cm, a conveyor speed of 2 m / min, and an integrated intensity of about 300 mJ / cm ２ The thickness of the hard coat layer (i.e., the processed layer (Y)) was adjusted to about 1 μm by blending pure water so that the nonvolatile content of the coating agent was 30 mass %, and adjusting the thickness by selecting a wire bar to be used in the wire bar coating method.

[0140] (7) Evaluation of Hard Coat Adhesion <Cross-Cut Method> In the hard-coated laminated polyester film sample obtained in (6), 25 5x5 squares were cut at 2 mm intervals according to JIS 5600-5-6 (established in 1999). Next, 18 mm "Cellotape" (registered trademark) (manufactured by Nichiban Co., Ltd., product number: CT-18S) was firmly rubbed with a finger on the cut area and pressed down so that the cut was visible. The "Cellotape" (registered trademark) was then instantly peeled off at an angle of approximately 60° to the hard coat layer. Thereafter, the number of squares where the hard coat layer remained was counted. The evaluation was performed five times, and the adhesion of the hard coat was evaluated using the average value (rounded up to the nearest whole number). The evaluation criteria were as follows: a percentage of squares where the hard coat layer remained of 90% or more was considered good.

[0141] (8) Coating property of water-based coating material (interference unevenness) (coating appearance) A hard-coated laminated polyester film was obtained in the same manner as in (6). Next, samples of 8 cm (width direction) x 10 cm (longitudinal direction) and 21 cm (width direction) x 30 cm (longitudinal direction) were cut out from the obtained hard-coated laminated polyester film, and black glossy tape (Yamato Co., Ltd., vinyl tape No. 200-50-21: black) was attached to the opposite side of the hard coat layer so as not to trap air bubbles. This sample was placed 30 cm directly below a three-wavelength fluorescent lamp (Panasonic Corporation, three-wavelength daylight white (F.L 15EX-N 15W)) in a dark room, and the degree of interference fringes was visually observed while changing the viewing angle, and the following evaluation was performed. A grade of B or higher was considered good. A: The spacing of the interference pattern was wider than B, or the interference pattern was not visible. B: There were five or more striped interference patterns spaced per 1 cm. C: Uncoated areas were present in some areas.

[0142] (9) Thickness Unevenness of Processed Layer (Y) A hard-coated laminated polyester film was obtained in the same manner as in (6). The thickness of the hard-coated layer (processed layer (Y)) was then measured by spectral interferometry using a Filmetrics thickness measurement system "Filmetrics F20" (Filmetrics). Specifically, 15 randomly selected points were measured on the 8 cm x 10 cm sample piece with black tape attached to the back side, prepared in (8), and the difference between the maximum and minimum values ​​was taken as the thickness unevenness.

[0143] (10) Measurement of the average roughness Ra and 10-point average roughness Rz of the easy-adhesion layer (X) (4) AFM measurement data was obtained in the same manner. Then, the data of the obtained Height Sensor channel was analyzed using the analysis software "NanoScopeAnalysis V1.40", and the image obtained by processing in Flatten mode under the conditions of XY direction and 3rd was analyzed in the entire range in Roughness mode, and the calculated Ra was used as the average roughness Ra of the easy-adhesion layer (X). Meanwhile, the image of Roughness mode was divided into 5 areas of 102 × 512 so that there was no overlap between them, and the difference between the MAX Peak Height (Rp) and Maximum Depth (Rv) in each range, and the average value (Rzx) of 5 points was obtained. Similarly, the image was divided into five areas of 512 x 102, and the difference between the obtained Rp and Rv and the average value (Rzy) of the five points were compared with the above Rzx, and the larger one was taken as the 10-point average roughness Rz.

[0144] (11) Blocking Resistance A film having an easy-adhesion layer (X) and a back surface thereof overlapped (overlap area: 3 cm x 4 cm) was subjected to a load of 6 kg / 12 cm. ２ After leaving the film at 60°C and 95% RH for 150 hours with a load of 1000 kJ / s, the state of peeling at the load-applied area was visually observed. The evaluation criteria were as follows, with A, B, and C being rated as good. A: Peeled easily and no overlapping traces remained. B: Peeled easily, but overlapping traces remained in some places. C: Peeled, but overlapping traces remained. D: The film cleaved when peeled.

