Easily bondable polyester film

Abstract

[Problem] To provide: a readily-adhesive polyester film improved in reliability of adhesion to a functional layer such as a hard coat layer, and a readily-adhesive polyester film suitable for optical use and the like. [Solution] A readily-adhesive polyester film having a coating layer on at least one side of a polyester film, the coating layer being formed by curing a composition containing a polyester having a polycyclic aromatic skeleton and a cross-linking agent having a skeleton selected from at least one of aliphatic, alicyclic, and heterocyclic, the readily-adhesive polyester film satisfying a specific relationship among a thickness of the coating layer, a surface free energy of a coating layer surface on a side of the coating layer not in contact with the polyester film, a nitrogen atom ratio of the coating layer surface, and a characteristic value related to the nitrogen atom ratio in a depth direction of the coating layer.

Description

Technical Field

[0001] This invention relates to easy-to-adhere polyester films exhibiting excellent adhesion to various functional layers, anti-blocking properties, and transparency. More specifically, it relates to easy-to-adhere polyester films also suitable for optical applications. Background Technology

[0002] Hard-coated films with a transparent hard coating layer are used on the front surfaces of touch panels, displays for computers, televisions, LCD devices, and decorative materials. Additionally, transparent polyester films are commonly used as the substrate for the transparent plastic film. To improve the adhesion between the polyester film and the hard coating, an easily adhesive coating layer is often applied to the surface of the polyester film as an interlayer.

[0003] The aforementioned hard-coated films require specific temperature, humidity, light resistance, transparency, chemical resistance, scratch resistance, and stain resistance. Furthermore, since they are mostly used on the surfaces of displays and decorative materials, visibility and design flexibility are also crucial. Therefore, to suppress glare and iridescent colors caused by reflected light when viewed from any angle, the following is generally performed: a multi-layered anti-reflective layer consisting of stacked high-refractive-index and low-refractive-index layers is applied on top of the hard coating.

[0004] In recent years, hard coatings with various skeletons have been developed, and the adhesion between the substrate and the hard coating is discussed each time. Not only is initial adhesion required immediately after lamination, but also resistance to damp heat, adhesion retention, and degradation of adhesion over time are required to ensure the long-term reliability of LCD TVs using films with laminated hard coatings, and products with various evaluation resistances are also required.

[0005] In the existing field of easily bondable polyester films, when using polyester resins containing naphthalene dicarboxylic acid as a coating layer with easily bondable properties, excellent adhesion to the substrate polyester film is proposed as a suitable example (see, for example, Patent Document 1). Furthermore, as a resin with excellent flexibility and high adhesion, a method using polyurethane resins containing polycarbonate components has been proposed (see, for example, Patent Document 2).

[0006] However, although the seal was confirmed, the seal of the easy-to-adhere polyester film could not be guaranteed after long-term storage.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2011-246663

[0010] Patent Document 2: Japanese Patent Application Publication No. 2011-168053 Summary of the Invention

[0011] The problem the invention aims to solve

[0012] This invention was made with the aforementioned problems of the prior art in mind. Specifically, the object of this invention is to provide an easy-to-adhere polyester film that improves the reliability of adhesion to functional layers such as hard coatings, and to provide an easy-to-adhere polyester film suitable for optical applications, etc.

[0013] In order to achieve the above objectives, the inventors conducted in-depth research and came up with the present invention.

[0014] That is, the present invention comprises the following components.

[0015] 1. An easily bondable polyester film having a coating layer on at least one side of the polyester film, said coating layer being formed by curing a composition comprising a polyester having a polycyclic aromatic backbone and a crosslinking agent having at least one backbone selected from aliphatic, alicyclic, and heterocyclic groups.

[0016] The thickness (d: nm) of the aforementioned coating layer satisfies the following equation (1).

[0017] The surface free energy (γs: mN / m) of the coating layer surface that is not in contact with the polyester film satisfies the following equation (2).

[0018] Based on X-ray photoelectron spectroscopy (ESCA), the nitrogen atom ratio (A) on the surface of the coating layer is... N :at%) satisfies the following equation (3),

[0019] In the nitrogen distribution curve determined based on depth-direction elemental distribution, the ratio of time t2 (seconds) to time t1 (seconds) (t2 / t1) satisfies the following equation (4), where time t1 is the lower limit value of the nitrogen atom ratio (A). N Y: at%) time, where time t2 is the time when the nitrogen atom ratio reaches its maximum value (A N X: at% and the aforementioned A N The median value of Y (A) N Z: at% time.

[0020] 30≤d≤200···Equation (1)

[0021] 43≤γs≤49···Equation (2)

[0022] 3.0≤A N ≤9.5···Equation (3)

[0023] (t2 / t1)×100≥40···Equation (4)

[0024] 2. The easily bondable polyester film according to the first description above, wherein the adhesion X (%) when a hard coating layer is applied to the aforementioned coating layer after film formation is 95% or higher.

[0025] The aforementioned adhesion X and the adhesion Y (%) after being placed in an environment of 80°C and 90%RH for 24 hours and then having a hard coating layer applied to the coating layer satisfy the following formula (5).

[0026] XY(%)≤5···Equation (5)

[0027] 3. The easily adhesive polyester film according to the first or second description above, wherein the aforementioned polyester having a polycyclic aromatic backbone is a polyester having a naphthalene backbone.

[0028] 4. The easily bondable polyester film according to any one of the above-mentioned 1 to 3, wherein the aforementioned crosslinking agent having at least one backbone selected from aliphatic, alicyclic, and heterocyclic groups is an isocyanate crosslinking agent having at least one backbone selected from aliphatic, alicyclic, and heterocyclic groups.

[0029] The effects of the invention

[0030] According to the present invention, an easy-to-adhere polyester film that ensures reliable adhesion to functional layers such as hard coatings after long-term storage can be provided, and can be widely used in optical applications, etc. Attached Figure Description

[0031] Figure 1 This is an example of a nitrogen distribution curve for the easily bondable polyester film of the present invention, based on the elemental distribution determined by etching from the surface of the coating layer along the depth direction according to ESCA.

[0032] Figure 2 This is an example of a nitrogen distribution curve for the easily bondable polyester film of Example 1, based on the elemental distribution determined by etching from the surface of the coating layer along the depth direction according to ESCA. Detailed Implementation

[0033] (Polyester film)

[0034] The polyester film used as a substrate in this invention is a film mainly composed of polyester resin. Here, "film mainly composed of polyester resin" means a film formed from a resin composition containing 50% by mass or more of polyester resin. When blended with other polymers (e.g., polycarbonate resin, polyimide resin, etc.), it means containing 50% by mass or more of polyester resin; when copolymerized with other monomers, it means containing 50 mol% or more of polyester structural units. Preferably, the polyester film contains 90% by mass or more of polyester resin, more preferably 95% by mass or more, and even more preferably 100% by mass.

[0035] The materials used for polyester resins are not particularly limited, and copolymers or blends thereof formed by polycondensation of dicarboxylic acid components and diol components can be used. Examples of dicarboxylic acid components include terephthalic acid, isophthalic acid, phthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonecarboxylic acid, anthracene dicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyl adipic acid, trimethyl adipic acid, heptacyanic acid, azelaic acid, dimer acid, sebacic acid, octanoic acid, dodecanedicarboxylic acid, etc.

[0036] Examples of diols that constitute polyester resins include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanediethanol, 1,4-cyclohexanediethanol, decamethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis(4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone.

[0037] One or more dicarboxylic acid components and two glycol components can be used to constitute the polyester resin. In addition, other acid components such as trimellitic acid and other hydroxyl components such as trimethylolpropane can also be appropriately added.

[0038] Specifically, examples of polyester resins include polyethylene terephthalate, polyethylene terephthalate, polyethylene terephthalate, and polyethylene naphthalate. Among these, polyethylene terephthalate is preferred due to its balance between physical properties and cost. Furthermore, including other copolymer components and other polymers is also a preferred approach to control optical properties such as polarization. From the viewpoint of controlling the optical properties of the polyester film, preferred copolymer components include diethylene glycol and copolymer components with norbornene in their side chains.

[0039] To improve the operability of polyester films, such as their slip properties and winding properties, inactive particles are sometimes included in the film. However, to maintain high transparency, it is preferable that the content of inactive particles in the film be as low as possible. Therefore, it is preferable to have a multilayer structure in which particles are contained only in the surface layer of the film, or to have a film that is substantially free of particles, with particles contained only in at least one side of the cover layer laminated on the polyester film.

[0040] It should be noted that "substantially free of particles," for example in the case of inorganic particles, means that the content of elements originating from particles is below 50 ppm, preferably below 10 ppm, and below the most preferred detection limit when quantitatively analyzed by fluorescence X-ray analysis. This is because even if particles are not actively added to the substrate film, contaminants from foreign sources, raw material resins, or contaminants adhering to pipelines or equipment in the film manufacturing process can inevitably be mixed into the film.

[0041] In addition, when the polyester film is made into a multilayer structure, two three-layer structures are preferred, in which the inner layer is substantially free of inactive particles and only the outermost layer contains inactive particles, which can balance transparency and processability.

[0042] The polyester film serving as the substrate can be a single layer or a composite of two or more layers. Furthermore, various additives can be included in the film as needed, provided that the effects of this invention are achieved. Examples of additives include antioxidants, lightfastness agents, anti-gelling agents, organic wetting agents, antistatic agents, ultraviolet absorbers, and surfactants. When the film has a laminated structure, it is preferable to include additives according to the function of each layer. For example, adding ultraviolet absorbers to the inner layers is a preferred method to prevent light degradation of the polarizer.

[0043] Polyester film can be manufactured using conventional methods. For example, it can be obtained by melting and extruding the aforementioned polyester resin into a film shape, and then cooling and solidifying it on a casting drum to form a film. As the polyester film in this invention, both unstretched and stretched films can be used, but stretched films are preferred from the perspective of durability, such as mechanical strength and chemical resistance. When the polyester film is a stretched film, the stretching method is not particularly limited; longitudinal uniaxial stretching, transverse uniaxial stretching, sequential longitudinal and transverse biaxial stretching, and simultaneous longitudinal and transverse biaxial stretching can be used. When stretching the polyester film, stretching can be performed before or after the easy-to-adhere coating layer (described later). Alternatively, uniaxial stretching can be performed longitudinally or transversely before the easy-to-adhere coating layer is stacked, and stretching can be performed in other directions after the cover layer is stacked.

