Water-based flexographic ink easily adhering polyester film

Abstract

To provide an easily adhesive polyester film having an easily adhesive layer which is excellent in antistatic property, suppresses transition of an antistatic agent in the easily adhesive layer to other article contacting the easily adhesive layer and a back surface of the film itself, and is excellent in adhesion to aqueous flexographic ink.SOLUTION: An aqueous flexographic easily adhesive polyester film has an easily adhesive layer on at least one surface of a polyester film, in which the easily adhesive layer is obtained by curing a composition containing an ion conductive antistatic agent, a polyester-based resin and a polycarbonate urethane resin, a surface resistivity of the surface of the easily adhesive layer is 1.0×1013 Ω / sq. or less, and a surface resistivity of the surface of the other polyester film contacting the surface of the easily adhesive layer after the other polyester film is brought into contact with the surface of the easily adhesive layer, and is held at 50°C under pressurization of 1 kg / cm2 for 3 days or more is 1.0×1014 Ω / sq. or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cavity-containing polyester film that is excellent in mass productivity, has opacity and whiteness, and is excellent in ease of adhesion and antistatic properties. More specifically, the present invention relates to a water-based flexographic ink-adhering polyester film that reduces the transfer of antistatic agents to other articles or the back surface and is particularly suitable as an information recording material or printing material due to its excellent adhesion to water-based flexographic inks. [Background technology]

[0002] Biaxially oriented polyester film possesses excellent properties such as mechanical properties, electrical properties, and dimensional stability, and is therefore used as a base film in many printing fields, including labels, tags, IC cards, magnetic recording materials, packaging materials, electrical insulation materials, photosensitive materials, drafting materials, and photographic materials. Especially when used for labeling, the opposite side of the easily adhesive layer may be treated with inorganic vapor deposition to enhance opacity, or an adhesive coating may be applied for attachment to containers, etc., or a release agent such as silicone may be applied, allowing it to be used as a release backing (separator).

[0003] However, in these applications, polyester film has high insulating properties, which can often lead to problems during printing, such as ink leakage due to dust adhesion caused by static electricity during various processes, or poor handling due to film adhesion caused by triboelectric charging.

[0004] Therefore, one known method for imparting easy adhesion and antistatic properties to the surface of a polyester film is to apply various resins to the surface of the polyester film to create a coating layer that has both easy adhesion and antistatic properties.

[0005] In various conventional ink adhesion type polyester coated films, a method of providing a coating layer made of a specific resin on the surface of a base polyester film is often seen (for example, see Patent Document 1). Examples of the constituent resin of the coating layer include polyester resins, polyurethane resins, acrylics, etc., which are used alone or in a mixture of two or more, and those obtained by mixing the resin with a specific crosslinking agent (such as melamine, isocyanate, etc.).

[0006] Also, in a polyester laminated film stretched in a uniaxial direction as a means for obtaining antistatic performance, it can also be obtained by mixing a polymer antistatic agent and an additive (see Patent Documents 2 and 3).

[0007] To impart an antistatic function, an antistatic agent having a polar group is used. Among them, in the case of an ion conductive type antistatic agent, cationic and anionic antistatic agents are known to be used as an effect of lowering the surface resistivity due to their high polarity. However, when an antistatic agent with a high polar group and high hydrophilicity is used and mixed with the above polyester resin or polyurethane resin, gelation may occur due to ion adsorption (interaction) from the difference in polarity species (functional groups), and there is also a problem that a coating solution cannot be prepared.

[0008] Furthermore, in such prior art, especially in the case of the film roll state in summer, during the storage of cut sheets, or during transportation such as land transportation or sea transportation, the components contained in the film surface and its coating layer may migrate to the back surface under the indoor temperature and humidity conditions of high temperature and high humidity. This is because back migration is unlikely to occur under normal temperature and humidity environments, but when the temperature and humidity exceed a certain range and the moisture content in the atmosphere further increases, the coating film components soften, which is considered to cause migration to the back surface. This phenomenon not only reduces the function of the coating layer, but especially when the antistatic agent component migrates to the back surface, problems such as evaporation failure (pinholes) when vapor deposition processing is performed in the next process, repelling phenomena due to poor appearance, and poor peelability due to poor curing when a release layer is applied will occur. That is, it was very difficult to suppress the migration property to the back surface of the easy-adhesive layer having the adhesion and antistatic functions such as printing ink on the polyester film. To avoid this, reducing the roll pressure or managing the temperature and humidity during storage is effective, but it cannot be completely avoided, and the problem was that it led to a deterioration in productivity.

[0009] A certain temperature range, for example, the temperature and humidity data inside a container transported by sea in summer are also disclosed by the transportation industry. Although the inside of the container is sealed, the temperature rises up to about 40°C at most. Furthermore, for humidity, the maximum humidity rises up to 80% due to the evaporation of the moisture contained in cardboard and other materials used for packaging. Therefore, in order to provide an easy-adhesive polyester film that is less likely to cause quality changes even under harsh environments, it is desirable to suppress the migration of the components in the coating layer to the back surface of other articles or the film itself under the evaluation conditions of a 50°C environment, and further under the hot and humid conditions of 60°C and 90% humidity.

[0010] When used for information recording materials and label applications, various printing methods and the inks used are selected. Generally, UV inks that crosslink acrylic monomer resins with a photoreaction catalyst are used, but due to odor and environmental impact, aqueous flexographic inks have come to be used.

[0011] Water-based flexographic inks are generally composed of pigment, pigment dispersion resin, water, humectant components, and binder resin. The binder resin is added to improve the coating durability of printed materials (water resistance, abrasion resistance, adhesion, scratch resistance, etc.), and resin fine particle dispersions are frequently used because they offer a good balance of excellent coating properties, ink properties, and printability. While these water-based flexographic inks have primarily been developed for substrates such as paper and cardboard, in recent years, there has been a demand for superior adhesion to non-polar film substrates such as polyethylene terephthalate under low-temperature drying conditions, from the perspectives of energy saving, low cost, and reduced environmental impact. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 11-105221 [Patent Document 2] Japanese Patent Publication No. 2008-296447 [Patent Document 3] Japanese Patent Publication No. 2010-208059 [Overview of the project] [Problems that the invention aims to solve]

[0013] The present invention was made against the backdrop of the problems of the prior art described above. Specifically, the object of the present invention is to provide an easy-to-adhere polyester film having an easy-to-adhere layer that has excellent antistatic properties on the surface of the easy-to-adhere layer, suppresses the migration of the antistatic agent in the easy-to-adhere layer to other films, separator paper, adhesive surfaces, or the back surface (back side) of the easy-to-adhere polyester film itself that come into contact with the easy-to-adhere layer, and has excellent adhesion to ultraviolet (UV) curing inks, water-based flexographic inks, etc. used in printing, etc. [Means for solving the problem]

[0014] In other words, the present invention consists of the following configuration. 1. A polyester film has an easy-adhesion layer on at least one surface, the easy-adhesion layer being formed by curing a composition containing an ion-conducting antistatic agent, a polyester resin, and a polycarbonate urethane resin, and the surface resistivity of the surface of the easy-adhesion layer is 1.0 × 10⁻⁶. 13 The density is Ω / sq or less, and the easy-adhesion layer surface is in contact with another polyester film at 50°C and 1 kg / cm². 2 After being held under pressure for 3 days, the surface resistivity of the other polyester film that was in contact with the surface of the easy-adhesion layer was 1.0 × 10⁻⁶. 14 A water-based flexographic ink-adhering polyester film with a density of Ω / sq or higher. 2. The surface of the easy-adhesion layer is brought into contact with another polyester film and bonded at 1 kg / cm² at 60°C and 90% humidity. 2 The surface resistivity of the easily adhering layer surface after being held under pressure for 3 days is 1.0 × 10⁻⁶. 13 The density is Ω / sq or less, and when another polyester film is brought into contact with the surface of the easy-adhesion layer, the density is 1 kg / cm² at 60°C and 90% humidity. 2 The surface resistivity of the other polyester film that was in contact with the surface of the easy-adhesion layer after being held under pressure for two days was 1.0 × 10⁻⁶. 13 A water-based flexographic ink-adhering polyester film as described in item 1 above, having a density of Ω / sq or greater. 3. The water-based flexographic ink-adhering polyester film according to the first or second above, wherein the solid content of the ion-conducting antistatic agent is 1 to 8% by mass when the total solid content of the composition is 100% by mass. 4. A water-based flexographic ink-adhering polyester film according to any one of the first to third claims above, wherein the total solid content of the composition is 100% by mass, and the crosslinking agent is present in an amount of 0 to 50% by mass as solid content. [Effects of the Invention]

[0015] The easily adhesive polyester film of the present invention exhibits excellent antistatic properties, suppresses the migration of the antistatic agent contained in the easily adhesive layer to other articles or the back surface even under high temperature and high humidity conditions, and provides excellent adhesion to UV-curing inks and water-based flexographic inks. [Modes for carrying out the invention]

[0016] (Polyester film substrate) 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 a copolymerized polyester resin in which a part of the diol component or dicarboxylic acid component of the above-mentioned polyester resin is replaced with the following copolymer components. For example, the copolymer components can include diol components such as diethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, and polyalkylene glycol, and dicarboxylic acid components such as adipic acid, sebatic acid, phthalic acid, isophthalic acid, 5-sodium isophthalic acid, and 2,6-naphthalenedicarboxylic acid.

[0017] In the present invention, the polyester resins suitably used for the polyester film substrate are mainly selected from polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate. Among these polyester resins, polyethylene terephthalate is the most preferred in terms of balancing physical properties and cost. Furthermore, the polyester film substrate composed of these polyester resins is preferably a biaxially oriented polyester film, which can improve chemical resistance, heat resistance, mechanical strength, and other properties.