[0145] (12) Measurement of Moisture Content of Processed Layer (Y) The moisture content of the processed layer (Y) was quantified by thermal evolved gas analysis (TPD-MS). The specific procedure is as follows. First, a laminate having the processed layer (Y) was obtained as in (5). Next, the processed layer (Y) was scraped off from the laminate using a diamond file (#200) to obtain a total of 100 mg of powder. Next, a heating device with a temperature controller was directly connected to a mass spectrometer, and the powder was placed on the heating stage. As a preparatory step, helium gas was passed through at 50 ml / min for 15 minutes. Furthermore, in a helium atmosphere, the temperature was raised from room temperature to 300°C at a rate of 10°C / min. The moisture content of the processed layer (Y) was determined by analyzing and integrating the concentration of water evolved from the laminate during heating. The moisture content (wtppm) was then calculated by dividing by the sample mass. The measurement equipment and conditions were as follows: Mass spectrometer: Shimadzu GC / MS QP5050A MS sensitivity: Gain 1.40 kV Mass number: m / z = 18 (H ２ O) Atmosphere: Helium flow (50 ml / min) Sample mass: 100 mg.

[0146] (13) Analysis of Variation Width and Domain Area Using Elastic Modulus Variation Image Elastic modulus images were measured in the same manner as in (4), except that the measurement range was 1 μm square. The measurement conditions are as follows: Measurement device: Atomic force microscope (AFM) manufactured by Bruker Corporation (Model number: DimensionIcon) Measurement mode: PeakForceQNM (force curve method) Cantilever: RTESPA-300 manufactured by Bruker AXS Measurement atmosphere: 23°C, in air Measurement range: 1 (μm) square Resolution: 512 × 512 Measurement speed: 0.977 Hz Cantilever movement speed: 10 (μm / s) Indentation load (Setpoint): 40 (nN) Poisson's ratio: 0.4.

[0147] The obtained DMT Modulus channel data was then analyzed using the analysis software "NanoScopeAnalysis V1.40." First, the data was smoothed in Flatten mode with Order: 3rd to obtain an "elastic modulus variation image." Next, the "elastic modulus variation image" was analyzed in Roughness mode, and Image Rmax was used as the variation width.

[0148] On the other hand, for the analysis of domain area, the "elastic modulus variation image" was converted to a grayscale image by selecting Color table: 7 from Adjust Image Color Scale in the Commands tab (corresponding to the schematic diagrams shown in Figures 1 and 2). Furthermore, the elastic modulus variation image was colored in Bearing Analysis mode with Bearing Area Percent: 10%. Next, the colored area was selected based on the hue using Color Threshold, an image processing software developed by the National Institutes of Health (NIH). Furthermore, the average area of ​​each domain was calculated using the Analyze Particles function. The area of ​​noise was excluded by setting the size range to 5-infinity (pixel^2) in the measurement conditions for Analyze Particles. The average area of ​​each domain obtained by the above operation was used as the domain area.

[0149] [Resin] First, the following resins were obtained for preparing the coating composition.

[0150] (Reference Example 1) Resin 1 An aqueous dispersion of polyester resin having the following copolymerization composition was obtained. The following copolymerization components and 0.1 parts of potassium titanium oxalate as a catalyst were added to a reactor, and the temperature was raised to 200°C while stirring and mixing at normal pressure in a nitrogen atmosphere. Next, the reaction temperature was gradually raised to 250°C over 4 hours to terminate the transesterification reaction. 15 parts by mass of the polyester resin thus obtained and 85 parts by mass of water were added to a dissolution tank and dispersed with stirring at a temperature of 80 to 95°C over 2 hours to obtain a 15% by mass aqueous dispersion of polyester resin. This was designated Resin 1. <Copolymerization Components> (Dicarboxylic Acid Component) Dimethyl 2,6-naphthalenedicarboxylate: 88 mol % Sodium dimethyl 5-sulfoisophthalate: 12 mol % (Diol Component) Compound in which 2 moles of ethylene oxide are added to 1 mole of bisphenol S: 86 mol % 1,3-propanediol: 14 mol % (Reference Example 2) Resin 2 Under a nitrogen gas atmosphere and at room temperature (25°C), 100 parts by mass of water, 1 part by mass of sodium lauryl sulfate, and 0.5 parts by mass of ammonium persulfate were placed in a vessel 1, and the temperature was raised to 70°C to dissolve the sodium lauryl sulfate, thereby obtaining a solution 1 at 70°C. At room temperature (25°C), 30 parts by weight of water and 2 parts by weight of sodium lauryl sulfate were added to container 2 to dissolve the sodium lauryl sulfate. Then, 13.3 parts by weight of polyethylene oxide monomethacrylate (10 repeating units of ethylene oxide) was added as an acrylic monomer component having a polyalkylene oxide, and 29.7 parts by weight of ethyl acrylate, 50.0 parts by weight of methyl methacrylate, and 5.0 parts by weight of N-methylolacrylamide were added as other monomer components and stirred to obtain solution 2. Under a nitrogen gas atmosphere, solution 1 was transferred to a reactor, and while maintaining the temperature of the solution in the reactor at 70°C, solution 2 was continuously added dropwise to solution 1 over 3 hours. After completion of the dropwise addition, the mixture was further stirred at 85°C for 2 hours, then cooled to 25°C to terminate the reaction and obtain an acrylic resin emulsion. This was designated resin 2.