[0044] (Coating layer)

[0045] The easy-to-adhesive polyester film of the present invention is formed by laminating an easy-to-adhesive coating layer onto the aforementioned polyester substrate film. The coating layer contains an adhesive resin and additives.

[0046] The components of the coating layer are described in detail below.

[0047] As the binder resin constituting the coating layer, a resin with good adhesion is preferred. From the viewpoint of particle retention and adhesion, polyester is most suitable. Furthermore, in this invention, polyester having a polycyclic aromatic backbone is most suitable. It also has compatibility with the composition of the hard coating layer described later, but when the composition of the hard coating layer has an aromatic backbone, it is also suitable from the viewpoint of conjugated interaction.

[0048] Specific examples of polyesters having a polycyclic aromatic backbone include polyesters with a naphthalene backbone, polyesters with a fluorene backbone, polyesters with anthracene backbone, and polyesters with a phenanthrene backbone.

[0049] In this invention, the binder resin constituting the coating layer is preferably free of polyurethane resin. While polyurethane resin is used from the viewpoint of the coating's elasticity and formability, it is obvious that urea compounds are introduced as impurities due to the polyurethane resin. If the amount of urea compounds present in the coating layer becomes excessive, it is preferable to be free of polyurethane resin from the viewpoint of maintaining the long-term stability of adhesion.

[0050] The composition for forming the coating layer preferably contains 10% by mass or more and 90% by mass or less of the aforementioned polyester in its total solid components of resin and crosslinking agent. More preferably, it contains 15% by mass or more and 85% by mass or less. When the polyester resin content is 90% by mass or less, it is preferable to maintain adhesion to functional layers such as hard coatings under high temperature and high humidity conditions. Conversely, if the content is 10% by mass or more, it is preferable to easily maintain adhesion to the polyester substrate film under room temperature and high temperature and high humidity conditions.

[0051] In this invention, a crosslinking agent is preferably included to form a crosslinked structure in the coating layer. Furthermore, the crosslinking agent is preferably a crosslinking agent having at least one backbone selected from aliphatic, alicyclic, and heterocyclic groups. Additionally, a crosslinking agent capable of generating urea groups through a crosslinking side reaction is suitable; specific examples of crosslinking agents include isocyanate-based crosslinking agents and carbodiimide-based crosslinking agents. Among these, isocyanate crosslinking agents are suitable due to their improved stability over time and adhesion under high temperature and humidity conditions. Furthermore, in this invention, isocyanates having at least one backbone selected from aliphatic, alicyclic, and heterocyclic groups are most suitable. Additionally, a catalyst or the like may be appropriately used in the coating layer forming composition as needed to promote the crosslinking reaction.

[0052] Specific examples of aliphatic isocyanates include 1,4-diisocyanate alkylbutane, 1,5-pentamethylene diisocyanate, 2-methyl-1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecane diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, 2,4,4-trimethyl-1,6-hexamethylene diisocyanate, and 3,5,5-trimethyl-1,6-hexamethylene diisocyanate.

[0053] Specific examples of alicyclic isocyanates include cyclohexane diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,3-bis(isocyanate methyl)cyclohexane, 1,4-bis(isocyanate methyl)cyclohexane, cyclohexyl 1,4-diisocyanate, 1,1-bis(isocyanate methyl)cyclohexane, 2,4-hexahydromethylphenylene diisocyanate, and 2,6-hexahydromethylphenylene diisocyanate.

[0054] Specific examples of heterocyclic isocyanates include 2,5-diisocyanate thiophene, 2,5-bis(isocyanate methyl)thiophene, 2,5-diisocyanate tetrahydrothiophene, 2,5-bis(isocyanate methyl) tetrahydrothiophene, 3,4-bis(isocyanate methyl) tetrahydrothiophene, 2,5-diisocyanate-1,4-dithiane, 2,5-bis(isocyanate methyl)-1,4-dithiane, 4,5-diisocyanate-1,3-dithiopentane, 4,5-bis(isocyanate methyl)-1,3-dithiopentane, and 4,5-bis(isocyanate methyl)- 2-Methyl-1,3-dithiopentane, 2,6-di(isocyanate methyl)furan, 5,5'-methylene difurfuryl isocyanate, 5,5'-isopropylidene difurfuryl isocyanate, or trimers of diisocyanates, 2,4,6-trioxohexahydro-1,3,5-triazine-1,3,5-triphenylmethyltris(6,1-hexanediyl)triisocyanate with a triazine ring and known as isocyanurates, 1,3,5-tris[(5-isocyanate oxy-1,3,3-trimethylcyclohexyl)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, etc.

[0055] In this invention, isocyanates with aromatic skeletons are highly reactive and readily react with moisture in the air, promoting the formation of urea compounds more than desired. Therefore, they are preferably not included in the composition for forming the coating layer. Furthermore, from the viewpoint of weather resistance, isocyanates with at least one aliphatic, alicyclic, or heterocyclic skeleton are also preferred. Additionally, in this application, end-capped isocyanates can also be used, especially when the coating agent is aqueous, which is particularly preferred from the viewpoint of suppressing the formation of urea compounds.

[0056] Examples of end-capping agents include sodium bisulfite and other bisulfite compounds, pyrazole compounds such as 3,5-dimethylpyrazole, 3-methylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 4-nitro-3,5-dimethylpyrazole, phenols such as phenol and cresol, aliphatic alcohols such as methanol and ethanol, active methylene compounds such as dimethyl malonate and acetylacetone, thiols such as butyl mercaptan and dodecyl mercaptan, acid amides such as acetanilide and acetamide, lactams such as ε-caprolactam and δ-valeronamide, acid imides such as succinic imide and maleic imide, oximes such as acetaldehyde oxime, acetone oxime, and methyl ethyl ketone oxime, and amines such as diphenylaniline, aniline, and ethyleneimine.

[0057] Furthermore, from the viewpoint of imparting water dispersibility to aqueous solvents, it is preferable to introduce hydrophilic groups into the end-capped isocyanate-based crosslinking agent. Moreover, as hydrophilic, it is preferable to introduce anionic groups such as carboxyl or sulfonic acid groups, or nonionic groups such as alkyl groups. These hydrophilic groups can be prepared by pre-reacting a polyisocyanate, which forms the basis of the end-capped isocyanate, with a compound having hydrophilic groups and reactive groups such as hydroxyl groups.

[0058] The composition for forming the coating layer preferably contains 5% by mass and 50% by mass or less of the aforementioned crosslinking agent in its total solid components of resin and crosslinking agent. More preferably, it contains 10% by mass and 45% by mass or less. Even more preferably, it contains 10% by mass and 30% by mass or less, and most preferably, it contains 10% by mass and 20% by mass or less. If it is 5% by mass or more, the strength of the resin in the coating layer is maintained, and the adhesion under high temperature and high humidity is good. If it is 50% by mass or less, the softness of the resin in the coating layer is maintained, and the adhesion under normal temperature, high temperature and high humidity is maintained, which is preferred.

[0059] The coating layer in the easily adhesive polyester film of the present invention is preferably formed by curing a composition comprising a polyester having a polycyclic aromatic backbone and a crosslinking agent having at least one backbone selected from aliphatic, alicyclic, and heterocyclic groups. Because the performance of the cured composition is difficult to adequately represent the chemical composition after curing due to the reaction caused by the crosslinking agent, this description is provided.

[0060] (additive)

[0061] In the coating layer of this invention, known additives such as surfactants, antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic slip agents, pigments, dyes, organic or inorganic particles, antistatic agents, nucleating agents, etc., may be added without impairing the effects of the invention. However, it is preferable not to use substances that are environmentally unfriendly.

[0062] In this invention, adding particles to the coating layer is a preferred method to further improve the anti-blocking properties of the coating layer. Examples of particles contained in the coating layer of this invention include titanium dioxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, or mixtures thereof. Furthermore, examples include inorganic particles used in combination with other common inorganic particles, such as calcium phosphate, mica, lithium montmorillonite, zirconium oxide, tungsten oxide, lithium fluoride, calcium fluoride, etc., as well as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, organosilicon-based, and other organic polymer particles.

[0063] The average particle size (average particle size based on the number of particles in SEM, the same applies below) of the inactive particles in the coating layer is preferably 0.04 to 2.0 μm, more preferably 0.1 to 1.0 μm. If the average particle size of the inactive particles is 0.04 μm or more, it is easy to form unevenness on the film surface, thus improving the film's operability such as sliding and winding properties, and resulting in good processability during lamination, which is preferable. On the other hand, if the average particle size of the inactive particles is 2.0 μm or less, it is preferable that particle shedding is less likely to occur. The particle concentration in the coating layer is preferably 1 to 20% by mass relative to the resin composition.

[0064] In this invention, the thickness (d: nm) of the coating layer is preferably as shown in the following formula (1).

[0065] 30≤d≤200···Equation (1)

[0066] As long as the preparation is within this range, it is easy to balance processability and adhesion, so it is preferred.

[0067] More preferably, the thickness is 50 nm or more and 150 nm or less, and even more preferably 70 nm or more and 100 nm or less. A coating thickness of 30 nm or more is preferred as it provides good adhesion. A coating thickness of 200 nm or less is preferred as it is less prone to adhesion.

[0068] The thickness of the coating layer is as follows: The cross-section of the cut film was observed using a transmission electron microscope (TEM), and the average value of 10 randomly measured points was taken as the thickness of the coating layer.

[0069] The surface free energy (γs: mN / m) of the coating layer present on the surface of the easily adhesive polyester film of the present invention is preferably within the range of the following formula (2).

[0070] 43≤γs≤49···Equation (2)

[0071] As long as it is adjusted to this range, the bonding reliability can be ensured, and the features of this invention can be met.

[0072] More preferably, the strength is 44 mN / m or higher and 48 mN / m or lower; even more preferably, it is 45 mN / m or higher and 47 mN / m or lower. If it is 43 mN / m or higher, the proportion of segregated components that are unevenly present on the surface of the coating layer is small, resulting in good adhesion to subsequent hard coatings, etc., and is particularly preferred as it ensures the long-term stability and reliability of the adhesion. Furthermore, if it is 49 mN / m or lower, it is preferred as it better maintains the initial adhesion to the hard coating.

[0073] This invention focuses on the proportion of segregated components (mainly crosslinking agent components) present from the surface to the interior of the coating layer.

