Laminated polyester film

Abstract

To provide a laminated polyester film which has less defects such as a coating spot in manufacture of a coating film, and is excellent in transparency and adhesion of the coating film, and to provide a laminated polyester film which has good adhesion to various coating materials, a resin, a UV curable resin or ink, especially, is excellent in adhesion to the UV curable resin, and is excellent in maintenance of an adhesion at a high level over a long period and moist heat resistance relating to adhesion.SOLUTION: A laminated polyester film has a coating layer on at least one surface of a polyester film base material, wherein the coating layer is formed by containing a composition containing a polyester resin, and an isocyanate-based crosslinking agent having a carboxyl group salt of two kinds of amine compounds having a boiling point of lower than 150°C and a boiling point of 150°C or higher.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a laminated polyester film. More specifically, it relates to a laminated polyester film having an easily adhering coating layer that is optimal for all fields, including optics, packaging, and labeling.

[0002] Thermoplastic resin films, particularly polyester films, are widely used in magnetic recording materials, packaging materials, solar cell applications, flat-panel displays, and other optical films such as anti-reflective films, diffusion sheets, and prism sheets, as well as label printing films, due to their excellent mechanical, electrical, dimensional stability, transparency, and chemical resistance. However, polyester films have a drawback in that their surface is highly crystalline, resulting in poor adhesion to various paints, resins, UV-curable resins, or inks during processing for these applications.

[0003] For this reason, various methods have been studied to impart adhesion to the surface of polyester films. One well-known method involves applying an aqueous dispersion of a resin having hydrophilic groups such as sulfonic acid groups to the surface of a polyester film to create a coating layer with easy adhesion properties (see Patent Document 1). Furthermore, market demands require the maintenance of adhesion even in high-temperature and high-humidity environments (heat and humidity resistance), and the combined use of a resin having hydrophilic groups and a crosslinking agent is being considered (see Patent Document 2). In particular, organotin compounds such as dibutyltin dilaurate are known to be effective catalysts for isocyanate-based crosslinking agents, and their use is known to improve the crosslinking effect. However, organotin compounds such as dibutyltin dilaurate are difficult to use due to environmental hormone concerns (see Patent Document 3). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 1727 / 1983 [Patent Document 2] Japanese Patent Publication No. 2011-133890 [Patent Document 3] International Publication No. 2015 / 052821 [Overview of the project] [Problems that the invention aims to solve]

[0005] As laminated polyester films are used in a variety of applications and operating environments, the aforementioned resistance to moisture and heat has become increasingly important in recent years, and high quality is also required. However, conventional laminated polyester films have not met market expectations in terms of moisture and heat resistance and quality.

[0006] This invention was made against the backdrop of the problems of the prior art. Specifically, the object of this invention is to provide a laminated polyester film that has fewer defects in the coating film, such as uneven coating during manufacturing, and has excellent transparency and adhesion of the coating film, and that has good adhesion to various paints, resins, UV-curable resins or inks, and is particularly excellent in adhesion to UV-curable resins, and that maintains a high level of adhesion over a long period of time and has excellent resistance to humidity and heat related to adhesion. [Means for solving the problem]

[0007] In the process of investigating the above-mentioned problems, the inventors discovered that the hydrophilic behavior of the coating solution changes during heating and drying depending on the type of base component paired with the carboxyl group in the carboxyl salt used as the hydrophilic group of the crosslinking agent in the coating solution. This causes the crosslinking agent to become unevenly distributed or aggregated in the coating layer, resulting in defects such as uneven coating and a decrease in performance such as transparency or adhesion of the coating film. As a countermeasure, the inventors discovered that the problems in the present invention can be solved by mainly using two specific amine compounds as the base pair for the carboxyl group of the crosslinking agent, leading to the completion of the present invention.

[0008] In other words, the present invention consists of the following configuration. 1. A laminated polyester film comprising a coating layer on at least one side of a polyester film substrate, wherein the coating layer is formed from a composition containing a polyester resin and an isocyanate-based crosslinking agent having carboxyl salts of two amine compounds having boiling points of less than 150°C and 150°C or higher. 2. The laminated polyester film according to the first description, wherein the amine compound having a boiling point of 150°C or higher has one or more hydroxyl groups. 3. The laminated polyester film according to the first or second description above, wherein the boiling point difference between the two amine compounds is 70°C or more. [Effects of the Invention]

[0009] The laminated polyester film of the present invention has few coating defects and excellent transparency, adhesion, and heat and humidity resistance of the coating film, making it suitable for use as an easily adhesive film with good adhesion to UV-curable resins such as hard coat films for optical or building materials, and UV-curable inks such as printing films. [Modes for carrying out the invention]

[0010] (Polyester film substrate) In the present invention, the polyester resin constituting the polyester film substrate is polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polytrimethylene terephthalate, etc., as well as a copolymerized polyester resin in which a part of the diol component or dicarboxylic acid component of the above-mentioned polyester resin is replaced with the following copolymer components. For example, the copolymer components can include diol components such as diethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, and polyalkylene glycol, and dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, 5-sodium sulfisoisophthalic acid, 2,6-naphthalenedicarboxylic acid, and 2,5-franzicarboxylic acid.

[0011] In the present invention, the polyester resins suitably used for the polyester film substrate are mainly selected from polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, and polyethylene furanolate. Among these polyester resins, polyethylene terephthalate is the most preferred in terms of the balance between physical properties and cost. Furthermore, the polyester film substrate composed of these polyester resins is particularly preferably a stretched polyester film stretched in at least one axial direction, as stretching can improve chemical resistance, heat resistance, mechanical strength, and other properties.

[0012] While there are no particular limitations on the catalyst used for polycondensation in the production of polyester resins, antimony trioxide is preferred because it is inexpensive and has excellent catalytic activity. Germanium compounds or titanium compounds are also preferred. Even more preferred polycondensation catalysts include catalysts containing aluminum and / or its compounds and phenolic compounds, catalysts containing aluminum and / or its compounds and phosphorus compounds, and catalysts containing aluminum salts of phosphorus compounds.

[0013] Furthermore, the polyester film substrate in the present invention is not particularly limited in terms of its layer structure. It may be a single-layer polyester film, a two-layer structure with different components, or a polyester film substrate consisting of at least three layers, including an outer layer and an inner layer.

[0014] (Coated layer) In order to reduce coating film defects and improve the transparency and adhesiveness of the coating film, it is preferable that the laminated polyester film of the present invention has a coating layer formed from a composition containing a polyester resin and an isocyanate crosslinking agent having a carboxylate salt formed from two amine compounds, one having a boiling point of less than 150°C and the other having a boiling point of 150°C or higher, the coating layer being laminated on at least one surface of the polyester film. The coating layer may be provided on both surfaces of the polyester film, or depending on the application, may be provided only on one surface of the polyester film, and a different resin coating layer may be provided on the other surface.

[0015] The carboxyl group of the crosslinking agent used in the coating layer forms a salt with an amine compound, which improves hydrophilicity, and as a result, the crosslinking agent can stably exist as an emulsion in an aqueous solvent. In addition, when heated during processes such as drying of the coating liquid, the amine compound with a relatively low boiling point desorbs from the carboxylate salt and volatilizes, regenerating carboxyl groups with low hydrophilicity, thereby improving the moist heat resistance after coating film formation. However, when an amine compound with a relatively low boiling point is used, volatilization of the amine compound itself occurs earlier than the drying step of the coating liquid caused by volatilization of the aqueous solvent, so the hydrophilicity of the crosslinking agent decreases in the coating liquid during drying, which easily causes aggregation due to destabilization of the crosslinking agent emulsion itself in the aqueous solvent or uneven distribution in the coating film. Such aggregation or uneven distribution leads to coating film defects or coating film unevenness, thereby reducing coating film quality.

[0016] As a result of studying improvements to the aforementioned problems, the inventors have found that the problems can be solved by a coating layer mainly formed from a composition containing a polyester resin and an isocyanate crosslinking agent having a carboxylate salt formed from two amine compounds, one having a boiling point of less than 150°C and the other having a boiling point of 150°C or higher. That is, the amine compound having a boiling point of less than 150°C volatilizes in the drying step, which reduces hydrophilicity, thereby improving moist heat resistance, while the amine compound having a boiling point of 150°C or higher suppresses the rate of change in hydrophilicity during the drying step, thereby making it possible to reduce the occurrence of coating film defects or spots caused by aggregation or uneven distribution. Furthermore, these two types of amine compounds appropriately adjust the hydrophilicity of the crosslinking agent and improve compatibility with the polyester resin, thereby improving coating film properties such as adhesion. Accordingly, these effects make it possible to achieve both high coating film quality and performance at the same time.

[0017] (Isocyanate-based crosslinking agent) In the present invention, it is preferable to use, in the coating layer, an isocyanate-based crosslinking agent having a carboxyl group salt formed from two types of amine compounds, one with a boiling point of less than 150°C and the other with a boiling point of 150°C or higher. Use of these crosslinking agents makes it possible to further improve the performance of the coating layer such as quality, adhesion, and moist heat resistance.

[0018] There are no particular limitations on the method for introducing a carboxyl group salt into an isocyanate-based crosslinking agent, but the product can be obtained by reacting a monool or polyol having a carboxyl group with a polyisocyanate, then neutralizing the carboxyl group with an amine, or by previously converting the carboxyl group into a salt and then carrying out the same reaction.

[0019] Examples of such monools or polyols include glycolic acid, lactic acid, tartaric acid, citric acid, oxybutyric acid, oxyvaleric acid, hydroxypivalic acid, dimethylolacetic acid, dimethylolpropionic acid, dimethylolbutanoic acid, polycaprolactone having a carboxyl group, and salts thereof.

[0020] In the present invention, the reactive group of the isocyanate-based crosslinking agent is preferably a blocked isocyanate from the viewpoint of storage stability in aqueous solvents. These blocked isocyanates are obtained by reacting an isocyanate group with a blocking agent. The dissociation temperature of the blocked isocyanate is preferably 180°C or lower, more preferably 150°C or lower, and even more preferably 130°C or lower. The blocking agent dissociates from the functional group by heat addition during the drying process after coating the coating solution or, in the case of the in-line coating method, during the film formation process, generating a regenerated isocyanate group. As a result, the crosslinking reaction with the polyester resin proceeds, improving adhesion at room temperature and under high temperature and high humidity conditions. When the dissociation temperature of the blocked isocyanate is below the above temperature, the dissociation of the blocking agent proceeds sufficiently, resulting in good adhesion, especially heat and humidity resistance. The lower limit of the dissociation temperature is not particularly limited as long as it is above room temperature to stabilize the coating solution, but it is preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 80°C or higher.

