JP7848795B2 - Antistatic polyester film - Google Patents

Description

This invention relates to an antistatic polyester film. More specifically, it relates to an antistatic polyester film having an antistatic layer and an adhesive layer laminated on the antistatic layer, and in particular to a protective film for optical components (for example, components of organic EL and liquid crystal displays).

Thermoplastic resin films, particularly polyester films, possess excellent mechanical, electrical, dimensional stability, transparency, and chemical resistance properties. Therefore, they are widely used in magnetic recording materials, packaging materials, solar cells, flat-panel displays, and other applications, including anti-reflective films, diffusion sheets, prism sheets, and other optical films, as well as label printing films, antistatic films, and protective films. However, due to the highly crystalline surface orientation of polyester films, they have the disadvantage of poor adhesion to various paints, resins, and inks during processing for these applications.
For this reason, various methods have been studied to impart adhesion to the surface of polyester film.

Conventionally, surface activation methods such as corona discharge treatment, ultraviolet irradiation treatment, and plasma treatment of the polyester film surface used as the substrate are known as methods for imparting adhesion. However, the adhesive effect obtained by these treatments decreases over time, making it difficult to maintain a high level of adhesion over a long period of time. (Patent Document 1)
Therefore, a common method involves applying various resins to the surface of a polyester film to create a coating layer with good adhesion properties.

Conventionally, techniques have been known to improve the affinity with resin components such as polyurethane acrylate or ester acrylate used in hard coat agents and prism lens materials, and to provide adhesion to them, by using coating solutions containing copolymerized polyester resin or urethane resin, or coating solutions using these resins in combination with crosslinking agents, in the coating layer (Patent Documents 2 and 3). However, UV inks (ultraviolet-curing inks) used in label printing contain dyes or pigments in addition to resins for color development, and pigments with relatively good lightfastness are used in amounts of about 15 to 25% by weight of the ink components. Furthermore, in white ink systems where opacity is important, the content of white pigment is about 50% by weight, so adhesion is insufficient with conventional techniques, and adhesion is particularly difficult under low radiation doses.

Regarding protective films, it has been proposed to provide an antistatic layer or an adhesive layer on a polyester film. (Patent Document 4) However, with conventional methods, the adhesion between the polyester film and the antistatic layer or adhesive layer is insufficient, and the durability is insufficient, especially when stored under high temperature and high humidity conditions, and the decrease in adhesion has been a problem.

Japanese Unexamined Patent Publication No. 58-27724 Japanese Patent Publication No. 2000-229355 Japanese Patent Publication No. 2009-220376 Japanese Patent Publication No. 2018-172473

This invention was made against the backdrop of the problems of the prior art. Specifically, the object of this invention is to provide an antistatic polyester film that exhibits good adhesion between the polyester film and the antistatic layer, and that maintains a high level of adhesion over a long period of time.

In other words, the present invention consists of the following configuration.
[1] An antistatic polyester film in which an easy-adhesion layer and an antistatic layer are laminated in this order on at least one side of a polyester film, wherein the easy-adhesion layer is a layer formed by curing a composition containing a polyurethane resin having a carboxyl group and an acid value of 30 to 50 mg KOH/g and a crosslinking agent having a carboxyl group and an acid value of 30 to 50 mg KOH/g.
[2] In one embodiment, the crosslinking agent is an isocinate compound.
[3] In one embodiment, the surface resistivity is ^10¹⁰ Ω/□ or less.
[4] In one embodiment, the antistatic layer includes a conductive polymer.
[5] In one embodiment, the film haze is 3.0% or less.
[6] An adhesive film having an adhesive layer laminated on at least one side of the antistatic polyester film.

The antistatic polyester film of the present invention exhibits excellent adhesion to UV-curing resins such as hard coat layers, lens layers, and inks, and in particular, it exhibits a high level of adhesion to UV inks.
The present invention provides an antistatic polyester film that exhibits excellent blocking resistance, initial adhesion between the antistatic layer, the easy-adhesion layer, and the polyester film substrate, as well as excellent moisture- and heat-resistant adhesion.

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

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

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 possesses 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.

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.

(Easy adhesive layer)
In order to improve adhesion to the antistatic layer and adhesive layer and to improve blocking resistance, it is preferable that the antistatic polyester film of the present invention has an easily adhesive layer laminated on at least one side of the polyester film substrate, which is formed from a polyurethane resin having a carboxyl group and an acid value of 30 to 50 mg KOH/g, and a crosslinking agent having a carboxyl group and an acid value of 30 to 50 mg KOH/g. The easily adhesive layer may be provided on both sides of the polyester film, or it may be provided on only one side of the polyester film, with a different resin coating layer provided on the other side.

The easily adhesive layer in this invention exhibits excellent adhesion to UV-curing resins or thermosetting resins such as antistatic layers, hard coat layers, lens layers, and inks. Furthermore, by having a certain range of carboxyl groups in both the polyurethane resin and the crosslinking agent, it is possible to incorporate a large number of carboxyl groups into the easily adhesive layer itself, while suppressing the occurrence of drawbacks such as reduced water resistance and poor heat and humidity resistance that can result from a resin having too many carboxyl groups.

The weight ratio of the polyurethane resin having carboxyl groups to the crosslinking agent having carboxyl groups is preferably in the range of 90/10 to 10/90, more preferably in the range of 80/20 to 20/80, and even more preferably in the range of 70/30 to 30/70. If the amount of crosslinking agent is too low, durability such as resistance to moisture and heat will decrease, and if the amount of polyurethane resin is too low, adhesion will decrease.

The following provides a detailed explanation of the composition of each easy-adhesion layer.
(Polyurethane resin with carboxyl groups and an acid value of 30-50 mgKOH/g)
A polyurethane resin having carboxyl groups is a urethane resin synthesized from at least a polyol component, a polyisocyanate component, and optionally a chain extender, and having carboxyl groups in the molecule or in the side chains. Here, "in the molecule" refers to those present in the main chain or at the ends of the polyurethane resin. Furthermore, side chains are those introduced onto branched molecular chains after synthesis and polymerization, due to the presence of three or more terminal functional groups in any of the aforementioned raw material components that constitute the molecular chain.
The polyurethane resin having carboxyl groups in the present invention is mainly obtained by using a carboxyl group-containing polyol component as a component of urethane.

Examples of such carboxyl group-containing polyol components include the following:
Relatively high molecular weight materials, such as carboxyl group-containing polyalkylene glycols, carboxyl group-containing acrylic polyols, carboxyl group-containing polyolefin polyols, and carboxyl group-containing polyester polyols, can be used. Relatively low molecular weight materials, such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, and 2,2-dimethylolvaleric acid, can also be used. Dimethylolpropionic acid and dimethylolbutanoic acid are particularly preferred for carboxyl group introduction.

The acid value of the polyurethane resin having a carboxyl group is preferably 30 to 50 mgKOH/g, and more preferably 35 to 45 mgKOH/g. An acid value of 30 mgKOH/g or higher improves adhesion to the antistatic layer and adhesive layer. On the other hand, an acid value of 50 mgKOH/g or lower is preferable because it maintains the water resistance of the coated layer and prevents the films from easily sticking together due to moisture absorption. However, in the polyurethane resin of the present invention, other hydrophilic groups, such as hydroxyl groups, ethers, sulfonic acids, phosphonic acids, quaternary amines, etc., may be introduced to compensate for the water solubility or water dispersibility of the polyurethane resin, within a range that does not degrade performance.

The carboxyl groups in the polyurethane resin may be neutralized with a basic compound. Examples of basic compounds used for neutralization include alkali metals such as sodium and potassium, alkaline earth metals such as magnesium and calcium, and organic amine compounds. Among these, organic amine compounds that readily dissociate from the carboxyl groups upon heating are preferred. Examples of organic amine compounds include linear, branched primary, secondary, or tertiary amines having 1 to 20 carbon atoms, such as ammonia, methylamine, ethylamine, propylamine, isopropylamine, butylamine, 2-ethylhexylamine, cyclohexylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, and ethylenediamine; cyclic amines such as morpholine, N-alkylmorpholine, and pyridine; and hydroxyl-containing amines such as monoisopropanolamine, methylethanolamine, methylisopropanolamine, dimethylethanolamine, diisopropanolamine, diethanolamine, triethanolamine, diethylethanolamine, and triethanolamine.

