Laminated polyester film

Abstract

To provide a laminated polyester film which has good anti-static property regardless of use environment, thereby can suppress defects by deposition or entrainment of a foreign matter, and can maintain good anti-static property even if any damage (external force) is applied to the surface of a curable resin layer.SOLUTION: A laminated polyester film includes a curable resin layer on at least one surface of a polyester film, wherein the curable resin layer is a cured product of a resin composition containing the following compounds (a), (b), (c) and (d): (a) at least one selected from the group consisting of (a1) a polymer obtained by doping a compound composed of a thiophene or thiophene derivative with another anionic compound, and (a2) a self-doped polymer composed of a thiophene or thiophene derivative and having an anionic group therein, (b) a (meth)acrylic polymer having a styrene structure, (c) at least one compound selected from the group consisting of (c1) polyglycerol and (c2) an alkylene oxide adduct of polyglycerol, or its derivative, and (d) a release agent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a laminated polyester film. [Background technology]

[0002] Polyester films have traditionally been used in a variety of applications because they possess excellent properties such as mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, and optical properties, as well as being cost-effective.

[0003] A common problem with plastic films is that polyester films are prone to static electricity buildup, which can cause problems in processing due to the adhesion or entrapment of foreign matter.

[0004] Therefore, various antistatic measures are taken. Generally, one method is to provide a functional layer with antistatic properties on the surface. As antistatic agents coated on polyester films, cationic compounds containing cationic groups such as quaternary ammonium groups, and anionic compounds containing anionic groups such as sulfonate groups and phosphonate groups are mainly used. However, these have the disadvantage that their antistatic ability is easily affected by ambient humidity and moisture due to their ionic conductivity, and their conductivity decreases, especially under low humidity, making it impossible to obtain the desired antistatic performance. This tendency is often more pronounced in anionic antistatic agents.

[0005] Furthermore, in recent years, due to growing concern about environmental issues and the potential impact on other components incorporated into the film, there is a growing demand for the absence of halogens in polyester films. However, in the case of cationic antistatic agents, compounds in which the counter-anion of the quaternary ammonium group is a chloride ion are common. While there are also antistatic agents that use monoalkyl sulfate ions, alkyl sulfonate ions, etc. as counter-anions, the ion mobility is lower, resulting in inferior antistatic performance.

[0006] Electronically conductive compounds can exhibit superior antistatic properties compared to the ionic conductive compounds mentioned above, and are less affected by humidity. Various conductive organic polymer compounds have been proposed as electronically conductive compounds, among which conductive polymer compounds such as polyacetylene, polyphenylene, polyaniline, polypyrrole, polyisothianaphthene, and polythiophene have been proposed. Polythiophene compounds have excellent conductivity and can exhibit high antistatic properties and transparency when applied to films (Patent Documents 1 and 2). However, the antistatic agent of electronically conductive compounds changes structure when exposed to air, so depending on the usage environment, the antistatic properties may decrease compared to immediately after manufacture (Patent Document 3). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2003-154594 [Patent Document 2] Japanese Patent Application Publication No. 9-131843 [Patent Document 3] Japanese Patent Publication No. 2020-29485 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The present invention has been made in view of the above circumstances, and its problem to be solved is to provide a laminated polyester film that has good antistatic properties regardless of the usage environment, thereby suppressing problems caused by the adhesion or entrapment of foreign matter, and that can maintain good antistatic properties even when some kind of damage (external force) is applied to the surface of the cured resin layer. [Means for solving the problem]

[0009] As a result of intensive studies on the above problems, the present inventor has found that the above problems can be solved by using a laminated polyester film having a specific structure, and has completed the present invention. That is, the present invention provides the following [1] to

[18] .

[0010] [1] A laminated polyester film having a cured resin layer on at least one surface of the polyester film, wherein the cured resin layer is a cured product of a resin composition containing the following compounds (a), (b), (c) and (d). (a) At least one selected from the group consisting of (a1) a polymer doped with another anion compound in a compound composed of thiophene or a thiophene derivative, and (a2) a polymer having an anion group in a compound composed of thiophene or a thiophene derivative and self-doped (b) A (meth)acrylic polymer having a styrene structure (c) At least one compound selected from the group consisting of (c1) polyglycerin and (c2) an alkylene oxide adduct to polyglycerin or a derivative thereof (d) A release agent [2] The laminated polyester film according to [1] above, wherein the acrylic structure of the (meth)acrylic polymer is a (meth)acrylic acid structure. [3] The laminated polyester film according to [1] or [2] above, wherein the (d) release agent is wax. [4] The surface resistivity of the cured resin layer after rubbing treatment is 1×10 8 (Ω / □) or less, and the laminated polyester film according to any one of [1] to [3] above. [5] The laminated polyester film according to any one of [1] to [4] above, wherein the resin composition contains at least one selected from the group consisting of a melamine compound, an epoxy compound, an isocyanate compound and a carbodiimide compound as a crosslinking agent. [6] The laminated polyester film according to any one of [1] to [5] above, wherein the cured resin layer is provided by in-line coating (coating and stretching method). [7] The arithmetic mean height (Sa) of the surface on the opposite side of the surface where the cured resin layer is provided is 15 nm or less, and the maximum peak height (Sp) is 350 nm or less. The laminated polyester film according to any one of [1] to [6] above. [8] The laminated polyester film according to any one of [1] to [7] above, wherein the polyester film has a multilayer structure including at least three layers. [9] The birefringence (Δn × 10 3 ) of the polyester film is 50 or more. The laminated polyester film according to any one of [1] to [8] above.

