White, easy-adhesive polyester film

Abstract

To provide a white, easily adhesive polyester film which has both antistatic properties and adhesion to inks and toners, and which has good adhesion to UV-curable inks, particularly during high-speed printing. [Solution] A white, highly adhesive polyester film having a coating layer on at least one side of a polyester film substrate, the coating layer having a thickness of 50 to 900 nm, the coating layer containing a cationic antistatic agent having a nitrogen element, a polyester resin, and a polyurethane resin, the nitrogen element ratio A (at%) derived from the antistatic agent and the nitrogen element ratio B (at%) derived from the polyurethane resin based on surface element distribution measurement by X-ray photoelectron spectroscopy in the coating layer satisfy the following formulas (i) and (ii), and the contact angle of the coating layer surface with water is 50° to 70°. (i) A(at%) > 0.4 (ii) 2.0 ≦ B / A ≦ 5.0

Description

[Technical Field]

[0001] The present invention relates to a white, highly adhesive polyester film. More specifically, the present invention relates to a white, highly adhesive polyester film that combines antistatic properties with adhesion to various inks and toners, and that exhibits particularly good adhesion to ultraviolet (UV)-curable inks during high-speed printing.

[0002] Because biaxially oriented polyester films have excellent properties such as mechanical properties, electrical properties, and dimensional stability, they are used as base films in many fields, including magnetic recording materials, packaging materials, electrical insulating materials, photosensitive materials, drafting materials, and photographic materials. However, when biaxially oriented polyester films are coated with ink or the like for these applications, adhesion may generally be insufficient depending on the material used (see, for example, Patent Document 1).

[0003] Therefore, one method of imparting adhesion to the surface of a biaxially stretched polyester film is known to involve applying a coating liquid containing various resin components to a polyester film before crystal orientation is complete, stretching the film in at least one direction after drying, and then subjecting the film to heat treatment to complete the crystal orientation, thereby forming a coating layer with easy adhesion properties.

[0004] In many conventional ink-adhesive polyester-coated films, a coating layer made of a specific resin is provided on the surface of a base polyester film. Examples of the resin constituting the coating layer include polyester resins, polyurethane resins, and acrylic resins, either alone or in combination, or mixtures of these resins with specific crosslinking agents (melamine, isocyanate, etc.).

[0005] However, in general, both the base polyester film and the highly adhesive polyester film provided with a coating layer for improving adhesion are prone to static electricity, which can cause problems related to passability in the film-forming process and static electricity hazards during the processing process (see, for example, Patent Document 2).

[0006] One way to improve static electricity problems is to use conductive polymers such as polyaniline and polypyrrole, or particulate carbon black, nickel, copper, or other metals in the coating layer. powder Metal oxides such as tin oxide and zinc oxide, metal-coated fibers such as fibrous brass, stainless steel, and aluminum, and scales Condition It is known to impart antistatic properties to the coating layer by incorporating conductive fillers such as graphite, aluminum flakes, copper flakes, etc.

[0007] However, in general, the conductive polymer, metal oxide, metal-coated fiber, conductive filler, etc., must be added in large amounts to the coating layer in order to achieve sufficient antistatic effects. Furthermore, adding a large amount may result in insufficient adhesion of the coating layer to ink or toner. Furthermore, there are issues such as coloring of the film and increased costs due to the high cost of conductive materials. In addition, when the substrate film is stretched, it becomes difficult for the film to follow the stretching, which may result in cracks in the coating film and other problems that may impair quality.

[0008] One known method for improving problems caused by static electricity is to incorporate a polymeric antistatic agent having at least one sulfonate group or phosphate group in the molecule into a coating agent and apply the agent to a substrate film (see, for example, Patent Document 3).

[0009] In order to obtain a sufficient antistatic effect from the polymeric antistatic agent, it is necessary to increase the number average molecular weight or to increase the amount added to the coating layer, but in general, neither method has any beneficial effect on the adhesion of the coating layer to ink or toner.

[0010] In recent years, the printing industry has been moving toward higher printing speeds in order to improve productivity. As printing speeds increase with UV-curable inks, the time required from ink application to UV irradiation and the cumulative amount of UV light decrease. This means that the interaction between the ink and the polyester film and the coating layer weakens. Therefore, the coating layer must have higher adhesion to the UV-curable ink. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-223714 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-348450 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-156848 Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been made in view of the problems of the prior art. That is, an object of the present invention is to provide a white, highly adhesive polyester film that has both antistatic properties and good adhesion to inks and toners, and that has particularly good adhesion to UV-curable inks during high-speed printing.

[0013] The present inventors have investigated the causes of the above problems in order to solve the above problems, and have completed the present invention. That is, the present invention has the following configuration. 1. A polyester film substrate having a coating layer on at least one side thereof, The thickness of the coating layer is 50 to 900 nm,A white, highly adhesive polyester film, characterized in that the coating layer contains a cationic antistatic agent having a nitrogen element, a polyester resin, and a polyurethane resin, and the nitrogen element ratio A (at%) derived from the antistatic agent and the nitrogen element ratio B (at%) derived from the polyurethane resin, based on surface element distribution measurement in the coating layer by X-ray photoelectron spectroscopy, satisfy the following formulas (i) and (ii), and the contact angle of the coating layer surface with water is 50° to 70°. (i) A(at%) > 0.4 (ii) 2.0 ≦ B / A ≦ 5.0 2. The white, highly adhesive polyester film according to item 1 above, wherein the polyester film substrate contains inorganic particles and / or a thermoplastic resin incompatible with the polyester resin. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a white, highly adhesive polyester film that has both antistatic properties and good adhesion to inks and toners, and that has particularly good adhesion to UV-curable inks during high-speed printing. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is an explanatory diagram for determining the nitrogen element ratio A (at %) derived from the antistatic agent and the nitrogen element ratio B (at %) derived from the polyurethane resin based on surface element distribution measurement by X-ray photoelectron spectroscopy on the coating layer surface in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] (Polyester film base) In the present invention, the polyester resin constituting the polyester film substrate is polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polytrimethylene terephthalate, etc., as well as copolymerized polyester resins in which a portion of the diol component or dicarboxylic acid component of the above-mentioned polyester resins is replaced with a copolymerization component such as the following. For example, the copolymerization component may include diol components such as diethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, and polyalkylene glycol, and dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, 5-sodium isophthalic acid, and 2,6-naphthalenedicarboxylic acid.

[0017] In the present invention, polyester resins suitable for use in the polyester film substrate are primarily selected from polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate. Among these polyester resins, polyethylene terephthalate is most preferred in terms of the balance between physical properties and cost. Furthermore, polyester film substrates made from these polyester resins are preferably biaxially oriented polyester films, which can improve chemical resistance, heat resistance, mechanical strength, stiffness, and the like.

[0018] The catalyst for polycondensation used in producing the polyester resin is not particularly limited, but antimony trioxide is preferred because it is inexpensive and has excellent catalytic activity. It is also preferred to use a germanium compound or a titanium compound. More preferred polycondensation catalysts include catalysts containing aluminum and / or its compound and a phenolic compound, catalysts containing aluminum and / or its compound and a phosphorus compound, and catalysts containing an aluminum salt of a phosphorus compound.

[0019] The base polyester film used in the present invention may have a single-layer structure or a multi-layer structure, but it is preferable that some or all of the layers are opaque. The optical density, which indicates the opacity of the polyester film, is 0.3 or more, preferably 0.3 to 4.0, and particularly preferably 0.5 to 3.0. An optical density of 0.3 or more is preferable because when printing is performed on the surface of the resulting polyester-based coated film, the printing effect becomes clear. Furthermore, an optical density of 4.0 or less is preferable because better printing effects can be expected.

[0020] While there are no particular limitations on the method for obtaining an optical density within the above range, it can be preferably achieved by incorporating inorganic particles or a thermoplastic resin incompatible with the polyester resin into the polyester resin. The content of these is also not particularly limited, but in the case of inorganic particles, it is preferably 5 to 35 mass% relative to the resulting polyester, and particularly preferably 8 to 25 mass%. On the other hand, when an incompatible thermoplastic resin is incorporated, it is preferably 5 to 35 mass% relative to the polyester, and particularly preferably 8 to 28 mass%. Furthermore, when inorganic particles and a thermoplastic resin incompatible with the polyester resin are used in combination, it is preferable that the total amount of these components be 40 mass% or less relative to the polyester film, from the viewpoints of film strength, stiffness, and film formation stability.

[0021] The layer structure of the base polyester film in the present invention may be a single layer structure or a laminate structure, but a preferred embodiment is a laminate structure of X layer / Y layer / X layer, in which the X layer contains inorganic particles and the Y layer contains microvoids. By disposing a layer containing inorganic particles in the X layer, which is the surface layer, it is possible to improve the slipperiness, i.e., handleability, and hiding power of the film. By incorporating microvoids only in the Y layer, which is the inner layer, it is possible to ensure the strength of the film surface while exhibiting cushioning properties. While the method for forming the laminate structure is not particularly limited, coextrusion is preferred from the viewpoints of stability during production and processing costs.

[0022] The inorganic particles contained in the X layer are preferably 2.5 to 70.0% by mass, particularly preferably 4.0 to 60.0% by mass, and further preferably 6.0 to 50.0% by mass, based on the polyester. Fat is The content is preferably 5 to 35% by mass, particularly preferably 8 to 28% by mass, based on the polyester.

[0023] The thickness ratio of each layer in the X layer / Y layer / X layer laminate structure is preferably in the range of 0.5 / 9 / 0.5 to 2 / 6 / 2, more preferably in the range of 1 / 8 / 1 to 1.5 / 7 / 1.5, from the viewpoints of film strength, stiffness, and film formation stability.

[0024] The inorganic particles used are not particularly limited, but inorganic particles with an average particle size of 0.1 to 4.0 μm are preferred, and inorganic particles with an average particle size of 0.3 to 1.5 μm are particularly preferred. Specifically, white pigments such as titanium oxide, barium sulfate, calcium carbonate, and zinc sulfide are preferred, and these may be mixed. Furthermore, inorganic particles commonly contained in films, such as silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, calcium fluoride, and calcium sulfate, may also be used in combination.

[0025] Furthermore, the thermoplastic resin incompatible with the polyester resin is not particularly limited, but examples thereof include, when mixed with polyethylene terephthalate resin, polyolefin resins such as polystyrene resin, polyethylene resin, polypropylene resin, and polymethylpentene resin, cyclic polyolefin resin, acrylic resin, phenoxy resin, polyphenylene oxide resin, and polycarbonate resin. These thermoplastic resins may be mixed or modified. Naturally, they may also be used in combination with the inorganic particles. Needless to say, various whitening agents may be added as needed.

[0026] Furthermore, the polyester film used in the present invention has an apparent density of 0.3 to 1.3 g / cm 3It is preferable that the polyester film is a microvoid-containing polyester film having the formula:

[0027] In addition, from the viewpoint of achieving both cushioning properties and surface peel strength, a microvoid-containing polyester film having a void lamination density of 0.20 / μm or more, preferably 0.25 / μm or more, and more preferably 0.30 / μm or more is also preferred. As a result, the resulting polyester-based coated film has excellent print clarity and processing characteristics during printing. Here, the void lamination density (cavities / μm) is defined by the formula: number of cavities in the film thickness direction (cavities) / film thickness (μm). From the viewpoint of void development efficiency, the upper limit of the void lamination density is preferably 0.80 / μm, more preferably 0.55 / μm. Methods for adjusting the void density within the above range include, but are not limited to, adjusting the amount, type, viscosity, etc. of the incompatible thermoplastic resin, changing the screw shape of the extruder, or installing a static mixer in the molten resin flow path.