In the present invention, polycarbonate polyols are preferably used as other polyol components for synthesizing and polymerizing the urethane resin, and it is particularly preferable to include aliphatic polycarbonate polyols that have excellent heat resistance and hydrolysis resistance. Examples of aliphatic polycarbonate polyols include aliphatic polycarbonate diols and aliphatic polycarbonate triols, but aliphatic polycarbonate diols are preferably used. Examples of aliphatic polycarbonate diols used to synthesize and polymerize the polycarbonate structure urethane resin in the present invention include aliphatic polycarbonate diols obtained by reacting one or more diols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,8-nonanediol, neopentyl glycol, diethylene glycol, and dipropylene glycol with carbonates such as dimethyl carbonate, ethylene carbonate, and phosgene.

The number-average molecular weight of the polycarbonate polyol in the present invention 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 adhesion to the antistatic layer and adhesive layer. A number-average molecular weight of 3000 or less is preferable because it improves blocking resistance.

Examples of polyisocyanates used in the synthesis and polymerization of urethane resins in the present invention include aliphatic diisocyanates having aromatic rings such as xylylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate and 1,3-bis(isocyanatemethyl)cyclohexane, aliphatic diisocyanates such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, 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 aliphatic diisocyanates, alicyclic diisocyanates, or aliphatic diisocyanates having the aforementioned aromatic ring, there is no problem of yellowing, which is preferable.

Examples of chain extenders include glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, and 1,6-hexanediol; polyhydric alcohols such as glycerin, trimethylolpropane, and pentaerythritol; diamines such as ethylenediamine, hexamethylenediamine, and piperazine; amino alcohols such as monoethanolamine and diethanolamine; thiodiglycols such as thiodiethylene glycol; or water. In small amounts, polyols and polyamines with three or more functional groups may also be used.

The polyurethane resin of the present invention may have reactive groups such as blocked isocyanates at its ends or side chains to improve its rigidity.

(Crosslinking agent)
In the present invention, a crosslinking agent having a carboxyl group and an acid value of 30 to 50 mgKOH/g is used. Furthermore, the carboxyl group of the crosslinking agent may be neutralized with a basic compound, similar to the polyurethane resin described above. The acid value of the crosslinking agent having a carboxyl group is preferably 30 to 50 mgKOH/g, and more preferably 35 to 45 mgKOH/g. An acid value of 30 to 50 mgKOH/g or higher is preferable because it improves adhesion to the antistatic layer and adhesive layer. On the other hand, an acid value of 50 mgKOH/g or lower is preferable because it maintains the water resistance of the coated layer after application and prevents the films from easily sticking together due to moisture absorption. However, to compensate for the water solubility or water dispersibility of the crosslinking agent in the present invention, other hydrophilic groups, such as hydroxyl groups, ethers, sulfonic acids, phosphonic acids, quaternary amines, etc., may be introduced within a range that does not degrade performance.

Examples of crosslinking agents containing carboxyl groups include oxazoline compounds, carbodiimide compounds, epoxy compounds, and isocyanate compounds in which carboxyl groups have been introduced into the molecule. Furthermore, the carboxyl groups introduced into the molecule can be pre-neutralized with a basic compound to prevent intramolecular or intermolecular reactions. Among these crosslinking agents, isocyanate compounds are preferred because they readily allow for the introduction of carboxyl groups into the molecule, and blocked isocyanate compounds are particularly preferred.

Blocking agents include bisulfite compounds such as sodium bisulfite, pyrazole compounds such as 3,5-dimethylpyrazole, 3-methylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 4-nitro-3,5-dimethylpyrazole, phenols such as phenol and cresol, aliphatic alcohols such as methanol and ethanol, active methylene compounds such as dimethyl malonate and acetylacetone, mercaptans such as butyl mercaptan and dodecyl mercaptan, acid amides such as acetanilide and acetic acid amide, lactams such as ε-caprolactam and δ-valerolactam, acid imides such as succinimide and maleimide, oximes such as acetaldehyde oxime, acetone oxime, and methyl ethyl ketoxime, and amines such as diphenylaniline, aniline, and ethyleneimine.

The lower limit of the boiling point of the blocking agent, the blocked isocyanate, is preferably 150°C, more preferably 160°C, even more preferably 180°C, particularly preferably 200°C, and most preferably 210°C. The higher the boiling point of the blocking agent, the more suppressed the volatilization of the blocking agent is by heat application during the drying process after coating the coating solution or, in the case of in-line coating methods, during the film formation process. This suppresses the occurrence of minute surface irregularities on the coated surface and improves the transparency of the film. There is no particular upper limit to the boiling point of the blocking agent, but from the viewpoint of productivity, it is thought that the upper limit is around 300°C. Since the boiling point is related to the molecular weight, in order to raise the boiling point of the blocking agent, it is preferable to use a blocking agent with a large molecular weight. The molecular weight of the blocking agent is preferably 50 or more, more preferably 60 or more, and even more preferably 80 or more.

The upper limit of the dissociation temperature of the blocking agent is preferably 200°C, more preferably 180°C, even more preferably 160°C, particularly preferably 150°C, and most preferably 120°C. The blocking agent dissociates due to the heat applied during the drying process after application of the coating solution or, in the case of the in-line coating method, during the film formation process, generating regenerated isocyanate groups. As a result, crosslinking reactions with urethane resins and the like proceed, improving adhesion. If 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 resistance to heat and humidity.

The blocking agent used in the blocked isocyanate of the present invention has a dissociation temperature of 120°C or lower and a boiling point of 150°C or higher. Examples of blocking agents include the aforementioned sodium bisulfite, 3,5-dimethylpyrazole, 3-methylpyrazole, dimethyl malonate, diethyl malonate, acetone oxime, and methyl ethyl ketoxime. Among these, pyrazole compounds, represented by 3,5-dimethylpyrazole and 3-methylpyrazole, are preferred in terms of resistance to humid heat and yellowing.

The aforementioned blocked isocyanate is preferably bifunctional or more functional, and a trifunctional or more functional blocked isocyanate is even more preferable from the viewpoint of crosslinking properties of the coating film.

The trifunctional or more polyisocyanates, which are precursors to the blocked isocyanates of the present invention, can be suitably obtained by introducing isocyanate monomers. Examples include bilets, isocyanurates, and adducts obtained by modifying isocyanate monomers such as aromatic diisocyanates, aliphatic diisocyanates, aromatic aliphatic diisocyanates, or alicyclic diisocyanates having two isocyanate groups.
A biuret compound is a self-condensate having a biuret bond formed by the self-condensation of isocyanate monomers. Examples include the biuret compound of hexamethylene diisocyanate.
Isocyanurates are trimers of isocyanate monomers, such as the trimer of hexamethylene diisocyanate, the trimer of isophorone diisocyanate, and the trimer of tolylene diisocyanate.
Adduct compounds are isocyanate compounds with three or more functions, obtained by reacting an isocyanate monomer with a low-molecular-weight active hydrogen-containing compound with three or more functions. Examples include compounds obtained by reacting trimethylolpropane with hexamethylene diisocyanate, trimethylolpropane with tolylene diisocyanate, trimethylolpropane with xylylene diisocyanate, and trimethylolpropane with isophorone diisocyanate.

The aforementioned isocyanate monomers include 2,4-tole diisocyanate, 2,6-tole diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, 1,4-naphthylene diisocyanate, phenylene diisocyanate, tetramethylxylylene diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, and 2,2'-diphenylpropane-4,4'-diisocyanate. Examples include aromatic diisocyanates such as nate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, and xylylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate, and 1,3-bis(isocyanate-methyl)cyclohexane; hexamethylene diisocyanate; and aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate. From the viewpoint of transparency, resistance to yellowing, adhesion, and resistance to humid and heat, aliphatic and alicyclic isocyanates and their modified forms are preferred.

In the present invention, other resins may be used in combination as long as they do not affect performance. Examples of resins to be used in combination include carboxyl group-free polyurethane, polyester resin, acrylic resin, cellulose resin, polyolefin resin, and polyacetal resin. Among these resins, polyester resin is particularly preferred because its combination improves adhesion to the antistatic layer and adhesive layer. Furthermore, when polyester resin is used in combination, it is possible to include 1.5 times or more of it than the combined content of the carboxyl group-containing polyurethane resin and the carboxyl group-containing crosslinking agent. It is presumed that this effect is due to a synergistic effect occurring where the polyester resin has better affinity to the polyester resin, which is the base material, than the carboxyl group-containing polyurethane resin or the carboxyl group-containing crosslinking agent, and therefore tends to localize on the base material side in the thickness direction, thereby improving adhesion to the base material interface, and the carboxyl group-containing polyurethane resin and carboxyl group-containing crosslinking agent localized on the surface improve adhesion to the binder resin contained in the antistatic layer and adhesive layer.

