Polyester film

Abstract

The present invention provides a layered polyester film comprising: an easily adhesive polyester film which, during film formation or post-processing such as application of a functional layer, does not damage an opposite surface that is in contact with a coating layer or the functional layer; and said functional layer.　An easily adhesive polyester film according to the present invention has a polyester film substrate and a coating layer on at least one surface thereof. The coating layer is formed from a composition containing a polycarbonate polyurethane resin (A), a polyester resin (B), a blocked isocyanate-based crosslinking agent (C), and particles. In a particle drop-off test, the particle drop-off amount in an observation field is less than 30%.

Description

Polyester film

[0001] The present invention provides a highly adhesive polyester film and a laminated polyester film equipped with the functional layer, which do not damage the surface opposite to the surface that comes into contact with the coating layer or the functional layer formed on the opposite surface during film formation and post-processing such as the addition of a functional layer.

[0002] Hard coat films having a transparent hard coat layer laminated thereon are used on the front surfaces of displays such as touch panels, computers, televisions, and liquid crystal display devices, as well as decorative materials, etc. Panel members used in displays are formed by laminating a hard coat film with a polarizer or with other members, and the lamination is carried out by applying an adhesive component.

[0003] A transparent polyester film is generally used as the transparent plastic film substrate, and in order to improve the adhesion between the polyester film substrate and the hard coat layer and adhesive, a coating layer having high adhesive properties is often provided on the surface of the polyester film as an intermediate layer between them.

[0004] The hard coat film is required to have durability against temperature, humidity, light, etc., transparency, chemical resistance, scratch resistance, stain resistance, etc. Furthermore, since it is often used on the surface of a display or decorative material, visibility or design is required. Therefore, in order to suppress glare and iridescent colors caused by reflected light when viewed from any angle, it is common to provide an antireflection layer with a multilayer structure in which a high refractive index layer and a low refractive index layer are alternately laminated on top of the hard coat layer.

[0005] In recent years, hard coat layers with various compositions have been developed, and the adhesion between the substrate and the hard coat layer has been discussed depending on the composition. For example, when a film laminated with a hard coat layer is used in a liquid crystal television display, not only initial adhesion immediately after lamination but also performance such as resistance to humidity and heat and adhesion retention over time are required to ensure high reliability for long-term use.

[0006] The same is true for the adhesives, which are required to have durability against temperature, humidity, light, etc., transparency, chemical resistance, scratch resistance, stain resistance, etc. Furthermore, since they are often used on the surfaces of displays and decorative materials, visibility or design is also required. In recent years, adhesives with various compositions have been developed, and the adhesion between the substrate and the adhesive has been discussed depending on the composition. For example, when members bonded together with an adhesive are used in a liquid crystal television display, in order to ensure high reliability for long-term use, not only initial adhesion immediately after lamination but also performance such as resistance to humidity and heat and adhesion retention over time are required.

[0007] Due to its image formation method, liquid crystal display devices have polarizing plates disposed on both sides of glass substrates that form the liquid crystal panel surface. Polarizing plates generally have a structure in which polarizer protective films are bonded to both sides of a polarizer made of a polyvinyl alcohol-based film and a dichroic material such as iodine via a hydrophilic adhesive such as a polyvinyl alcohol-based resin. Triacetyl cellulose films have traditionally been used as protective films for protecting polarizers because of their optical properties and transparency.

[0008] However, triacetyl cellulose does not have sufficient durability, and when a polarizing plate using a triacetyl cellulose film as a polarizer protective film is used under high temperature or high humidity conditions, the performance of the polarizing plate, such as the polarization degree and hue, may deteriorate. Furthermore, in recent years, there has been a demand for thinner polarizing plates to accommodate thinner displays, but there has been a limit to how thin a triacetyl cellulose film can be made from the viewpoint of maintaining moisture barrier properties. Therefore, it has been proposed to use a polyester film as a polarizer protective film having durability and moisture barrier properties (see, for example, Patent Document 1).

[0009] Triacetyl cellulose films used as polarizer protective films have their surfaces subjected to alkali treatment or the like, and therefore have extremely high affinity with hydrophilic adhesives. Therefore, protective films made of triacetyl cellulose films have extremely high adhesion to polarizers coated with hydrophilic adhesives. However, polyester films have insufficient adhesion to hydrophilic adhesives, and this tendency is particularly pronounced in polyester films that have been oriented by stretching. Therefore, in order to improve adhesion to polarizers or hydrophilic adhesives coated on polarizers, it has been reported to provide a coating layer by coating the surface of a polyester film with a highly hydrophilic material (see, for example, Patent Document 1).

[0010] In the field of conventional highly adhesive polyester films, it has been reported that a laminated polyester film having a coating layer containing a polyester resin using a naphthalenedicarboxylic acid component on at least one side of the polyester film has excellent adhesion to a surface functional layer such as a hard coat layer (see, for example, Patent Document 2).

[0011] It has also been reported that an easily adhesive polyester film having a coating layer on at least one side of the polyester film, the coating layer containing a polyurethane resin containing an aliphatic polycarbonate polyol as a constituent, which has excellent flexibility and adhesion, has excellent adhesion to an optical functional layer under high temperature and high humidity conditions (see, for example, Patent Document 3).

[0012] JP 2013-063610 A JP 2011-246663 A JP 2011-168053 A

[0013] In recent years, when used as a display component near the surface, high-quality films that are particularly transparent and free of scratches are required. Furthermore, to improve productivity, the film-forming conveying speed tends to increase as a process condition, and films that do not develop scratches even under more severe conditions are required. Display applications generally involve multiple surface processing steps, but there is a problem in that scratches can occur even during post-processing, reducing productivity. The present inventors focused on the occurrence of scratches that may be related to, for example, an easy-adhesion or easy-slip layer in a polyester film having a polyester film substrate and a coating layer, and completed the present invention.

[0014] The present invention was made in response to the problems of the conventional technology. Specifically, an object of the present invention is to provide a highly adhesive polyester film that can prevent scratches on the surface opposite to the coating layer that comes into contact with the coating layer during film formation and post-processing such as the addition of a functional layer, such as when the film is wound into a roll, and that can also prevent scratches on the functional layer formed on the opposite surface. Another object of the present invention is to provide a laminated polyester film having such a functional layer.

[0015] As a result of extensive research to achieve this object, the present inventors have discovered that controlling the flexibility of a coating layer can prevent particles contained in the coating layer from falling off and make the coating layer less susceptible to scratches, and have arrived at the present invention.

[0016] [1] An easily adhesive polyester film having a polyester film substrate and a coating layer, wherein the coating layer is formed from a composition containing a polycarbonate polyurethane resin (A), a polyester resin (B), a blocked isocyanate crosslinking agent (C), and particles, and wherein in a particle shedding test, the amount of particles shedding within the field of view is less than 30%. [2] The easily adhesive polyester film according to [1], wherein the difference in film haze before and after the particle shedding test is less than 0.55%. [3] The easily adhesive polyester film according to [1] or [2], wherein the polycarbonate polyurethane resin (A) has a structure represented by formula (1) in its molecule.

[0017] (In the formula, * represents a binding site, and n represents an integer of 5 to 10.)

[0018] [4] The highly adhesive polyester film according to any one of [1] to [3], wherein the polyester resin (B) is a polyester resin having a structure represented by formula (1) in the molecule.

[0019] (In the formula, * represents a binding site, and n represents an integer of 5 to 10.)

[0020] [5] A method for producing the highly adhesive polyester film according to any one of [1] to [4], comprising a step of applying a coating layer-forming composition to at least one surface of a polyester film substrate, the coating layer-forming composition comprising a polycarbonate polyurethane resin (A), a polyester resin (B), and a blocked isocyanate-based crosslinking agent (C) and particles, the polycarbonate polyurethane resin (A) having a structure represented by formula (1) in its molecule,

[0021] (In the formula, * represents a binding site, and n represents an integer of 5 to 10.)

[0022] The polyester resin (B) has a structure represented by formula (1) in the molecule,

[0023] (In the formula, * represents a binding site, and n represents an integer of 5 to 10.)

[0024] The blocked isocyanate crosslinking agent (C) has a structure represented by formula (1) in the molecule: (In the formula, * represents each bonding site, and n represents an integer of 5 to 10.) A method for producing an easily adhesive polyester film. [6] A laminated polyester film further having a functional layer on the coating layer of the easily adhesive polyester film according to any one of [1] to [4]. [7] A method for producing the laminated polyester film according to [6], comprising a step of applying a functional layer-forming composition to the coating layer surface of the easily adhesive polyester film according to any one of [1] to [4].

[0025] The adhesive polyester film of the present invention improves the flexibility of the coating layer and maintains high adhesion to the lubricant particles, thereby preventing particles from falling off the coating layer and preventing damage to the contact surface caused by the fallen particles. Therefore, during post-processing such as film formation and functional layer application of a film having a coating layer, such as when the film is wound into a roll, scratches on the surface opposite the contact surface with the coating layer can be prevented, and scratches on the functional layer formed on the opposite surface can also be prevented. Furthermore, because the film has excellent blocking resistance and transparency, it can be widely used in optical applications, etc.

[0026] Polyester Film Substrate The polyester film used as the substrate in the highly adhesive polyester film of the present invention is a film mainly composed of polyester resin. Here, "a 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 that the polyester resin is contained in an amount of 50% by mass or more, and when copolymerized with other monomers, it means that the polyester structural unit is contained in an amount of 50 mol% or more. 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.

[0027] The polyester resin material is not particularly limited, but a copolymer formed by polycondensation of a dicarboxylic acid component and a diol component, or a blend resin thereof can be used. Examples of dicarboxylic acid components constituting the polyester resin include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonecarboxylic acid, anthracenedicarboxylic 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-methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, dimer acid, sebacic acid, suberic acid, and dodecadicarboxylic acid.

[0028] Examples of diol components constituting the polyester resin include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decamethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexadiol, 2,2-bis(4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone.

[0029] The dicarboxylic acid component and the diol component may each be used alone or in combination of two or more kinds. In addition, other polycarboxylic acid components such as trimellitic acid and other polyol components such as trimethylolpropane may also be added as appropriate.

[0030] Specific examples of polyester resins include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Among these, polyethylene terephthalate is preferred in terms of the balance between physical properties and cost. In addition, it is also a preferred embodiment to contain other copolymerization components or other polymers in order to control optical properties such as polarization. From the viewpoint of controlling the optical properties of the polyester film, preferred copolymerization components include diethylene glycol and copolymerization components having norbornene in the side chain.

