TWI909034B - Printed materials - Google Patents

Abstract

This invention provides a printed material that avoids static electricity during the printing process and has good adhesion to various ink components. Even when stored in a high-temperature and high-humidity environment after printing, the adhesion between the ink layer and the easy-to-adhere layer will not decrease, thus maintaining good adhesion. The printed material of this invention has an adhesive coating layer on a polyester film substrate, and at least one ink layer is deposited on the adhesive coating layer. The ink layer is selected from UV curing ink, solvent ink, oxidative polymerization ink, heat transfer ink ribbon, and LBP toner. The nitrogen ion concentration A (at%) and nitrogen element ratio B (at%) on the surface of the adhesive coating layer are determined by X-ray photoelectron spectroscopy to satisfy a specific relationship, and the contact angle _θH₂O of the surface of the adhesive coating layer with water is within a specific range.

Description

Printed materials

This invention relates to a printed material with excellent adhesion to various ink layers. More specifically, it relates to a printed material having an adhesive coating on a biaxially oriented polyester film substrate. This adhesive coating is most suitable for all types of ink layers, including UV-curable inks, solvent-based inks, oxidative polymeric inks, heat transfer ink ribbons, and LBP (Laser Beam Printer) toners. In particular, regarding adhesion to active energy-curable ink layers such as UV-curable inks, the adhesion to these ink layers does not decrease when stored in a high-temperature and high-humidity environment after printing.

Polyester film, due to its excellent mechanical, electrical, and dimensional stability properties, is used as a substrate film in many fields, including magnetic recording materials, packaging materials, electrical insulation materials, photosensitive materials, drawing materials, and photographic materials. It is especially indispensable for various commercial printing applications and labels that require printing on the film. However, because polyester film has poor adhesion to printing inks, it is generally necessary to use an anchoring coating made of resin with good adhesion. Examples of resins constituting the aforementioned coating layer include resins made by mixing one or more of polyester resins, polyurethane resins, and acrylic resins, as well as resins made by mixing the aforementioned resins with specific crosslinking agents (melamine, isocyanates, etc.). However, generally speaking, the surface of the polyester film substrate and the surface of the adhesion-enhancing coating layer provided to improve adhesion are prone to becoming charged, sometimes posing problems related to the passability of the film-making process and electrostatic barriers in the processing steps (see, for example, Patent 1).

As a method to improve the problem caused by static electricity, it is known to impart antistatic properties to the coating by including conductive polymers such as polyaniline and polypyrrole in the coating; or conductive fillers such as particulate metal powders such as carbon black, nickel, and copper, metal oxides such as tin oxide and zinc oxide, fibrous metal-cladded fibers such as brass, stainless steel, and aluminum, flake graphite, aluminum flakes, and copper flakes.

Alternatively, it is also known to formulate a polymeric antistatic agent having at least one of a sulfonate group or a phosphate group in its molecule into a coating and apply it to a substrate film (see, for example, Patent 2).

In recent years, printed materials used as labels in various fields have become increasingly widespread. The food market is expanding globally, naturally in developed countries, and food labeling is also becoming increasingly common in developing countries. Furthermore, with the increasing demand for industrial products, the demand for warning labels for industrial electronic components is also rising. These printed materials are often used in high-temperature or high-humidity environments. However, when printed materials are stored in such environments, the adhesion between the ink layer and the substrate decreases, causing peeling of the printed area, which sometimes renders the label ineffective. [Prior Art Documents] [Patent Documents]

[Patent Document 1] Japanese Patent Application Publication No. 2001-348450. [Patent Document 2] Japanese Patent Application Publication No. 2011-156848.

[The problem the invention aims to solve]

The purpose of this invention is to provide a printed material having an adhesive coating layer on a polyester film substrate, upon which an ink layer is further formed. This avoids electrostatic interference during the printing process and provides excellent adhesion to various ink compositions. Even when stored in a high-temperature and high-humidity environment after printing, the adhesion between the ink layer and the adhesive layer does not decrease, thus maintaining good adhesion. [Means for Solving the Problem]

In order to solve the aforementioned problems, the inventor of this case conducted research on the causes of the aforementioned problems, and thus completed this invention. That is, this invention consists of the following components. 1. A printed material having an adhesive coating layer on a polyester film substrate, wherein at least one ink layer is deposited on the adhesive coating layer, the ink layer being selected from UV-curable ink, solvent-based ink, oxidative polymerization ink, thermal transfer ink ribbon, and LBP toner; the nitrogen ion concentration A(at%) and nitrogen element ratio B(at%) of the surface of the adhesive coating layer, determined based on surface elemental distribution measured by X-ray photoelectron spectroscopy, satisfy the following formulas (i) and (ii), and the contact angle _θH₂O of the surface of the adhesive coating layer with water satisfies the following formula (iii). (i) A(at%) > 0.4. (ii) 2.0 ≤ B/A ≤ 5.0. (iii) 50°≦ _θH₂O ≦70°. 2. The printed material as described in section 1 above, wherein the aforementioned adhesive coating is formed by curing a composition comprising a cationic antistatic agent, polyurethane resin, and polyester resin. 3. The printed material as described in section 1 or 2 above, wherein the aforementioned polyester film substrate is a white polyester film substrate containing inorganic particles and/or a thermoplastic resin immiscible with polyester resin. [Invention Benefits]

This invention enables the production of various printed materials that avoid static electricity during the printing process and have good adhesion between the coating layer and the ink layer. Even when stored in a high-temperature and high-humidity environment after printing, the adhesion between the substrate and the ink layer will not decrease, thus maintaining good adhesion.

[Polyester Film Substrate] The polyester resin constituting the polyester film substrate in this invention is, in addition to polyethylene terephthalate, polybutylene terephthalate, polyethylene 2,6-naphthalenedicarboxylate, and polypropylene terephthalate, a copolymer polyester resin obtained by replacing a portion of the diol or dicarboxylic acid component of the aforementioned polyester resin with a copolymer component such as: diethylene glycol, neopentyl glycol, 1,4-cyclohexanediol, polyalkylene glycol, etc.; and dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, 5-sodium isophthalic acid, 2,6-naphthalenedicarboxylic acid, etc.

The polyester resins suitable for use as polyester film substrates in this invention are mainly selected from polyethylene terephthalate, polyethylene terephthalate, polyethylene butylene terephthalate, and polyethylene 2,6-naphthalate. Among these polyester resins, polyethylene terephthalate is the best in terms of balance between physical properties and cost. In addition, 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 toughness.

There are no particular limitations on the catalyst used for polycondensation in the manufacture of polyester resins, but antimony trioxide is a suitable catalyst due to its low cost and excellent catalytic activity. Additionally, germanium or titanium compounds are also preferred. Further preferred polycondensation catalysts include: catalysts containing aluminum and/or aluminum compounds and phenolic compounds; catalysts containing aluminum and/or aluminum compounds and phosphorus compounds; and catalysts containing aluminum salts of phosphorus compounds.

The polyester film used in this invention can be a single-layer structure or a multi-layer structure, but preferably some or all of the layers of the polyester film are opaque. The optical concentration of the polyester film's opacity is 0.3 or higher, preferably 0.3 to 4.0, and most preferably 0.5 to 3.0. If the optical concentration is 0.3 or higher, the printing effect becomes clearer and better when printing is performed on the surface of the obtained polyester film. In addition, if the optical concentration is 4.0 or lower, even better printing effects can be expected.

The method for obtaining the optical concentration within the aforementioned range is not particularly limited, and it can be preferably achieved by including inorganic particles in the polyester resin or by including a thermoplastic resin that is immiscible with the polyester resin. The content of these components is not particularly limited, but in the case of inorganic particles, it is preferably 5% to 35% by mass, and more preferably 8% to 25% by mass, relative to the formed polyester. On the other hand, in the case of containing an immiscible thermoplastic resin, it is preferably 5% to 35% by mass, and more preferably 8% to 28% by mass, relative to the polyester. In addition, when inorganic particles and thermoplastic resins that are immiscible with polyester resins are used together, in terms of film strength, toughness and film stability, it is preferable that the total amount of these components be set to 40% by mass or less relative to polyester-based films.

The polyester film substrate of this invention can be composed of a single layer or a laminated structure, but a preferred embodiment is a laminated structure of X layers/Y layers/X layers, wherein the X layers contain inorganic particles and the Y layers contain micro-cavities. By configuring the layer containing inorganic particles in the X layer, which serves as the surface layer, the slip properties (i.e., operability) and concealment of the film can be improved. By making the Y layer, which serves as the inner layer, contain micro-cavities, the film's cushioning properties can be exhibited and the strength of the film surface can also be ensured. There are no particular limitations on the method of forming the layered structure here, but from the perspective of manufacturing stability and processing costs, co-extrusion is preferable.

The content of inorganic particles in layer X is preferably 2.5% to 70.0% by mass relative to polyester, more preferably 4.0% to 60.0% by mass, and even more preferably 6.0% to 50.0% by mass. The content of immiscible thermoplastic resin in layer Y is preferably 5% to 35% by mass relative to polyester, more preferably 8% to 28% by mass.

In terms of film strength, toughness, and film fabrication stability, the thickness ratio of each layer in the X-layer/Y-layer/X-layer stacked structure is preferably in the range of 0.5/9/0.5 to 2/6/2, and more preferably in the range of 1/8/1 to 1.5/7/1.5.

The inorganic particles used are not particularly limited, but preferably have an average particle size of 0.1 μm to 4.0 μm, and more preferably 0.3 μm to 1.5 μm. Specifically, white pigments such as titanium oxide, barium sulfate, calcium carbonate, and zinc sulfide are preferred, and these components can also be mixed. Furthermore, inorganic particles commonly found in membranes can also be used, such as silicon dioxide, alumina, talc, kaolin, clay, calcium phosphate, mica, lithium bentonite, zirconium oxide, tungsten oxide, lithium fluoride, calcium fluoride, and calcium sulfate.

Furthermore, there are no particular limitations on thermoplastic resins that are immiscible with polyester resins. Examples of thermoplastic resins that can be mixed with polyethylene terephthalate (PET) resin include: polystyrene resin, polyethylene resin, polypropylene resin, polymethylpentene resin and other polyolefin resins, cyclic polyolefin resins, acrylic resins, phenoxy resins, polyphenylene ether resins, polycarbonate resins, etc. These thermoplastic resins can be mixed and modified. Of course, they can also be used in conjunction with the aforementioned inorganic particles. Furthermore, various whitening agents can be added as needed.

Furthermore, the polyester film used in this invention is preferably a polyester film containing microcavities with an apparent density of 0.3 g/ ^cm³ to 1.3 g/ ^cm³ . Additionally, considering both cushioning and surface peel strength, it is also preferable that the aforementioned polyester film has a cavity stacking density of 0.20 cavities/μm or more, more preferably 0.25 cavities/μm or more, and even more preferably 0.30 cavities/μm or more. As a result, the obtained polyester-based coated film exhibits excellent print clarity and processing characteristics during printing. Here, the cavity stacking density (cavities/μm) is defined by the formula: number of cavities in the film thickness direction (cavities) / film thickness (μm). Regarding the cavity performance efficiency, the upper limit of the cavity stack density is preferably 0.80 cavities/μm, and more preferably 0.55 cavities/μm. As a method to adjust the density to the above range, in addition to adjusting the amount or type of immiscible thermoplastic resin added, viscosity, etc., other methods may be used, such as changing the screw shape of the extruder, or installing a static stirrer in the molten resin flow path, but are not limited to these methods.