[0018] While there are no particular limitations on the catalyst used for polycondensation in the production of polyester resins, antimony trioxide is preferred because it is inexpensive and has excellent catalytic activity. Germanium compounds or titanium compounds are also preferred. Even more preferred polycondensation catalysts include catalysts containing aluminum and / or its compounds and phenolic compounds, catalysts containing aluminum and / or its compounds and phosphorus compounds, and catalysts containing aluminum salts of phosphorus compounds.

[0019] Polyethylene resins, polypropylene resins, and polyester resins are used as the main raw materials in the manufacture of synthetic paper. In particular, polyester resins, such as polyethylene terephthalate, are used in a wide range of applications due to their excellent mechanical and thermal properties.

[0020] Methods for obtaining films with functions similar to paper generally include incorporating a large number of microscopic cavities into the film, or roughening a flat film by performing surface treatments such as sandblasting, chemical etching, or matting. Among these, the former method of incorporating a large number of microscopic cavities into the film is widely adopted because it not only provides paper-like opacity and whiteness, but also allows for lighter film weight, thus reducing costs per unit area, and provides appropriate flexibility and cushioning, resulting in superior image clarity during printing.

[0021] A common method for creating fine cavities within a film involves mixing an incompatible thermoplastic resin (hereinafter referred to as the incompatible resin) with a polyester resin to obtain a sheet in which the incompatible resin is dispersed in the polyester resin, and then stretching the sheet in at least one axial direction to create cavities through interfacial delamination between the polyester resin and the incompatible resin. For the incompatible resin used to create cavities in the polyester resin, polyolefin resins such as polyethylene resins, polypropylene resins, and polymethylpentene resins, as well as polystyrene resins, are preferably used.

[0022] In the present invention, the polyester film substrate is particularly preferably a biaxially oriented polyester film, from the viewpoint of practicality such as strength, stiffness, and dimensional stability.

[0023] The polyester film substrate can have a single-layer or laminated structure, but a laminated structure of A / B / A layers, in which the A layer contains inorganic particles and the B layer contains microcavities, is preferred. By placing a layer containing inorganic particles in the surface layer A, it is possible to improve the film's slipperiness, i.e., handling and opacity. By containing microcavities only in the inner layer B, a desirable white appearance can be obtained, and the film's cushioning properties can be achieved while ensuring the strength of the film surface. The method for forming the laminated structure is not particularly limited, but co-extrusion is preferred from the viewpoint of manufacturing stability and processing costs.

[0024] Furthermore, the polyester film substrate 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 indicating the opacity of the white cavity-containing polyester film is preferably 0.3 or higher, more preferably 0.3 to 4.0, and particularly preferably 0.5 to 3.0. An optical density of 0.3 or higher is preferable because it results in a clearer printing effect when printing is applied to the easily adhesive layer surface of the white cavity-containing polyester film. An optical density of 4.0 or lower is preferable because it can be expected to produce an even better printing effect.

[0025] The method for obtaining optical density within the above range is not particularly limited, but it can be achieved by incorporating inorganic particles or a thermoplastic resin that is incompatible with the polyester resin into the polyester resin. The content of these is not particularly limited, but in the case of inorganic particles, 5 to 35% by mass relative to the generated polyester is preferred, and particularly preferred, 8 to 25% by mass. On the other hand, when incorporating an incompatible thermoplastic resin, 5 to 35% by mass relative to the polyester is preferred, and particularly preferred, 8 to 28% by mass. Furthermore, when using inorganic particles and a thermoplastic resin incompatible with the polyester resin in combination, it is preferable that the total amount of these materials relative to the polyester film substrate be 40% by mass or less, from the viewpoint of film strength, stiffness, and film formation stability.

[0026] 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 dioxide, 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.

[0027] Furthermore, the easily adhering polyester film of the present invention has an apparent density of 0.3 to 1.3 g / cm³. 3 Preferably, it is an easily adhesive polyester film containing fine cavities.

[0028] Furthermore, an easily adhering white void-containing polyester film is also preferred, in terms of achieving both cushioning properties and surface peel strength, with a void layer density of 0.20 voids / μm or more, preferably 0.25 voids / μm or more, and more preferably 0.30 voids / μm or more. As a result, the obtained easily adhering white void-containing polyester film exhibits excellent print clarity and processing characteristics during printing. Here, the void layer density (voids / μm) is defined by the formula: number of voids in the film thickness direction (voids) / film thickness (μm). The upper limit of the void layer density is preferably 0.80 voids / μm, and more preferably 0.55 voids / μm, from the viewpoint of void formation efficiency. Methods for adjusting the density to the above range include adjusting the amount, type, and viscosity of the incompatible thermoplastic resin, as well as changing the screw shape of the extruder or installing a static mixer in the molten resin flow path, but are not limited to these methods.

[0029] These easily adhering white void-containing polyester films are particularly useful because the micro-voids contained within the film cause light scattering at the interface with the polyester matrix, resulting in significantly improved opacity and reducing the amount of inorganic particles that need to be added. Furthermore, by incorporating micro-voids, the base film itself can be made lighter, making it easier to handle and resulting in significant economic benefits such as reduced raw material costs and transportation costs.

[0030] As a method for obtaining such an easily adhesive white cavity-containing polyester film, known methods already disclosed can be used, such as a method in which a thermoplastic resin incompatible with the polyester resin, as described above, is kneaded with a thermoplastic polyester resin that serves as a matrix, and a sheet in which the incompatible resin is dispersed in the polyester resin as fine particles is stretched in at least one axial direction to generate cavities around the incompatible resin fine particles.

[0031] Furthermore, the thickness of the obtained water-based flexographic ink-adhering white cavity-containing polyester film is preferably 5 to 300 μm. In particular, the thickness of the white laminated polyester film having a cavity number density of 0.20 cubic cells / μm or more is preferably 20 to 300 μm, and more preferably 40 to 250 μm.

[0032] The required whiteness when used in printing materials can be expressed using color values. In particular, the color L value is a measure of lightness, and a higher value indicates whiter. Furthermore, a higher color b value indicates a stronger yellow tint, while a lower value indicates a stronger blue tint. In other words, a high L value and a low b value indicate high whiteness, meaning that the material appears whiter to the naked eye. This leads to improved clarity during printing.

[0033] (Easy adhesion layer) The water-based flexographic ink-easy adhesion polyester film of the present invention preferably has an easy adhesion layer formed by curing a composition containing an ion conductive antistatic agent, a polycarbonate urethane resin, and a polyester resin laminated on at least one side thereof in order to improve the back migration property of the antistatic agent, the adhesion to UV ink and water-based flexographic ink. The above-mentioned easy adhesion layer is considered to be formed by curing a cationic antistatic agent or an anionic antistatic agent, a polycarbonate urethane resin and a polyester resin. However, since it is difficult to represent the chemical structure itself after curing, it is expressed that a composition containing a cationic or anionic antistatic agent, a polycarbonate urethane resin, and a polyester resin is cured and formed. The easy adhesion layer may be provided on both sides of the polyester film substrate, provided only on one side of the polyester film substrate, and a different resin coating layer may be provided on the other side.

[0034] In the present invention, it is preferable that the water-based flexographic ink-easy adhesion polyester film has antistatic properties with a surface resistivity value of the surface of the easy adhesion layer of 1.0×10 13 Ω / sq or less. When the surface resistivity value of the surface of the easy adhesion layer is 1.0×10 13 Ω / sq or less, the wettability is good and the printing quality of the water-based flexographic ink is good, which is preferable. In addition, when the films are electrostatically adsorbed to each other, it is preferable that phenomena such as skew failure and double feeding during conveyance can be prevented. The surface resistivity value of the surface of the easy adhesion layer is more preferably 5.0×10 12 Ω / sq or less, and even more preferably 1.0×10 12 Ω / sq or less. On the other hand, when the surface resistivity value is 1.0×10 8 Ω / sq or more, the polarity does not become too high and the easy adhesion to various inks and the like is good, which is preferable. More preferably, it is 5.0×10 8 Ω / sq or more, and particularly preferably 1.0×10 9 Ω / sq or more.

[0035] In this invention, another polyester film is brought into contact with the surface of the easily adhering layer of a water-based flexographic ink-adhering polyester film at 50°C and 1 kg / cm². 2 After being held under pressure for 3 days, the surface resistivity of the easily adhering layer surface was 1.0 × 10⁻⁶. 13 It is preferable that the resistivity is Ω / sq or less. Having the above characteristics means that, for example, the antistatic agent present in the easily adhesive layer of an easily adhesive polyester film wound into a roll is less likely to migrate (transfer to the back) to the opposite side in contact, and the antistatic properties of the easily adhesive layer are easily maintained. The surface resistivity of the surface of the easily adhesive layer after contact treatment under the above specific conditions is 1.0 × 10⁻⁶. 13 A resistance of Ω / sq or less is preferable as it provides durable antistatic properties. The surface resistivity of the easily adhering layer surface after contact treatment under the specific conditions described above is more preferably 5.0 × 10 12 The coefficient of gravity is less than or equal to Ω / sq, and more preferably 1.0 × 10⁻⁶. 12 It is less than or equal to Ω / sq. On the other hand, the surface resistivity after contact treatment under the specific conditions described above is 1.0 × 10 8 A polarity of Ω / sq or higher is preferable because it does not become too polar, resulting in good adhesion with various inks, etc. A more preferable polarity is 5.0 × 10 8 The density is Ω / sq or greater, and particularly preferably 1.0 × 10⁻⁶. 9 It is greater than or equal to Ω / sq.