[0031] The intrinsic viscosity of the polyester resin (solvent: phenol / tetrachloroethane=60:40) is, for example, 0.50 to 1.0 dl / g.

[0032] In order to improve the handling properties of polyester films, such as slipperiness and windability, inert particles can be incorporated into the film. Examples of inert particles include inorganic particles such as silica, kaolinite, talc, light calcium carbonate, heavy calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, zinc sulfate, zinc carbonate, titanium dioxide, satin white, aluminum silicate, diatomaceous earth, calcium silicate, aluminum hydroxide, hydrated halloysite, magnesium carbonate, and magnesium hydroxide, as well as organic particles such as melamine, acrylic, styrene, and silicone. The average particle size is measured using the method described in the examples (number-based average particle size measured by SEM). To maintain high transparency, it is preferable to minimize the content of inert particles in the film. Therefore, it is preferable to use a multilayer structure in which particles are incorporated only in the surface layer of the film, or to incorporate particles substantially free of particles in the film and incorporate fine particles only in a coating layer laminated on at least one side of the polyester film.

[0033] The phrase "substantially free of particles" means, for example, in the case of inorganic particles, that the content of elements derived from the particles is 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit when quantitatively analyzed by fluorescent X-ray analysis. This is because even if particles are not intentionally added to the substrate film, contaminants derived from foreign matter or dirt adhering to the raw material resin or the production line or equipment in the film manufacturing process may peel off and be inevitably mixed into the film.

[0034] Furthermore, when the polyester film has a multi-layer structure, it may have a two-kind three-layer structure in which the inner layer does not substantially contain inert particles and only the outermost layer (second layer) contains inert particles, which is preferable because it can achieve both transparency and processability.

[0035] The polyester film serving as the substrate may be a single layer or a laminate of two or more layers. Furthermore, various additives may be incorporated into the film as needed, as long as the effects of the present invention are achieved. Examples of additives include antioxidants, light-resistant agents, antigelling agents, organic wetting agents, antistatic agents, UV absorbers, surfactants, and the like. When the film has a laminated structure, it is also preferable to incorporate additives into each layer as needed, depending on the function of each layer. For example, adding a UV absorber or the like to an inner layer is a preferred embodiment to prevent photodegradation of the polarizer.

[0036] The polyester film can be produced by a conventional method. For example, it can be obtained by melt-extruding a material containing the above-mentioned 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 the present invention, either a non-stretched film or a stretched film can be used, but a stretched film is preferred from the viewpoint of durability such as mechanical strength and chemical resistance.

[0037] When the polyester film is a stretched film, the stretching method is not particularly limited, and may be a longitudinal uniaxial stretching method, a transverse uniaxial stretching method, a longitudinal and transverse sequential biaxial stretching method, a longitudinal and transverse simultaneous biaxial stretching method, or the like. When stretching a polyester film, the stretching may be carried out before laminating an easy-adhesion coating layer described below, or may be carried out after laminating the easy-adhesion coating layer. It is also possible to uniaxially stretch the polyester film in the longitudinal or transverse direction before laminating the easy-adhesion coating layer, and then stretch the polyester film in the other direction after laminating the coating layer.

[0038] Coating Layer The highly adhesive polyester film of the present invention has a polyester film and a coating layer. For example, an highly adhesive coating layer is laminated on at least one surface of the polyester film substrate. In the present invention, the coating layer is a layer formed from a composition containing a polycarbonate polyurethane resin (A), a polyester resin (B), a blocked isocyanate crosslinking agent (C), and particles. The highly adhesive polyester film of the present invention can be produced by applying a coating layer-forming composition to at least one surface of a polyester film substrate. The present invention may have the coating layer of the present invention on both surfaces of the polyester film substrate.

[0039] The components of the coating layer are described in detail below. The binder resin constituting the coating layer is a resin having high adhesiveness, and contains a polycarbonate polyurethane resin (A) which is a urethane resin having a polycarbonate structure, and a polyester resin (B), and the crosslinking agent contains a blocked isocyanate crosslinking agent (C).

[0040] The polycarbonate polyurethane resin (A) contains a cyclohexane ring structure in its molecule, and has a structure in which at least one (particularly one or two) hydrogen atoms on the cyclohexane ring are substituted with a hydrocarbon group (hereinafter, this structure may be referred to as a "cyclohexane ring structure"). In other words, it has a structure in which at least one hydrogen atom on the cyclohexane ring is bonded to a carbon atom of a hydrocarbon group (for example, an alkyl group having 1 to 3 carbon atoms, an alkylene group having 1 to 3 carbon atoms, etc.).

[0041] The polycarbonate polyurethane resin (A) further has a structure containing a methylene chain having 5 to 10 carbon atoms in its molecule (hereinafter, this structure may be referred to as a "C5 to C10 methylene chain structure.") The polycarbonate polyurethane resin (A) may be one type or a mixture of two or more types.

[0042] In consideration of the interaction with the polycarbonate polyurethane resin (A), the polyester resin (B) has a cyclohexane ring structure and / or a C5 to C10 methylene chain structure in its molecule. That is, the polyester resin (B) has both a cyclohexane ring structure and a C5 to C10 methylene chain structure, or either one of them, in its molecule. The polyester resin (B) may be one type or a mixture of two or more types.

[0043] The blocked isocyanate crosslinking agent (C) has a cyclohexane ring structure and / or a C5-C10 methylene chain structure in its molecule, taking into consideration the interaction with the polycarbonate polyurethane resin (A) and the polyester resin (B). That is, the blocked isocyanate crosslinking agent (C) has both a cyclohexane ring structure and a C5-C10 methylene chain structure, or either one of them, in its molecule. The blocked isocyanate crosslinking agent may be one type or a mixture of two or more types.

[0044] In one embodiment, the polycarbonate polyurethane resin (A) has a structure represented by formula (1) in the molecule:

[0045] (In the formula, * represents a binding site, and n represents an integer of 5 to 10.)

[0046] The polycarbonate polyurethane resin (A) having the above structure can improve the flexibility of the coating layer, and can maintain high adhesion to particles (e.g., lubricant particles).Furthermore, it can prevent particles from falling off in the coating layer and prevent damage to the contact surface caused by the fallen particles.

[0047] In one embodiment, the polyester resin (B) has a structure represented by formula (1) in the molecule.

[0048] (In the formula, * represents a binding site, and n represents an integer of 5 to 10.)

[0049] The polyester resin (B) having the above structure can improve the flexibility of the coating layer and further maintain high adhesion to particles (e.g., lubricant particles). It can also prevent particles from falling off in the coating layer and prevent damage to the contact surface caused by the fallen particles. Furthermore, in the present invention, good compatibility with the polycarbonate polyurethane resin (A) can be maintained, improving the adhesion between the substrate and the coating layer. While not intended to be limited to a specific theory, it is presumed that a suitable interaction (steric structure) is formed between the polycarbonate polyurethane resin (A) and the polyester resin (B), thereby ensuring both satisfactory particle retention and flexibility.

[0050] In one embodiment, the blocked isocyanate crosslinking agent (C) has a structure represented by formula (1) in the molecule:

[0051] (In the formula, * represents a binding site, and n represents an integer of 5 to 10.)

[0052] The blocked isocyanate crosslinking agent (C) has a structure represented by formula (1) in its molecule, thereby maintaining good compatibility with the polycarbonate polyurethane resin (A) and the polyester resin (B). It is presumed that the good compatibility allows the blocked isocyanate crosslinking agent (C) to crosslink evenly throughout the resin, thereby achieving the effect of forming a tougher coating film.

[0053] Examples of the "cyclohexane ring structure" contained in each molecule of the polycarbonate polyurethane resin (A), the polyester resin (B), and the crosslinking agent (C) of the blocked isocyanate crosslinking agent include a structure represented by formula (1).

[0054] (In the formula, * indicates a binding site.)

[0055] As the structure represented by formula (1), a structure represented by formula (1a) is preferred.

[0056] (wherein * is the same as above.)

[0057] Furthermore, the structure represented by formula (1b) is more preferred.

[0058] (wherein * is the same as above.)

[0059] The structure represented by the formula (1b) is more preferably a structure derived from cyclohexanedimethanol (particularly 1,4-cyclohexanedimethanol). In this case, the two * marks are the bonding sites with the oxygen atoms constituting the resin.

[0060] Furthermore, examples of the "C5-C10 methylene chain structure" include a structure represented by formula (2).

[0061] (In the formula, n represents an integer of 5 to 10, and * represents a binding site.)

[0062] In the above formulas (1) and (2), * denotes a bonding site with an atom constituting the binder resin or crosslinking agent. The atom may be the same or different, and examples thereof include a hydrogen atom, a carbon atom, an oxygen atom, and a nitrogen atom. Of the two *s in each formula, at least one is preferably a carbon atom, an oxygen atom, a nitrogen atom, or the like. In the above formula (2), n is preferably 5 to 9, and more preferably 5 to 6.

[0063] The "cyclohexane ring structure" and "C5 to C10 methylene chain structure" contained in each of the polycarbonate polyurethane resin (A), the polyester resin (B), and the blocked isocyanate crosslinking agent (C) may be the same or different.

[0064] By employing a coating layer made of a binder resin and a crosslinking agent having such a structure, the adhesion between the polyester film substrate and the functional layer is dramatically improved.

[0065] One reason for this is the good compatibility between the coating layer and the composition of the functional layer described below. The functional layer is obtained by UV curing through UV irradiation and has a crosslinked network structure. The polycarbonate polyurethane resin (A), polyester resin (B), and blocked isocyanate crosslinking agent (C) of the coating layer all have at least a cyclohexane ring structure or a C5-C10 methylene chain structure in their molecules, which allows the resins to interact with each other, making them more compatible and entangled. Furthermore, it is believed that these entangled resins become entangled in the network structure of the functional layer formed thereon, resulting in a coating layer with superior adhesion compared to conventional coating layers. Furthermore, since the coating layer contains polyester resin (B), it is believed that adhesion to the polyester film substrate is improved, resulting in a coating layer with superior adhesion.

[0066] (Polycarbonate Polyurethane Resin (A)) The polycarbonate polyurethane resin (A) may have, in its molecule, both a cyclohexane ring structure, i.e., a structure containing a cyclohexane ring structure in which at least one hydrogen atom on the cyclohexane ring is substituted with a hydrocarbon group, and a C5-C10 methylene chain structure, i.e., a structure containing a methylene chain having from 5 to 10 carbon atoms.