[0074] The term "segregated components" here refers to urea compounds and urethane compounds that are present in the crosslinking agent component of the coating layer forming composition and deform due to reaction with moisture in the air. These compounds tend to segregate on the surface, and are therefore considered to be the main cause of reduced adhesion to hard coatings, etc.

[0075] When observing the coating layer present on the surface of the easily bondable polyester film of this invention using X-ray photoelectron spectroscopy (ESCA), the ratio of the amount of nitrogen atoms to the total amount of all elements (nitrogen atom ratio: A) is determined. N :at%) is preferably within the range of the following formula (3).

[0076] 3.0≤A N ≤9.5···Equation (3)

[0077] As long as the setting is within this range, the bonding reliability can be ensured, so it is the preferred option.

[0078] More preferably, it is 5.0 at% or more and 9.3 at% or less, and even more preferably, it is 7.0 at% or more and 9.0 at% or less. It is preferred to set it to 3.0 at% or more, so that the initial adhesion with the hard coating is good. If it is 9.5 at% or less, the adhesion with the hard coating is stable over time, and the adhesion reliability can be maintained.

[0079] In the ESCA measurement, when etching along the depth direction from the surface of the coating layer of the easily adhesive polyester film of the present invention, and plotting the nitrogen element distribution curve based on the elemental distribution at each depth direction position, the following is obtained: Figure 1 The spectrum shown is as follows (horizontal axis: etching time (seconds), vertical axis: nitrogen atom ratio (at%)).

[0080] In the obtained distribution curve, the time (t1) (seconds) when the nitrogen atom ratio reaches its lower limit and the time (A) when it reaches its maximum value are taken. N X) and lower limit (A) N The median value of Y) (A) NWhen the time (t2) (seconds) of Z) is , it is preferably within the range of the following formula (4).

[0081] (t2 / t1)×100≥40···Equation (4)

[0082] A N The time (t2) under Z refers to the time when it becomes the maximum value (A). N X) and lower limit (A) N The location of the midpoint of Y) means that the ratio of (t2) to (t1) refers to the magnitude of the nitrogen atom ratio in the depth direction.

[0083] That is, the larger the value of the ratio of (t2) to the overall amplitude (t1) in the depth direction, the slower the change in the amount of segregated components on the surface of the coating layer.

[0084] More preferably, 47 or higher, and even more preferably 55 or higher. If it is 40 or higher, the amount of segregated components becomes less, and therefore, due to this effect, the sealing reliability can be maintained, which is preferred.

[0085] There are no particular limitations on the methods used to satisfy the aforementioned formulas (2), (3), and (4). The type and ratio of resin and crosslinking agent in the composition for forming the coating layer can be preferably adjusted by controlling these factors.

[0086] Moreover, when all the relationships of these equations (1) to (4) are satisfied, an easy-to-adhere polyester film with excellent transparency, anti-adhesion, and adhesion to hard coatings, etc., and especially with high adhesion stability over time and high reliability as a film, can be obtained.

[0087] The coating layer forming composition may contain surfactants to improve leveling and defoaming of the coating liquid during coating. The surfactants can be cationic, anionic, or nonionic, but silicone, acetylene glycol, or fluorinated surfactants are preferred. These surfactants are preferably included in the coating layer forming composition within a range that does not impair the suppression of iridescent color under fluorescent light or the degree of adhesion.

[0088] As a coating method, either the so-called online coating method, in which coating is performed simultaneously when the film is made into a polyester substrate film, or the so-called offline coating method, in which coating is performed separately using a coating machine after the film is made into a polyester substrate film, can be applied. The online coating method is effective and more preferred.

[0089] As a coating method, any known method can be used to coat the coating liquid onto a polyethylene terephthalate (PET) film. Examples include reverse roller coating, gravure coating, coincidence coating, die coating, roller brush coating, spray coating, air knife coating, wire rod coating, tube blade coating, dip coating, curtain coating, etc. These methods can be used individually or in combination.

[0090] In this invention, a method for forming a coating layer on a polyester film can be described as applying a coating liquid containing a solvent, particles, and resin onto the polyester film and then drying it. As a solvent, water or a mixture of water and an organic solvent can be used; preferably, from an environmental perspective, water alone or in a mixture of water and a water-soluble organic solvent is preferred.

[0091] Examples of water-soluble organic solvents include isopropanol, ethanol and other alcohols, methyl ethyl ketone and other ketones, butyl cellosolve and other ethers, triethanolamine and other amines, and N-methylpyrrolidone and other amides.

[0092] The concentration of solids in the coating solution also depends on the type of binder resin, the type of solvent, etc., and is preferably 2% by mass or more, more preferably 4% by mass or more. The concentration of solids in the coating solution is preferably 35% by mass or less, more preferably 15% by mass or less.

[0093] The drying temperature after coating also depends on the type of adhesive resin, the type of solvent, the presence or absence of crosslinking agent, and the concentration of solid components, preferably above 80°C and preferably below 250°C.

[0094] (Manufacturing of easy-to-adhere polyester film)

[0095] The polyester film that serves as the substrate for the easily adhesive polyester film of the present invention can be manufactured according to a general polyester film manufacturing method. For example, the following method can be used: melting polyester resin, extruding and molding it into a sheet to obtain a non-oriented polyester, stretching the obtained non-oriented polyester longitudinally at a temperature above the glass transition temperature using the speed difference of the rollers, and then stretching it transversely using a tenter frame and performing heat treatment.

[0096] The polyester film in this invention can be a uniaxially stretched film or a biaxially stretched film. When a biaxially stretched film is used as a protective film in front of the liquid crystal panel, no rainbow-like color spots are seen even when viewed from directly above the film surface. However, rainbow-like color spots are sometimes observed when viewed from an oblique direction. Therefore, this should be noted.

[0097] This phenomenon occurs because biaxially stretched films are composed of refractive index ellipsoids with different refractive indices in the traveling direction, width direction, and thickness direction. A direction exists where the retardation is zero (the refractive index ellipsoid is visible as a perfect circle) depending on the transmission direction of light within the film. Therefore, if a liquid crystal display image is observed from a specific angle, a point where the retardation is zero sometimes appears, and an iridescent spot is generated in concentric circles around this point. Furthermore, if the angle from directly above the film surface (normal direction) to the position where the iridescent spot can be observed is defined as θ, the greater the birefringence within the film surface, the larger this angle θ becomes, and the more difficult it becomes to observe the iridescent spot. In biaxially stretched films, there is a tendency for the angle θ to become smaller; therefore, in the case of uniaxially stretched films, it becomes less likely to observe the iridescent spot, which is preferable.

[0098] However, in a completely uniaxial (uniaxially symmetric) thin film, the mechanical strength in the direction perpendicular to the orientation direction is significantly reduced, and therefore it is not preferred. The present invention preferably exhibits biaxiality (biaxial objectivity) within a range where rainbow-like spots are not substantially produced, or within a viewing angle range required by the liquid crystal display image.

[0099] (Laminated polyester film)

[0100] A functional layer, such as a hard coating, is laminated onto the coating layer of the easily adhesive polyester film of the present invention. As a laminated polyester film, it is preferably used for optical applications. A hard coating or the like, formed of an electron beam or ultraviolet-curable acrylic resin or a siloxane-based thermosetting resin, may be provided on the aforementioned coating layer.

[0101] It is also preferred to provide various functional layers on the coating layer of the easily adhesive polyester film of the present invention. Functional layers refer to layers that, in addition to the aforementioned hard coating layer, have functions such as anti-glare layers, anti-glare and anti-reflective layers, anti-reflective layers, low-reflection layers, and antistatic layers, for purposes such as anti-reflection, glare suppression, suppression of iridescent unevenness, and scratch suppression. Various materials known in the art can be used for functional layers, and there are no particular limitations on their types. The following describes each functional layer.

[0102] For example, in the formation of a hard coating, known hard coating materials can be used without particular limitation. Resin compounds that polymerize and / or react through drying, heat, chemical reaction, or irradiation with an electron beam, radiation, or ultraviolet light can be used. Examples of such curable resins include melamine-based, acrylic-based, silicone-based, and polyvinyl alcohol-based curable resins. For achieving high surface hardness or optical design, photocurable acrylic-based curable resins are preferred. As such acrylic-based curable resins, polyfunctional (meth)acrylate monomers and acrylate oligomers can be used. Examples of acrylate oligomers include polyester acrylates, epoxy acrylates, urethane acrylates, polyether acrylates, polybutadiene acrylates, and silicone acrylates. By mixing reaction diluents, photopolymerization initiators, sensitizers, etc., with these acrylic-based curable resins, a coating composition for forming the aforementioned optical functional layer can be obtained.

[0103] The aforementioned hard coating can have an anti-glare function that scatters external light. This anti-glare function can be achieved by forming an uneven surface on the hard coating. Ideally, the haze of the film is 0-50%, more preferably 0-40%, and particularly preferably 0-30%. Of course, 0% is ideal, but it can be 0.2% or more, or 0.5% or more.

[0104] Furthermore, in order to implement a low-reflection processing (anti-reflection processing) that suppresses light reflection by altering the light transmission characteristics by imparting layers with different refractive indices, it is preferable to adjust the refractive indices of the hard coating and functional layer to ideally achieve a reflectivity of 0 to 1.0%, more preferably 0 to 0.8%, and particularly preferably 0 to 0.5%. Of course, 0% is ideal, but it can be 0.05% or more, or 0.1% or more.

[0105] In particular, as the hard coating composition used in this invention, in order to adjust the refractive index, a resin containing aromatic components in a proportion of 5 mol% or more and 20 mol% or less relative to the total molar number of monomers and oligomers constituting the resin is generally used.

[0106] The applications of the easily adhesive polyester film of the present invention and the laminated polyester film having a functional layer stacked on its coating layer mainly cover all optical films, and are particularly suitable for base films for optical components such as LCDs, flat panel TVs, and CRTs, such as prism lenses, AR (anti-reflective) films, hard-coated films, diffusers, and shatterproof films; transparent conductive films for near-infrared absorption filters, touch panels, electroluminescent materials, etc., located as components in the front panel of plasma displays.

[0107] As for the acrylic resin that is cured by electron beam or ultraviolet light to form the above-mentioned hard coating, specifically, it is one that has acrylate or methacrylate functional groups. For example, low molecular weight polyester resins, polyether resins, acrylic resins, epoxy resins, polyurethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, and polythiol polyene resins can be used; oligomers or prepolymers containing polyfunctional compounds such as polyols and (meth)acrylates; and monofunctional monomers such as (meth)acrylate and (meth)acrylate, as reactive diluents, and polyfunctional monomers such as trimethylolpropane tri(meth)acrylate, hexanediol (meth)acrylate, tripropylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, etc.