These polyester films containing microcavities exhibit significantly enhanced opacity due to the light scattering caused at the interface between the microcavities and the polyester substrate. This reduces the need for the addition of inorganic particles, making them particularly useful. Furthermore, the presence of microcavities in the film allows for a lighter substrate, simplifying operation and resulting in significant economic benefits such as reduced raw material and transportation costs.

As a method for obtaining such a polyester film containing microcavities, known methods already disclosed can be used, such as the method of extending a sheet at least along a uniaxial direction to create cavities around the immiscible resin microparticles described later. The aforementioned sheet is formed by mixing a thermoplastic polyester resin as a matrix with a thermoplastic resin that is immiscible with the polyester resin as described above, and dispersing the immiscible resin in the polyester resin in the form of microparticles.

Furthermore, the thickness of the obtained polyester film substrate is preferably from 5 μm to 300 μm. More preferably, the thickness of the polyester film substrate is from 20 μm to 300 μm, and even more preferably from 40 μm to 250 μm.

Whiteness, highly valued in printing materials, can be represented by the color b-value. Regarding the color b-value, a higher value indicates a stronger yellow tint, while a lower value indicates a stronger blue tint. A color b-value that corresponds well to visual confirmation is ideally below 4.0, and even better, below 3.0. With a b-value below 4.0, whiteness is good, resulting in excellent clarity during printing, such as for labels, thus increasing the product's value. The lower limit for the tint b-value is preferably -5.0. With a b-value above -5.0, the blue tint of the film does not become excessively strong, providing a good balance of resolution when used as a printing substrate, making it superior.

[Explanation of the characteristic values in this invention] The adhesive coating in this invention is preferably composed of a cation-based antistatic agent containing nitrogen, polyester resin, or polyurethane resin. Furthermore, by placing cationic antistatic agents and polyurethane resins in appropriate amounts and proportions on the surface of the easily adhesive coating, the contact angle with water is controlled within a suitable range, thereby avoiding static electricity barriers during the printing process. It also exhibits excellent adhesion to various ink components, particularly with UV-cured inks and other active energy line-cured inks. Even when stored in high-temperature and high-humidity environments after printing, the adhesion to these ink layers remains strong and does not decrease.

Here, the amounts of the cationic antistatic agent and polyurethane resin components on the surface of the aforementioned adhesive coating are evaluated using the peak areas of the ionized and unionized nitrogen peaks in the N1s spectrum of X-ray photoelectron spectroscopy (ESCA). In ESCA, the peak positions of the obtained measured spectra are used to identify the corresponding element species and chemical state. Furthermore, curve fitting is performed on the element peaks to calculate the peak areas. The adhesive coating of this invention contains a nitrogen-containing cationic antistatic agent and polyurethane resin. In the case of the easily adhesive coating, the peaks of the N1s spectrum of ESCA are illustrated in Figure 1. The thin solid line in the figure represents the measured data of the N1s spectrum. Of the two peaks, the peak near 402 eV of the curve represented by the dotted line in Figure (1) is the peak of ionized nitrogen, which can be identified in this invention as originating from a cationic antistatic agent. Furthermore, the peak near 400 eV of the curve represented by the dashed line in Figure (2) is the peak of unionized nitrogen, which can be identified in this invention as originating from polyurethane resin. Curve fitting was performed on the peaks of the full-element spectra detected by the N1s spectrum. With the peak area set to 100 (at%), the area ratio of (1) was expressed as the nitrogen element ratio A (at%) of the cationic antistatic agent, and used as an indicator of the amount of the aforementioned antistatic agent component on the surface of the easily bondable coating. Similarly, the area ratio of (2) was expressed as the nitrogen element ratio B (at%) of the polyurethane resin, and used as an indicator of the amount of the aforementioned polyurethane resin component on the surface of the easily bondable coating.

Furthermore, regarding the adhesive coating of this invention, based on the characteristic values determined by surface elemental distribution measurement using ESCA, which are in the following relationships (i) and (ii), and when the contact angle _θH₂O of the adhesive coating surface with water is as shown in equation (iii), static electricity barriers during the printing process are avoided, and it exhibits good adhesion to various ink compositions, especially with active energy line curing ink layers such as ultraviolet (UV) curing inks. Even when stored in a high-temperature and high-humidity environment after printing, the adhesion to the aforementioned ink layers does not decrease and maintains good adhesion. (i) A(at%) > 0.4. (ii) 2.0 ≤ B/A ≤ 5.0. (iii) 50°≦θH ₂ O≦70°.

According to the present invention, a printed material is provided that maintains good adhesion even when stored in a high-temperature and high-humidity environment after printing without causing a decrease in the adhesion between the ink layer and the adhesive coating. The high-temperature and high-humidity environment storage test conditions in the present invention are the temperature and humidity conditions exceeding normal temperature and humidity conditions as defined in JIS-8703, and are assumed to be for use in labels for industrial electronic components or for use in food labels in humid environments such as Southeast Asia, and are set at a temperature of 80°C and a humidity of 90%RH for 3 days. Furthermore, in the adhesion evaluation described later, it is preferable that the residual area of the printed layer before and after storage under the aforementioned storage test conditions is more than 90% of the total area, which will not cause a decrease in adhesion or tightness, and is preferred to maintain a good range of adhesion and tightness.

This paper explains the principle behind the antistatic properties of ionic antistatic agents, including the cationic antistatic agent of this invention, and their relationship with ink adhesion. When using an ionic antistatic agent to achieve antistatic properties on a substrate surface, it is preferable to form a water network on the substrate surface that facilitates the flow of static electricity. By having the ionic antistatic agent present on the substrate surface, it attracts moisture from the air. Therefore, the more ionic antistatic agent present on the substrate surface, the easier it is to attract moisture from the air, and the easier it is to form a water network, thus facilitating the performance of antistatic properties. However, on the other hand, due to the increased amount of ionic antistatic agent on the substrate surface, the relative amount of resin decreases. That is, in this invention, there is a risk of reduced adhesion due to the decreased amount of polyurethane resin, which is generally considered to be related to adhesion to the ink. Therefore, it is preferable to control the amount of ionic antistatic agent and resin (especially polyurethane resin) on the surface of the adhesive coating to a suitable range. In order to form a water network even when the amount of ionic antistatic agent on the surface of the adhesive coating is low, it is preferable to control the contact angle of the adhesive coating surface with water. By controlling the contact angle of the adhesive coating surface to a suitable range, the water attracted by the antistatic agent on the adhesive coating surface can also wet and diffuse into areas where the antistatic agent is absent. In other words, by controlling the contact angle of the adhesive coating surface, it is possible to facilitate the formation of a water network. Therefore, good antistatic properties can be obtained even with a smaller amount of antistatic agent. By achieving the facilitating effect of water network formation, the excessive wetting and diffusion of water is suppressed, thereby achieving an optimal contact state between the ink and the polyurethane resin components of the adhesive coating surface. Furthermore, by controlling the contact angle of the adhesive coating surface to an appropriate range, the affinity with various inks is improved for printed materials, enhancing adhesion and wetting diffusion with inks. Moreover, when stored in high-temperature and high-humidity environments, the degradation of the adhesive coating caused by moisture penetrating the ink layer can be suppressed, thereby maintaining adhesion.

A(at%) is preferably greater than 0.4. By controlling it within the aforementioned range, the coating surface can attract moisture from the air. By controlling the contact angle of the easily adherent coating surface with water to a suitable range, as described later, good antistatic properties can be obtained, and static electricity barriers during the printing process can be avoided. A(at%) is more preferably 0.5at% or more, and even more preferably 0.6at% or more. However, if A(at%) is too large, it becomes difficult to meet the preferred range of B/A below, therefore it is preferably 5at% or less, more preferably 3at% or less, and even more preferably 2at% or less.

The B/A ratio is preferably between 2.0 and 5.0. By controlling the B/A within the aforementioned range and controlling the contact angle of the coating surface with water within a suitable range (described later), both antistatic properties and ink adhesion are considered. Furthermore, for printed materials, this also helps to suppress coating degradation and maintain good adhesion when stored in high-temperature and high-humidity environments. The lower limit of the B/A ratio is preferably 3.0 or higher. On the other hand, the upper limit of the B/A ratio is preferably 4.0 or lower.

The contact angle of the coating surface with water is preferably in the range of 50° to 70°. The lower limit of the contact angle is preferably 60° or higher, while the upper limit is preferably 68° or lower. By controlling it within the range of 50° to 70°, a good auxiliary effect is achieved for the formation of a water network on the coating surface. Furthermore, for printed materials, it improves affinity with various inks, enhances adhesion and wetting diffusion with inks, and, when stored in high-temperature and high-humidity environments, suppresses the deterioration of the adhesive coating caused by moisture penetrating the ink layer, thereby maintaining adhesion.

[Easy-to-Adhere Coating] To balance antistatic properties with adhesion to inks or toners, especially achieving good adhesion to UV-curable inks during high-speed printing, the easy-to-adhere polyester film of this invention preferably has an easy-to-adhere coating composed of a nitrogen-containing cationic antistatic agent, polyester resin, or polyurethane resin on at least one side. The easy-to-adhere coating can be applied to both sides of the polyester film, or it can be applied to only one side of the polyester film, with a different type of resin coating applied to the other side.

The following is a detailed explanation of the components of easily adhesive coatings. [Cationic Antistatic Agents] Examples of cationic antistatic agents include: poly(ethylene imide), poly(diallyl dimethyl ammonium salt), poly(ethylene alkyl polyamine dicyandiamide ammonium condensate), polyvinylpyridine halides, (meth)acrylate alkyl quaternary ammonium salts, (meth)acrylamide alkyl quaternary ammonium salts, ω-chloro-poly(oxyethylene-polymethylene-alkyl quaternary ammonium salt), polyvinylbenzyltrimethyl ammonium salt, polystyrene-based cationic polymers, and poly(methyl)methacrylate... Acrylic cationic polymers (methyl methacrylate, ethyl acrylate, 2-hydroxyethyl methacrylate, trimethylaminoethyl chloromethacrylate, etc.), polyvinylpyridine polymers, cyclic monopolymers, linear monopolymers, polymers of aromatic vinyl monomers having two or more quaternary ammonium groups in the side chain (pendant type), and polymers having pyrrolidine onium rings in the main chain, etc. These polymers can be homopolymers or copolymers. Known monomers capable of copolymerization can be used in the manufacture of these polymers. Regarding the control of the amount of antistatic agent component present on the surface of the easily adhesive coating, an antistatic agent having a linear alkyl group is preferred, and more preferably an antistatic agent having both a linear alkyl group and a quaternary ammonium salt group.

In this invention, the antistatic agent is preferably present on the surface of the adhesive coating.

