Laminated Polyester Film

Abstract

To provide a laminated polyester film with excellent antifogging performance and also easy adhesiveness with which a tape adheres thereto.SOLUTION: Provided is a laminated polyester film comprising a polyester film, and a resin layer formed on at least either surface of the polyester film, in which the resin composition includes (A) a binder resin and (B) a hydrophilic compound, and satisfies a relation between the following formulas (1) and (2): (1) γ1p≥20.0 mN / m and (2) (γ2d / γ2p)≥0.91 (γ1p represents a polar component of a surface free energy on the resin layer surface, calculated by a contact angle one second after liquid comes into contact with the resin layer surface, and γ2d and γ2p represent a dispersion component and a polar component of the surface free energy on the resin layer surface respectively, calculated by a contact angle 30 seconds after liquid comes into contact with the resin layer surface).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminated polyester film. [Background technology]

[0002] Polyester films, such as polyethylene terephthalate films and polyethylene naphthalate films, are used in a variety of applications because they have excellent properties such as mechanical properties, dimensional stability, flatness, heat resistance, chemical resistance, and optical properties, and also have excellent cost performance.

[0003] As an example of the use of polyester films, anti-fog films imparted with anti-fog properties have been proposed, and these films are used in windows, mirrors, lenses, goggles, masks, shields, and the like. When used for these purposes, a method of laminating a resin layer with excellent anti-fogging properties on the surface of a polyester film has been investigated (for example, Patent Document 1).

[0004] In medical settings, bodily fluids, blood, droplets, etc. of patients are scattered during treatment and may accidentally come into contact with the eyes, mouth, or nose of medical personnel. If a patient receiving treatment carries infectious pathogens, the medical personnel may become infected with the pathogens when their bodily fluids come into contact with their eyes, mouth, or nose. In particular, due to the recent global spread of the novel coronavirus disease (COVID-19), there is an increasing need to ensure that medical personnel do not come into contact with the virus when treating infected patients, so that they do not become infected. For this reason, there has been active development of medical face protection equipment, known as face shields.

[0005] For example, Patent Document 2 discloses, as an example of a face shield, a shield that protects the eyes of a user wearing a nonwoven fabric mask. This shield includes an attachment part formed on the lower edge of the shield, which is superimposed on the nonwoven fabric mask and attached to the nonwoven fabric mask, and an eye protection part formed on the upper edge of the shield and capable of protecting the eyes of the user, and a connecting part formed on the attachment part that is detachably fixed to the nonwoven fabric mask. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2011-513513 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-142654 Summary of the Invention [Problem to be solved by the invention]

[0007] Face shields such as the shield in Patent Document 2 have the problem that when used to cover the face, the shield can fog up due to the user's breath, reducing the user's visibility. For this reason, shields are required to have excellent anti-fogging properties.

[0008] Furthermore, when a part of the anti-fogging surface, including the shield disclosed in Patent Document 2, is to be attached to something with double-sided tape or the like, the surface must also have the property of easily adhering to the tape. In particular, although the film disclosed in Patent Document 1 has anti-fogging properties, no consideration has been given to its adhesion to tape, which may limit the manner in which it can be used.

[0009] Therefore, the present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a laminated polyester film that has excellent anti-fogging properties and also has easy adhesive properties that allow tape to adhere to it. [Means for solving the problem]

[0010] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by the following configuration. The present invention has the following aspects.

[0011] [1] A laminated polyester film comprising a polyester film and a resin layer formed from a resin composition on at least one side of the polyester film, wherein the resin composition contains (A) a binder resin and (B) a hydrophilic compound, and the laminated polyester film satisfies the relationship between the following formulas (1) and (2): γ1 p ≧20.0 mN / m (1) (γ2 d / γ2 p ) ≥ 0.91 (2) (However, γ1 p represents the polar component of the surface free energy of the resin layer surface, calculated from the contact angle 1 second after the liquid contacts the resin layer surface, and γ2 d and γ2 p represent the dispersive component and polar component of the surface free energy of the resin layer surface, respectively, calculated from the contact angle 30 seconds after a liquid comes into contact with the resin layer surface. [2] The laminated polyester film according to the above [1], further satisfying the following formula (3): (γ2 d / γ2 p )-(γ1 d / γ1 p ) ≥ 0.02 (3) (However, γ1 d represents the dispersion component of the surface free energy of the resin layer surface, calculated from the contact angle 1 second after a liquid comes into contact with the resin layer surface. [3] The laminated polyester film according to [1] or [2] above, wherein the water droplet contact angle 1 second after contact of a water droplet with the surface of the resin layer is 45 degrees or less. [4] The laminated polyester film according to any one of the above [1] to [3], wherein the resin layer surface has a water droplet contact angle of 36 degrees or less 30 seconds after contact with the water droplet. [5] The laminated polyester film according to any one of the above [1] to [4], wherein the binder resin (A) comprises at least one resin selected from the group consisting of polyurethane resins and polyester resins. [6] The laminated polyester film according to any one of the above [1] to [5], wherein the hydrophilic compound (B) includes a dialkyl sulfosuccinate. [7] The laminated polyester film according to any one of the above [1] to [6], wherein the content of the binder resin (A) is 30 to 97 mass % as a non-volatile component. [8] The laminated polyester film according to any one of the above [1] to [7], wherein the resin composition further contains (C) particles. [9] The laminated polyester film according to any one of the above [1] to [8], wherein the resin composition further contains (D) a fluorine-containing surfactant.

[10] The laminated polyester film according to any one of the above [1] to [9], wherein at least a part of the resin layer comprises an adhesive layer.

[11] The laminated polyester film according to any one of the above [1] to

[10] , which is for a face shield. [Effects of the Invention]

[0012] According to the present invention, there is provided a laminated polyester film having excellent anti-fogging properties and also having high adhesive properties that allow tape to adhere to it. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is an image diagram showing the face shield according to an embodiment of the present invention when in use. [Figure 2] 1 is a schematic cross-sectional view of a face shield according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Next, an example of an embodiment of the present invention will be described, but the present invention is not limited to the embodiment described below.

[0015] In this specification, when the expression "(meth)acrylic" is used, "(meth)acrylic" means one or both of "acrylic" and "methacrylic". Similarly, "(meth)acrylic acid" means one or both of "acrylic acid" and "methacrylic acid", "(meth)acrylate" means one or both of "acrylate" and "methacrylate", and "(meth)acryloyl" means one or both of "acryloyl" and "methacryloyl". The same applies to other terms.

[0016] <<<Laminated polyester film>>> The laminated polyester film of the present invention (hereinafter also referred to as "the present laminated polyester film") comprises a polyester film (hereinafter also referred to as "the present polyester film") and a resin layer (hereinafter also referred to as "the present resin layer") formed from a resin composition on at least one side of the polyester film.

[0017] The laminated structure of the present laminated polyester film may be a structure in which a resin layer is formed on one side of a polyester film and the surface of the polyester film is left as is on the other side, or a structure in which another layer is formed on the other side. Alternatively, a resin layer may be formed on both sides of a polyester film. Furthermore, the resin layer may be formed directly on the polyester film, or another layer may be provided between the polyester film and the resin layer.

[0018] <<Polyester film>> The polyester film serves as the substrate of the laminated polyester film. The polyester film may have a single layer structure or a multilayer structure. When the polyester film has a multilayer structure, the polyester film may have a two-layer structure, a three-layer structure, or a four-layer structure or more, without departing from the gist of the present invention. The number of layers is not particularly limited. When the polyester film has a multilayer structure of two or more layers, a two-kind three-layer structure or a three-kind three-layer structure is particularly preferred. When the polyester film has a multilayer structure, it is also preferred that the polyester film has a structure in which surface layers are provided on both sides of an intermediate layer.

[0019] The polyester film may be either an unstretched film (sheet) or a stretched film. A uniaxially or biaxially stretched film is preferred. A biaxially stretched film is more preferred because of its excellent balance of mechanical properties and flatness.

[0020] <Polyester> The polyester, which is the raw material of the polyester film, refers to a polymer compound having continuous ester bonds in the main chain, and may be a homopolyester or a copolymer polyester. Specific examples include polyesters obtained by polycondensation of a dicarboxylic acid component and a diol component. Furthermore, it is preferable to use a polyester containing more than 50 mol% of an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid, based on 100 mol% of the dicarboxylic acid component.

[0021] Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, and 4,4'-diphenylsulfonedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid, and ester derivatives thereof.

[0022] Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-hexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis(4-hydroxyethoxyphenyl)propane, isosorbate, and spiroglycol.

[0023] When the polyester is a homopolyester, it is preferably one obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic diol. Preferred examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and preferred examples of the aliphatic diol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Representative examples of homopolyesters include polyethylene terephthalate (PET) and polyethylene-2,6-naphthalenedicarboxylate (PEN), with polyethylene terephthalate being preferred.