[0028] These microvoid-containing polyester films are particularly useful because the microvoids contained in the film cause light scattering at the interface with the polyester matrix, thereby further improving opacity and allowing the addition of the inorganic particles to be reduced. Furthermore, the inclusion of microvoids in the film makes the substrate film itself lighter, making it easier to handle, and also resulting in significant economic benefits such as reduced raw material costs and transportation costs.

[0029] As a method for obtaining such a polyester film containing microvoids, a publicly known method can be used, such as a method in which a thermoplastic resin that is incompatible with the polyester resin as described above is kneaded into a thermoplastic polyester resin matrix, and the incompatible resin is dispersed in the form of fine particles in the polyester resin, and the resulting sheet is stretched in at least one direction to generate cavities around the incompatible resin fine particles.

[0030] The thickness of the obtained microvoid-containing polyester film is preferably 5 to 300 μm, more preferably 20 to 300 μm, and even more preferably 40 to 250 μm.

[0031] The whiteness required when used in printing materials and the like can be expressed by the color b value. A higher color b value indicates a stronger yellow tinge, while a lower value indicates a stronger blue tinge. The color b value corresponds well to visual confirmation, and the color b value is preferably 4.0 or less, and more preferably 3.0 or less. A b value of 4.0 or less provides excellent whiteness, and when used in labels and the like, provides excellent clarity when printed. The lower limit of the color tone b value is preferably -5.0. A b value of -5.0 or more prevents the film from becoming too blue, allowing for a well-balanced resolution when used as a printing substrate.

[0032] (Explanation of characteristic values ​​in the present invention) The white, highly adhesive polyester film of the present invention preferably has a coating layer on at least one surface of the polyester film substrate as described above, and the coating layer preferably contains a cationic antistatic agent having a nitrogen element, a polyester resin, and a polyurethane resin. By having the cationic antistatic agent component and the polyurethane resin component present on the coating layer surface in suitable amounts and ratios and controlling the contact angle with water within a suitable range, antistatic properties and adhesion to inks and toners are simultaneously achieved, and adhesion to UV-curable inks is particularly good during high-speed printing.

[0033] The amounts of the cationic antistatic agent component and the polyurethane resin component present on the surface of the coating layer are evaluated by the peak areas of the ionized nitrogen element peak and the non-ionized nitrogen element peak in the N1s spectrum of X-ray photoelectron spectroscopy (hereinafter referred to as ESCA). In ESCA, the element species and chemical state corresponding to the peaks are identified from the peak positions of the measured spectrum. Furthermore, curve fitting of the element peaks can be performed to calculate the peak area. The coating layer of the present invention contains a cationic antistatic agent containing nitrogen and a polyurethane resin. For such a coating layer, the peaks of the ESCA N1s spectrum are exemplified as shown in Figure 1. The thin solid line in the figure represents the measured data of the N1s spectrum. Of the two peaks, (1) the peak near 402 eV on the dotted curve in the figure is the ionized nitrogen element peak, and in the present invention, it can be determined to be derived from the cationic antistatic agent. Furthermore, (2) the peak near 400 eV on the dashed curve in the figure is the non-ionized nitrogen element peak, and in the present invention, it can be determined to be derived from the polyurethane resin. Curve fitting was performed on the peaks of the spectra of all detected elements, including the N1s spectrum, and when the total peak area was taken as 100 (at%), the area ratio of (1) was expressed as the nitrogen element ratio A (at%) derived from the cationic antistatic agent, which is used as an index of the amount of the antistatic agent component present on the coating layer surface.Similarly, the area ratio of (2) was expressed as the nitrogen element ratio B (at%) derived from the polyurethane resin, which is used as an index of the amount of the polyurethane resin component present on the coating layer surface.

[0034] Furthermore, when the characteristic values ​​of the coating layer in the present invention based on the surface element distribution measurement by ESCA satisfy the following relationships (i) and (ii) and the contact angle of the coating layer surface with water is 50° to 70°, both antistatic properties and adhesion to ink and toner are achieved, and adhesion to UV-curable ink is particularly good during high-speed printing. (i) A(at%) > 0.4 (ii) 2.0 ≦ B / A ≦ 5.0

[0035] The principle of antistatic performance when using an ionic antistatic agent, including the cationic antistatic agent of the present invention, and its correlation with adhesion to ink and toner are described below. When using an ionic antistatic agent to achieve antistatic properties on a substrate surface, it is preferable to form a water network on the substrate surface, which functions to dissipate static electricity. The presence of an ionic antistatic agent on the substrate surface has the effect of attracting moisture from the air. Therefore, the greater the amount of ionic antistatic agent present on the substrate surface, the easier it is to attract moisture from the air and form a water network, thereby making it easier to achieve antistatic properties. However, on the other hand, an increase in the amount of ionic antistatic agent present on the substrate surface relatively reduces the amount of resin present. That is, in the present invention, the amount of urethane resin, which is generally considered important for adhesion to ink and toner, decreases, resulting in reduced adhesion. Therefore, it is preferable to control the amounts of ionic antistatic agent and resin (especially polyurethane resin) present on the coating layer surface within a suitable range. To form a water network even when the amount of ionic antistatic agent present on the coating layer surface is low, it is preferable to control the contact angle of the coating layer surface with water. By controlling the contact angle of the coating layer surface within a suitable range, water attracted by the antistatic agent on the coating layer surface can spread to areas where no antistatic agent is present. In other words, controlling the contact angle of the coating layer surface can assist the formation of a water network. Therefore, good antistatic properties can be obtained even with a smaller amount of antistatic agent. The effect of assisting the formation of a water network can be achieved, suppressing the spreading of excess water, thereby ensuring a suitable contact state between the ink or toner and the polyurethane resin component on the coating layer surface.

[0036] A (at%) is preferably greater than 0.4. By controlling it within this range, it becomes possible to attract moisture in the air to the coating film surface. By controlling the contact angle of the coating layer surface with water, which will be described later, within a suitable range, good antistatic properties can be obtained. It is more preferably 0.5 at% or more, and even more preferably 0.6 at% or more. However, if A (at%) is too large, it becomes difficult to satisfy the preferred range of B / A below, so it is preferably 5 at% or less, more preferably 3 at% or less, and even more preferably 2 at% or less.

[0037] B / A is preferably 2.0 to 5.0. By controlling B / A within this range and controlling the contact angle of the coating film surface with water (described later) within a suitable range, antistatic properties and adhesion to ink and toner are both achieved, and adhesion to UV-curable ink is particularly good during high-speed printing. The lower limit of B / A is more preferably 3.0 or more. On the other hand, the upper limit of B / A is more preferably 4.0 or less.

[0038] The contact angle of the coating surface with water is preferably in the range of 50° to 70°. The lower limit of the contact angle of the coating surface with water is more preferably 60° or more. On the other hand, the upper limit of the contact angle of the coating surface with water is more preferably 68° or less. By controlling the contact angle within the range of 50° to 70°, a good assisting effect for the formation of a water network on the coating surface can be obtained.

[0039] (coating layer) The white, highly adhesive polyester film of the present invention has both antistatic properties and good adhesion to inks and toners, and in order to obtain good adhesion to UV-curable inks, particularly during high-speed printing, it is preferable that a coating layer made of a nitrogen-containing cationic antistatic agent, a polyester resin, or a polyurethane resin is provided on at least one side of the film. The coating layer may be provided on both sides of the polyester film, or on only one side of the polyester film with a different resin coating layer provided on the other side.

[0040] The composition of each coating layer will be described in detail below. (Cationic antistatic agent containing nitrogen element) Examples of suitable polymers include polyethyleneimine, polydimethyldiallylammonium salts, polyalkylenepolyamine dicyanodiamide ammonium condensates, polyvinylpyridinium halides, (meth)acrylate alkyl quaternary ammonium salts, (meth)acrylamido alkyl quaternary ammonium salts, ω-chloro-poly(oxyethylene-polymethylene-alkyl quaternary ammonium salts), polyvinylbenzyltrimethylammonium salts, polystyrene-based cationic polymers, poly(meth)acrylic cationic polymers (e.g., methyl methacrylate, ethyl acrylate, 2-hydroxyethyl methacrylate, trimethylaminoethyl methacrylate chloride), polyvinylpyridine-based polymers, cyclic integral polymers, linear integral polymers, polymers of aromatic vinyl monomers having two or more pendant quaternary ammonium ion groups, and polymers having pyrrolidinium rings in the main chain. These polymers may be homopolymers or copolymers. Known copolymerizable monomers can be used to produce these polymers. In order to control the amount of antistatic agent component present on the surface of the coating layer, an antistatic agent having a linear alkyl group is preferred, and an antistatic agent having both a linear alkyl group and a quaternary ammonium salt group is more preferred.

[0041] In the present invention, the antistatic agent is preferably present on the surface of the coating layer.

[0042] Therefore, in an antistatic agent having a linear alkyl group and a quaternary ammonium salt group, the number of carbon atoms in the alkyl chain is preferably 10 to 20, more preferably 12 to 19, and particularly preferably 14 to 18. In order to control the ratio of nitrogen elements derived from the nitrogen-containing cationic antistatic agent within a suitable range based on surface element distribution measurement by ESCA, it is preferable to allow the antistatic agent to bleed out onto the coating layer surface, and in consideration of intermolecular interactions and the ease of bleed-out due to molecular length, it is preferable to set the range as described above.

[0043] Furthermore, the molecular structure of the nitrogen-containing cationic antistatic agent may contain at least one amide bond or urethane bond between the linear alkyl chain and the quaternary ammonium base.

[0044] In the above antistatic agent, the counter ion of the quaternary ammonium salt group is not particularly limited as long as it is an anionic compound, but can be appropriately selected from halogen ions, mono- or polyhalogenated alkyl ions, nitrate ions, sulfate ions, alkyl sulfate ions, sulfonate ions, and alkyl sulfonate ions, and preferably, chloroyl ions, metasulfonate ions, ethanesulfonate ions, and nitrate ions are selected.

[0045] (polyester resin) The polyester resin used to form the coating layer in the present invention is a straight-chain polyester resin. ConditionHowever, it is more preferable that the polyester resin be composed of a dicarboxylic acid and a diol having a branched structure. The dicarboxylic acid referred to here is a dicarboxylic acid whose main component is terephthalic acid, isophthalic acid, or 2,6-naphthalenedicarboxylic acid, as well as an aliphatic dicarboxylic acid such as adipic acid or sebacic acid, and an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, phthalic acid, or 2,6-naphthalenedicarboxylic acid. Furthermore, the branched glycol refers to a diol having a branched alkyl group, and examples thereof include 2,2-dimethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, 2-methyl-2-butyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-2-isopropyl-1,3-propanediol, 2-methyl-2-n-hexyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, 2-ethyl-2-n-hexyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 2-n-butyl-2-propyl-1,3-propanediol, and 2,2-di-n-hexyl-1,3-propanediol.