Therefore, in antistatic agents having a straight-chain alkyl group and a quaternary ammonium salt group, the number of carbon atoms in the alkyl chain is preferably 10 to 20, more preferably 12 to 19, and even more preferably 14 to 18. In order to control the nitrogen ratio of the cation-based antistatic agent containing nitrogen, as determined by surface elemental distribution using ESCA, to a suitable range, it is preferable to allow the aforementioned antistatic agent to penetrate to the surface of the easily adhesive coating. Considering the intermolecular interactions and the ease of penetration determined by the molecular length, the aforementioned range is preferred.

In addition, in the molecular structure of cation-based antistatic agents containing nitrogen, it is permissible to include at least one amide bond or amino ester bond between the linear alkyl chain and the quaternary ammonium salt group.

In the aforementioned antistatic agents, the relative ion of the quaternary ammonium salt group is not particularly limited as long as it is anionic. It can preferably be selected from halogen ions, mono- or poly-halogenated alkyl ions, nitrate ions, sulfate ions, alkyl sulfate ions, sulfonate ions, or alkyl sulfonate ions. Chloride ions, methanesulfonate ions, ethanesulfonate ions, and nitrate ions are preferred.

[Polyester Resin] The polyester resin used in forming the easily adhesive coating layer of this invention can also be linear, but more preferably it is a polyester resin composed of dicarboxylic acids and diols with branched structures. Examples of dicarboxylic acids here include: aliphatic dicarboxylic acids such as adipic acid and sebacic acid, whose main components are terephthalic acid, isophthalic acid, or 2,6-naphthalenedicarboxylic acid; and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid. Furthermore, the term "branched diol" refers to diols with branched alkyl groups, such as: 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, etc.

The dicarboxylic acid that forms a component of the aforementioned polyester resin is preferably terephthalic acid or isophthalic acid. In addition to the aforementioned dicarboxylic acid, to impart water dispersibility to the copolymer polyester resin, it is preferable to copolymerize 5-sulfoisophthalic acid, etc., in a range of 1 mol% to 10 mol%, for example: sulfoterephthalic acid, 5-sulfoisophthalic acid, sodium isophthalate-5-sulfonate, etc. Polyester resins containing dicarboxylic acids with a naphthalene skeleton can also be used; however, to suppress the reduction in adhesion to curing inks, the proportion of the aforementioned dicarboxylic acid with a naphthalene skeleton in the total carboxylic acid composition is preferably 5 mol% or less, or it may be omitted.

As a component of the aforementioned polyester resin, it is permissible for it to contain triols or tricarboxylic acids to a degree that does not impair the properties of the polyester resin.

The aforementioned polyester resins may also contain polar groups other than carboxyl groups. Examples include sulfonic acid metal salts and phosphate groups, and one or more of these polar groups may be present. As a method for introducing sulfonic acid metal salts, the following method may be used: metal salts such as 5-sulfoisophthalic acid, 4-sulfonnaphthalene-2,7-dicarboxylic acid, and 5-[4-sulfophenoxy]isophthalic acid, or metal salts such as 2-sulfo-1,4-butanediol and 2,5-dimethyl-3-sulfo-2,5-hexanediol, etc., containing sulfonic acid metal salts, are used within the range of 10 mol% or less, preferably 7 mol% or less, and even more preferably 5 mol% or less of the total polycarboxylic acid or polyol components. If the content is below 10 mol%, the resin itself has good hydrolysis resistance and the coating has good water resistance.

[Polyurethane Resin] In this invention, it is preferable that the antistatic agent is present on the surface of the easily bondable coating, based on the suitable relationship of the surface elemental distribution measured using ESCA, and the water contact angle of the easily bondable coating surface is within a suitable range. Therefore, it is preferable to primarily control the polarity of the polyurethane resin.

As a method to control the polarity of polyurethane resins, one example is controlling the structure of the polyol component used in the synthesis and polymerization of polyurethane resins. Generally, the polarity of the ester or carbonate backbone tends to be lower than that of the ether backbone. In cases where the nitrogen ratio of the cationic antistatic agent, as determined by surface elemental distribution analysis using ESCA, is not within an appropriate range, the aim is to reduce the interaction between the polyurethane resin and the cationic antistatic agent, thereby ensuring the antistatic agent is present on the surface of the easily adhesive coating. Preferably, this is achieved by using a polyurethane resin whose polyol component used in the synthesis and polymerization of the polyurethane resin has an ester or carbonate backbone. Polyurethane resins with a carbonate backbone are preferred.

Examples of polyols with an ether skeleton include: polyethylene glycol, polypropylene glycol, polybutylene glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol.

Examples of polyols with an ester skeleton include: polycarboxylic acids (malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, sebacic acid, fumaric acid, cis-butenedioic acid, terephthalic acid, isophthalic acid, etc.) or their anhydrides and polyols (ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol). Diols, 2-methyl-2,4-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-hexyl-1,3-propanediol, cyclohexanediol, dihydroxymethylcyclohexane, dimethylbenzene, dihydroxyethoxybenzene, alkyldialkylolamine, lactone diol, etc.

As a polyol with a carbonate backbone, it is preferable to contain aliphatic polycarbonate polyols with excellent heat resistance and hydrolysis resistance. Examples of aliphatic polycarbonate polyols include aliphatic polycarbonate diols and aliphatic polycarbonate triols, and aliphatic polycarbonate diols can be used appropriately. Aliphatic polycarbonate diols used in the synthesis and polymerization of the polyurethane resin with a polycarbonate structure of the present invention can be exemplified by reacting one or more of the following diols, such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,8-nonanediol, neopentanediol, diethylene glycol, and dipropylene glycol, with carbonates such as dimethyl carbonate, ethylene carbonate, and phosgene.

Other methods for controlling the polarity of polyurethane resins include, for example, controlling the number-average molecular weight of the polyols used in the synthesis and polymerization of polyurethane resins. Generally, a higher number-average molecular weight of the polyols used in the synthesis and polymerization of polyurethane resins tends to result in lower polarity, while a lower number-average molecular weight tends to result in higher polarity. In cases where the contact angle between the surface of an easily adhesive coating and water is not within an appropriate range, it is preferable to increase the number-average molecular weight of the polyols to reduce the polarity of the polyurethane resin. Furthermore, in cases where the contact angle of the easily adhesive coating surface with water exceeds a suitable range, it is preferable to reduce the number average molecular weight of the polyol component and increase the polarity of the polyurethane resin. As an example of the number average molecular weight, when the polyol used in the synthesis and polymerization of the polyurethane resin is an ester-based polyol, the number average molecular weight is preferably 1000 to 2400. More preferably, it is 1200 to 2200, and even more preferably, it is 1400 to 2200. Furthermore, when the polyol is a carbonate-based polyol, the number average molecular weight is preferably 500 to 1800. More preferably, it is 600 to 1600, and even more preferably, it is 700 to 1400.

One method for controlling the polarity of polyurethane resins is, for example, controlling the amount of urethane groups in the molecule. Generally, if there are more urethane groups in the molecule, the polarity of the polyurethane resin increases, and the amount of polyurethane resin component present on the surface of the adhesive coating tends to increase. On the other hand, if there are fewer urethane groups in the molecule, the polarity of the polyurethane resin decreases, and the amount of polyurethane resin component present on the surface of the adhesive coating tends to decrease. Therefore, by controlling the amount of carbamate groups in the molecule, the presence of the antistatic agent component and the polyurethane resin component on the surface of the adhesive coating, and consequently the contact angle of the adhesive coating surface with water, will all change. As an example of setting the characteristic values of the surface elemental distribution measured using ESCA and the contact angle of the adhesive coating surface with water within a suitable range, the amount of carbamate groups in the molecule (the number average molecular weight of the isocyanate components used in the synthesis and polymerization of the polyurethane resin / the number average molecular weight of the polyurethane resin) is preferably 26 to 38. More preferably, it is 26 to 36.

As a method for manufacturing the polyurethane resin of the present invention, known methods can be used, such as the following: synthesizing a prepolymer with isocyanate end from a polyol and an excess of polyisocyanate, and then reacting the prepolymer with a chain extender or crosslinker to increase its molecular weight.

The polyisocyanates used in the synthesis and polymerization of the polyurethane resins in this invention include, for example: aromatic aliphatic diisocyanates such as diphenyl diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane; aliphatic diisocyanates such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate; or polyisocyanates formed by pre-addition of these compounds alone or in combination with trimethylolpropane, etc. When using the aforementioned aromatic aliphatic diisocyanates, cycloaliphatic diisocyanates, or aliphatic diisocyanates, it is preferable that there is no yellowing problem. In addition, it is preferable that it will not become an overly tough coating, can alleviate the stress caused by the thermal shrinkage of the polyester film substrate, and does not have problems such as cohesion failure of easily adhesive coatings.

Chain extenders used in the synthesis and polymerization of the polyurethane resins of this invention may include, for example: diols such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, and 1,6-hexanediol; polyols such as glycerol, trimethylolpropane, and pentaerythritol; diamines such as ethylenediamine, hexamethylenediamine, and piperazine; amino alcohols such as monoethanolamine and diethanolamine; thiodiglycol such as dithiodiethylene glycol; or water.

The easily adhesive coating of this invention is preferably applied using an aqueous coating solution via the in-line coating method described later. Therefore, the polyurethane resin of this invention is preferably water-soluble or water-dispersible. Furthermore, the aforementioned "water-soluble or water-dispersible" means dispersible in water or an aqueous solution containing less than 50% by mass of a water-soluble organic solvent.

To impart water dispersibility to polyurethane resins, (copolymerized) sulfonic acid (salt) groups or carboxylic acid (salt) groups can be introduced into the polyurethane molecular backbone. The aforementioned polyurethane resins with the introduction of nonionic groups such as polyoxyalkylene groups are particularly advantageous as they can significantly reduce the interaction between the polyurethane resin and cationic antistatic agents.

The method for introducing the aforementioned nonionic groups can be appropriately selected from known methods, such as: a method of manufacturing by replacing a portion of the polymer polyol with a diol containing polyoxyethylene ethyl; or a method of pre-reacting a portion of the isocyanate groups in the urate body of the diisocyanate with methoxy polyethylene glycol, and then reacting it with the polymer polyol.

To introduce carboxylic acid (salt) groups into the polyurethane resin of this invention, for example, polyol compounds with carboxylic acid groups such as dihydroxymethylpropionic acid and dihydroxymethylbutyric acid are introduced as copolymer components, and neutralized by a salt-forming agent. Specific examples of salt-forming agents include: trialkylamines such as ammonia, 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 salt-forming agents can be used alone or in combination of two or more.

To impart water dispersibility, when using a polyol compound with a carboxylic acid (salt) group as a copolymer component, when the total polyisocyanate content of the polyurethane resin is set to 100 mol%, the mol percentage of the polyol compound with a carboxylic acid (salt) group in the polyurethane resin is preferably 3 mol% to 25 mol%, more preferably 3 mol% to 18 mol%, and even more preferably in the range of 3 mol% to 15 mol%. By controlling it within the aforementioned range, water dispersibility can be ensured, and the interaction with the coexisting cationic antistatic agent component can be suppressed, thereby ensuring that the aforementioned antistatic agent is present on the surface of the easily adhesive coating.