[0036] In this invention, another polyester film is brought into contact with the surface of the easily adhesive layer at 50°C and 1 kg / cm². 2 After being held under pressure for 3 days, the surface resistivity of the other polyester film that was in contact with the surface of the easy-adhesion layer was 1.0 × 10⁻⁶. 14It is preferable that the resistivity is Ω / sq or greater. Having the above characteristics means, for example, that the antistatic agent present in the easily adhering layer of a water-based flexographic ink easily adhering polyester film wound into a roll is less likely to migrate (transfer to the back) to the opposite side in contact, and thus the antistatic properties of the easily adhering layer of the water-based flexographic ink easily adhering polyester film are more easily maintained. The surface resistivity of the surface of the other polyester film after contact treatment under the above specific conditions is 1.0 × 10⁻⁶. 14 It is more preferable that the Ω / sq is greater than or equal to 5.0 × 10 14 It is even more preferable that the density is Ω / sq or greater.

[0037] In this invention, another polyester film is brought into contact with the surface of the easily adhering layer of a water-based flexographic ink-adhering polyester film, and the adhesion rate is 1 kg / cm² at 60°C and 90% humidity. 2 The surface resistivity of the easily bonded layer surface after being held under pressure for 3 days is 1.0 × 10⁻⁶. 13 It is preferable that the resistivity is Ω / sq or less. In the aforementioned humid and hot environment, it is thought that the antistatic agent in the easy-to-adhere layer is likely to migrate to other surfaces. Therefore, even after bonding treatment in the aforementioned humid and hot environment, the surface resistivity of the surface of the easy-to-adhere layer should be 1.0 × 10⁻¹⁰. 13 A resistance of Ω / sq or less means, for example, that even if an easily adhesive polyester film wound into a roll is left in a humid and hot environment, the antistatic agent present in the easily adhesive layer is less likely to migrate (transfer to the opposite side) and the antistatic properties of the water-based flexographic ink easily adhesive polyester film are easily maintained. The surface resistivity of the surface of the easily adhesive layer after the contact treatment in the humid and hot environment is 1.0 × 10⁻⁶ 13 It is more preferable that the value be Ω / sq or less, and 9.0 × 10 12 It is even more preferable that the resistivity is Ω / sq or less. On the other hand, the surface resistivity after contact treatment under the aforementioned moist heat conditions is 1.0 × 10 8 A polarity of Ω / sq or higher is preferable because it does not become too polar, resulting in good adhesion with various inks, etc. A more preferable polarity is 5.0 × 10 8 It is greater than or equal to Ω / sq.

[0038] In this invention, another polyester film is brought into contact with the surface of the easily adhering layer of a water-based flexographic ink-adhering polyester film, and the adhesion rate is 1 kg / cm² at 60°C and 90% humidity. 2 The surface resistivity of the other polyester film that was in contact with the surface of the easy-adhesion layer after being held under pressure for two days was 1.0 × 10⁻⁶. 13 It is preferable that the resistivity is Ω / sq or higher. In the aforementioned humid and hot environment, it is thought that the antistatic agent in the easy-to-adhere layer is likely to migrate to other surfaces. Therefore, the surface resistivity of the other polyester film that was in contact with the surface of the easy-to-adhere layer after the bonding treatment in the aforementioned humid and hot environment is 1.0 × 10⁻⁶. 13 A density of Ω / sq or higher means, for example, that even if an easily adhesive polyester film wound into a roll is left in a humid and hot environment, the antistatic agent present in the easily adhesive layer is less likely to migrate (transfer to the opposite side) and the antistatic properties of the water-based flexographic ink easily adhesive polyester film are easily maintained. More preferably, another polyester film is brought into contact with the surface of the easily adhesive layer of the water-based flexographic ink easily adhesive polyester film and the density is 1 kg / cm² at 60°C and 90% humidity. 2 The surface resistivity of the other polyester film that was in contact with the surface of the easy-adhesion layer after being held under pressure for 3 days was 1.0 × 10⁻⁶. 13 The density must be greater than or equal to Ω / sq.

[0039] In this invention, when evaluating the migration of the antistatic agent, the reason for contacting another polyester film with the easily adhering layer of the water-based flexographic ink easily adhering polyester film of the present invention is that it is conceivable that the polyester film of the present invention may have easily adhering layers on both surfaces, and in that case, it is difficult to accurately evaluate the water-based flexographic ink easily adhering polyester films of the present invention when they are stacked together. Therefore, as described later, in this case, the other polyester film used does not have an easily adhering layer.

[0040] The components of the easy-adhesion layer will be explained in detail below. (Ion-conducting antistatic agent) Preferred antistatic agents are those that can suppress migration to other articles they come into contact with or to the back surface of the film itself. Examples include nonionic surfactants such as sorbitan, ether, ester, sorbitol, and glucose types; cationic surfactants such as quaternary ammonium salts, quaternary ammonium resins, imidazoline, Arcover, and Solomin A types; anionic surfactants such as alkyl sulfates, alkyl phosphates, phosphate esters, and sulfate esters; and amphoteric surfactants such as betaine, amino acid, and aminosulfate esters.

[0041] In the above-mentioned antistatic agent, the counterion of the quaternary ammonium base is not particularly limited as long as it is an anionic compound, but preferably it can be appropriately selected from halogen ions, mono- or polyhalogenated alkyl ions, nitrate ions, sulfate ions, alkyl sulfate ions, sulfonate ions, or alkyl sulfonate ions. However, ethosulfate salts are preferred to maintain stability of surface resistivity, coating stability, ink adhesion, and to suppress migration of the antistatic agent to other articles or the back surface.

[0042] Furthermore, examples include polyethyleneimines, polydimethyldiallylammonium salts, polyalkylene polyamine dicyanodiamide ammonium condensates, polyvinylpyridium halides, alkyl quaternary ammonium (meth)acrylate salts, alkyl quaternary ammonium (meth)acrylamide salts, ω-chloro-poly(oxyethylene-polymethylene-alkyl quaternary ammonium salts), polyvinylbenzyltrimethylammonium salts, polystyrene-based cationic polymers, poly(meth)acrylic-based cationic polymers (methyl methacrylate, ethyl acrylate, 2-hydroxyethyl methacrylate, trimethylaminoethyl methacrylate chloride, etc.), polyvinylpyridine-based polymers, cyclic integral polymers, linear integral polymers, polymers of aromatic vinyl monomers having two or more quaternary ammonium ion groups in a pendant shape, and polymers having pyrrolidium 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 liquid and the easily adhering layer, it is preferable that the antistatic agent has a linear alkyl group, and more preferably that it has a linear alkyl group and a quaternary ammonium base.

[0043] Therefore, in an antistatic agent having a linear alkyl group and a quaternary ammonium base, the number of carbon atoms in the alkyl chain is preferably 10 to 25, more preferably 12 to 19, and particularly preferably 14 to 18. This range is preferable considering the interactions between the molecules and the suppression of back-side migration due to molecular length.

[0044] The molecular weight of the quaternary ammonium base having a linear alkyl group is preferably 200 or more, and more preferably 700 or less. More preferably 400 to 600. When the molecular weight is 200 or less, surface resistivity is easily achieved, but back migration cannot be suppressed. When the molecular weight is 700 or more, surface resistivity is difficult to achieve, and aggregation due to interaction with resin functional groups is more likely to occur during coating solution formulation.

[0045] Furthermore, in the molecular structure of a cationic antistatic agent containing a nitrogen element, at least one amide bond or urethane bond may be included between the linear alkyl chain and the quaternary ammonium base.

[0046] (Polycarbonate urethane resin) The urethane resin having a polycarbonate structure in the present invention preferably has a urethane bonding substructure derived from at least a polycarbonate polyol component and a polyisocyanate component, and further optionally contains a chain extender. Furthermore, a branched polyisocyanate is suitably introduced by forming a branched molecular chain structure after synthesis and polymerization, provided that any of the aforementioned raw material components constituting the molecular chain have three or more terminal functional groups.

[0047] In the present invention, the polycarbonate urethane resin, especially when it has a branched structure, preferably has a lower limit of 3 terminal functional groups in the molecular chain, and more preferably 4, due to its branched structure. Having 3 or more is preferable because it improves blocking resistance when water adheres to the resin. In the present invention, the urethane resin having a polycarbonate structure preferably has an upper limit of 6 terminal functional groups in the molecular chain, due to its branched structure. Having 6 or fewer is preferable because it allows the resin to be stably dispersed in an aqueous solution.

[0048] In the present invention, the polycarbonate polyol component used for synthesizing and polymerizing the polycarbonate urethane resin preferably contains an aliphatic polycarbonate polyol that has excellent heat resistance and hydrolysis resistance. Examples of aliphatic polycarbonate polyols include aliphatic polycarbonate diols and aliphatic polycarbonate triols, but aliphatic polycarbonate diols are preferably used. Examples of aliphatic polycarbonate diols used to synthesize and polymerize the polycarbonate structure urethane resin 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.

[0049] The number-average molecular weight of the polycarbonate polyol in the present invention is preferably 1000 to 3000. More preferably 1200 to 2900, and most preferably 1500 to 2800. A number-average molecular weight of 1000 or more is preferable because it can improve ink adhesion. A number-average molecular weight of 3000 or less is preferable because it can suppress the migration of the antistatic agent to the back surface.

[0050] Examples of polyisocyanates used in the synthesis and polymerization of polycarbonate urethane resin in the present invention include aromatic aliphatic diisocyanates such as xylylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate and 1,3-bis(isocyanate-methyl)cyclohexane, aliphatic diisocyanates such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, or polyisocyanates obtained by pre-adding these compounds, either individually or in combination, with trimethylolpropane or the like. When using the aforementioned aromatic aliphatic diisocyanates, alicyclic diisocyanates, or aliphatic diisocyanates, there is no problem of yellowing, which is preferable. Furthermore, the resulting coating does not become too hard, which is preferable as it is good for obtaining the surface resistivity value with an antistatic agent.