[0024] On the other hand, the copolymer polyester is preferably a polycondensation polymer of a dicarboxylic acid component and an aliphatic diol. The dicarboxylic acid component preferably includes one or more of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (e.g., p-oxybenzoic acid). The aliphatic diol preferably includes one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, and neopentyl glycol. The copolymer polyester more preferably includes terephthalic acid as the dicarboxylic acid component and ethylene glycol as the aliphatic diol. When the polyester is a copolymer polyester, it is preferably a copolymer containing 30 mol % or less of a third component. The third component is a component other than the compound that is the main component (i.e., the component with the highest content) of the dicarboxylic acid component constituting the polyester and the compound that is the main component of the diol component, such as a component other than terephthalic acid and ethylene glycol in the case of copolymer polyethylene terephthalate. The copolymer polyester may also contain structural units derived from difunctional compounds other than dicarboxylic acid components and aliphatic diols. The structural units derived from difunctional compounds other than dicarboxylic acid components and aliphatic diols are preferably 20 mol% or less, more preferably 10 mol% or less, based on the total moles of all structural units constituting the polyester. Examples of the difunctional compound include various hydroxycarboxylic acids and aromatic diols.

[0025] The content of terephthalic acid in all dicarboxylic acid components constituting the present polyester film is preferably 50 mol % or more, more preferably 70 mol % or more, and even more preferably 90 mol % or more. The content of ethylene glycol in all diol components constituting the present polyester film is preferably 50 mol % or more, more preferably 70 mol % or more, and even more preferably 90 mol % or more. The upper limit of the content of terephthalic acid and ethylene glycol is 100 mol %.

[0026] The polyester may be a recycled polyester or a biomass-derived polyester.

[0027] <Polycondensation catalyst> The polycondensation catalyst used in polycondensing the polyester is not particularly limited, and any conventionally known compound can be used, such as a titanium compound, a germanium compound, an antimony compound, a manganese compound, an aluminum compound, a magnesium compound, and a calcium compound. Among these, at least one of titanium compounds and antimony compounds is preferred, and it is particularly preferred to use polyesters obtained using titanium compounds. Therefore, the present polyester film preferably contains at least one of a titanium compound and an antimony compound.

[0028] <Intrinsic viscosity> The intrinsic viscosity (IV) of the polyester constituting the present polyester film is preferably 0.50 dL / g or more, more preferably 0.55 dL / g or more, and even more preferably 0.60 dL / g or more. This range has the advantage of increasing the shear stress during kneading, thereby enabling high particle dispersion. The intrinsic viscosity (IV) of the polyester is, for example, 1.00 dL / g or less. In addition, when two or more polyesters with different intrinsic viscosities (IV) are used, the "intrinsic viscosity (IV) of the polyester constituting the present polyester film" refers to the intrinsic viscosity (IV) of the mixed polyesters.

[0029] When the polyester film has a multilayer structure, the intrinsic viscosity (IV) of the polyester constituting the surface layer is preferably within the above range.

[0030] <particle> Particles may be incorporated into the polyester film, primarily for the purposes of imparting lubricity and preventing scratches during each process. The type of particles contained in the polyester film is not particularly limited as long as they are particles that can impart slipperiness. Specific examples include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide, as well as crosslinked polymers such as crosslinked silicone resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, and crosslinked polyester particles, and organic particles such as calcium oxalate and ion exchange resins. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

[0031] There is no particular limitation on the shape of the particles used, and any of spherical, blocky, rod-like, flat, etc. may be used. There are also no particular limitations on the hardness, specific gravity, color, etc. Two or more types of particles of this series may be used in combination as needed.

[0032] The average particle size of the particles used is usually 5 μm or less, preferably in the range of 0.01 to 3 μm. A particle size of 5 μm or less is preferable because the surface roughness of the film does not become too rough, which is advantageous when forming a resin layer and various surface functional layers other than the resin layer in a subsequent process. Furthermore, if the average particle size is within this range, the haze is kept low, making it easier to ensure the transparency of the entire laminated polyester film. In addition, when the particles are powder, the average particle size can be the particle size at an integrated volume fraction of 50% (d50) in the equivalent spherical distribution measured using a centrifugal sedimentation particle size distribution analyzer (e.g., Shimadzu Corporation's "SA-CP3"). The average particle size of particles in a film, layer, or resin can be determined by observing 10 or more particles with a scanning electron microscope (SEM) to measure their diameters and calculating the average value. In this case, for non-spherical particles, the average of the longest and shortest diameters can be measured as the diameter of each particle.

[0033] When particles are incorporated into the present polyester film, it is preferable to provide a surface layer and an intermediate layer, and incorporate the particles into the surface layer. In this case, it is more preferable to form a multilayer structure having a particle-containing surface layer, an intermediate layer, and another particle-containing surface layer in this order. The particle content, depending on the average particle size, is typically 5000 ppm or less, preferably 30 to 800 ppm, and more preferably 50 to 400 ppm, by mass in the particle-containing layer. When particles are not contained or the particle content is low, sufficient slippage cannot be imparted, and although the transparency of the polyester film is high, the slippage may be insufficient. Therefore, measures such as laminating the present resin layer described below to improve the slippage are necessary. Furthermore, a content of 5000 ppm or less ensures sufficient transparency of the polyester film. In particular, when the present laminated polyester film is used for a face shield, the higher the transparency of the present polyester film, the better, from the viewpoint of ensuring visibility for the user.

[0034] The method for adding particles to the polyester film is not particularly limited, and any conventionally known method can be used. For example, in the case of a multi-layer polyester film, particles can be added at any stage in the production of the polyester constituting each layer, but it is preferable to add particles after the completion of the esterification or transesterification reaction.

[0035] <Other> In order to suppress the amount of precipitation of oligomer components, the film may be produced using a polyester having a low content of oligomer components as the raw material. As a method for producing a polyester having a low content of oligomer components, various known methods can be used, such as a method in which solid-state polymerization is carried out after the polyester is produced. The amount of oligomer component precipitation may be suppressed by forming the polyester film into a three-layer or more layer structure and using a polyester raw material with a low content of oligomer components as the surface layer of the polyester film. The polyester may also be obtained by carrying out the esterification or transesterification reaction, followed by melt polycondensation at a higher reaction temperature under reduced pressure.

[0036] In addition to the above-mentioned particles, conventionally known additives such as ultraviolet absorbers, antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, etc. may be added to the polyester film as needed.

[0037] The thickness of the polyester film is not particularly limited as long as it can be formed into a film. From the viewpoints of mechanical strength, handling properties, productivity, etc., the thickness is preferably 1 μm or more, more preferably 10 μm or more, even more preferably 25 μm or more, particularly preferably 50 μm or more, and is preferably 500 μm or less, more preferably 300 μm or less, even more preferably 250 μm or less, particularly preferably 200 μm or less.

[0038] <Polyester film manufacturing method> Next, specific examples of the production of the polyester film will be described, but the production method is not limited to the following examples. For example, when producing a biaxially stretched film, a preferred method is to extrude dried pellets of the polyester raw material described above as a molten sheet from a die using a melt extrusion device such as an extruder, and then cool and solidify the molten sheet on a cooling roll such as a rotating cooling drum to obtain an unstretched sheet. In this case, it is preferable to increase the adhesion between the sheet and the cooling roll to improve the flatness of the sheet, and an electrostatic application adhesion method and / or a liquid application adhesion method are preferably used.

[0039] The unstretched sheet is then stretched biaxially. In this case, the unstretched sheet is first stretched in one direction using a roll or tenter type stretching machine. The stretching temperature is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.5 to 7.0 times, preferably 3.0 to 6.0 times. Next, the film is stretched in a direction perpendicular to the first-stage stretching direction, in which case the stretching temperature is usually 70 to 170° C., and the stretching ratio is usually 3.0 to 7.0 times, preferably 3.5 to 6.0 times. Subsequently, the film is heat-treated under tension or relaxation of 30% or less at a temperature of 180 to 270°C to obtain a biaxially stretched film. This heat treatment is also called a heat setting step. The heat treatment may be performed in two or more steps at different temperatures. In the above stretching, a method of stretching in one direction in two or more stages can be adopted, in which case it is preferable to perform the stretching so that the final stretching ratios in both directions are each within the above ranges.

[0040] The polyester film can also be produced by simultaneous biaxial stretching, which involves simultaneously stretching and orienting the unstretched sheet in the machine direction (longitudinal direction) and width direction (transverse direction) under temperature control, typically at 70 to 120°C, and preferably at 80 to 110°C, with the area stretch ratio being preferably 4 to 50 times, more preferably 7 to 35 times, and even more preferably 10 to 25 times. Subsequently, the film is subjected to a heat treatment under tension or relaxation of 30% or less at a temperature of typically 170 to 250°C to obtain a stretched and oriented film. Regarding the simultaneous biaxial stretching device employing the above-mentioned stretching method, any conventionally known stretching method such as a screw method, a pantograph method, or a linear drive method can be employed.