[0021] Examples of blocking agents with a dissociation temperature of 130°C or lower include bisulfite compounds such as sodium bisulfite, imidazole compounds such as imidazole, 2-methylimidazole, 4-methylimidazole, and 2-ethylimidazole, imidazoline compounds such as 2-methylimidazole, guanidine compounds such as 1,1,3,3-tetramethylguanidine, pyrazole compounds such as 3,5-dimethylpyrazole, active methylene compounds such as malonic acid diesters (dimethyl malonate, diethyl malonate, di-n-butyl malonate, di-2-ethylhexyl malonate), and oxime compounds such as acetooxime and methyl ethyl ketoxime.

[0022] Examples of polyisocyanate compounds include polyisocyanate monomers and polyisocyanate derivatives. Examples of polyisocyanate monomers include aromatic polyisocyanates, aromatic aliphatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, and 3,3'-dimethoxydiphenyl-4,4'-diisocyanate. Examples of aromatic aliphatic polyisocyanates include 1,3- or 1,4-xylylene diisocyanate, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene, and ω,ω'-diisocyanato-1,4-diethylbenzene. Examples of aliphatic polyisocyanates include 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate. Examples of alicyclic polyisocyanates include 1,3-cyclopentane diisocyanate, cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, methylenebis(cyclohexyl isocyanate), norbornane diisocyanate, and bis(isocyanatomethyl)cyclohexane. These polyisocyanate monomers can be used individually or in combination of two or more types. Examples of polyisocyanate derivatives include polymers of the polyisocyanate monomers mentioned above (e.g., dimers, trimers (e.g., isocyanurate modified products), adduct modified products (e.g., polyol modified products (alcohol adducts) produced by the reaction of polyisocyanate monomers with low molecular weight polyols described later), allophanate modified products, biuret modified products, uretdione modified products, and uretonimine modified products. In the present invention, aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic aliphatic polyisocyanates are preferred as polyisocyanates, and isocyanurate-modified, adduct-modified, and biuret-modified polyisocyanate derivatives are particularly preferred. In the present invention, the crosslinking agent preferably has two or more isocyanate groups in one molecule, and more preferably three or more.

[0023] In the present invention, it is preferable that the isocyanate-based crosslinking agent has a carboxyl group in its molecule, and the amount of carboxyl group present is preferably 15 mg KOH / g or more, more preferably 20 mg KOH / g or more, and even more preferably 25 mg KOH / g or more, as an acid value of the isocyanate-based crosslinking agent. Having a carboxyl group with an acid value of 15 mg KOH / g or more makes it possible to maintain a certain level of hydrophilicity, and as a result, stability in aqueous solvents is improved. Details of the two amine compounds used to form the carboxyl base salt in the present invention, one with a boiling point below 150°C and the other with a boiling point above 150°C, will be described later. The isocyanate-based crosslinking agent in the present invention may have hydrophilic groups other than carboxyl groups or carboxyl salts. Examples of other hydrophilic groups include cationic groups such as quaternary amines, anionic groups such as sulfonic acid and phosphinic acid, and nonionic groups such as polyoxyalkylene groups, but nonionic groups such as polyoxyalkylene groups are preferred. Nonionic groups can be easily incorporated into molecules by the reaction of a nonionic hydrophilic group-containing compound with an isocyanate group. Examples of nonionic hydrophilic group-containing compounds include polyoxyalkylene alkyl ethers: polyethylene glycol, polyethylene glycol monomethyl ether, etc. The number average molecular weight of these compounds is preferably 400 to 4000, and most preferably 400 to 1000.

[0024] The crosslinking agent content of the isocyanate-based crosslinking agent, which has carboxyl base salts of two amine compounds with boiling points below 150°C and above 150°C, is preferably 5% by mass or more and less than 60% by mass, relative to the total amount of solids of the polyester resin, crosslinking agent and other resins constituting the composition. A crosslinking agent content of 5% by mass or more is preferable from the viewpoint of moisture and heat resistance, and a content of less than 60% by mass is preferable from the viewpoint of adhesion, etc., because the polyester resin content is relatively high. A content of 10% by mass or more and 55% by mass or less is more preferable, and a content of 15% by mass or more and 50% by mass or less is even more preferable.

[0025] (Amine compounds) In this invention, two types of amine compounds are used: one with a boiling point below 150°C and another with a boiling point of 150°C or higher. In this invention, boiling point refers to the boiling point at atmospheric pressure (760 mmHg (101.325 kPa)), and there is no problem in using known data such as literature values. If there is a range in boiling points, there is no problem in using the median value of that range. Furthermore, if the known data only includes the boiling point under reduced pressure and the boiling point at atmospheric pressure is unknown, there is no particular problem in substituting it with a value converted from a boiling point conversion chart (Science of Petroleum, Vol. II. P. 1281 (1938)). Similarly, if the boiling point of the amine compound is sufficiently high and the decomposition temperature is lower than the boiling point, there is no problem in substituting this decomposition temperature as an indicator in place of the boiling point in this invention. In the present invention, amine compounds containing one or more nitrogen atoms in the molecule are usable. Amine compounds containing two or more nitrogen atoms in the molecule are also usable, but it is preferable that they be 10 mol% or less of the total amine compound due to the influence of side reactions such as ionic crosslinking. However, azides are unstable to heat and other factors, so it is preferable not to use them in the present invention. Furthermore, as an amine compound, it is preferable to have fewer hydrogen atoms directly bonded to the nitrogen atom, from the standpoint of preventing deterioration such as oxidation and suppressing reactions with the isocyanate group of the crosslinking agent. For this reason, secondary amines are more preferable than primary amines, and tertiary amines or heterocyclic compounds are even more preferable.

[0026] For amine compounds with a boiling point below 150°C, there is no particular lower limit to the boiling point, but from the viewpoint of the quality of the coating film, a boiling point of 80°C or higher is preferred, and 110°C or higher is particularly preferred. Furthermore, it is preferable that the amine compound is water-soluble. Amine compounds with a boiling point below 150°C include aliphatic monoamine compounds such as ammonia (boiling point -33°C), methylamine (boiling point -6°C), trimethylamine (boiling point 3°C), ethylamine (boiling point 17°C), propylamine (boiling point 48°C), butylamine (boiling point 78°C), isobutylamine (boiling point 68-69°C), pentylamine (boiling point 104°C), hexylamine (boiling point 131-132°C), allylamine (boiling point 96-98°C), cyclohexylamine (boiling point 135°C), and other primary amines. Secondary amines such as dimethylamine (boiling point 7°C), diethylamine (boiling point 56°C), dipropylamine (boiling point 111°C), diisopropylamine (boiling point 84°C), dibutylamine (boiling point 159°C), diisobutylamine (boiling point 137-139°C), dicyclohexylamine (boiling point 135°C), diallylamine (boiling point 111-112°C), ethylpropylamine (boiling point 79°C), and methylbutylamine (boiling point 91°C), Examples of tertiary amines include N,N-dimethylethylamine (boiling point 37°C), N,N-diethylmethylamine (boiling point 62°C), N,N-dimethylisopropylamine (boiling point 68°C), N-butyldimethylamine (boiling point 93°C), triethylamine (boiling point 89°C), N,N-diisopropylethylamine (boiling point 127°C), N,N-methyldiisopropylamine (boiling point 114°C), N,N-dipropylethylamine (boiling point 132°C), tricyclohexylamine (boiling point 135°C), N-butyldimethylamine (boiling point 93°C), N,N-diisopropylethylamine (boiling point 127°C), N-methyl-N-ethylpropylamine (boiling point 92°C), and N-methyldiallylamine (boiling point 111°C).

[0027] Examples of alicyclic monoamine compounds include pyrrolidine (boiling point 87°C), piperidine (boiling point 106°C), 2-azabicyclo[2.2.1]heptane (boiling point 135°C), N-methylpyrrolidine (boiling point 76°C), and N-methylpiperidine (boiling point 107°C). Examples of heterocyclic amine compounds include pyrrole (boiling point 129-131°C) and pyridine (boiling point 115°C).

[0028] In the present invention, amine compounds with a boiling point of less than 150°C may contain atoms other than nitrogen, carbon, or hydrogen. Examples of other atoms include oxygen, sulfur, and halogens, but hydroxyl groups and alkoxy groups containing oxygen are preferred for stability and other reasons. Examples include dimethylethanolamine (boiling point 134°C), methoxyamine (boiling point 50°C), 3-ethoxypropylamine (boiling point 132°C), and methoxy(methyl)amine (boiling point 97°C).

[0029] For amine compounds with a boiling point of 150°C or higher, a boiling point of 190°C or higher is more preferable from the viewpoint of the quality of the coating film, and 240°C or higher is particularly preferable. There are no particular restrictions on the upper limit of the boiling point other than the decomposition temperature mentioned above. In other words, the upper limit of the boiling point of an amine compound with a boiling point of 150°C or higher is the same as the decomposition temperature of the amine compound.

[0030] Examples of amine compounds with a boiling point of 150°C or higher in the present invention include the following compounds. Examples of primary aliphatic monoamine compounds include heptylamine (boiling point 154-156°C), octylamine (boiling point 175-177°C), and dodecylamine (boiling point 259°C). Examples of secondary aliphatic monoamine compounds include dipentylamine (boiling point 203°C), dihexylamine (boiling point 236°C), dioctylamine (boiling point 297-298°C), and didodecylamine (boiling point 265°C / 27mmHg). Examples of tertiary aliphatic monoamine compounds include tripropylamine (boiling point 156°C), tributylamine (boiling point 217°C), triisobutylamine (boiling point 183°C), tripentylamine (boiling point 240°C), trihexylamine (boiling point 265°C), triheptylamine (boiling point 155°C / 5mmHg), trioctylamine (boiling point 367°C), triallylamine (boiling point 156°C), and N,N-dimethylcyclohexylamine (boiling point 160°C).

[0031] Examples of tertiary alicyclic monoamine compounds include quinuclidine (boiling point 198°C) and 2-methyl-2-azabicyclo[2.2.1]heptane (boiling point 198°C). Examples of tertiary monoamine compounds having an aromatic skeleton include dimethylbenzylamine (boiling point 180°C), N-methyldiphenylamine (boiling point 295°C), and N,N-dimethylnaphthylamine (boiling point 274°C).

[0032] Aromatic amine compounds include aniline (boiling point 184°C) and N-methylaniline (boiling point 196°C). Examples include N,N-dimethylaniline (boiling point 193°C) and N,N-diethyl-1-naphthylamine (boiling point 285°C). Among heterocyclic amine compounds, quinoline (boiling point 238°C) and isoquinoline (boiling point 242°C) are examples. Examples include acridine (boiling point 346°C).

[0033] Compounds containing multiple nitrogen atoms in their molecules include N,N,N',N'-tetraethylethylenediamine (boiling point 189-192°C), imidazole (boiling point 256°C), 2-methylimidazole (boiling point 267-268°C), and 1-(2-aminoethyl)-2-methylimidazole (boiling point 274°C ± 23°C), as well as hydrazides such as oxalate dihydrazide (boiling point 221°C), malonic acid dihydrazide (boiling point 554°C ± 33°C), succinate dihydrazide (boiling point 540°C ± 33°C), and adipic acid dihydrazide (boiling point 305°C).