[0051] Examples of chain extenders 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; or water.

[0052] 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 and time, and then a compound having three or more functional hydroxyl groups or isocyanate groups is added to further allow the reaction to proceed.

[0053] 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, and polyethertriol. Examples of the aforementioned polyethertriol include compounds obtained by addition polymerization of one or more monomers such as ethylene oxide, propylene oxide, butylene oxide, amylene oxide, glycidyl ether, methylglycidyl ether, t-butylglycidyl ether, and phenylglycidyl ether, using one or more compounds having three active hydrogen atoms, such as glycerin, alcohols like trimethylolpropane, and diethylenetriamine, as initiators.

[0054] Specific examples of compounds having three or more functional isocyanate groups include polyisocyanate compounds having at least three isocyanate (NCO) groups in one molecule. In the present invention, examples of three or more functional isocyanate compounds include burettes, nurates, and adducts obtained by modifying isocyanate monomers such as aromatic diisocyanates, aliphatic diisocyanates, aromatic aliphatic diisocyanates, and alicyclic diisocyanates, which have two isocyanate groups. Examples of aromatic diisocyanates include 1,3-phenylenediisocyanate, 4,4'-diphenyldiisocyanate, 1,4-phenylenediisocyanate, 4,4'-diphenylmethanediisocyanate, 2,4-tolylenediisocyanate, 2,6-tolylenediisocyanate, 4,4'-toluidinediisocyanate, dianisidinediisocyanate, and 4,4'-diphenyletherdiisocyanate. 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'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylylene diisocyanate, and 1,3-tetramethylxylylene diisocyanate. Alicyclic diisocyanates include, for example, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (also known as IPDI or 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(isocyanate methyl)cyclohexane. A biuret compound is a self-condensate having a biuret bond formed by the self-condensation of isocyanate monomers. Examples include the biuret compound of hexamethylene diisocyanate. Nurates are trimers of isocyanate monomers, such as trimers of hexamethylene diisocyanate, isophorone diisocyanate, and tolylene diisocyanate. Adduct compounds are isocyanate compounds with three or more functions obtained by reacting the above-mentioned isocyanate monomer with a low-molecular-weight active hydrogen-containing compound with three or more functions. Examples include compounds obtained by reacting trimethylolpropane with hexamethylene diisocyanate, compounds obtained by reacting trimethylolpropane with tolylene diisocyanate, compounds obtained by reacting trimethylolpropane with xylylene diisocyanate, and compounds obtained by reacting trimethylolpropane with isophorone diisocyanate.

[0055] Chain extenders having three or more functional groups include trimethylolpropane, as described above, and alcohols having three or more hydroxyl groups, such as pentaerythritol.

[0056] In the present invention, the easily adhering layer is preferably provided by an in-line coating method described later using an aqueous coating solution. Therefore, it is desirable that the urethane resin of the present invention be water-soluble or water-dispersible. The above-mentioned "water-soluble or water-dispersible" means that it is dispersed in water or an aqueous solution containing less than 50% by mass of a water-soluble organic solvent.

[0057] To impart water dispersibility to urethane resin, sulfonic acid (salt) groups or carboxylic acid (salt) groups can be introduced (copolymerized) into the urethane molecular backbone. To maintain moisture resistance, it is preferable to introduce weakly acidic carboxylic acid (salt) groups, which also suppresses interaction (gelation) with cationic antistatic agents. Furthermore, nonionic groups such as polyoxyalkylene groups can also be introduced.

[0058] To introduce carboxylic acid (salt) groups into urethane resin, for example, a polyol compound having carboxylic acid groups, such as dimethylolpropanoic acid or dimethylolbutanoic acid, is introduced as a copolymer 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 individually or in combination of two or more.

[0059] When a polyol compound having a carboxylic acid (salt) group is used as a copolymer 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 60 mol%, and more preferably 5 to 40 mol%, when the total polyisocyanate component of the urethane resin is considered to be 100 mol%. A molar ratio of 3 mol% or more is preferable because it provides water dispersibility. Furthermore, a molar ratio of 60 mol% or less is preferable because it maintains water resistance and provides resistance to humid heat.

[0060] The urethane resin in this invention may have a blocked isocyanate structure at its ends to improve its rigidity.

[0061] (Crosslinking agent) In the present invention, a blocked isocyanate may be added as a crosslinking agent to the composition for forming an easily adhesive layer. A block isocyanate with three or more functions is more preferable, and a block isocyanate with four or more functions is particularly preferable. This makes it possible to control the antistatic properties of the surface of the easily adhesive layer and suppress the migration of the antistatic agent to the back surface.

[0062] In the present invention, the blocked isocyanate can be made water-soluble or water-dispersible by introducing hydrophilic groups into the precursor polyisocyanate. Examples of hydrophilic groups include (1) quaternary ammonium salts of dialkylamino alcohols and quaternary ammonium salts of dialkylaminoalkylamines, (2) sulfonates, carboxylates, phosphates, etc., and (3) polyethylene glycol and polypropylene glycol with one end sealed by an alkyl group. When hydrophilic moieties are introduced, the properties become (1) cationic, (2) anionic, or (3) nonionic. Among these, anionic and nonionic properties are preferred because many other water-soluble resins are anionic, allowing for easy compatibility. Furthermore, anionic properties offer excellent compatibility with other resins, and nonionic properties are preferred for improving heat and humidity resistance because they do not have ionic hydrophilic groups.

[0063] As anionic hydrophilic groups, those having a hydroxyl group for introduction into the polyisocyanate and a carboxylic acid group for imparting hydrophilicity are preferred. Examples include glycolic acid, lactic acid, tartaric acid, citric acid, oxybutyric acid, oxyvaleric acid, hydroxypivalic acid, dimethylolacetic acid, dimethylolpropanoic acid, dimethylolbutanoic acid, and polycaprolactone having a carboxylic acid group. Organic amine compounds are preferred for neutralizing the carboxylic acid group. Examples include linear, branched, primary, secondary, or tertiary amines having 1 to 20 carbon atoms, such as ammonia, methylamine, ethylamine, propylamine, isopropylamine, butylamine, 2-ethylhexylamine, cyclohexylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, and ethylenediamine; cyclic amines such as morpholine, N-alkylmorpholine, and pyridine; and hydroxyl-containing amines such as monoisopropanolamine, methylethanolamine, methylisopropanolamine, dimethylethanolamine, diisopropanolamine, diethanolamine, triethanolamine, diethylethanolamine, and triethanolamine.

[0064] The nonionic hydrophilic group preferably has 3 to 50 repeating units of ethylene oxide and / or propylene oxide of polyethylene glycol or polypropylene glycol, which are one-ended with an alkyl group, and more preferably 5 to 30. If the repeating units are small, the compatibility with the resin will be poor and the haze will increase, and if they are large, the adhesion under high temperature and high humidity conditions may decrease. Nonionic, anionic, cationic, and amphoteric surfactants can be added to the blocked isocyanate of the present invention to improve its water dispersibility. Examples include nonionic surfactants such as polyethylene glycol and polyhydric alcohol fatty acid esters, anionic surfactants such as fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, sulfosuccinates, and alkyl phosphates, cationic surfactants such as alkylamine salts and alkyl betaines, and surfactants such as carboxylic acid amine salts, sulfonic acid amine salts, and sulfate ester salts.

[0065] Furthermore, the mixture can contain water-soluble organic solvents other than water. For example, the organic solvent used in the reaction can be removed, and another organic solvent can be added.

[0066] Other disclosed compounds can be added to improve adhesion. Even with other crosslinking agents, adhesion under high temperature and high humidity conditions can be further improved to enhance the adhesion durability of the easily bonded layer. Specific crosslinking agents include urea-based, epoxy-based, melamine-based, oxazoline-based, and carbodiimide-based agents. Furthermore, catalysts can be used as needed to accelerate the crosslinking reaction.

[0067] (Polyester resin) The polyester resin used to form the easily adhesive layer in the present invention may be linear, but more preferably it is a polyester resin composed of a dicarboxylic acid and a branched diol. The dicarboxylic acid referred to here may be terephthalic acid, isophthalic acid, or 2,6-naphthalenedicarboxylic acid as its main component, as well as aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid. Furthermore, branched glycols are diols having branched alkyl groups, and examples 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.

[0068] The polyester resin, in the more preferred embodiment described above, contains branched glycol components in a proportion of preferably 10 mol% or more, and more preferably 20 mol% or more, of the total glycol components. A proportion of 10 mol% or more is preferable because it prevents excessive crystallinity and ensures good adhesion of the easily bondable layer. The upper limit of the glycol component in the total glycol components is preferably 80 mol% or less, and more preferably 70% by mass. A proportion of 80 mol% or less is preferable because it suppresses the concentration of oligomers, which are by-products, and ensures good transparency of the easily bondable layer. Among glycol components other than the above compounds, ethylene glycol is the most preferred. In small amounts, diethylene glycol, propylene glycol, butanediol, hexanediol, or 1,4-cyclohexanedimethanol may also be used.

[0069] The most preferred dicarboxylic acid as a component of the above-mentioned polyester resin is terephthalic acid or isophthalic acid. In addition to the above-mentioned dicarboxylic acid, it is preferable to copolymerize 5-sulfoisophthalic acid or the like in the range of 1 to 10 mol% in order to impart water dispersibility to the copolymerized polyester resin. Examples 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 suppress a decrease in adhesion to UV ink, the quantitative proportion of the dicarboxylic acid is preferably 5 mol% or less of the total carboxylic acid component, and it may not be necessary to use it.

[0070] The above-mentioned polyester resin may contain triols or tricarboxylic acids as constituent components, to the extent that the properties of the polyester resin are not impaired.