[0041] <<Resin layer>> The present laminated polyester film comprises a polyester film and a resin layer formed from a resin composition on at least one side of the polyester film. The resin layer may be a cured resin layer. As described above, the present resin layer is formed from a resin composition (hereinafter also referred to as "the present composition").

[0042] <Resin composition> The composition contains the following compounds (A) and (B): (A) Binder resin (B) Hydrophilic compound

[0043] ((Compound (A))) The composition contains a binder resin as compound (A). By forming a resin layer containing the compound (A), a hydrophilic resin layer can be obtained, and adhesion to the adhesive of the tape can also be obtained.

[0044] The binder resin (A) is defined as a polymer compound having a number average molecular weight (Mn) of 1,000 or more as measured by gel permeation chromatography (GPC) and having film-forming properties, in accordance with the "Flow Scheme for the Safety Evaluation of Polymeric Compounds" (November 1985, sponsored by the Chemical Substances Council). Such a binder resin (A) is not particularly limited, and conventionally known binder resins can be used. Examples include polyurethane resins, polyester resins, and (meth)acrylic resins. Among these, it is preferable to use one or more resins selected from the group consisting of polyurethane resins and polyester resins, from the viewpoint of achieving the desired surface free energy described below and obtaining high adhesion to the pressure-sensitive adhesive. In the present composition, the binder resin (A) may be used alone or in combination of two or more resins.

[0045] (Polyurethane resin) The polyurethane resin is a polymer compound having a urethane bond in the molecule, and is preferably water-dispersible or water-soluble. In the present invention, a single type of polyurethane resin may be used, or two or more types of polyurethane resins may be used in combination.

[0046] In order to impart water dispersibility or water solubility, it is common and preferable to introduce hydrophilic groups such as hydroxyl groups, carboxyl groups, sulfonic acid groups, sulfonyl groups, phosphate groups, ether groups, etc. Among these hydrophilic groups, carboxyl groups and sulfonic acid groups are particularly preferred in terms of adhesion between the resin layer and the polyester film.

[0047] One method for producing polyurethane resins is by reacting a hydroxyl group-containing compound with an isocyanate. Polyols are preferably used as raw materials for the hydroxyl group-containing compound, including, for example, polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, and acrylic polyols. These compounds may be used alone or in combination.

[0048] Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol.

[0049] Polyester polyols include those obtained by reacting polycarboxylic acids or their acid anhydrides with polyhydric alcohols. Examples of polycarboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, and isophthalic acid. Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 1,8-octanediol, and 2,2, Examples of the alkyl esters include 4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-hexyl-1,3-propanediol, cyclohexanediol, bishydroxymethylcyclohexane, dimethanolbenzene, bishydroxyethoxybenzene, bisphenol A, alkylene glycol-modified bisphenol A, alkyldialkanolamines, and lactone diols.

[0050] Examples of polycarbonate polyols include polycarbonate diols obtained by dealcoholization reaction of polyhydric alcohols with dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, etc., such as poly(1,6-hexylene) carbonate and poly(3-methyl-1,5-pentylene) carbonate. Among the above, polyester polyols and polycarbonate polyols are preferred from the viewpoint of adhesion to polyester films and adhesives.

[0051] Examples of polyisocyanate compounds used to obtain polyurethane resins include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate; aliphatic diisocyanates having an aromatic ring such as α,α,α',α'-tetramethylxylylene diisocyanate; aliphatic diisocyanates such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate; and alicyclic diisocyanates such as cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and isopropylidenedicyclohexyl diisocyanate. These may be used alone or in combination.

[0052] A chain extender may be used when synthesizing the polyurethane resin. The chain extender is not particularly limited as long as it has two or more active groups that react with isocyanate groups, and generally, a chain extender having two hydroxyl groups or two amino groups can be mainly used.

[0053] Examples of chain extenders having two hydroxyl groups include glycols such as aliphatic glycols such as ethylene glycol, propylene glycol, and butanediol; aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene; and ester glycols such as neopentyl glycol hydroxypivalate.

[0054] Examples of chain extenders having two amino groups include aromatic diamines such as tolylenediamine, xylylenediamine, and diphenylmethanediamine; aliphatic diamines such as ethylenediamine, propanediamine, hexanediamine, 2,2-dimethyl-1,3-propanediamine, 2-methyl-1,5-pentanediamine, trimethylhexanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,8-octanediamine, 1,9-nonanediamine, and 1,10-decanediamine; and alicyclic diamines such as 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, dicyclohexylmethanediamine, 1,4-diaminocyclohexane, and 1,3-bisaminomethylcyclohexane.

[0055] Furthermore, as the polyurethane resin, a (meth)acrylic-modified polyurethane resin, which will be described later, may be used.

[0056] (polyester resin) The polyester resin may be composed of, as main components, for example, the following polycarboxylic acids and polyhydroxy compounds. That is, examples of polycarboxylic acids that can be used include terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4'-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaric acid, succinic acid, trimellitic acid, trimesic acid, pyromellitic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, trimellitic acid monopotassium salt, and ester-forming derivatives thereof. Examples of polyhydric hydroxy compounds that can be used include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, bisphenol A-ethylene glycol adduct, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, and potassium dimethylolpropionate. One or more of these compounds can be appropriately selected and used to synthesize a polyester resin by a conventional polycondensation reaction.

[0057] As part of the polycarboxylic acid, a product obtained by copolymerizing sulfoisophthalic acids such as 5-sodium sulfoisophthalic acid, introducing sulfonic acid groups into the polyester skeleton, and neutralizing the copolymer to make it hydrophilic is preferably used. The amount copolymerized is usually 1 to 13 mol %, preferably 3 to 10 mol %, and more preferably 5 to 9 mol %, based on the total amount of polycarboxylic acid. Introducing an appropriate amount of sulfonic acid groups can increase the hydrophilicity of the resin, making it easier to impart anti-fogging properties. Furthermore, aqueous dispersion stability can be improved.

[0058] In addition, the polyester resin may be a (meth)acrylic-modified polyester resin described below. In the present invention, it is more preferable to use a (meth)acrylic-modified polyester resin as the polyester resin from the viewpoint of excellent adhesion to the pressure-sensitive adhesive.

[0059] ((Meth)acrylic resin) The (meth)acrylic resin is a polymer made of polymerizable monomers including acrylic and methacrylic monomers. These may be homopolymers or copolymers, or copolymers with polymerizable monomers other than acrylic and methacrylic monomers. The (meth)acrylic polymer is a polymer having structural units derived from (meth)acrylic acid or (meth)acrylic acid alkyl esters. The (meth)acrylic polymer may be a polymer of at least one selected from (meth)acrylic acid and (meth)acrylic acid alkyl esters, or may be a copolymer of at least one selected from these and at least one other monomer, such as styrene or a styrene derivative, or a monomer containing a hydroxyl group. Also included are copolymers of these polymers with other polymers (e.g., polyester, polyurethane, etc.). For example, these are block copolymers and graft copolymers. That is, they can be called (meth)acrylic-modified polyester resins and (meth)acrylic-modified polyurethane resins, respectively. However, in this specification, (meth)acrylic-modified polyester resins are treated as the above-mentioned polyester resins, and (meth)acrylic-modified polyurethane resins are treated as the above-mentioned polyurethane resins. Alternatively, the term also includes a polymer (or a mixture of polymers, as the case may be) obtained by polymerizing a polymerizable monomer in a polyester solution or polyester dispersion. Similarly, the term also includes a polymer (or a mixture of polymers, as the case may be) obtained by polymerizing a polymerizable monomer in a polyurethane solution or polyurethane dispersion, and a polymer obtained by polymerizing a polymerizable monomer during polyurethane synthesis. Similarly, the term also includes a polymer (or a mixture of polymers, as the case may be) obtained by polymerizing a polymerizable monomer in another polymer solution or dispersion. These are also referred to herein as (meth)acrylic-modified polyester resins and (meth)acrylic-modified polyurethane resins, and are treated as the above-mentioned polyester resins and polyurethane resins, respectively. The above-mentioned polyesters and polyurethanes used in the (meth)acrylic resins can be appropriately selected from the polyesters and polyurethanes exemplified above for use in the binder resins. The (meth)acrylic resin may also contain a hydroxy group or an amino group in order to further improve adhesion to the polyester film.

[0060] The polymerizable monomer is not particularly limited, but particularly representative compounds include various carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, and citraconic acid, and salts thereof; various hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, monobutylhydroxyfumarate, and monobutylhydroxyitaconate; various alkyl (meth)acrylate esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and lauryl (meth)acrylate; 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and the like. Examples of suitable polyfunctional (meth)acrylates include various polyfunctional (meth)acrylates such as dipentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate; various nitrogen-containing monomers such as (meth)acrylamide, diacetone acrylamide, and (meth)acrylonitrile; hydroxyl group-containing nitrogen-containing monomers such as N-methylol (meth)acrylamide; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, and vinyltoluene; various vinyl esters such as vinyl propionate; various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane; phosphorus-containing vinyl monomers; various vinyl halides such as vinyl chloride and vinylidene chloride; and various conjugated dienes such as butadiene.