[10] The laminated polyester film according to any one of [1] to [9] above, wherein the master roll width of the laminated polyester film is 6000 mm or more.

[11] The laminated polyester film according to

[10] above, wherein the slit roll width of the laminated polyester film is 1500 mm or more.

[12] A laminated polyester film with a functional layer provided on the cured resin layer or on the opposite side of the cured resin layer of the laminated polyester film according to any one of [1] to

[11] above.

[13] The laminated polyester film with a functional layer according to

[12] above, wherein the functional layer is an adhesive layer.

[14] The laminated polyester film with a functional layer according to

[13] above, wherein the adhesive layer is a silicone-based adhesive layer.

[15] The laminated polyester film with a functional layer according to

[13] above, wherein the adhesive layer is an acrylic-based adhesive layer or a urethane-based adhesive layer.

[16] The laminated polyester film with a functional layer according to

[12] above, wherein the functional layer is a release layer.

[17] A film laminate in which an optical member is bonded to the surface of the adhesive layer of the laminated polyester film with a functional layer according to any one of

[12] to

[16] above.

[18] A film laminate in which a release film is bonded to the surface of the adhesive layer of the laminated polyester film with a functional layer according to any one of

[12] to

[16] above. [Effect of the Invention]

[0011] According to the present invention, regardless of the usage environment (e.g., exposure to the atmosphere), even if some damage (external force) is applied to the surface of the cured resin layer, a laminated polyester film can be provided in which defects due to the adhesion or entrapment of foreign matter due to static electricity are suppressed, and its industrial value is high. [Modes for carrying out the invention]

[0012] Hereinafter, an example of an embodiment of the present invention will be described in detail. However, the present invention is not limited to the embodiments described below, and can be modified and implemented as such without departing from the spirit of the invention.

[0013] The laminated polyester film of the present invention has a cured resin layer containing a specific component on at least one surface of the polyester film.

[0014] <Polyester film> The polyester film may have a single-layer structure or a multi-layer structure. If the polyester film has a multi-layer structure, it may have a two-layer structure, a three-layer structure, or more, and may have a four-layer or more multi-layer structure as long as it does not exceed the essence of the present invention; it is not particularly limited. In the present invention, it is preferable that the polyester film consists of at least three layers. The polyester film may be an unoriented film (sheet) or an oriented film (sheet). In particular, an oriented film stretched in one or two axes is preferred, and a biaxially oriented polyester film is more preferred in terms of thinness and dimensional stability.

[0015] In the present invention, the polyester used as the raw material for the polyester film is not particularly limited and may be a homopolyester or a copolymerized polyester. When it is a homopolyester, examples include polyesters obtained by polycondensation of a dicarboxylic acid and a diol, where aromatic dicarboxylic acid is preferred as the dicarboxylic acid and aliphatic glycol is preferred as the diol.

[0016] The polyester film is preferably composed mainly of polyester. Furthermore, if the polyester film has a multilayer structure, it is preferable that the main resin component of each layer is polyester. The term "main component resin" refers to the resin that makes up the largest proportion of each layer. For example, it refers to the resin that accounts for 50% or more by mass, especially 70% or more by mass, and among those, 80% or more by mass (including 100% by mass) of the resins that make up each layer.

[0017] Examples of the above-mentioned aromatic dicarboxylic acids include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, and phthalic acid. Examples of the above-mentioned aliphatic glycols include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, and 1,4-cyclohexanedimethanol. Typical polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalate, polybutylene terephthalate, and polybutylene-2,6-naphthalate. Among these, polyethylene terephthalate (PET) is preferred.