[0071] The above polyester resin may contain polar groups other than carboxyl groups. Examples include metal sulfonic acid bases and phosphate groups, and these may be present in one or more types. A method for introducing metal sulfonic acid bases is to use a dicarboxylic acid or glycol containing a metal sulfonic acid base, such as a metal salt of 5-sulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, 5-[4-sulfophenoxy]isophthalic acid, or a metal salt of 2-sulfo-1,4-butanediol, 2,5-dimethyl-3-sulfo-2,5-hexanediol, etc., in an amount of 10 mol% or less, preferably 7 mol% or less, and more preferably 5 mol% or less, of the total amount of the 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 film tend to decrease.

[0072] The resin solids concentration in the coating solution refers to the sum of the solids concentrations of the polyester resin, the urethane resin having a polycarbonate structure, and the crosslinking agent. It is desirable to adjust the resin solids concentration in the coating solution to 5-17%. A resin solids concentration of 5% or more is preferable because it prevents the thickness of the easily adhesive layer after drying and curing from becoming too thin, resulting in good adhesion to various materials such as UV-curing inks. On the other hand, a resin solids concentration of 17% or less is preferable because it allows for sufficient crosslinking when a crosslinking agent is included, suppresses the migration of the antistatic agent to other articles or the back surface, and also suppresses the blocking phenomenon.

[0073] When the total solid content in the composition for forming the easy-adhesion layer is taken as 100% by mass, it is desirable that the composition contains 1 to 8% by mass of an ion-conducting antistatic agent. Satisfying the specified range will provide antistatic performance. Furthermore, this range is preferable because it prevents the antistatic component from migrating to other articles or the back surface after heating and humid heat treatment.

[0074] When the total solid content mass of the three types of materials—polyester resin, urethane resin having a polycarbonate structure, and crosslinking agent—is 100% by mass, it is preferable that the content of the urethane resin having a polycarbonate structure is 5 to 50% by mass. Satisfying the above range is preferable because it allows for good affinity with various materials and UV inks, and good adhesion can be achieved. Within the above specified range, it is preferable that the material has excellent adhesion, antistatic properties, and the migration of the antistatic agent to other articles or the back surface is suppressed even under humid and hot conditions.

[0075] When the total solid content mass of the three components—polyester resin, urethane resin having a polycarbonate structure, and crosslinking agent—is 100% by mass, it is preferable that the upper limit of the crosslinking agent content is 50% by mass. Satisfying this range is preferable because it enhances the crosslinkability of the easily adhesive layer, resulting in good affinity with UV inks and the like, as well as easier development of antistatic properties. Furthermore, it is preferable that the strength of the easily adhesive layer is maintained during moisture resistance treatment, and the migration of the antistatic agent to other articles or the back surface is suppressed.

[0076] When the total solid content mass of the polyester resin, the urethane resin having a polycarbonate structure, and the three types of crosslinking agents is 100% by mass, it is preferable that the polyester resin content is 10 to 70% by mass. Satisfying this range allows for good affinity with various materials and UV inks, and achieves good adhesion. Adhesion to polyester film substrates is particularly improved, which is preferable. Furthermore, when a cationic antistatic agent is used, it is preferable that gelation of the coating liquid due to interactions can be suppressed.

[0077] (Additives) In the easy-adhesion layer of the present invention, known additives such as surfactants, pH adjusters, antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic particles, antistatic agents, nucleating agents, etc., may be added, provided that they do not impair the effects of the present invention.

[0078] The aforementioned surfactants may be used with the expectation of effects such as solubilizers, dispersants, defoamers, and wettability enhancers. Surfactants can be classified into those with ionic (cationic, anionic, or amphoteric) and nonionic hydrophilic portions. When used in water-based coating materials, polyester film is used as the base material because it has low surface energy and poor wettability. Therefore, surfactants are often used to adjust the surface tension of water-based coating materials and as wettability enhancers. Although not particularly limited, surfactants that can lower the surface tension of the coating liquid to 50 dyne / cm or less, preferably 40 dyne / cm or less, and promote wetting of the polyester film are preferred. Examples include alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkylbenzyldimethylammonium salts, monoalkyl sulfates, alkylpolyoxyethylene sulfates, alkylbenzene sulfonates, monoalkyl phosphates, alkyldimethylamine oxides, alkylcarboxybetaines, polyoxyethylene alkyl ethers, fatty acid sorbitan esters, alkyl polyglucosides, fatty acid diethanolamides, and alkyl monoglyceryl ethers, with polyether-modified silicones being particularly preferred.

[0079] The amount of surfactant added is preferably 0.1% by mass or more and 1.0% by mass or less, when the total mass of solids in the coating solution is taken as 100% by mass. More preferably, it is in the range of 0.2% by mass to 0.8% by mass. An amount of 0.1% by mass or more is preferable because it provides a wettability effect as a surfactant. An amount of 1.0% by mass or less is preferable because it maintains good adhesion.

[0080] In some cases, pH adjusters are used as additives. Acids used to adjust the pH include inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid, as well as organic acids such as oxalic acid, formic acid, citric acid, and acetic acid. For alkali adjustment, sodium carbonate, sodium bicarbonate, and sodium phosphinate are used. For water-based coatings, a neutral pH is preferable, ranging from 5 to 9, and more preferably 6 to 8.5. A pH below 5 may corrode the coating machine, and the blocking agent detachment-promoting effect is reduced when a blocked isocyanate is selected as a crosslinking agent. Furthermore, a pH above 9 is undesirable because it can cause hydrolysis of the polyester resin used as a resin binder, impairing adhesion and durability.

[0081] To reduce the glossiness of the easily adhesive layer, inert particles may be included in the easily adhesive layer.

[0082] The easy-adhesion layer may also contain lubricant particles to impart properties such as slipperiness, matte finish, and ink absorption to the surface. The particles may be inorganic or organic, and are not particularly limited, but examples include (1) inorganic particles such as silica, kaolinite, talc, light calcium carbonate, heavy calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, zinc sulfate, zinc carbonate, zirconium oxide, titanium dioxide, aluminum silicate, diatomaceous earth, calcium silicate, aluminum hydroxide, calcium carbonate, magnesium carbonate, calcium phosphate, magnesium hydroxide, and barium sulfate; and (2) organic particles such as acrylic or methacrylic, vinyl chloride, vinyl acetate, nylon, styrene / acrylic, styrene / butadiene, polystyrene / acrylic, polystyrene / isoprene, polystyrene / isoprene, methyl methacrylate / butyl methacrylate, melamine, polycarbonate, urea, epoxy, urethane, phenol, diallyl phthalate, and polyester. However, silica is particularly preferred to provide appropriate slipperiness to the easily bondable layer.

[0083] The average particle size of the inert particles is preferably 0.1 to 2.4 μm, and more preferably 0.3 to 2.0 μm. If the average particle size of the inert particles is 0.04 μm or less, the glossiness of the film surface may increase. Conversely, if it exceeds 2.4 μm, the particles tend to detach from the easy-adhesion layer, causing powder shedding during various processes such as film running.

[0084] The average particle diameter can be determined by morphological observation using a microscope such as a scanning electron microscope or a transmission electron microscope. Specifically, the average diameter of 20 particles arbitrarily selected in these microscopic observations is adopted. Furthermore, the particle shape is not particularly limited as long as it satisfies the purpose of the present invention, and spherical particles or irregularly shaped non-spherical particles can be used. The particle diameter of irregularly shaped particles can be calculated as the equivalent diameter of a circle. The equivalent diameter of a circle is obtained by dividing the area of ​​the observed particle by π, calculating the square root, and multiplying by 2.

[0085] If you want to increase the glossiness of the easily adhesive layer, it is also preferable not to include particles in the easily adhesive layer.

[0086] (Manufacturing of water-based flexographic ink-compatible polyester film) The method for producing the water-based flexographic ink-adhering polyester film of the present invention is arbitrary and not particularly limited, but a general method can be used in which a mixture having the above-mentioned composition is melted and extruded into a sheet to form an unstretched film, and then this unstretched film is stretched.

[0087] In the water-based flexographic ink-adhering 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 embodiments of the present invention, the polyester resin and the thermoplastic resin incompatible with the polyester resin were supplied in pellet form, but the invention is not limited thereto.

[0088] The raw materials fed into the extruder for melt molding into a film are prepared by mixing these resins into pellets according to the desired composition. However, when polyester resin and polyolefin resin are used as the raw materials for the polyester film of the present invention, the specific gravities of the resins differ significantly, so it is preferable to take measures to prevent segregation during the process of supplying the mixed pellets to the extruder. A suitable method for preventing segregation is to combine and knead some or all of the raw material resins in advance to form a masterbatch pellet. This method was used in the embodiments of the present invention, but it is not particularly limited as long as it does not hinder the effects of the present invention.

[0089] Furthermore, in the extrusion of mixed systems of these polyester resins and resins incompatible with polyester resins, even after mixing and finely dispersing them in a molten state, the resins have a tendency to re-aggregate due to their ability to reduce interfacial energy. This phenomenon occurs when extruding unstretched films, causing the cavity-forming agent to become coarsely dispersed and hindering the development of desired physical properties.

[0090] To prevent this, when forming the aforementioned mixed film, it is preferable to use a twin-screw extruder with a higher mixing efficiency to pre-disperse the cavity-forming agent. 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 measure. A static mixer or orifice can be used as the static mixer here. However, caution is necessary when using these methods, as heat-degraded resin may accumulate in the melt line.

[0091] Furthermore, since the incompatible resin, once dispersed in polyester resin as fine particles, tends to re-aggregate over time under low-shear melting conditions, reducing the residence time in the melt line from the extruder to the die is a fundamental solution. In the present invention, it is preferable to set the residence time in the melt line to 30 minutes or less, and more preferably to 15 minutes or less.