[0108] Furthermore, in the case of electron beam or ultraviolet curable resins, the aforementioned resins can be mixed with acetophenones, benzophenones, mifepristone benzoate, α-amyloxim ester, tetramethylthiuram monosulfide, thioxanones as photopolymerization initiators, or they can be mixed with n-butylamine, triethylamine, tri-n-butylphosphine, etc. as photosensitizers.

[0109] Furthermore, organosilicon (siloxane-based) thermosetting resins can be manufactured by hydrolyzing and condensing two or more organosilicon compounds, either alone or in combination, under acid or alkaline catalysts. In particular, for applications requiring low reflectivity, further improvements are made in low refractive index properties and stain resistance when one or more fluorosilane compounds are mixed and subjected to hydrolysis and condensation reactions.

[0110] (Manufacturing of laminated polyester film)

[0111] A method for manufacturing a laminated polyester film using the easily adhesive polyester film of the present invention will be described, but is not limited to the specific examples described.

[0112] On the aforementioned easily bondable polyester film coating layer, the aforementioned electron beam or ultraviolet-curable acrylic resin, oligomer, monomer, or siloxane-based thermosetting resin is coated. When coating layers are provided on both sides, the coating is applied to at least one coating layer. The coating liquid does not require special dilution, but dilution with an organic solvent is acceptable depending on the viscosity, wettability, and film thickness requirements of the coating liquid. For the coating layer, after applying the aforementioned coating liquid to the aforementioned film and allowing it to dry as needed, the coating layer is cured by electron beam or ultraviolet irradiation and heating, in accordance with the curing conditions of the coating liquid, thereby forming a hard coating layer.

[0113] In this invention, the thickness of the hard coating is preferably 1 to 15 μm. If the thickness of the hard coating is 1 μm or more, it effectively enhances the properties of the hard coating, such as chemical resistance, abrasion resistance, and stain resistance, which is preferable. On the other hand, if the thickness is 15 μm or less, the flexibility of the hard coating can be maintained, eliminating concerns about cracking, which is also preferable.

[0114] Regarding scratch resistance, when the coated surface is abraded with black backing paper, it is preferable that the scratches are not noticeable to the naked eye. If the scratches are not noticeable in the aforementioned evaluation, it is less likely to be scratched when passing through the guide roller, which is preferable from the viewpoint of operability, etc.

[0115] The easily bondable polyester film and laminated polyester film of the present invention are primarily intended for optical applications; therefore, high transparency is preferred. Ideally, the lower limit of haze is 0%, and the closer to 0%, the more preferred. The upper limit of haze is preferably 2%, and if it is below 2%, light transmittance is good, resulting in a clear image in the liquid crystal display device, which is preferable. The haze of the polyester film can be measured, for example, according to the method described later.

[0116] On the easily adhesive coating layer of the easily adhesive polyester film, a coating liquid for forming a hard coating with the above-described composition is suitable for application using a wire rod or similar tool. For example, it can be dried at 70°C for 1 minute to remove the solvent. Next, the film coated with the hard coating is irradiated with a high-pressure mercury lamp at, for example, 300 mJ / cm². 2 Ultraviolet light can be used to obtain laminated polyester films with hard coatings.

[0117] The adhesion between the easily bondable coating layer and the hard coating layer can be obtained by evaluation based on the measurement method described later. Regarding the adhesion X after film formation, 95% or more is preferred. More preferably, 98% or more, and even more preferably 100%. If it is 95% or more, it can be said that the adhesion between the coating layer and the hard coating layer is sufficiently maintained. It should be noted that, in this invention, "after film formation" means that the film is stored continuously at a temperature below 40°C for no more than 6 months from the date of film formation.

[0118] Regarding the adhesion Y between the easily bondable coating layer and the hard coating layer under high temperature and high humidity conditions of 80°C and 95% RH, as evaluated according to the method described later, as mentioned above, the adhesion is preferably 95% or more. More preferably 98% or more, and even more preferably 100%. If it is 95% or more, the adhesion between the easily bondable coating layer and the hard coating layer under high temperature and high humidity conditions can be satisfied in one go, and the passability in subsequent processing steps can be satisfied in one go.

[0119] Ideally, the adhesion of easy-to-adhere polyester films would be evaluated by their adhesion after being placed at room temperature for several weeks to several months. However, since it is difficult to perform placement tests, this application uses a substitute measurement: accelerated evaluation is performed by placing the film at a high temperature and high humidity of 80°C and 90% RH for 24 hours.

[0120] The easily bondable polyester film of the present invention is a film with high sealing reliability, and it also exhibits high sealing performance after being exposed to high temperature and high humidity environments. Therefore, the above X (%) and Y (%) satisfy the following formula (5).

[0121] XY(%)≤5···Equation (5)

[0122] The value of formula (5) is preferably 5% or less. More preferably 2% or less, and even more preferably 0%. If it is 5% or less, the difference between the adhesion after film formation and the adhesion after damp heat treatment is small, and it can be said that the film is sufficiently tight after both film formation and damp heat treatment. This is believed to be related to the characteristic that the adhesion to the hard coating does not decrease even after long-term storage.

[0123] The easily bondable polyester film of the present invention can be used for various applications, preferably in the manufacturing process of polarizing plates used in liquid crystal display devices, and particularly preferably as a protective film for polarizers constituting polarizing plates. Typically, polarizers are mostly made of polyvinyl alcohol, and the easily bondable polyester film of the present invention is bonded to the polarizer using an adhesive made of polyvinyl alcohol with added crosslinking agents, as needed. In this case, the coating layer of the easily bondable polyester film of the present invention is more preferably applied facing the opposite side rather than the side to which it is bonded to the polarizer. On the surface of the easily bondable polyester film of the present invention that is bonded to the polarizer, an easily bondable layer, such as that described in International Publication No. 2012 / 105607, comprising a polyester resin, a polyvinyl alcohol resin, and a crosslinking agent, is preferably laminated.

[0124] Example

[0125] Next, the present invention will be described in detail using examples, comparative examples, and reference examples, but the present invention is not limited to the following examples. Furthermore, the evaluation method used in the present invention is described below.

[0126] (1) Average particle size

[0127] [Measurement method based on scanning electron microscopy]

[0128] The average particle size of the aforementioned particles can be determined by the following method. For each particle, a scanning electron microscope (SEM) is used to take photographs. Using the smallest particle as a magnification of 2–5 mm, the maximum particle size (distance between the two furthest points) of 300–500 particles is measured, and the average value is taken as the average particle size. The average particle size present in the coating layer of this invention can be determined by this method.

[0129] [Dynamic light scattering method]

[0130] The average particle size can also be determined using dynamic light scattering during the fabrication of particles and films. The sol is diluted with a dispersion medium, and the parameters of the dispersion medium are measured using a submicron particle analyzer N4 PLUS (Beckman Coulter). The average particle size is calculated using the cumulative method. In dynamic light scattering, the average particle size of the particles in the sol is observed; when particles aggregate, the average particle size of these aggregated particles is also observed.

[0131] (2) Refractive index of particles

[0132] The refractive index of the particles can be determined by the following method: Inorganic particles are dried at 150°C and then pulverized in a mortar to obtain powder. The powder is then impregnated with solvent 1 (refractive index lower than that of the particles), and solvent 2 (refractive index higher than that of the particles) is added little by little until the particles become essentially transparent. The refractive index of the solution is measured using an Abbe refractometer (manufactured by ATAGO CO., LTD.). The measurement is performed at 23°C under D-rays (wavelength 589 nm). Solvent 1 and solvent 2 are selected to be miscible with each other. Examples of solvents that can be used, based on their refractive index, include 1,1,1,3,3,3-hexafluoro-2-propanol, 2-propanol, chloroform, carbon tetrachloride, toluene, and glycerol.

[0133] (3) Haze of easy-to-adhere polyester film for optical applications

[0134] The haze of the easy-to-adhere polyester film was measured according to JIS K 7136:2000 using a turbidimeter (Nippon Denshoku Corporation, NDH2000).

[0135] (4) Adhesion (adhesion after film formation X)

[0136] In the examples, a hard coating is formed on the easy-to-adhere coating layer of the polyester film. For the easy-to-adhere polyester film with the hard coating formed, the adhesion between the hard coating and the substrate film is determined according to 8.5.1 of JIS-K5400-1990.

[0137] The coating solution used in the formation of the hard coating is prepared as follows.

[0138] (Preparation of coating liquid L for hard coating formation)

[0139] 64.40% by mass of methyl ethyl ketone

[0140] Dipentaerythritol hexaacrylate 27.20% by mass

[0141] (Niinakamura Chemicals A-DPH)

[0142] 3.40% by mass of polyethylene glycol diacrylate

[0143] (Kyoei Chemical Manufacturing Co., Ltd. Light Acrylate 9EG-A)

[0144] Bisphenol A diacrylate 4.00% by mass

[0145] (Kyoei Chemical Manufacturing Co., Ltd. Light Acrylate BP-4PA)

[0146] Photopolymerization initiator 1.00% by mass

[0147] (IGM Resins BV Omnirad184)

[0148] The aromatic content of all resins in the prepared hard coating solution L is 13.3% in molar proportion.

[0149] (Formation of a hard coating)

[0150] The easily bondable polyester film manufactured in the examples described later was stored at 20°C and 65% RH for 12 hours. Then, using a #14 wire rod, a hard coating solution of the above composition was applied to the easily bondable coating layer. The film was dried at 70°C for 1 minute to remove the solvent. Next, the film coated with the hard coating was irradiated with a high-pressure mercury lamp at 300 mJ / cm². 2 Ultraviolet light was used to obtain a hard-coated film with a thickness of 7 μm.

[0151] The specific method for measuring adhesion is as follows. Using a cutting guide with a 2mm gap, 100 grid-like scratches are applied to the hard coating surface, reaching the substrate film. Next, cellophane tape (Nichiban, No. 405; 24mm wide) is adhered to the grid-like scratched surface and rubbed with an eraser to ensure complete adhesion. Then, the cellophane tape is vertically peeled off from the hard coating surface of the aforementioned easy-to-adhere polyester film with the hard coating. The number of grids peeled off from the hard coating surface of the easy-to-adhere polyester film with the hard coating is visually counted, and the adhesion between the hard coating and the substrate film is calculated using the following formula. It should be noted that partially peeled grids are also counted as peeled grids.