[0018] Examples of copolymerized polyesters include copolymerized polyesters that contain a third component as a copolymerizing component, other than the main component compounds of dicarboxylic acids, preferably aromatic dicarboxylic acids, and diols, preferably a compound that is the main component of aliphatic glycols. For example, as dicarboxylic acids, in addition to the above-mentioned aromatic dicarboxylic acids, aliphatic dicarboxylic acids such as adipic acid and sebacic acid can be mentioned, and as diols, in addition to the above-mentioned aliphatic glycols, neopentyl glycol can be mentioned. For example, in polyethylene terephthalate, the third component is a component other than terephthalic acid and ethylene glycol. Specifically, polyethylene terephthalate may contain approximately 30 mol% or less of dicarboxylic acid units other than terephthalic acid out of 100 mol% of dicarboxylic acid units, and may also contain approximately 30 mol% or less of diol units other than ethylene glycol out of 100 mol% of diol units.

[0019] The intrinsic viscosity of the polyester is not particularly limited, but from the viewpoint of film-forming properties and productivity, it is preferably 0.45 to 1.0 dL / g, and more preferably 0.5 to 0.9 dL / g.

[0020] There are no particular restrictions on the polymerization catalyst for polyester, and conventionally known compounds can be used. For example, antimony compounds, titanium compounds, germanium compounds, manganese compounds, aluminum compounds, magnesium compounds, calcium compounds, etc., can be used as polymerization catalysts. In particular, titanium compounds and germanium compounds are preferred because they exhibit high catalytic activity, allowing polymerization to occur in small amounts, resulting in a low amount of catalyst-derived metal remaining in the film and thus increasing the film's brightness. Furthermore, since germanium compounds are expensive, the use of titanium compounds is even more preferable.

[0021] In the case of polyester using a titanium compound as a polymerization catalyst, the titanium element content in the polyester is preferably in the range of 50 ppm or less, more preferably 1 to 20 ppm, and even more preferably 2 to 10 ppm. If the titanium compound content is 50 ppm or less, the degradation of the polyester in the melt extrusion process can be suppressed, and a film with reduced yellowing can be obtained. If the titanium compound content is above the above lower limit, the polymerization efficiency is sufficient, and a cost-effective film with sufficient strength can be obtained.

[0022] When using a titanium compound as a polymerization catalyst, it is preferable to use a phosphorus compound to reduce the activity of the titanium compound in order to suppress resin degradation during the melt extrusion process. As the phosphorus compound, orthophosphoric acid is preferred considering the productivity and thermal stability of polyester. The phosphorus element content is preferably in the range of 1 to 300 ppm by mass, more preferably 3 to 200 ppm by mass, and even more preferably 5 to 100 ppm by mass, based on 100% by mass of the polyester to be melt-extruded. If the phosphorus compound content is below the above upper limit, it will not cause gelation or foreign matter. If it is above the above lower limit, the activity of the titanium compound can be sufficiently reduced, discoloration can be suppressed, and the resulting film will not be yellowish.

[0023] To suppress the precipitation of oligomer components, the film may be manufactured using polyester with a low oligomer content as the raw material. Various known methods can be used to manufacture polyester with a low oligomer content, such as a method of solid-phase polymerization after polyester production.

[0024] The polyester film may be constructed with three or more layers, and the outermost layer of the polyester film may be made of a polyester raw material with a low oligomer content to suppress the amount of oligomer component precipitation. Alternatively, the polyester may be obtained by esterification or transesterification, followed by further increasing the reaction temperature and melt polycondensation under reduced pressure.

[0025] It is also possible to include ultraviolet absorbers in the polyester film to improve the weather resistance of the film and prevent deterioration of the adherend (e.g., liquid crystal polarizing film). The ultraviolet absorber is a compound that absorbs ultraviolet light and is not particularly limited as long as it can withstand the heat added during the manufacturing process of the polyester film.

[0026] UV absorbers include organic and inorganic UV absorbers, but organic UV absorbers are preferred from the viewpoint of transparency. Organic UV absorbers are not particularly limited, but examples include cyclic iminoesters, benzotriazoles, and benzophenones. From the viewpoint of durability, cyclic iminoesters and benzotriazoles are more preferred. UV absorbers may be used individually or in combination of two or more types.

[0027] Particles can be incorporated into the polyester film primarily for the purpose of providing slipperiness and preventing scratches during each process. The type of particles to be incorporated is not particularly limited as long as they can provide slipperiness. Examples include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, zirconium oxide, and titanium dioxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenolic resin, epoxy resin, and benzoguanamine resin. Furthermore, during the polyester manufacturing process, precipitated particles obtained by precipitating and finely dispersing a portion of metal compounds such as catalysts can also be used. Among these, silica particles and calcium carbonate particles are preferred because they are particularly effective even in small amounts.