[0046] The dicarboxylic acid as a constituent of the polyester resin is preferably terephthalic acid or isophthalic acid. In addition to the dicarboxylic acid, 1 to 10 mol % of 5-sulfoisophthalic acid or the like may be used to impart water dispersibility to the copolymer polyester resin. Range Examples of suitable dicarboxylic acids include sulfoterephthalic acid, 5-sulfoisophthalic acid, and 5-sodium sulfoisophthalic acid. A polyester resin containing a dicarboxylic acid having a naphthalene skeleton may be used, but in order to prevent a decrease in adhesion to curable ink, the proportion of such a dicarboxylic acid is preferably 5 mol % or less of the total carboxylic acid components, and it may not be used at all.

[0047] The polyester resin may contain triols or tricarboxylic acids as constituent components to the extent that the properties of the polyester resin are not impaired.

[0048] The polyester resin may contain polar groups other than carboxyl groups. Examples include metal sulfonate groups and phosphate groups, and these groups may be present in one or more types. Methods for introducing metal sulfonate groups include using dicarboxylic acids or glycols containing metal sulfonate groups, such as metal salts of 5-sulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, and 5-[4-sulfophenoxy]isophthalic acid, or metal salts of 2-sulfo-1,4-butanediol and 2,5-dimethyl-3-sulfo-2,5-hexanediol, in an amount of 10 mol% or less, preferably 7 mol% or less, and more preferably 5 mol% or less, of the total polycarboxylic acid component or polyol component. If the amount exceeds 10 mol%, the hydrolysis resistance of the resin itself and the water resistance of the coating tend to decrease.

[0049] (Polyurethane resin) In the present invention, it is preferable that an antistatic agent is present on the surface of the coating layer, that the characteristic values ​​based on the surface element distribution measurement by ESCA satisfy a suitable relationship, and that the contact angle of the coating layer surface with water satisfies a suitable range. Therefore, it is preferable to mainly control the polarity of the polyurethane resin.

[0050] One method for controlling the polarity of a polyurethane resin is, for example, to control the structure of the polyol component used in the synthesis and polymerization of the polyurethane resin. Generally, the polarity of ester skeletons and carbonate skeletons tends to be lower than that of ether skeletons. In cases where the nitrogen element ratio derived from the cationic antistatic agent based on surface element distribution measurement by ESCA is below a suitable range, it is preferable to use a urethane resin in which the skeleton of the polyol component used in the synthesis and polymerization of the polyurethane resin is an ester skeleton or a carbonate skeleton, in order to reduce the interaction between the polyurethane resin and the cationic antistatic agent and allow the antistatic agent to be present on the surface of the coating layer. It is particularly preferable to use a urethane resin with a carbonate skeleton.

[0051] Examples of the ether skeleton polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol.

[0052] Examples of ester-skeleton polyols include polycarboxylic acids (malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, isophthalic acid, etc.) or their acid anhydrides and polyhydric alcohols (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, etc.). , 2-methyl-2,4-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 1,8-octanediol, 2,2,4-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, alkyldialkanolamines, lactonediols, etc.

[0053] The carbonate-skeleton polyol preferably contains an aliphatic polycarbonate polyol, which has excellent heat resistance and hydrolysis resistance. Examples of the aliphatic polycarbonate polyol include an aliphatic polycarbonate diol and an aliphatic polycarbonate triol, and the aliphatic polycarbonate diol is preferably used. Examples of the aliphatic polycarbonate diol used for synthesizing and polymerizing the urethane resin having a polycarbonate structure in the present invention include aliphatic polycarbonate diols obtained by reacting one or more diols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,8-nonanediol, neopentyl glycol, diethylene glycol, and dipropylene glycol with carbonates such as dimethyl carbonate, ethylene carbonate, and phosgene.

[0054] Another method for controlling the polarity of a polyurethane resin is, for example, controlling the number average molecular weight of the polyol component used in the synthesis and polymerization of the polyurethane resin. Generally, when the number average molecular weight of the polyol component used in the synthesis and polymerization of the polyurethane resin is large, the polarity of the polyurethane resin tends to be low, while when the number average molecular weight of the polyol component is small, the polarity of the polyurethane resin tends to be high. When the contact angle of the coating layer surface with water is below a suitable range, it is preferable to increase the number average molecular weight of the polyol component and reduce the polarity of the polyurethane resin. When the contact angle of the coating layer surface with water exceeds a suitable range, it is preferable to reduce the number average molecular weight of the polyol component and increase the polarity of the polyurethane resin. As an example of the number average molecular weight, when the polyol used in the synthesis and polymerization of the polyurethane resin is an ester-skeleton polyol, the number average molecular weightis preferably 1000 to 2400, more preferably 1200 to 2200, and particularly preferably 1400 to 2200. In the case of a carbonate skeleton polyol, the number average molecular weight is preferably 500 to 1800, more preferably 600 to 1600, and particularly preferably 700 to 1400.

[0055] One method for controlling the polarity of a polyurethane resin is to control the amount of urethane groups in the molecule. Generally, the more urethane groups in the molecule, the higher the polarity of the polyurethane resin, and the greater the amount of polyurethane resin component present on the coating layer surface. On the other hand, the fewer urethane groups in the molecule, the lower the polarity of the polyurethane resin, and the greater the amount of polyurethane resin component present on the coating layer surface. Therefore, controlling the amount of urethane groups in the molecule changes the amount of antistatic agent component present on the coating layer surface, the amount of polyurethane resin component present, and even the water contact angle of the coating layer surface. In the present invention, for example, to set the characteristic values ​​based on surface element distribution measurement by ESCA and the water contact angle of the coating layer surface within a suitable range, the amount of urethane groups in the molecule (number average molecular weight of the isocyanate component used in the synthesis and polymerization of the polyurethane resin / number average molecular weight of the polyurethane resin) is preferably 26 to 38, more preferably 26 to 36.

[0056] Known methods can be used to produce the polyurethane resin of the present invention, and examples include a method in which a prepolymer having an isocyanate terminal is synthesized from a polyol and an excess of polyisocyanate, and then this prepolymer is reacted with a chain extender or a crosslinking agent to increase the molecular weight.

[0057] Examples of polyisocyanates used in the synthesis and polymerization of the urethane resin in the present invention include aromatic aliphatic diisocyanates such as xylylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane, aliphatic diisocyanates such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, and polyisocyanates obtained by pre-adding one or more of these compounds with trimethylolpropane or the like. The use of the aromatic aliphatic diisocyanates, alicyclic diisocyanates, or aliphatic diisocyanates described above is preferred because it does not cause yellowing problems. Furthermore, it is also preferred because it does not result in an excessively hard coating film, can relieve stress due to thermal shrinkage of the polyester film substrate, and does not cause problems such as cohesive failure of the coating layer.

[0058] Examples of chain extenders used in the synthesis and polymerization of the urethane resin in the present invention include glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, and 1,6-hexanediol; polyhydric alcohols such as glycerin, trimethylolpropane, and pentaerythritol; diamines such as ethylenediamine, hexamethylenediamine, and piperazine; amino alcohols such as monoethanolamine and diethanolamine; thiodiglycols such as thiodiethylene glycol; and water.

[0059] The coating layer in the present invention is preferably formed using an aqueous coating liquid by the in-line coating method described below. Therefore, the urethane resin of the present invention is preferably water-soluble or water-dispersible. The term "water-soluble or water-dispersible" means that the resin is dispersible in water or an aqueous solution containing less than 50% by mass of a water-soluble organic solvent.

[0060] To impart water dispersibility to a urethane resin, a sulfonic acid (salt) group or a carboxylic acid (salt) group can be introduced (copolymerized) into the urethane molecular skeleton. The polyurethane resin having a nonionic group such as a polyoxyalkylene group introduced therein is particularly preferred because it can minimize the interaction between the polyurethane resin and the cationic antistatic agent.

[0061] The method for introducing the nonionic group can be appropriately selected from known methods, and examples include a production method in which a portion of a polymer polyol is replaced with a diol containing a polyoxyethylene group, or a method in which a portion of the isocyanate groups in a nurate form of a diisocyanate is reacted in advance with methoxypolyethylene glycol, and then the resulting mixture is reacted with a polymer polyol.

[0062] To introduce carboxylic acid (salt) groups into the urethane resin of the present invention, for example, a polyol compound having a carboxylic acid group, such as dimethylolpropanoic acid or dimethylolbutanoic acid, is introduced as a copolymerization component and neutralized with a salt-forming agent. Specific examples of salt-forming agents include ammonia, trialkylamines such as trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine, and tri-n-butylamine, N-alkylmorpholines such as N-methylmorpholine and N-ethylmorpholine, and N-dialkylalkanolamines such as N-dimethylethanolamine and N-diethylethanolamine. These can be used alone or in combination of two or more.

[0063] When a polyol compound having a carboxylic acid (salt) group is used as a copolymerization component to impart water dispersibility, the molar ratio of the polyol compound having a carboxylic acid (salt) group in the urethane resin is preferably 3 to 25 mol%, more preferably 3 to 18 mol%, and particularly preferably 3 to 15 mol%, when the total polyisocyanate components in the urethane resin are taken as 100 mol%. By controlling the molar ratio within this range, water dispersibility is ensured while suppressing interaction with the coexisting cationic antistatic agent component, allowing the antistatic agent to be present on the surface of the coating layer.

[0064] The urethane resin of the present invention may be a self-crosslinking polyurethane resin having a blocked isocyanate bonded to the end to improve hardness.

[0065] The urethane resin of the present invention may have a branched structure.

[0066] To form a branched structure in the urethane resin, for example, a method can be preferably employed in which the polycarbonate polyol component, polyisocyanate, and chain extender are reacted at an appropriate temperature for an appropriate time, and then a compound having a tri- or higher functional hydroxyl group or isocyanate group is added, and the reaction is further allowed to proceed.

[0067] Specific examples of compounds having three or more functional hydroxyl groups include caprolactone triol, glycerol, trimethylolpropane, butanetriol, hexanetriol, 1,2,3-hexanetriol, 1,2,3-pentanetriol, 1,3,4-hexanetriol, 1,3,4-pentanetriol, 1,3,5-hexanetriol, 1,3,5-pentanetriol, polyethertriol, etc. Examples of the polyethertriol include compounds obtained by addition polymerization of one or more monomers such as ethylene oxide, propylene oxide, butylene oxide, amylene oxide, glycidyl ether, methyl glycidyl ether, t-butyl glycidyl ether, phenyl glycidyl ether, etc., using one or more compounds having three active hydrogens, such as alcohols such as glycerin and trimethylolpropane, and diethylenetriamine, as initiators.