(Polyester resin)
The polyester resin used in combination with the coating layer in the present invention may be linear, but more preferably it is a polyester resin composed of a dicarboxylic acid and a branched diol (glycol). The dicarboxylic acid referred to here may be terephthalic acid, isophthalic acid, or 2,6-naphthalenedicarboxylic acid as its main component, as well as aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid. Furthermore, branched glycols are diols having branched alkyl groups, and examples include 2,2-dimethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, 2-methyl-2-butyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-2-isopropyl-1,3-propanediol, 2-methyl-2-n-hexyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, 2-ethyl-2-n-hexyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 2-n-butyl-2-propyl-1,3-propanediol, and 2,2-di-n-hexyl-1,3-propanediol.

Regarding the polyester resin described above, the branched glycol component, which is the more preferred embodiment described above, is preferably contained in the total glycol component at a rate of 10 mol% or more, and more preferably 20 mol% or more. A rate of 10 mol% or more is preferable because it prevents excessive crystallinity and maintains the adhesion of the coated layer. The upper limit of the glycol component in the total glycol component is preferably 80 mol% or less, and more preferably 70% by mass or less. A rate of 80 mol% or less is preferable because it prevents an increase in the oligomer concentration, which is a by-product, and maintains the transparency of the coated layer. Among glycol components other than the above compounds, ethylene glycol is the most preferred. In small amounts, diethylene glycol, propylene glycol, butanediol, hexanediol, or 1,4-cyclohexanedimethanol may also be used.

The most preferred dicarboxylic acid as a component of the polyester resin is terephthalic acid or isophthalic acid. In addition to the above dicarboxylic acid, it is preferable to copolymerize 5-sulfoisophthalic acid or the like in a value of 1 to 10 mol% in order to impart water dispersibility to the copolymerized polyester resin. Examples include sulfoterephthalic acid, 5-sulfoisophthalic acid, and 5-sodium sulfoisophthalic acid.

When the total solid content of the resin and crosslinking agent in the coating solution forming the easy-adhesion layer is taken as 100% by mass, a polyester resin content of 10% by mass or more is preferable as it results in good adhesion between the easy-adhesion layer and the polyester film substrate. The upper limit of the polyester resin content is preferably 65% by mass or less, and more preferably 60% by mass or less. A polyester resin content of 70% by mass or less is preferable as it results in good resistance to moisture and heat.

Other resins besides the aforementioned polyester resin may be used in the easy-adhesion layer, as long as they do not degrade the performance of this invention. Typical examples of resins other than the polyester resin are polyurethane resins having carboxyl groups, but other resins may also be included, or the resin may consist solely of polyurethane resins having carboxyl groups.
In that case, if the total solid content of the resin and crosslinking agent in the coating solution that forms the easy-adhesion layer is taken as 100% by mass, the content of resins other than polyester resin is preferably 40% by mass or less, more preferably 30% by mass or less, and particularly preferably 20% by mass or less. However, the total content of resins other than polyester resin and polyester resin is preferably 70% by mass or less. The respective content of the aforementioned polyurethane resin and crosslinking agent in the coating solution that forms the coating layer is preferably 3% by mass or more as the total solid content of the resin and crosslinking agent.
A content of 3% by mass or more is preferable as it provides good adhesion to the antistatic layer and adhesive layer. A more preferable content range is 3.5 to 90% by mass, even more preferably 7 to 80% by mass, and particularly preferably 10.5 to 70% by mass.

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

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. Furthermore, other general inorganic particles such as calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, calcium fluoride in combination, etc., and organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based particles are also possible.

The average particle size of the particles in the easy-adhesion 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 of inert particles is preferable because it facilitates the formation of irregularities on the film surface, improving handling properties such as film slipperiness and winding ability, and resulting in good processability during lamination. On the other hand, an average particle size of 2.0 μm or less of inert particles is preferable because it reduces the likelihood of particle detachment. The particle concentration in the easy-adhesion layer is preferably 1 to 20% by mass of the solid component.

The average particle size was measured by observing the particles in a cross-section of a laminate of a polyester film substrate and an easy-adhesion layer (hereinafter also referred to as a laminated polyester film) using a scanning electron microscope. Thirty particles were observed, and the average value was used as the average particle size.

The shape of the particles is not particularly limited as long as it satisfies the objectives of the present invention; spherical particles and 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.

(Manufacturing of laminated polyester film)
The method for producing the laminated polyester film of 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.

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 sheet 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.

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 using a roll heated to 80 to 120°C to obtain a uniaxially stretched 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, the sheet is stretched 2.5 to 5.0 times in a tenter. After stretching, the sheet is then guided into a heat treatment zone and heat treatment is performed to complete the crystal orientation.

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 is preferable because it ensures sufficient curing and good blocking properties in the presence of liquid water, eliminating the need for a longer drying time. On the other hand, the upper limit of the heat treatment zone temperature is preferably 250°C, and more preferably 240°C. A temperature of 240°C or lower is preferable because it avoids the risk of deterioration in the film's physical properties.

The easy-adhesion layer can be formed after or during the film manufacturing process. In particular, from the viewpoint of productivity, it is preferable to form the easy-adhesion layer at any stage of the film manufacturing process, i.e., by applying the coating solution to at least one side of the PET film after it has been unstretched or uniaxially stretched, and then stretching and heat-treating it in at least one axial direction.

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, and curtain coating method. These methods can be used individually or in combination.

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

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. Generally, 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 0.2% or more.

(Antistatic layer)
The antistatic polyester film of the present invention has an antistatic layer on top of an easily adhesive layer in a laminated polyester film. The antistatic layer may be laminated on one side or on both sides. Laminating the antistatic layer is preferable because it can suppress peeling charge from the adherend and suppress the adhesion of foreign matter, even when an adhesive layer is laminated and the film is used as a protective film.

The means for laminating the antistatic layer are not particularly limited, and known methods such as coating, vacuum deposition, and bonding can be used. However, from a cost standpoint, it is preferable to apply a coating liquid containing an antistatic agent by coating.

As antistatic agents, polymers utilizing ion conduction such as cationic compounds, surfactants, silicon oxide films, conductive metal compounds, and π-electron conjugated conductive polymers can be used. However, from the viewpoint of antistatic properties under low humidity, π-electron conjugated conductive polymers are preferred. Furthermore, π-electron conjugated conductive polymers are preferred because they can maintain a high level of antistatic performance regardless of moisture in the air, and therefore have good antistatic performance in various usage environments of protective films.

Examples of π-electron conjugated conductive polymers include aniline polymers containing aniline or its derivatives as constituent units, pyrrole polymers containing pyrrole or its derivatives as constituent units, acetylene polymers containing acetylene or its derivatives as constituent units, and thiophene polymers containing thiophene or its derivatives as constituent units. For high transparency, π-electron conjugated conductive polymers without nitrogen atoms are preferred, and among these, thiophene polymers containing thiophene or its derivatives as constituent units are preferred in terms of transparency, with polyalkylenedioxythiophene being particularly preferred. Examples of polyalkylenedioxythiophene include polyethylenedioxythiophene, polypropylenedioxythiophene, and poly(ethylene/propylene)dioxythiophene.

Furthermore, thiophene-based polymers containing thiophene or its derivatives as constituent units may be doped with a doping agent to further improve their antistatic properties. For example, 0.1 to 500 parts by mass per 100 parts by mass of the polymer containing thiophene or its derivatives as constituent units may be added. If the amount is too small, electron transfer becomes difficult, leading to a decrease in antistatic performance. Conversely, if the amount is too large, there is a problem of reduced dispersibility in the solvent. This doping agent includes LiCl, _R1-30 COOLi ( _R1-30 : saturated hydrocarbon group with 1 to 30 carbon atoms), _{R1-30 SO3} Li, _R1-30 COONa, _R1-30 SO3 _Na , _{R1-30 COOK} , _{R1-30 SO3} K, tetraethylammonium _{, I2} , _BF3 Na, _BF4 Na, HClO4, _{CF3 SO3} H, FeCl3, tetracyanoquinoline (TCNQ), _{Na2 B10 Cl10} Examples include phthalocyanine, porphyrin, glutamic acid, alkyl sulfonates, sodium polystyrene sulfonate (K, Li) salt, styrene-sodium styrene sulfonate (K, Li) salt copolymer, polystyrene sulfonate anion, and styrene sulfonate-styrene sulfonate anion copolymer.