[0034] In the amine compounds with a boiling point of 150°C or higher in this invention, there is no problem in containing atoms other than nitrogen, carbon, or hydrogen atoms, similar to amine compounds with a boiling point of less than 150°C. Oxygen atoms are preferred as alkoxy or hydroxyl groups because they enhance the hydrophilicity of the amine compound itself. In particular, in amine compounds with a boiling point of 150°C or higher, it is more preferable that there be one or more hydroxyl groups in the molecule. The presence of hydroxyl groups in the molecule reacts with the isocyanate groups of the crosslinking agent, increasing the crosslinkability in the coating film and improving adhesion and heat and humidity resistance. Furthermore, from the viewpoint of crosslinkability, it is even more preferable that the amine compound contains two or more hydroxyl groups. There is no particular upper limit to the number of hydroxyl groups in the amine compound, but four or fewer is preferable, and three or fewer is also preferable. In addition, from the viewpoint of reactivity with isocyanate groups, secondary hydroxyl groups are more preferable than tertiary hydroxyl groups, and primary hydroxyl groups are most preferable.

[0035] Examples of amine compounds having one or more hydroxyl groups and a boiling point of 150°C or higher include the following compounds. Examples of primary amine compounds having one primary hydroxyl group include monoethanolamine (boiling point 170°C), propanolamine (boiling point 188°C), 4-amino-1-butanol (boiling point 206°C), 2-amino-1-butanol (boiling point 176-178°C), 2-amino-2-methyl-1-propanol (boiling point 165°C), 5-amino-1-pentanol (boiling point 222°C), and 6-amino-1-hexanol (boiling point 225°C).

[0036] Examples of secondary amine compounds having one primary hydroxyl group include N-methylethanolamine (boiling point 156°C), N-ethylethanolamine (boiling point 169°C), N-propylethanolamine (boiling point 182°C), N-isopropylethanolamine (boiling point 171°C), N-butylethanolamine (boiling point 199°C), N-pentylethanolamine (boiling point 219°C), N-decylethanolamine (boiling point 309°C), 2-m-tolylaminoethanol (boiling point 303°C), 2-p-tolylaminoethanol (boiling point 287°C), t-butylaminoethanol (boiling point 90-92°C / 25mmHg), 2-(p-methylbenzyl)aminoethanol (boiling point 303°C), phenylpropanolamine (boiling point 273°C), and 2-piperidinemethanol (boiling point 100°C / 2mmHg).

[0037] Examples of tertiary amine compounds having one primary hydroxyl group include diethylaminoethanol (boiling point 162°C), 2-di(2-ethylhexyl)aminoethanol (boiling point 374°C), N,N-diarylaminoethanol (boiling point 206°C), 5-diethylamino-1-pentanol (boiling point 217°C), 1-methyl-4-piperidinemethanol (boiling point 108°C / 10mmHg), 2-di(2-ethylhexyl)aminoethanol (boiling point 374°C), N,N-diisopropylethanolamine (boiling point 191°C), N,N-dibutylethanolamine (boiling point 226°C), N,N-dicyclohexylaminoethanol (boiling point 352°C), and N,N-dimethylpropanolamine (boiling point 164°C).

[0038] Examples of primary amine compounds having one secondary hydroxyl group include 1-amino-2-octanol (boiling point 251±13℃), 3-(aminomethyl)-4-heptanol (boiling point 238±13℃), and phenylpropanolamine (boiling point 273℃), while examples of secondary amine compounds having one secondary hydroxyl group include 1-(pentylamino)-2-propanol (boiling point 231±13℃).

[0039] Examples of tertiary amine compounds having one secondary hydroxyl group include 6-(dimethylamino)-2-hexanol (boiling point 198±23℃), 1-[butyl(methyl)amino]-2-propanol (boiling point 202±13℃), 1-dipropylamino-2-butanol (boiling point 223±13℃), 4-(diethylamino)-3-methyl-2-butanol (boiling point 227±13℃), and 1-(dimethylamino)-2-pentanol (boiling point 181±13℃).

[0040] Examples of primary amine compounds having one tertiary hydroxyl group include 4-(aminomethyl)-4-heptanol (boiling point 244±13℃), 1-amino-2,2,3-trimethyl-3-pentanol (boiling point 225±13℃), 2-amino-3-ethyl-2-methyl-3-pentanol (boiling point 231±13℃), 1-amino-2-methyl-2-octanol (boiling point 262±13℃), 1-amino-2,2,3,4-tetramethyl-3-pentanol (boiling point 238±13℃), and 1-amino-3-ethyl-2,2-dimethyl-3-pentanol (boiling point 244±13℃).

[0041] Examples of secondary amine compounds having one tertiary hydroxyl group include 2-methyl-1-(2-pentanylamino)-2-propanol (boiling point 238±13℃). Examples of tertiary amine compounds having one tertiary hydroxyl group include 2-(dimethylamino)-2-hexanol (boiling point 180±23℃).

[0042] Examples of secondary amine compounds having two primary hydroxyl groups include diethanolamine (boiling point 217°C), diisopropanolamine (boiling point 249°C), diisobutanolamine (boiling point 245°C), and dibutanolamine (boiling point 245°C). Among tertiary amine compounds having two primary hydroxyl groups, N-methyldiethanolamine (boiling point 245°C), N-ethyldiethanolamine (boiling point 251°C), N-propyldiethanolamine (boiling point 263°C), N-isopropyldiethanolamine (boiling point 255°C), N-butyldiethanolamine (boiling point 275°C), Nt-butyldiethanolamine (boiling point 161°C / 22mmHg), N-heptyldiethanolamine (boiling point 327°C), N-octyldiethanolamine (boiling point 481°C), N-phenyldiethanolamine (boiling point 270°C), Nm-trildiethanolamine (boiling point 275°C) Examples include Np-tolyldiethanolamine (boiling point 339°C), N-benzyldiethanolamine (boiling point 226°C), N-cyclohexyldiethanolamine (boiling point 343°C), stearyldiethanolamine (boiling point 260-285°C / 5mmHg), N-lauryldiethanolamine (boiling point 195°C / 3mmHg), tetradecyldiethanolamine (boiling point 429°C), N-hexadecyldiethanolamine (boiling point 455°C), methoxypropyldiethanolamine (boiling point 295°C), and 3-(dimethylamino)-1,2-propanediol (boiling point 217°C).

[0043] Examples of primary amine compounds having three primary hydroxyl groups include tris(hydroxymethyl)aminomethane (boiling point 220°C / 10 mmHg). Examples of tertiary amine compounds having three primary hydroxyl groups include triethanolamine (boiling point 335°C), triisopropanolamine (boiling point 305°C), tributanolamine (boiling point 377°C), and 1-[bis(2-hydroxyethyl)amino]-2-propanol (boiling point 145°C / 0.6 mmHg).

[0044] Examples of tertiary amine compounds having four or more primary hydroxyl groups include bis(2-hydroxyethyl)aminotris(hydroxymethyl)methane (boiling point 466±40℃). Among the tertiary amine compounds having four or more secondary hydroxyl groups, N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine (boiling point 175-181°C) is an example.

[0045] In this invention, two types of amine compounds are used. If we refer to the amine compound with a boiling point below 150°C and the amine compound with a boiling point of 150°C or higher as amine compound (A) and amine compound (B), respectively, the amount of amine compound (A) used is preferably 10-90% and more preferably 15-85% in molar percentage (A / (A+B)) of the sum of amine compounds (A) and (B). A molar ratio of 10% or more is preferable because it provides good heat and humidity resistance of the coating film, and a ratio of 90% or less is preferable from the viewpoint of suppressing the occurrence of coating defects or unevenness. Furthermore, the boiling point difference between amine compound (A) and amine compound (B) is preferably 70°C or more, more preferably 130°C or more, and even more preferably 150°C or more. A boiling point difference of 70°C or more is preferable from the viewpoint of achieving both the quality and performance of the coating film. There is no particular upper limit set for the boiling point difference between amine compound (A) and amine compound (B), but it can be said that it is naturally determined by the decomposition temperature of amine compound (B).

[0046] In the present invention, amine compounds (A) and (B) are preferably used to form the carboxyl base salt of the crosslinking agent solution before aqueous dispersion. However, it is also possible to add amine compound (B) later to an aqueous dispersion consisting of the carboxyl base salt of the crosslinking agent amine compound (A). The carboxyl base salt formed by amine compound (A) dissociates and volatilizes upon heating during coating film preparation, and is sequentially replaced by amine compound (B), which has a higher boiling point. Therefore, the same effect as that of carboxyl base salts formed in advance by amine compounds (A) and (B) can be obtained. As mentioned above, molar ratio is used, but when the exact molecular weight of an amine compound is unknown, for example, in the case of amine compounds derived from natural oils and fats, it is also possible to use the amine value instead of moles as an indicator.

[0047] Other inorganic basic compounds include non-volatile alkali metal elements such as sodium and alkaline earth metal elements such as magnesium. The upper limit of the amount used cannot be determined definitively as it depends on the type and concentration of the coating material, but it can be used without any particular problems as long as it is about 10 mol% or less of the total carboxyl groups of the crosslinking agent in the present invention.

[0048] The amount of amine compounds (A) and (B) added to the aqueous dispersion of the crosslinking agent is preferably in the range of 50-600% (((A)+(B)) / (C)) relative to the total carboxyl groups (C) of the crosslinking agent, more preferably 60-550%, and even more preferably 70-500%. When the range of 50-600% (((A)+(B)) / (C)) is 50-600%, the effects of adhesion and its resistance to humidity and heat are obtained, and no adverse effects on quality or performance due to excessive amine compounds are observed.

[0049] (Crosslinking agent) In the present invention, it is also possible to use crosslinking agents other than those mentioned above. There are no particular restrictions on the type of crosslinking agent to be used in combination, and isocyanate-based, oxazoline-based, carbodiimide-based, epoxy-based, melamine-based, etc., which do not have carboxyl groups can be used. Among these, those having crosslinking groups that have low reactivity with the carboxyl groups of isocyanate-based crosslinking agents are preferred, for example, isocyanate-based, epoxy-based, and melamine-based crosslinking agents that do not have carboxyl groups are preferred.

[0050] (Polyester resin) In the present invention, the polyester resin to be included in the composition that forms the coating layer can be obtained from the reaction of a dicarboxylic acid and a diol. Examples of dicarboxylic acids include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, trimethyladipic acid, pimelic acid, 2,2-dimethylglutaric acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, and itaconic acid; aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, benzylmalonic acid, diphenic acid, 4,4'-oxydibenzoic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid; and alicyclic dicarboxylic acids such as 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and 2,5-norbornanedicarboxylic acid.