[0068] Specific examples of compounds having tri- or higher functional isocyanate groups include polyisocyanate compounds having at least three isocyanate (NCO) groups per molecule. In the present invention, tri- or higher functional isocyanate compounds include biuret compounds, nurate compounds, and adduct compounds obtained by modifying isocyanate monomers having two isocyanate groups, such as aromatic diisocyanates, aliphatic diisocyanates, araliphatic diisocyanates, and alicyclic diisocyanates. Examples of aromatic diisocyanates include 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-toluidine diisocyanate, dianisidine diisocyanate, and 4,4'-diphenyl ether diisocyanate. Examples of aliphatic diisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate. Examples of aromatic aliphatic diisocyanates include xylylene diisocyanate, ω,ω'-diisocyanato-1,4-diethylbenzene, 1,4-tetramethylxylylene diisocyanate, and 1,3-tetramethylxylylene diisocyanate. Examples of alicyclic diisocyanates include 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (also known as IPDI, isophorone diisocyanate), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and 1,4-bis(isocyanatomethyl)cyclohexane.The biuret form is a self-condensation product having a biuret bond formed by the self-condensation of an isocyanate monomer, such as the biuret form of hexamethylene diisocyanate. The nurate form is a trimer of an isocyanate monomer, such as the trimer of hexamethylene diisocyanate, the trimer of isophorone diisocyanate, or the trimer of tolylene diisocyanate. The adduct form refers to a trifunctional or higher isocyanate compound obtained by reacting the above-mentioned isocyanate monomer with a trifunctional or higher low-molecular-weight active hydrogen-containing compound, such as a compound obtained by reacting trimethylolpropane with hexamethylene diisocyanate, a compound obtained by reacting trimethylolpropane with tolylene diisocyanate, a compound obtained by reacting trimethylolpropane with xylylene diisocyanate, or a compound obtained by reacting trimethylolpropane with isophorone diisocyanate.

[0069] Examples of chain extenders having three or more functional groups include alcohols having three or more hydroxyl groups, such as trimethylolpropane and pentaerythritol, which are mentioned in the above description of chain extenders.

[0070] (ratio) In the present invention, it is preferable that the antistatic agent is present on the surface of the coating layer, the characteristic values ​​based on the surface element distribution measurement by ESCA satisfy a suitable relationship, and the contact angle of the coating layer surface with water satisfies a suitable range. Therefore, after mainly controlling the polarity of the polyurethane resin, the solid content ratio of each component to the total solid content of the cationic antistatic agent, polyester resin, and polyurethane resin is further adjusted. Adjustment It is also preferable to control the polarity of the coating layer.

[0071] When the total solid content of the cationic antistatic agent, polyester resin, and polyurethane resin in the coating liquid is taken as 100% by mass, the content (% by mass) of the cationic antistatic agent is preferably 3.5 to 7.0, and more preferably 4.0 to 5.5. By adjusting the content within this range, the ratio of nitrogen element originating from the nitrogen-containing cationic antistatic agent based on surface element distribution measurement by ESCA, and the ratio of nitrogen element originating from the polyurethane resin / nitrogen element originating from the cationic antistatic agent can be controlled within suitable ranges.

[0072] When the total solid content of the cationic antistatic agent, polyester resin, and polyurethane resin in the coating solution is taken as 100% by mass, the content (% by mass) of the polyester resin is preferably 25 to 80, more preferably 30 to 80, and particularly preferably 35 to 80. By keeping the content within this range, adhesion between the coating layer and the polyester film substrate is ensured, and the amounts of polar groups in the polyester resin, such as carboxyl groups, sulfonate metal salt groups, and phosphate groups, which may interact with the coexisting cationic antistatic agent components, are controlled, and the ratio of nitrogen elements derived from the nitrogen-containing cationic antistatic agent based on surface element distribution measurement by ESCA can be controlled within a suitable range.

[0073] When the total solid content of the cationic antistatic agent, polyester resin, and polyurethane resin in the coating solution is taken as 100% by mass, the polyurethane resin content (mass%) is preferably 15 to 65, more preferably 20 to 55. A low polyurethane resin content results in a relatively high polyester resin ratio, resulting in an increase in the amount of polar groups in the polyester resin in the coating layer, such as carboxyl groups, sulfonate metal salt groups, and phosphate groups. A high polyurethane resin content results in a low polarity coating layer. While the polyurethane component on the surface of the coating layer increases, the low polarity of the coating layer makes it easier for the cationic antistatic agent to be present on the surface of the coating layer. In other words, the cationic antistatic agent component on the surface of the coating layer also increases. In light of these factors, by setting the polyurethane resin content (mass%) within the above range, the nitrogen element ratio derived from the nitrogen-containing cationic antistatic agent and the ratio of the nitrogen element ratio derived from the polyurethane resin to the nitrogen element ratio derived from the cationic antistatic agent, based on surface element distribution measurement by ESCA, can be controlled within suitable ranges.

[0074] (additives) The coating layer of the present invention may contain known additives, such as surfactants, antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic particles, and nucleating agents, within the range that does not impair the effects of the present invention.

[0075] In order to reduce the glossiness of the coating layer surface, inert particles may be contained in the coating layer.

[0076] Examples of the inert particles include inorganic particles such as titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, and calcium fluoride, and organic polymer particles such as polystyrene-based, polyacrylic-based, melamine-based, benzoguanamine-based, and silicone resin-based particles. These may be used alone or in combination of two or more.

[0077] The average particle size of the inert particles is preferably 0.1 to 2.4 μm, more preferably 0.3 to 2.0 μm. If the average particle size of the inert particles is 0.1 μm or less, the glossiness of the film surface may increase. Conversely, if the average particle size exceeds 2.4 μm, the particles tend to fall off from the coating layer, causing powdering.

[0078] The content of the inert particles can be set within a range that does not impair the effects of the present invention. However, to prevent the particles from dropping off from the coating layer and causing powder fall, the content of the particles is preferably 0 to 70.0 mass %, more preferably 0 to 60.0 mass %, and even more preferably 0 to 55.0 mass %, of the total solid content of the coating layer.

[0079] The particle shape is not particularly limited as long as it satisfies the objectives of the present invention, and spherical particles and irregular, non-spherical particles can be used. The particle size of irregular particles can be calculated as the circle equivalent diameter.

[0080] In order to increase the glossiness of the coating layer surface, it is better not to include particles in the coating layer.

[0081] (White PET manufacturing method) The white coated polyester film of the present invention can be produced by any method without any particular limitation, but can be produced, for example, as follows.

[0082] After the film raw material is thoroughly dried in a vacuum, it is melted in an extruder and extruded into a sheet from a T-die onto a rotating cooled metal roll while applying static electricity, to obtain an unstretched film.

[0083] In this case, rather than adding the white pigment and other additives in powder form to the extruder and kneading them, it is preferable to prepare a masterbatch polymer in which the white pigment and other additives are separately incorporated into the polyester resin at high concentrations, and then blend and dilute this with the polyester resin. A twin-screw extruder is preferably used as the extruder to ensure more uniform mixing of the various film raw materials. Furthermore, to improve electrostatic adhesion, it is preferable to add an alkaline earth metal salt and / or an alkali metal salt and phosphoric acid or a salt thereof when polymerizing the polyester. The addition of phosphoric acid or a salt thereof also has the effect of improving color tone (especially the b value).

[0084] In the present invention, the polyester film substrate may have either a single-layer structure or a laminated structure. A laminated structure has the advantage that the compositions of the surface layer and the central layer can be designed in a variety of ways depending on the required function. When the polyester film substrate has a laminated structure, it is most preferable to use a co-extrusion method in which the resins of the X layer and the Y layer are fed into separate extruders, and then laminated in a molten state to, for example, a two-layer structure of X layer / Y layer or a three-layer structure of X layer / Y layer / X layer, and extruded from the same die.

[0085] The unstretched film thus obtained is further subjected to biaxial orientation processing, such as stretching between rolls with different speeds (roll stretching), stretching by holding the film with clips and spreading it out (tenter stretching), or stretching by spreading it out using air pressure (inflation stretching).

[0086] The conditions for stretching and orienting unstretched film are closely related to the physical properties of the film. Below, we will explain the stretching and orientation conditions using the most common sequential biaxial stretching method, specifically the method of stretching an unstretched sheet in the longitudinal direction and then the width direction.

[0087] First, in the first longitudinal stretching step, the film is stretched between two or more rolls with different peripheral speeds. The heating method used here may be a method using a heated roll, a non-contact heating method, or a combination of these. The uniaxially stretched film is then introduced into a tenter and stretched 2.5 to 5 times in the width direction at a temperature equal to or lower than the melting point (Tm) of the polyester (Tm-10°C).

[0088] The biaxially stretched film thus obtained is subjected to heat treatment as required. The heat treatment is preferably carried out in a tenter at a temperature ranging from the melting point (Tm) of the polyester - 50 (°C) to Tm (°C).

[0089] (Void-containing PET manufacturing method) In the white, highly adhesive polyester film of the present invention, a thermoplastic resin incompatible with the polyester resin may be dispersed in the polyester resin during the process of melting and extruding the film raw material. In the examples of the present invention, the polyester resin and the thermoplastic resin incompatible with the polyester resin were supplied in pellet form, but the present invention is not limited thereto.

[0090] The raw materials fed into the extruder for melt molding into a film are prepared by pelletizing these resins according to the desired composition. However, when polyester resin and polyolefin resin are used as the raw materials for the void-containing polyester film of the substrate of the present invention, the specific gravities of the resins are significantly different, so it is preferable to take measures to prevent segregation of the pellets once mixed during the process of feeding them to the extruder. A suitable method for preventing segregation is to combine some or all of the raw material resins in advance, knead them, and pelletize them to form masterbatch pellets. This method was used in the examples of the present invention, but is not particularly limited as long as it does not interfere with the effects of the present invention.

[0091] Furthermore, when these incompatible resins are mixed and finely dispersed in a molten state, they tend to re-aggregate due to the effect of reducing the interfacial energy of the resins, which causes the void-producing agent to become coarsely dispersed during extrusion molding of the unstretched film, hindering the desired physical properties.

[0092] To prevent this, when molding the film of the present invention, it is preferable to finely disperse the void-producing agent in advance using a twin-screw extruder with a higher mixing effect. If this is difficult, it is also preferable to supply the raw resin from the extruder to the feed block or die via a static mixer as an auxiliary means. Examples of static mixers that can be used here include static mixers and orifices. However, when using these methods, it is preferable to avoid retention of thermally deteriorated resin in the melt line.

[0093] In addition, since the incompatible resin once dispersed in the polyester resin as fine particles tends to re-aggregate over time under low-shear molten conditions, a fundamental solution is to reduce the residence time in the melt line from the extruder to the die. In the present invention, the residence time in the melt line is preferably 30 minutes or less, and more preferably 15 minutes or less.

[0094] The conditions for stretching and orienting the unstretched film obtained as described above are closely related to the physical properties of the film. Below, the stretching and orientation conditions will be explained using the most common sequential biaxial stretching method, particularly the method of stretching an unstretched film in the longitudinal direction and then in the width direction, as an example.

[0095] In the longitudinal stretching step, the film is stretched 2.5 to 5.0 times in the machine direction using rolls heated to 80 to 120°C to obtain a uniaxially stretched film. The heating method may be a method using heated rolls or a non-contact heating method, or a combination of these. The uniaxially stretched film is then introduced into a tenter and stretched 2.5 to 5 times in the width direction at a temperature of (Tm-10°C) or less, where Tm is the melting point of the polyester.

[0096] The biaxially stretched film is also subjected to heat treatment as required, preferably in a tenter at a temperature in the range of (Tm-60°C) to Tm.