[0067] The content of the cyclohexane ring structure in the polycarbonate polyurethane resin (A) is usually 5% by mass or more and 55% by mass or less, preferably 10% by mass or more and 50% by mass or less, and more preferably 15% by mass or more and 45% by mass or less. If the content is 5% by mass or more, there are a sufficient number of cyclohexane ring structure units that allow the resins to interact with each other, so the strength of the resin in the coating layer is maintained and particle shedding properties in the coating layer are likely to be good. If the content is 55% by mass or less, the flexibility of the resin in the coating layer is maintained and the particle retention force is also strengthened, tending to improve particle shedding properties. The content of the cyclohexane ring structure in the polycarbonate polyurethane resin (A) is determined by the ratio of the cyclohexane ring structure (-C) to the total mass of 100 g of the polycarbonate polyurethane resin (A). ６ H １0 -CH ２Specifically, it can be calculated from "the molecular weight and mol % of each component such as the polycarbonate diol component and the diisocyanate component constituting the polycarbonate polyurethane resin (A)", "the mol % of the component having a cyclohexane ring", and "the proportion of the molecular weight occupied by the cyclohexane ring structure in the molecular weight of the component having a cyclohexane ring".

[0068] The content of C5 to C10 methylene chain structures in the polycarbonate polyurethane resin (A) is typically 5% by mass or more and 55% by mass or less, preferably 10% by mass or more and 50% by mass or less, and more preferably 15% by mass or more and 45% by mass or less. If the content is 5% by mass or more, there will be a sufficient number of C5 to C10 methylene chain structure units that interact with each other, resulting in increased entanglement of the resin in the coating layer, maintaining strength and tending to improve adhesion under high temperature and high humidity conditions. If the content is 55% by mass or less, the flexibility of the resin in the coating layer will be maintained and particle shedding will also be likely to be improved.

[0069] The content of the C5 to C10 methylene chain structure in the polycarbonate polyurethane resin (A) is the ratio of the C5 to C10 methylene chain structure (-(CH ２ ) ｎ -, n are the same as above.) Specifically, it can be calculated from "the molecular weight and mol % of each component such as the polycarbonate diol component and the diisocyanate component constituting the polycarbonate polyurethane resin (A)", "the mol % of the component having a methylene chain having from 5 to 10 carbon atoms", and "the proportion of the molecular weight occupied by the methylene chain having from 5 to 10 carbon atoms among the molecular weight of the component having a methylene chain having from 5 to 10 carbon atoms".

[0070] The polycarbonate polyurethane resin (A) is obtained by addition reaction of a polycarbonate diol component, a diisocyanate component, and, if necessary, a diol component as a chain extender, and at least one of these components contains a cyclohexane ring structure and / or a C5 to C10 methylene chain structure, and the entire polycarbonate polyurethane resin (A) contains both the cyclohexane ring structure and the C5 to C10 methylene chain structure.

[0071] The polycarbonate diol component necessary for preparing the polycarbonate polyurethane resin (A) can be produced by reacting a diol component with a carbonate component. Examples of the diol component include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediethanol, decamethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexadiol, 2,2-bis(4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone. Among these, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, and 1,4-cyclohexanediethanol are particularly preferred because they have the above-mentioned cyclohexane ring structure. Furthermore, hexamethylene glycol, decamethylene glycol, 1,5-pentanediol, 1,6-hexadiol, etc., have the above-mentioned C5 to C10 methylene chain structure and are particularly preferred. These diol components can be used alone or in combination of two or more. When combining two or more, the ratio is not particularly limited, and can be adjusted to obtain a polycarbonate polyurethane resin with the required properties. Examples of carbonate components include dimethyl carbonate, ethylene carbonate, and phosgene.

[0072] Examples of diisocyanate components necessary for preparing the polycarbonate polyurethane resin (A) include toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4,4-methylenebiscyclohexyl diisocyanate, 1,2-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, etc. Among these, isophorone diisocyanate, 4,4-methylenebiscyclohexyl diisocyanate, 1,2-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, etc., have the cyclohexane ring structure described above and are particularly preferred. Furthermore, these isocyanate components can be used alone or in combination of two or more. The ratio when two or more components are combined is not particularly limited, and can be adjusted so as to obtain a polycarbonate polyurethane resin having the required properties.

[0073] (Polyester Resin (B)) The polyester resin (B) used in combination with the polycarbonate polyurethane resin (A) may have a cyclohexane ring structure and / or a C5 to C10 methylene chain structure in its molecule.

[0074] The content of the cyclohexane ring structure in the polyester resin (B) is usually preferably 5% by mass or more and 20% by mass or less, and more preferably 10% by mass or more and 15% by mass or less. By making the content 20% by mass or less, it becomes easy to ensure the mobility and flexibility of the resin, and by making the content 5% by mass or more, it becomes possible to ensure the number of units of the cyclohexane ring structure that interact with the polycarbonate polyurethane resin (A), thereby ensuring the strength of the resin in the coating layer and easily improving particle shedding properties.

[0075] The content of the cyclohexane ring structure in the polyester resin (B) is the ratio of the cyclohexane ring structure (-C) to the total mass of 100 g of the polyester resin (B). ６ H １０ -CH ２Specifically, it can be calculated from "the mol % and molecular weight of each monomer component constituting the polyester resin (B)," "the mol % of the monomer component having a cyclohexane ring among all the monomer components," and "the proportion of the molecular weight of the cyclohexane ring structure among the molecular weight of the monomer component having a cyclohexane ring."

[0076] The content of the C5 to C10 methylene chain structure in the polyester resin (B) is usually more preferably 5% by mass or more and 20% by mass or less, and more preferably 10% by mass or more and 15% by mass or less. By making the content 20% by mass or less, it becomes easier to ensure the mobility and flexibility of the resin, and by making the content 5% by mass or more, it becomes possible to ensure the number of units of the C5 to C10 methylene chain structure that interact with the polycarbonate polyurethane resin (A), thereby ensuring the strength of the resin in the coating layer and also making it easier to improve particle shedding properties. The content of the C5 to C10 methylene chain structure in the polyester resin (B) is the ratio of the C5 to C10 methylene chain structure (-(CH ２ ) ｎ -, n is the same as above.) Specifically, it can be calculated from "the mol % and molecular weight of each monomer component constituting the polyester resin (B)," "the mol % of monomer components having a methylene chain having from 5 to 10 carbon atoms among all monomer components," and "the proportion of the molecular weight of methylene chains having from 5 to 10 carbon atoms among the molecular weights of monomer components having a methylene chain having from 5 to 10 carbon atoms."

[0077] The polyester resin (B) is a copolymer polyester obtained by polycondensation of a dicarboxylic acid component and a diol component. The dicarboxylic acid component and the diol component may each be used alone or in combination of two or more. In the present invention, at least one of the dicarboxylic acid component and the diol component has a cyclohexane ring structure and / or a C5 to C10 methylene chain structure.

[0078] Examples of dicarboxylic acid components include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonecarboxylic acid, anthracenedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, cyclohexylmethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, cyclohexylmethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, dimer acid, sebacic acid, suberic acid, dodecadicarboxylic acid, and 1,1-cyclohexanediacetic acid. Among these, cyclohexylmethylmalonic acid, cyclohexylmethylsuccinic acid, 1,1-cyclohexanediacetic acid, etc. are particularly preferred because they have the above-mentioned cyclohexane ring structure.

[0079] Water dispersibility can be imparted to the polyester resin (B). In this case, for example, in addition to the dicarboxylic acid component described above, a dicarboxylic acid component having a hydrophilic group (such as a sulfo group) can be copolymerized. Examples of dicarboxylic acid components having a hydrophilic group include 5-sulfoterephthalic acid, 5-sulfoisophthalic acid, and salts thereof. The dicarboxylic acid component having a hydrophilic group can be copolymerized in an amount of 1 to 10 mol % based on the total dicarboxylic acid components.

[0080] If necessary, a small amount of a monocarboxylic acid such as cyclohexylacetic acid may also be used.

[0081] Examples of diol components include ethylene glycol, propylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediethanol, hexamethylene glycol, decamethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexadiol, 2,2-bis(4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone. Among these, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, and 1,4-cyclohexanediethanol are particularly preferred because they have the above-mentioned cyclohexane ring structure. Furthermore, hexamethylene glycol, decamethylene glycol, 1,5-pentanediol, and 1,6-hexadiol are particularly preferred because they have the above-mentioned C5 to C10 methylene chain structure.

[0082] The ratio of the dicarboxylic acid component and the diol component when combined is not particularly limited, and can be adjusted so as to obtain a polyester having the required properties.

[0083] In the present invention, the binder resin comprises a polycarbonate polyurethane resin (A) and a polyester resin (B). The ratio of the two is not particularly limited as long as the physical properties of the resulting coating layer can be ensured. When the total amount of the binder resin is taken as 100% by mass, the polycarbonate polyurethane resin (A) is usually preferably 35% by mass or more and 85% by mass or less, more preferably 40% by mass or more and 80% by mass or less, and even more preferably 45% by mass or more and 75% by mass or less. By making the polycarbonate polyurethane resin (A) 35% by mass or more, the balance between flexibility and hardness of the urethane resin can be ensured, and adhesion over time can be ensured. Furthermore, by making it 85% by mass or less, the balance between hardness and softness of the coating layer can be maintained and flexibility can be improved, so that the coating layer functions optimally.

[0084] (Crosslinking Agent) In the present invention, a crosslinking agent is contained in the composition used to form the coating layer in order to form a crosslinked structure between resins in the coating layer. By including a crosslinking agent, it is possible to further improve adhesion under high temperature and high humidity conditions. In addition, by including a crosslinking agent together with the polycarbonate polyurethane resin (A) and the polyester resin (B), it becomes easier to appropriately adjust the flexibility of the coating layer, and it is thought that this will further improve particle shedding properties. Specific examples of crosslinking agents include isocyanate-based crosslinking agents (particularly the blocked isocyanate-based crosslinking agent (C) described below) from the viewpoints of the stability of the coating liquid over time and the effect of maintaining the flexibility of the coating layer. In addition, a catalyst or the like can be used as needed to promote the crosslinking reaction.

[0085] The isocyanate crosslinking agent is preferably a difunctional or higher (further trifunctional or higher) polyisocyanate crosslinking agent. Examples of the crosslinking agent include polyisocyanate (particularly diisocyanate) compounds such as allophanate, biuret, adduct, urtdione, and isocyanurate. Examples of the polyisocyanate compound include diisocyanate compounds such as hexamethylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, cyclohexane-1,2-diylbis(methylene)diisocyanate, pentamethylene diisocyanate, isophorone diisocyanate, and bis(isocyanatomethyl)cyclohexane.