[0151] (Reference Example 3) Resin 3 Under a nitrogen gas atmosphere and at room temperature (25°C), 66 parts by mass of polyester-based urethane resin (DIC Corporation's "HYDRAN" (registered trademark) AP-40(F)), 35 parts by mass of methyl methacrylate, 29 parts by mass of ethyl acrylate, and 2 parts by mass of N-methylol acrylamide were charged into vessel 3 to obtain solution 3. Next, 7 parts by mass of an emulsifier (ADEKA Corporation's "REASORP" ER-30) was added, and water was added so that the solids content of the solution became 50% by mass, to obtain solution 4. Under room temperature (25°C), 30 parts by mass of water was added to vessel 4, and the temperature was raised to 60°C. Thereafter, while stirring, solution 4 was continuously added dropwise to vessel 4 over 3 hours. At the same time, 3 parts by mass of a 5% by mass aqueous potassium persulfate solution was continuously added dropwise to vessel 4. After the dropwise addition was completed, the mixture was stirred for an additional 2 hours and then cooled to 25° C. to terminate the reaction, yielding an aqueous dispersion of an acrylic-urethane copolymer resin, designated Resin 3.

[0152] Reference Example 4 Resin 4 An aqueous dispersion of a polyester resin (Tg 80°C) composed of terephthalic acid (88 mol%), 5-sodium sulfoisophthalic acid (12 mol%), ethylene glycol (95 mol%), and diethylene glycol (5 mol%) was obtained in the same manner as in Reference Example 1. This was designated Resin 4.

[0153] Reference Example 5 Resin 5 An aqueous dispersion of polyester resin 5 (Tg: 66°C) composed of terephthalic acid (99 mol%), 5-sodium sulfoisophthalic acid (1 mol%), ethylene glycol (70 mol%), and neopentyl glycol (30 mol%) was obtained in the same manner as in Reference Example 1. This was designated Resin 5.

[0154] [Other Components] The following materials were used as reactive compounds, surfactants, etc. Reactive compound 1: carbodiimide aqueous crosslinking agent (Nisshinbo Chemical Inc.'s "CARBODILITE" (registered trademark) V-04) Reactive compound 2: oxazoline-containing polymer aqueous dispersion (Nihon Shokubai Co., Ltd.'s "EPOCROS" (registered trademark) WS-500) Reactive compound 3: melamine resin water sol (DIC Corporation's "WATERSOL" (registered trademark) S-695) Reactive compound 4: branched isocyanate compound (Dai-ichi Kogyo Seiyaku Co., Ltd.'s "ELASTRON" (registered trademark) E-37) Surfactant: fluorine-based surfactant (Gooo Chemical Industry Co., Ltd.'s "PLASCOAT" (registered trademark) RY-2) Inorganic particles 1: silica particles with a number average particle size of 170 nm (Nissan Chemical Industries, Ltd.'s "SNOWTEX" (registered trademark) MP-2040). Inorganic particles 2: silica particles having a number average particle diameter of 100 nm ("Snowtex" (registered trademark) MP-1040, manufactured by Nissan Chemical Industries, Ltd.). Inorganic particles 3: silica particles having a number average particle diameter of 1 μm ("Sicastar" (registered trademark) 43-00-103, manufactured by Micromod Corporation). The number average molecular weight can be determined from analysis of particle images observed by a cross-section transmission electron microscope (TEM) in the case of a film, or from number-based analysis by dynamic light scattering (DLS) in the case of a coating composition.