[0051] Examples of diols include linear aliphatic diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,9-nonanediol. Propylene glycol, dipropylene glycol, 2,4-dimethyl-2-ethylhexane-1,3-diol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 1,3-butanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,6-hexanediol, and other branched aliphatic diols. Alicyclic diols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, and tricyclodecanedimethanol; Examples include aromatic diols such as 4,4'-methylenediphenol, bisphenol S, bisphenol A, bisphenol fluorene, 4,4'-dihydroxybiphenyl, 2,5-naphthalenediol, and p-xylenediol, or their ethylene oxide and propylene oxide adducts. In addition to the divalent dicarboxylic acids and diols mentioned above, it is possible to use trivalent or higher polycarboxylic acids or polyols as long as they do not cause polymerization abnormalities such as gelation. Examples of trivalent or higher polycarboxylic acids include trimellitic acid, pyromellitic acid, adamantane tricarboxylic acid, and trimesic acid, while examples of trivalent or higher polyols include pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, trimethylolpropane, and trimethylolethane.

[0052] In the present invention, the polyester resin included in the composition forming the coating layer preferably has hydrophilic groups introduced into its molecules in order to impart water dispersibility. Examples of hydrophilic groups include anionic groups represented by carboxyl groups, sulfonic acid groups, and sodium or potassium salts of phosphonic acid groups, and nonionic groups represented by hydroxyl groups, polyoxyalkylene groups, etc. However, in the present invention, anionic groups such as sulfonic acid groups and sodium or potassium salts of phosphonic acid groups are preferred. The amount of these hydrophilic groups is preferably in the range of 0.5 to 6.0 mol%, more preferably 1.0 to 5.0 mol%, and even more preferably 1.2 to 4.0 mol% relative to the total polycarboxylic acid and polyol raw materials. A hydrophilic group content in the range of 0.5 to 6.0 mol% is preferable in terms of coating film quality and performance. There are no particular restrictions on the method of introducing these into the polyester resin, and they can be easily obtained by using dicarboxylic acids or diols having these hydrophilic groups in combination. Furthermore, there are no particular restrictions on the method for forming an aqueous dispersion of polyester resin, but it is preferable to dissolve the resin in a hydrophilic solvent to form a resin solution, and then disperse this resin solution with water while stirring. Also, if the hydrophilic solvent used is removed from the aqueous dispersion by vacuum distillation or the like, it is not a problem to use a nonionic surfactant in combination as long as it is 5% by mass or less of the polyester resin. The molecular weight is preferably in the range of 0.20 to 0.80 dl / g as a reduced viscosity, more preferably 0.30 to 0.75 dl / g, and even more preferably 0.40 to 0.65 dl / g.

[0053] Modified polyester resins can also be used in the coating layer of the present invention. Examples of modified resins include acrylic grafts, acid anhydride adducts, glycol adducts, and caprolactone adducts. Other resins may be used in combination with the polyester resins mentioned above. Examples of other resins include polyurethane resins, acrylic resins, acrylic urethane resins, vinyl acetate, polyvinyl alcohol, and hydroxycellulose, but preferred resins are polyurethane resins and acrylic resins.

[0054] (Polyurethane resin) In the present invention, the polyurethane resin that can be included in the composition for forming the coating layer is a urethane resin derived from at least a polyol component, a polyisocyanate component, and, if necessary, a chain extender. From the viewpoint of water dispersibility, it is preferable to have hydrophilic groups in the molecule or in the side chains. Furthermore, as hydrophilic groups, anionic groups such as sulfonic acid groups, phosphonic acid groups, and carboxyl groups, or nonionic groups represented by polyethylene glycol are preferred. These hydrophilic polyurethane resins can preferably be obtained by using a hydrophilic group-containing polyol component as the main component of the urethane.

[0055] In the present invention, the other polyol components used to synthesize and polymerize the polyurethane resin that can be included in the composition forming the coating layer preferably contain an aliphatic or alicyclic polycarbonate polyol that has excellent heat resistance and hydrolysis resistance. Examples of these polycarbonate polyols include polycarbonate diols and polycarbonate triols, but polycarbonate diols can be preferably used. Aliphatic polycarbonate diols used to synthesize and polymerize the polycarbonate structure urethane resin in the present invention can be obtained by reacting one or more diols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,8-nonanediol, neopentyl glycol, diethylene glycol, and dipropylene glycol with carbonates such as dimethyl carbonate, ethylene carbonate, and phosgene. Alicyclic polycarbonate diols can be obtained similarly by synthesizing and polymerizing diols such as 1,3-cyclopentanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, and cyclohexanediol.

[0056] The number-average molecular weight of the polycarbonate polyol is preferably 300 to 5000. More preferably 400 to 4000, and most preferably 500 to 3000. A number-average molecular weight of 300 or more is preferable because it improves ink adhesion. A number-average molecular weight of 3000 or less is preferable because it improves blocking resistance.

[0057] In the present invention, polyisocyanates used in the synthesis and polymerization of urethane resins that can be included in the composition forming the coating layer include aromatic aliphatic diisocyanates, alicyclic diisocyanates, aliphatic diisocyanates, modified polyisocyanates containing isocyanurate bonds, biuret bonds, or allophanate bonds produced from diisocyanates, and polyisocyanates obtained by pre-adding diisocyanates, either individually or in combination, with trimethylolpropane or the like. When using the aforementioned aromatic aliphatic diisocyanates, alicyclic diisocyanates, or aliphatic diisocyanates, there is no problem of yellowing, which is preferable.

[0058] The polyurethane resin that can be included in the composition forming the coating layer in the present invention may have reactive groups such as blocked isocyanates at its ends or side chains to improve rigidity.

[0059] (Acrylic resin) In the present invention, the acrylic resin that can be included in the composition for forming the coating layer is a copolymer mainly formed from acrylic acid, methacrylic acid, or esters thereof. Various compounds can be used as the acrylic acid or methacrylic acid ester. For example, acrylic acid esters such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate, dodecyl acrylate, cyclohexyl acrylate, isobornyl acrylate, and stearyl acrylate can be used, with the aforementioned acrylic acid replaced by methacrylic acid as the methacrylic acid ester.

[0060] In the present invention, the acrylic resin that can be included in the composition forming the coating layer is preferably in a water dispersion. There are no particular restrictions on the method of forming the water dispersion, and it is possible to use a forced dispersion using a surfactant or a self-dispersion. From the viewpoint of stability of water dispersion, a self-dispersion is preferred, and for that purpose, it is preferable to have a hydrophilic group in the molecule or in the side chain. Furthermore, as the hydrophilic group, anionic groups such as sulfonic acid groups, phosphonic acid groups, carboxyl groups, or nonionic groups represented by polyethylene glycol are preferred. These hydrophilic acrylic resins can preferably be obtained by using hydrophilic group-containing acrylic acid esters or methacrylic acid ester components as monomers or macromolecules. There is no problem in using components other than acrylic acid, acrylic acid esters, methacrylic acid, or methacrylic acid esters. Examples include acrylic acid or methacrylamide, nitriles such as acrylonitrile or methacrylonitrile, styrenes such as styrene and α-methylstyrene, vinyls such as vinyl acetate and vinyl propionate, allyls such as allyl acetate and allyl propionate, unsaturated carboxylic acids such as maleic acid, itaconic acid, or their esters.

[0061] (Additives) In the coating layer of the present invention, known additives such as surfactants, antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic or inorganic lubricants, pigments, dyes, organic or inorganic particles, and antistatic agents may be added, provided that they do not impair the effects of the present invention.

[0062] In the present invention, it is also preferable to add particles to the coating layer in order to further improve the blocking resistance of the coating layer. Examples of particles to be contained in the coating layer in the present invention include titanium dioxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, or mixtures thereof, as well as other general inorganic particles such as calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, calcium fluoride in combination, and other inorganic particles, and organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based particles.

[0063] In this invention, since an amine compound with a boiling point of 150°C or higher is used, the pH in the coating solution is high, and even in the coating solution drying process, the presence of an amine compound with a relatively high boiling point suppresses pH fluctuations, making it possible to suppress the aggregation of dispersed particles in the coating solution due to pH fluctuations. For this reason, it is particularly preferable to use particles in which the aqueous dispersion is stable in the basic pH range. However, if the aggregation of particles in the coating solution can be suppressed by a dispersant or surface treatment agent, etc., this does not restrict the use of particles in which the aqueous dispersion is unstable in the basic pH range.

[0064] Furthermore, in the present invention, in order to prevent aggregation of the particles used, it is also possible to pre-treat the particles with a reactive compound such as a silane coupling agent or a resin having a polar group such as a carboxyl group. There are no particular restrictions on the resin used, and examples of treatment include pre-mixing the particles and resin in an organic solvent and then dispersing them in water, mixing the resin with the water-dispersed particles, and pre-mixing the particles and monomer and then polymerizing them.

[0065] The average particle size of the particles in the coating layer (average particle size based on the number of particles measured by a scanning electron microscope (SEM); the same applies hereinafter) is preferably 0.04 to 2.0 μm, and more preferably 0.1 to 1.0 μm. An average particle size of 0.04 μm or more for inert particles is preferable because it facilitates the formation of irregularities on the film surface, improving handling properties such as film slipperiness and windability, and resulting in good processability during lamination. On the other hand, an average particle size of 2.0 μm or less for inert particles is preferable because particle shedding is less likely to occur. The particle concentration in the coating layer is preferably 1 to 20% by mass of the solid components.

[0066] The average particle size was measured by observing the particles in the cross-section of a laminated polyester film using a scanning electron microscope, observing 30 particles, and using the average value of these observations as the average particle size.

[0067] The shape of the particles is not particularly limited as long as it satisfies the objectives of the present invention, and spherical particles or irregularly shaped non-spherical particles can be used. The particle size of irregularly shaped particles can be calculated as the equivalent diameter of a circle. The equivalent diameter of a circle is obtained by dividing the area of ​​the observed particle by π, calculating the square root, and multiplying by 2.

[0068] (Manufacturing of laminated polyester film) The method for producing a laminated polyester film in the present invention will be explained using an example with a polyethylene terephthalate (hereinafter sometimes abbreviated as PET) film substrate, but it is not limited to this.

[0069] After thoroughly vacuum-drying the PET resin, it is supplied to an extruder, and the molten PET resin at approximately 280°C is melt-extruded from the T-die onto a rotating cooling roll in a sheet shape. The molten PET resin is then cooled and solidified by electrostatic application to obtain an unstretched PET sheet. The unstretched PET sheet may be a single-layer structure or a multi-layer structure obtained by co-extrusion.

[0070] The obtained unstretched PET sheet is subjected to uniaxial or biaxial stretching to achieve crystal orientation. For example, in the case of biaxial stretching, the sheet is stretched 2.5 to 5.0 times in the longitudinal direction on a roll heated to 80 to 120°C to obtain a uniaxially oriented PET film. Then, the ends of the film are held with clips and guided into a hot air zone heated to 80 to 180°C, where it is stretched 2.5 to 5.0 times in the width direction. In the case of uniaxial stretching, it is stretched 2.5 to 5.0 times in a tenter. After stretching, it is then guided into a heat treatment zone and heat treatment is performed to complete the crystal orientation.