[0086] Among the above polyisocyanate-based crosslinking agents, one or more polyisocyanate-based crosslinking agents selected from the group consisting of allophanate compounds, biuret compounds, and adduct compounds are preferred because they have small steric hindrance as a polymer and easily interact with the structures represented by formulas (1) and (2) derived from the polycarbonate diol that constitutes the polycarbonate polyurethane.

[0087] An allophanate is a compound obtained by forming a urethane from a polyisocyanate and an alcohol and then reacting this with a polyisocyanate. Examples of such an allophanate include a compound obtained by reacting a monohydric alcohol (such as 1-butanol) with dicyclohexylmethane-4,4'-diisocyanate, and a compound obtained by reacting a monohydric alcohol (such as 1-butanol) with cyclohexane-1,2-diylbis(methylene)diisocyanate.

[0088] The adduct is a tri- or higher functional isocyanate obtained by reacting a polyisocyanate with a tri- or higher functional low-molecular-weight active hydrogen-containing compound, and examples thereof include a compound obtained by reacting trimethylolpropane with hexamethylene diisocyanate, a compound obtained by reacting trimethylolpropane with dicyclohexylmethane-4,4'-diisocyanate, and a compound obtained by reacting trimethylolpropane with cyclohexane-1,2-diylbis(methylene)diisocyanate.

[0089] By including these allophanate, biuret, or adduct isocyanate-based crosslinking agents in the coating layer composition, the reactivity is increased, the crosslinking reaction is facilitated, the crosslink density of the resulting coating layer can be improved, and the denseness of the resulting coating layer can be improved.

[0090] The isocyanate crosslinking agent is preferably a blocked isocyanate crosslinking agent (C) incorporating a blocking agent to control the reactivity of isocyanate. Examples of blocking agents include bisulfite compounds such as sodium bisulfite; 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; mercaptans such as butyl mercaptan and dodecyl mercaptan; acid amides such as acetanilide and acetic acid amide; lactams such as ε-caprolactam and δ-valerolactam; acid imides such as succinimide and maleimide; oximes such as acetaldoxime, acetone oxime, and methyl ethyl ketone oxime; and amines such as diphenylaniline, aniline, and ethyleneimine. From the viewpoint of reactivity, a blocking agent having a pyrazole skeleton is suitable for this system.

[0091] Furthermore, the blocked isocyanate crosslinking agent (C) has a cyclohexane ring structure and / or a C5 to C10 methylene chain structure in its molecule for the purpose of increasing the interaction with the resin used in combination.

[0092] The content of the cyclohexane ring structure in the blocked isocyanate crosslinking agent (C) is usually preferably 10% by mass or more and 40% by mass or less, and more preferably 15% by mass or more and 35% by mass or less. By making the content 40% by mass or less, it becomes easier to ensure the mobility and flexibility of the crosslinking agent, and by making the content 10% by mass or more, it becomes possible to ensure the number of units of the cyclohexane ring structure that interact with the resin, thereby ensuring the strength of the resin in the coating layer and expected to improve the particle retention force in the coating layer. The content of the cyclohexane ring structure in the blocked isocyanate crosslinking agent (C) is determined by the ratio of the cyclohexane ring structure (-C) to the total mass of 100 g of the blocked isocyanate crosslinking agent (C). ６ H １０ -CH ２Specifically, it can be calculated from "the mol % and molecular weight of each component constituting the blocked isocyanate crosslinking agent (C)," "the mol % of the component having a cyclohexane ring among all the components," and "the proportion of the molecular weight of the cyclohexane ring structure among the molecular weight of the component having a cyclohexane ring."

[0093] The content of the C5 to C10 methylene chain structure in the blocked isocyanate crosslinking agent (C) is usually preferably 10% by mass or more and 40% by mass or less, and more preferably 15% by mass or more and 35% by mass or less. By making the content 40% by mass or less, it becomes easier to ensure the mobility and flexibility of the resin, and by making the content 10% by mass or more, the number of units of the C5 to C10 methylene chain structure that interact with the resin can be ensured, ensuring the strength of the resin in the coating layer and expected to improve the particle retention force in the coating layer. The content of the C5 to C10 methylene chain structure in the blocked isocyanate crosslinking agent (C) is determined by the ratio of the C5 to C10 methylene chain structure (-(CH ２ ) ｎ -, n is the same as above.) Specifically, it can be calculated from "the mol % and molecular weight of each component constituting the blocked isocyanate crosslinking agent (C)," "the mol % of components having a methylene chain having from 5 to 10 carbon atoms among all components," and "the proportion of the molecular weight of the methylene chain having from 5 to 10 carbon atoms among the molecular weights of components having a methylene chain having from 5 to 10 carbon atoms."

[0094] The blocked isocyanate crosslinking agent (C) may have a cyclohexane ring structure and / or a C5 to C10 methylene chain structure in the molecule. Examples of diisocyanate components that can be used to prepare this blocked isocyanate crosslinking agent (C) include pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4,4-methylenebiscyclohexyl diisocyanate, 1,2-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, etc. Among these, isophorone diisocyanate, 4,4-methylenebiscyclohexyl diisocyanate, 1,2-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, etc. are particularly preferred because they have a structure in which at least one hydrogen atom on the cyclohexane ring is substituted with a hydrocarbon group. Hexamethylene diisocyanate and the like are particularly preferred because they have a C5 to C10 methylene chain structure. These isocyanate components can be used alone or in combination of two or more. When combining two or more, the ratio is not particularly limited, and can be adjusted to obtain an isocyanate-based crosslinking agent that exhibits the required properties.

[0095] It is preferable to introduce a hydrophilic group into the blocked isocyanate crosslinking agent (C) from the viewpoint of imparting water dispersibility in aqueous solvents. Furthermore, the hydrophilic group is preferably an anionic group such as a carboxyl group or a sulfonic acid group, or a nonionic group such as an oxyalkyl group. Crosslinking agents having these hydrophilic groups can be prepared by previously reacting a polyisocyanate, which serves as the base of the blocked isocyanate crosslinking agent (C), with a compound having a hydrophilic group and a reactive group such as a hydroxyl group.

[0096] Therefore, the blocked isocyanate crosslinking agent (C) is preferably a bifunctional or higher (further, trifunctional or higher) blocked isocyanate crosslinking agent, and is preferably an allophanate, biuret or adduct of a polyisocyanate compound.

[0097] When the total mass of the binder resin (particularly the polycarbonate polyurethane resin (A) and the polyester resin (B)) and the blocked isocyanate crosslinking agent (C) is taken as 100% by mass, the content of the binder resin is preferably 45 to 95% by mass from the viewpoint of adhesion, more preferably 55 to 90% by mass, even more preferably 60 to 90% by mass, and most preferably 80 to 90% by mass. When the content is 95% by mass or less, the strength of the coating layer is maintained and adhesion is good under high temperature and high humidity conditions. When the content is 45% by mass or more, the flexibility of the coating layer is maintained and adhesion is maintained under normal temperature and high temperature and high humidity conditions, which is preferable. Furthermore, when the total mass of the binder resin and the crosslinking agent is taken as 100% by mass, the content of the blocked isocyanate crosslinking agent (C) is preferably 5 to 50% by mass, more preferably 10 to 45% by mass, even more preferably 10 to 40% by mass, and most preferably 10 to 20% by mass.

[0098] The present invention is characterized in that the polycarbonate polyurethane resin (A) used in the coating layer contains a cyclohexane ring structure and a C5-C10 methylene chain structure in its molecule, and the polyester resin (B) and the blocked isocyanate crosslinking agent (C) each contain a cyclohexane ring structure and / or a C5-C10 methylene chain structure, thereby effectively demonstrating the effects of the present invention. Although the exact mechanism is unclear, the coating layer of the present invention functions optimally as a coating layer because it can maintain the rigidity of the resin while improving its flexibility. In other words, the coating layer not only exhibits excellent adhesion to the polyester film substrate and adherends such as functional layers, but also significantly improves adhesion over time. This makes it possible to obtain a film that maintains its quality for a long period of time.

[0099] (Additives) The coating layer of the present invention may contain known additives, such as surfactants, antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic particles, antistatic agents, nucleating agents, etc., within the range that does not impair the effects of the present invention. However, it is preferable not to use substances that are undesirable from an environmental perspective, etc.

[0100] In order to further improve the blocking resistance of the coating layer, it is also a preferred embodiment to add particles (especially inert particles) to the coating layer. Examples of particles to be contained in the coating layer include inorganic particles and organic polymer particles. Examples of inorganic particles include titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, and mixtures thereof. Furthermore, other common inorganic particles such as calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, calcium fluoride, and the like can also be used in combination. Examples of organic polymer particles include styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based polymer particles.

[0101] The average particle size (average particle size based on the number of particles by SEM; the same applies hereinafter) of the particles (preferably inactive particles) in the coating layer is preferably 0.04 to 2.0 μm, more preferably 0.05 to 1.0 μm. When the average particle size of the inactive particles is 0.04 μm or more, it is easy to form irregularities on the surface of the coating layer, which improves the handling properties of the highly adhesive polyester film, such as the slipperiness and winding properties, and provides good processability during lamination, which is preferred. On the other hand, when the average particle size of the inactive particles is 2.0 μm or less, particle detachment is less likely to occur, which is preferred. The particle concentration in the coating layer is preferably 1 to 20% by mass relative to the resin content.

[0102] (Formation of Coating Layer) A coating layer-forming composition (hereinafter also referred to as "coating liquid") for forming a coating layer may further contain a surfactant for the purposes of improving leveling during application and degassing the coating liquid. Examples of surfactants include cationic, anionic, and nonionic surfactants, with silicone-based, acetylene glycol-based, and fluorine-based surfactants being preferred. These surfactants are preferably contained in the coating layer-forming composition to an extent that does not impair the effect of suppressing iridescence under a three-wavelength LED light source or the adhesion.

[0103] As a method for applying the coating liquid onto the polyester film, either a so-called in-line coating method in which the coating is carried out simultaneously with the polyester film formation, or a so-called off-line coating method in which the coating is carried out using a separate coater after the polyester substrate film has been formed, can be applied, but the in-line coating method is more efficient and more preferred.