[0152] Adhesion (%) = {1 - (number of stripped meshes / 100)} × 100

[0153] (5) Resistance to damp heat (sealing performance after placement at 80℃ and 90%RH: sealing performance after damp heat treatment Y)

[0154] The obtained easily bondable polyester film was placed in a high-temperature, high-humidity bath at 80°C and 90% RH for 24 hours, and then placed at room temperature (20°C and 65% RH) for 12 hours. Afterward, a hard coating was formed using the same method as described above, and the adhesion was determined.

[0155] (6) Adhesion of the hard coating of the easy-to-adhere polyester film roll after 6 months of storage Z

[0156] Rolls of easily bondable polyester film were placed in an environment with a temperature of 0°C to 30°C and a humidity of 10% RH to 80% RH for 6 months. Samples were collected from the film rolls after this period of time, and a hard coating was formed on the easily bondable coating layer in the same manner as above to evaluate the adhesion.

[0157] As for the sealing reliability based on the above-mentioned sealing performance Z, 99% or more is marked as ◎, 95% or more but less than 99% is marked as 〇, and less than 95% is marked as ×. Sealing reliability ◎ and 〇 with the above-mentioned sealing performance Z of 95% or more is marked as qualified.

[0158] (7) Number-average molecular weight

[0159] Dissolve 0.03 g of resin in 10 ml of tetrahydrofuran. Use a GPC-LALLS low-angle light scattering spectrophotometer LS-8000 (manufactured by Tosoh Corporation, tetrahydrofuran solvent, control: polystyrene) at a column temperature of 30°C and a flow rate of 1 ml / min to determine the number-average molecular weight using a column (Showa Denko Corporation, shodex KF-802, 804, 806).

[0160] (8) Cross-sectional observation based on transmission electron microscopy

[0161] The obtained easily bondable polyester film was cut into 1mm × 10mm pieces, embedded in epoxy resin, and then thin sections were prepared using an ultramicrotome, parallel to the short side of the embedded sample. Next, in areas of the film obtained by staining with ruthenium tetroxide and finding no obvious damage, observation was performed using a transmission electron microscope (JEM2100, NEC) at an accelerating voltage of 200kV and magnification of 20000x. The thickness of the coating was measured at 10 points on each horizontal plane from the observed images, and the average value was taken as the coating thickness.

[0162] (9) Surface free energy

[0163] Under conditions of 25°C and 50% RH, droplets of water (1.8 μL) and diiodomethane (0.9 μL) were prepared on the coated surface of an easily bondable polyester film using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.: DM-701 fully automatic contact angle meter), and their contact angles were measured. The contact angles were measured 10 seconds after each liquid was added to the easily bondable polyester film. Based on the Kitasaki-Hatake theory, the contact angle data of water and diiodomethane obtained by the aforementioned method were calculated, and the dispersion component γ of the surface free energy of the easily bondable polyester film was determined. sd Hydrogen bond component γ sh The components are summed up and their values ​​are taken as the surface free energy γ. s In this calculation, the calculation software within the contact angle meter software (FAMAS) was used.

[0164] (10) Evaluation of the nitrogen atom ratio on the surface of the coating layer

[0165] The ratio of the amount of nitrogen atoms to the total amount of all elements in the surface region (nitrogen atom ratio (A)). N :at%)) X-ray photoelectron spectroscopy (ESCA) (K-Alpha manufactured by Thermo Fisher Scientific) + Evaluation. The measurement conditions are shown below. It should be noted that background removal was performed using the Shirley method during analysis. Additionally, A N The calculation is set as the average value of the measurement results from 3 sites.

[0166] Measurement conditions

[0167] Excitation of X-rays: Monochromatic Al Kα rays

[0168] X-ray power: 12kV, 6mA

[0169] Photoelectron extraction angle: 90°

[0170] Dot size:

[0171] Energy: 50eV

[0172] Step size: 0.1eV

[0173] (11) Determination of nitrogen distribution in the depth direction

[0174] The elemental distribution along the depth direction of the coating layer was determined by X-ray photoelectron spectroscopy (ESCA) (K-Alpha, Thermo Fisher Scientific). +The etching process was performed using an Ar cluster, which is expected to cause low damage to organic materials, as an ion source. The sample was rotated during etching to ensure uniform etching. To minimize X-ray-based damage, spectral collection at each etching time was performed in snapshot mode for short-term evaluation. For ease of evaluation, spectral collection was performed as follows: every 30 seconds until the etching time reached 120 seconds, then every 60 seconds until 720 seconds, and then every 120 seconds until 1200 seconds. Details of the measurement conditions are shown below. It should be noted that background removal was performed using the Shirley method during analysis.

[0175] Measurement conditions

[0176] Excitation X-rays: Monochromatic Al Kα lines

[0177] X-ray power: 12kV, 2.5mA

[0178] Photoelectron extraction angle: 90°

[0179] Dot size:

[0180] Energy rating: 150eV (Snapshot mode)

[0181] Accelerating voltage of the ion gun: 6kV

[0182] Cluster size: small

[0183] Etching rate: 15nm / min (converted from polystyrene)※

[0184] Sample rotation during etching:

[0185] The etching rate was calculated using a 155 nm thick film made by dissolving monodisperse polystyrene (Mn: 91000; Mw / Mn = 1.05) in toluene and then spin-coating it onto a silicon wafer.

[0186] Based on this evaluation data, a nitrogen distribution curve was plotted with the etching time from the coating surface as the horizontal axis and the ratio of nitrogen atoms to the total amount of all elements (nitrogen atom ratio) as the vertical axis. An example of the distribution curve is shown below. Figure 1 .

[0187] Figure 1 In the distribution curve shown, the etching time (t1) (seconds) when no significant change is observed (becoming the lower limit) is the maximum value of the nitrogen atom ratio (A). N X: at% and lower limit (A) N The median value of Y: at% (A) NThe etching time (t2) at Z:at%) is taken as a ratio according to the aforementioned formula (4), and thus used as a measure of the amount of segregated components.

[0188] Here, the reading of t1 is determined as follows.

[0189] from Figure 1 Mark three points sequentially from the left end of the horizontal axis, and set their etching times sequentially to t from left to right. 1-1 (seconds), t 1-2 (seconds), t 1-3 (seconds) will be used to determine the etching time (t). 1-1 The nitrogen atom ratio value is set to n1 (at%), and the next etching time (t) is set after 30 seconds, 60 seconds, or 120 seconds. 1-2 The nitrogen atom ratio value is set to n2 (at%), and then the etching time (t) is set after 30 seconds, 60 seconds, or 120 seconds. 1-3 When the nitrogen atom ratio is set to n3 (at%), the difference between the average of these three points (n1, n2, n3) and n1 is used to confirm whether the following relationship (6) is satisfied. This process is repeated until three consecutive points (t of the following three points) are satisfied. 1-1 (seconds) corresponds to the above 1-2 (seconds) will be the first time that relation (6) is satisfied. 1-1 (seconds) is the etching time t1 (seconds).

[0190] |n1-(n1+n2+n3) / 3)|≤0.010(at%)···Equation (6)

[0191] Regarding the lower limit (A) N Y), as the nitrogen atom ratio value at t1 (seconds).

[0192] From this lower limit value, A can be calculated according to the following formula (7). N Z,

[0193] A N Z = (A N XA N Y) / 2···Formula (7)

[0194] Set the etching time at this point to t2 (seconds).

[0195] (Polymerization of copolyester resin (A) for coating layer)

[0196] In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 342.0 parts by weight of dimethyl 2,6-naphthalenedicarboxylate, 35.0 parts by weight of dimethyl terephthalate, 35.5 parts by weight of sodium dimethyl isophthalate-5-sulfonate, 198.6 parts by weight of ethylene glycol, 118.2 parts by weight of 1,6-hexanediol, and 0.4 parts by weight of tetrabutyl titanate were added. The transesterification reaction was carried out at 160°C to 220°C for 4 hours. Then, 60.7 parts by weight of sebacic acid were added to initiate an esterification reaction. Next, the temperature was raised to 255°C, and the reaction system was slowly reduced under reduced pressure. The reaction was then carried out under reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain copolyester resin (A). The obtained copolyester resin (A) was pale yellow and transparent. The specific viscosity of copolyester resin (A) was measured to be 0.72 dl / g. The glass transition temperature based on DSC is 40℃ and the number-average molecular weight is 20,000.

[0197] (Polymerization of copolyester resin (B) for coating layer)

[0198] In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 293.0 parts by weight of dimethyl 2,6-naphthalenedicarboxylate, 128.0 parts by weight of dimethyl terephthalate, 41.6 parts by weight of sodium dimethyl isophthalate-5-sulfonate, 125.0 parts by weight of ethylene glycol, 105.0 parts by weight of diethylene glycol, 142.0 parts by weight of 1,6-hexanediol, and 0.4 parts by weight of tetrabutyl titanate were added. The transesterification reaction was carried out at 160°C to 220°C for 4 hours. Then, the temperature was raised to 255°C, and the reaction system was slowly reduced in pressure, followed by reaction under reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain copolyester resin (B). The obtained copolyester resin (B) was pale yellow and transparent. The specific viscosity of the copolyester resin (B) was measured to be 0.69 dl / g. The glass transition temperature based on DSC is 30℃ and the number-average molecular weight is 21000.

[0199] (Polymerization of copolyester resin (C) for coating layer)

[0200] In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 145.6 parts by weight of dimethyl terephthalate, 14.8 parts by weight of sodium dimethyl isophthalate-5-sulfonate, 43.3 parts by weight of dimethyl azelate, 80.7 parts by weight of ethylene glycol, 131.6 parts by weight of 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene, 70.9 parts by weight of 3-methyl-1,5-pentanediol, and 0.4 parts by weight of tetrabutyl titanate were added. The transesterification reaction was carried out at 160°C to 220°C for 4 hours. Then, the temperature was raised to 255°C, and the reaction system was slowly reduced in pressure, followed by reaction under reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain copolyester resin (C). The obtained copolyester resin (C) was pale yellow and transparent. The specific viscosity of the copolyester resin (C) was measured and found to be 0.65 dl / g. The glass transition temperature based on DSC is 40℃ and the number-average molecular weight is 19000.