In the present invention, the antistatic agent contained in the antistatic layer is preferably present in an amount of 1% by mass or more, and more preferably 10% by mass or more, based on 100 parts by mass of the solid content of the antistatic layer. When a π-electron conjugated conductive polymer is used as the antistatic agent, and the doping agent is used, the content of the π-electron conjugated conductive polymer in the antistatic layer as defined in this application refers to the total amount of the conductive polymer and the doping agent.
For example, the amount of antistatic agent may be 80% by mass or less, or 50% by mass or less.

The antistatic layer of the present invention preferably contains a binder resin. While the binder resin is not particularly limited, specific examples of polymers include polyester resins, acrylic resins, urethane resins, polyolefin resins, polyvinyl resins (such as polyvinyl alcohol), polyalkylene glycols, polyalkyleneimines, methylcellulose, hydroxycellulose, and starches. Among these, polyester resins, acrylic resins, and urethane resins are preferred from the viewpoint of adhesion to the polyester film. Acrylic resins are even more preferred due to the ease of molecular design and molecular weight design.

The binder resin preferably has reactive functional groups. While not particularly limited, hydroxyl groups, carboxyl groups, amino groups, acrylate groups, and epoxy groups are preferred, with hydroxyl groups and carboxyl groups being more preferred.

The binder resin may have a portion that exhibits release properties, such as a silicone component or a long-chain alkyl group. When an adhesive layer is laminated, it is preferable to have an antistatic layer with release properties on the opposite side of the adhesive layer of the laminated film, as this prevents blocking and other issues even when the film is wound into a roll.

(Crosslinking agent)
In the present invention, the antistatic layer may be formed containing a crosslinking agent in order to form a crosslinked structure in the antistatic layer. Including a crosslinking agent is preferable because it improves adhesion to the easily bonded layer, improves durability, and suppresses the deterioration of antistatic performance even when treated under high temperature and high humidity conditions. Specific crosslinking agents include urea-based, epoxy-based, melamine-based, isocyanate-based, oxazoline-based, carbodiimide-based, and aziridine-based agents. Melamine-based, oxazoline-based, carbodiimide-based, and aziridine-based agents are particularly preferred. Furthermore, catalysts and the like can be used as needed to promote the crosslinking reaction.

The crosslinking agent contained in the antistatic layer of the present invention is preferably present in an amount of 5% by mass or more, and more preferably 10% by mass or more, based on 100 parts by mass of solid content in the antistatic layer. An amount of 5% by mass or more is preferable because it can improve the moisture and heat resistance of the antistatic layer. Furthermore, if the crosslinking agent is self-crosslinking, a binder resin is not required. For example, the amount of crosslinking agent may be 90% by mass or less, or 80% by mass or less.

In the present invention, a surfactant may be used in the antistatic layer to improve its appearance. Examples of surfactants that can be used include nonionic surfactants such as polyoxyethylene octylphenyl ether, polyoxyethylene alkyl ether, and polyoxyethylene sorbitan fatty acid ester, as well as fluorine-based surfactants such as fluoroalkyl carboxylic acid, perfluoroalkyl carboxylic acid, perfluoroalkylbenzenesulfonic acid, perfluoroalkyl quaternary ammonium, and perfluoroalkyl polyoxyethylene ethanol, and silicone-based surfactants.

In addition to the above, the antistatic layer may contain, as necessary, lubricants, dyes, ultraviolet absorbers, silane coupling agents, etc., to the extent that it does not hinder the objectives of the present invention.

The thickness of the antistatic layer of the present invention is preferably 0.005 μm or more and 1 μm or less. More preferably, it is 0.01 μm or more and 0.5 μm or less, and even more preferably, 0.01 μm or more and 0.2 μm or less. A thickness of 0.005 μm or more of the antistatic layer is preferable because it provides an antistatic effect. On the other hand, a thickness of 1 μm or less is preferable because it results in less discoloration and higher transparency.

The surface resistivity of the antistatic film of the present invention is preferably 1 × ^10¹⁰ Ω/□ or less. More preferably, it is 1 × ^10⁹ Ω/□ or less, even more preferably, 1 × ^10⁷ Ω/□ or less, and still more preferably 1 × ^10⁶ Ω/□ or less. A surface resistivity of 1 × ^10¹⁰ Ω/□ or less is preferable because it suppresses the adhesion of foreign matter to the laminated polyester and suppresses peeling charge when the adhesive layer is laminated and peeled off. Furthermore, there is no particular lower limit for the surface resistivity of the antistatic film, but it is preferably 1 × ^10³ Ω/□ or more. It is undesirable to make the surface resistivity of the antistatic film less than 1 × ^10³ Ω/□ because it increases the processing cost of the antistatic layer.

The haze of the antistatic film used in the present invention is preferably 3% or less. More preferably 1.5% or less, and even more preferably 1.0% or less. If it is 0.8% or less, it is extremely preferable. If it is 3% or less, it is preferable because it allows for visual inspection of the protective film when it is bonded to the substrate, and is particularly preferable when the substrate is a component for optical applications.
The haze is preferably lower, may be substantially 0% (or 0% or more), and may be, for example, 0.1% or more.

The average surface roughness (Sa) of the surface of the antistatic film used in the present invention is preferably in the range of 1 to 40 nm, more preferably 1 to 30 nm, and even more preferably 1 to 10 nm. The maximum protrusion height (P) of the surface of the antistatic film used in the present invention is preferably 2 μm or less, more preferably 1.5 μm or less, and even more preferably 0.8 μm or less. If Sa is 40 nm or less and P is 2 μm or less, it is preferable because there is no risk of roughening the adhesive surface when the adhesive layer is laminated and wound into a roll.

Methods for applying and laminating an antistatic layer to the surface of a base film include applying a coating solution, in which the aforementioned antistatic agent and binder resin are dispersed and dissolved in a solvent, using methods such as gravure roll coating, reverse roll coating, knife coater, dip coat, bar coat, and spin coat. However, there are no particular restrictions on the coating method suitable for conductive compositions. Furthermore, the coating layer can be applied using an in-line coating method, where the coating layer is applied during the film manufacturing process, or an off-line coating method, where the coating layer is applied after film manufacturing.

The drying temperature for forming the antistatic layer using the method described above is usually 60°C to 150°C, preferably 90°C to 140°C. A temperature of 60°C or higher is preferable from the viewpoint of improving productivity, as it allows for a shorter processing time. Furthermore, if a crosslinking agent is included, this is preferable because it allows the crosslinking reaction to proceed sufficiently. On the other hand, a temperature of 150°C or lower is preferable because it maintains the flatness of the film.

The antistatic film of the present invention can have an adhesive layer laminated onto it by applying and curing an adhesive. The adhesive is not particularly limited and can be used, and the resulting laminated film can be used as a protective film. The side on which the adhesive layer is laminated can be either side of the antistatic film. When using an antistatic film having an antistatic layer on only one side, it is preferable that the antistatic layer be on the side opposite to the side on which the adhesive layer is laminated.

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.

(1) Haze The haze of the obtained antistatic polyester film was measured in accordance with JIS K 7136:2000 using a turbidimeter (Nippon Denshoku, NDH5000).

(2) Acid value The acid value of the resin and crosslinking agent was measured by the titration method described in JIS K1557-5:2007.
However, in the case of carboxyl groups neutralized with amines, etc., the amines were removed by high-temperature treatment, or the amines were liberated and removed beforehand by treatment with hydrochloric acid, 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.

(3) Blocking resistance Two film samples were placed on top of each other with the coated layers facing each other, a load of 98 kPa was applied, and they were left in contact for 24 hours in a 50°C atmosphere. After that, the films were peeled off and the peeling state was judged according to the following criteria.
○: The coating layer does not shift and can be easily peeled off.
△: The coating layer is maintained, but the surface layer of the coating layer has partially transferred to the mating surface.
×: The two films are stuck together and cannot be separated, or even if they can be separated, the film substrate is cleaved.

(4) Adhesion to the antistatic layer Using a cutter guide with a 2 mm gap spacing, 100 grid-like cuts were made on the surface of the antistatic layer laminated on the easy-adhesion layer of the laminated polyester film, penetrating the antistatic layer and reaching the film substrate. Next, cellophane adhesive tape (Nichiban, No. 405; 24 mm wide) was applied to the grid-like cut surfaces and firmly adhered. Then, the cellophane adhesive tape was peeled vertically from the surface of the antistatic layer of the laminated film. After performing the adhesive tape application and peeling operation a total of five times at the same location, the number of grids that peeled off from the surface of the antistatic layer of the laminated film was visually counted, and the adhesion between the antistatic layer and the film substrate was determined using the following formula. Note that grids that were partially peeled off were also counted as peeled grids, and the adhesion of the antistatic layer was determined as shown in the formula below.
Adhesion of the antistatic layer (%) = 100 - (number of squares that have peeled off)
The adhesion of the antistatic layer was determined according to the following criteria.
◎: 100%, ○: 96-99%, △: 80-95%, ×: less than 80%. A score of ○ or higher was considered a passing grade.