The polyurethane resin in this invention can also be a self-crosslinking polyurethane resin with end-capped isocyanates bonded at the ends to improve strength and toughness.

The polyurethane resin in this invention may also have a branched structure.

In order to form a branched structure in polyurethane resin, the following method can be preferably used: after setting an appropriate temperature and time to allow the aforementioned polycarbonate polyol component, polyisocyanate, and chain extender to react, a compound having a hydroxyl group or isocyanate group with three or more functions is added to carry out the reaction.

Specific examples of compounds having three or more hydroxyl groups include: caprolactone triol, glycerol, trimethylolpropane, glycerol, 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, polyether triol, etc. As for the aforementioned polyether triol, examples include compounds obtained by means of the following method: using one or more compounds having three active hydrogen atoms, such as glycerol, trimethylolpropane, diethyltriamine, etc., as starters, to carry out addition polymerization of one or more monomers such as ethylene oxide, propylene oxide, epoxide, epoxide, pentane, glycidyl ether, methyl glycidyl ether, tributyl glycidyl ether, phenyl glycidyl ether, etc.

Specific examples of compounds having three or more functional isocyanate groups include polyisocyanate compounds having at least three or more isocyanate (NCO) groups in one molecule. In this invention, examples of isocyanate compounds with three or more functional groups include biuret esters, urate esters, and adducts formed by modifying isocyanate monomers such as aromatic diisocyanates, aliphatic diisocyanates, aromatic aliphatic diisocyanates, and alicyclic diisocyanates having two isocyanate groups. Aromatic diisocyanates include, for example, 1,3-phenyl diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenyl diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-toluidine diisocyanate, anisidine diisocyanate, and 4,4'-diphenyl ether diisocyanate. Examples of aliphatic diisocyanates include: trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propanediol diisocyanate, 2,3-butanediol diisocyanate, 1,3-butanediol diisocyanate, dodecamethyl diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate. Examples of aromatic aliphatic diisocyanates include: phenylenedimethyl diisocyanate, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylphenylenedimethyl diisocyanate, and 1,3-tetramethylphenylenedimethyl diisocyanate. Alicyclic diisocyanates include, for example, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (also known as IPDI, isophorone diisocyanate), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and 1,4-bis(isocyanatomethyl)cyclohexane, etc. Biuret compounds refer to self-condensation compounds containing biuret bonds formed by the auto-condensation of isocyanate monomers, such as the biuret compound of hexamethylene diisocyanate. Urate compounds refer to trimers of isocyanate monomers, such as trimers of hexamethylene diisocyanate, isophorone diisocyanate, and toluene diisocyanate. The so-called adduct refers to an isocyanate compound with three or more functions, formed by the reaction of the above-mentioned isocyanate monomer with a compound containing low molecular weight active hydrogen. Examples include: compounds formed by the reaction of trihydroxymethylpropane with hexamethylene diisocyanate, compounds formed by the reaction of trihydroxymethylpropane with toluene diisocyanate, compounds formed by the reaction of trihydroxymethylpropane with phenyl diisocyanate, and compounds formed by the reaction of trihydroxymethylpropane with isophorone diisocyanate.

As a chain extender with three or more functional groups, trihydroxymethylpropane and pentaerythritol, alcohols with three or more hydroxyl groups as described in the above chain extender descriptions, meet the criteria.

[Ratio] In this invention, it is preferable that the antistatic agent is present on the surface of the easily bondable coating, based on the suitable relationship of the characteristic values determined by surface elemental distribution measurement using ESCA, and that the contact angle of the easily bondable coating surface with water is within a suitable range. Therefore, it is preferable to primarily control the polarity of the polyurethane resin, and then adjust the solid component ratio of each component relative to the sum of the cationic antistatic agent, polyester resin, and polyurethane resin solid components to control the polarity of the easily bondable coating.

When the total solid content of the cationic antistatic agent, polyester resin, and polyurethane resin in the coating solution is set to 100% by mass, the content (by mass%) of the cationic antistatic agent is preferably 3.5 to 7.0, more preferably 4.0 to 5.5. By setting it within the aforementioned range, the nitrogen content of the cationic antistatic agent, as determined by surface elemental distribution analysis using ESCA, and the ratio of nitrogen content from polyurethane resin to nitrogen content from the cationic antistatic agent can be controlled within suitable ranges.

When the total solid content of the cationic antistatic agent, polyester resin, and polyurethane resin in the coating solution is set to 100% by mass, the content (by mass%) of polyester resin is preferably 25 to 80%, more preferably 30 to 80%, and even more preferably 35 to 80%. By setting the aforementioned range, the adhesion between the easy-to-adhere coating and the polyester film substrate can be ensured, and the amount of polar carboxyl groups or sulfonic acid metal salt groups and phosphate groups in the polyester resin that can interact with the coexisting cationic antistatic agent components can be controlled. This allows the nitrogen ratio of the cationic antistatic agent, which is derived from nitrogen-containing elements and determined based on the surface elemental distribution measured using ESCA, to be controlled within a suitable range.

When the total solid content of the cationic antistatic agent, polyester resin, and polyurethane resin in the coating solution is set to 100% by mass, the content (by mass%) of polyurethane resin is preferably 15 to 65%, more preferably 20 to 55%. If the content of polyurethane resin is low, the proportion of polyester resin becomes relatively high, and the amount of polar carboxyl groups or sulfonic acid metal salt groups and phosphate groups in the polyester resin of the easily adhesive coating layer increases. If the content of polyurethane resin is high, the polarity of the easily adhesive coating layer becomes low. Due to the increased polyurethane content on the surface of the adhesive coating, and the low polarity of the adhesive coating itself, cationic antistatic agents tend to be present on the surface of the adhesive coating. In other words, the content of cationic antistatic agents on the surface of the adhesive coating also increases. In view of these circumstances, by setting the content (mass %) of polyurethane resin within the aforementioned range, it is possible to control the nitrogen ratio of the nitrogen-containing cationic antistatic agent, as determined by surface elemental distribution analysis using ESCA, and the ratio of nitrogen from polyurethane resin to nitrogen from the cationic antistatic agent, within a suitable range.

[Additives] To the adhesive coating of this invention, known additives may be added, within the scope not hindering the effects of this invention, such as surfactants, antioxidants, heat stabilizers, weather stabilizers, UV absorbers, organic smoothers, pigments, dyes, organic or inorganic particles, nucleating agents, etc.

In order to reduce the gloss of the adhesive coating layer, inert particles can also be included in the adhesive coating layer.

Examples of inert particles mentioned above include: titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silicon dioxide, aluminum oxide, talc, kaolin, clay, calcium phosphate, mica, lithium bentonite, zirconium oxide, tungsten oxide, lithium fluoride, calcium fluoride, and other inorganic particles; as well as organic polymer particles such as polystyrene-based, polyacrylic acid-based, melamine-based, benzoguanamine-based, and silicone resins. These inert particles can be one type or two or more types combined.

The average particle size of the aforementioned inert particles is preferably between 0.1 μm and 2.4 μm, and more preferably between 0.3 μm and 2.0 μm. If the average particle size of the inert particles is greater than 0.1 μm, the gloss of the film surface will not become excessively high, which is preferable. Conversely, if it is less than 2.4 μm, the particles are less likely to self-adhesively detach from the coating, thus preventing powder shedding, which is also preferable.

Regarding the content of the aforementioned inert particles, they can be added within a range that does not hinder the effect of the present invention. In order to avoid the particles from peeling off from the easily adhesive coating and causing powdering, the content of the particles relative to the total solid component of the easily adhesive coating, based on the solid component of the particles, is preferably 0% to 70.0% by mass, more preferably 0% to 60.0% by mass, and even more preferably 0% to 55.0% by mass.

The shape of the particles is not particularly limited as long as the purpose of this invention is met; spherical particles or amorphous non-spherical particles can be used. The particle size of amorphous particles can be calculated using the equivalent diameter of a circle.

To increase the gloss of the easy-adhesive coating layer, it is best if the easy-adhesive coating layer does not contain particles.

[Method for Manufacturing Polyester Film] The method for manufacturing the polyester film in this invention is arbitrary and not particularly limited. For example, it can be manufactured in the following manner.

After the membrane raw material is thoroughly vacuum dried, it is melted using an extruder. While applying static electricity to the rotating cooling metal roller, it is extruded in sheet form from a T-die to obtain an unstretched membrane.

In terms of uniform mixing, the white pigment or other additives are not added as powder and mixed in the extruder. Instead, they are mixed by pre-preparing masterbatch polymers containing high concentrations of white pigments, etc., in the polyester resin, and then diluting these masterbatch polymers with the polyester resin. To ensure more thorough and uniform mixing of the various film raw materials, a twin-shaft extruder is preferred. Furthermore, to improve electrostatic adhesion during polyester polymerization, it is preferable to pre-add alkaline earth metal salts and/or alkaline metal salts and phosphoric acid or phosphates. The addition of phosphoric acid or phosphates also has the effect of improving tint (especially b-value).

In this invention, the polyester film of the substrate can be a single-layer structure or a laminated structure. In the case of a laminated structure, it has the advantage that the composition of the surface layer and the core layer can be designed in various ways according to the required function. When the polyester film of the substrate is set as a laminated structure, it is preferable to adopt the following co-extrusion method: the resins of layer X and layer Y are supplied to different extruders, for example, to form a two-layer structure of layer X/layer Y in a molten state, and then laminated into a three-layer structure of layer X/layer Y/layer X, etc., and extruded from the same die.

The unstretched film thus obtained is then subjected to biaxial alignment treatment by stretching in the following ways: stretching between rollers with a speed difference (roller stretching), stretching by holding with a clamp to gradually expand (stenter stretching), stretching by using air pressure to expand (blown stretching), etc.

The conditions for stretching and aligning an unstretched film are closely related to the film's physical properties. The following example, the most common stepwise biaxial stretching method (especially the method of stretching an unstretched sheet along its length and then along its width), will be used to illustrate the stretching and alignment conditions.

First, in the first stage of the longitudinal stretching process, stretching is performed between two or more rollers with different circumferential speeds. The heating method at this stage can be a heated roller method, a non-contact heating method, or a combination of these methods. Next, the uniaxially stretched film is introduced into a tenter frame and stretched 2.5 to 5 times its original length along the width at a temperature below the polyester's melting point Tm - 10°C.

The biaxially stretched film thus obtained may be subjected to heat treatment as needed. Heat treatment is preferably carried out in a tenter frame, and preferably at a heat treatment temperature in the range of the polyester melting point (Tm) - 50 (°C) to Tm (°C).

[Manufacturing Method of PET (Polyethylene Terephthalate) with Cavities] In this invention, the polyester film substrate can also have a thermoplastic resin immiscible with the polyester resin dispersed in the polyester resin during the steps of melting and extruding the film raw material. The polyester film substrate in this invention is preferably a white polyester film substrate. In the experimental examples of this invention, the polyester resin and the thermoplastic resin immiscible with the polyester resin are supplied in granular form, but this is not a limitation.