[0097] (Preparation for using recycled polyester raw materials) The polyester resin in the present invention may include polyester resin recycled from PET bottles. The crystallinity of the polyesters used in PET bottles is controlled to improve bottle moldability and appearance. As a result, polyesters containing 0.5 mol % to 10.0 mol % of isophthalic acid components and ester units derived from any diol component, such as ethylene glycol or diethylene glycol, relative to the total ester structural units in the polyester resin may be used. Furthermore, polyesters with increased intrinsic viscosity may be used by further solid-phase polymerization after liquid-phase polymerization. Polyester resin pellets recycled from PET bottles are usually obtained by cleaning, crushing, heat-melting, and re-pelletizing the PET bottles, but they may also be further solid-phase polymerized to increase their intrinsic viscosity. The intrinsic viscosity of polyester resins recycled from PET bottles is preferably in the range of 0.60 to 0.75 dL / g. An intrinsic viscosity of 0.60 dL / g or higher is preferable because the resulting film is less likely to break and film production is more stable. On the other hand, if the intrinsic viscosity is 0.75 dl / g or less, the increase in filtration pressure of the molten fluid will not be too great, and stable film production will be facilitated, which is preferable. Generally, when polyethylene terephthalate resin is solid-phase polymerized, the amount of oligomers contained in the resin, especially PET cyclic trimer, which has the highest content, will be less than that of resin polymerized in liquid phase. Rari The upper limit of the cyclic trimer oligomer contained in the cycled polyester resin is preferably 0.7% by mass, more preferably 0.5% by mass, and even more preferably 0.4% by mass.

[0098] The lower limit of the content of polyester resin recycled from PET bottles in the void-containing polyester film is preferably 25% by mass, more preferably 30% by mass, and even more preferably 50% by mass. A content of 25% by mass or more is preferable because it reduces the oligomers contained in the void-containing polyester film and can suppress oligomer precipitation. Furthermore, in terms of utilizing recycled resins, a high content is preferable in terms of contributing to reducing environmental impact. The upper limit of the content of polyester resin recycled from PET bottles is preferably 90% by mass, and more preferably 85% by mass.

[0099] The coating layer can be provided after or during the film production process. From the viewpoint of productivity, it is particularly preferred to form the coating layer by applying a coating liquid to at least one surface of an unstretched or uniaxially stretched PET film at any stage of the film production process.

[0100] Any known method can be used to apply this coating solution to the PET film. Examples include reverse roll coating, gravure coating, kiss coating, die coating, roll brushing, spray coating, air knife coating, wire bar coating, pipe doctor coating, impregnation coating, and curtain coating. These methods can be used alone or in combination.

[0101] The drying conditions after coating are preferably 80°C to 150°C, more preferably 90°C to 140°C, so that the cationic antistatic agent components bleed out onto the surface of the coating layer and the characteristic values ​​based on the surface element distribution measurement by ESCA satisfy the preferred relationships. A particularly preferred range is 100°C to 130°C. However, the conditions are not limited to those mentioned above, because extending the drying time may allow the cationic antistatic agent components to bleed out onto the surface of the coating layer even at a relatively low temperature, and the characteristic values ​​based on the surface element distribution measurement by ESCA may satisfy the preferred relationships.

[0102] In the present invention, the thickness of the coating layer is preferably in the range of 50 to 900 nm, more preferably in the range of 70 to 800 nm, even more preferably in the range of 100 to 600 nm, and particularly preferably in the range of 200 to 500 nm. As the thickness of the coating layer increases, the amount of cationic antistatic agent components present per volume of the coating layer increases. In other words, these components bleed out to the surface of the coating layer, resulting in a large amount of cationic antistatic agent components present on the surface of the coating layer. On the other hand, as the thickness of the coating layer decreases, the amount of cationic antistatic agent components present per volume of the coating layer decreases. In other words, the amount of cationic antistatic agent components present on the surface of the coating layer also decreases. Therefore, by controlling the thickness of the coating layer within the above range, the nitrogen element ratio derived from the cationic antistatic agent and the nitrogen element ratio derived from the polyurethane resin / nitrogen element ratio derived from the cationic antistatic agent can be controlled within suitable ranges for surface element distribution measurement by ESCA. [Example]

[0103] Next, the present invention will be described in detail using examples and comparative examples, but the present invention is not limited to the following examples. First, the evaluation methods used in the present invention will be described below.

[0104] (1) Nitrogen elements in the surface region (N and N + ) Ratio Measurement The surface composition was measured by ESCA. + (manufactured by Thermo Fisher Scientific) was used. Details of the measurement conditions are shown below. During the analysis, background was removed by the Shirley method. The surface composition ratio was calculated as the average value of the measurement results at three or more locations, and N (N + The N1s spectra were calculated by peak separation, where N(N + N1s (isoionized nitrogen element) is the peak around 402 eV in the N1s spectrum, and N (non-ionized nitrogen element such as CN) is the peak around 400 eV. Measurement conditions Excitation X-ray: Monochromated Al Kα line X-ray output: 12 kV, 6 mA Photoelectron escape angle: 90° Spot size: 400 μmφ Pass energy: 50eV Step: 0.1eV FIG. 1 is a graph showing the results of analyzing the N1s spectrum of the surface region of the white, highly adhesive polyester film of Example 1. The thin solid line represents the measured data of the N1s spectrum. The peaks of the measured spectrum were separated into multiple peaks, and the bond species corresponding to each peak were identified from the peak position and shape. Furthermore, curve fitting was performed on the peaks derived from each bond species, and the peak area was calculated. N(N + The peak area of ​​N (ionized nitrogen element such as CN) was defined as A (at%), and the peak area of ​​N (non-ionized nitrogen element such as CN) was defined as B (at%).

[0105] (2) Water contact angle measurement After leaving the sample in an atmosphere of 23°C and 65% RH for 24 hours, the contact angle between the coating surface of the sample and water was measured in that atmosphere using a contact angle meter (Kyowa Interface Science Co., Ltd., CA-X) and distilled water stored under the same conditions. Measurements were made at 10 points, and the average value was calculated. The contact angle data was used.

[0106] (3) Surface resistivity of the coating layer After leaving the white, highly adhesive polyester film or white laminated polyester film in an atmosphere of 23°C and 65% RH for 24 hours, the surface resistivity (Ω / □) of the film surface (or the coating layer surface, if a coating layer was present) was measured in that atmosphere using a surface resistance measuring device (Hiresta-IP, manufactured by Mitsubishi Petrochemical Co., Ltd.) at an applied voltage of 500 V. Especially good when less than 1×1012Ω / □: ◎ 1×1012Ω / □ or more to less than 1×1013Ω / □: Good: ○, If it is 1×1013Ω / □ or more, it is marked as ×.

[0107] (4) Adhesion to screen ink The coating layer of a white, easily adhesive polyester film or a white laminated polyester film was printed with a UV-curable screen ink (manufactured by TOYOINK Corporation, product name "TU240 FDSS 911 Black") using a Tetron screen (#250 mesh). The ink-coated film was then irradiated with 500 mJ / cm using a high-pressure mercury lamp. 2 The printed matter was then irradiated with ultraviolet light of 1000 W at ... 5: The remaining area of ​​the printed layer is 99% or more of the total. 4: The remaining area of ​​the printed layer is 90% or more but less than 99% of the total. 3: The remaining area of ​​the printed layer is 80% or more but less than 90% of the total. 2: The remaining area of ​​the printed layer is 70% or more but less than 80% of the total. 1: The remaining area of ​​the printed layer is 60% or more but less than 70% of the total area

[0108] (5) Adhesion to thermal transfer ink ribbon Using a thermal transfer ribbon (Ricoh Co., Ltd., B-110C resin type, black) attached to a Bon Electric Co., Ltd. BLP-323, a barcode pattern of arbitrary design was printed onto the coating layer of a white, easily adhesive polyester film or a white laminated polyester film to obtain a print. Next, a 24 mm wide, 50 mm long piece of Nichiban cellophane adhesive tape (CT405AP-24) was cut and completely adhered to the ink layer surface with a handy rubber roller, taking care not to trap air. The cellophane adhesive tape was then peeled off vertically, and the remaining area of ​​the printed layer in a 24 mm x 50 mm area was observed and evaluated according to the following criteria. In this invention, a score of 4 or higher was considered acceptable. 5: The remaining area of ​​the printed layer is 99% or more of the total. 4: The remaining area of ​​the printed layer is 90% or more but less than 99% of the total. 3: The remaining area of ​​the printed layer is 80% or more but less than 90% of the total. 2: The remaining area of ​​the printed layer is 70% or more but less than 80% of the total. 1: The remaining area of ​​the printed layer is 60% or more but less than 70% of the total area

[0109] (6) Adhesion to LBP toner Using a FUJI XEROX Corporation ApeosPort-V C3376, a randomly created design was printed onto the coating layer of a white, easily adhesive polyester film or a white laminated polyester film to obtain a printed product. Next, a 24 mm wide, 50 mm long piece of cellophane adhesive tape (CT405AP-24) manufactured by Nichiban was cut and completely adhered to the ink layer surface with a handy rubber roller, taking care not to trap air. The cellophane adhesive tape was then peeled off vertically, and the remaining area of ​​the printed layer was observed within a 24 mm x 50 mm area and evaluated according to the following criteria. In this invention, a score of 4 or higher was considered acceptable. 5: The remaining area of ​​the printed layer is 99% or more of the total. 4: The remaining area of ​​the printed layer is 90% or more but less than 99% of the total. 3: The remaining area of ​​the printed layer is 80% or more but less than 90% of the total. 2: The remaining area of ​​the printed layer is 70% or more but less than 80% of the total. 1: The remaining area of ​​the printed layer is 60% or more but less than 70% of the total area

[0110] (7) Adhesion to UV offset ink A UV-curable offset ink (manufactured by T&K TOKA Corporation, product name "BEST CURE UV161 Indigo S") was printed on the coating layer of a white adhesive polyester film or a white laminated polyester film using a printing machine (manufactured by Akira Manufacturing Co., Ltd., product name "RI Tester"). Then, 30 seconds after printing, a high-pressure mercury lamp was used to irradiate the ink-coated film with an integrated light dose of 70 mJ / cm. 2The UV-curable offset ink was cured by irradiating it with ultraviolet light, yielding a printed product. Next, a 24 mm wide, 50 mm long piece of cellophane adhesive tape (CT405AP-24) manufactured by Nichiban was cut out and completely adhered to the ink layer surface with a handy rubber roller, taking care not to trap air. The cellophane adhesive tape was then peeled off vertically, and the remaining area of ​​the printed layer was observed within a 24 mm x 50 mm area and evaluated according to the following criteria. In the present invention, a score of 4 or higher was considered acceptable. 5: The remaining area of ​​the printed layer is 99% or more of the total. 4: The remaining area of ​​the printed layer is 90% or more but less than 99% of the total. 3: The remaining area of ​​the printed layer is 80% or more but less than 90% of the total. 2: The remaining area of ​​the printed layer is 70% or more but less than 80% of the total. 1: The remaining area of ​​the printed layer is 60% or more but less than 70% of the total area

[0111] (8) Adhesion to UV offset ink during high-speed printing A UV-curable ink (manufactured by T&K TOKA Corporation, product name "BEST CURE UV161 Indigo S") was printed on the coating layer of a white, easily adhesive polyester film or a white laminated polyester film using a central impression printer. 3 / m 2 The ink was measured using an anilox roll, then transferred to a solid plate and then to a film. The transferred ink on the film was cured using a 160 W / cm metal halide UV lamp. The time from ink transfer to the film to UV light irradiation was 0.94 seconds. Next, a 24 mm wide, 50 mm long piece of Nichiban cellophane adhesive tape (CT405AP-24) was cut and completely adhered to the ink layer surface with a handy rubber roller, taking care not to trap air. The cellophane adhesive tape was then peeled off vertically, and the remaining area of ​​the printed layer in a 24 mm x 50 mm area was observed and evaluated according to the following criteria. In this invention, a score of 4 or higher was considered acceptable. 5: The remaining area of ​​the printed layer is 99% or more of the total. 4: The remaining area of ​​the printed layer is 90% or more but less than 99% of the total. 3: The remaining area of ​​the printed layer is 80% or more but less than 90% of the total. 2: The remaining area of ​​the printed layer is 70% or more but less than 80% of the total. 1: The remaining area of ​​the printed layer is 60% or more but less than 70% of the total area

[0112] (9) Apparent density Four 5.00 cm square pieces of film were cut out to serve as samples. These four sheets were stacked, and their thickness was measured at 10 points using a micrometer to four significant figures to determine the average thickness of the stack. This average value was divided by 4 and rounded to the fourth decimal place to determine the average film thickness (t: μm) per sheet to the third decimal place. In addition, the mass (w: g) of the four samples was measured to four significant figures using an automatic top-pan balance, and the apparent density was calculated using the following formula. The apparent density was rounded to three significant figures. Apparent density (g / cm 3 )=w×10 4 / (5.00×5.00×t×4)

[0113] (10) Resin solid content thickness of coating layer The thickness of the resin solid content was calculated from the amount of coating material applied and the mass of the total resin solid content contained in the coating material.