(5) Humidity and heat resistance An antistatic polyester film, laminated with an antistatic layer prepared in the same manner as in (4) above, was left for 500 hours in an environment of 80°C and 80% RH with the coated surface vertical and without contact with any other films or materials. After treatment, it was left for 10 minutes in an environment of 23°C and 65% RH with no contact with any 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.

(6) Surface Resistivity The surface resistance of the release film surface of the present invention was measured using a surface resistance measuring instrument (SIMCO Japan Co., Ltd., Work Surface Tester ST-3) after 24 hours of humidity control under conditions of 23°C and 55%, and evaluated according to the following criteria.

◎: Surface resistance less than ^10⁷ Ω/□ ○: Surface resistance between ^10⁷ and ^10⁸ Ω/□
△: Surface resistance value is ^10⁹ to ^10¹⁰ Ω/□
×: Surface resistance value is ¹⁰ Ω/□ or higher

(Polymerization of polyurethane resin A-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, 82.8 parts by mass of hydrogenated m-xylylene diisocyanate, 25.0 parts by mass of dimethylolpropanoic acid, 21.0 parts by mass of 1,6-hexanediol, 150.0 parts by mass of a polyester diol with a number average molecular weight of 2000 consisting of adipic acid and 1,4-butanediol, and 110 parts by mass of acetone as a solvent were added. The mixture was stirred at 75°C under a nitrogen atmosphere for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, the reaction solution was cooled to 40°C, and then 19.8 parts by mass of triethylamine was added to obtain a polyurethane polymer solution. Next, in a reaction vessel equipped with a homodisperser capable of high-speed stirring, 500 g of water was added and the temperature was adjusted to 25°C. The polyurethane polymer solution was added and dispersed in water while stirring at 2000 ^min⁻¹ . After that, the solvent, acetone, was removed under reduced pressure. By adjusting the concentration with water, a solution containing 35% by mass of solids, including polyurethane resin (A-1) with an acid value of 37.5 mgKOH/g, was prepared.

(Polymerization of polyurethane resin A-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, 63.0 parts by mass of hydrogenated m-xylylene diisocyanate, 21.0 parts by mass of dimethylolpropanoic acid, 147.0 parts by mass of polycarbonate diol (1,6-hexanediol type) with a number average molecular weight of 2000, and 110 parts by mass of acetone as a solvent were added. The mixture was stirred at 75°C under a nitrogen atmosphere for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, the reaction solution was cooled to 40°C, and then 16.6 parts by mass of triethylamine was added to obtain a polyurethane polymer solution. Next, in a reaction vessel equipped with a homodisperser capable of high-speed stirring, 500 g of water was added and the temperature was adjusted to 25°C. The polyurethane polymer solution was then added and dispersed in water while stirring at 2000 ^min⁻¹ . After that, the solvent, acetone, was removed under reduced pressure. By adjusting the concentration with water, a solution containing 35% by mass of solids, including polyurethane resin (A-2) with an acid value of 36.3 mgKOH/g, was prepared.

(Polymerization of polyurethane resin A-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, 64.5 parts by mass of hydrogenated diphenylmethane diisocyanate, 21.5 parts by mass of dimethylolpropanoic acid, 11.2 parts by mass of neopentyl glycol, 150.5 parts by mass of polycarbonate diol (1,6-hexanediol type) with a number average molecular weight of 2000, and 110 parts by mass of acetone as a solvent were added. The mixture was stirred at 75°C under a nitrogen atmosphere for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, the reaction solution was cooled to 40°C, and then 17.0 parts by mass of triethylamine was added to obtain a polyurethane polymer solution. Next, in a reaction vessel equipped with a homodisperser capable of high-speed stirring, 500 g of water was added and the temperature was adjusted to 25°C. The polyurethane polymer solution was then added and dispersed in water while stirring at 2000 ^min⁻¹ . After that, the solvent, acetone, was removed under reduced pressure. By adjusting the concentration with water, a solution containing 35% by mass of solids, including polyurethane resin (A-3) with an acid value of 36.0 mgKOH/g, was prepared.

(Polymerization of polyurethane resin A-4)
In a four-necked flask equipped with a stirrer, a Liebig condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 83.4 parts by mass of hydrogenated m-xylylene diisocyanate, 16.9 parts by mass of dimethylolpropanoic acid, 28.4 parts by mass of 1,6-hexanediol, 151.0 parts by mass of a polyester diol with a number average molecular weight of 2000 consisting of adipic acid and 1,4-butanediol, and 110 parts by mass of acetone as a solvent were added. The mixture was stirred at 75°C under a nitrogen atmosphere for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, the reaction solution was cooled to 40°C, and then 13.3 parts by mass of triethylamine was added to obtain a polyurethane polymer solution. Next, in a reaction vessel equipped with a homodisperser capable of high-speed stirring, 500 g of water was added and the temperature was adjusted to 25°C. The polyurethane polymer solution was added and dispersed in water while stirring at 2000 ^min⁻¹ . After that, the solvent, acetone, was removed under reduced pressure. A 35% by mass solution of polyurethane resin (A-4) with a solid content of 25.3 mg KOH/g was prepared by adjusting the concentration with water.

(Polymerization of polyurethane resin A-5)
In a four-necked flask equipped with a stirrer, a Liebig condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 104.9 parts by mass of hydrogenated m-xylylene diisocyanate, 41.8 parts by mass of dimethylolpropanoic acid, 19.0 parts by mass of 1,6-hexanediol, 152.0 parts by mass of a polyester diol with a number average molecular weight of 2000 consisting of adipic acid and 1,4-butanediol, and 110 parts by mass of acetone as a solvent were added. The mixture was stirred at 75°C under a nitrogen atmosphere for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, the reaction solution was cooled to 40°C, and then 33.1 parts by mass of triethylamine was added to obtain a polyurethane polymer solution. Next, in a reaction vessel equipped with a homodisperser capable of high-speed stirring, 500 g of water was added and the temperature was adjusted to 25°C. The polyurethane polymer solution was added and dispersed in water while stirring at 2000 ^min⁻¹ . After that, the solvent, acetone, was removed under reduced pressure. A 35% by mass solution of polyurethane resin (A-5) with a solid content of 55.0 mgKOH/g was prepared by adjusting the concentration with water.

(Polymerization of polyurethane resin A-6)
In a four-necked flask equipped with a stirrer, a Liebig condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 45.0 parts by mass of hydrogenated m-xylylene diisocyanate, 20.0 parts by mass of 1,6-hexanediol, 149.0 parts by mass of polyethylene glycol with a number average molecular weight of 2000, and 110 parts by mass of acetone as a solvent were added. The mixture was stirred at 75°C under a nitrogen atmosphere for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, the reaction solution was cooled to 40°C, and then 500 g of water was added to a reaction vessel equipped with a homodisperser capable of high-speed stirring, and the temperature was adjusted to 25°C. The polyurethane polymer solution was then added and dispersed in water while stirring at 2000 ^min⁻¹ . After that, the solvent, acetone, was removed under reduced pressure. By adjusting the concentration with water, a 35% by mass solids solution containing polyurethane resin (A-6) with an acid value of 0.2 mg KOH/g was prepared.

(Polymerization of polyurethane resin A-7)
In a four-necked flask equipped with a stirrer, a Liebig condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 43.8 parts by mass of hydrogenated diphenylmethane diisocyanate, 12.9 parts by mass of dimethylolbutanoic acid, 153.4 parts by mass of polycarbonate diol (1,6-hexanediol type) with a number average molecular weight of 2000, and 110 parts by mass of acetone as a solvent were added. The mixture was stirred at 75°C under a nitrogen atmosphere for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, the reaction solution was cooled to 40°C, and then 8.8 parts by mass of triethylamine was added to obtain a polyurethane polymer solution. Next, in a reaction vessel equipped with a homodisperser capable of high-speed stirring, 500 g of water was added and the temperature was adjusted to 25°C. The polyurethane polymer solution was then added and dispersed in water while stirring at 2000 ^min⁻¹ . After that, the solvent, acetone, was removed under reduced pressure. A 35% by mass solution of polyurethane resin (A-7) with a solid content of 23.1 mg KOH/g was prepared by adjusting the concentration with water.