[0071] The lower limit of the heat treatment zone temperature is preferably 170°C, and more preferably 180°C. A temperature of 170°C or higher in the heat treatment zone is preferable because it ensures sufficient curing, provides good blocking properties in high-humidity environments, and facilitates adjustment of storage environments. On the other hand, the upper limit of the heat treatment zone temperature is preferably 260°C, and more preferably 250°C. A temperature of 260°C or lower in the heat treatment zone is preferable because it does not risk degrading the physical properties of the film.

[0072] The coating layer can be applied after the film is manufactured or during the manufacturing process. In particular, from the viewpoint of productivity, it is preferable to apply the coating solution to at least one side of the PET film after it has been unstretched or uniaxially stretched, thereby forming the coating layer.

[0073] Any known method can be used to apply this coating solution to the PET film. Examples include the reverse roll coating method, gravure coating method, kiss coating method, die coater method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, impregnation coating method, curtain coating method, and the like. These methods can be used individually or in combination.

[0074] In the present invention, the thickness of the coating layer can be appropriately set within the range of 0.001 to 2.00 μm, but to achieve both processability and adhesion, the range of 0.01 to 1.00 μm is preferable, more preferably 0.02 to 0.80 μm, and even more preferably 0.05 to 0.50 μm. A coating layer thickness of 0.001 μm or more is preferable because it provides good adhesion. A coating layer thickness of 2.00 μm or less is preferable because it is less likely to cause blocking.

[0075] The upper limit of the haze of the laminated polyester film of the present invention is preferably 2.5%, more preferably 2.0%, even more preferably 1.5%, and particularly preferably 1.2%. A haze of 2.5% or less is preferable in terms of transparency, and can be suitably used in optical films where transparency is required. The lower the haze, the better, but it is also preferable to have a haze of 0.1% or more, and also preferable to have a haze of 0.3% or more. [Examples]

[0076] Next, the present invention will be described in detail using examples and comparative examples, but the present invention is not limited to the following examples. First, the evaluation method used in the present invention will be described below.

[0077] (1) Hayes The haze of the obtained laminated polyester film was measured in accordance with JIS K 7136:2000 using a turbidimeter (NDH5000, manufactured by Nippon Denshoku).

[0078] (2) Acid value The acid values ​​of resins and crosslinking agents were measured by the titration method described in JIS K-1557-5:2007. However, in the case of carboxyl salts neutralized with amines, etc., the amines, etc. were removed by high-temperature treatment or by pre-treatment with hydrochloric acid, etc. to liberate and remove the amines, etc. before measurement. In the case of crosslinking agents, the reactive groups such as isocyanates were reacted with amines, etc. beforehand before measurement. If the resin to be measured had poor solubility in isopropanol, which is the solvent, N-methylpyrrolidone was used instead. In all of the above treatments, comparative measurements were thoroughly performed.

[0079] (3) Stability of the coating solution 200 g of the prepared coating solution was placed in a 220 ml mayonnaise bottle and left at room temperature for 24 hours while being stirred at 200 ± 20 rpm with a 7 mm diameter, 20 mm long rod-shaped Teflon® stirring bar. After standing, the entire contents of the solution were filtered through a 400 mesh SUS316 wire mesh. The filtration state and the residue on the wire mesh after filtration were visually inspected and evaluated according to the following. ◎: No stagnation of the coating solution, and no residue whatsoever was observed. ○: There is no stagnation of the coating solution, but a very small amount of residue can be observed. △: Some retention of the coating solution is observed, and residue is clearly visible. ×: Stagnation of the coating solution is observed, and residue can be seen across the entire filtration surface. Each person performed an initial assessment, and if the result was excellent (◎), that was used as the final evaluation result. If the result was below average (〇), three people performed the assessment again. The final evaluation result was determined by majority vote. However, if the three people's evaluations were divided, the median of their results was used as the final evaluation result. Based on the above evaluation criteria, a score of 〇 or higher was considered a passing grade.

[0080] (4) Coating surface quality (uneven coating and coating defects) In a darkroom, the film was suspended against a black felt background, and the coating surface quality was evaluated by observing it from the coated side using a 400-800 lumen LED flashlight. The coating surface quality was judged according to the following criteria. The evaluation area was 2 m² of the coated surface. 2 It was deemed appropriate. application spot ◎: The applied surface is uniform with no faint blemishes. ○: 5.0 small spots / m² on the coated surface 2 The following or the entire surface has slight spots. △: 6.0-10.0 small spots / m² on the coated surface. 2 Alternatively, it may have thin spots all over. ×: 11.0 small spots / m² on the coated surface 2 The area above or the entire surface is mottled. Furthermore, the variegation was classified according to the following criteria. When the spot area is 100 mm 2 or less, the spot is classified as a small spot. The darkness of spots was classified by cutting the corresponding portion identified through the aforementioned observation from the film, and confirming in the following order. The film piece was observed by transmission under an LED light source, and a spot was determined as such if it could be confirmed. If no spot was observed via transmission, the film piece was then placed on black felt with the coated surface facing upward, and visually observed from an upper position at an oblique angle of 45° to the film surface under an LED light source; if a spot could be confirmed, it was determined as a light spot. If no spot was observed in the above steps, visual observation was further performed by changing the angle from the oblique upper position relative to the film surface, and if a spot could be confirmed, it was determined as a faint spot. Coating defects ◎: No defects in the coating layer. ○: The number of small defects in the coating layer is 5.0 defects per m 2 or less. △: The number of defects in the coating is 2.0 defects per m 2 or less. or the number of small defects is 6.0 to 20.0 per m 2 . ×: The number of defects in the coating is 3.0 defects per m 2 or more, or the number of small defects is 21.0 per m 2 or more. The size of defects was judged according to the following criteria. The corresponding portion identified through the aforementioned observation was cut from the film and observed under an optical microscope at 100× magnification; a defect with a maximum side length of less than 1 mm was defined as a small defect. According to the above evaluation criteria, coating spots and coating defects with an evaluation of ○ or higher are regarded as acceptable.

[0081] (5) Blocking resistance Two film samples were stacked with their coated layer surfaces facing each other, a load of 98 kPa was applied, and the stacked samples were allowed to stand in close contact in an atmosphere at 50°C for 24 hours. Thereafter, the films were peeled apart, and the peeling state was judged according to the following criteria. ◎: No transfer of the coating layer occurs, and peeling can be performed easily. ○: No transfer of the coating layer occurs, but there is slight resistance during peeling. △: The coating layer is maintained, but the surface layer of the coating layer has partially transferred to the mating surface. ×: Two films are stuck together and cannot be separated, or even if they can be separated, the film substrate is cleaved. Based on the above evaluation criteria, a rating of ○ or higher was considered a passing grade.

[0082] (6) Adhesion with UV ink On the coated layer of a laminated polyester film, UV ink [manufactured by T&K TOKA Co., Ltd., product name "BEST CURE UV161 Blue S" or "BEST CURE UV161 White S"] is used to print on a printing press [manufactured by Akira Seisakusho Co., Ltd., product name "RI Tester"] using an ink pipette with 4 divisions and a 2-part roll. Then, the film coated with the ink layer is subjected to a high-pressure mercury lamp at 100 or 40 mJ / cm². 2 The UV-curing ink was cured by irradiating it with ultraviolet light. Next, 100 grid-like cuts were made on the ink layer surface using a cutter guide with a gap of 2 mm, penetrating the ink layer and reaching the film substrate. Then, cellophane adhesive tape (Nichiban, No. 405; 24 mm wide) was firmly attached to the grid-like cut surface. After that, the cellophane adhesive tape was peeled vertically from the ink layer surface of the ink-laminated film, and the number of grids that peeled off from the ink layer surface of the ink-laminated film was visually counted, and the adhesion between the ink layer and the film substrate was calculated using the following formula. Note that grids that were partially peeled off were also counted as peeled grids, and the ink adhesion was calculated as shown in the formula below. Ink adhesion (%) = 100 - (number of peeled squares) Ink adhesion was evaluated according to the following criteria. ◎: 100%, ○: 96-99%, △: 80-95%, ×: Less than 80% Based on the above evaluation criteria, a rating of ○ or higher was considered a passing grade.

[0083] (7) Adhesion to the hard coat layer Opstar Z7503 (manufactured by Arakawa Chemical Industries, Ltd.), a UV-curing hard coat agent, was applied to the coating layer of a laminated polyester film using a #5 wire bar and dried at 80°C for 1 minute. Then, the coated film was subjected to a high-pressure mercury lamp at a pressure of 100 mJ / cm². 2 A hard coat film was obtained by irradiating it with ultraviolet light. Next, using a cutter guide with a 2mm gap, 100 grid-like cuts were made on the hard coat layer surface, penetrating the hard coat layer and reaching the film substrate. Then, cellophane adhesive tape (Nichiban, No. 405; 24mm wide) was applied to the grid-like cut surface and firmly adhered. After that, the cellophane adhesive tape was peeled vertically from the hard coat layer surface of the hard coat laminated film. After performing the adhesive tape application and peeling operation a total of 5 times at the same location, the number of grids that peeled off from the hard coat layer surface of the hard coat laminated film was visually counted, and the adhesion between the hard coat layer and the film substrate was calculated using the following formula. Note that grids that were partially peeled were also counted as peeled grids, and the hard coat adhesion was calculated as shown in the formula below. Hard court adhesion (%) = 100 - (number of peeled squares) Hard court adhesion was determined according to the following criteria. ◎: 100%, ○: 96-99%, △: 80-95%, ×: Less than 80%. Based on the above evaluation criteria, a rating of ○ or higher was considered a passing grade.

[0084] (8) Moisture and heat resistance UV ink coated film prepared in the same manner as in (5) and (6) above (BEST CURE UV161 white S coating, followed by UV irradiation at 100 mJ / cm²) 2 The cured product or hard-coated film was left for 500 hours in an environment of 80°C and 80% RH with the coated surface vertical and without contact with other films or materials. After treatment, it was left for 10 minutes in an environment of 23°C and 65% RH, without contact with other films or materials. Immediately after the time had elapsed, the adhesion of the coated surface was evaluated in the same manner as described above.

[0085] (Synthesis of blocked isocyanate crosslinking agent (C-1)) In a flask equipped with a stirrer, thermometer, and reflux condenser, 171.5 parts by mass of a polyisocyanate compound having a vilette structure derived from hexamethylene diisocyanate (Duranate 24A-100, manufactured by Asahi Kasei Chemicals), 50.0 parts by mass of dipropylene glycol dimethyl ether, and 52.5 parts by mass of ethyl methyl ketoxime were added and held at 70°C with stirring under a nitrogen atmosphere for 2 hours. Subsequently, 26.0 parts by mass of dimethylolpropionic acid was added. By measuring the infrared spectrum of the reaction solution and confirming the disappearance of absorption of the isocyanate group, a block isocyanate-based crosslinking agent (C-1) solution with a solid content of 80.0% by mass was obtained. The solid content acid value of this block isocyanate-based crosslinking agent (C-1) was 43.2 mg KOH / g.