[0061] Among the above (meth)acrylic resins, polymers obtained by polymerizing polymerizable monomers including acrylic and methacrylic monomers are preferred, and it is more preferred that the polymerizable monomers include alkyl(meth)acrylic acid esters. Furthermore, the present composition containing a (meth)acrylic resin is preferably diluted with a solvent to form a coating solution as described below, and the solvent preferably contains water as the main solvent (50% by mass or more). That is, from the viewpoint of facilitating dissolution or dispersion in an aqueous coating solution, the polymerizable monomer preferably has a hydrophilic group such as a hydroxyl group or a carboxyl group. Therefore, the acrylic resin is also preferably a polymer obtained by polymerizing alkyl (meth)acrylates and polymerizable monomers including a hydroxyl group-containing monomer and a hydrophilic group-containing monomer such as a carboxyl group-containing monomer. The acrylic resin may also be an emulsion polymer obtained by polymerizing a polymerizable monomer in the presence of a surfactant.

[0062] The content of compound (A) in the composition is preferably 30 to 97% by mass, more preferably 55 to 85% by mass, and even more preferably 60 to 79% by mass, based on the total nonvolatile components of the composition. By setting the content at 30% by mass or more, the resin layer can be hydrophilic while maintaining adhesion to the pressure-sensitive adhesive. Furthermore, by setting the content at 97% by mass or less, the anti-fogging effect of the hydrophilic compound (B) can be obtained.

[0063] ((Compound (B))) The composition contains a hydrophilic compound as compound (B). By including the compound (B), the surface free energy of the resin layer surface is improved, and the formation of minute water droplets on the resin layer surface can be suppressed, thereby imparting anti-fogging properties.

[0064] Examples of the (B) hydrophilic compound include surfactants, polyether polymers having structural units derived from ethylene oxide, quaternary ammonium salt-containing compounds, hydroxyl group-containing polymers such as polyvinyl alcohol, etc. Among these, surfactants are preferred from the viewpoints of improving water permeability into the resin layer and maintaining a transparent, non-cloudy surface, and of causing a change in surface free energy, as described below, thereby providing anti-fogging properties while also providing adhesion to the pressure-sensitive adhesive.

[0065] As the surfactant, any conventionally known surfactant can be used, including, for example, anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Among these, anionic surfactants are more preferred in terms of affinity with the (A) binder resin. The surfactants may be used alone or in combination of two or more.

[0066] Examples of the anionic surfactant include alkyl sulfates such as sodium dodecyl sulfate, potassium dodecyl sulfate, and ammonium dodecyl sulfate; polyoxyethylene ether sulfates such as sodium dodecyl polyglycol ether sulfate and ammonium polyoxyethylene alkyl ether sulfate; sodium sulforicinoleate; alkyl sulfonates such as alkali metal salts of sulfonated paraffin and ammonium salts of sulfonated paraffin; fatty acid salts such as sodium laurate, triethanolamine oleate, and triethanolamine abietate; sodium benzenesulfonate and sodium dodecylbenzenesulfonate. Examples of the hydrophilic compounds (B) include alkylaryl sulfonates such as alkali metal sulfates of alkali phenol hydroxyethylene; high alkyl naphthalene sulfonates; naphthalene sulfonate-formaldehyde condensates; alkyl sulfosuccinates and dialkyl sulfosuccinates such as dioctyl sodium sulfosuccinate, sodium bis(2-ethylhexyl) sulfosuccinate, and polyoxyethylene alkyl ether sulfosuccinate sodium salt; polyoxyethylene alkyl sulfate salts; polyoxyethylene alkylaryl sulfate salts; polyoxyethylene ether phosphate salts; polyoxyethylene alkyl ether acetate salts; N-acyl amino acid salts; and N-acyl methyl taurine salts. In the present composition, the hydrophilic compounds (B) may be used alone or in combination of two or more. Among these, it is preferable to contain a dialkyl sulfosuccinate as the compound (B) from the viewpoint of achieving a balance between transparency and hydrophilicity of the resin layer and adhesion to the pressure-sensitive adhesive.

[0067] The content of compound (B) in the composition is preferably 3 to 70 mass%, more preferably 15 to 45 mass%, and even more preferably 21 to 40 mass%, based on the total nonvolatile components in the composition. By setting the content to 3 mass% or more, sufficient anti-fogging properties can be obtained. Furthermore, by setting the content to 70 mass% or less, adhesion to the pressure-sensitive adhesive can be maintained.

[0068] ((Compound (C))) The present composition preferably further contains particles (C) for the purpose of improving handling properties such as anti-blocking and slipperiness. The inclusion of the (C) particles in the composition provides excellent handleability even in applications where at least a portion of the resin layer is used in an exposed state (e.g., face shields). More specifically, the processing steps for face shields include cutting into sheets, punching into a predetermined shape, folding, etc., and in this series of steps, intermediate products during production and final products may be stacked for storage. In such cases, the sheets must be able to be handled appropriately.

[0069] Specific examples of the (C) particles are the same as those that can be contained in the polyester film described above, and among them, silica is preferred from the viewpoint of transparency. In the present composition, the (C) particles may be used alone or in combination of two or more types.

[0070] The shape of the (C) particles used may be spherical, blocky, rod-like, flat, chain-like, etc. Among these, spherical particles are preferred from the viewpoint of facilitating uniform distribution in the present composition.

[0071] The average particle size of the (C) particles is preferably 5 to 500 nm, more preferably 10 to 300 nm, and even more preferably 20 to 150 nm. If the average particle size is 500 nm or less, the transparency of the film is good, leading to improved visibility for the user. On the other hand, if the average particle size is 5 nm or more, handleability can be more effectively improved.

[0072] When the composition contains particles, the content of compound (C) in the composition is preferably 0.05 to 15% by mass, more preferably 0.1 to 10% by mass, and even more preferably 0.5 to 8% by mass, based on the total nonvolatile components of the composition. By setting the content to 0.05% by mass or more, the handling properties can be appropriately improved. Furthermore, by setting the content to 15% by mass or less, the transparency of the film is improved, leading to improved visibility for the user.

[0073] ((Compound (D))) For the purpose of leveling, the present composition preferably further contains (D) a fluorine-containing surfactant. The inclusion of (D) a fluorosurfactant in the present composition improves wettability of the composition to the polyester film, improving application properties such as enabling a uniform coating. As a result, the formation of streaks and unevenness that may occur during application can be suppressed. Minimizing such streaks and unevenness can prevent a decrease in visibility when the present laminated polyester film is used in applications where visibility is important, such as for window glass or face shields.

[0074] The (D) fluorosurfactant is preferably a nonionic surfactant containing a (poly)alkylene oxide, a (poly)glycerin, or a derivative thereof in its structure, and more preferably a surfactant having a fluorine-substituted alkyl group or a carbon-carbon triple bond structure in the hydrophobic portion.

[0075] When the composition contains a fluorosurfactant, the content of compound (D) in the composition is preferably 0.01 to 10% by mass, more preferably 0.05 to 7% by mass, and even more preferably 0.1 to 5% by mass, based on the total nonvolatile components of the composition. By setting the content to 0.01% by mass or more, the wettability of the composition to polyester films can be improved, and the formation of streaks and unevenness caused by application can be suppressed. Furthermore, by setting the content to 10% by mass or less, the impact on anti-fogging performance and easy adhesion can be reduced.

[0076] ((others)) In addition to the above compounds, additives such as crosslinking agents, antifoaming agents, coatability improvers, thickeners, organic lubricants, ultraviolet absorbers, antioxidants, foaming agents, dyes, and pigments may be further blended as appropriate within the scope of the present invention.

[0077] ((solvent)) The present composition may be diluted with a solvent to form a coating solution, that is, the present composition may be applied as a liquid coating solution to, for example, the present polyester film, and then dried and cured as necessary to form a resin layer. The components constituting the present composition (compounds (A) and (B), optionally added compounds (C) and (D), other components, etc.) may be dissolved in a solvent or dispersed in a solvent. When the composition is used as a coating solution, the concentration of all nonvolatile components in the coating solution is preferably 0.1 to 50% by mass. If the concentration is 0.1% by mass or more, a resin layer of the desired thickness can be efficiently formed. On the other hand, if the concentration is 50% by mass or less, the viscosity during coating can be reduced, thereby improving the appearance of the resin layer and increasing the stability in the coating solution.

[0078] The solvent is not particularly limited, and either water or an organic solvent can be used. From the viewpoint of environmental protection and the effects on the human body, it is preferable to prepare an aqueous coating liquid using water as the main solvent (50% by mass or more of the total solvent). The water content is preferably 60% by mass or more, more preferably 70% by mass or more. The aqueous coating liquid may contain a small amount of organic solvent. The specific amount of organic solvent should be equal to or less than the amount of water on a mass basis, for example, 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less of the solvent. Examples of organic solvents used in combination with water include alcohols such as ethanol, isopropanol, ethylene glycol, and glycerin; ethers such as ethyl cellosolve, t-butyl cellosolve, propylene glycol monomethyl ether, and tetrahydrofuran; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; and amines such as dimethylethanolamine. These can be used alone or in combination. By appropriately selecting and adding these organic solvents to the aqueous coating solution as needed, the stability and coatability of the coating solution can sometimes be improved.