(Synthesis of crosslinking agent B-1)
In a flask equipped with a stirrer, thermometer, and reflux condenser, 59.5 parts by mass of hexamethylene diisocyanate, 10.7 parts by mass of neopentyl glycol, 11.0 parts by mass of dimethylolbutanoic acid, and 20.0 parts by mass of N-methylpyrrolidone as a solvent were added. The mixture was stirred at 80°C under a nitrogen atmosphere for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, 29.9 parts by mass of 2-butanone oxime was added dropwise to the reaction solution, and it was held at 80°C under a nitrogen atmosphere for 1 hour. After that, the infrared spectrum of the reaction solution was measured, and it was confirmed that the absorption of the isocyanate group had disappeared. The reaction solution was then cooled to 40°C, and 7.9 parts by mass of triethylamine was added. After stirring for 1 hour, an appropriate amount of water was added to prepare a 40% by mass solids block isocyanate crosslinking agent (B-1) solution. The acid value equivalent to the solids of crosslinking agent B-1 was 37.6 mgKOH/g.

(Synthesis of crosslinking agent B-2)
In a flask equipped with a stirrer, thermometer, and reflux condenser, 66.6 parts by mass of a polyisocyanate compound having an isocyanurate structure derived from hexamethylene diisocyanate (Duranate TPA, manufactured by Asahi Kasei Chemicals), 17.5 parts by mass of N-methylpyrrolidone, and 21.7 parts by mass of 3,5-dimethylpyrazole were added dropwise, and the mixture was held at 70°C under a nitrogen atmosphere for 1 hour. Then, 9.0 parts by mass of dimethylolpropanoic acid were added dropwise. After measuring the infrared spectrum of the reaction solution and confirming that the absorption of the isocyanate group had disappeared, 6.3 parts by mass of N,N-dimethylethanolamine was added. After stirring for 1 hour, an appropriate amount of water was added to prepare a 40% by mass solids block isocyanate crosslinking agent (B-2) solution. The acid value of crosslinking agent B-2 equivalent to the solids content was 41.2 mgKOH/g.

(Synthesis of crosslinking agent B-3)
In a flask equipped with a stirrer, thermometer, and reflux condenser, 150.0 parts by mass of water and 250.0 parts by mass of methoxypropyl alcohol were charged and heated to 80°C under a nitrogen atmosphere. Then, a monomer mixture consisting of 126.0 parts by mass of methyl methacrylate, 210.0 parts by mass of 2-isopropenyl-2-oxazoline and 53.0 parts by mass of triethylamine methacrylate, and a polymerization initiator solution consisting of 18.0 parts by mass of 2,2'-azobis(2-amidinopropane) dihydrochloride and 170.0 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 oxazoline-based crosslinking agent (B-3) solution with a solid content of 40% by mass. The acid value equivalent to the solid content of crosslinking agent B-3 was 39.8 mgKOH/g.

(Polymerization of crosslinking agent B-4)
In a flask equipped with a stirrer, thermometer, and reflux condenser, 65.0 parts by mass of a polyisocyanate compound having an isocyanurate structure derived from hexamethylene diisocyanate (Duranate TPA, manufactured by Asahi Kasei Chemicals), 17.5 parts by mass of N-methylpyrrolidone, 29.2 parts by mass of 3,5-dimethylpyrazole, and 21.9 parts by mass of polyethylene glycol monomethyl ether with a number average molecular weight of 500 were added, and the mixture was held at 70°C for 2 hours under a nitrogen atmosphere. Then, 4.0 parts by mass of trimethylolpropane was added dropwise. The infrared spectrum of the reaction solution was measured, and after confirming that the absorption of the isocyanate group had disappeared, 280.0 parts by mass of water was added. An appropriate amount of water was added to prepare a block polyisocyanate-based crosslinking agent (B-4) solution with a solid content of 40% by mass. The acid value of the crosslinking agent B-4 equivalent to the solid content was 0.0 mgKOH/g.

(Polymerization of crosslinking agent B-5)
In a flask equipped with a stirrer, thermometer, and reflux condenser, 66.04 parts by mass of a polyisocyanate compound having an isocyanurate structure derived from hexamethylene diisocyanate (Duranate TPA, manufactured by Asahi Kasei Chemicals), 17.50 parts by mass of N-methylpyrrolidone, and 25.19 parts by mass of 3,5-dimethylpyrazole were added dropwise, and the mixture was held at 70°C for 1 hour under an ambient atmosphere. Subsequently, 5.27 parts by mass of dimethylolpropanoic acid were added dropwise. After measuring the infrared spectrum of the reaction solution and confirming that the absorption of the isocyanate group had disappeared, 5.59 parts by mass of N,N-dimethylethanolamine and 132.5 parts by mass of water were added. An appropriate amount of water was added to prepare a block polyisocyanate-based crosslinking agent (B-5) solution with a solid content of 40% by mass. The acid value of crosslinking agent B-5 equivalent to the solid content was 22.8 mgKOH/g.

(Synthesis of crosslinking agent B-6)
In a flask equipped with a stirrer, thermometer, and reflux condenser, 59.5 parts by mass of hexamethylene diisocyanate, 6.8 parts by mass of neopentyl glycol, 16.6 parts by mass of dimethylolbutanoic acid, and 20.0 parts by mass of N-methylpyrrolidone as a solvent were added. The mixture was stirred at 80°C under a nitrogen atmosphere for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, 30.3 parts by mass of 2-butanone oxime was added dropwise to the reaction solution, and it was held at 80°C under a nitrogen atmosphere for 1 hour. After that, the infrared spectrum of the reaction solution was measured, and it was confirmed that the absorption of the isocyanate group had disappeared. The reaction solution was then cooled to 40°C, and 11.9 parts by mass of triethylamine was added. After stirring for 1 hour, an appropriate amount of water was added to prepare a 40% by mass solids block isocyanate crosslinking agent (B-6) solution. The acid value equivalent to the solids of crosslinking agent B-6 was 55.4 mgKOH/g.

(Manufacturing of polyester resin C-1)
In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 194.2 parts by mass of dimethyl terephthalate, 184.5 parts by mass of dimethyl isophthalate, 14.8 parts by mass of dimethyl-5-sodium sulfoisophthalate, 233.5 parts by mass of diethylene glycol, 136.6 parts by mass of ethylene glycol, and 0.2 parts by mass of tetra-n-butyl titanate were charged, and a transesterification reaction was carried out at a temperature of 160°C to 220°C for 4 hours. The temperature was then raised to 255°C, the reaction system was gradually depressurized, and the reaction was carried out under a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain copolymerized polyester resin (CR-1). The obtained copolymerized polyester resin (CR-1) was pale yellow and transparent. The reduced viscosity of the copolymerized polyester resin (CR-1) was measured to be 0.70 dl/g.
Furthermore, 15 parts by mass of copolymerized polyester resin (CR-1) and 15 parts by mass of ethylene glycol n-butyl ether were placed in a reactor equipped with a stirrer, thermometer, and reflux device, and the mixture was heated and stirred at 110°C to dissolve the resin. After the resin was completely dissolved, 70 parts by mass of water were gradually added to the polyester solution while stirring, and after the addition, the solution was cooled to room temperature while stirring. An appropriate amount of water was added to prepare a polyester resin (C-1) solution with a solid content of 30% by mass. The acid value equivalent to the solid content of polyester resin C-1 was 0.9 mgKOH/g.

(Manufacturing of polyester resin C-2)
In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 194.2 parts by mass of dimethyl terephthalate, 194.2 parts by mass of dimethyl isophthalate, 233.5 parts by mass of diethylene glycol, 136.6 parts by mass of ethylene glycol, and 0.2 parts by mass of tetra-n-butyl titanate were charged, and a transesterification reaction was carried out at a temperature of 160°C to 220°C for 4 hours. The temperature was then raised to 255°C, the reaction system was gradually depressurized, and the reaction was carried out under a reduced pressure of 30 Pa for 1 hour. Furthermore, nitrogen was introduced into the system to release the reduced pressure, and the system was cooled to 200°C. 28.0 parts by mass of trimellitic anhydride was added to the system while stirring, and the addition reaction was carried out for a further 2 hours to obtain copolymerized polyester resin (CR-2). The obtained copolymerized polyester resin (CR-2) was pale yellow and transparent. The reduced viscosity of the copolymerized polyester resin (CR-2) was measured to be 0.35 dl/g.
Furthermore, 15 parts by mass of copolymerized polyester resin (CR-2) and 15 parts by mass of tetrahydrofuran were placed in a reactor equipped with a stirrer, thermometer, and reflux device, and heated and stirred at 70°C to dissolve the resin. After the resin was completely dissolved, 31 parts by mass of triethylamine and 70 parts by mass of water were gradually added to the polyester solution while stirring. After the addition, the system was reduced in pressure to remove the tetrahydrofuran, and the system was cooled to room temperature. An appropriate amount of water was added to prepare polyester resin (C-2) solution C-2 with a solid content of 30% by mass. The acid value equivalent to the solid content of polyester resin C-2 was 37.4 mgKOH/g.