[0155] Example 1 Coating Composition First, resin 1, reactive compound 1, and reactive compound 2 were mixed in a mass ratio of 100:30:30, and then 0.5 parts by mass of inorganic particles 1 was added to 100 parts by mass of binder resin (resin 1). The concentration was adjusted using water as a solvent, and then 0.03 parts by mass of a surfactant was added to a total of 100 parts by mass of water to adjust the coating properties. Here, the method for adjusting the concentration using water will be described in detail. Specifically, the concentration was determined according to the target thickness of the adhesion layer (X) using the following method. The thickness of the adhesion layer (X) is proportional to the concentration of the coating composition and the coating thickness, and inversely proportional to the widthwise stretching ratio and the specific gravity of the adhesion layer (X). The coating thickness is uniquely determined from the count used for bar coating, and the stretching ratio is uniquely determined from the film-forming conditions. Therefore, a plurality of concentrations of the coating composition were prepared in advance, and a calibration curve was created by measuring the thickness of the easy-adhesion layer (X) using the above-mentioned method, and the concentration of the coating composition that matches the target thickness of the easy-adhesion layer (X) was determined. The concentration of the obtained coating composition was approximately 2.5% by mass to 4.5% by mass. In this way, the coating composition was obtained.

[0156] <Laminated Polyester Film> PET pellets (intrinsic viscosity 0.64 dl / g) containing two types of particles (4% by mass of silica particles with a primary particle size of 0.3 μm and 2% by mass of calcium carbonate particles with a primary particle size of 0.8 μm) were thoroughly vacuum-dried, fed into an extruder, melted at 280°C, extruded into a sheet from a T-shaped die, and wrapped around a mirror-finished casting drum at a surface temperature of 25°C by an electrostatic casting method, where it was cooled and solidified. The composition and particle size of the particles contained in the PET pellets were measured by a combination of shape analysis by TEM and elemental analysis by energy dispersive X-ray spectroscopy (EDX) on thin film sections prepared using a cryomicrotome. On the other hand, the intrinsic viscosity was measured by an extrapolation method according to JIS K 7367:2002, in which PET pellets were dissolved in a solvent capable of dissolving the pellets (e.g., hexafluoroisopropanol), viscosity measurements were carried out at a plurality of concentrations, and the viscosity at 100% (i.e., the intrinsic viscosity) was calculated from an approximation curve.

[0157] The unstretched film (Film A) thus obtained was heated to 90°C and stretched 3.1 times in the longitudinal direction to produce a uniaxially stretched film (Film B). The uniaxially stretched film was then subjected to a corona discharge treatment in air, after which the above-mentioned coating composition was applied using a bar coater (wire bar #4). The uniaxially stretched film coated with the coating composition was then gripped with clips at both widthwise ends and introduced into a preheating zone. The ambient temperature in the preheating zone was set to 90-100°C, and the solvent in the coating composition was dried. Subsequently, the film was continuously stretched 3.6 times in the widthwise direction in a 100°C stretching zone and heat-treated for 20 seconds in a 240°C heat treatment zone to form an easy-adhesion layer (X). Further, a 5% relaxation treatment in the widthwise direction at the same temperature was performed to obtain a laminated polyester film in which the polyester film had completed its crystalline orientation. In the resulting laminated polyester film, the PET film (polyester substrate) had a thickness of 50 μm, and the easy-adhesion layer (X) had a thickness (film thickness) of 80 nm. The evaluation results are shown in Table 3.

[0158] (Examples 2, 5 to 15, Comparative Examples 1, 2, 4) Laminated polyester films were obtained in the same manner as in Example 1, except that the formulation of the coating composition and the drying temperature (maximum processing temperature) were as shown in Table 2. In the obtained laminated polyester films, the thickness of the PET film (polyester substrate) was 50 μm, and other evaluation results are shown in Table 3.

[0159] Example 3 A laminated polyester film was obtained using the coating composition of Example 1 in the following manner. A PET film "Lumirror" (registered trademark) T60 (thickness: 50 μm) manufactured by Toray Industries, Inc. was used as the substrate. The coating composition was applied onto the substrate using a wire bar, and then dried and cured in a hot air oven at 180°C for 2 minutes. The thickness of the PET film (polyester substrate) in the obtained laminated polyester film was 50 μm, and other evaluation results are shown in Table 3.