[0079] Furthermore, when only an organic solvent is used as the solvent, examples of such organic solvents include aromatic hydrocarbons such as toluene, aliphatic hydrocarbons such as hexane, heptane, isooctane, esters such as ethyl acetate, butyl acetate, ketones such as ethyl methyl ketone, isobutyl methyl ketone, alcohols such as ethanol, 2-propanol, ethers such as diisopropyl ether, dibutyl ether, etc. These may be used alone or in combination, taking into consideration solubility, coatability, boiling point, etc.

[0080] It is assumed that the resin layer contains unreacted components of the composition (compounds (A) and (B), optionally added compounds (C) and (D), other components, etc.), reacted compounds, or a mixture thereof. The components in the resin layer can be analyzed by, for example, TOF-SIMS, ESCA, fluorescent X-rays, or the like.

[0081] <Method for forming resin layer> Next, a method for forming the resin layer constituting the present laminated polyester film will be described. The resin layer may be formed by applying the composition to a polyester film and, if necessary, subjecting the applied composition to treatments such as drying, curing, heat treatment, etc., preferably at least heat treatment. The method for applying the resin composition is not particularly limited, and any conventionally known coating method can be used, such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, etc.

[0082] The resin layer can be formed by in-line coating or off-line coating. The method for heat-treating the applied resin composition is not particularly limited, and when the resin layer is formed by off-line coating, the heat treatment is typically carried out at 80 to 200°C for 3 to 40 seconds, preferably at 100 to 180°C for 3 to 40 seconds. When the resin layer is formed by in-line coating, the heat treatment is typically carried out at 70 to 280°C for 3 to 200 seconds. The heat treatment may be carried out in two or more steps at different temperatures within the above temperature range. At least a part of the heat treatment may be carried out by heating during stretching. Drying and curing may be carried out simultaneously by heating in the heat treatment.

[0083] In the present invention, the resin layer is preferably formed by in-line coating, which treats the surface of a polyester film during the film-forming process. In-line coating is a method of coating within the polyester film production process, specifically, at any stage from melt extrusion of polyester to stretching, heat setting, and winding up. Typically, coating is performed on any of the following: an unstretched sheet obtained by melting and quenching, a stretched uniaxially stretched film, a biaxially stretched film before heat setting, or a film after heat setting and before winding up.

[0084] Although not limited to the following, for example, in sequential biaxial stretching, a method in which a uniaxially stretched film stretched in the longitudinal direction (machine direction) is coated and then stretched in the width direction (transverse direction) is particularly advantageous. This method has advantages in terms of production costs because film production and resin layer formation can be carried out simultaneously. In addition, because stretching is carried out after coating, the thickness of the resin layer can be changed by changing the stretch ratio, and thin film coating can be carried out more easily than with offline coating films.

[0085] Furthermore, by providing a resin layer on the film before stretching, the resin layer can be stretched together with the polyester film, thereby allowing the resin layer to be firmly adhered to the polyester film.

[0086] Furthermore, in the production of biaxially stretched polyester film, the film can be stretched while holding the edges with clips or the like, thereby restraining the film in both the longitudinal and transverse directions, and in the subsequent heat treatment (heat setting process), high temperatures can be applied while maintaining flatness and preventing wrinkles. Therefore, the heat treatment after coating can be performed at a high temperature that cannot be achieved by other methods, improving the film-forming properties of the resin layer and enabling stronger adhesion between the resin layer and the polyester film.Furthermore, a strong resin layer can be formed, and the performance such as migration resistance and moist heat resistance of various functional layers that can be formed on the resin layer can be improved.

[0087] Regardless of whether off-line coating or in-line coating is used, heat treatment and irradiation with active energy rays such as ultraviolet light may be used in combination as needed. The polyester film constituting the present laminated polyester film may be previously subjected to a surface treatment such as a corona treatment or a plasma treatment.

[0088] The thickness of this resin layer, as the thickness of the resin layer in the final laminated polyester film, is preferably 0.005 μm or more, more preferably 0.01 μm or more, and even more preferably more than 0.02 μm. The thickness of the resin layer is preferably 1 μm or less, more preferably 0.5 μm or less, and even more preferably 0.2 μm or less. If the thickness of the resin layer is within this range, excellent anti-fogging properties and easy adhesion can be imparted. The thickness of the resin layer can be measured by the method described in the Examples.

[0089] <<<Physical properties of laminated polyester film>>> Next, the physical properties of the present laminated polyester film will be described.

[0090] <<Surface free energy>> Surface free energy is composed of the sum of components of intermolecular forces. The intermolecular forces are classified into dispersion forces, orientation forces, induction forces, and hydrogen bonding forces, which respectively constitute the surface free energy as a dispersion component (Dispersion), a polar component (Polar), an induction component (Induction), and a hydrogen bonding component (Hydrogen). Among these components, the inductive component is very weak and can be ignored, and the hydrogen bonding component can be grouped into the polar component.

[0091] In the present invention, the surface free energy γ SV Each component (variance component γ SV d and polar component γ SV p ) is a value determined by the following measurement and calculation methods. First, the following γ LV1 , γ LV1 d and γ LV1 p The contact angle (θ1) between the first liquid, whose value is known, and the surface of the resin layer to be measured is measured, and the following γ LV2 , γ LV2 d and γ LV2p The contact angle (θ2) between the second liquid, the contact angle of which is known, and the surface of the resin layer to be measured is measured. Next, these values ​​are substituted into the following equations (I-1) and (I-2), and the surface free energy γ of the resin layer surface to be measured is calculated from the simultaneous equations (I-1) and (I-2) below. SV The variance component of γ SV d and the polar component γ SV p The units are mN / m.

[0092] (γ SV d γ LV1 d ) 1 / 2 +(γ SV p γ LV1 p ) 1 / 2 =γ LV1 (1+cosθ1) / 2 (I-1) (γ SV d γ LV2 d ) 1 / 2 +(γ SV p γ LV2 p ) 1 / 2 =γ LV2 (1+cosθ2) / 2 (I-2)

[0093] gamma SV d : Surface free energy γ of the resin layer surface SV Variance component of gamma SV p : Surface free energy γ of the resin layer surface SV Polar component of gamma LV1 : surface tension of the first liquid gamma LV2 : surface tension of the second liquid θ1: contact angle of the first liquid θ2: contact angle of the second liquid gamma LV1 d : Dispersion component of the surface tension of the first liquid gamma LV1 p : Polar component of the surface tension of the first liquid gamma LV2 d : the dispersive component of the surface tension of the second liquid gamma LV2 p : the polar component of the surface tension of the second liquid

[0094] The above formulas (I-1) and (I-2) are derived from the following Owens-Wendt-Rable-Kaelble (OWRK) theoretical formula and the following Young's formula. Theoretical formula of OWRK: gamma SL =γ SV +γ LV -2(γ SV d γ LV d ) 1 / 2 -2(γ SV p γ LV p ) 1 / 2 Young's formula: gamma SV =γ SL +γ LV cosθ (where, γ SL is the interfacial tension between the resin layer surface and the liquid.)

[0095] In the present invention, the components of the surface free energy γ1 calculated from the contact angle 1 second after the liquid contacts the resin layer surface are respectively defined as the dispersion component γ1 d , polar component γ1 p It was decided. Then, each component of the surface free energy γ2 calculated from the contact angle 30 seconds after the liquid contacted the resin layer surface was defined as the dispersion component γ2 d , polar component γ2 p It was decided.

[0096] The present laminated polyester film satisfies the relationships of the following formulas (1) and (2). γ1 p≧20.0 mN / m (1) (γ2 d / γ2 p ) ≥ 0.91 (2) (However, γ1 p represents the polar component of the surface free energy of the resin layer surface, calculated from the contact angle 1 second after the liquid contacts the resin layer surface, and γ2 d and γ2 p represent the dispersive component and polar component of the surface free energy of the resin layer surface, respectively, calculated from the contact angle 30 seconds after a liquid comes into contact with the resin layer surface.

[0097] The above formula (1) will be explained. The polar component γ1 of the surface free energy of the resin layer surface is calculated from the contact angle 1 second after the liquid contacts the resin layer surface. p However, if the surface tension is 20.0 mN / m or more, the surface free energy is sufficient, and water droplets spread on the surface of the resin layer, preventing the formation of minute droplets. In other words, excellent anti-fogging properties can be achieved. Since fogging due to breath occurs immediately after breath droplets come into contact with the resin layer, it is presumed that the surface free energy after 1 second is important. From this point of view, the polar component γ1 p is preferably 25.0 mN / m or more, and more preferably 28.0 mN / m or more. In addition, from the viewpoint of easily achieving adhesion with the adhesive, the polar component γ1 p is preferably 50.0 mN / m or less, more preferably 45.0 mN / m or less, and even more preferably 40.0 mN / m or less.