[0104] As a coating method, any known method can be used for applying the coating liquid to a polyethylene terephthalate (hereinafter abbreviated as PET) film. Examples include reverse roll coating, gravure coating, kiss coating, die coater, roll brush, spray coating, air knife coating, wire bar coating, pipe doctor coating, impregnation coating, curtain coating, etc. These methods can be used alone or in combination.

[0105] In the present invention, a method for providing a coating layer on a polyester film includes applying a coating liquid containing a solvent, particles, and a resin to the polyester film and drying the coating liquid. Examples of the solvent include water or a mixture of water and an organic solvent. From the viewpoint of environmental concerns, however, water alone or a mixture of water and a water-soluble organic solvent is preferred. Examples of water-soluble organic solvents include alcohols such as isopropyl alcohol and ethanol; ketones such as methyl ethyl ketone; ethers such as butyl cellosolve; amines such as triethanolamine; and amides such as N-methylpyrrolidone.

[0106] The solid content of the coating solution is preferably 2% by mass or more, more preferably 4% by mass or more, relative to the total mass of the coating solution, although this depends on the type of binder resin, the type of solvent, etc. The solid content of the coating solution is preferably 35% by mass or less, more preferably 15% by mass or less.

[0107] The drying temperature after application also depends on the type of binder resin, the type of solvent, the presence or absence of a crosslinking agent, the solid content concentration, etc., but is preferably 80°C or higher and 250°C or lower.

[0108] The amount of coating of the coating solution is, for example, 0.03 to 0.24 g / m 2 in terms of the amount of solid content on the polyester film after drying. ２ , and further 0.06 to 0.18 g / m ２ When a film stretching step is carried out after coating and drying, the solid content on the polyester film after stretching can be adjusted to fall within the above range.

[0109] The stretched polyester film may be subjected to a heat treatment (for example, at 70 to 250°C, preferably at 80 to 245°C) while being fixed by a tenter, and may further be subjected to a relaxation treatment at 120 to 250°C.

[0110] As described above, the highly adhesive polyester film of the present invention is produced through the coating, drying, stretching, and heat treatment steps.

[0111] The thickness of the coating layer may be 30 nm or more and 200 nm or less, 40 nm or more and 160 nm or less, etc. If it is prepared within this range, it is preferable because it is easy to achieve both processability and adhesion. More preferably, it is 50 nm or more and 150 nm or less, and even more preferably, it is 70 nm or more and 110 nm or less. When the thickness of the coating layer is 30 nm or more, adhesion becomes good, which is preferable. When the thickness of the coating layer is 200 nm or less, blocking is less likely to occur, which is preferable.

[0112] The thickness of the coating layer was determined by observing the cross section of the cut film with a transmission electron microscope (TEM) and measuring the thickness of the coating layer at 10 random points, and averaging the measured values.

[0113] The present invention also provides a laminated polyester film in which a functional layer having various properties is provided on a coating layer of a highly adhesive polyester film. The functional layer refers to a layer having functionality, such as a hard coat layer, an antiglare layer, an antiglare antireflection layer, an antireflection layer, a low-reflection layer, or an antistatic layer, for the purpose of preventing reflection, suppressing glare, suppressing rainbow unevenness, suppressing scratches, etc. Various functional layers known in the technical field can be used, and the type is not particularly limited.

[0114] For example, when forming a hard coat layer on a coating layer, known materials for the hard coat layer can be used and are not particularly limited. Examples of such materials include resin compounds (especially curable resins) that polymerize and / or react upon drying, heat, chemical reaction, or irradiation with electron beams, radiation, or ultraviolet rays. Examples of such curable resins include melamine-based, acrylic-based, silicone-based, and polyvinyl alcohol-based curable resins. Photocurable acrylic-based curable resins are preferred for achieving high surface hardness or optical design. Examples of such acrylic-based curable resins include polyfunctional (meth)acrylate monomers and acrylate-based oligomers. Examples of acrylate-based oligomers include polyester acrylate, epoxy acrylate, urethane acrylate, polyether acrylate, polybutadiene acrylate, and silicone acrylate. By mixing these acrylic-based curable resins with reactive diluents, photopolymerization initiators, sensitizers, and the like, a coating composition for forming the optical functional layer can be obtained.

[0115] The hard coat layer may have an anti-glare function that scatters external light. The anti-glare function is obtained by forming irregularities on the surface of the hard coat layer. In this case, the haze of the film is ideally 0 to 50%, more preferably 0 to 40%, and particularly preferably 0 to 30%. Of course, 0% is ideal, and it may be 0.2% or more, or 0.5% or more.

[0116] Furthermore, a layer with a different refractive index can be provided as a functional layer, and a low-reflection (anti-reflection) treatment can be applied to suppress light reflection by changing the light transmission characteristics. The refractive index of a functional layer such as a hard coat layer is preferably adjusted to ideally have a reflectance of 0 to 1.0%, more preferably 0 to 0.8%, and particularly preferably 0 to 0.5%. Of course, 0% is ideal, and it is acceptable for it to be 0.05% or more, or even 0.1% or more.

[0117] The highly adhesive polyester film of the present invention can be used as a polarizer protective film. Generally, a polarizing plate is formed by disposing polarizer protective films on both sides of a polarizer, and it is preferable that the polarizer protective film on at least one side of the polarizer is the highly adhesive polyester film of the present invention. The polarizer protective film on the other side may be the highly adhesive polyester film of the present invention, or may be a film without birefringence, such as a triacetyl cellulose film, an acrylic film, or a norbornene-based film.

[0118] Examples of polarizers include those made of a polyvinyl alcohol-based film containing a dichroic material such as iodine. The polarizer protective film is attached to the polarizer directly or via an adhesive layer, but from the perspective of improving adhesion, attachment via an adhesive is preferred. In this case, the coating layer of the highly adhesive polyester film of the present invention is preferably disposed on the polarizer surface or the adhesive layer surface. Examples of polarizers suitable for bonding the polyester film of the present invention include those obtained by dyeing and adsorbing iodine or a dichroic material onto a polyvinyl alcohol-based film, uniaxially stretching the film in a boric acid aqueous solution, and then washing and drying the film while maintaining the stretched state. The stretching ratio for uniaxial stretching is typically about 4 to 8 times. Polyvinyl alcohol is suitable as the polyvinyl alcohol-based film, and commercially available products such as "Kuraray Vinylon" (manufactured by Kuraray Co., Ltd.), "Tohcello Vinylon" (manufactured by Tohcello Co., Ltd.), and "Nippon Vinylon" (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) can be used. Examples of dichroic materials include iodine, disazo compounds, and polymethine dyes.

[0119] When the adhesive layer to be applied to the polarizer is to be thin, it is preferable to use an aqueous adhesive, i.e., an adhesive component dissolved or dispersed in water. For example, a composition containing a polyvinyl alcohol resin, a urethane resin, or the like as the main component and, if necessary, an isocyanate compound, an epoxy compound, or the like, blended therein can be used to improve adhesion. The thickness of the adhesive layer is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less.

[0120] When a polyvinyl alcohol resin is used as the main component of the adhesive, in addition to partially saponified polyvinyl alcohol and fully saponified polyvinyl alcohol, modified polyvinyl alcohol resins such as carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, and amino group-modified polyvinyl alcohol may be used. The concentration of the polyvinyl alcohol resin in the adhesive is preferably 1 to 10% by mass, more preferably 2 to 7% by mass.

[0121] When further improvement in productivity is desired, it is preferable to use a photocurable adhesive as the adhesive to be applied to the polarizer. The thickness of the adhesive layer after curing can be set as desired by designing the characteristics of the polarizing plate, and a smaller thickness is preferable from the viewpoint of reducing adhesive material costs. Generally, it is 0.01 to 20 μm, preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm. An adhesive layer thickness of 0.01 μm or more is preferable because air bubbles are less likely to be mixed into the adhesive layer, resulting in good adhesion and durability. An adhesive layer thickness of 20 μm or less is preferable because the adhesive reactivity is sufficient and the polarizing plate has good moist heat resistance.

[0122] The photocurable adhesive preferably contains an epoxy compound containing no aromatic ring as a main component, a photocationic curable component (I), and a photocationic polymerization initiator (II).

[0123] The photocationically curable component (I) preferably contains an epoxy compound that does not contain an aromatic ring as its main component. An epoxy compound that does not contain an aromatic ring is an epoxy compound other than an aromatic epoxy compound, and is hereinafter referred to as an aliphatic epoxy compound. An "epoxy compound" is a compound having at least one epoxy group in the molecule. The aliphatic epoxy compound that is the main component may contain two or more epoxy compounds. "Main component" means that the content of the aliphatic epoxy compound is 50% by mass or more in 100% by mass of the photocurable adhesive. The content of the aliphatic epoxy compound is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0124] The aliphatic epoxy compound may be an epoxy compound having an alicyclic ring, or an epoxy compound having only a linear hydrocarbon structure and / or a branched hydrocarbon structure without containing an alicyclic ring. The aliphatic epoxy compound may contain an unsaturated bond such as a double bond, or may further contain a heteroatom (such as an oxygen atom, a nitrogen atom, a sulfur atom, or a halogen atom) other than the oxygen atom contained in the epoxy group.

[0125] The photocationic polymerization initiator (II) can initiate cationic polymerization upon irradiation with active energy rays, thereby curing the photocationic curable component (I) to form an adhesive layer. The photocationic polymerization initiator (II) generates cationic species or Lewis acids upon irradiation with active energy rays such as visible light, ultraviolet light, X-rays, or electron beams, thereby initiating the polymerization reaction of the photocationic curable component. Because the photocationic polymerization initiator (II) acts catalytically upon exposure to light, it exhibits excellent storage stability and workability even when mixed with the photocationic curable component.

[0126] Examples of the photocationic polymerization initiator (II) include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; and iron-arene complexes.

[0127] Examples of aromatic diazonium salts include benzenediazonium hexafluoroantimonate, benzenediazonium hexafluorophosphate, and benzenediazonium hexafluoroborate.

[0128] Examples of aromatic iodonium salts include diphenyliodonium tetrakis(pentafluorophenyl)borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, and di(4-nonylphenyl)iodonium hexafluorophosphate.