The raw materials used for melt-forming into a film and fed into the extruder are prepared by granulating these resins according to the target composition. For the polyester film substrate of this invention, as a suitable method to prevent segregation, one example is to combine part or all of the raw material resins in advance and then mix and granulate them to produce masterbatch granules. This method is used in the experimental examples of this invention, but there is no particular limitation as long as it does not impair the effect of this invention.

Furthermore, when extruding these immiscible resin mixtures, the mixture is mixed in a molten state to achieve micro-dispersion. This process, aimed at reducing the interfacial energy of the resins, results in a tendency to re-aggregate. This is because when extruding an unstretched film, the coarse dispersion of the cavity surface agent hinders the desired physical properties.

To prevent the aforementioned issues, when forming the membrane in this invention, it is preferable to use a biaxial extruder with a higher mixing efficiency to pre-disperse the cavity surface agent. Alternatively, in cases where the above methods are difficult, as an auxiliary method, it is also preferable to feed the raw resin from the extruder to the feed block or die via a static mixer. The static mixer used here can be a static mixer or an orifice. However, when using these methods, it is preferable to prevent heat-degraded resin from remaining in the melt flow.

Furthermore, in the low-shear molten state of polyester resins, immiscible thermoplastic resins temporarily dispersed in microparticles tend to re-aggregate over time. Therefore, the fundamental solution is to reduce the residence time in the melt line from the extruder to the die. In this invention, the residence time in the melt line is preferably set to 30 minutes or less, and more preferably 15 minutes or less.

The conditions for stretching and aligning the unstretched membrane obtained in the above manner are closely related to the membrane's physical properties. Hereinafter, the most common stepwise biaxial stretching method (especially the method of stretching the unstretched membrane along the length direction and then along the width direction) will be used as an example to illustrate the stretching and alignment conditions.

In the longitudinal stretching step, a uniaxially stretched film is obtained by stretching the film 2.5 to 5.0 times its length using rollers heated to 80°C to 120°C. The heating method can be a heated roller, a non-contact heating method, or a combination of these methods. The uniaxially stretched film is then fed into a tenter frame and stretched 2.5 to 5 times its length along the width at a temperature below (Tm - 10°C). Here, Tm refers to the melting point of the polyester.

In addition, the biaxially stretched film may be subjected to heat treatment as needed. Heat treatment is preferably carried out in a tenter frame, preferably within the range of (Tm-60°C) to Tm.

[Preparation when using recycled polyester raw materials] The polyester resins of this invention may also include polyester resins recycled from PET bottles. For polyesters used in PET bottles, crystallinity must be controlled to ensure good bottle formability and appearance. As a result, sometimes polyesters containing ester units derived from isophthalic acid and any diol, represented by ethylene glycol or diethylene glycol, at a concentration of 0.5 mol% to 10.0 mol% relative to all ester constituent units in the polyester resin are used. Additionally, polyesters that have undergone liquid-phase polymerization followed by solid-phase polymerization, thereby increasing their ultimate viscosity, are sometimes used. Polyester resin granules recycled from PET bottles are typically produced by washing and crushing PET bottles, heating and melting them, and then granulating them. Alternatively, polyester resin granules that have undergone solid-state polymerization to increase their ultimate viscosity can also be used. The ultimate viscosity of the polyester resin recycled from PET bottles is preferably in the range of 0.60 dl/g to 0.75 dl/g. If the ultimate viscosity is above 0.60 dl/g, the resulting membrane is less prone to breakage, making membrane manufacturing easier and more stable. Conversely, if the ultimate viscosity is below 0.75 dl/g, the filtration pressure increase of the melt fluid will not become excessive, making membrane manufacturing easier and more stable. Generally, when polyethylene terephthalate (PET) resin is polymerized in the solid phase, the amount of oligomers, especially the most abundant PET cyclic trimers, is less than that of polymers produced by liquid-phase polymerization. The upper limit of cyclic trimer oligomers in recycled polyester resins made from PET bottles is preferably 0.7% by mass, more preferably 0.5% by mass, and even more preferably 0.4% by mass.

The lower limit of the content of recycled polyester resin from PET bottles in the cavity-containing polyester membrane is preferably 25% by mass, more preferably 30% by mass, and further preferably 50% by mass. If it is 25% by mass or higher, the oligomer content in the cavity-containing polyester membrane is reduced, which can suppress the precipitation of oligomers, and is therefore better. Furthermore, in terms of effectively utilizing recycled resin, a higher content is better in terms of contributing to the reduction of environmental impact. The upper limit of the content of recycled polyester resin from PET bottles is preferably 90% by mass, and more preferably 85% by mass.

The easy-adhesion coating can be applied after or during the film manufacturing process. In particular, for the sake of productivity, it is preferable to apply the coating liquid at any stage of the film manufacturing process, that is, to form the easy-adhesion coating on at least one side of the PET film after it has been unstretched or uniaxially stretched.

The method for applying the coating liquid to the PET film can be any known method. Examples include: reverse roller coating, gravure coating, touch coating, mold coating, roller brush coating, spray coating, air knife coating, wire rod coating, pipe doctor method, impregnation coating, and curtain coating. These methods can be applied individually or in combination.

Regarding the drying conditions after coating, in order to allow the cationic antistatic agent to penetrate to the surface of the easily adhesive coating, and based on the suitable relationship of the characteristic values determined by surface elemental distribution measurement using ESCA, the preferred temperature is 80°C to 150°C, and more preferably 90°C to 140°C. A range of 100°C to 130°C is particularly preferred. However, by extending the drying time, even at relatively lower temperatures, the cationic antistatic agent can penetrate to the surface of the easily adhesive coating, and sometimes the suitable relationship is met based on the surface elemental distribution measurement using ESCA, therefore, the above conditions are not limited.

In this invention, the thickness of the adhesive coating is preferably in the range of 50 nm to 900 nm, more preferably in the range of 70 nm to 800 nm, further preferably in the range of 100 nm to 600 nm, and even more preferably in the range of 200 nm to 500 nm. By increasing the thickness of the adhesive coating, the amount of cationic antistatic agent component per unit volume of the adhesive coating increases. That is, by allowing these cationic antistatic agent components to penetrate to the surface of the adhesive coating, a greater amount of cationic antistatic agent component exists on the surface of the adhesive coating. On the other hand, by reducing the thickness of the adhesive coating, the amount of cationic antistatic agent per unit volume of the adhesive coating is reduced. That is, the amount of cationic antistatic agent present on the surface of the adhesive coating is also reduced. Therefore, by controlling the thickness of the adhesive coating within the aforementioned range, the nitrogen element ratio derived from cationic antistatic agents and the nitrogen element ratio derived from polyurethane resin/nitrogen element ratio derived from cationic antistatic agents in the surface elemental distribution measurement performed using ESCA can be controlled within a suitable range.

[UV-Curing Ink] The UV-curing ink referred to in this invention is a general term for inks that are cured by ultraviolet light. In terms of composition, it comprises pigments (dyes), oligomers and monomers, photopolymerization initiators and accelerators, and excipients. The oligomers and monomers act as flow components in this composition, spreading and adhering to the substrate, and are cured by free radicals generated from the photopolymerization initiator under ultraviolet light. The proportions of the types of oligomers and monomers vary depending on the printing method described later. Generally speaking, it is preferable to have no solvent except for viscosity adjustment purposes, or if present, at most about 10% by mass.

[Solvent-Based Ink] The solvent-based ink referred to in this invention is a general term for inks that harden through evaporation drying. In terms of composition, it includes pigments (dyes), resin components, diluents, and additives. The solvent rapidly evaporates after printing, thereby leaving and fixing the resin or pigment components on the printed surface. The drying speed is extremely fast, making it suitable for high-speed, high-volume printing.

[Oxidative Polymerization Ink] The oxidative polymerization ink of this invention uses a drying oil that exhibits polymerization/curing properties through the absorption of oxygen in the air as its main component. It also includes pigments (dyes), polymerization accelerators, and auxiliary agents. The drying oil acts as a flow component, and its viscosity is adjusted according to the printing method. Recently, composite inks containing both UV-curing components and drying oils have also been developed. Furthermore, the solvents described above primarily refer to organic solvents, including hydrocarbons such as hexane and heptane; esters such as methyl acetate and ethyl acetate; and ketones such as acetone and MEK (methyl ethyl ketone). Examples include these organic solvents alone, mixtures of these organic solvents, and mixtures with alcohols. Monomers or oligomers with polymerizable/curing properties, and oil content not contained in organic solvents. Printing methods using these components include flexographic printing, screen printing, and offset printing. The viscosity of the ink increases with each subsequent step.

[Heat Transfer Ink] The heat transfer ink described in this invention is a heat-melting pigment ink used in a heat transfer printing method that melts ink applied to an ink ribbon and transfers it to paper. In terms of composition, it comprises colorants such as pigments and dyes; binders such as waxes and thermoplastic resins; and various additives such as softeners and dispersants. Resin-based or wax-based inks can be used for heat transfer printing. Resin-based inks are more suitable due to their superior weather resistance. They are used for black and white document output in word processors, tape writers, barcode printers, etc. Additionally, by using colored ribbons, they are also used in color printers and image printers.

[LBP Toner] The LBP toner mentioned in this invention is a coloring powder used in laser printers or photocopiers, formulated with electrostatically conductive microparticles (polymer resin), wax, and pigments. In color printing, four colors are used: blue-green, magenta, yellow, and black. LBP refers to a page-type printer that uses laser light to electrify the drum, utilizing electrostatic charge to adhere the toner.

The evaluation method used in this invention will be explained below. (1) Determination of the ratio of nitrogen (N and N ⁺ ) in the surface region: The surface composition was determined using ESCA. The apparatus used was K-Alpha ⁺ (manufactured by Thermo Fisher Scientific). Details of the measurement conditions are shown below. Furthermore, the Shirley method was used to remove the background during analysis. In addition, the surface composition ratio was set as the average of the measurement results of three or more sites. N (ionized nitrogen such as N ⁺ ) and N (unionized nitrogen such as CN) were calculated by peak separation of the N1s spectrum. Here, N (ionized nitrogen such as N ⁺ ) is the peak near 402 eV in the N1s spectrum, and N (unionized nitrogen such as CN) is the peak near 400 eV. • Measurement conditions: Excitation X-rays: Monochromatic Al Kα radiation; X-ray output: 12kV, 6mA; Photoelectron extraction angle: 90°; Spot size: 400μmφ; Passing energy: 50eV; Step size: 0.1eV. Figure 1 is a graph showing the analysis results of the N1s spectrum of the surface region in the substrate with an easily adhesive coating in Experimental Example 1. The thin solid line represents the measured data of the N1s spectrum. The peaks of the obtained measured spectrum were separated into multiple peaks, and the type of bond corresponding to each peak was identified according to the position and shape of each peak. Furthermore, curve fitting was performed using the peaks from each type of bond to calculate the peak area. The peak area of N (ionized nitrogen elements such as N ⁺ ) is set as A (at%), and the peak area of N (unionized nitrogen elements such as CN) is set as B (at%).

(2) Measurement of Water Contact Angle After placing the substrate with the easily adhesive coating at 23°C and 65%RH for 24 hours, the contact angle between the coating surface and water was measured using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., CA-X) under the same conditions and with distilled water. Ten measurements were taken, and the average value of these measurements was recorded as the contact angle data.