[0098] The above formula (2) will be explained. The dispersion component γ2 of the surface free energy of the resin layer surface is calculated from the contact angle 30 seconds after the liquid contacts the resin layer surface. d and polar component γ2 p The ratio (γ2 d / γ2 p ) is 0.91 or more, excellent adhesive properties can be exhibited. The component ratio (γ2 d / γ2 pAlthough the mechanism by which excellent adhesion can be achieved by setting the γ2 ratio to 0.91 or more is not clear, it is assumed that it is related to the ratio of the dispersion component and polar component of the surface free energy of the adhesive layer that can be laminated on the resin layer. Specifically, the dispersion component γ2 of the surface free energy of the resin layer d and polar component γ2 p The ratio (γ2 d / γ2 p ) and the ratio of the dispersion component to the polar component of the surface free energy of the adhesive layer, the closer they are, and it is estimated that this can increase the adhesion between the resin layer and the adhesive. In many cases, the dispersion component of the surface free energy of the adhesive layer is higher, so the component ratio (γ2 d / γ2 p ) is also preferably high. In addition, since adhesion to a pressure-sensitive adhesive is a phenomenon that occurs over a longer period of contact rather than immediately after application, we believe that the adhesiveness of a resin layer can be evaluated by considering the value 30 seconds after contact with the liquid, rather than the value 1 second after contact. From this perspective, the ratio (γ2 d / γ2 p ) is preferably 0.93 or more, more preferably 0.95 or more. In addition, from the viewpoint of compatibility with anti-fogging performance, the ratio (γ2 d / γ2 p ) is preferably 2.0 or less, more preferably 1.6 or less, and even more preferably 1.4 or less.

[0099] The present laminated polyester film preferably further satisfies the relationship of the following formula (3). (γ2 d / γ2 p )-(γ1 d / γ1 p ) ≥ 0.02 (3) (However, γ1 d represents the dispersion component of the surface free energy of the resin layer surface, calculated from the contact angle 1 second after a liquid comes into contact with the resin layer surface. Usually, the anti-fogging resin layer containing a hydrophilic compound spreads water droplets after contact with water, so γ1 pthan γ2 p is higher, ((γ2 d / γ2 p )-(γ1 d / γ1 p On the other hand, by using the above-mentioned component composition of the resin layer, γ1 p than γ2 p is smaller, making it possible to satisfy formula (3). This demonstrates that excellent adhesion to adhesives can be achieved while maintaining anti-fogging properties. From this perspective, the above ((γ2 d / γ2 p )-(γ1 d / γ1 p )) is more preferably 0.04 or more, and even more preferably 0.06 or more. In addition, the above ((γ2 d / γ2 p )-(γ1 d / γ1 p )) is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.2 or less, from the viewpoint of achieving both anti-fogging properties and easy adhesion.

[0100] The dispersion component γ1 of the surface free energy of the resin layer surface, calculated from the contact angle 1 second after the liquid comes into contact with the resin layer surface d From the viewpoint of increasing the surface free energy of the resin layer, the dispersion component γ1 is preferably 10.0 mN / m or more, more preferably 20.0 mN / m or more, and even more preferably 25.0 mN / m or more. d The upper limit is not particularly limited, and is about 50.0 mN / m. In addition, the dispersion component γ1 of the surface free energy of the resin layer surface, calculated from the contact angle 1 second after the liquid contacts the resin layer surface, d and polar component γ1 p The ratio (γ1 d / γ1 p From the viewpoint of the adhesive's ability to easily blend in over a short period of time, the ratio (γ1 d / γ1 pThe upper limit of ) is not particularly limited and is about 1.5.

[0101] The dispersion component γ2 of the surface free energy of the resin layer surface, calculated from the contact angle 30 seconds after the liquid contacts the resin layer surface d In order to satisfy the above formula (2) and to enhance adhesion to the adhesive, the dispersion component γ2 is preferably 28.0 mN / m or more, more preferably 30.0 mN / m or more, and even more preferably 31.0 mN / m or more. d is preferably 50.0 mN / m or less, more preferably 45 mN / m or less, and even more preferably 40 mN / m or less. In addition, the polar component γ2 of the surface free energy of the resin layer surface, calculated from the contact angle 30 seconds after the liquid contacted the resin layer surface, p From the viewpoint of long-term anti-fogging performance, the polar component γ2 is preferably 18.0 mN / m or more, more preferably 23.0 mN / m or more, and even more preferably 26.0 mN / m or more. On the other hand, from the viewpoint of satisfying the above formula (2) and obtaining adhesion to the pressure-sensitive adhesive, the polar component γ2 p is preferably 45.0 mN / m or less, more preferably 40.0 mN / m or less, and even more preferably 35.0 mN / m or less.

[0102] The surface free energy of the resin layer surface can be adjusted by the composition and content of the present composition, the thickness of the present resin layer, and the like. The surface free energy of the resin layer surface can be measured by the method described in the Examples.

[0103] <<Water droplet contact angle>> The water droplet contact angle 1 second after contact of a water droplet with the resin layer surface is preferably 45 degrees or less, more preferably 43 degrees or less, and even more preferably 40 degrees or less. If the water droplet contact angle is 45 degrees or less, the resin layer surface becomes hydrophilic and the anti-fogging performance is good. The lower limit of the water droplet contact angle is not particularly limited, but is preferably 1 degree or more, more preferably 5 degrees or more. Furthermore, the water droplet contact angle 30 seconds after contact of a water droplet with the resin layer surface is preferably 36 degrees or less, more preferably 35 degrees or less, and even more preferably 34 degrees or less. If the water droplet contact angle is 36 degrees or less, the anti-fogging performance can be maintained even after a certain period of time has passed. The lower limit of the water droplet contact angle is not particularly limited, but is preferably 5 degrees or more, more preferably 20 degrees or more.

[0104] The water droplet contact angle can be adjusted by the composition and content of the present composition, the thickness of the present resin layer, and the like. The water droplet contact angle can be measured by the method described in the Examples.

[0105] <<Tape adhesion strength>> The adhesive strength between the resin layer of the present laminated polyester film and the tape (tape adhesive strength) is preferably 4000 mN / cm or more, more preferably 4100 mN / cm or more, and even more preferably 4200 mN / cm or more. If the tape adhesive strength is 4000 mN / cm or more, it can be said that the adhesiveness to the tape (adhesive, adhesive layer) is good, and the present laminated polyester film can be said to have good adhesive properties. The upper limit of the tape adhesive strength is not particularly limited, but it is preferably 6000 mN / cm or less.

[0106] The adhesive strength of the tape can be adjusted by the composition and content of the present composition, the thickness of the present resin layer, and the like. The adhesive strength of the tape can be measured by the method described in the Examples.

[0107] <<<Applications of laminated polyester film>>> The present resin layer is characterized in that it can exhibit excellent anti-fogging properties and easy adhesion by satisfying a specific relational expression relating to the surface free energy of the resin layer surface. In particular, by taking into consideration each component of the surface free energy (dispersion component and polar component), it has become possible to achieve both anti-fogging performance and easy adhesion performance.

[0108] The present laminated polyester film can be used in various applications for the purpose of improving anti-fogging properties, and the applications are not particularly limited, but can be used for, for example, windows, mirrors, lenses, goggles, masks, shields, etc. In particular, since it also has good adhesive properties that allow tape to adhere to it, it can be suitably used in applications where at least a part of the resin layer is provided with a pressure-sensitive adhesive layer (adhesive layer). More specifically, an example of such an application, in which part of the surface of the resin layer is attached to something with double-sided tape or the like, is a face shield. Therefore, the present laminated polyester film is particularly preferably used for face shields.

[0109] An example of a face shield 1 according to an embodiment of the present invention is shown in Fig. 1. As shown in Fig. 1, the face shield 1 is detachably attached via a connecting portion 14 to a mask 2, preferably a nonwoven fabric mask, for covering the area around the user's mouth and nose, and is preferably used to cover the area around the user's eyes. As shown in FIG. 2, the face shield 1 preferably has a resin layer 12 laminated on a polyester film 13, and an adhesive layer 11 provided on at least a portion of the resin layer 12. As shown by the dotted line in FIG. 2 , the adhesive layer 11 preferably also functions as part of a connecting portion 14 for attaching the mask 2. The connecting portion 14 is preferably a tape having the adhesive layer 11, and the tape is more preferably a double-sided tape. The surface of the double-sided tape facing the mask 2 preferably has a hook-like shape, such as the hook-and-loop fastener (mechanical fastener) described in, for example, JP 2015-142654 A (see particularly Figures 3, 5, and 6 of the publication). The specific form of the adhesive layer 11 is not particularly limited, and examples include an acrylic adhesive layer, a urethane adhesive layer, a silicone adhesive layer, and a synthetic rubber adhesive layer. Among these, acrylic adhesives are preferred from the viewpoint of exhibiting favorable adhesive strength and durability. However, the face shield according to the embodiment of the present invention is not limited to the one shown in FIG. 1 or FIG.