[0129] Examples of aromatic sulfonium salts include triphenylsulfonium hexafluorophosphate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, 4,4-bis[diphenylsulfonio]diphenyl sulfide bishexafluorophosphate, 4,4-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenyl sulfide bishexafluoroantimonate, 4,4-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenyl sulfide bishexafluorophosphate, 7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthone hexafluoroantimonate, 7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthone tetrakis(pentafluorophenyl)borate, and 4-phenylcarbonyl-4-diphenylsulfonio-diphenyl sulfide. hexafluorophosphate, 4-(p-tert-butylphenylcarbonyl)-4-diphenylsulfonio-diphenylsulfide hexafluoroantimonate, 4-(p-tert-butylphenylcarbonyl)-4-di(p-toluyl)sulfonio-diphenylsulfide tetrakis(pentafluorophenyl)borate.

[0130] Examples of iron-arene complexes include xylene-cyclopentadienyliron(II) hexafluoroantimonate, cumene-cyclopentadienyliron(II) hexafluorophosphate, and xylene-cyclopentadienyliron(II) tris(trifluoromethylsulfonyl)methanide.

[0131] The photocationic polymerization initiator (II) may be used alone or in combination of two or more. Among the above, aromatic sulfonium salts are particularly preferred because they have ultraviolet absorption properties even in the wavelength region around 300 nm, and therefore can provide an adhesive layer with excellent curability, good mechanical strength, and good adhesive strength.

[0132] The content of the photocationic polymerization initiator (II) is preferably 1 to 10 parts by mass, more preferably 2 to 6 parts by mass, per 100 parts by mass of the total photocationic curable component (I). By incorporating 1 part by mass or more of the photocationic polymerization initiator (II), the photocationic curable component (I) can be sufficiently cured, thereby imparting high mechanical strength and adhesive strength to the resulting polarizing plate. On the other hand, if the content is too high, the amount of ionic substances in the cured product increases, which may increase the hygroscopicity of the cured product and reduce the durability of the polarizing plate. Therefore, the content of the photocationic polymerization initiator (II) is preferably 10 parts by mass or less per 100 parts by mass of the photocationic curable component (I).

[0133] The laminated polyester film of the present invention is mainly used for optical films in general, and examples thereof include base films for optical components such as prism lens sheets, AR (anti-reflection) films, hard coat films, diffusion plates, and shatter-resistant films for LCDs, flat TVs, and CRTs, near-infrared absorbing filters which are components for the front panels of plasma displays, and transparent conductive films for touch panels and electroluminescence, etc. The film can be suitably used for any of these applications.

[0134] Examples of the acrylic resin that can be cured by electron beams or ultraviolet rays for forming the functional layer include a composition containing a (meth)acrylate oligomer, which is a reactive oligomer, and a (meth)acrylate-based monomer, which is a reactive monomer (reactive diluent). Examples of the (meth)acrylate oligomer include compounds in which a reactive (meth)acrylic group is bonded to a (meth)acrylic resin skeleton, polyester acrylate, epoxy acrylate, polyurethane acrylate, silicone acrylate, melamine acrylate, and polyether acrylate. Examples of (meth)acrylate monomers include monofunctional monomers such as ethyl (meth)acrylate and ethylhexyl (meth)acrylate, 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, and neopentyl glycol di(meth)acrylate. If necessary, a third component can be appropriately added, and examples of the third component include relatively low molecular weight polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiolpolyene resins, and polyhydric alcohols.

[0135] In the case of electron beam or ultraviolet ray curable acrylic resins, photopolymerization initiators such as acetophenones, benzophenones, Michler's benzoyl benzoate, α-amyloxime ester, tetramethylthiuranium monosulfide, and thioxanthones can be used in the resin. Also, the photopolymerization initiator can be mixed with a photosensitizer such as n-butylamine, triethylamine, or tri-n-butylphosphine.

[0136] Silicone (siloxane) thermosetting resins can be produced by hydrolysis and condensation reactions of a single organosilane compound or a mixture of two or more compounds in the presence of an acid or base catalyst. In particular, for low reflectance applications, it is more advantageous to hydrolyze and condense the mixture of one or more fluorosilane compounds in order to improve low refractive index, contamination resistance, etc.

[0137] Manufacturing of Laminated Polyester Films A laminated polyester film can be manufactured by providing a functional layer on the coating layer of the highly adhesive polyester film of the present invention. Specific embodiments are described below, but the present invention is not limited to these. For example, the present invention can provide the following embodiment: A method for manufacturing a highly adhesive polyester film, comprising the step of applying a coating layer-forming composition to at least one surface of a polyester film substrate, wherein the coating layer-forming composition contains a polycarbonate polyurethane resin (A), a polyester resin (B), and a blocked isocyanate-based crosslinking agent (C), and further contains particles. Each component is as described herein.

[0138] In one aspect, the present invention provides a laminated polyester film having a functional layer on a coating layer of an adhesive polyester film. A functional layer-forming composition (functional layer-forming coating liquid) is applied to the coating layer surface of the adhesive polyester film. Examples of the functional layer-forming composition include the electron beam or ultraviolet curable acrylic resin (including its oligomer, monomer, etc.) or a siloxane-based thermosetting resin. When a coating layer is provided on both sides of the adhesive polyester film, the functional layer-forming coating liquid can be applied to at least one of the coating layer surfaces. The functional layer-forming coating liquid does not need to be diluted, but diluting it with an organic solvent is not particularly problematic, depending on the viscosity, wettability, coating thickness, etc. After applying the functional layer-forming coating liquid to the film, the coating film can be dried as needed and then cured by electron beam or ultraviolet radiation and heating according to the curing conditions to form a functional layer.

[0139] More typically, the functional layer-forming coating solution having the above-described composition is applied onto the coating layer of the highly adhesive polyester film using a wire bar or the like, and the solvent can be removed by drying, for example, at 60 to 100°C for 0.5 to 10 minutes. Next, the film coated with the functional layer is irradiated with 300 mJ / cm using, for example, a high-pressure mercury lamp. ２ By irradiating the film with ultraviolet light, a laminated polyester film having a functional layer can be obtained.

[0140] In the present invention, the thickness of the functional layer is preferably 1 to 15 μm. When the thickness of the functional layer is 1 μm or more, the effects of the functional layer on chemical resistance, scratch resistance, stain resistance, etc. are efficiently exhibited, which is preferable. On the other hand, when the thickness is 15 μm or less, the flexibility of the functional layer is maintained, and there is no risk of cracks, etc., being therefore preferable.

[0141] The highly adhesive polyester film and laminated polyester film of the present invention are preferably highly transparent because they can be used primarily for optical applications. The lower limit of the haze is ideally 0%, and the closer to 0%, the more preferable. The upper limit of the haze is preferably 2%. A haze of 2% or less is preferable because it provides good light transmittance and allows clear images to be obtained in liquid crystal display devices. The haze can be measured, for example, according to the method described in the Examples below.

[0142] (Evaluation of Particle Shedding Properties) In a particle shedding test, the highly adhesive polyester film of the present invention exhibits a particle shedding amount of less than 30% within the observation field. Because the particle shedding amount is less than 30%, the highly adhesive polyester film of the present invention can maintain high adhesion between the particles and the resin within the coating layer, preventing particles from shedding in the coating layer and preventing damage to the contact surface caused by the fallen particles. For example, the particle shedding amount may be, for example, 0.1% to 28% or 0.5% to 27% or more, or even 1.0% to 26%. By ensuring that the particle shedding amount is within such a range, damage to the contact surface caused by fallen particles can be prevented and good slip properties can be maintained. Here, the particle shedding property test of the present invention can be performed using the method described below. This method allows for evaluation of particle shedding properties, taking into account the friction and pressure between the coating layer and the contact surface, for example, when the film is wound into a roll during film production of a film having a coating layer and post-processing such as the addition of a functional layer.

[0143] The scratch resistance of a polyester film to the opposite side of the polyester film can be evaluated by the method described in the Examples. Specifically, a highly adhesive polyester film is attached to a friction fastness tester (RT-200, manufactured by Daiei Scientific Instruments Co., Ltd.) with the highly adhesive layer facing up, and a low-reflection-treated film is used at the contact point between the load head (2 cm x 2 cm, 200 g) and the sample film. The film is then reciprocated 10 times over a distance of 10 cm at a speed of 2 seconds per reciprocation. Here, the evaluation according to the present invention is performed under a constant load, generating friction, which can be used to estimate the effect, for example, when winding a film roll. After the friction test, the obtained sample film is observed using a scanning electron microscope (magnification: 3000x), and the number of particles X (pieces) within the field of view is counted. The amount of particles that fell off (%) is calculated from the number of particles Y (pieces) within the same field of view before evaluation using formula (1): X / Y × 100 (%) Formula (1)

[0144] For example, the difference in film haze (ΔHAZE) before and after the particle shedding test is less than 0.55%. The difference in film haze may be, for example, 0.10% to 0.50%, or 0.15% to 0.45%, and is preferably 0.20% to 0.40%. When the film haze difference is within this range, damage to the contact surface caused by fallen particles can be prevented, and good slip properties and blocking resistance can also be maintained.

[0145] Next, the present invention will be described in detail using examples and comparative examples, but the present invention is not limited to the following examples, etc. Furthermore, the measurement methods used in the present invention are as follows.

[0146] (1) Average particle size [Measurement method using a scanning electron microscope] The average particle size of particles present in a coating layer was measured by the following method: Particles were photographed using a scanning electron microscope (SEM), and the maximum diameters (the distance between the two most distant points) of 300 to 500 particles were measured at a magnification such that the size of the smallest particle was 2 to 5 mm, and the arithmetic mean of these was taken as the average particle size.

[0147] [Dynamic Light Scattering] The average particle size of particles was measured by dynamic light scattering during particle production and film production. The sol was diluted with a dispersion medium, and measurements were performed using a submicron particle analyzer N4 PLUS (manufactured by Beckman Coulter) using the parameters of the dispersion medium. The average particle size was then calculated using the cumulant method. In dynamic light scattering, the average particle size of particles in the sol was observed, and if particles aggregated, the average particle size of the aggregated particles was observed.

[0148] (2) Haze of Optical Adhesive Polyester Film The haze of the adhesive polyester film was measured in accordance with JIS K 7136:2000 using a turbidity meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH2000).