(3) Surface resistivity of the easily adhesive coating: After placing the substrate with the easily adhesive coating in an atmosphere of 23°C and 65%RH for 24 hours, the surface resistivity (Ω/□) of the film surface (in the case of a coating) is measured using a surface resistivity measuring device (manufactured by Mitsubishi Petrochemical Corporation, Hiresta-IP) with a voltage of 500V applied. Cases with less than 1×10 ¹² Ω/□ are considered particularly good: ◎; Cases with 1×10 ¹² Ω/□ or more but less than 1×10 ¹³ Ω/□ are considered good: ○; Cases with 1×10 ¹³ Ω/□ or more are considered: ×.

(4) Initial Adhesion After the printing material described in the experimental examples below was manufactured, Nichiban celluloid tape (CT405AP-24) was cut into pieces 24 mm wide and 50 mm long. Using a hand-held rubber roller to prevent air from entering between the ink layer of the printed material and the tape, complete adhesion was achieved. Then, the celluloid tape was peeled off vertically, and the area of residual printed layer in a 24 mm × 50 mm area was observed and judged according to the following criteria. In this invention, a score of 4 or higher is considered acceptable. 5: The residual area of the printed layer is 99% or more of the total area. 4: The residual area of the printed layer is 90% or more but less than 99% of the total area. 3: The residual area of the printed layer is 80% or more but less than 90% of the total area. 2: The residual area of the printed layer is 70% or more but less than 80% of the total area. 1: The residual area of the printed layer is 60% or more but less than 70% of the total area.

(5) Adhesion after high-temperature and high-environment storage After the printing materials described in the experimental examples below were manufactured, the temperature and humidity test tank [Model: LH44-12P manufactured by NAGANO SCIENCE Co., Ltd.] was set to a temperature of 80°C and a humidity of 90%, and the printing materials were stored under the aforementioned temperature and humidity conditions for 3 days. After storage, the printing materials were removed and allowed to stand until they reached room temperature. After standing, Nichiban celluloid tape (CT405AP-24) was cut into pieces 24mm wide and 50mm long, and the tape was completely adhered by using a hand-held rubber roller to prevent air from mixing into the ink layer of the printing materials. Then, vertically peel off the celluloid tape and observe the area of the printed layer residue in a 24mm × 50mm area, judging according to the following criteria. In this invention, 4 or higher is considered acceptable. 5: The area of the printed layer residue is 99% or more of the total area. 4: The area of the printed layer residue is 90% or more but less than 99% of the total area. 3: The area of the printed layer residue is 80% or more but less than 90% of the total area. 2: The area of the printed layer residue is 70% or more but less than 80% of the total area. 1: The area of the printed layer residue is 60% or more but less than 70% of the total area.

(7) Apparent Density: The film was cut into four 5.00 cm square pieces as samples. The four samples were overlapped, and the thickness was measured at 10 points with a micrometer to four significant figures. The average thickness of the overlapped thickness was calculated. This average value was divided by 4, and the fourth decimal place was rounded to the nearest whole number to obtain the average film thickness (t: μm) of each sample. The mass (w: g) of the four samples was measured to four significant figures using an automatic balance, and the apparent density was calculated using the following formula: Apparent density (g/ ^cm³ ) = w × ^10⁴ / (5.00 × 5.00 × t × 4)

(8) Resin Solids Thickness of Adhesive Coatings The resin solids thickness is calculated based on the amount of coating applied and the total mass of resin solids contained in the coating.

(9) b-value According to JIS-8722, the b-value of the reflected color is measured using a colorimeter (manufactured by Nippon Denshoku Kogyo Co., Ltd., ZE6000). [Example]

Secondly, experimental examples are used to illustrate the invention in detail, but the invention is not limited to the following experimental examples.

[Synthesis of a Nitrogen-Containing Cationic Antistatic Agent: A-1] An esterification reaction was carried out at 100°C for 10 hours using 89 g of dimethylaminoethanol and 285 g of stearic acid with 18 carbon atoms under a nitrogen atmosphere. Tetrahydrofuran was added as a quaternary solvent. A measured amount of dimethylsulfuric acid was added to the target amine, and 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 concentration to the desired level, yielding an isopropanol solution A-1 of a quaternary ammonium salt cationic antistatic agent.

[Synthesis of a Nitrogen-Containing Cationic Antistatic Agent A-2] Using 116 g of N,N-dimethyl-1,3-propanediamine and 285 g of stearic acid, the same treatment as described in A-1 was performed to obtain an isopropanol solution A-2 of a quaternary ammonium salt cationic antistatic agent.

[Polymerization of Polyester Resin B-1] In a stainless steel high-pressure reactor equipped with a mixer, thermometer, and partial reflux condenser, 194.2 parts by weight of dimethyl terephthalate, 184.5 parts by weight of dimethyl isophthalate, 14.8 parts by weight of sodium dimethyl isophthalate-5-sulfonate, 233.5 parts by weight of diethylene glycol, 136.6 parts by weight of ethylene glycol, and 0.2 parts by weight of tetrabutyl titanate were added. The 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, and the reaction system was slowly depressurized. The reaction was carried out at a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain a copolyester resin (B-1). The obtained copolyester resin (B-1) was pale yellow and transparent. The reducing viscosity of the copolyester resin (B-1) was measured to be 0.70 dl/g. The glass transition temperature obtained using DSC (Differential Scanning Calorimetry) was 40°C.

[Preparation of Polyester Aqueous Dispersion Bw-1] In a reactor equipped with a stirrer, thermometer, and reflux device, 25 parts by weight of polyester resin (B-1) and 10 parts by weight of ethylene glycol n-butyl ether were added. The mixture was heated and stirred at 110°C to dissolve the resin. After the resin was completely dissolved, 65 parts by weight of water were slowly added to the polyester solution while stirring. After addition, the solution was cooled to room temperature while stirring, resulting in a milky white polyester aqueous dispersion (Bw-1) with a solid content of 30.0% by weight.

[Preparation of Polyester Resin Solution Bw-2] 97 parts by mass of dimethyl terephthalate, 93 parts by mass of dimethyl isophthalate, 68 parts by mass of ethylene glycol, 116 parts by mass of diethylene glycol, 0.1 parts by mass of zinc acetate, and 0.1 parts by mass of antimony trioxide were added to a reaction vessel, and a transesterification reaction was carried out at 180°C for 3 hours. Next, 7.1 parts by mass of sodium isophthalate-5-sulfonate were added, and an esterification reaction was carried out at 240°C for 1 hour. Then, a polycondensation reaction was carried out at 250°C under reduced pressure (1.33 kPa to 0.027 kPa) for 2 hours to obtain a polyester resin with a molecular weight of 22,000. A viscous melt was obtained by stirring 300 parts by weight of the polyester resin and 140 parts by weight of butyl celluloid at 160°C for 3 hours. Water was then slowly added to the melt, and after 1 hour, a homogeneous, pale white polyester resin solution (Bw-2) with a solid content of 25.0% by weight was prepared.

[Preparation of polyurethane resin solution C-1 with polycarbonate structure] In a four-necked flask equipped with a stirrer, a Deutsche condenser, a nitrogen inlet tube, a silicone drying tube, and a thermometer, add 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 glycol with a number average molecular weight of 2100, 5 parts by mass of neopentyl glycol, and 84.00 parts by mass of acetone as solvent. Stir at 75°C for 3 hours under a nitrogen atmosphere to confirm that the reaction solution has reached the predetermined amine equivalent. Then, lower the temperature of the reaction solution to 50°C and add 3 parts by mass of methyl ethyl ketone oxime dropwise. The reaction solution was cooled to 40°C to obtain a polyurethane prepolymer solution. Next, 450g of water was added to a reaction vessel equipped with a high-speed homogenizer, and the temperature was adjusted to 25°C. While stirring and mixing for 2000 ^min⁻¹ , the polyurethane prepolymer solution was added to disperse the solution in water. Then, acetone and a portion of the water were removed under reduced pressure to prepare a water-dispersible polyurethane resin solution (C-1) with a solid content of 35.4% by mass.

[Preparation of Polyurethane Resin Solution C-2 with Polycarbonate Structure] In a four-necked flask equipped with a stirrer, a Deutsche condenser, a nitrogen inlet tube, a silicone drying tube, and a thermometer, 31.0 parts by mass of hydrogenated isophthalic diisocyanate, 7.0 parts by mass of dihydroxymethylpropionic acid, 60 parts by mass of polyhexamethylene carbonate diol with a number average molecular weight of 1800, 6 parts by mass of neopentyl glycol, and 84.00 parts by mass of acetone as solvent were added. The mixture was stirred at 75°C for 3 hours under a nitrogen atmosphere to confirm that the reaction solution reached the predetermined amine equivalent. After cooling the reaction solution to 40°C, 6.65 parts by mass of triethylamine were added to obtain a polyurethane prepolymer solution. Next, 450g of water was added to a reaction vessel equipped with a homogenizer capable of high-speed stirring, and the temperature was adjusted to 25°C. While stirring and mixing for 2000 ^min⁻¹ , a polyurethane prepolymer solution was added to disperse the water. Then, acetone and a portion of the water were removed under reduced pressure to prepare a water-dispersible polyurethane resin solution (C-2) with a solid content of 35.0% by mass.

[Preparation of polyurethane resin solution C-3 with polyester structure] In a four-necked flask equipped with a stirrer, a Deutsche condenser, a nitrogen inlet tube, a silicone drying tube, and a thermometer, add 82.8 parts by mass of hydrogenated isophthalic diisocyanate, 25.0 parts by mass of dihydroxymethylpropionic acid, 2 parts by mass of 3-methyl-1,5-pentanediol, 150.0 parts by mass of polyester diol composed of terephthalic acid/isophthalic acid//ethylene glycol/diethylene glycol = 50/50//40/60 (molar ratio), and 110 parts by mass of acetone as solvent. Stir at 75°C for 3 hours under a nitrogen atmosphere to confirm that the reaction solution reaches the predetermined amine equivalent. Next, the reaction solution was cooled to 40°C, and 19.8 parts by weight of triethylamine were added to obtain a polyurethane polymer solution. Then, 880 g of water was added to a reaction vessel equipped with a homogenizer capable of high-speed stirring, and the temperature was adjusted to 25°C. While stirring and mixing for 2000 ^min⁻¹ , the polyurethane polymer solution was added to disperse the solution in water. Then, acetone, used as a solvent, was removed under reduced pressure. The concentration was adjusted using water to prepare a polyurethane resin solution (C-3) with a solid content of 30.0% by weight.

[Preparation of an Aqueous Dispersion of Polyurethane-Terminated Isocyanate with a Polyester Structure (C-4)] 33.6 parts by weight of hexamethylene diisocyanate were added to 200 parts by weight of a 2-molar adduct of bisphenol A and a polyester of maleic acid (molecular weight 2000), and the reaction was carried out at 100°C for 2 hours. Then, the system temperature was temporarily lowered to 50°C, and 73 parts by weight of a 30% sodium bisulfite aqueous solution were added. After stirring at 45°C for 60 minutes, the mixture was diluted with 718 parts by weight of water to obtain an aqueous dispersion of terminal polyisocyanate (C-4) with a solid content of 20.0% by weight. The functional group number of this terminal isocyanate crosslinker is 2, and the NCO equivalent is 1300.