[0086] (Synthesis of blocked isocyanate crosslinking agent (C-2)) In a flask equipped with a stirrer, thermometer, and reflux condenser, 118.6 parts by mass of m-xylylene diisocyanate, 50.0 parts by mass of dipropylene glycol dimethyl ether, and 39.0 parts by mass of ethyl methyl ketoxime were added and the mixture was held at 70°C under a nitrogen atmosphere with stirring for 2 hours. Subsequently, 28.4 parts by mass of trimethylolpropane were added, and after 1 hour, 14.0 parts by mass of dimethylolpropionic acid were added. The infrared spectrum of the reaction solution was measured, and it was confirmed that the absorption of the isocyanate group had disappeared, yielding a blocked isocyanate crosslinking agent (C-2) solution with a solid content of 80.0% by mass. The solid content acid value of this blocked isocyanate crosslinking agent (C-2) was 29.2 mg KOH / g.

[0087] (Synthesis of blocked isocyanate crosslinking agent (C-3)) In a flask equipped with a stirrer, thermometer, and reflux condenser, 133.6 parts by mass of a polyisocyanate compound having an isocyanurate structure derived from hexamethylene diisocyanate (Duranate TPA-100, manufactured by Asahi Kasei Chemicals), 50.0 parts by mass of dipropylene glycol dimethyl ether, and 47.2 parts by mass of 3,5-dimethylpyrazole were added and the mixture was held at 70°C under a nitrogen atmosphere with stirring for 2 hours. Subsequently, 19.2 parts by mass of dimethylolbutanoic acid was added. By measuring the infrared spectrum of the reaction solution and confirming the disappearance of the absorption of the isocyanate group, a blocked isocyanate crosslinking agent (C-3) solution with a solid content of 80.0% by mass was obtained. The solid content acid value of this blocked isocyanate crosslinking agent (C-3) was 36.1 mgKOH / g.

[0088] (Synthesis of blocked isocyanate crosslinking agent (C-4)) In a flask equipped with a stirrer, thermometer, and reflux condenser, 116.2 parts by mass of dicyclohexylmethane-4,4'-diisocyanate, 21.2 parts by mass of 3,5-dimethylpyrazole, 32.2 parts by mass of polyethylene glycol monomethyl ether with a molecular weight of 550, and 50.0 parts by mass of dipropylene glycol dimethyl ether were added and the mixture was held at 70°C under a nitrogen atmosphere with stirring for 2 hours. Thereafter, at 1-hour intervals, 19.8 parts by mass of trimethylolpropane, 7.4 parts by mass of dimethylolpropionic acid, and 2.2 parts by mass of 1,6-hexanediol were added in order. After another hour, the infrared spectrum of the reaction solution was measured, and it was confirmed that the absorption of the isocyanate group had disappeared, thereby obtaining a blocked isocyanate crosslinking agent (C-4) solution with a solid content of 80.0% by mass. The solid content acid value of this blocked isocyanate crosslinking agent (C-4) was 15.3 mgKOH / g.

[0089] (Synthesis of blocked isocyanate crosslinking agent (C-5)) In a flask equipped with a stirrer, thermometer, and reflux condenser, 108.8 parts by mass of a polyisocyanate compound having an isocyanurate structure derived from hexamethylene diisocyanate (Duranate TPA-100, manufactured by Asahi Kasei Chemicals), 50.0 parts by mass of dipropylene glycol dimethyl ether, and 38.0 parts by mass of 3,5-dimethylpyrazole were added and the mixture was held at 70°C under a nitrogen atmosphere with stirring for 2 hours. Subsequently, 53.2 parts by mass of polyethylene glycol with a molecular weight of 500 was added. By measuring the infrared spectrum of the reaction solution and confirming the disappearance of absorption of the isocyanate group, a blocked isocyanate crosslinking agent (C-5) solution with a solid content of 80.0% by mass was obtained. The solid content acid value of this blocked isocyanate crosslinking agent (C-5) was 0.0 mg KOH / g.

[0090] (Synthesis of blocked isocyanate crosslinking agent (C-6)) In a flask equipped with a stirrer, thermometer, and reflux condenser, 127.4 parts by mass of a polyisocyanate compound having an isocyanurate structure derived from hexamethylene diisocyanate (Duranate TPA-100, manufactured by Asahi Kasei Chemicals), 50.0 parts by mass of dipropylene glycol dimethyl ether, and 72.6 parts by mass of 3,5-dimethylpyrazole were added and the mixture was held at 70°C under a nitrogen atmosphere with stirring for 2 hours. The infrared spectrum of the reaction solution was measured, and the disappearance of absorption of the isocyanate group was confirmed to yield a blocked isocyanate crosslinking agent (C-6) solution with a solid content of 80.0% by mass. The solid content acid value of this blocked isocyanate crosslinking agent (C-6) was 0.0 mgKOH / g.

[0091] (Synthesis of oxazoline crosslinking agent (C-7) and preparation of aqueous dispersion (C-7WD)) In a flask equipped with a stirrer, thermometer, and reflux condenser, 100.0 parts by mass of water and 100.0 parts by mass of methoxypropyl alcohol were charged and heated to 80°C under a nitrogen atmosphere. Then, a monomer mixture consisting of 31.4 parts by mass of methyl methacrylate, 53.2 parts by mass of methacrylate amide, 48.6 parts by mass of 2-isopropenyl-2-oxazoline, and 66.8 parts by mass of an ester compound of n=9 polyethylene glycol monomethyl ether and methacrylic acid, and a polymerization initiator solution consisting of 10.0 parts by mass of 2,2'-azobis(2-amidinopropane) dihydrochloride and 100.0 parts by mass of water were added dropwise from a dropping funnel under a nitrogen atmosphere over 2 hours while maintaining the flask at 80°C. After the addition was complete, the mixture was stirred at 80°C for 5 hours and then cooled to room temperature. An appropriate amount of water was added to prepare an aqueous dispersion (C-7WD) of an oxazoline crosslinking agent (C-7) with a solid content of 40.0% by mass. The solid content acid value of this oxazoline crosslinking agent (C-7) was 0.0 mg KOH / g.

[0092] (Preparation of an aqueous dispersion of a blocked isocyanate crosslinking agent (C-1) (C-1-AWD)) To the aforementioned blocked isocyanate crosslinking agent (C-1) solution, an equimolar amount of methyldiethanolamine (boiling point 245°C) equivalent to the carboxyl groups determined from the solid content mass and acid value at room temperature was added, and the mixture was stirred for 30 minutes to obtain a neutralized blocked isocyanate crosslinking agent (C-1-A), in which 100% of the carboxyl groups of the blocked isocyanate crosslinking agent (C-1) were replaced with the amine salt of methyldiethanolamine, as shown in Table 1. Next, 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, and the mixture was stirred for 2000 min. -1 While stirring and mixing, a solution of neutralized blocked isocyanate crosslinking agent (C-1-A) was added and dispersed in water. Subsequently, by adjusting the concentration with water, an aqueous dispersion of neutralized blocked isocyanate crosslinking agent (C-1-AWD) with a solid content of 40% by mass was prepared.

[0093] (Preparation of aqueous dispersions of blocked isocyanate crosslinking agents (C-1-BWD)~(C-1-GWD), (C-2-AWD)~(C-2-JWD), (C-3WD), (C-4WD)) Aqueous dispersions of the neutralized products of each crosslinking agent (C-1-BWD) to (C-1-GWD), (C-2-AWD) to (C-2-JWD), (C-3WD), and (C-4WD) were prepared in the same manner as the preparation of the neutralized product of the blocked isocyanate crosslinking agent (C-1-AWD) described above. However, the type and ratio of amine added were changed according to the corresponding blocked isocyanate crosslinking agent as shown in Table 1.

[0094] (Preparation of an aqueous dispersion (C-5WD) of a blocked isocyanate crosslinking agent (C-5)) A blocked isocyanate crosslinking agent (C-5) with an acid value of 0.0 mg KOH / g was subjected to aqueous dispersion treatment in the same manner as the aqueous dispersion (C-1-AWD), except that neutralization treatment with amines, etc. was not performed, to prepare an aqueous dispersion of the blocked isocyanate crosslinking agent (C-5WD).

[0095] (Preparation of an aqueous dispersion (C-6WD) of a blocked isocyanate crosslinking agent (C-6)) Add a predetermined amount of water to a reaction vessel equipped with a homodisperser capable of high-speed stirring, and stir at 25°C for 2000 minutes. -1 While stirring and mixing, the aforementioned blocked isocyanate crosslinking agent (C-6) solution and polyoxyethylene (13) oleyl ether as an emulsifier were gradually added at a concentration of 5% by mass relative to the solid content of the crosslinking agent and dispersed in water. By adjusting the concentration with water, an aqueous dispersion of the blocked isocyanate crosslinking agent (C-6WD) with a solid content of 40% by mass was prepared.

[0096] (Polymerization of copolymerized polyester resin PES-1) In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 188.0 parts by mass of dimethyl terephthalate, 188.0 parts by mass of dimethyl isophthalate, 17.8 parts by mass of dimethyl-5-sodium sulfoisophthalate, 178.0 parts by mass of ethylene glycol, 160.0 parts by mass of neopentyl glycol, and 0.2 parts by mass of tetra-n-butyl titanate were charged, and a transesterification reaction was carried out at a temperature of 160°C to 220°C for 4 hours. The temperature was then raised to 255°C, the reaction system was gradually depressurized, and the reaction was carried out under a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain copolymerized polyester resin (PES-1). The obtained copolymerized polyester resin (PES-1) was pale yellow and transparent. The reduced viscosity of copolymerized polyester resin (PES-1) was measured to be 0.55 dl / g.

[0097] (Preparation of aqueous dispersion of copolymerized polyester resin PES-1 (PES-1WD)) In a reactor equipped with a stirrer, thermometer, and reflux device, equal parts by mass of the aforementioned copolymer polyester resin (PES-1) and ethylene glycol-n-butyl ether were added and heated at 110°C, stirring to dissolve the resin. After the resin was completely dissolved, a predetermined amount of water was gradually added to the polyester solution while stirring, and after the addition was complete, the liquid was cooled to room temperature while stirring. An appropriate amount of water was added to prepare an aqueous dispersion of copolymer polyester resin PES-1 (PES-1WD) with a solid content of 30% by mass.

[0098] PES-3 was polymerized from copolymer polyester resin PES-2 in the same manner as PES-1. The composition and physical properties of the polymerized copolymer polyester resins are shown in Table 2. In addition, PES-2WD and PES-3WD, which are aqueous dispersions with a solid content of 30% by mass, were prepared using copolymer polyester resins PES-2 to PES-3, similar to the aqueous dispersion of copolymer polyester resin PES-1 (PES-1WD).