[0114] (11) b value The reflective color b value was measured using a color difference meter (ZE6000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS-8722.

[0115] (Synthesis of Nitrogen-Containing Cationic Antistatic Agent A-1) Using 89 g of dimethylaminoethanol and 285 g of stearic acid having 18 carbon atoms, an esterification reaction was carried out at 100°C under a nitrogen atmosphere for 10 hours, tetrahydrofuran was added as a quaternization solvent, and a specified amount of dimethyl sulfate was added to the target amine, followed by a reaction at 70°C for approximately 10 hours. After the reaction, the solvent was distilled off under reduced pressure, and isopropanol was added to adjust the solid concentration to the desired level, yielding an isopropanol solution A-1 of a cationic antistatic agent having a quaternary ammonium salt.

[0116] (Synthesis of nitrogen-containing cationic antistatic agents A-2) Using 89 g of dimethylaminoethanol and 228 g of myristic acid having 14 carbon atoms, the same treatment as for A-1 was carried out to obtain a cationic antistatic agent solution A-2 having a quaternary ammonium salt.

[0117] (Synthesis of nitrogen-containing cationic antistatic agents A-3) Using 89 g of dimethylaminoethanol and 354 g of tricosylic acid with 23 carbon atoms, an esterification reaction was carried out at 200°C under a nitrogen atmosphere for 10 hours, tetrahydrofuran was added as a quaternization solvent, and a specified amount of dimethyl sulfate was added to the target amine, followed by a reaction at 70°C for approximately 10 hours. The same treatment as in A-1 was repeated to obtain an isopropanol solution A-3 of a cationic antistatic agent having a quaternary ammonium salt.

[0118] (Synthesis of nitrogen-containing cationic antistatic agents A-4) Using 116 g of N,N-dimethyl-1,3-propanediamine and 285 g of stearic acid, the same treatment as in A-1 was carried out to obtain an isopropanol solution A-4 of a cationic antistatic agent having a quaternary ammonium salt.

[0119] (Polystyrene sulfonate ammonium salt A-5 with a number average molecular weight of 10,000) Isopropanol was added to existing ammonium polystyrene sulfonate having a number average molecular weight of 10,000 to obtain an isopropanol solution A-5 of ammonium polystyrene sulfonate.

[0120] (Polymerization of Polyester Resin B-1) A stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser was charged with 194.2 parts by mass of dimethyl terephthalate, 184.5 parts by mass of dimethyl isophthalate, 14.8 parts by mass of dimethyl-5-sodium sulfoisophthalate, 233.5 parts by mass of diethylene glycol, 136.6 parts by mass of ethylene glycol, and 0.2 parts by mass of tetra-n-butyl titanate, and the transesterification reaction was carried out at a temperature of 160 to 220°C for 4 hours. The temperature was then raised to 255°C, and the reaction system was gradually reduced in pressure. The reaction was then continued for 1 hour and 30 minutes under a reduced pressure of 30 Pa to obtain copolymer polyester resin (B-1). The resulting copolymer polyester resin (B-1) was pale yellow and transparent. The reduced viscosity of copolymer polyester resin (B-1) was measured and found to be 0.70 dL / g. The glass transition temperature measured by DSC was 40°C.

[0121] (Preparation of Polyester Water Dispersion Bw-1) A reactor equipped with a stirrer, thermometer, and reflux device was charged with 25 parts by mass of polyester resin (B-1) and 10 parts by mass of ethylene glycol n-butyl ether, and the mixture was heated to 110°C and stirred to dissolve the resin. After the resin was completely dissolved, 65 parts by mass of water was gradually added to the polyester solution while stirring. After the addition, the liquid was cooled to room temperature while stirring to produce a milky white polyester water dispersion (Bw-1) with a solids content of 30.0% by mass.

[0122] (Preparation of polyester resin solution Bw-2) A reactor was charged with 97 parts by weight of dimethyl terephthalate, 93 parts by weight of dimethyl isophthalate, 68 parts by weight of ethylene glycol, 116 parts by weight of diethylene glycol, 0.1 parts by weight of zinc acetate, and 0.1 parts by weight of antimony trioxide, and a transesterification reaction was carried out at 180°C for 3 hours. Next, 7.1 parts by weight of 5-sodium sulfoisophthalic acid was added, and an esterification reaction was carried out at 240°C for 1 hour. This was followed by a polycondensation reaction at 250°C under reduced pressure (1.33 to 0.027 kPa) for 2 hours, yielding a polyester resin with a molecular weight of 22,000. 300 parts by weight of this polyester resin and 140 parts by weight of butyl cellosolve were stirred at 160°C for 3 hours to obtain a viscous molten liquid. Water was gradually added to this molten liquid, and after 1 hour, a homogeneous, pale white polyester resin solution with a solids content of 25.0% by weight was prepared.

[0123] (Preparation of urethane resin solution C-1 having a polycarbonate structure) 22 parts by mass of 4,4-dicyclohexylmethane diisocyanate, 20 parts by mass of polyethylene glycol monomethyl ether having a number-average molecular weight of 700, 53 parts by mass of polyhexamethylene carbonate diol having a number-average molecular weight of 2100, 5 parts by mass of neopentyl glycol, and 84.00 parts by mass of acetone as a solvent were added to a four-neck flask equipped with a stirrer, Dimroth condenser, nitrogen inlet tube, silica gel drying tube, and thermometer. The mixture was stirred at 75°C for 3 hours under a nitrogen atmosphere, and it was confirmed that the reaction solution had reached the specified amine equivalent. The reaction solution temperature was then lowered to 50°C, and 3 parts by mass of methyl ethyl ketoxime was added dropwise. After cooling the reaction solution to 40°C, a polyurethane prepolymer solution was obtained. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring, and the temperature was adjusted to 25°C. Adjustment Then, 2000min -1 The polyurethane prepolymer solution was added and dispersed in water while stirring and mixing at 50°C. Then, the acetone and a portion of the water were removed under reduced pressure to prepare a water-dispersible urethane resin solution (C-1) with a solids content of 35.4% by mass.

[0124] (Preparation of urethane resin solution C-2 having a polycarbonate structure) A four-neck flask equipped with a stirrer, Dimroth condenser, nitrogen inlet tube, silica gel drying tube, and thermometer was charged with 22 parts by weight of 4,4-dicyclohexylmethane diisocyanate, 20 parts by weight of polyethylene glycol monomethyl ether with a number average molecular weight of 700, 53 parts by weight of polyhexamethylene carbonate diol with a number average molecular weight of 2100, 5 parts by weight of neopentyl glycol, and 84.00 parts by weight of acetone as a solvent. The mixture was stirred under a nitrogen atmosphere at 75°C for 3 hours, and the reaction mixture was confirmed to have reached the required amine equivalent. Next, 16 parts by weight of a polyisocyanate compound having an isocyanurate structure (Asahi Kasei Chemicals, Duranate TPA, trifunctional) made from hexamethylene diisocyanate was added, and the mixture was stirred under a nitrogen atmosphere at 75°C for 1 hour, and the reaction mixture was confirmed to have reached the required amine equivalent. The reaction mixture temperature was then lowered to 50°C, and 7 parts by weight of methyl ethyl ketoxime was added dropwise. After the reaction solution was cooled to 40°C, a polyurethane prepolymer solution was obtained. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high speed stirring, and the temperature was adjusted to 25°C. Adjustment Then, 2000min -1 The polyurethane prepolymer solution was added and dispersed in water while stirring and mixing at 50°C. Then, the acetone and part of the water were removed under reduced pressure to prepare a water-dispersible urethane resin solution (C-2) with a solids content of 35.4% by mass.

[0125] (Preparation of urethane resin solution C-3 having a polycarbonate structure) A four-neck flask equipped with a stirrer, a Dimroth condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer was charged with 31.0 parts by mass of hydrogenated m-xylylene diisocyanate, 7.0 parts by mass of dimethylolpropanoic acid, 60 parts by mass of polyhexamethylene carbonate diol having a number average molecular weight of 1800, 6 parts by mass of neopentyl glycol, and 84.00 parts by mass of acetone as a solvent, and stirred at 75°C for 3 hours under a nitrogen atmosphere. It was confirmed that the reaction solution had reached the predetermined amine equivalent. After cooling the reaction solution to 40°C, 6.65 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. , high450 g of water was added to a reaction vessel equipped with a homodisperser capable of rapid stirring, and the temperature was adjusted to 25°C. The mixture was stirred for 2000 min. -1 The polyurethane prepolymer solution was added and dispersed in water while stirring and mixing at 50°C. Then, the acetone and a portion of the water were removed under reduced pressure to prepare a water-dispersible urethane resin solution (C-3) with a solids content of 35.0% by mass.

[0126] (Preparation of urethane resin solution C-4 having a polycarbonate structure) A four-neck flask equipped with a stirrer, a Dimroth condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer was charged with 4 , 22.0 parts by mass of 4-dicyclohexylmethane diisocyanate, 4.5 parts by mass of dimethylol butanoic acid, 72.5 parts by mass of polyhexamethylene carbonate diol with a number average molecular weight of 2000, 1 part by mass of neopentyl glycol, and 84.00 parts by mass of acetone as a solvent were added and stirred under a nitrogen atmosphere at 75°C for 3 hours, and it was confirmed that the reaction solution had reached the specified amine equivalent. Next, the reaction solution was cooled to 40°C, and 8.77 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisperser capable of high-speed stirring, and the temperature was adjusted to 25°C. The mixture was stirred for 2000 min. -1 The polyurethane prepolymer solution was added and dispersed in water while stirring and mixing at 50°C. Then, the acetone and a portion of the water were removed under reduced pressure to prepare a water-dispersible urethane resin solution (C-4) with a solids content of 37.0 mass%.