[Experimental Example 1] (1) Preparation of Coating Solution The following coating agent was mixed in a mixed solvent of water and isopropanol, and the solid content mass ratio of the nitrogen-containing cationic antistatic agent/polyester resin/polyurethane resin solution was adjusted to 5.0/57.0/38.0. During the white easily adhesive film manufacturing process described later, the coating was applied with a resin solid content thickness of 450 nm. Nitrogen-containing cationic antistatic agent solution (A-1): 2.52 parts by mass (Solid concentration 17.50% by mass) Polyester aqueous dispersion (Bw-1): 17.00 parts by mass Polyurethane resin solution (C-1): 9.60 parts by mass Particles: 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid concentration 40.00% by mass) Surfactant: 0.15 parts by mass (Silicone-based, solid concentration 10% by mass)

(2) Preparation of Master Particle M1 60% by mass of polymethylpentene resin (manufactured by Mitsui Chemicals, DX820) with a melt viscosity (ηO) of 1,300 poise, 20% by mass of polystyrene resin (manufactured by Nippon Polystyrene, G797N) with a melt viscosity (ηS) of 3,900 poise, and 20% by mass of polypropylene resin (manufactured by Grand Polymers, J104WC) with a melt viscosity of 2,000 poise were mixed. The resulting particles were fed to a vented twin-shaft extruder with a temperature of 285°C for premixing. The molten resin is continuously fed into an exhaust-type single-shaft mixer for mixing and extrusion. The resulting strands are cooled and cut to prepare cavity expression agent masterbatch granules (M1).

(3) Preparation of Masterbatch M2 Furthermore, 50% by mass of anthracite-type titanium dioxide particles (manufactured by Fuji Titanium Co., Ltd., TA-300) with an average particle size of 0.3 μm were mixed with 50% by mass of polyethylene terephthalate resin (with an intrinsic viscosity of 0.62 dl/g based on an antimony catalyst, produced using a known method). The resulting mixture was fed to an exhaust-type biaxial extruder for premixing. The molten resin was continuously fed to an exhaust-type uniaxial mixer for mixing and extrusion. The resulting strands were cooled and cut to prepare titanium dioxide-containing masterbatch (M2).

(4) Manufacturing of white, easily adhesive polyester film

[Preparation of Membrane Raw Material D1] 81% by weight of the aforementioned polyethylene terephthalate resin with an intrinsic viscosity of 0.62 dl/g, vacuum-dried at 140°C for 8 hours, 9% by weight of the aforementioned masterbatch (M1) vacuum-dried at 90°C for 4 hours, and 10% by weight of the aforementioned masterbatch (M2) were mixed to prepare membrane raw material (D1).

[Preparation of Unstretched Membrane] The aforementioned membrane raw material (D1) is fed to a Y-layer extruder with a temperature setting of 285°C. A mixture of 70% by weight of polyethylene terephthalate resin (which has the same composition as the membrane raw material (D1)) and 30% by weight of the aforementioned masterbatch (M2) is fed to an X-layer extruder with a temperature setting of 290°C. Molten resin extruded from layer Y by an extruder is introduced into the feed block through orifices. Separately, resin extruded from layer A by an extruder is introduced into the feed block through a static agitator. The layer (layer Y) composed of the membrane raw material (D1) and the layer (layer X) composed of polyethylene terephthalate resin and masterbatch (M2) are layered in the order X layer/Y layer/X layer.

The molten resin was co-extruded in sheet form from a T-die onto a cooling roller at a temperature of 25°C, and then solidified using electrostatic deposition to produce an unstretched film with a thickness of 510 μm. Furthermore, the ejection rates of each extruder were adjusted to achieve a layer thickness ratio of 1:8:1. The molten resin remained at the melt line for approximately 12 minutes, and the shear rate from the T-die was approximately 150 shears per second.

[Fabrication of Biaxially Stretched Film] Using heating rollers, the obtained unstretched film is uniformly heated to 65°C and stretched 3.4 times between two pairs of rollers with different circumferential speeds (low-speed roller: 2 m/min, high-speed roller: 6.8 m/min). At this time, as an auxiliary heating device for the film, an infrared heater (rated output: 20 W/cm) with a gold reflective film in the middle of the rollers is positioned 1 cm away from the film surface, facing both sides of the film. The aforementioned coating solution is then applied to one side of the thus obtained uniaxially stretched film using a reverse light-touch coating method. After coating, the film is fed into a tenter frame, where it is simultaneously dried and heated to 150°C, then stretched 3.7 times its original length. The width is then fixed, followed by a 5-second heat treatment at 220°C, and finally a 4% temperature reduction along the width at 200°C. This process yields a 50μm thick, white, easily bondable polyester film. The b-value of this film is 1.6.

(5) Printing of the Printed Material [Printed Material with Solvent-Based Ink Layer] On the easy-adhesive coating layer of the easy-adhesive polyester film, using "TETRON Standard Solvent" (trade name: TETRON Standard Solvent) manufactured by Jujo Chemical Co., Ltd., "TETRON Screen Ink 900-1 Series 990 Black" was diluted to a TETRON ink: TETRON Standard Solvent ratio of 4:1. A 250-mesh screen was used, and the ink was applied using a squeegee. After ink application, the material was dried and cured for 5 minutes at 90°C using a Yamato Scientific DVS602 drying oven to obtain the printed material.

[Printed Material with Oxidative Polymer Ink Layer] Printed material is obtained by printing on an easy-adhesive coating layer of an easy-adhesive polyester film using oxidative polymeric offset ink [manufactured by Toyo Ink Manufacturing Co., Ltd., trade name "TSP400 G ink"] and a printing press [manufactured by Mei Seisakusho Co., Ltd., trade name "RI Tester"].

[Printed Material with Melt-Type Heat Transfer Ink Layer] On an easy-adhesive coating layer of easy-adhesive polyester film, a SATO Scantronics CL4NX-J heat transfer printer is used to print arbitrary JAN-based 1D barcodes using RICOH heat transfer ribbon B110C ink at a printing speed of 6 inches per second, obtaining the printed material.

[Printed Material with LBP Toner Layer] Using the FUJI XEROX Co., Ltd. ApeosPort-V C3376, any pattern can be printed onto the easy-adhesive coating layer of the easy-adhesive polyester film to obtain a printed material.

[Printed Material with UV-Curing Ink Layer] Printing was performed on an easy-adhesive coating layer of an easy-adhesive polyester film using UV-curable ink [manufactured by T&K TOKA Co., Ltd., trade name "BEST CURE UV161 Blue S"], using a central impression printing press. Ink was metered using an anilox roller with a unit volume of 11 ^cm³ / ^m² , transferred to a solid plate, and then transferred to the film. The transferred ink on the film was cured using a 160W/cm metal halogen UV lamp to obtain the printed material. The time from ink transfer to film to UV light irradiation was 1.88 seconds.

[Experimental Example 2] The following coating agent was mixed in a mixed solvent of water and isopropanol, with the solid content mass ratio of nitrogen-containing cationic antistatic agent/polyester resin/polyurethane resin solution changed to 5.0/76.0/19.0. Otherwise, the process was carried out in the same manner as in Experimental Example 1, yielding a white, easily adhesive polyester film and printed material. Nitrogen-containing cationic antistatic agent solution (A-1): 2.52 parts by mass (Solid concentration 17.50% by mass) Polyester aqueous dispersion (Bw-1): 22.67 parts by mass Polyurethane resin solution (C-1): 4.80 parts by mass Particles: 25.15 parts by mass (Silicon dioxide particles with an average particle size of 0.45 μm, solid concentration 40.00% by mass) Surfactant: 0.15 parts by mass (Silicone-based, solid concentration 10% by mass)

[Experimental Example 3] The following coating agent was mixed in a mixed solvent of water and isopropanol, with the solid content mass ratio of the nitrogen-containing cationic antistatic agent/polyester resin/polyurethane resin solution changed to 5.0/57.0/38.0. Otherwise, the process was carried out in the same manner as in Experimental Example 1, yielding a white, easily adhesive polyester film and printed material. Nitrogen-containing cationic antistatic agent solution (A-1): 2.52 parts by mass (Solid concentration 17.50% by mass) Polyester aqueous dispersion (Bw-1): 17.00 parts by mass Polyurethane resin solution (C-2): 9.71 parts by mass Particles: 25.15 parts by mass (Silicon dioxide particles with an average particle size of 0.45 μm, solid concentration 40.00% by mass) Surfactant: 0.15 parts by mass (Silicone-based, solid concentration 10% by mass)

[Experimental Example 4] The following coating agent was mixed in a mixed solvent of water and isopropanol, with the solid content mass ratio of the nitrogen-containing cationic antistatic agent/polyester resin/polyurethane resin solution changed to 5.0/57.0/38.0. Otherwise, the process was carried out in the same manner as in Experimental Example 1, resulting in a white, easily bondable polyester film. Nitrogen-containing cationic antistatic agent solution (A-2): 2.52 parts by weight (Solid concentration 17.50% by weight) Polyester aqueous dispersion (Bw-1): 17.00 parts by weight Polyurethane resin solution (C-1): 9.60 parts by weight Particles: 25.15 parts by weight (Silica particles with an average particle size of 0.45 μm, solid concentration 40.00% by weight) Surfactant: 0.15 parts by weight (Silicone-based, solid concentration 10% by weight)

[Experimental Example 5] The following coating agent was mixed in a mixed solvent of water and isopropanol, with the solid content mass ratio of the nitrogen-containing cationic antistatic agent/polyester resin/polyurethane resin solution changed to 5.0/57.0/38.0. Otherwise, the process was carried out in the same manner as in Experimental Example 1, resulting in a white, easily bondable polyester film. Nitrogen-containing cationic antistatic agent solution (A-1): 2.52 parts by mass (Solid concentration 17.50% by mass) Polyester resin solution (Bw-2): 20.40 parts by mass Polyurethane resin solution (C-1): 9.60 parts by mass Particles: 25.15 parts by mass (Silicon dioxide particles with an average particle size of 0.45 μm, solid concentration 40.00% by mass) Surfactant: 0.15 parts by mass (Silicone-based, solid content concentration 10% by weight)

[Experimental Example 6] The following coating agent was mixed in a mixed solvent of water and isopropanol, with the solid content mass ratio of nitrogen-containing cationic antistatic agent/polyester resin/polyurethane resin solution changed to 5.0/57.0/38.0. The coating was applied to a resin solid content thickness of 650 nm. Otherwise, the process was the same as in Experimental Example 1, yielding a white, easily adhesive polyester film and printed material. Nitrogen-containing cationic antistatic agent solution (A-1): 3.30 parts by weight (Solid concentration 19.20% by weight) Polyester aqueous dispersion (Bw-1): 30.00 parts by weight Polyurethane resin solution (C-1): 16.95 parts by weight Particles: 31.91 parts by weight (Benzoguanidine formaldehyde condensate particles with an average particle size of 2 μm, solid concentration 40.00% by weight) Surfactant: 0.40 parts by weight (Silicone-based, solid content concentration 10% by weight)