[0099] (Synthesis of polyurethane resin PU-1) In a four-necked flask equipped with a stirrer, a Liebig condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 70.0 parts by mass of dicyclohexylmethane-4,4'-diisocyanate, 94.2 parts by mass of polycarbonate diol mainly composed of 1,6-hexanediol with a number average molecular weight of 1000, and 200 parts by mass of ethyl methyl ketone as a solvent were added. The mixture was stirred at 75°C under a nitrogen atmosphere for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, 17.2 parts by mass of polyethylene glycol monomethyl ether with a molecular weight of 550 was added, and the mixture was stirred for a further 2 hours. The infrared spectrum of the reaction solution was measured to confirm the disappearance of isocyanate groups in the reaction solution. By cooling this reaction solution to below room temperature, a polyurethane resin (PU-1) solution with a solid content of 50.0% by mass was obtained.

[0100] (Preparation of aqueous dispersion of polyurethane resin PU-1 (PU-1WD)) A predetermined amount of water is added to a reaction vessel equipped with a homodisperser capable of high-speed stirring, and the temperature is adjusted to 25°C for 2000 minutes. -1 While stirring and mixing, the aforementioned polyurethane resin (PU-1) solution was gradually added and dispersed in water. Then, under reduced pressure, the solvent, ethyl methyl ketone, was removed. By adjusting the concentration with water, an aqueous dispersion of polyurethane resin (PU-1WD) with a solid content of 35% by mass was prepared.

[0101] (Synthesis of polyurethane resin PU-2) In a four-necked flask equipped with a stirrer, a Liebig condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 82.6 parts by mass of dicyclohexylmethane-4,4'-diisocyanate, 93.2 parts by mass of polyethylene glycol with a number average molecular weight of 1000, and 200 parts by mass of ethyl methyl ketone as a solvent were added. The mixture was stirred at 75°C under a nitrogen atmosphere for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, 24.2 parts by mass of neopentyl glycol was added, and the mixture was stirred for a further 2 hours. The infrared spectrum of the reaction solution was measured to confirm the disappearance of isocyanate groups in the reaction solution. By cooling this reaction solution to below room temperature, a polyurethane resin (PU-2) solution with a solid content of 50.0% by mass was obtained.

[0102] (Preparation of aqueous dispersion of polyurethane resin PU-2 (PU-2WD)) An aqueous dispersion of polyurethane resin (PU-2) with a solid content of 35% by mass (PU-2WD) was prepared in the same manner as the preparation of the aqueous dispersion of polyurethane resin PU-1 (PU-1WD) described above.

[0103] (Synthesis of polyurethane resin PU-3) In a four-necked flask equipped with a stirrer, a Liebig condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 53.2 parts by mass of dicyclohexylmethane-4,4'-diisocyanate, 9.8 parts by mass of dimethylolpropionic acid, 130.4 parts by mass of polycarbonate diol mainly composed of 1,6-hexanediol with a number average molecular weight of 1000, 6.6 parts by mass of polyethylene glycol with a number average molecular weight of 450, and 200 parts by mass of ethyl methyl ketone as a solvent were added. The mixture was stirred at 75°C for 3 hours under a nitrogen atmosphere, and the infrared spectrum of the reaction solution was measured to confirm the disappearance of isocyanate groups in the reaction solution. By cooling this reaction solution to below room temperature, a polyurethane resin (PU-3) solution with a solid content of 50.0% by mass was obtained. The solid content acid value of this polyurethane resin (PU-3) solution was 20.1 mgKOH / g.

[0104] (Preparation of aqueous dispersion of polyurethane resin PU-3 (PU-3WD)) To 100 parts by mass of the aforementioned polyurethane resin (PU-3) solution, 1.9 parts by mass of triethylamine was added at room temperature, and the mixture was stirred for 30 minutes to neutralize the carboxyl groups of the polyurethane resin (PU-3) with triethylamine. Next, 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 for 2000 minutes. -1 The neutralized solution was added while stirring and mixed, and dispersed in water. Then, the solvent, ethyl methyl ketone, was removed under reduced pressure. By adjusting the concentration with water, an aqueous dispersion of polyurethane resin (PU-3) with a solid content of 35% by mass (PU-3WD) was prepared.

[0105] (Polymerization of acrylic resin (AC-1)) 85.7 parts by mass of propylene glycol monomethyl ether was placed in a flask equipped with a stirrer, thermometer, and reflux condenser, and heated and maintained at 100°C. A mixture of 108.8 parts by mass of methyl methacrylate, 69.2 parts by mass of ethyl acrylate, 10.2 parts by mass of 2-hydroxyethyl methacrylate, 11.8 parts by mass of N-methylmethacrylamide, and 10 parts by mass of azobisisobutyronitrile was added dropwise over 3 hours. After dropwise addition, the mixture was allowed to mature at the same temperature for 2 hours. By cooling this reaction solution to below room temperature, an acrylic resin (AC-1) solution with a solid content of 70.0% by mass was obtained.

[0106] (Preparation of aqueous dispersion of acrylic resin (AC-1) (AC-1WD)) Add a predetermined amount of water to a reaction vessel equipped with a homodisperser capable of high-speed stirring, and stir at 25°C for 2000 minutes. -1 While stirring and mixing, the aforementioned acrylic resin (AC-1) solution and polyoxyethylene (13) oleyl ether as an emulsifier were gradually added at a concentration of 5% by mass relative to the acrylic resin solids and dispersed in water. By adjusting the concentration with water, an aqueous dispersion of acrylic resin (AC-1WD) with a solids content of 30% by mass was prepared.

[0107] (Polymerization of acrylic resin (AC-2)) 85.7 parts by mass of propylene glycol monomethyl ether was placed in a flask equipped with a stirrer, thermometer, and reflux condenser, and heated and maintained at 100°C. A mixture of 100.2 parts by mass of methyl methacrylate, 59.2 parts by mass of ethyl acrylate, 41.4 parts by mass of polyethylene glycol monomethyl ether methacrylate (n=9), 8.2 parts by mass of N-methyl methacrylamide, and 10 parts by mass of azobisisobutyronitrile was added dropwise over 3 hours. After addition, the mixture was allowed to mature at the same temperature for 2 hours. By cooling this reaction solution to below room temperature, an acrylic resin (AC-2) solution with a solid content of 70.0% by mass was obtained.

[0108] (Preparation of aqueous dispersion of acrylic resin (AC-2) (AC-2WD)) Add a predetermined amount of water to a reaction vessel equipped with a homodisperser capable of high-speed stirring, and stir at 25°C for 2000 minutes. -1 While stirring and mixing, the aforementioned acrylic resin (AC-2) solution was gradually added and dispersed in water. By adjusting the concentration with water, an aqueous dispersion of acrylic resin (AC-2WD) with a solid content of 30% by mass was prepared.

[0109] (particle) (Particle (P-1)) Colloidal silica (Snowtex O; manufactured by Nissan Chemical Corporation) with an average particle size of 10-15 nm and a solid content concentration of 20% by mass was used as the particle (P-1) solution.

[0110] (Particle (P-2)) Colloidal silica (Seahostar KE-W50; Nippon Shokubai Co., Ltd.) with an average particle size of 500 nm and a solid content concentration of 20% by mass was used as the particle (P-2) solution.

[0111] (Particle (P-3)) As the particle (P-3) solution, zirconia oxide particles (ZSL00014; Daiichi Rare Elements Chemical Industry Co., Ltd.) with an average particle size of 10-20 nm and a solid content concentration of 20% by mass were used as the particle (P-3).

[0112] (Additives) (Preparation of additive (AD-1) solution) A solution of additive (AD-1) with an amine concentration of 50% by mass was prepared by adding dimethylethanolamine (boiling point 134°C, molecular weight 89.1) and a predetermined amount of water to a flask equipped with a stirrer and thermometer and dissolving it.

[0113] (Preparation of additive (AD-2) solution) A solution of additive (AD-2) with an amine concentration of 50% by mass was prepared by adding methyldiethanolamine (boiling point 245°C, molecular weight 119.2) and a predetermined amount of water to a flask equipped with a stirrer and thermometer and dissolving it.

[0114] (Preparation of additive (AD-3) solution) A solution of additive (AD-3) with an amine concentration of 50% by mass was prepared by adding triethanolamine (boiling point 335°C, molecular weight 149.2) and a predetermined amount of water to a flask equipped with a stirrer and thermometer and dissolving it.

[0115] (Manufacturing of polyester resin (E-1) for base materials) (Preparation of antimony trioxide solution) Antimony trioxide (manufactured by Sigma-Aldrich Japan LLC) was placed in a flask with ethylene glycol, stirred at 150°C for 4 hours to dissolve, and then cooled to room temperature to prepare a 20 g / L antimony trioxide ethylene glycol solution.

[0116] (Polymerization of polyester resin (E-1) for base materials) High-purity terephthalic acid and twice its molar volume of ethylene glycol were charged into a 2-liter stainless steel autoclave equipped with a stirrer. 0.3 mol% triethylamine was added relative to the acid component, and the esterification reaction was carried out at 250°C under a pressure of 0.25 MPa while distilling off water from the system to obtain a mixture of bis(2-hydroxyethyl) terephthalate and oligomer (hereinafter referred to as the BHET mixture) with an esterification rate of approximately 95%. The above antimony trioxide solution was used as a polycondensation catalyst and added to this BHET mixture so that the amount of antimony atoms relative to the acid component in the polyester was 0.04 mol%, and then the mixture was stirred at 250°C for 10 minutes under atmospheric pressure in a nitrogen atmosphere. Subsequently, the reaction system pressure was gradually reduced to 13.3 Pa (0.1 Torr) while the temperature was raised to 280°C over 60 minutes. A polycondensation reaction was then carried out at 280°C and 13.3 Pa for 68 minutes, yielding a polyester resin (E-1) with an intrinsic viscosity (IV) (solvent: phenol / tetrachloroethane = 60 / 40) of 0.61 dL / g and substantially free of particles.

[0117] (Manufacturing of polyester resin (E-2) for base materials) (Example of aluminum compound solution preparation) An equal volume (by volume) of ethylene glycol was added to a 20 g / L aqueous solution of basic aluminum acetate (hydroxyaluminum diacetate; manufactured by Sigma-Aldrich Japan LLC) in a flask. The mixture was stirred at room temperature for 6 hours, and then water was removed from the system under reduced pressure (133 Pa) at 70-90°C for several hours while stirring, to prepare a 20 g / L ethylene glycol solution of the aluminum compound.

[0118] (Example of preparation of phosphorus compound solution) Diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid (Irganox 1222 (BASF)) was placed in a flask with ethylene glycol as the phosphorus compound, and the mixture was heated at 160°C for 25 hours under nitrogen purging and stirring to prepare a 50 g / L ethylene glycol solution of the phosphorus compound.

[0119] (Preparation of a mixture of aluminum compound solution and phosphorus compound solution) The ethylene glycol solutions obtained in the above-mentioned aluminum compound preparation example and the above-mentioned phosphorus compound preparation example were placed in flasks and mixed at room temperature so that the molar ratio of aluminum atoms to phosphorus atoms was 1:2. The mixture was then stirred for one day to prepare the catalyst solution.