[0092] The conditions for stretching and oriented the unstretched film obtained as described above 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, in particular the method of stretching the unstretched film in the longitudinal direction and then in the width direction, as an example.

[0093] In the longitudinal stretching process, the film is stretched 2.5 to 5.0 times in the longitudinal direction using a roll heated to 80 to 120°C to obtain a uniaxially oriented film. The heating method may be either using a heated roll or a non-contact heating method, or a combination of both. Next, the uniaxially oriented film is introduced into a tenter and stretched 2.5 to 5.0 times in the width direction at a temperature of (Tm-10°C) or lower. Here, Tm refers to the melting point of polyester.

[0094] Furthermore, the biaxially oriented film described above is subjected to heat treatment as necessary. The heat treatment is preferably carried out in a tenter, and preferably in the range of (Tm-60℃) to Tm.

[0095] The easy-adhesion layer can be formed after the film is manufactured or during the manufacturing process. In particular, from the viewpoint of productivity, it is preferable to apply the coating solution to at least one side of the PET film after it has been unstretched or uniaxially stretched, and to form the easy-adhesion layer at any stage in the film manufacturing process.

[0096] Any known method can be used to apply this coating solution to the polyester film. Examples include the reverse roll coating method, gravure coating method, kiss coating method, die coater method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, impregnation coating method, curtain coating method, and the like. These methods can be used individually or in combination.

[0097] In the present invention, the thickness of the easy-adhesion layer can be appropriately set in the range of 0.001 to 2.00 μm, but to achieve both processability and adhesion, the range of 0.01 to 1.00 μm is preferable, more preferably 0.02 to 0.80 μm, and even more preferably 0.05 to 0.50 μm. A thickness of 0.001 μm or more of the easy-adhesion layer is preferable because it provides good adhesion. A thickness of 2.00 μm or less of the easy-adhesion layer is preferable because it can suppress migration of the antistatic agent to other articles or the back surface. [Examples]

[0098] 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 method used in the present invention will be described below.

[0099] (1) Antistatic properties Surface resistivity Three 5.00 cm squares of film were cut out and used as samples. The surface resistivity was measured for each of the three samples using a surface resistance meter (Nitto Seiko Analytic High Resta MCP-HT800) under an applied voltage of 500V, 23°C, and 65% humidity, in accordance with JIS K6911, and the average value was taken.

[0100] (2) Evaluation of easy-to-adhere layer surface and migration properties to other surfaces under a 50°C pressurized environment Three 5.00 cm squares of film were cut out to form samples. These were then placed on top of Toyobo Co., Ltd.'s polyester film E5001 (thickness 50 μm) and the surface of the easy-adhesion layer of the samples. The samples were then subjected to a drying process using a Yamato Scientific Co., Ltd. dry oven DVS602 at 50°C at a rate of 1 kg / cm². 2 The samples were held under pressure for 3 days. The surface resistivity of the easily adhesive layer surface of the sample and the surface of the Toyobo polyester film E5001 in contact with it was measured using a surface resistance meter (Nitto Seiko Analyx Highresta MCP-HT800) in accordance with JIS K6911, with an applied voltage of 500V, 23℃, and 65% humidity, and the average value was calculated for three samples of each. Regarding the easily adhering layer surface of the sample, ○ : 1.0 × 10 13 Ω / sq or less × : 1.0 × 10 13 Exceeding Ω / sq Regarding the surface that E5001 came into contact with, ○: 1.0 × 10 14 Ω / sq or more × : 1.0 × 10 14 Less than Ω / sq That was their assessment.

[0101] (3) Evaluation of easy-to-adhere layer surface and migration to other surfaces under pressure in a humid, heat-resistant environment. Three 5cm squares were cut from the film to form a sample. These were then superimposed on the surface of the easy-adhesion layer of the sample and a polyester film E5001 (thickness 50μm) manufactured by Toyobo Co., Ltd. The sample was then tested at 60°C and 90% humidity using a constant temperature and humidity chamber IG400 manufactured by Yamato Scientific Co., Ltd., at a temperature of 60°C and 90% humidity, with a density of 1 kg / cm². 2 Samples were prepared that were held under pressure for two days and those that were held for three days. The surface resistivity of the easily adhesive layer of the sample and the surface of the Toyobo polyester film E5001 in contact with it was measured using a surface resistance meter (Nitto Seiko Analyx High Resta MCP-HT800) under an applied voltage of 500V, 23℃, and 65% humidity, in accordance with JIS K6911, with three samples measured and the average value calculated. For the easily adhering layer surface of the sample, measurements were taken on samples that were stacked and held for 3 days. ○ : 1.0 × 10 13 Ω / sq or less × : 1.0 × 10 13 Exceeding Ω / sq For the surfaces that were in contact with E5001, measurements were taken for both surfaces that were stacked for 2 days and surfaces that were stacked for 3 days. ○: 1.0 × 10 when stacked over 3 days 14 Ω / sq or more △: 1.0 × 10 when stacked over 3 days 14 The value is less than Ω / sq, and when superimposed over two days, it equals 1.0 × 10⁻⁶. 13 Ω / sq or more ×: The result of stacking two days is 1.0 × 10 13 Less than Ω / sq He evaluated it as such.

[0102] (4) Adhesion with UV ink On the easy-adhesion layer of an easy-adhesion polyester film, UV ink [manufactured by T&K TOKA Co., Ltd., product name "BEST CURE UV161 Indigo S"] was used to print on a printing press [manufactured by Akira Seisakusho Co., Ltd., product name "RI Tester"], and then a high-pressure mercury lamp was used to apply 40 mJ / cm² to the film coated with the ink layer. 2 The UV-curing ink was cured by irradiating it with ultraviolet light. Next, a piece of Nichiban cellophane adhesive tape (CT405AP-24) measuring 24 mm in width and 50 mm in length was cut and completely attached to the ink layer surface using a handy rubber roller, ensuring no air was trapped inside. After that, the cellophane adhesive tape was peeled off vertically, and the remaining area of ​​the printed layer in the 24 mm x 50 mm area was observed and judged according to the following criteria. ○: A print was considered acceptable if the remaining area of ​​the printed layer was 99% or more of the total area. △: The product was deemed acceptable if the remaining area of ​​the printed layer was between 90% and 99% of the total area. ×: Failed because the remaining area of ​​the printed layer was less than 90% of the total area.

[0103] (5) Adhesion with water-based flexographic inks On the easy-adhesion layer of an easy-adhesion polyester film, printing was performed using a water-based flexographic ink for surface printing [manufactured by Dainichi Seika Kogyo Co., Ltd., product name "Hydric FCG"] on a printing press [manufactured by Matsuo Sangyo Co., Ltd., product name "K Printing Proofer"] with a 150-line metal plate. The ink layer was then cured by heating it in a dryer oven at 100°C for 30 seconds. Next, a piece of Nichiban cellophane adhesive tape (CT405AP-24) measuring 24 mm in width and 50 mm in length was cut and completely attached to the surface of the ink layer using a handy rubber roller, ensuring that no air was trapped inside. After that, the cellophane adhesive tape was peeled off vertically, and the remaining area of ​​the printed layer in a 24 mm x 50 mm area was observed and judged according to the following criteria. ○: A print was considered acceptable if the remaining area of ​​the printed layer was 99% or more of the total area. △: The product was deemed acceptable if the remaining area of ​​the printed layer was between 90% and 99% of the total area. ×: Failed because the remaining area of ​​the printed layer was less than 90% of the total area.

[0104] (Cationic antistatic agent A-1) An esterification reaction was carried out at 100°C under a nitrogen atmosphere for 10 hours using 116 g of N,N-dimethyl-1,3-propanediamine and 285 g of C17 stearic acid. Tetrahydrofuran was added as the quaternization solvent, and a specified amount of dimethyl sulfuric acid was added to the target amine. The reaction was carried out at 70°C for approximately 10 hours. After the reaction, the solvent was removed by distillation under reduced pressure, and isopropanol was added to adjust the solid content to the desired level to obtain an isopropanol solution of a cationic antistatic agent (A-1) having a quaternary ammonium ethosulfate salt.

[0105] (Cationic antistatic agent A-2) Using 89 g of dimethylaminoethanol and 228 g of myristic acid with 14 carbon atoms, the same treatment was performed on the other A-1 to obtain a cationic antistatic agent (A-2) solution containing a quaternary ammonium ethosulfate salt.

[0106] (Cationic antistatic agent A-3) An esterification reaction was carried out at 200°C under a nitrogen atmosphere for 10 hours using 89 g of dimethylaminoethanol and 354 g of tricosylic acid with 23 carbon atoms. Tetrahydrofuran was added as the quaternization solvent, and a specified amount of dimethyl sulfuric acid was added to the target amine. The reaction was carried out at 70°C for approximately 10 hours. The same procedure as for A-1 was carried out to obtain an isopropanol solution of a cationic antistatic agent (A-3) having a quaternary ammonium ethosulfate salt.

[0107] (Anionic antistatic agent A-4) Sodium dodecylbenzenesulfonate (TB702, manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd.) was used.

[0108] (Quaternary cation chlorine-based antistatic agent A-5) Lauryltrimethylammonium chloride (Kachiogen® TML, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used.