[0110] <<<Term Explanation>>> In the present invention, the term "film" includes the term "sheet", and the term "sheet" includes the term "film". In the present invention, when it is stated that "X to Y" (X and Y are any numbers), unless otherwise specified, it means "X or more and Y or less", and also means "preferably larger than X" or "preferably smaller than Y". Furthermore, when it is stated that the amount is "X or more" (X is any number), it also means that the amount is "preferably greater than X" unless otherwise specified, and when it is stated that the amount is "Y or less" (Y is any number), it also means that the amount is "preferably smaller than Y" unless otherwise specified. [Example]

[0111] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples as long as it does not deviate from the gist of the present invention.

[0112] <Evaluation method> (1) Intrinsic viscosity (IV) of polyester 1 g of polyester, from which components incompatible with the polyester had been removed, was precisely weighed and dissolved in 100 mL of a 50 / 50 (mass ratio) phenol / tetrachloroethane mixed solvent. The viscosity was measured at 30°C using a viscosity measuring device "VMS-022UPC·F10" (manufactured by Rigo Co., Ltd.).

[0113] (2) Average particle size The average particle size of particles was determined by observing 10 or more particles with a scanning electron microscope (SEM), measuring the particle diameters, and averaging the measured diameters. In the case of non-spherical particles, the average of the longest and shortest diameters was measured as the diameter of each particle.

[0114] (3) Resin layer thickness The surface of the resin layer was stained with RuO4 and embedded in epoxy resin. Then, ultrathin sections were prepared and stained with RuO4, and the cross-sections of the resin layer were analyzed using a transmission electron microscope (TEM) (Hitachi High-Technologies Corporation, H-7650, accelerating voltage 100 kV).

[0115] (4) Surface free energy of the resin layer surface The static contact angles of the resin layer surface of the film sample, which had been conditioned for 24 hours or more at 23°C and 50% RH, were measured using an automatic contact angle meter (DataPhysics, model "OCA20") for water, methylene iodide, and n-hexadecane. Note that the droplet volume was 2 μL. Using the obtained contact angle and the surface tension component values ​​of each liquid (Table 1), the polar and dispersive components of the surface free energy of the resin layer surface were calculated using the Owens-Wendt-Rable-Kaelble (OWRK) theoretical formula. The contact angle was measured 1 second and 30 seconds after the liquid contacted the surface of the resin layer.

[0116] [Table 1]

[0117] (5) Water droplet contact angle on the resin layer surface The contact angle of the resin layer surface of a film sample that had been conditioned for 24 hours or more in an environment of 23°C and 50% RH was measured using an automatic contact angle meter (manufactured by DataPhysics, model "OCA20") by contacting a 2 μL water droplet with the resin layer surface, and the water droplet contact angle was measured 1 second and 30 seconds later.

[0118] (6) Anti-fogging test (exhalation) In an environment of 23°C and 50% RH, the film was held approximately 5 cm from the face, and the wearer exhaled on it, and the degree of fogging was visually evaluated according to the following evaluation criteria. ○: No visible clouding of the film ×: Cloudiness of the film was visible

[0119] (7) Anti-fogging test (40°C water) The resin layer was exposed to a water bath at 40°C for 10 seconds and 1 minute, and evaluated according to the following criteria. ○: Visibility through the film was not affected △: Blurring was visible due to the water film that formed, but visibility through the film was good. ×: The formed water droplets caused fogging and obstructed the view through the film.

[0120] (8) Tape adhesion A 24mm-wide double-sided adhesive tape (3M "Scotch 665-3-24", acrylic adhesive) was laminated to a 100μm-thick polyester film (Mitsubishi Chemical T100-100) that had not been surface-treated. The other side of the double-sided adhesive tape was pressed back and forth onto the resin layer surface with a 2kg rubber roller. After leaving the film at room temperature for 1 hour, the peel strength was measured. The peel strength was measured using a Shimadzu AGX-plus at a 180° peel angle at a tensile speed of 300mm / min. The surface free energy of the adhesive surface of the double-sided adhesive tape was calculated from the contact angle 30 seconds after contact with each liquid using the same method as in (4) above. The surface free energy of the adhesive surface of the double-sided adhesive tape was found to be the following value. Dispersion component: 28.2mN / m Polar component: 1.9mN / m Dispersion component / polar component: 14.84

[0121] <Materials used> The polyesters used in the examples and comparative examples are as follows:

[0122] [Polyester (A)] The starting materials were 100 parts by mass of dimethyl terephthalate and 55 parts by mass of ethylene glycol. 0.04 parts by mass of magnesium acetate tetrahydrate was added to the reactor as a catalyst. The reaction was initiated at 150°C and gradually increased to 230°C after 3 hours as methanol was distilled off. After 4 hours, the transesterification reaction was essentially complete. 0.02 parts by mass of ethyl acid phosphate was added to the reaction mixture, followed by 0.04 parts by mass of antimony trioxide. The polycondensation reaction was carried out for 4 hours. The temperature was gradually increased from 230°C to 280°C. Meanwhile, the pressure was gradually reduced from atmospheric pressure to a final value of 0.3 mmHg. Due to changes in the stirring power of the reactor, the reaction was terminated at a point corresponding to an intrinsic viscosity of 0.65 dL / g. The polymer was discharged under nitrogen pressure, yielding polyester (A) with an intrinsic viscosity of 0.65 dL / g.

[0123] [Polyester (B)] The starting materials were 100 parts by mass of dimethyl terephthalate and 45 parts by mass of ethylene glycol. 0.06 parts by mass of magnesium acetate tetrahydrate was added to the reactor as a catalyst. The reaction was initiated at 150°C and gradually increased to 230°C after 3 hours as methanol was distilled off. After 4 hours, the transesterification reaction was essentially complete. 0.03 parts by mass of ethyl acid phosphate was added to the reaction mixture, followed by 0.2 parts by mass of silica particles with an average particle size of 2.7 μm dispersed in ethylene glycol and 0.03 parts by mass of antimony trioxide. The polycondensation reaction was carried out for 4 hours. The temperature was gradually increased from 230°C to 280°C. Meanwhile, the pressure was gradually reduced from atmospheric pressure to a final value of 0.3 mmHg. Due to changes in the stirring power of the reactor, the reaction was terminated at a point corresponding to an intrinsic viscosity of 0.65 dL / g. The polymer was discharged under nitrogen pressure, yielding polyester (B) with an intrinsic viscosity of 0.65 dL / g.

[0124] Resin compositions obtained by stirring and mixing the compositions shown in Table 2 below were diluted with water to prepare coating solutions 1 to 11. The compounds used are as follows.

[0125] [Compound (A): Binder resin (IA)] Aqueous dispersion of polyester-based urethane resin polymerized with the following composition Isophorone diisocyanate unit: terephthalic acid unit: isophthalic acid unit: ethylene glycol unit: diethylene glycol unit: dimethylolpropionic acid unit = 12:19:18:21:25:5 (mol%)

[0126] [Compound (A): Binder resin (IB)] Aqueous dispersion of polyester-based urethane resin polymerized with the following composition Hexamethylene diisocyanate: adipic acid: hexanediol: propylene glycol-modified bisphenol A: dimethylolpropionic acid = 31:16:31:20:2 (mol%)

[0127] [Compound (A): Binder resin (IC)] A water dispersion of a mixture of a polycarbonate-based urethane resin and a (meth)acrylate compound having the following composition: A mixture of 50 parts by mass of a polyurethane (meth)acrylate resin formed from a polyhexamethylene carbonate diol unit having a molecular weight of 1100, a dimethylolpropionic acid unit, a hydrogenated xylylene diisocyanate unit, and a dipentaerythritol pentaacrylate unit in a ratio of 11:7:40:42 (mol%), 27 parts by mass of dipentaerythritol hexaacrylate, and 23 parts by mass of trimethylolpropane triacrylate.

[0128] [Compound (A): Binder resin (ID)] Aqueous dispersion of acrylic-modified polyester resin with the following composition: Aqueous dispersion of acrylic-modified polyester resin formed from 42 parts by mass of polyester resin formed from (acid component) isophthalic acid / / (diol component) diethylene glycol / neopentyl glycol = 100 / / 70 / 30 (mol%) and 58 parts by mass of polymethyl methacrylate

[0129] [Compound (A): Binder resin (IE)] Acrylic resin, an emulsion polymer of ethyl acrylate / methyl methacrylate = 35 / 65 (mol%) (emulsifier: nonionic surfactant)

[0130] [Compound (A): Binder resin (IF)] Aqueous dispersion of polyester resin copolymerized with the following composition Monomer composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid / / (diol component) ethylene glycol / 1,4-butanediol / diethylene glycol = 56 / 40 / 4 / / 70 / 20 / 10 (mol%)

[0131] [Compound (A): Binder resin (IG)] Aqueous dispersion of acrylic resin polymerized with the following composition Emulsion polymer of ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylolacrylamide / acrylic acid = 65 / 21 / 10 / 2 / 2 (mass%) (emulsifier: anionic surfactant)

[0132] [Compound (B): Hydrophilic compound (II)] Sodium dioctyl sulfosuccinate

[0133] [Compound (C): Particle (III)] Spherical silica particles with an average particle size of 0.07 μm

[0134] [Compound (D): Fluorocarbon surfactant (IV)] A fluorine-based nonionic surfactant with a structure that has a branched perfluoroalkenyl group in the hydrophobic group and a polyethylene oxide chain (average chain length 12 units) in the hydrophilic group.