[0201] (Polymerization of copolyester resin (D) for coating layer)

[0202] The copolymerized resin (D) was obtained by polymerizing resin (A) with 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. The specific viscosity of the obtained copolymerized resin (D) was measured to be 0.70 dl / g. The glass transition temperature based on DSC was 40 °C.

[0203] (Preparation of polyester aqueous dispersions (Aw), (Bw), (Cw), (Dw))

[0204] In a reactor equipped with a stirrer, thermometer, and reflux device, 30 parts by weight of copolyester resin (A) and 15 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, 55 parts by weight of water were slowly added to the polyester solution while stirring. After addition, the solution was stirred and cooled to room temperature to prepare a milky white aqueous dispersion Aw (resin A solution) of polyester resin (A) with a solid content of 25.0% by weight.

[0205] In the same manner, an aqueous dispersion of polyester resin (B) Bw (resin B solution) containing copolyester resin (B) was prepared.

[0206] In the same way, an aqueous dispersion of polyester resin (C) Cw (resin C solution) containing copolyester resin (C) was prepared.

[0207] In the same way, an aqueous dispersion Dw (resin D solution) of polyester resin (D) containing copolyester resin (D) was prepared.

[0208] (Manufacturing of polyurethane aqueous dispersion (E))

[0209] Polymerization of water-dispersible polyurethane resins with aliphatic polycarbonate polyols as constituent components

[0210] In a four-necked flask equipped with a stirrer, a serpentine condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 43.75 parts by weight of 4,4'-diphenylmethane diisocyanate, 12.85 parts by weight of dimethylolbutyric acid, 153.41 parts by weight of polyhexamethylene carbonate diol with a number average molecular weight of 2000, 0.03 parts by weight of dibutyltin dilaurate, and 84.00 parts by weight of acetone as a 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 specified amine equivalent. Next, the reaction solution was cooled to 40°C, and 8.77 parts by weight of triethylamine were added to obtain a polyurethane prepolymer solution. Then, in a reaction vessel equipped with a high-speed homogenizer, 450 g of water was added, the temperature was adjusted to 25°C, and the mixture was stirred at a high speed for 2000 min. -1 A polyurethane prepolymer solution was added for water dispersion while stirring and mixing. Then, under reduced pressure, a portion of the acetone and water was removed to prepare a water-soluble polyurethane resin solution (resin E solution) with a solid content of 37% by mass. The resulting polyurethane resin had a glass transition temperature of -30°C.

[0211] (Synthesis of crosslinking agent P)

[0212] In a flask equipped with a stirrer, thermometer, and reflux condenser, 100 parts by mass of a polyisocyanate compound (NCO concentration 23.1%) with an isocyanurate structure prepared from 1,6-hexamethylene diisocyanate according to existing methods, and 17.5 parts by mass of N-methylpyrrolidone, 35.00 parts by mass of 3,5-dimethylpyrazole were added dropwise. The mixture was kept at 70°C for 1 hour under a nitrogen atmosphere. Then, 12.50 parts by mass of dimethylolpropionic acid were added dropwise. After confirming the disappearance of the isocyanate group absorption by measuring the infrared spectrum of the reaction solution, 8.72 parts by mass of N,N-dimethylethanolamine were added. After stirring for 1 hour under this condition, an appropriate amount of water was added to obtain an aqueous dispersion of end-capped isocyanate with a solid content of 40% by mass (crosslinking agent P solution).

[0213] (Synthesis of crosslinking agent Q)

[0214] In a flask equipped with a stirrer, thermometer, and reflux condenser, 35.00 parts by weight of 3,5-dimethylpyrazole were added dropwise to 100 parts by weight of a polyisocyanate compound (NCO concentration 23.3%) with an isocyanurate structure prepared from cyclohexane diisocyanate according to existing methods and 17.5 parts by weight of N-methylpyrrolidone. The mixture was kept at 70°C for 1 hour under a nitrogen atmosphere.

[0215] Next, 12.50 parts by weight of dimethylolpropionic acid were added dropwise. The infrared spectrum of the reaction solution was measured, and after confirming the disappearance of the isocyanate group absorption, 8.72 parts by weight of N,N-dimethylethanolamine were added. After stirring for 1 hour under these conditions, an appropriate amount of water was added to obtain a 40% by weight end-capped isocyanate-based aqueous dispersion (crosslinking agent Q solution).

[0216] (Synthesis of crosslinking agent R)

[0217] In a flask equipped with a stirrer, thermometer, and reflux condenser, 35.00 parts by weight of 3,5-dimethylpyrazole were added dropwise to 100 parts by weight of a polyisocyanate compound (NCO concentration 23.1%) prepared from 2,5-diisocyanate thiophene with an isocyanurate structure and 17.5 parts by weight of N-methylpyrrolidone, and the mixture was kept at 70°C for 1 hour under a nitrogen atmosphere.

[0218] Next, 12.50 parts by weight of dimethylolpropionic acid were added dropwise. The infrared spectrum of the reaction solution was measured, and after confirming the disappearance of the isocyanate group absorption, 8.72 parts by weight of N,N-dimethylethanolamine were added. After stirring for 1 hour under these conditions, an appropriate amount of water was added to obtain a 40% by weight end-capped isocyanate-based aqueous dispersion (crosslinking agent R solution).

[0219] (Synthesis of crosslinking agent S)

[0220] In a flask equipped with a stirrer, thermometer, and reflux condenser, 168 parts by mass of hexamethylene diisocyanate and 220 parts by mass of polyethylene glycol monomethyl ether (average molecular weight 400) were added. The mixture was stirred at 120°C for 1 hour. Then, 26 parts by mass of 4,4'-dicyclohexylmethane diisocyanate and 3.8 parts by mass of 3-methyl-1-phenyl-2-phosphine-1-oxide (2% by mass relative to the total isocyanate) were added as a carbodiimide catalyst. The mixture was stirred at 185°C for 5 hours under a nitrogen atmosphere. The infrared spectrum of the reaction solution was measured, confirming the disappearance of the isocyanate group absorption. After natural cooling to 60°C, 567 parts by mass of deionized water were added to obtain a carbodiimide-based crosslinking agent with a solid content of 40% by mass (crosslinking agent S solution).

[0221] (Synthesis of crosslinking agent T)

[0222] In a flask equipped with a stirrer, thermometer, and reflux condenser, 35.00 parts by weight of 3,5-dimethylpyrazole were added dropwise to 100 parts by weight of a polyisocyanate compound (NCO concentration 22.3%) with an isocyanurate structure prepared from 2,4-toluene diisocyanate according to existing methods and 17.5 parts by weight of N-methylpyrrolidone. The mixture was kept at 70°C for 1 hour under a nitrogen atmosphere.

[0223] Next, 12.50 parts by weight of dimethylolpropionic acid were added dropwise. The infrared spectrum of the reaction solution was measured, and after confirming the disappearance of the isocyanate group absorption, 8.72 parts by weight of N,N-dimethylethanolamine were added. After stirring for 1 hour under these conditions, an appropriate amount of water was added to obtain a 40% by weight end-capped isocyanate-based aqueous dispersion (crosslinking agent T solution).

[0224] (Zirconium oxide particles)

[0225] In a 3-liter glass container, 2283.6 g of pure water and 403.4 g of oxalic acid dihydrate were added and heated to 40°C to prepare a 10.72% by mass oxalic acid aqueous solution. While stirring the aqueous solution, 495.8 g of zirconium oxycarbonate powder (ZrOCO3, manufactured by AMR International Corp., equivalent to 39.76% by mass ZrO2) was slowly added. After mixing for 30 minutes, the mixture was heated at 90°C for 30 minutes. Then, 1747.2 g of a 25.0% by mass tetramethylammonium hydroxide aqueous solution (manufactured by Tama Chemical Industry Co., Ltd.) was slowly added over 1 hour. At this point, the mixture was in slurry form, containing 4.0% by mass ZrO2. The slurry was transferred to a stainless steel autoclave and hydrothermally treated at 145°C for 5 hours. The product after hydrothermal treatment was free of undissolved matter and completely gelled. The obtained sol contained 4.0% by mass of ZrO2, had a pH of 6.8, and an average particle size of 19 nm based on dynamic light scattering. Furthermore, the transmittance of the sol was measured to be 88% when the ZrO2 concentration was adjusted to 2.0% by mass with pure water. Particle observation using a transmission electron microscope showed that the particles were essentially aggregates of primary ZrO2 particles around 7 nm in size. 4000 g of the zirconia sol with a ZrO2 concentration of 4.0% by mass obtained through the above hydrothermal treatment was washed and concentrated using an ultrafiltration device with the slow addition of pure water, yielding 953 g of zirconia sol with a ZrO2 concentration of 13.1% by mass, a pH of 4.9, and a transmittance of 76% at a ZrO2 concentration of 13.1% by mass. The refractive index of the obtained zirconia-based microparticles was 1.75.

[0226] (Zirconium oxide sol)

[0227] After adding 300g of zirconia sol with a ZrO2 concentration of 13.1% by mass to 3.93g of 20% by mass citric acid aqueous solution and 11.0g of 25% by mass tetramethylammonium hydroxide aqueous solution, the solution was further concentrated using an ultrafiltration device, resulting in 129g of a high-concentration zirconia sol with a ZrO2 concentration of 30.5% by mass. This high-concentration zirconia sol had a pH of 9.3 and an average particle size of 19nm obtained based on dynamic light scattering. Furthermore, this zirconia sol exhibited no sedimentation and remained stable for more than one month at 50°C.

[0228] (Titanium dioxide particles)

[0229] A white slurry with pH 9.5 was prepared by mixing 12.09 kg of an aqueous solution of titanium tetrachloride (manufactured by Osaka Titanium Technologies Co., Ltd.) containing 7.75% by mass of titanium tetrachloride (constituted by Osaka Titanium Technologies Co., Ltd.) based on TiO2 conversion, and 4.69 kg of ammonia water (manufactured by Ube Industries Co., Ltd.) containing 15% by mass of ammonia. The slurry was then filtered and washed with pure water to obtain 9.87 kg of a hydrated titanate filter cake containing 10% by mass of solids. Next, 11.28 kg of hydrogen peroxide water (manufactured by Mitsubishi Gas Chemical Co., Ltd.) containing 35% by mass of hydrogen peroxide and 20.00 kg of pure water were added to the filter cake. The mixture was heated at 80°C with stirring for 1 hour, and then 57.52 kg of pure water was added to obtain 98.67 kg of an aqueous solution of titanate containing 1% by mass of titanate peroxide based on TiO2 conversion. The aqueous solution of this titanic acid peroxide is a transparent yellowish-brown color with a pH of 8.5.