[0149] (3) Haze of polyester film before and after scratch resistance evaluation The difference in film haze (ΔHAZE) before and after the particle shedding test was calculated using the following formula (2): ΔHAZE=A(%)-B(%) (2) A(%): Film haze before the particle shedding test B(%): Film haze after the particle shedding test

[0150] (Evaluation of particle shedding) An easy-adhesion polyester film was attached to a friction fastness tester (RT-200, manufactured by Daiei Scientific Instruments Co., Ltd.) with the easy-adhesion layer facing up, and a film with a low-reflection surface was used at the contact point between the load head (2 cm x 2 cm, 200 g) and the sample film, and the film was reciprocated 10 times over a distance of 10 cm at a speed of 2 seconds per reciprocation. After the friction test, the obtained film was observed with a scanning electron microscope (magnification: 3000x), and the number of particles X (pieces) within the field of view was counted. The amount of shedding (%) was calculated from the number of particles Y (pieces) within the same field of view before evaluation using formula (1): X / Y x 100 (%) Formula (1)

[0151] (Evaluation of Scratch Resistance) The low-reflection surface-treated films obtained in the above particle shedding test were observed under an optical microscope (50x magnification), and the scratch resistance was judged as follows: ⊚: Number of scratches after particle shedding test was less than 2 ◯: Number of scratches after particle shedding test was 2 or more but less than 5 △: Number of scratches after particle shedding test was 5 or more but less than 8 ×: Number of scratches after particle shedding test was 8 or more Here, scratches were defined as the number of scratches of 10 mm or more in the reciprocating direction of the load head.

[0152] (Evaluation of Blocking Resistance) Two pairs of samples were cut out into 10 cm x 5 cm squares, and the test surfaces were stacked together, and then a pressure of 1 kg / cm was applied to the center. ２ After leaving the samples in an oven at 50°C for 24 hours while applying a load, the state of the two samples when peeled off was judged according to the following evaluation criteria. The test was carried out five times for each sample. ◎: No noise was made when peeled off and no peeling marks were left. ○: A slight noise was made when peeled off but no marks were left. △: No noise was made when peeled off and marks were left on part or all of the surface. ×: No peeling.

[0153] (4) Reduced Viscosity ηsp / c (unit: dl / g) 0.10 g of polyester resin was dissolved in 25 ml of a mixed solvent of phenol / tetrachloroethane (mass ratio 6 / 4), and the reduced viscosity was measured at 30° C. using an Ubbelohde viscometer.

[0154] (5) Cross-sectional observation by transmission electron microscope The highly adhesive polyester film was cut into 1 mm x 10 mm pieces and embedded in epoxy resin. Then, a cross-sectional thin section parallel to the short side of the embedded sample piece was prepared using an ultramicrotome. The thin section was then stained with ruthenium tetroxide, and a significantly undamaged portion was observed using a transmission electron microscope (JEOL JEM2100) at an accelerating voltage of 200 kV and a magnification of 20,000 times. From the observed images of the coating layer, the thickness of the coating layer was measured at 10 points for each level, and the average value was taken as the thickness of the coating layer.

[0155] (6) Polyester Resin Composition Polyester resin was dissolved in deuterated chloroform, and the resulting mixture was analyzed using a Varian Gemini-200 nuclear magnetic resonance analyzer (NMR). １ H-NMR analysis was carried out and the molar percentage of each component was determined from the integral ratio.

[0156] (7) Viscosity of Polyester Resin Dispersion A polyester resin aqueous dispersion was placed in a 140 cc glass bottle, and the bottle was placed in a thermostatic bath at 25° C. using a viscometer model BL (TOKIMEC INC.) with a No. 1 or No. 2 rotor. Measurement was carried out at a rotation speed of 60 rpm for 1 minute to measure the viscosity of the polyester resin aqueous dispersion.

[0157] [Polycarbonate polyurethane resin] Synthesis of polycarbonate polyurethane resin (PCPU-1): In a four-neck flask equipped with a stirrer, a Dimroth condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 28.0 parts by mass of 4,4'-diphenylmethane diisocyanate, 63.6 parts by mass of a polycarbonate diol with a melting point of 33 ° C., mainly made from 1,4-butanediol / 1,6-hexanediol (= 75 / 25 (molar ratio)) having a number average molecular weight of 1000, 7 parts by mass of dimethylolpropionic acid, and 200 parts by mass of ethyl methyl ketone as a solvent were added, and the mixture was stirred for 3 hours at 75 ° C. under a nitrogen atmosphere. The infrared spectrum of the reaction solution was measured, and the disappearance of the isocyanate groups in the reaction solution was confirmed. Next, the solution was cooled to room temperature, and 8.2 parts by mass of triethylamine was added to obtain a polycarbonate polyurethane resin (PCPU-1) solution with a solids content of 50.0% by mass. The proportion (content) of cyclohexane ring structures in the entire polycarbonate polyurethane resin (PCPU-1) was 0.0 mass %, and the proportion (content) of methylene chain structures having 5 to 10 carbon atoms was 11.3 mass %.

[0158] Preparation of water dispersion (PCPU-1WD) of polycarbonate polyurethane resin (PCPU-1): A predetermined amount of water was added to a reaction vessel equipped with a homodisperser capable of high speed stirring, and the temperature was adjusted to 25°C. The mixture was stirred for 2000 min. －１ While stirring and mixing at 50°C, the polycarbonate polyurethane resin (PCPU-1) solution was gradually added to disperse it in water. The solvent, ethyl methyl ketone, was then removed under reduced pressure. The concentration was adjusted with water to prepare an aqueous dispersion (PCPU-1WD) of polycarbonate polyurethane resin (PCPU-1) with a solids content of 35.0% by mass.

[0159] Synthesis of polycarbonate polyurethane resin (PCPU-2) and preparation of aqueous dispersion (PCPU-2WD): The main raw material of the polycarbonate diol was changed to 1,4-cyclohexanedimethanol / 1,6-hexanediol (= 75 / 25 (molar ratio)) instead of 1,4-butanediol / 1,6-hexanediol (= 75 / 25 (molar ratio)), except that PCPU-2 was prepared in the same manner as in the synthesis of PCPU-1, and an aqueous dispersion (PCPU-2WD) was obtained in the same manner as in the preparation of PCPU-1WD. The proportion (content) of cyclohexane ring structures in this polycarbonate polyurethane resin (PCPU-2) as a whole was 29.1% by mass, and the proportion (content) of methylene chain structures having 5 to 10 carbon atoms was 8.5% by mass.

[0160] [Polyester Resin] Production of Polyester Resin (PEs-1): Polyester resin (PEs-1) was polymerized according to a known polymerization method. The composition of the obtained polymer was: １ H-NMR analysis was performed, and the mole percentage ratio of each component was determined from the integral ratio. The results are shown in Table 1. The reduced viscosity of the resulting polyester resin was 0.583 dl / g. The abbreviations shown in Table 1 are as follows: TPA: terephthalic acid IPA: isophthalic acid CHMM: cyclohexylmethylmalonic acid DSS: dimethyl-5-sodium sulfoisophthalate EG: ethylene glycol HD: 1,6-hexanediol DEG: diethylene glycol NPG: neopentyl glycol CHDM: 1,4-cyclohexanedimethanol The proportion (content) of cyclohexane ring structures in the entire polyester (PEs-1) was 12.6% by mass, and the proportion (content) of methylene chain structures having 5 to 10 carbon atoms was 0.0% by mass.

[0161] Preparation of polyester aqueous dispersion (PEs-1WD): 30 parts by mass of copolymer polyester resin (PEs-1) and 15 parts by mass of ethylene glycol-n-butyl ether were placed in a reactor equipped with a stirrer, thermometer, and reflux device, and the mixture was heated to 110°C and stirred to dissolve the resin. After the resin was completely dissolved, 55 parts by mass of water was gradually added to the polyester solution while stirring. After the addition, the liquid was cooled to room temperature while stirring to produce a milky white polyester resin (PEs-1) aqueous dispersion (PEs-1WD) with a solids content of 25.1% by mass. The liquid viscosity of the resulting aqueous dispersion was 84 mPa s.

[0162] Production of Polyester Resin (PEs-2) and Preparation of Polyester Water Dispersion (PEs-2WD): A polyester resin (PEs-2) was produced according to a known polymerization method similar to the polymerization of the polyester resin (PEs-1) described above. As with PEs-1, the composition ratio was determined, and the reduced viscosity of the resulting resin was evaluated. The results are shown in Table 1. The proportion (content) of cyclohexane ring structures in the entire polyester (PEs-2) was 12.8% by mass, and the proportion (content) of methylene chain structures having 5 to 10 carbon atoms was 0.0% by mass. A polyester water dispersion (PEs-2WD) was prepared in the same manner as in the preparation of the polyester water dispersion (PEs-1WD) described above. The solids concentration and liquid viscosity were evaluated similarly to those for PEs-1WD. The results are shown in Table 2.

[0163]

[0164]

[0165] [Polyisocyanate Compound] Polyisocyanate Compound (PI-1): A polyisocyanate compound (PI-1) having a biuret structure was produced using dicyclohexylmethane-4,4'-diisocyanate with reference to JP-A-8-225511. The NCO concentration of this polyisocyanate compound was 16.0 wt%. The proportion (content) of cyclohexane ring structures was 37.0 mass%, and the proportion (content) of methylene chain structures having 5 to 10 carbon atoms was 0.0 mass%.

[0166] Polyisocyanate compound (PI-2): A polyisocyanate compound (PI-2) having a biuret structure similar to that of polyisocyanate compound (PI-1) was produced using cyclohexane-1,2-diylbis(methylene)diisocyanate instead of dicyclohexylmethane-4,4'-diisocyanate. The NCO concentration of this polyisocyanate compound was 21.6 wt%. The proportion (content) of cyclohexane ring structures was 50.0 mass%, and the proportion (content) of methylene chain structures having 5 to 10 carbon atoms was 0.0 mass%.

[0167] [Crosslinking Agent] Preparation of Water Dispersion (C-1WD) of Blocked Isocyanate Crosslinking Agent (C-1): 140.1 parts by mass of a polyisocyanate compound (PI-1) having a biuret structure derived from dicyclohexylmethane-4,4'-diisocyanate, 50.0 parts by mass of dipropylene glycol dimethyl ether, and 53.9 parts by mass of 3,5-dimethylpyrazole were added to a flask equipped with a stirrer, thermometer, and reflux condenser, and the mixture was stirred at 70°C for 2 hours under a nitrogen atmosphere. The infrared spectrum of the reaction solution was then measured, and it was confirmed that the absorption of the isocyanate group had disappeared. After cooling to room temperature, 6 parts by mass of polyethylene glycol (n = 12) monolaurate was added, and the mixture was stirred for 2000 min. －１ Water was added while stirring and mixing at 100°C. The concentration was adjusted with water to prepare an aqueous dispersion (C-1WD) of the blocked isocyanate crosslinking agent (C-1) having a solids content of 30.0% by mass. The proportion (content) of cyclohexane ring structures in the solids content of this blocked isocyanate crosslinking agent (C-1) was 26.7% by mass, and the proportion (content) of methylene chain structures having 5 to 10 carbon atoms was 0% by mass.