[Experimental Example 7] The following coating agent was mixed in a mixed solvent of water and isopropanol, with the solid content mass ratio of a nitrogen-containing cationic antistatic agent/polyester resin/polyurethane resin solution changed to 6.5/60.7/32.8. The coating was applied to a solid resin thickness of 50 nm. Otherwise, the process was the same as in Experimental Example 1, yielding a white, easily adhesive polyester film and printed material. Nitrogen-containing cationic antistatic agent solution (A-1): 2.45 parts by weight (Solid concentration 15.8% by weight) Polyester aqueous dispersion (Bw-1): 12.35 parts by weight Polyurethane resin solution (C-1): 6.27 parts by weight Surfactant: 0.25 parts by weight (Silicone-based, solid concentration 10% by weight)

[Experimental Example 8] The following coating agent was mixed in a mixed solvent of water and isopropanol, with the solid content mass ratio of nitrogen-containing cationic antistatic agent/polyester resin/polyurethane resin solution changed to 5.0/85.5/9.5. Otherwise, the process was carried out in the same manner as in Experimental Example 1, yielding a white, easily adhesive polyester film and printed material. Nitrogen-containing cationic antistatic agent solution (A) 2.52 parts by weight (Solid concentration 17.50% by weight) Polyester aqueous dispersion (Bw-1) 25.50 parts by weight Polyurethane resin solution (C-1) 2.40 parts by weight Particles 25.15 parts by weight (Silica particles with an average particle size of 0.45 μm, solid concentration 40.00% by weight) Surfactant 0.15 parts by weight (Silicone-based, solid concentration 10% by weight)

[Experimental Example 9] The following coating agent was mixed in a mixed solvent of water and isopropanol, with the solid content mass ratio of nitrogen-containing cationic antistatic agent/polyester resin/polyurethane resin solution changed to 5.0/28.5/67.0. Otherwise, the process was carried out in the same manner as in Experimental Example 1, yielding a white, easily adhesive polyester film and printed material. Nitrogen-containing cationic antistatic agent solution (A): 2.52 parts by mass (Solid concentration 17.50% by mass) Polyester aqueous dispersion (Bw-1): 8.50 parts by mass Polyurethane resin solution (C-1): 16.81 parts by mass Particles: 25.15 parts by mass (Silica particles with an average particle size of 0.45 μm, solid concentration 40.00% by mass) Surfactant: 0.15 parts by mass (Silicone-based, solid concentration 10% by mass)

[Experimental Example 10] The following coating agent was mixed in a mixed solvent of water and isopropanol, with the solid content mass ratio of the nitrogen-containing cationic antistatic agent/polyester resin/polyurethane resin solution changed to 5.0/57.0/38.0. Otherwise, the process was carried out in the same manner as in Experimental Example 1, yielding a white, easily adhesive polyester film and printed material. Nitrogen-containing cationic antistatic agent solution (A) 2.52 parts by mass (Solid concentration 17.50% by mass) Polyester aqueous dispersion (Bw-1) 17.00 parts by mass Polyurethane resin solution (C-3) 11.33 parts by mass Particles 25.15 parts by mass (Silicone particles with an average particle size of 0.45 μm, solid concentration 40.00% by mass) Surfactant 0.15 parts by mass (Silicone-based, solid concentration 10% by mass)

[Experimental Example 11] The following coating agent was mixed in a mixed solvent of water and isopropanol, with the solid content mass ratio of the nitrogen-containing cationic antistatic agent/polyester resin/polyurethane resin solution changed to 5.8/33.0/61.2. Otherwise, the process was carried out in the same manner as in Experimental Example 1, yielding a white, easily adhesive polyester film and printed material. Nitrogen-containing cationic antistatic agent solution (A) 2.83 parts by mass (Solid concentration 17.50% by mass) Polyester aqueous dispersion (Bw-1) 9.33 parts by mass Polyurethane resin solution (C-4) 26.00 parts by mass Particles (1) 16.31 parts by mass (Silicon dioxide particles with an average particle size of 0.45 μm, solid concentration 40.00% by mass) Particles (2) 5.44 parts by mass (Silicon dioxide particles with an average particle size of 1.00 μm, solid content concentration 40.00% by weight) Surfactant: 0.15 parts by weight (Silicone-based, solid content concentration 10% by weight)

[Experimental Example 12] The following coating agent was mixed in a mixed solvent of water and isopropanol, with the solid content mass ratio of a nitrogen-containing cationic antistatic agent/polyester resin/polyurethane resin solution changed to 5.8/33.0/61.2. The coating was applied to a solid resin thickness of 650 nm. Otherwise, the process was the same as in Experimental Example 1, yielding a white, easily adhesive polyester film and printed material. Nitrogen-containing cationic antistatic agent solution (A) 2.91 parts by mass (Solid concentration 19.20% by mass) Polyester aqueous dispersion (Bw-1) 11.67 parts by mass Polyurethane resin solution (C-4) 32.50 parts by mass Particles 21.27 parts by mass (Benzoguanidine particles with an average particle size of 2.00 μm, solid concentration 40.00% by mass) Surfactant 0.45 parts by mass (Silicone-based, solid concentration 10% by mass)

The evaluation results of each experimental case are summarized in Tables 1 and 2.

[Table 1] coating Solid composition mass ratio (mass of each solid component relative to the solid components of antistatic agent, polyester resin, and polyurethane resin) Coating thickness [nm] Surface elemental distribution determination of characteristic values using ESCA Regarding the angle of contact with water Antistatic agent Polyester resin Polyurethane resin Antistatic agent Polyester resin Polyurethane resin A [at%] B/A [─] [°] Experimental Example 1 A-1 Bw-1 C-1 5.0 57.0 38.0 450 0.5 3.4 67 Experimental Example 2 A-1 Bw-1 C-1 5.0 76.0 19.0 450 0.5 3.2 67 Experimental Example 3 A-1 Bw-1 C-2 5.0 57.0 38.0 450 0.7 2.4 61 Experimental Example 4 A-2 Bw-1 C-1 5.0 57.0 38.0 450 0.5 3.4 67 Experimental Example 5 A-1 Bw-2 C-1 5.0 57.0 38.0 450 0.8 2.3 67 Experimental Example 6 A-1 Bw-1 C-1 5.0 57.0 38.0 650 0.6 4.3 56 Experimental Example 7 A-1 Bw-1 C-1 5.0 57.0 38.0 50 0.8 2.1 59 Experimental Example 8 A-1 Bw-1 C-1 5.0 85.5 9.5 450 0.4 5.3 68 Experimental Example 9 A-1 Bw-1 C-1 5.0 28.5 67.0 450 0.8 1.5 65 Experimental Example 10 A-1 Bw-1 C-3 5.0 57.0 38.0 450 0.7 1.3 69 Experimental Example 11 A-1 Bw-1 C-4 5.8 33.0 61.2 450 0.9 2.3 49 Experimental Example 12 A-1 Bw-1 C-4 5.8 33.0 61.2 650 0.8 2.5 40

[Table 2] Surface resistance Closeness assessment initial Store at 80℃/90% humidity Solvent-based inks Oxidative polymer inks Heat transfer ink LBP toner UV-curable inks Screen printing ink Oxidative polymer inks Heat transfer ink LBP toner UV offset ink Experimental Example 1 ◎ 5 5 5 5 5 5 5 5 5 5 Experimental Example 2 ○ 5 5 5 5 5 5 5 5 5 5 Experimental Example 3 ◎ 5 5 5 5 5 5 5 5 5 5 Experimental Example 4 ◎ 5 5 5 5 5 5 5 5 5 5 Experimental Example 5 ◎ 5 5 5 5 5 5 5 5 5 5 Experimental Example 6 ◎ 5 5 5 5 5 5 5 5 5 5 Experimental Example 7 ○ 5 5 5 5 4 5 5 5 5 4 Experimental Example 8 × 4 4 4 2 4 3 3 3 2 1 Experimental Example 9 ◎ 5 5 5 5 4 3 2 2 1 2 Experimental Example 10 ○ 5 5 5 4 3 3 3 3 1 1 Experimental Example 11 ◎ 5 5 5 5 4 2 2 2 1 1 Experimental Example 12 ◎ 5 5 5 5 4 3 3 3 2 2

It can be seen that the printed materials obtained in Examples 1 to 7 exhibit excellent adhesion to various inks or toners, especially regarding adhesion to UV-cured ink layers, such as active energy line-cured inks. Even when stored in high-temperature and high-humidity environments, the adhesion to these ink layers does not decrease. On the other hand, in Examples 8 to 12, the A value, B/A value, and water contact angle of the substrate with the easily adhesive coating were inappropriate. As a result, the antistatic properties and adhesion to various ink layers when stored in high-temperature and high-humidity environments after printing may not be satisfactory. [Industrial Applicability]

According to the present invention, a printed material is provided that has excellent adhesion to various ink components, and the adhesion to the ink layer will not decrease even when stored in a high temperature and high humidity environment.

Solid line: Measured data of the N1s spectrum of the easily adhesive coating surface Dotted line: Curve representing the ionized nitrogen peak obtained by peak separation of the N1s spectrum Dashed line: Curve representing the unionized nitrogen peak obtained by peak separation of the N1s spectrum (1): Ionized nitrogen peak (2): Unionized nitrogen peak

[Figure 1] is an explanatory diagram used to determine the nitrogen element ratio A (at%) derived from the antistatic agent and the nitrogen element ratio B (at%) derived from the aforementioned polyurethane resin on the surface element distribution of the easily bondable coating surface in this invention, based on the surface element distribution measured by X-ray photoelectron spectroscopy.

Thin solid line: Measured data of the N1s spectrum of easily adhesive coating surfaces.

Dotted line: Represents the curve of the ionized nitrogen peaks obtained by peak separation of the N1s spectrum.

Dashed line: Represents the curve of the unionized nitrogen peaks obtained by peak separation of the N1s spectrum.

(1): Nitrogen peak after ionization

(2): Nitrogen peak without ionization

Claims (3)

A printed material having an adhesive coating layer on a polyester film substrate, wherein at least one ink layer is deposited on the adhesive coating layer, the ink layer being selected from UV-curable ink, solvent-based ink, oxidative polymerization ink, thermal transfer ink ribbon, and laser printer toner; the nitrogen ion concentration A(at%) and nitrogen element ratio B(at%) of the surface of the adhesive coating layer, determined by surface elemental distribution using X-ray photoelectron spectroscopy, satisfy the following formulas (i) and (ii), and the contact angle _θH₂O of the surface of the adhesive coating layer with water satisfies the following formula (iii); (i) A(at%) >0.4;(ii)2.0≦B/A≦5.0; (iii)50°≦θH ₂ O≦70°. The printed material described in claim 1, wherein the aforementioned adhesive coating is formed by curing a composition comprising a cationic antistatic agent, polyurethane resin and polyester resin. The printed matter described in claim 1 or 2, wherein the aforementioned polyester film substrate is a white polyester film substrate containing inorganic particles and/or thermoplastic resins that are immiscible with polyester resins.