[0135] Example 1 The outermost layer (surface layer) was made of a mixed material containing 92% and 8% by mass of polyesters (A) and (B), while the middle layer was made of polyester (A) alone. The outermost layer and middle layer materials were fed into two extruders, melted at 285°C, and then co-extruded onto a cooling roll set at 40°C in a two-type, three-layer structure (surface layer / middle layer / surface layer = 8 / 84 / 8 output), followed by cooling and solidification to obtain an unstretched sheet. The film was then stretched 3.3 times in the longitudinal direction while passing through a group of heated rolls at 85°C to produce a uniaxially stretched film. Coating Solution 1, having the composition shown in Table 2 below, was applied to one side of the uniaxially stretched film. The film was then introduced into a tenter stretching machine and stretched 4.3 times in the width direction at 100°C. After further heat treatment at 235°C, the film was subjected to a 2% relaxation treatment in the width direction to produce a laminated polyester film with a resin layer thickness of 0.02 μm and a polyester film thickness excluding the resin layer of 50 μm. The evaluation results are shown in Table 3.

[0136] Examples 2 to 11 A laminated polyester film was obtained in the same manner as in Example 1, except that the coating liquid shown in Table 2 was used and the thickness of the resin layer was changed to the value shown in Table 3. The evaluation results are shown in Table 3.

[0137] (Comparative Example 1) Except for not providing a resin layer, a polyester film was obtained in the same manner as in Example 1. The evaluation results are shown in Table 3.

[0138] (Comparative Examples 2 to 4) A laminated polyester film was obtained in the same manner as in Example 1, except that the coating liquid shown in Table 2 was used and the thickness of the resin layer was changed to the value shown in Table 3. The evaluation results are shown in Table 3.

[0139] [Table 2]

[0140] [Table 3]

[0141] As shown in the results in Table 3, this laminated polyester film satisfied the formulas (1), (2), and (3), and had excellent anti-fogging properties against exhaled breath and excellent tape adhesion. Furthermore, the films of Examples 1 to 3 and 10, which had a water droplet contact angle of 36 degrees or less after 30 seconds, still had excellent anti-fogging properties even after a long period of time, such as 1 minute. On the other hand, Comparative Example 1, which did not have a resin layer and did not satisfy formula (1), did not have anti-fogging properties. Furthermore, Comparative Examples 2 to 4, which did not satisfy formula (2), were films that were excellent in anti-fogging properties but had poor tape adhesion. [Industrial Applicability]

[0142] The laminated polyester film of the present invention has excellent anti-fogging properties and can be used for windows, mirrors, lenses, goggles, masks, shields, etc. Furthermore, the laminated polyester film of the present invention has good adhesive properties that allow tape to adhere to it, and therefore can be used in a manner in which a part of the surface of the resin layer is attached to something with double-sided tape or the like. Therefore, the laminated polyester film of the present invention can be suitably used as a face shield. [Explanation of symbols]

[0143] 1 face shield 2. Mask 11 Adhesive layer 12 Resin layer 13 Polyester film 14 Connecting part

Claims

1. A laminated polyester film comprising a polyester film and a resin layer formed on at least one surface of the polyester film using a resin composition, the resin composition contains (A) a binder resin and (B) a hydrophilic compound, A laminated polyester film that satisfies the relationships of the following formulas (1) and (2) and further satisfies the relationship of the following formula (3): c １ ｐ ≧20.0mN / m・・・(1) (c) ２ ｄ / c ２ ｐ )≧0.91・・・(2) (However, γ １ ｐ represents the polar component of the surface free energy of the resin layer surface, calculated from the contact angle 1 second after a liquid contacts the resin layer surface, and γ ２ ｄ and γ ２ ｐ represent the dispersive component and polar component of the surface free energy of the resin layer surface, respectively, calculated from the contact angle 30 seconds after a liquid comes into contact with the resin layer surface. (γ 2 d / γ 2 p ) - (γ 1 d / γ 1 p )≧0.02...(3) (where γ 1 d represents the dispersion component of the surface free energy of the resin layer surface, calculated from the contact angle 1 second after a liquid comes into contact with the resin layer surface.)

2. A laminated polyester film comprising a polyester film and a resin layer formed on at least one surface of the polyester film using a resin composition, the resin composition contains (A) a binder resin and (B) a hydrophilic compound, the water droplet contact angle 1 second after contacting the resin layer surface is 45 degrees or less, A laminated polyester film satisfying the relationships of the following formulas (1) and (2): c １ ｐ ≧20.0mN / m・・・(1) (c) ２ ｄ / c ２ ｐ )≧0.91・・・(2) (However, γ １ ｐ represents the polar component of the surface free energy of the resin layer surface, calculated from the contact angle 1 second after a liquid contacts the resin layer surface, and γ ２ ｄ and γ ２ ｐ represent the dispersive component and polar component of the surface free energy of the resin layer surface, respectively, calculated from the contact angle 30 seconds after a liquid comes into contact with the resin layer surface.

3. A laminated polyester film comprising a polyester film and a resin layer formed on at least one surface of the polyester film using a resin composition, the resin composition contains (A) a binder resin and (B) a hydrophilic compound, the water droplet contact angle 30 seconds after contacting the surface of the resin layer is 36 degrees or less, A laminated polyester film satisfying the relationships of the following formulas (1) and (2): c １ ｐ ≧20.0mN / m・・・(1) (c) ２ ｄ / c ２ ｐ )≧0.91・・・(2) (However, γ １ ｐ represents the polar component of the surface free energy of the resin layer surface, calculated from the contact angle 1 second after a liquid contacts the resin layer surface, and γ ２ ｄ and γ ２ ｐ represent the dispersive component and polar component of the surface free energy of the resin layer surface, respectively, calculated from the contact angle 30 seconds after a liquid comes into contact with the resin layer surface.

4. A laminated polyester film comprising a polyester film and a resin layer formed on at least one surface of the polyester film using a resin composition, the resin composition contains (A) a binder resin and (B) a hydrophilic compound, the hydrophilic compound (B) contains a dialkyl sulfosuccinate, A laminated polyester film satisfying the relationships of the following formulas (1) and (2): c １ ｐ ≧20.0mN / m・・・(1) (c) ２ ｄ / c ２ ｐ )≧0.91・・・(2) (However, γ １ ｐ represents the polar component of the surface free energy of the resin layer surface, calculated from the contact angle 1 second after a liquid contacts the resin layer surface, and γ ２ ｄ and γ ２ ｐ represent the dispersive component and polar component of the surface free energy of the resin layer surface, respectively, calculated from the contact angle 30 seconds after a liquid comes into contact with the resin layer surface.

5. The laminated polyester film according to any one of claims 2 to 4, further satisfying the following formula (3): (c) ２ ｄ / c ２ ｐ )-(c １ ｄ / c １ ｐ )≧0.02・・・(3) (However, γ １ ｄ represents the dispersion component of the surface free energy of the resin layer surface, calculated from the contact angle 1 second after a liquid comes into contact with the resin layer surface.

6. 6. The laminated polyester film according to claim 1, wherein the resin layer surface has a water droplet contact angle of 45 degrees or less one second after contact with the water droplet.

7. 7. The laminated polyester film according to claim 1, wherein the resin layer surface has a water droplet contact angle of 36 degrees or less 30 seconds after contact with the water droplet.

8. 8. The laminated polyester film according to claim 1, wherein the binder resin (A) comprises at least one resin selected from the group consisting of polyurethane resins and polyester resins.

9. The laminated polyester film according to any one of claims 1 to 3 and 5 to 8, wherein the hydrophilic compound (B) comprises a dialkyl sulfosuccinate.

10. The laminated polyester film according to any one of claims 1 to 9, wherein the content of the binder resin (A) is 30 to 97 mass% as a non-volatile component.

11. The laminated polyester film according to any one of claims 1 to 10, wherein the resin composition further comprises (C) particles.

12. The laminated polyester film according to any one of claims 1 to 11, wherein the resin composition further comprises (D) a fluorine-containing surfactant.

13. The laminated polyester film according to any one of claims 1 to 12, further comprising an adhesive layer on at least a part of the resin layer.

14. The laminated polyester film according to any one of claims 1 to 13, which is used for a face shield.

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