(Manufacturing of acrylic resin D-1)
40 parts of propylene glycol monomethyl ether were placed in a flask equipped with a stirrer, thermometer, and reflux condenser, and heated and maintained at 100°C. A mixture of 60.0 parts by mass of n-butyl acrylate, 42.0 parts by mass of methyl methacrylate, 2.9 parts by mass of 2-hydroxyethyl methacrylate, 5.7 parts by mass of acrylic acid, and 5 parts of azobisisobutyronitrile was added dropwise over 3 hours. After dropwise addition, the mixture was allowed to mature at the same temperature for 2 hours. Then, the reaction solution was cooled to 40°C, and 8.4 parts by mass of triethylamine and 165 parts by mass of water were added while stirring. After stirring for 1 hour, an appropriate amount of water was added to prepare an acrylic resin (D-1) solution with a solid content of 35% by mass. The acid value corresponding to the solid content of this acrylic resin D-1 was 40.1 mgKOH/g.

(Manufacturing of acrylic resin D-2)
A four-necked flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet was charged with 231 parts by mass of methyl methacrylate (MMA), 130 parts by mass of stearyl methacrylate (SMA), 100 parts by mass of hydroxyethyl methacrylate (HEMA), 33 parts by mass of methacrylic acid (MAA), and 1153 parts by mass of isopropyl alcohol (IPA). The flask was heated to 80°C while stirring. The flask was stirred for 3 hours while maintaining the temperature at 80°C, after which 0.5 parts by mass of 2,2-azobis-2-methyl-N-2-hydroxyethylpropionamide was added to the flask. The flask was purged with nitrogen while the temperature was raised to 120°C, and the mixture was stirred at 120°C for 2 hours.
Next, the mixture was subjected to a reduced pressure of 1.5 kPa at 120°C to remove unreacted raw materials and solvent, yielding a long-chain alkyl group-containing acrylic resin. The flask was returned to atmospheric pressure and cooled to room temperature, and 1592 parts by mass of IPA aqueous solution (water content 50% by mass) was added and mixed. Then, while stirring, ammonia was added using a dropping funnel to neutralize the long-chain alkyl group-containing acrylic resin until the pH of the solution was in the range of 5.5 to 7.5, yielding a long-chain alkyl group-containing acrylic resin (D-2) solution with a solid content concentration of 20% by mass. The oxidation equivalent to the solid content of this acrylic resin (D-2) was 104 mg KOH/g.

(Manufacturing of polyester resin E-1 for base materials)
(Preparation of antimony trioxide solution)
Antimony trioxide (manufactured by Sigma-Aldrich Japan LLC) is placed in a flask together with ethylene glycol.
After dissolving by stirring at 150°C for 4 hours, the mixture was cooled to room temperature to prepare a 20 g/l antimony trioxide ethylene glycol solution.

(Polymerization of polyester resin E-1 for base material)
In a 2-liter stainless steel autoclave equipped with a stirrer, high-purity terephthalic acid and twice its molar volume of ethylene glycol were charged. Triethylamine was added at a concentration of 0.3 mol% 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%. To this BHET mixture, a polycondensation catalyst was used:
Using the antimony trioxide solution described above, it was added to the polyester in such a way that it amounted to 0.04 mol% of antimony atoms relative to the acid component. The mixture was then stirred at 250°C for 10 minutes under atmospheric pressure and a nitrogen atmosphere. Subsequently, the temperature was raised to 280°C over 60 minutes while gradually lowering the pressure of the reaction system to 13.3 Pa (0.1 Torr). A polycondensation reaction was then carried out at 280°C and 13.3 Pa for 68 minutes to obtain polyester resin E-1 with an intrinsic viscosity (IV) (solvent: phenol/tetrachloroethane = 60/40) of 0.61 dl/, which was substantially particle-free.

(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.

(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.

(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.

(Polymerization of polyester resin E-2 for base material)
Polymerization was carried out in the same manner as for polyester resin E-1, except that instead of the antimony trioxide solution as the polycondensation catalyst, a mixture of the aforementioned aluminum compound solution and phosphorus compound solution was used, and added to the polyester so that the aluminum atoms and phosphorus atoms amounted to 0.014 mol% and 0.028 mol%, respectively, relative to the acid component in the polyester. However, by setting the polymerization time to 68 minutes, polyester resin E-2 was obtained with an intrinsic viscosity (IV) of 0.61 dl/ and substantially free of particles.

(Example 1)
(1) Preparation of coating solution A coating solution for forming an easily adhesive layer was prepared by mixing the following coating agents with a mixed solvent of water and isopropanol (80/20 parts by mass ratio) so that the solid content mass ratio of the polyurethane resin (A-1) solution to the crosslinking agent (B-1) solution was 70/30.

Mixed solvent (water/isopropanol) 78.26 parts by mass Polyurethane resin (A-1) solution 14.00 parts by mass Crosslinking agent (B-1) solution 5.25 parts by mass Particle I 0.12 parts by mass (Silica sol with average particle size of 100 nm, solid content concentration 40% by mass)
Particle II: 1.87 parts by mass (silica sol with an average particle size of 40-50 nm, solid content concentration of 30% by mass)
Surfactant 0.50 parts by mass (silicone-based, solid content concentration 10% by mass)

(2) Manufacturing of Laminated Polyester Film As the film raw material polymer, 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, and rapidly cooled and solidified on a rotating cooling metal roll maintained at a surface temperature of 20°C to obtain an unstretched PET sheet.

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.

Next, the coating solution was applied to one side of the PET film so that the final coating amount after drying (after biaxial stretching) was 0.13 g/ ^m² . After the coating solution dried, the film was stretched 4.0 times in the width direction 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 having a 100 μm easy-adhesion layer.

3. Manufacturing of Antistatic Polyester Film The following coating liquid (AS-1) was applied to the easily adhering layer of the obtained laminated polyester film so that the coating amount after drying was 0.08 g/m2. After application, it was heated with hot air at 140°C for 20 seconds to dry and cure, and a laminated polyester film with an antistatic layer (antistatic polyester film) was obtained. Various physical properties and evaluation results are shown in Tables 1 and 2.
In the table, the abbreviation "AS" stands for antistatic.
(AS-1)
Water 38.9 parts by mass, Isopropyl alcohol 38.9 parts by mass, N-methyl-2-pyrrolidone 3.0 parts by mass, Acrylic resin (D-1) 1.7 parts by mass, Melamine crosslinking agent 0.3 parts by mass (MX-035, manufactured by Sanwa Chemical Co., Ltd., solid content concentration 70% by mass)
PEDOT/PSS solution 16.7 parts by mass (ICP1010 manufactured by Agfa Material Japan, solid content concentration 1.2% by mass)
Surfactant 0.5 parts by mass (silicone-based, solid content concentration 10% by mass)

(Example 2)
An antistatic polyester film was obtained in the same manner as in Example 1, except that the polyurethane resin was (A-2) and the ratio of the polyurethane resin to the crosslinking agent was changed to 60/40 (by mass).

(Example 3)
An antistatic polyester film was obtained in the same manner as in Example 1, except that the polyurethane resin was (A-3) and the ratio of the polyurethane resin to the crosslinking agent was changed to 50/50 (by mass).

(Example 4)
An antistatic polyester film was obtained in the same manner as in Example 1, except that the crosslinking agent was (B-2) and the ratio of polyurethane resin to crosslinking agent was changed to 60/40 (mass ratio).

(Example 5)
An antistatic polyester film was obtained in the same manner as in Example 1, except that the crosslinking agent was (B-3) and the ratio of polyurethane resin to crosslinking agent was changed to 60/40 (mass ratio).