[0120] (Polymerization of polyester resin (E-2) for base materials) Instead of the antimony trioxide solution as the polycondensation catalyst, a mixture of the aforementioned aluminum compound solution and phosphorus compound solution was used so that the aluminum atoms and phosphorus atoms in the acid component of the polyester were at 0.014 mol% and 0.028 mol%, respectively. Except for the additions, the polymerization was carried out in the same manner as for polyester resin E-1. However, by setting the polymerization time to 68 minutes, a polyester resin (E-2) with an intrinsic viscosity (IV) of 0.61 dL / g and substantially free of particles was obtained.

[0121] (Example 1) (1) Preparation of coating solution (No. 2) A mixture of water and isopropanol (80 / 20 parts by mass ratio) was mixed with the following coating agents to prepare a total of 100 parts by mass. The solid content mass ratio of the aqueous dispersion of blocked isocyanate crosslinking agent (C-1-BWD), aqueous dispersion of polyester resin (PES-1WD), and aqueous dispersion of polyurethane resin (PU-1WD) was 30 / 35 / 35, and the total solid resin content concentration was 4% by mass. Next, the solid content mass ratios of particles (P-1) and particles (P-2) were set to 12.0 and 0.4 respectively, relative to the total solid content of the aforementioned resins, etc. (100%). Furthermore, 1% by mass of a 10% aqueous solution of a silicone-based surfactant was added to this coating solution to prepare coating solution (No. 2). The mixing ratios of resins and additives for each coating solution are shown in Table 3. An example of the preparation of coating solution (No. 2) is shown below.

[0122] Example of preparation of coating solution (No. 2) Mixed solvent (water / isopropanol) 84.85 parts by mass Aqueous dispersion of blocked isocyanate crosslinking agent (C-1-BWD) 3.00 parts by mass Aqueous dispersion of polyester resin (PES-1WD) 4.67 parts by mass Aqueous dispersion of polyurethane resin (PU-1WD) 4.00 parts by mass Particle (P-1) solution 2.40 parts by mass Particle (P-2) solution 0.08 parts by mass 1.00 parts by mass of aqueous surfactant solution Total 100.00 parts by mass

[0123] (2) Manufacturing of laminated polyester film As the raw material resin for the film, resin pellets of polyester resin (E-1) were dried at 135°C for 6 hours under reduced pressure of 133 Pa. Then, they were fed into an extruder and melt-extruded into a sheet at approximately 280°C. The sheet was then rapidly cooled and solidified on a rotating, cooled metal roll maintained at a surface temperature of 20°C to obtain an unstretched PET sheet.

[0124] This unstretched PET sheet was heated to 100°C using a heated roll group and an infrared heater, and then stretched 3.5 times in the longitudinal direction using a roll group with different peripheral speeds to obtain a uniaxially oriented PET film.

[0125] Next, the coating solution (No. 2) was applied to one side of the PET film, with a final coating amount of 0.08 g / m² after drying (after biaxial stretching). 2 The film was coated in the manner described above. After coating, it was heat-treated at 90°C for 3 seconds and then at 40°C for 3 seconds to dry. Next, the film was stretched to 4.0 times its original width at 110°C, and with the width direction of the film fixed, it was heated at 230°C for 5 seconds. A further 3% widthwise relaxation treatment was performed to obtain a laminated polyester film with a thickness of 100 μm. The thickness of the coated layer was 70 nm. The evaluation results of this film are shown in Table 4.

[0126] (Examples 2-4) A laminated polyester film was obtained in the same manner as in Example 1, except that the coating solution No. listed in Table 4 was used for each example. The types and proportions of crosslinking agents, resins, particles, etc. used for each coating solution No. are as shown in Table 3.

[0127] (Example 5) A laminated polyester film was obtained in the same manner as in Example 1, except that the coating solution used was the coating solution (No. 8) listed in Table 4. The details of the coating solution (No. 8) are shown below. (1) Preparation of coating solution (No. 8) Similar to coating solution (No. 1), the types and proportions of crosslinking agent, resin, particles, etc., as shown in Table 3 were used. However, for coating solution (No. 8), as shown in Table 3, an additive (AD-2) solution consisting of methyldiethanolamine with a boiling point of 245°C, corresponding to amine compound (B), was added. The amount added was equal to the molar amount relative to the amount of carboxyl groups determined from the acid value of the crosslinking agent. With the addition of the additive (AD-2) solution, the apparent difference in boiling points of the amine in the blocked isocyanate crosslinking agent (crosslinking agent in C-1-FWD) was 156°C, the molar % (((A)+(B)) / (C)) of total amine to carboxyl groups of the crosslinking agent was 200%, and the molar % ((A) / ((A)+(B))) of amine compound (A) relative to total amine was 50%. In Table 3, the aforementioned molar amounts of additive (AD-2) are expressed in parts by solids per 100 units of total solids of the crosslinking agent and resin. Furthermore, the increase in parts by mass due to the additive (AD-2) solution was adjusted by the amount added to the mixed solution. An example of the preparation of coating solution (No. 8) is shown below.

[0128] Preparation example of coating solution (No. 8) Mixed solvent (water / isopropanol) 84.63 parts by mass Aqueous dispersion of blocked isocyanate crosslinking agent (C-1-FWD) 3.00 parts by mass Aqueous dispersion of polyester resin (PES-1WD) 4.67 parts by mass Aqueous dispersion of polyurethane resin (PU-1WD) 4.00 parts by mass Particle (P-1) solution 2.40 parts by mass Particle (P-2) solution 0.08 parts by mass 1.00 parts by mass of aqueous surfactant solution Additive (AD-2) solution: 0.22 parts by mass Total 100.00 parts by mass

[0129] (Examples 6-8) As shown in Table 4, laminated polyester films were obtained in Examples 6-8 in the same manner as in Example 1, except that the corresponding coating solutions No. 9, 10, and 12 were used. The types and proportions of crosslinking agents, resins, particles, and additives used in each coating solution No. are as shown in Table 3, and the solutions were prepared in the same manner as the aforementioned coating solution (No. 8). In coating solutions No. 9, 10, and 12, the amount of each additive corresponding to amine compound (B) was set to 6, 3, and 3 times the molar amount of the carboxyl group amount determined from the acid value of the crosslinking agent, respectively. For each additive, the apparent boiling point difference of the amine in the blocked isocyanate crosslinking agent (crosslinking agent in C-1-FWD) was 156, 246, and 201°C, the molar % of total amine and carboxyl groups of the crosslinking agent (((A)+(B)) / (C)) was 700, 400, and 400%, respectively, and the molar % of the amount of amine compound (A) used relative to the total amine ((A) / ((A)+(B))) was 14, 25, and 25%, respectively.

[0130] (Examples 9-23) A laminated polyester film was obtained in the same manner as in Example 1, except that the coating solution No. listed in Table 4 was used for each example. The types and proportions of crosslinking agents, resins, particles, etc. used for each coating solution No. are as shown in Table 3.

[0131] (Example 24) A laminated polyester film was obtained in the same manner as in Example 19, except that E-2 was used instead of E-1 as the film raw material resin.

[0132] (Comparative Examples 1-2) A laminated polyester film was obtained in the same manner as in Example 1, except that the coating solution No. listed in Table 4 was used for each example. The types and proportions of crosslinking agents, resins, particles, etc. used for each coating solution No. are as shown in Table 3.

[0133] (Comparative Example 3) A laminated polyester film was obtained in the same manner as in Example 8, except that the coating solution used was the coating solution (No. 7) listed in Table 4. In the preparation of coating solution (No. 7), as shown in Table 3, an additive (AD-1) solution consisting of dimethylethanolamine with a boiling point of 134°C, corresponding to amine compound (A), was used. The amount added was three times the molar amount of the carboxyl groups determined from the amount of crosslinking agent used and the acid value. With the addition of additive (AD-1) solution, the ratio of the number of moles of total amine to the number of carboxyl groups of the crosslinking agent (((A)+(B)) / (C)) was 400 mol%, and the molar ratio of amine compound (A) to total amine ((A) / ((A)+(B))) was 100 mol%.

[0134] (Comparative Examples 4-9) A laminated polyester film was obtained in the same manner as in Example 1, except that the coating solution No. listed in Table 4 was used for each example. The types and proportions of crosslinking agents, resins, particles, etc. used for each coating solution No. are as shown in Table 3.

[0135] Table 4 shows the evaluation results for each example and comparative example.

[0136] As shown in Table 4, satisfactory results were obtained in each of Examples 1 to 24 regarding haze, coat quality, blocking resistance, adhesion to UV ink or hard coat layer, and humidity and heat resistance. On the other hand, the results for Comparative Examples 1 to 9 were not satisfactory.

[0137] [Table 1]

[0138] [Table 2]

[0139] [Table 3]

[0140] [Table 4] [Industrial applicability]

[0141] This invention makes it possible to provide a laminated polyester film with excellent moisture and heat resistance and easy adhesion, ideal for a wide range of applications including optical, building materials, packaging, and labeling.

Claims

1. A laminated film comprising a coating layer on at least one side of a polyester film substrate, The coating layer is formed by comprising a polyester resin and a composition containing an isocyanate-based crosslinking agent having carboxyl base salts of two amine compounds, one with a boiling point less than 150°C and the other with a boiling point of 150°C or higher. The isocyanate-based crosslinking agent is a blocked isocyanate. When the amine compound with a boiling point of less than 150°C is designated as amine compound (A), and the amine compound with a boiling point of 150°C or higher is designated as amine compound (B), the amount of amine compound (A) used is: The molar percentage of (A / (A+B)) is between 10% and 90% of the sum of amine compounds (A) and (B). A laminated polyester film in which the amounts of the amine compounds (A) and (B) added to the aqueous dispersion of the crosslinking agent are in the range of 50 to 600% mol% (((A) + (B)) / (C)) relative to the total carboxyl groups (C) of the crosslinking agent.

2. The laminated polyester film according to claim 1, wherein the amine compound having a boiling point of 150°C or higher has one or more hydroxyl groups.

3. The laminated polyester film according to claim 1 or 2, wherein the boiling point difference between the two amine compounds is 70°C or more.

4. A composition comprising a polyester resin and an isocyanate-based crosslinking agent having carboxyl salts of two amine compounds having a boiling point of less than 150°C and a boiling point of 150°C or more, The isocyanate-based crosslinking agent is a blocked isocyanate. When the amine compound with a boiling point of less than 150°C is designated as amine compound (A), and the amine compound with a boiling point of 150°C or higher is designated as amine compound (B), the amount of amine compound (A) used is: The molar percentage of (A / (A+B)) is between 10% and 90% of the sum of amine compounds (A) and (B). The amounts of the amine compounds (A) and (B) added to the aqueous dispersion of the crosslinking agent are such that the molar percentage (((A) + (B)) / (C)) is in the range of 50 to 600% relative to the total carboxyl groups (C) of the crosslinking agent. A composition used for forming a coating layer laminated onto a polyester film.

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