[0109] (Polymerization of urethane resin B-1 having a polycarbonate structure) In a four-necked flask equipped with a stirrer, a Liebig condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 22 parts by mass of 4,4-dicyclohexylmethane diisocyanate, 20 parts by mass of polyethylene glycol monomethyl ether with a number average molecular weight of 700, 53 parts by mass of polyhexamethylene carbonate diol with 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. The mixture was stirred at 75°C under a nitrogen atmosphere for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, 16 parts by mass of a polyisocyanate compound having an isocyanurate structure (Duranate TPA, manufactured by Asahi Kasei Chemicals, trifunctional), which was produced using hexamethylene diisocyanate as a raw material, was added. The mixture was stirred at 75°C under a nitrogen atmosphere for 1 hour, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Subsequently, the reaction solution temperature was lowered to 50°C, and 7 parts by mass of methyl ethyl ketoxime were added dropwise. After cooling the reaction mixture to 40°C, a polyurethane prepolymer solution was obtained. 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 for 2000 min.-1 While stirring and mixing, the polyurethane prepolymer solution was added and dispersed in water. Then, under reduced pressure, a solution of 35% by mass of water-dispersible urethane resin (B-1) was prepared by removing some of the acetone and water.

[0110] (Polymerization of urethane resin B-2 having a polycarbonate structure) In a four-necked flask equipped with a stirrer, a Liebig condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 25 parts by mass of 4,4-dicyclohexylmethane diisocyanate, 5 parts by mass of dimethylolpropanoic acid, 52 parts by mass of polyhexamethylene carbonate diol with a number average molecular weight of 2600, 6 parts by mass of neopentyl glycol, and 84.00 parts by mass of acetone as a solvent were added. The mixture was stirred at 75°C under a nitrogen atmosphere for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, 18 parts by mass of a polyisocyanate compound having an isocyanurate structure (Duranate TPA, manufactured by Asahi Kasei Chemicals, trifunctional), which was derived from hexamethylene diisocyanate, was added. The mixture was stirred at 75°C under a nitrogen atmosphere for 1 hour, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Subsequently, the reaction solution temperature was lowered to 50°C, and 8 parts by mass of methyl ethyl ketoxime were added dropwise. After cooling the reaction solution to 40°C, 5.17 parts by mass of triethylamine were 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 for 2000 min. -1 While stirring and mixing, the polyurethane prepolymer solution was added and dispersed in water. Then, under reduced pressure, a solution of 35% by mass of water-dispersible urethane resin (B-2) was prepared by removing some of the acetone and water.

[0111] (Polymerization of urethane resin B-3 that does not contain polycarbonate polyol components) 75 parts by mass of a 5000 molecular weight polyester polyol composed of terephthalic acid, isophthalic acid, ethylene glycol, and neopentyl glycol, 30 parts by mass of hydrogenated m-xylylene diisocyanate, 7 parts by mass of ethylene glycol, 6 parts by mass of dimethylolpropionic acid, 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 reached the predetermined amine equivalent. After cooling the reaction solution to 40°C, 5.17 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 for 2000 min. -1 While stirring and mixing, the polyurethane prepolymer solution was added and dispersed in water. Then, under reduced pressure, a solution of 35% by mass of water-dispersible urethane resin (B-3) was prepared by removing some of the acetone and water.

[0112] (Preparation of polyurethane block isocyanate (B-4) having a polyester structure) 200 parts by mass of a polyester (molecular weight 2000) of a bisphenol A ethylene oxide 2-mol adduct and maleic acid was mixed with 33.6 parts by mass of hexamethylene diisocyanate, and the reaction was carried out at 100°C for 2 hours. The temperature of the system was then lowered to 50°C, 73 parts by mass of a 30% sodium bisulfite aqueous solution was added, and the mixture was stirred at 45°C for 60 minutes. The mixture was then diluted with 718 parts by mass of water to obtain an aqueous dispersion of block polyisocyanate (B-4) with a solid content of 20.0% by mass. The number of functional groups of this block isocyanate crosslinking agent is 2, and the NCO equivalent is 1300.

[0113] (Polymerization of blocked isocyanate crosslinking agent C-1) In a flask equipped with a stirrer, thermometer, and reflux condenser, 66.04 parts by mass of a polyisocyanate compound having an isocyanurate structure derived from hexamethylene diisocyanate (Duranate TPA, manufactured by Asahi Kasei Chemicals) and 17.50 parts by mass of N-methylpyrrolidone were added dropwise to 95 parts by mass of 3,5-dimethylpyrazole (dissociation temperature: 120°C, boiling point: 218°C), and the mixture was held at 70°C for 1 hour under a nitrogen atmosphere. Subsequently, 30 parts by mass of dimethylolpropanoic acid were added dropwise. After measuring the infrared spectrum of the reaction solution and confirming that the absorption of the isocyanate group had disappeared, 5.59 parts by mass of N,N-dimethylethanolamine and 132.5 parts by mass of water were added to obtain an aqueous dispersion of block polyisocyanate (C-1) with a solid content of 40% by mass. The number of functional groups of this block isocyanate crosslinking agent is 4, and the NCO equivalent is 280.

[0114] (Polymerization of blocked isocyanate crosslinking agent C-2) In a flask equipped with a stirrer, thermometer, and reflux condenser, 100 parts by mass of a polyisocyanate compound having an isocyanurate structure derived from hexamethylene diisocyanate (Duranate TPA, manufactured by Asahi Kasei Chemicals), 55 parts by mass of propylene glycol monomethyl ether acetate, and 30 parts by mass of polyethylene glycol monomethyl ether (average molecular weight 750) were charged and held at 70°C for 4 hours under a nitrogen atmosphere. The reaction mixture temperature was then lowered to 50°C, and 47 parts by mass of methyl ethyl ketoxime were added dropwise. The infrared spectrum of the reaction mixture was measured to confirm the disappearance of absorption of the isocyanate group. 210 parts by mass of water were added to obtain an aqueous dispersion of the oxime-blocked isocyanate crosslinking agent (C-2) with a solid content of 40% by mass. The number of functional groups in this blocked isocyanate crosslinking agent is 3, and its NCO equivalent is 170.

[0115] (Polymerization of polyester resin D-1) In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 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, 185 parts by mass of neopentyl glycol, 188 parts by mass of ethylene glycol, and 0.2 parts by mass of tetra-n-butyl titanate were charged, and a transesterification reaction was carried out at a temperature of 160°C to 220°C for 4 hours. The temperature was then raised to 255°C, the reaction system was gradually depressurized, and the reaction was carried out under a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain copolymerized polyester resin (D-1). The obtained copolymerized polyester resin (D-1) was pale yellow and transparent. The reduced viscosity of copolymerized polyester resin (D-1) was measured to be 0.40 dl / g. The glass transition temperature determined by DSC was 65°C.

[0116] (Preparation of polyester aqueous dispersion Dw-1) In a reactor equipped with a stirrer, thermometer, and reflux device, 25 parts by mass of copolymerized polyester resin (D-1) and 10 parts by mass of ethylene glycol n-butyl ether were added and heated at 110°C, stirring to dissolve the resin. After the resin was completely dissolved, 65 parts by mass of water were gradually added to the polyester solution while stirring. After the addition, the liquid was cooled to room temperature while stirring to prepare a milky white polyester aqueous dispersion (Dw-1) with a solid content of 25% by mass.

[0117] (Polymerization of polyester resin D-2) In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 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 were charged, and a transesterification reaction was carried out at a temperature of 160°C to 220°C for 4 hours. The temperature was then raised to 255°C, the reaction system was gradually depressurized, and the reaction was carried out under a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain copolymerized polyester resin (D-2). The obtained copolymerized polyester resin (D-2) was pale yellow and transparent. The reduced viscosity of copolymerized polyester resin (D-2) was measured to be 0.70 dl / g. The glass transition temperature determined by DSC was 40°C.

[0118] (Preparation of polyester aqueous dispersion Dw-2) In a reactor equipped with a stirrer, thermometer, and reflux device, 25 parts by mass of copolymerized polyester resin (D-2) and 10 parts by mass of ethylene glycol n-butyl ether were added and heated at 110°C, stirring to dissolve the resin. After the resin was completely dissolved, 65 parts by mass of water were gradually added to the polyester solution while stirring. After the addition, the liquid was cooled to room temperature while stirring to prepare a milky white polyester aqueous dispersion (Dw-2) with a solid content of 25% by mass.

[0119] (Example 1) The solid content of the compounds constituting the coating layer in the coating solution is as follows: The total amount of solids contained in the coating layer is assumed to be 100% by mass. • Cationic antistatic agent A-1: ​​6.2% by mass • Polycarbonate structured urethane resin B-1: 22.8% by mass • Blocked isocyanate crosslinking agent C-1: 22.8% by mass • Polyester resin D-1: 45.4% by mass • Silicone-based surfactant: 0.4% by mass • pH adjuster (sodium bicarbonate): 2.4% by mass The solid content mass ratio of urethane resin (B-1), crosslinking agent (C-1), and polyester resin (D-1) is 25 / 25 / 50.

[0120] (1) Manufacturing of white void-containing polyester film (F-1) (Preparation of master pellets) A pellet mixture consisting of 60% by mass of polymethylpentene resin (Mitsui Chemicals, DX820) with a melt viscosity (ηO) of 1,300 poise, 20% by mass of polystyrene resin (Nippon Polysty Co., Ltd., G797N) with a melt viscosity (ηS) of 3,900 poise, and 20% by mass of polypropylene resin (Grand Polymer Co., Ltd., J104WC) with a melt viscosity of 2,000 poise was supplied to a vented twin-screw extruder heated to 285°C for pre-mixing. This molten resin was continuously supplied to a vented single-screw mixer, mixed and extruded, and the resulting strands were cooled and cut to prepare a cavity-forming agent master pellet (M1).

[0121] Furthermore, 50% by mass of polyethylene terephthalate resin with an intrinsic viscosity of 0.62 dl / g, manufactured by a known method, was mixed with 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. This mixture was then supplied to a vented twin-screw extruder for pre-mixing. This molten resin was continuously supplied to a vented single-screw mixer, mixed, and extruded. The resulting strands were cooled and cut to prepare titanium dioxide-containing master pellets (M2).