[0230] Next, 4.70 kg of cation exchange resin (manufactured by Mitsubishi Chemical Corporation) was mixed into 98.67 kg of the aforementioned titanic acid aqueous solution. Then, 12.33 kg of a potassium stannate aqueous solution containing 1% by mass of potassium stannate (manufactured by Showa Chemical Corporation) based on SnO2 was slowly added to the solution while stirring. After separating the cation exchange resin containing potassium ions, etc., it was placed in an autoclave (manufactured by Pressure Glass Industry Co., Ltd., 120L) and heated at 165°C for 18 hours.

[0231] (Titanium dioxide sol)

[0232] Next, the obtained mixed aqueous solution was cooled to room temperature and concentrated using an ultrafiltration membrane device (Asahi Kasei Corporation, ACV-3010) to obtain 9.90 kg of an aqueous dispersion sol containing titanium-based microparticles (hereinafter referred to as "P-1") with a solid content of 10% by mass. The solids contained in the sol thus obtained were determined using the above method, and the results showed that the solids were titanium-based microparticles (primary particles) with a rutile crystal structure, formed from a composite oxide containing titanium and tin. Furthermore, the content of the metal components contained in these titanium-based microparticles was determined, and the results, on an oxide conversion basis, were as follows: TiO2 87.2% by mass, SnO2 11.0% by mass, and K2O 1.8% by mass. In addition, the pH of the mixed aqueous solution was 10.0. Furthermore, the aqueous dispersion sol containing the aforementioned titanium-based microparticles was a transparent milky white, and the average particle size of the aforementioned titanium-based microparticles contained in the aqueous dispersion sol was 35 nm, with a distribution frequency of coarse particles having a particle size of 100 nm or more of 0%. Furthermore, the refractive index of the obtained titanium-based microparticles is 2.42.

[0233] (Zirconium oxide / titanium dioxide mixed sol)

[0234] The zirconium oxide particles and titanium dioxide particles obtained above are mixed in their respective ratios to prepare a zirconium oxide / titanium dioxide mixed sol with a solid content concentration of 13% by mass.

[0235] (Example 1)

[0236] (Adjustment of coating solution)

[0237] Adjust the coating solution according to the following composition.

[0238] 36.47 parts by weight of water

[0239] 37.42 parts by weight of isopropanol

[0240] 1.21 parts by weight of silica sol

[0241] (Silica sol with an average particle size of 40 nm and a solid content concentration of 40% by mass)

[0242] 1.11 parts by weight of silica sol

[0243] (Silica sol with an average particle size of 450 nm and a solid content concentration of 4% by mass)

[0244] 20.06 parts by weight of resin A solution

[0245] (Solid component concentration 25% by mass)

[0246] 3.14 parts by weight of crosslinking agent P solution

[0247] (Solid component concentration 40% by mass)

[0248] 0.25 parts by weight of surfactant

[0249] (Fluorine-based, solid content 10% by mass)

[0250] 0.34 parts by weight of high-boiling-point solvent

[0251] (Manufacturing of easy-to-adhere polyester film)

[0252] As a polymer for film production, PET resin granules with an intrinsic viscosity (solvent: phenol / tetrachloroethane = 60 / 40) of 0.62 dl / g and substantially free of particles were dried at 135°C for 6 hours under reduced pressure of 133 Pa. Afterward, the granules were fed to an extruder and melt-extruded into sheets at approximately 280°C. These sheets were then rapidly cooled and solidified on rotating cooling metal rollers with a surface temperature maintained at 20°C to obtain unstretched PET sheets.

[0253] The unstretched PET sheet was heated to 100°C using a heated roller assembly and an infrared heater. Then, it was stretched 3.5 times along its length using a roller assembly with a circumferential speed difference to obtain a uniaxially stretched PET film.

[0254] Then, the above coating solution is applied to one side of the PET film using a roller coating method, and dried at 80°C, with the final coating weight after stretching and drying being 0.12 g / m. 2 The film is then adjusted in the following manner. Next, in a tenter frame, it is stretched to 4.0 times its original length in the width direction at 150°C. With the width direction length of the film fixed, it is heated to 230°C and further relaxed in the width direction at 230°C. The resulting film roll is then wound into a 38μm thick, easily bondable polyester film.

[0255] The thickness of the adhesive coating layer of the obtained adhesive polyester film is 80 nm, and the surface free energy is 46.3 mN / m.

[0256] Next, the nitrogen atom ratio of the ESCA-based surface became 8.6 at%, and the distribution curve of the nitrogen atom ratio in the depth direction based on surface etching became... Figure 2 The results show that t1 and t2 are t1 = 111 (seconds) and t2 = 65 (seconds) respectively, and the value obtained from equation (4) is (t2 / t1) × 100 = 59 (seconds).

[0257] Next, on the easy-to-adhere coating layer of the easy-to-adhere polyester film, the above-mentioned hard coating forming liquid L is used to form a laminated polyester film according to the above-described forming method.

[0258] The adhesion of the hard coating of the obtained laminated polyester film was evaluated, and the adhesion force X was found to be 100%.

[0259] The obtained easy-to-adhere polyester film was then placed in a high-temperature and high-humidity bath at 80°C and 90% RH for 24 hours, followed by 12 hours at room temperature. Afterward, a hard coating was formed on the easy-to-adhere coating layer of the treated easy-to-adhere polyester film using a hard coating forming liquid L, resulting in a laminated polyester film.

[0260] The adhesion of the hard coating of the obtained laminated polyester film was evaluated, and the adhesion force Y was found to be 100%.

[0261] As a result, according to equation (5), XY = 0 (%). These results are recorded in Table 1.

[0262] The film rolls of the above-mentioned easy-to-adhere polyester film were placed in an environment with a temperature of 0℃~30℃ and a humidity of 10%RH~80%RH for 6 months. Samples were collected from the film rolls after the placement, and a hard coating was formed on the easy-to-adhere coating layer in the same manner as above. The adhesion Z was evaluated and recorded in Table 1.

[0263] The evaluation results are as follows: the above-mentioned tightness Z is 100%, the tightness reliability is ◎, and the tightness reliability is preferred.

[0264] (Examples 2-3)

[0265] The thickness of the coated resin layer was adjusted as described in Table 1. Otherwise, similar to Example 1, an easily bondable polyester film was obtained. The results are shown in Table 1.

[0266] (Example 4)

[0267] By adjusting the coating liquid with the following composition, an easy-to-adhere polyester film is obtained in the same manner as in Example 1.

[0268] 35.62 parts by weight of water

[0269] 37.42 parts by weight of isopropanol

[0270] 1.21 parts by weight of silica sol

[0271] (Silica sol with an average particle size of 40 nm and a solid content concentration of 40% by mass)

[0272] 1.11 parts by weight of silica sol

[0273] (Silica sol with an average particle size of 450 nm and a solid content concentration of 4% by mass)

[0274] 22.32 parts by weight of resin A solution

[0275] (Solid component concentration 25% by mass)

[0276] 1.72 parts by weight of crosslinking agent P solution

[0277] (Solid component concentration 40% by mass)

[0278] 0.25 parts by weight of surfactant

[0279] (Fluorine-based, solid content 10% by mass)

[0280] 0.34 parts by weight of high-boiling-point solvent

[0281] The evaluation of the obtained easy-to-adhere polyester film was carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0282] (Example 5)

[0283] By adjusting the coating liquid with the following composition, an easy-to-adhere polyester film is obtained in the same manner as in Example 1.

[0284] 37.41 parts by weight of water

[0285] 37.42 parts by weight of isopropanol

[0286] 1.21 parts by weight of silica sol

[0287] (Silica sol with an average particle size of 40 nm and a solid content concentration of 40% by mass)

[0288] 1.11 parts by weight of silica sol

[0289] (Silica sol with an average particle size of 450 nm and a solid content concentration of 4% by mass)

[0290] 17.56 parts by weight of resin A solution

[0291] (Solid component concentration 25% by mass)

[0292] 4.70 parts by weight of crosslinking agent P solution

[0293] (Solid component concentration 40% by mass)

[0294] 0.25 parts by weight of surfactant

[0295] (Fluorine-based, solid content 10% by mass)

[0296] 0.34 parts by weight of high-boiling-point solvent

[0297] The evaluation of the obtained easy-to-adhere polyester film was carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0298] (Example 6)

[0299] The coating solution was adjusted using a crosslinking agent Q solution, and otherwise, an easy-to-adhere polyester film was obtained in the same manner as in Example 1. The evaluation of the obtained easy-to-adhere polyester film was carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0300] (Example 7)

[0301] The coating solution was adjusted using a crosslinking agent R solution, and otherwise, an easy-to-adhere polyester film was obtained in the same manner as in Example 1. The evaluation of the obtained easy-to-adhere polyester film was carried out in the same manner as in Example 1, and the results are described in Table 1.

[0302] (Example 8)

[0303] The coating solution was adjusted using a crosslinking agent S solution, and otherwise, an easy-to-adhere polyester film was obtained in the same manner as in Example 1. The evaluation of the obtained easy-to-adhere polyester film was carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0304] (Example 9)

[0305] The coating solution was adjusted using resin B solution, and otherwise, an easy-to-adhere polyester film was obtained in the same manner as in Example 1. The evaluation of the obtained easy-to-adhere polyester film was carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0306] (Example 10)

[0307] The coating solution was adjusted using resin C solution, and otherwise, an easy-to-adhere polyester film was obtained in the same manner as in Example 1. The evaluation of the obtained easy-to-adhere polyester film was carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0308] (Example 11)

[0309] By adjusting the coating liquid with the following composition, an easy-to-adhere polyester film is obtained in the same manner as in Example 1.