[0168] Preparation of Water Dispersion (C-2WD) of Blocked Isocyanate Crosslinking Agent (C-2): In the same manner as in the preparation of the water dispersion (C-1WD), a water dispersion (C-2WD) of the blocked isocyanate crosslinking agent (C-2) was prepared using the polyisocyanate compound (PI-2) and the polyisocyanate adduct (PI-4).

[0169] The proportion (content) of cyclohexane ring structures in the solid content of the blocked isocyanate crosslinking agent (C-2) was 32.9% by mass, and the proportion (content) of methylene chain structures having 5 to 10 carbon atoms was 0% by mass.

[0170] Example 1 (Preparation of Coating Solution) A coating solution having the following composition was prepared: Water 43.47 parts by mass Isopropyl alcohol 30.57 parts by mass Silica sol A-1 4.15 parts by mass (silica sol with an average particle size of 100 nm, solid content 4.0% by mass) PCPU-1WD 5.42 parts by mass (solid content 35.0% by mass) PEs-1WD 7.58 parts by mass (solid content 25.1% by mass) C-1WD 8.43 parts by mass (solid content 30.0% by mass) Surfactant 0.05 parts by mass (silicon-based, solid content 10.0% by mass) High-boiling-point solvent 0.34 parts by mass

[0171] (Production of Highly Adhesive Polyester Film) As a raw polymer for the film, PET resin pellets having an intrinsic viscosity of 0.62 dl / g (solvent: phenol / tetrachloroethane = 60 / 40) and containing substantially no particles were dried at 135°C for 6 hours under a reduced pressure of 133 Pa. Thereafter, the pellets were fed into an extruder and melt-extruded into a sheet at about 280°C, followed by rapid cooling and solidification on a rotating cooled metal roll maintained at a surface temperature of 20°C, to obtain an unstretched PET sheet.

[0172] Next, the coating solution was applied to one side of a PET film by roll coating, and then dried at 80°C. After final stretching, the coating amount after drying was 0.12 g / m ２ Subsequently, the film was stretched in the width direction by 4.0 times at 150°C in a tenter, and while the length of the film in the width direction was fixed, it was heated at 230°C and further subjected to a relaxation treatment in the width direction at 230°C to obtain an easily adhesive polyester film having a thickness of 50 µm.

[0173] The thickness of the adhesive coating layer of the obtained adhesive polyester film was 102 nm, and the film haze was 0.66%.

[0174] The particle shedding property of the obtained highly adhesive polyester film was evaluated, and the amount of shedding was 12%.

[0175] [Examples 2 to 3, 5 to 7] Highly adhesive polyester films were obtained in the same manner as in Example 1, except that the polycarbonate polyurethane resin, polyester resin, crosslinking agent, and particles used were changed to the combinations shown in Table 3.

[0176] The obtained highly adhesive polyester film was evaluated in the same manner as in Example 1. The results of the various evaluations are shown in Table 3.

[0177] [Examples 4, 9, 10, 14, and 15] Highly adhesive polyester films were obtained in the same manner as in Example 1, except that the polycarbonate polyurethane resin, polyester resin, and crosslinking agent used were changed to the combinations shown in Table 3, and that silica sol A-2 (average particle size 80 nm, solid content concentration 40.0 mass%) or silica sol A-3 (average particle size 50 nm, solid content concentration 40.0 mass%) was used in addition to silica sol A-1.

[0178] The obtained highly adhesive polyester film was evaluated in the same manner as in Example 1, and then a laminated polyester film having a functional layer was obtained in the same manner as in Example 1. The various evaluation results are shown in Table 3.

[0179] [Examples 8, 11 to 12] Highly adhesive polyester films were obtained in the same manner as in Example 1, except that the polycarbonate polyurethane resin, polyester resin, and crosslinking agent used were changed to the combinations shown in Table 3, and the particles were changed from Silica Sol A-1 to Silica Sol A-4 (average particle size 450 nm, solid content concentration 4.0 mass%), Silica Sol B (average particle size 50 nm, solid content concentration 3.5 mass%), or Particles C (average particle size 300 nm, solid content concentration 20 mass%).

[0180] The obtained highly adhesive polyester film was evaluated in the same manner as in Example 1, and then a laminated polyester film having a functional layer was obtained in the same manner as in Example 1. The various evaluation results are shown in Table 3.

[0181] [Example 13] A highly adhesive polyester film was obtained in the same manner as in Example 1, except that the polycarbonate polyurethane resin, polyester resin, and crosslinking agent used were changed to the combinations shown in Table 3, and particles D (average particle size 45 nm, solid content concentration 13% by mass) were used in addition to silica sol A-1.

[0182] The obtained highly adhesive polyester film was evaluated in the same manner as in Example 1, and then a laminated polyester film having a functional layer was obtained in the same manner as in Example 1. The various evaluation results are shown in Table 3.

[0183] [Comparative Example 1] (Preparation of Coating Solution) A coating solution having the following composition was prepared, and a highly adhesive polyester film was obtained in the same manner as in Example 1. Water 47.63 parts by mass Isopropyl alcohol 33.28 parts by mass Silica sol A-1 4.52 parts by mass (silica sol with an average particle size of 100 nm, solid content concentration 4.0% by mass) PCPU-2WD 5.90 parts by mass (solid content concentration 35.0% by mass) PEs-1WD 8.25 parts by mass (solid content concentration 25.1% by mass) Surfactant 0.05 parts by mass (silicone-based, solid content concentration 10.0% by mass) High-boiling-point solvent 0.37 parts by mass

[0184] The obtained highly adhesive polyester film was evaluated in the same manner as in Example 1, and then a laminated polyester film having a functional layer was obtained in the same manner as in Example 1. The various evaluation results are shown in Table 3.

[0185] [Comparative Example 2] A highly adhesive polyester film was obtained in the same manner as in Example 1, except that the polycarbonate polyurethane resin, crosslinking agent, and particles used were changed to the combinations shown in Table 3, and the same amount of polyvinyl alcohol (manufactured by Kuraray Co., Ltd.) was used instead of the polyester resin.

[0186] The obtained highly adhesive polyester film was evaluated in the same manner as in Example 1, and then a laminated polyester film having a functional layer was obtained in the same manner as in Example 1. The various evaluation results are shown in Table 3.

[0187] [Comparative Examples 3 and 4] A highly adhesive polyester film was obtained in the same manner as in Example 1, except that the polycarbonate polyurethane resin described in Table 3 was removed and replaced with only the polyester resin described in Table 3 in which the amount of the removed polycarbonate polyurethane resin was increased.

[0188] The obtained highly adhesive polyester film was evaluated in the same manner as in Example 1, and then a laminated polyester film having a functional layer was obtained in the same manner as in Example 1. The various evaluation results are shown in Table 3.

[0189]

[0190] The adhesive polyester film of the present invention improves the flexibility of the coating layer and maintains high adhesion to the lubricant particles, thereby preventing particles from falling off the coating layer and preventing damage to the contact surface caused by the fallen particles. Therefore, during post-processing such as film formation and functional layer application of a film having a coating layer, such as when the film is wound into a roll, scratches on the surface opposite the contact surface with the coating layer can be prevented, and scratches on the functional layer formed on the opposite surface can also be prevented. Furthermore, because the film has excellent blocking resistance and transparency, it can be widely used in optical applications, etc.

[0191] On the other hand, Comparative Example 1 did not contain the blocked isocyanate crosslinking agent (C), so scratches occurred on the surface opposite to the contact surface of the coating layer, and scratches were also formed in the functional layer formed on the opposite surface. Comparative Example 2 did not contain the polyester resin (B), so scratches occurred on the surface opposite to the contact surface of the coating layer, and scratches were also formed in the functional layer formed on the opposite surface. Comparative Examples 3 and 4 did not contain the polycarbonate polyurethane resin (A), so scratches occurred on the surface opposite to the contact surface of the coating layer, and scratches were also formed in the functional layer formed on the opposite surface.

[0192] The highly adhesive polyester film of the present invention improves the flexibility of the coating layer and maintains high adhesion to lubricant particles, thereby preventing particles from falling off the coating layer and preventing damage to the contact surface caused by the fallen particles. It also has excellent blocking resistance and transparency. Therefore, it can be widely used in optical applications, etc.

Claims

1. A highly adhesive polyester film having a polyester film substrate and a coating layer, wherein the coating layer is formed from a composition containing a polycarbonate polyurethane resin (A), a polyester resin (B), a blocked isocyanate crosslinking agent (C), and particles, and wherein in a particle shedding test, the amount of particles shedding within the observation field is less than 30%.

2. The highly adhesive polyester film according to claim 1, wherein the difference in film haze before and after the particle shedding test is less than 0.55%.

3. The highly adhesive polyester film according to claim 1, wherein the polycarbonate polyurethane resin (A) has a structure represented by formula (1) in the molecule. (In the formula, * represents a binding site, and n represents an integer of 5 to 10.) 4. The highly adhesive polyester film according to claim 1, wherein the polyester resin (B) is a polyester resin having a structure represented by formula (1) in the molecule. (In the formula, * represents a binding site, and n represents an integer of 5 to 10.) 5. A method for producing the highly adhesive polyester film according to any one of claims 1 to 4, comprising a step of applying a coating layer-forming composition to at least one surface of a polyester film substrate, the coating layer-forming composition comprising a polycarbonate polyurethane resin (A), a polyester resin (B), a blocked isocyanate crosslinking agent (C), and particles, the polycarbonate polyurethane resin (A) having a structure represented by formula (1) in its molecule, (wherein * represents a bonding site, and n represents an integer of 5 to 10). The polyester resin (B) has a structure represented by formula (1) in the molecule, (In the formula, * represents a bonding site, and n represents an integer of 5 to 10.) The blocked isocyanate crosslinking agent (C) has a structure represented by formula (1) in the molecule: (wherein * represents a bonding site, and n represents an integer of 5 to 10.) A method for producing an easily adhesive polyester film.

6. A laminated polyester film having a functional layer on the coating layer of the highly adhesive polyester film according to claim 1.

7. A method for producing the laminated polyester film described in claim 6, comprising a step of applying a composition for forming a functional layer to the coating layer surface of the highly adhesive polyester film described in any one of claims 1 to 4.

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