[0122] (Preparation of film raw materials) 81% by mass of the polyethylene terephthalate resin with an intrinsic viscosity of 0.62 dl / g, which was vacuum-dried at 140°C for 8 hours, 9% by mass of the master pellet (M1), which was vacuum-dried at 90°C for 4 hours, and 10% by mass of the master pellet (M2) were mixed together to form a film raw material (G1).

[0123] (Preparation of unstretched film) The aforementioned film raw material (G1) was heated to 285°C in an extruder for layer B, and a mixture of 70% by mass of the same polyethylene terephthalate resin used in the film raw material (G1) and 30% by mass of the above-mentioned master pellet (M2) was separately supplied to an extruder for layer A, heated to 290°C. The molten resin discharged from the extruder for layer B was guided through an orifice, and the resin discharged from the extruder for layer A was guided through a static mixer to a feed book, and the layer made of film raw material (G1) (layer B) and the layer made of polyethylene terephthalate resin and master pellet (M2) (layer A) were laminated in the order of layer A / layer B / layer A.

[0124] The molten resin was co-extruded in sheet form from a T-die onto a cooling roll heated to 25°C, and solidified using 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. The molten resin remained in the melt line for approximately 12 minutes, and the shear rate from the T-die was approximately 150 / second.

[0125] (Preparation of biaxially oriented film) The obtained unstretched film was uniformly heated to 65°C using a heated roll and longitudinally stretched 3.4 times between two pairs of nip rolls with different peripheral speeds (low-speed roll: 2 m / min, high-speed roll: 6.8 m / min). At this time, as an auxiliary heating device for the film, an infrared heating heater (rated output: 20 W / cm) equipped with a gold reflective film in the middle of the nip roll was installed facing both sides of the film, 1 cm from the film surface, and heated. On one side of the uniaxially oriented film obtained in this way, a wet coating of 7 g / m² was applied using the reverse gravure coating method with the above coating configuration. 2 After coating the material, it was guided into a tenter, dried while being heated to 150°C and transversely stretched 3.7 times, the width was fixed and heat-treated at 220°C for 5 seconds, and then relaxed by 4% in the width direction at 200°C to obtain an easily adhesive polyester film with a thickness of 50 μm. This film has excellent whiteness, and due to the formation of voids, the apparent density is 1.10 g / cm³. 3 The optical density is 0.8, and the coating thickness after drying is 0.12 g / m². 2A water-based flexographic ink-adhering polyester film was obtained. The evaluation results are shown in Table 1.

[0126] (Examples 2-26) An easily adhesive polyester film was obtained in the same manner as in Example 1, except that the coating layer configuration was changed as shown in Table 1.

[0127] (Example 27) The solid content of the compounds constituting the coating layer in the coating solution is as follows: The total amount of solids contained in the coating layer is assumed to be 100% by mass. • Colloidal silica particles (E-1) (average particle size: 450 nm): 48.8% by mass • Cationic antistatic agent A-1: ​​2.1% by mass • Polycarbonate structured urethane resin B-1: 12.2% by mass • Blocked isocyanate crosslinking agent C-1: 12.2% by mass • Polyester resin D-1: 24.4% by mass • Silicone-based surfactant: 0.1% by mass • pH adjuster (sodium bicarbonate): 0.2% by mass The mass ratio of urethane resin (B-1) / crosslinking agent (C-1) / polyester resin (D-1) is 25 / 25 / 50. The above coating layer configuration is used, with a wet coating amount of 10 g / m². 2 Except for the change made to the following, the coating thickness after drying was 0.55 g / m², similar to Example 1. 2 An easily adhering polyester film was obtained. Furthermore, a matte coating layer was obtained with a gloss value of 9.0 at 60-degree specular reflection of the coated layer surface.

[0128] (Example 28) The solid content of the compounds constituting the coating layer in the coating solution is as follows: The total amount of solids contained in the coating layer is assumed to be 100% by mass. • Benzoquanamine particles (E-2) (average particle size: 1.2 μm): 38.3% by mass • Cationic antistatic agent A-1: ​​2.1% by mass • Polycarbonate structured urethane resin B-1: 14.8% by mass • Blocked isocyanate crosslinking agent C-1: 14.8% by mass • Polyester resin D-1: 29.6% by mass • Silicone-based surfactant: 0.1% by mass • pH adjuster (sodium bicarbonate): 0.3% by mass The mass ratio of urethane resin (B-1) / crosslinking agent (C-1) / polyester resin (D-1) is 25 / 25 / 50. The above coating layer configuration is used, with a wet coating amount of 12 g / m². 2 Except for the change, the coating thickness after drying was 0.93 g / m², similar to Example 1. 2 An easily adhering polyester film was obtained. Furthermore, a matte coating layer was obtained with a gloss value of 14.0 at 60-degree specular reflection of the coated layer surface.

[0129] (Example 29) A water-based flexographic ink-adhering polyester film was obtained in the same manner as in Example 27, except that the coating layer configuration in Table 1 was changed.

[0130] (Example 30) A water-based flexographic ink-adhering polyester film was obtained in the same manner as in Example 28, except that the coating layer configuration in Table 1 was changed.

[0131] (Example 31) The solid content of the compounds constituting the coating layer in the coating solution is as follows: The total amount of solids contained in the coating layer is assumed to be 100% by mass. • Colloidal silica particles E-3 (average particle size: 100 nm): 1.6% by mass • Cationic antistatic agent A-1: ​​6.2% by mass • Polycarbonate structured urethane resin B-1: 25.3% by mass • Blocked isocyanate crosslinking agent C-2: 10.8% by mass • Polyester resin D-1: 54.2% by mass • Silicone-based surfactant: 0.4% by mass • pH adjuster: 1.6% by mass (sodium bicarbonate) The mass ratio of urethane resin (B-1) / crosslinking agent (C-2) / polyester resin (D-1) is 28 / 12 / 60.

[0132] (2) Manufacturing of polyester film that is substantially free of particles (F-2) As a film raw material polymer, PET resin pellets with an intrinsic viscosity (solvent: phenol / tetrachloroethane = 60 / 40) of 0.62 dl / g and substantially free of particles were dried at 135°C for 6 hours under reduced pressure of 133 Pa. Subsequently, the pellets were fed into an extruder and melt-extruded into a sheet at approximately 280°C. They were then rapidly cooled and solidified on a rotating, cooled metal roll maintained at a surface temperature of 20°C to obtain an unstretched PET sheet. The unstretched PET sheet was heated to 100°C using a heated roll group and an infrared heater, and then stretched 3.5 times in the longitudinal direction using a roll group with different peripheral speeds to obtain a uniaxially oriented PET film. Next, using the coating liquid composition with the solid content described above, a wet coating amount of 7 g / m² was applied by reverse gravure coating. 2 After coating the material, it was guided into a tenter, dried while being heated to 150°C and transversely stretched 3.7 times, the width was fixed and heat-treated at 220°C for 5 seconds, and then further relaxed by 4% in the width direction at 200°C to obtain an easily adhesive polyester film with a film thickness of 50 μm. This film has excellent transparency and an apparent specific gravity of 1.42 g / cm³. 3 The total light transmittance is 91%, and the thickness of the coated layer after drying is 0.12 g / m². 2 We obtained a water-based flexographic ink-adhering polyester film.

[0133] (Comparative Examples 1-7) A polyester film was obtained in the same manner as in Example 1, except that the coating layer configuration in Table 1 was changed.

[0134] [Table 1] [Industrial applicability]

[0135] The present invention provides a water-based flexographic ink-adhering polyester film that offers excellent mass productivity, can provide labels and stickers, and exhibits excellent antistatic properties even when stored in humid and hot environments, and provides a water-based flexographic ink-adhering polyester film with minimal change in surface quality of the easily adhesive layer.

Claims

1. A polyester film has an easy-adhesion layer on at least one surface, the easy-adhesion layer is formed by curing a composition containing an ion-conducting antistatic agent, a polyester resin, and a polycarbonate urethane resin, and the surface resistivity of the surface of the easy-adhesion layer is 1.0 × 10⁻¹⁰ １３ The density is Ω / sq or less, and the easy-adhesion layer surface is in contact with another polyester film at 50°C and 1 kg / cm². ２ After being held under pressure for three days, the surface resistivity of the other polyester film that was in contact with the surface of the easy-adhesion layer was 1.0 × 10⁻¹⁰. １４ It is greater than or equal to Ω / sq, The ion-conducting antistatic agent is an antistatic agent having a linear alkyl group, wherein the number of carbon atoms in the alkyl group is 10 to 25. An easily adhesive polyester film used in printing with water-based flexographic inks.

2. The surface of the easy-adhesion layer is brought into contact with another polyester film and subjected to a temperature of 60°C and 90% humidity at a rate of 1 kg / cm². ２ The surface resistivity of the easily adhering layer surface after being held under pressure for 3 days is 1.0 × 10⁻⁶. １３ The density is Ω / sq or less, and when another polyester film is brought into contact with the surface of the easy-adhesion layer, the density is 1 kg / cm² at 60°C and 90% humidity. ２ The surface resistivity of the other polyester film that was in contact with the surface of the easy-adhesion layer after being held under pressure for two days was 1.0 × 10⁻¹⁰. １３ An easily adhering polyester film used for printing with a water-based flexographic ink as described in claim 1, having a density of Ω / sq or greater.

3. An easily adhering polyester film for printing using a water-based flexographic ink according to claim 1 or 2, wherein the solid content of the ion-conducting antistatic agent is 1 to 8% by mass when the total solid content of the composition is 100% by mass.

4. An easily adhering polyester film for use in printing with a water-based flexographic ink according to any one of claims 1 to 3, wherein the crosslinking agent is present in an amount of 0 to 50% by mass as solid content, when the total amount of solid content in the composition is 100% by mass.

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