[0160] Example 4, Comparative Example 3 A laminated polyester film was obtained in the same manner as in Example 3, except that the drying temperature of the coating composition was changed.

[0161] Examples 16 and 17 Laminated polyester films were obtained in the same manner as in Example 6, except that recycled materials and biomass materials were used as raw materials for the polyester substrate in the proportions shown in Table 2. The evaluation results are shown in Table 3.

[0162] The recycled raw material was prepared by shredding the uncoated portions at both ends in the width direction that had been gripped by clips in the tenter, which had been removed in the film-forming process in Examples 1, 2, 5 to 15 and Comparative Examples 1, 2, and 4, and kneading them with virgin raw material. On the other hand, the biomass raw material was prepared in the same manner as the starting raw material, except that PET pellets (biomass content 15%) in which part of the ethylene glycol had been replaced with plant-derived monoethylene glycol were used.

[0163]

[0164]

[0165]

[0166] The present invention relates to an easily adhesive film that has excellent application properties and adhesion, particularly with water-based coating materials, and also has excellent transparency. It can be used for magnetic recording materials, packaging materials, anti-reflection films used in flat displays, optical films such as diffusion sheets and prism sheets, transparent touch panels, etc., and is particularly suitable for use in products that include post-processing steps using water-based coating materials.

[0167] 1: Representative black area in the elastic modulus variation image 2: Representative white area in the elastic modulus variation image

Claims

1. A laminated polyester film having an easy-adhesion layer (X) on the outermost surface of at least one side of a polyester substrate, wherein the ratio (γh / γd) of the dispersion force (γd) to the hydrogen bonding force (γh) in the surface free energy of the easy-adhesion layer (X) is 0.140 or less.

2. A laminated polyester film having an easy-adhesion layer (X) on the outermost surface of at least one side of a polyester base material, wherein the easy-adhesion layer (X) has an advancing water angle θa of 75.0° or more and 110.0° or less and a receding water angle θr of 5.0° or more and 40.0° or less.

3. 3. The laminated polyester film according to claim 2, wherein the polyester substrate has an easy-adhesion layer (X) on the outermost surface of at least one side thereof, and the easy-adhesion layer (X) has a surface free energy ratio (γh / γd) of dispersion force (γd) to hydrogen bonding force (γh) of 0.140 or less.

4. The laminated polyester film according to claim 1 or 2, wherein the dispersion force (γd) on the surface of the adhesive layer (X) is 32.0 mN / m or more.

5. 3. The laminated polyester film according to claim 1, wherein the adhesive layer (X) has an average elastic modulus of 1.0 GPa or more in a 5 μm square area measured by AFM.

6. The domain area of the adhesive layer (X) in a 1 μm square elastic modulus variation image measured by AFM is 500 nm ２ The laminated polyester film according to claim 1 or 2, wherein:

7. 3. The laminated polyester film according to claim 1, which has a haze value of 2.0% or less.

8. 3. The laminated polyester film according to claim 1, wherein the adhesive layer (X) contains at least two kinds of resins or compounds selected from the group consisting of polyester resins, oxazoline compounds, and carbodiimide compounds.

9. 3. The laminated polyester film according to claim 1, wherein at least one surface satisfies (1) and (2). (1) The average roughness Ra is 1.0 nm or more and 20.0 nm or less. (2) The ten-point average roughness Rz is 50.0 nm or more and 400.0 nm or less.

10. The laminated polyester film according to claim 1 or 2, wherein the polyester substrate comprises at least one of a biomass material and a recycled material.

11. A laminate comprising the laminated polyester film according to claim 1 or 2, and a processable layer (Y) on the surface of the adhesive layer (X).

12. The laminate according to claim 11, wherein the moisture content of the processing layer (Y) is 50 wtppm or more.

13. The laminate according to claim 11, wherein the processing layer (Y) contains at least one of a hard coating agent, an adhesive, and a printing ink, and also contains a dispersant (D).

14. 3. A method for producing the laminated polyester film according to claim 1, comprising a step of forming the easy-adhesion layer (X) by thermally curing a coating composition at 170°C or higher.