[0127] (Preparation of Polyester Structure-Containing Urethane Resin Solution C-5) A four-neck flask equipped with a stirrer, Dimroth condenser, nitrogen inlet tube, silica gel drying tube, and thermometer was charged with 83.4 parts by mass of hydrogenated m-xylylene diisocyanate, 16.9 parts by mass of dimethylolpropanoic acid, 28.4 parts by mass of 1,6-hexanediol, 151.0 parts by mass of a polyester diol consisting of adipic acid and 1,4-butanediol with a number average molecular weight of 2000, and 110 parts by mass of acetone as a solvent. The mixture was stirred at 75°C under a nitrogen atmosphere for 3 hours, and it was confirmed that the reaction solution had reached the required amine equivalent. Next, the reaction solution was cooled to 40°C, and 13.3 parts by mass of triethylamine was added to obtain a polyurethane polymer solution. Next, 500 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring, and the temperature was adjusted to 25°C. The mixture was stirred for 2000 min. -1 While stirring and mixing at 50°C, the polyurethane polymer solution was added and dispersed in water. The acetone solvent was then removed under reduced pressure. The concentration was adjusted with water to prepare a polyurethane resin solution (C-5) with a solids content of 35.0% by mass.

[0128] (Preparation of Polyester Structure-Containing Urethane Resin Solution C-6) Into a four-neck flask equipped with a stirrer, a Dimroth condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 82.8 parts by mass of hydrogenated m-xylylene diisocyanate, 25.0 parts by mass of dimethylolpropanoic acid, and 2 parts by mass of 3-methyl-1,5-pentanediol were added. 、 150.0 parts by mass of polyester diol consisting of terephthalic acid / isophthalic acid / ethylene glycol / diethylene glycol = 50 / 50 / / 40 / 60 (molar ratio) and 110 parts by mass of acetone as a solvent were added and stirred under a nitrogen atmosphere at 75 °C for 3 hours, and it was confirmed that the reaction solution had reached the specified amine equivalent. Next, the reaction solution was cooled to 40 °C, and 19.8 parts by mass of triethylamine was added to obtain a polyurethane polymer solution. Next, 880 g of water was added to a reaction vessel equipped with a homodisperser capable of high-speed stirring, and the temperature was adjusted to 25 °C. The mixture was stirred for 2000 min. -1 While stirring and mixing at 100°C, the polyurethane polymer solution was added and dispersed in water. After that, the solvent, acetone, was removed under reduced pressure. By adjusting the concentration with water, the solid minutes A 30.0 mass % polyurethane resin solution (C-6) was prepared.

[0129] (Preparation of Polyether Structure-Containing Urethane Resin Solution C-7) Into a four-neck flask equipped with a stirrer, a Dimroth condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 45.0 parts by mass of hydrogenated m-xylylene diisocyanate, 20.0 parts by mass of 1,6-hexanediol, 149.0 parts by mass of polyethylene glycol having a number average molecular weight of 2000, and 110 parts by mass of acetone as a solvent were added, and the mixture was stirred at 75°C for 3 hours under a nitrogen atmosphere. It was confirmed that the reaction solution had reached the predetermined amine equivalent. Next, after the reaction solution was cooled to 40°C, 550 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring, the temperature was adjusted to 25°C, and the mixture was stirred for 2000 min. -1 While stirring and mixing at 50°C, the polyurethane polymer solution was added and dispersed in water. The solvent, acetone, was then removed under reduced pressure. The concentration was adjusted with water to prepare a polyurethane resin solution (C-7) with a solids content of 30.0% by mass.

[0130] (Preparation of Polyurethane Blocked Isocyanate Aqueous Dispersion (C-8) Having a Polyester Structure) 33.6 parts by weight of hexamethylene diisocyanate was added to 200 parts by weight of a polyester (molecular weight 2000) of ethylene oxide 2 mole adduct of bisphenol A and maleic acid, and the reaction was carried out at 100°C for 2 hours. The temperature of the system was then temporarily lowered to 50°C, and 73 parts by weight of a 30% aqueous solution of sodium bisulfite was added. After stirring at 45°C for 60 minutes, the mixture was diluted with 718 parts by weight of water to obtain a blocked polyisocyanate aqueous dispersion (C-8) with a solids content of 20.0% by weight. The blocked isocyanate crosslinker had 2 functional groups and an NCO equivalent of 1300.

[0131] Example 1 (1) Preparation of coating solution The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. ChargingThe solution was coated so that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was 4.0 / 57.6 / 38.4 and the resin solid thickness was 450 nm, to obtain a white, highly adhesive polyester film. Nitrogen-containing cationic antistatic agent solution (A-1) 2.06 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-1) 9.60 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0132] (2) Preparation of Master Pellet M1 A pellet mixture of 60% by mass of polymethylpentene resin (DX820, manufactured by Mitsui Chemicals, Inc.) with a melt viscosity (ηO) of 1,300 poise, 20% by mass of polystyrene resin (G797N, manufactured by Nippon Polystyrene Co., Ltd.) with a melt viscosity (ηS) of 3,900 poise, and 20% by mass of polypropylene resin (J104WC, manufactured by Grand Polymer Co., Ltd.) with a melt viscosity of 2,000 poise was fed into a vented twin-screw extruder controlled at 285°C and pre-mixed. This molten resin was continuously fed into a vented single-screw kneader, kneaded, and extruded, and the resulting strand was cooled and cut to prepare void-producing agent master pellets (M1).

[0133] (3) Preparation of Master Pellet M2-A In addition, 50% by mass of polyethylene terephthalate resin with an intrinsic viscosity of 0.62 dL / g and an antimony catalyst, produced by a known method, was mixed with 50% by mass of anatase-type titanium dioxide particles (TA-300, manufactured by Fuji Titanium Co., Ltd.) with an average particle size of 0.3 μm, and the mixture was fed into a vented twin-screw extruder and pre-mixed. This molten resin was continuously fed into a vented single-screw kneader, kneaded, and extruded. The resulting strand was cooled and cut to prepare titanium dioxide-containing master pellets (M2-A).

[0134] (4) Production of white, highly adhesive polyester film (film substrate α-1) (Preparation of Film Raw Material D1-A) 81% by mass of the polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g, which had been vacuum dried at 140°C for 8 hours, 9% by mass of the master pellets (M1), which had been vacuum dried at 90°C for 4 hours, and 10% by mass of the master pellets (M2-A), were mixed together to prepare a film raw material (D1-A).

[0135] (Preparation of stretched film) The film raw material (D1-A) was mixed with 70% by mass of the same polyethylene terephthalate resin used in preparing the film raw material (D1-A) and 30% by mass of the master pellets (M2-A) and then fed separately to an extruder for A layer, the temperature of which was adjusted to 290°C, into an extruder for Y layer, the temperature of which was adjusted to 285°C. The molten resin discharged from the extruder for Y layer was introduced into a feedbook through an orifice, and the resin discharged from the extruder for A layer was introduced into a feedbook through a static mixer, and a layer (Y layer) made of the film raw material (D1-A) and a layer (X layer) made of polyethylene terephthalate resin and master pellets (M2-A) were laminated in the order of X layer / Y layer / X layer.

[0136] The molten resin was co-extruded from a T-die onto a cooling roll adjusted to 25°C in the form of a sheet, and solidified by electrostatic application to produce an unstretched film with a thickness of 510 μm. The discharge rate of each extruder was adjusted so that the thickness ratio of each layer was 1:8:1. Adjustment At this time, the molten resin remained in the melt line for approximately 12 minutes, and the shear rate it received from the T-die was approximately 150 / s.

[0137] (Preparation of biaxially stretched film) The resulting unstretched film was uniformly heated to 65°C using a heating roll and longitudinally stretched 3.4 times between two pairs of nip rolls (low-speed roll: 2 m / min, high-speed roll: 6.8 m / min) with different peripheral speeds. An infrared heater (rated output: 20 W / cm) equipped with a gold reflective film was installed 1 cm from the film surface, facing both sides of the film, as an auxiliary film heating device. The coating solution described above was applied to one side of the resulting uniaxially stretched film using the reverse kiss coating method so that the resin solids thickness after stretching would be 50 nm. After coating, the film was introduced into a tenter, heated to 150°C while drying, and transversely stretched 3.7 times. The width was fixed and heat-treated at 220°C for 5 seconds, and then further relaxed 4% in the width direction at 200°C to obtain a 50 μm-thick white, highly adhesive polyester film (the film substrate portion is designated α-1). The b value of this film was 1.6.

[0138] Example 2 The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white, highly adhesive polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 57.0 / 38.0. Nitrogen-containing cationic antistatic agent solution (A-1) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-1) 9.60 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0139] Example 3 The following coating agent was mixed into a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. ChargingA white, highly adhesive polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.4 / 56.8 / 37.8. Nitrogen-containing cationic antistatic agent solution (A-1) 2.75 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-1) 9.60 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0140] Example 4 The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white, highly adhesive polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 76.0 / 19.0. Nitrogen-containing cationic antistatic agent solution (A-1) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 22.67 parts by mass Urethane resin solution (C-1) 4.80 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0141] Example 5 The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. ChargingA white, highly adhesive polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 38.0 / 57.0. Nitrogen-containing cationic antistatic agent solution (A-1) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 11.33 parts by mass Urethane resin solution (C-1) 14.41 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0142] Example 6 The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white, highly adhesive polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 57.0 / 38.0. Nitrogen-containing cationic antistatic agent solution (A-2) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-1) 9.60 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0143] Example 7 The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. ChargingA white, highly adhesive polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 57.0 / 38.0. Nitrogen-containing cationic antistatic agent solution (A-4) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-1) 9.60 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0144] Example 8 The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white, highly adhesive polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 57.0 / 38.0. Nitrogen-containing cationic antistatic agent solution (A-1) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester resin solution (Bw-2) 20.40 parts by mass Urethane resin solution (C-1) 9.60 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0145] Example 9 The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. ChargingA white, highly adhesive polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 57.0 / 38.0. Nitrogen-containing cationic antistatic agent solution (A-1) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-2) 9.60 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0146] Example 10 The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white, highly adhesive polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 57.0 / 38.0. Nitrogen-containing cationic antistatic agent solution (A-1) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-3) 9.71 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0147] Example 11 The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. ChargingA white, highly adhesive polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 57.0 / 38.0. Nitrogen-containing cationic antistatic agent solution (A-1) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-5) 9.71 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0148] Example 12 The following coating agent was mixed into a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white, highly adhesive polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 57.0 / 38.0 and the resin solid thickness was applied to 650 nm. Nitrogen-containing cationic antistatic agent solution (A-1) 3.30 parts by mass (Solid content concentration 19.20% by mass) Polyester water dispersion (Bw-1) 30.00 parts by mass Urethane resin solution (C-1) 16.95 parts by mass Particles 31.91 parts by mass (benzoguanamine formaldehyde condensate particles with an average particle size of 2 μm, Solid content concentration 40.00% by mass) Surfactant 0.40 parts by mass (Silicone-based, solid content 10% by mass)

[0149] Example 13 The following coating agent was mixed into a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white, highly adhesive polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 6.5 / 60.7 / 32.8 and the resin solid thickness was applied to 50 nm. Nitrogen-containing cationic antistatic agent solution (A-1) 2.45 parts by mass (Solid content concentration 15.8% by mass) Polyester water dispersion (Bw-1) 12.35 parts by mass Urethane resin solution (C-1) 6.27 parts by mass Surfactant 0.25 parts by mass (Silicone-based, solid content 10% by mass)

[0150] Example 14 A white, highly adhesive polyester film was obtained in the same manner as in Example 1, except that the method for preparing the master pellets and the preparation of the unstretched film in the preparation of the white, highly adhesive polyester film were changed as follows. The b value of this film was 1.6.