[0310] 36.47 parts by weight of water

[0311] 37.42 parts by weight of isopropanol

[0312] 1.21 parts by weight of zirconium oxide sol

[0313] 1.11 parts by weight of silica sol

[0314] (Silica sol with an average particle size of 450 nm and a solid content concentration of 4% by mass)

[0315] 20.06 parts by weight of resin A solution

[0316] (Solid component concentration 25% by mass)

[0317] 3.14 parts by weight of crosslinking agent P solution

[0318] (Solid component concentration 40% by mass)

[0319] 0.25 parts by weight of surfactant

[0320] (Fluorine-based, solid content 10% by mass)

[0321] 0.34 parts by weight of high-boiling-point solvent

[0322] The evaluation of the obtained easy-to-adhere polyester film was carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0323] (Example 12)

[0324] By adjusting the coating liquid with the following composition, an easy-to-adhere polyester film is obtained in the same manner as in Example 1.

[0325] 36.47 parts by weight of water

[0326] 37.42 parts by weight of isopropanol

[0327] 1.21 parts by weight of titanium dioxide sol

[0328] 1.11 parts by weight of silica sol

[0329] (Silica sol with an average particle size of 450 nm and a solid content concentration of 4% by mass)

[0330] 20.06 parts by weight of resin A solution

[0331] (Solid component concentration 25% by mass)

[0332] 3.14 parts by weight of crosslinking agent P solution

[0333] (Solid component concentration 40% by mass)

[0334] 0.25 parts by weight of surfactant

[0335] (Fluorine-based, solid content 10% by mass)

[0336] 0.34 parts by weight of high-boiling-point solvent

[0337] The evaluation of the obtained easy-to-adhere polyester film was carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0338] (Example 13)

[0339] By adjusting the coating liquid with the following composition, an easy-to-adhere polyester film is obtained in the same manner as in Example 1.

[0340] 36.47 parts by weight of water

[0341] 37.42 parts by weight of isopropanol

[0342] 1.21 parts by weight of zirconium oxide / titanium dioxide mixed sol

[0343] (75% by mass of zirconium oxide relative to the total mass of zirconium oxide / titanium dioxide)

[0344] Solid component concentration 13% by mass

[0345] 1.11 parts by weight of silica sol

[0346] (Silica sol with an average particle size of 450 nm and a solid content concentration of 4% by mass)

[0347] 20.06 parts by weight of resin A solution

[0348] (Solid component concentration 25% by mass)

[0349] 3.14 parts by weight of crosslinking agent P solution

[0350] (Solid component concentration 40% by mass)

[0351] 0.25 parts by weight of surfactant

[0352] (Fluorine-based, solid content 10% by mass)

[0353] 0.34 parts by weight of high-boiling-point solvent

[0354] The evaluation of the obtained easy-to-adhere polyester film was carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0355] (Comparative Examples 1-2)

[0356] The thickness of the coated resin layer was adjusted as described in Table 1. Otherwise, similar to Example 1, an easily bondable polyester film was obtained. The results are shown in Table 1.

[0357] (Comparative Example 3)

[0358] By adjusting the coating liquid with the following composition, an easy-to-adhere polyester film is obtained in the same manner as in Example 1.

[0359] 38.63 parts by weight of water

[0360] 37.42 parts by weight of isopropanol

[0361] 1.21 parts by weight of silica sol

[0362] (Silica sol with an average particle size of 40 nm and a solid content concentration of 40% by mass)

[0363] 1.11 parts by weight of silica sol

[0364] (Silica sol with an average particle size of 450 nm and a solid content concentration of 4% by mass)

[0365] 14.30 parts by weight of resin A solution

[0366] (Solid component concentration 25% by mass)

[0367] Crosslinking agent P solution 6.74 parts by weight

[0368] (Solid component concentration 40% by mass)

[0369] 0.25 parts by weight of surfactant

[0370] (Fluorine-based, solid content 10% by mass)

[0371] 0.34 parts by weight of high-boiling-point solvent

[0372] The evaluation of the obtained easy-to-adhere polyester film was carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0373] (Comparative Example 4)

[0374] By adjusting the coating liquid with the following composition, an easy-to-adhere polyester film is obtained in the same manner as in Example 1.

[0375] 35.06 parts by weight of water

[0376] 37.42 parts by weight of isopropanol

[0377] 1.21 parts by weight of silica sol

[0378] (Silica sol with an average particle size of 40 nm and a solid content concentration of 40% by mass)

[0379] 1.11 parts by weight of silica sol

[0380] (Silica sol with an average particle size of 450 nm and a solid content concentration of 4% by mass)

[0381] 23.83 parts by weight of resin A solution

[0382] (Solid component concentration 25% by mass)

[0383] 0.78 parts by weight of crosslinking agent P solution

[0384] (Solid component concentration 40% by mass)

[0385] 0.25 parts by weight of surfactant

[0386] (Fluorine-based, solid content 10% by mass)

[0387] 0.34 parts by weight of high-boiling-point solvent

[0388] The evaluation of the obtained easy-to-adhere polyester film was carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0389] (Comparative Example 5)

[0390] The coating solution was adjusted using resin D solution, and otherwise, an easy-to-adhere polyester film was obtained in the same manner as in Example 1. The evaluation of the obtained easy-to-adhere polyester film was carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0391] (Comparative Example 6)

[0392] By adjusting the coating liquid with the following composition, an easy-to-adhere polyester film is obtained in the same manner as in Example 1.

[0393] 36.80 parts by weight of water

[0394] 37.29 parts by weight of isopropanol

[0395] 1.33 parts by weight of silica sol

[0396] (Silica sol with an average particle size of 40 nm and a solid content concentration of 40% by mass)

[0397] 1.23 parts by weight of silica sol

[0398] (Silica sol with an average particle size of 450 nm and a solid content concentration of 4% by mass)

[0399] 13.31 parts by weight of resin A solution

[0400] (Solid component concentration 25% by mass)

[0401] 5.99 parts by weight of resin E solution

[0402] (Solid component concentration 37% by mass)

[0403] Crosslinking agent P solution 3.47 parts by weight

[0404] (Solid component concentration 40% by mass)

[0405] 0.25 parts by weight of surfactant

[0406] (Fluorine-based, solid content 10% by mass)

[0407] 0.34 parts by weight of high-boiling-point solvent

[0408] The evaluation of the obtained easy-to-adhere polyester film was carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0409] (Comparative Example 7)

[0410] The coating solution was adjusted using crosslinking agent T solution, and otherwise, an easy-to-adhere polyester film was obtained in the same manner as in Example 1. The evaluation of the obtained easy-to-adhere polyester film was carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0411] [Table 1]

[0412]

[0413] Industrial availability

[0414] According to the present invention, an easy-to-adhere polyester film can be provided that ensures reliable sealing after long-term placement in high temperature and high humidity environments, making it easier to apply for optical purposes and the like.

[0415] Explanation of reference numerals in the attached figures

[0416] A N X: Maximum nitrogen atom ratio (at%)

[0417] A N Y: Lower limit of nitrogen atom ratio (at%)

[0418] A N Z: At position A N X and A N The median (at%) of the nitrogen atom ratio in Y.

[0419] t1: Etching time (seconds) when the nitrogen atom ratio reaches the lower limit.

[0420] t2: corresponds to A N Etching time of Z (seconds)

[0421] t 1-1 t 1-2 t 1-3 Etching time (in seconds) for three consecutive points.

Claims

1. An easily bondable polyester film having a coating layer on at least one side of the polyester film, said coating layer being formed by curing a composition comprising a polyester having a polycyclic aromatic backbone and a crosslinking agent having at least one backbone selected from aliphatic, alicyclic, and heterocyclic groups, the coating layer comprising zirconium oxide particles. The thickness (d: nm) of the coating layer satisfies the following formula (1). The surface free energy (γs: mN / m) of the coating layer surface that is not in contact with the polyester film satisfies the following equation (2). The nitrogen atom ratio (A) on the surface of the coating layer based on X-ray photoelectron spectroscopy (ESCA) N :at%) satisfies the following formula (3). In the nitrogen distribution curve determined based on depth-direction elemental distribution, the ratio of time t2 (seconds) to time t1 (seconds) (t2 / t1) satisfies the following equation (4), where time t1 is the lower limit value of the nitrogen atom ratio (A). N The time t2 (Y: at%) is the time when the nitrogen atom ratio reaches its maximum value (A). N X: at% and the A N The median value of Y (A) N Z: at% time, 30 ≤ d ≤ 200 ・・・Equation (1) 43 ≤ γs ≤ 49 ・・・Equation (2) 3.0 ≤ A N ≤ 9.5 ・・・Equation (3) (t2 / t1)×100 ≥ 40 ・・・Equation (4).

2. The easily adhesive polyester film according to claim 1, wherein, When a hard coating layer is applied to the coating layer after film formation, the adhesion X (%) is above 95%. The adhesion X and the adhesion Y (%) after being placed in an environment of 80°C and 90%RH for 24 hours and then having a hard coating layer applied to the coating layer satisfy the following formula (5). X - Y (%) ≤ 5・・・Formula (5).

3. The easily bondable polyester film according to claim 1 or 2, wherein, The polyester having a polycyclic aromatic backbone is a polyester having a naphthalene backbone.

4. The easily bondable polyester film according to claim 1 or 2, wherein, The crosslinking agent having at least one backbone selected from aliphatic, alicyclic, and heterocyclic groups is an isocyanate crosslinking agent or a carbodiimide crosslinking agent having at least one backbone selected from aliphatic, alicyclic, and heterocyclic groups.

5. The easily bondable polyester film according to claim 1 or 2, wherein, The crosslinking agent having at least one backbone selected from aliphatic, alicyclic, and heterocyclic groups is an isocyanate crosslinking agent having at least one backbone selected from aliphatic, alicyclic, and heterocyclic groups.

6. The easily bondable polyester film according to claim 5, wherein, The composition does not contain isocyanates having an aromatic backbone.

7. The easily bondable polyester film according to claim 5, wherein, The isocyanate crosslinking agent is a capped isocyanate-based crosslinking agent.

8. The easily bondable polyester film according to claim 1 or 2, wherein, Of the total solid components of the resin and crosslinking agent contained in the composition, there are 10% by mass and 90% by mass of the polyester.

9. The easily bondable polyester film according to claim 1 or 2, wherein, Of the total solid components of the resin and crosslinking agent contained in the composition, the crosslinking agent comprises 5% by mass and less than 50% by mass.

10. The easily bondable polyester film according to claim 1 or 2, wherein, The adhesive resin constituting the coating layer does not contain polyurethane resin.

11. The easily bondable polyester film according to claim 1 or 2, wherein, The coating layer contains particles with an average particle size of 0.04 to 2.0 μm, and the particle concentration in the coating layer is 1 to 20% by mass relative to the resin composition.

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