(Example 6)
An antistatic polyester film was obtained in the same manner as in Example 1, except that a crosslinking agent (B-4) was used in combination with polyurethane resin (A-1) and crosslinking agent (B-1), and the ratio was changed to (A-1)/(B-1)/(B-4) = 55/35/10 (mass ratio).

(Example 7)
An antistatic polyester film was obtained in the same manner as in Example 1, except that polyester resin (C-1) was used in combination with polyurethane resin (A-1) and crosslinking agent (B-1), and the ratio was changed to (A-1)/(B-1)/(C-1) = 36/24/40 (mass ratio).

(Example 8)
An antistatic polyester film was obtained in the same manner as in Example 1, except that polyester resin (C-1) was used in combination with polyurethane resin (A-1) and crosslinking agent (B-1), and the ratio was changed to (A-1)/(B-1)/(C-1) = 24/16/60 (mass ratio).

(Example 9)
An antistatic polyester film was obtained in the same manner as in Example 1, except that resin pellets of polyester resin E-2 were used as the film raw material polymer.

(Example 10)
An antistatic polyester film was obtained in the same manner as in Example 1, except that the coating liquid for the antistatic layer was changed to AS-2.
(AS-2)
Water 38.3 parts by mass, Isopropyl alcohol 38.3 parts by mass, N-methyl-2-pyrrolidone 3.0 parts by mass, Acrylic resin (D-2) 3.0 parts by mass, Melamine crosslinking agent 0.3 parts by mass (MX-035, manufactured by Sanwa Chemical Co., Ltd., solid content concentration 70% by mass)
PEDOT/PSS solution 16.7 parts by mass (ICP1010 manufactured by Agfa Material Japan, solid content concentration 1.2% by mass)
Surfactant 0.5 parts by mass (silicone-based, solid content concentration 10% by mass)

(Example 11)
An antistatic polyester film was obtained in the same manner as in Example 1, except that the coating liquid for the antistatic layer was changed to AS-3.
(AS-3)
Water 38.3 parts by mass, Isopropyl alcohol 38.3 parts by mass, N-methyl-2-pyrrolidone 3.0 parts by mass, Melamine crosslinking agent 1.2 parts by mass (MX-035, manufactured by Sanwa Chemical Co., Ltd., solid content concentration 70% by mass)
PEDOT/PSS solution 16.7 parts by mass (ICP1010 manufactured by Agfa Material Japan, solid content concentration 1.2% by mass)
Surfactant 0.5 parts by mass (silicone-based, solid content concentration 10% by mass)

(Example 12)
An antistatic polyester film was obtained in the same manner as in Example 1, except that the coating liquid for the antistatic layer was changed to AS-4.
(AS-4)
Water 38.3 parts by mass, Isopropyl alcohol 38.3 parts by mass, N-methyl-2-pyrrolidone 3.0 parts by mass, Melamine crosslinking agent 0.9 parts by mass (MX-035, manufactured by Sanwa Chemical Co., Ltd., solid content concentration 70% by mass)
PEDOT/PSS solution 33.3 parts by mass (ICP1010 manufactured by Agfa Material Japan, solid content concentration 1.2% by mass)
Surfactant 0.5 parts by mass (silicone-based, solid content concentration 10% by mass)

(Comparative Example 1)
An antistatic polyester film was obtained in the same manner as in Example 1, except that only polyurethane resin (A-1) was used and the crosslinking agent (B-1) was not used.

(Comparative Example 2)
An antistatic polyester film was obtained in the same manner as in Example 1, except that only the crosslinking agent (B-1) was used and the polyurethane resin (A-1) was not used.

(Comparative Example 3)
An antistatic polyester film was obtained in the same manner as in Example 1, except that the polyurethane resin was changed to (A-4).

(Comparative Example 4)
An antistatic polyester film was obtained in the same manner as in Example 1, except that the polyurethane resin was (A-5) and the ratio of the polyurethane resin to the crosslinking agent was changed to 60/40 (by mass).

(Comparative Example 5)
An antistatic polyester film was obtained in the same manner as in Example 1, except that the polyurethane resin was (A-6) and the ratio of polyurethane resin to crosslinking agent was changed to 50/50 (mass ratio).

(Comparative Example 6)
An antistatic polyester film was obtained in the same manner as in Example 1, except that the polyurethane resin was changed to (A-7) and the crosslinking agent to (B-5).

(Comparative Example 7)
An antistatic polyester film was obtained in the same manner as in Example 1, except that the crosslinking agent was (B-5) and the ratio of polyurethane resin to crosslinking agent was changed to 75/25 (mass ratio).

(Comparative Example 8)
An antistatic polyester film was obtained in the same manner as in Example 1, except that the crosslinking agent was changed to (B-6).

(Comparative Example 9)
An antistatic polyester film was obtained in the same manner as in Example 1, except that the polyurethane resin (A-1) was replaced with a polyester resin (C-2).

(Comparative Example 10)
An antistatic polyester film was obtained in the same manner as in Example 1, except that the polyurethane resin (A-1) was replaced with an acrylic resin (D-1).

Tables 1 and 2 summarize the various physical properties and evaluation results for each example and comparative example.

As shown in Table 2, satisfactory results were obtained in each example regarding haze resistance, blocking resistance, adhesion to the antistatic layer, and moisture and heat resistance. On the other hand, Comparative Examples 1 to 10 did not meet the requirements for at least one of the above evaluation items.

The antistatic polyester film of the present invention has an easy-adhesion layer and an antistatic layer in this order. In particular, by having the easy-adhesion layer according to the present invention, it is possible to provide an antistatic polyester film that has excellent blocking resistance, and excellent initial adhesion and moisture-heat-resistant adhesion between the antistatic layer, the easy-adhesion layer and the polyester film substrate.

On the other hand, Comparative Example 1, lacking the crosslinking agent of the present invention, showed significantly inferior moisture- and heat-resistant adhesion. Comparative Example 2, lacking the polyurethane resin of the present invention, showed significantly inferior moisture- and heat-resistant adhesion. Comparative Example 3, having an acid value outside the range of the present invention for the polyurethane resin, showed significantly inferior moisture- and heat-resistant adhesion. Comparative Example 4, having an acid value outside the range of the present invention for the polyurethane resin, showed poor moisture- and heat-resistant adhesion. Comparative Example 5, having a polyurethane resin with virtually no acid value, showed significantly inferior blocking resistance and moisture- and heat-resistant adhesion. Comparative Example 6, with both the polyurethane resin and the crosslinking agent, had acid values outside the range of the present invention, resulting in significantly inferior moisture- and heat-resistant adhesion. Comparative Example 7, with the acid value of the crosslinking agent, had an acid value outside the range of the present invention, resulting in significantly inferior moisture- and heat-resistant adhesion. Comparative Example 8, with the acid value of the crosslinking agent, had an acid value outside the range of the present invention, resulting in poor moisture- and heat-resistant adhesion. Comparative Examples 9 and 10 are examples in which a polyester resin (Comparative Example 9) or an acrylic resin (Comparative Example 10) was used instead of the polyurethane resin of the present invention. The acid value of the polyester resin or acrylic resin used was equivalent to the acid value range of the polyurethane resin according to the present invention. However, these resins showed significantly inferior moisture resistance and heat adhesion.

According to the present invention, it is possible to provide an antistatic polyester film that can be suitably used in a wide range of fields, including optical applications, packaging applications, and label applications.

Claims (6)

An antistatic polyester film is formed by laminating an easy-adhesion layer and an antistatic layer in this order on at least one side of a polyester film, wherein the easy-adhesion layer is a layer formed by curing a composition containing a polyurethane resin having a carboxyl group and an acid value of 30 to 50 mgKOH/g and a crosslinking agent having a carboxyl group and an acid value of 30 to 50 mgKOH/g.
The antistatic layer comprises an acrylic resin and an antistatic agent.
The antistatic agent is an antistatic polyester film comprising polyalkylenedioxythiophene and a doping agent having sulfonic acid as constituent units . The antistatic polyester film according to claim 1 , wherein the composition forming an easily adhering layer is an isocyanate compound, in which case the crosslinking agent is an isocyanate compound. The antistatic polyester film according to claim 1 or 2, characterized in that its surface resistivity is ^10¹⁰ Ω/□ or less. The antistatic polyester film according to any one of claims 1 to 3, characterized in that the antistatic layer contains melamine as a crosslinking agent , and the antistatic agent is PEDOT/PSS . An antistatic polyester film according to any one of claims 1 to 4, characterized in that the film haze is 3.0% or less. An adhesive film comprising an antistatic polyester film according to any one of claims 1 to 5, with an adhesive layer laminated on at least one side.