[0151] (1) Preparation of Master Pellet M2-B A mixture of 50% by mass of polyethylene terephthalate resin with an intrinsic viscosity of 0.62 dL / g, produced by a known method using a phosphorus compound and an aluminum catalyst, and 50% by mass of anatase-type titanium dioxide particles (manufactured by Fuji Titanium Co., Ltd., TA-300) with an average particle size of 0.3 μm was fed into a vented twin-screw extruder and pre-mixed. This molten resin was continuously fed into a vented single-screw kneader, kneaded, and extruded. The resulting strand was cooled and cut to prepare titanium dioxide-containing master pellets (M2-B).

[0152] (2) Manufacture of white, highly adhesive polyester film (film substrate α-2) (Preparation of film raw material D1-B) 81% by mass of the polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g, which had been vacuum dried at 140°C for 8 hours, 9% by mass of the master pellets (M1), which had been vacuum dried at 90°C for 4 hours, and 10% by mass of the master pellets (M2-B), were mixed together to prepare a film raw material (D1-B).

[0153] (Preparation of unstretched film) The film raw material (D1-B) was mixed with 70% by mass of the same polyethylene terephthalate resin used in the film raw material (D1-B) and 30% by mass of the master pellets (M2-B) and fed separately to an extruder for an A layer, the temperature of which was adjusted to 290° C. The molten resin discharged from the extruder for the Y layer was introduced into a feedbook via an orifice, and the resin discharged from the extruder for the A layer was introduced into a feedbook via a static mixer, and a layer (Y layer) made of the film raw material (D1-B) and a layer (X layer) made of the polyethylene terephthalate resin and master pellets (M2-B) were laminated in the order of X layer / Y layer / X layer (the film substrate portion of the in-line coated biaxially stretched film is referred to as α-2).

[0154] Example 15 A white, highly adhesive polyester film was obtained in the same manner as in Example 1, except that the method for preparing the master pellets and the production of the white, highly adhesive polyester film were changed as follows. The b value of this film was 1.5.

[0155] (1) Preparation of Master Pellet M3 49.9% by mass of polyethylene terephthalate resin, which was prepared by a known method and contained no white pigment or inorganic particles, and was produced using a phosphorus compound and an aluminum catalyst. The resin had an intrinsic viscosity of 0.62 dL / g, and was mixed with 50.0% by mass of anatase titanium dioxide particles (TA-300, manufactured by Fuji Titanium Co., Ltd.) with an average particle size of 0.3 μm and 0.1% by mass of a fluorescent whitening agent (OB1, manufactured by Eastman Chemical Co.). The mixture was fed into a vented twin-screw extruder and pre-mixed. The molten resin was then continuously fed into a vented single-screw extruder, mixed, and extruded. The resulting strands were cooled and cut to produce master pellets (M3).

[0156] (2) Preparation of Master Pellet M4 Also, polyethylene terephthalate resin pellets (M4) containing 0.7% by mass of silica particles with an average particle size of 1.8 μm added by a known polymerization addition method and an aluminum catalyst and having an intrinsic viscosity of 0.62 dl / g were prepared.

[0157] (3) Production of white, highly adhesive polyester film (β) (Preparation of Film Raw Materials D2 and D3) 75% by mass of polyethylene terephthalate resin containing no white pigment or inorganic particles, which was produced by a phosphorus compound and an aluminum catalyst and had an intrinsic viscosity of 0.62 dL / g, and 25% by mass of the titanium dioxide particle (white pigment)-containing master pellets (M3) were pellet-mixed and dried in a vacuum at 140°C for 8 hours to obtain film raw material (D2). 30% by mass of titanium dioxide-containing master pellets (M3) and 70% by mass of silica particle (inorganic particle)-containing pellets (M4) were pellet-mixed and dried in a vacuum at 140°C for 8 hours to obtain film raw material (D3).

[0158] (Preparation of unstretched film) The film raw materials were fed to separate extruders, and a layer (Y layer) made of raw material (D2) and a layer (X layer) made of raw material (D3) were laminated in a molten state using a feed block in the order of X layer / Y layer / X layer. The molten resin was co-extruded from a T-die onto a rotating cooled metal roll adjusted to 25°C. The output rate of each extruder was adjusted so that the thickness ratio of each layer was 1:8:1. Adjustment At this time, the molten resin remained in the melt line for approximately 12 minutes, and the shear rate it received from the T-die was approximately 150 / s.

[0159] (Preparation of biaxially stretched film) The resulting unstretched film was uniformly heated to 66°C using a heating roll and stretched 3.4 times between two pairs of nip rolls (low-speed roll: 2 m / min, high-speed roll: 6.8 m / min) with different peripheral speeds. At this time, infrared heaters (rated output: 20 W / cm) equipped with gold reflective films were installed 1 cm from the film surface as auxiliary film heating devices. The coating solution described above was applied to one side of the resulting uniaxially stretched film using the reverse kiss coating method so that the resin solid thickness before stretching was 450 nm. After coating, the film was introduced into a tenter, heated to 150°C while drying, and stretched 3.7 times laterally. The width was fixed and heat-treated at 220°C for 5 seconds, and then further relaxed 4% in the width direction at 200°C to obtain a 50 μm-thick white, highly adhesive polyester film (the substrate film portion is referred to as β).

[0160] (Comparative Example 1) The following coating agent was mixed into a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white laminated polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 2.5 / 58.5 / 39.0. Nitrogen-containing cationic antistatic agent solution (A-1) 1.26 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-1) 9.60 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0161] (Comparative Example 2) The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white laminated polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 7.1 / 55.7 / 37.2. Nitrogen-containing cationic antistatic agent solution (A-1) 3.72 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-1) 9.60 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0162] (Comparative Example 3) The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white laminated polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 85.5 / 9.5. Nitrogen-containing cationic antistatic agent solution (A-1) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 25.50 parts by mass Urethane resin solution (C-1) 2.40 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0163] Comparative Example 4 The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white laminated polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 28.5 / 67.0. Nitrogen-containing cationic antistatic agent solution (A-1) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 8.50 parts by mass Urethane resin solution (C-1) 16.81 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0164] (Comparative Example 5) The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white laminated polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 57.0 / 38.0. Nitrogen-containing cationic antistatic agent solution (A-3) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-1) 9.60 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0165] (Comparative Example 6) The following coating agent was mixed into a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white laminated polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 57.0 / 38.0. Nitrogen-containing cationic antistatic agent solution (A-5) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-1) 9.60 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0166] (Comparative Example 7) The following coating agent was mixed into a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white laminated polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 57.0 / 38.0. Nitrogen-containing cationic antistatic agent solution (A-1) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-4) 9.19 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0167] (Comparative Example 8) The following coating agent was mixed into a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white laminated polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 57.0 / 38.0. Nitrogen-containing cationic antistatic agent solution (A-1) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-6) 11.33 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0168] Comparative Example 9 The following coating agent was mixed into a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white laminated polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 57.0 / 38.0. Nitrogen-containing cationic antistatic agent solution (A-1) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-7) 11.33 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0169] (Comparative Example 10) The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white laminated polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.8 / 33.0 / 61.2. Nitrogen-containing cationic antistatic agent solution (A-1) 2.83 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 9.33 parts by mass Urethane resin solution (C-8) 26.00 parts by mass Particles (A) 16.31 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Particles (b) 5.44 parts by mass (Silica particles with an average particle size of 1.00 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0170] (Comparative Example 11) The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white laminated polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.8 / 33.0 / 61.2 and the resin solid thickness was applied to 650 nm. Nitrogen-containing cationic antistatic agent solution (A-1) 2.91 parts by mass (Solid content concentration 19.20% by mass) Polyester water dispersion (Bw-1) 11.67 parts by mass Urethane resin solution (C-8) 32.50 parts by mass Particles 21.27 parts by mass (Benzoguanamine particles with an average particle size of 2.00 μm, solid content concentration of 40.00 mass%) Surfactant 0.45 parts by mass (Silicone-based, solid content 10% by mass)

[0171] (Comparative Example 12) The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white laminated polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 57.0 / 38.0 and the resin solid thickness was applied to 950 nm. Nitrogen-containing cationic antistatic agent solution (A-1) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-1) 9.60 parts by mass Particles 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid content concentration of 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0172] (Comparative Example 13) The following coating agent was mixed with a mixed solvent of water and isopropanol to form a cationic coating containing nitrogen. Charging A white laminated polyester film was obtained in the same manner as in Example 1, except that the solid mass ratio of the inhibitor / polyester resin / urethane resin solution was changed to 5.0 / 57.0 / 38.0 and the resin solid thickness was applied to 25 nm. Nitrogen-containing cationic antistatic agent solution (A-1) 2.52 parts by mass (Solid content concentration 17.50% by mass) Polyester water dispersion (Bw-1) 17.00 parts by mass Urethane resin solution (C-1) 9.60 parts by mass Surfactant 0.15 parts by mass (Silicone-based, solid content 10% by mass)

[0173] Tables 1 and 2 summarize the evaluation results for each example and comparative example.

[0174] [Table 1]

[0175] [Table 2]

[0176] The white, highly adhesive polyester films obtained in each Example were found to have excellent antistatic properties and excellent adhesion to various inks and toners, particularly to UV-curable inks during high-speed printing. On the other hand, the comparative examples were unsatisfactory in at least one of antistatic properties and adhesion to inks and toners due to inappropriate A value, B / A value, or water contact angle of the coating layer. [Industrial Applicability]

[0177] According to the present invention, it is possible to provide a white, highly adhesive polyester film that can be suitably used in fields such as label applications. [Explanation of symbols]

[0178] Thin solid line: Measured data of N1s spectrum on the coating layer surface Dotted line: curve showing the ionized nitrogen peaks obtained by peak separation of the N1s spectrum Dashed line: curve showing the unionized nitrogen peak obtained by peak separation of the N1s spectrum (1): Ionized nitrogen element peak (2) : Non-ionized nitrogen peak

Claims

1. a coating layer is provided on at least one surface of a polyester film substrate, the coating layer having a thickness of 50 to 900 nm, the coating layer containing a cationic antistatic agent having a nitrogen element, a polyester resin, and a polyurethane resin, and a ratio A (at %) of the nitrogen element derived from the antistatic agent and a ratio B (at %) of the nitrogen element derived from the polyurethane resin, which are determined by surface element distribution measurement by X-ray photoelectron spectroscopy, satisfy the following formulas (i) and (ii): the contact angle of the coating layer surface with water is 50° to 70°; A white, highly adhesive polyester film suitable for printing with UV-curable ink, thermal transfer ink ribbon, and LBP toner. (i) A (at%) > 0.4 (ii) 2.0 ≦ B / A ≦ 5.0

2. 2. The white, highly adhesive polyester film according to claim 1, wherein the polyester film substrate contains inorganic particles and / or a thermoplastic resin incompatible with the polyester resin.

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