[0028] There are no particular restrictions on the shape of the particles used; spherical, lumpy, rod-shaped, flattened, etc., may be used. Furthermore, there are no particular restrictions on their hardness, specific gravity, color, etc. These particles may be used individually or in combination of two or more types as needed.

[0029] The average particle size of the particles used is not particularly limited, but is preferably 5 μm or less, and more preferably in the range of 0.01 to 3 μm. When the average particle size is 5 μm or less, the surface roughness of the film does not become too rough, and problems do not occur in various subsequent processing steps. Also, by using the above range, haze is kept low, and it is easier to ensure transparency of the film as a whole. If the average particle size is 0.01 μm or more, effects such as providing slipperiness and preventing scratch formation can be ensured. For determining the average particle size, the particle size at which the cumulative volume fraction reaches 50% (d50) in the equivalent spherical distribution measured using a centrifugal sedimentation particle size distribution analyzer (SA-CP3 type, manufactured by Shimadzu Corporation) can be used as the average particle size.

[0030] The particle content in the layer containing the above-mentioned particles is preferably less than 5% by mass, more preferably in the range of 0.0003 to 1% by mass, and even more preferably in the range of 0.0005 to 0.5% by mass. If no particles are present, or if the particle content is low, the transparency of the film increases, resulting in a good film. On the other hand, by including particles within the above range, a polyester film with sufficient slipperiness is obtained. If the particle content is less than 5% by mass, the film's haze does not increase, and sufficient transparency is obtained. Therefore, for example, the difficulty of inspecting for defects such as foreign matter during various inspections does not increase. When incorporating particles into a polyester film, if the polyester film has a multilayer structure, for example, if the polyester film has a surface layer and an intermediate layer, it is preferable to incorporate the particles into the surface layer. In this case, it is even more preferable to have a multilayer structure having a particle-containing surface layer, an intermediate layer, and a particle-containing surface layer in that order. By incorporating particles into the surface layer, it is possible to effectively impart properties such as slipperiness while reducing the overall particle content of the polyester film.

[0031] The method for adding particles to the polyester film is not particularly limited, and conventionally known methods can be employed. For example, if the polyester film has a multilayer structure, the particles can be added at any stage in the production of the polyester constituting each layer, but it is preferable to add them after the esterification or transesterification reaction is completed.

[0032] In addition to the particles mentioned above, conventionally known ultraviolet absorbers, antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, etc., may be added to the polyester film of the present invention as needed.

[0033] The thickness of the polyester film in this invention is not particularly limited as long as it is within the range in which a film can be formed, but is usually in the range of 10 to 300 μm, preferably 15 to 250 μm, more preferably 20 to 200 μm, and even more preferably 25 to 125 μm. If the polyester film has a multilayer structure, the overall thickness of the polyester film is assumed to be within the above range.

[0034] Next, we will specifically describe examples of polyester film manufacturing, but the examples are not limited to those listed below. For example, when manufacturing a biaxially oriented polyester film, it is preferable to extrude the aforementioned polyester raw material from a die as a molten sheet using an extruder, and then cool and solidify the molten sheet with a rotating cooling roll to obtain an unstretched sheet. In this case, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotating cooling drum, and electrostatic application adhesion or liquid coating adhesion is preferably employed. In this way, an unstretched sheet is obtained. If the polyester film has a multilayer structure, for example, multiple extruders can be used as the extruder to extrude the molten sheet from the die, and an unstretched sheet can be obtained as described above.

[0035] Next, the obtained unstretched sheet is stretched in two axial directions. First, the unstretched sheet is stretched in one direction using a roll or tenter type stretcher. The stretching temperature is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.5 to 7 times, preferably 3 to 6 times. Next, the material is stretched in a direction perpendicular to the first stretching direction, usually at 70 to 170°C, at a stretching ratio of usually 2.5 to 7 times, preferably 3 to 6 times. Subsequently, a biaxially oriented film can be obtained by heat treatment at a temperature of typically 180-270°C, under tension or under relaxation of 30% or less. In the above stretching, a method of performing unidirectional stretching in two or more stages can also be employed. In that case, it is preferable to perform the stretching so that the final stretching ratios in both directions are within the above ranges.

[0036] Furthermore, in the present invention, a simultaneous biaxial stretching method can also be used for the production of polyester film. The simultaneous biaxial stretching method is a method of simultaneously stretching and oriented the aforementioned unstretched sheet in the longitudinal direction (machine direction) and the width direction while maintaining a temperature control of typically 70 to 120°C, preferably 80 to 110°C. The stretching ratio is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area. Next, a heat treatment is performed at a temperature of typically 180-270°C under tension or relaxation of 30% or less to obtain a stretched and oriented film. Regarding the simultaneous biaxial stretching apparatus employing the above-described stretching method, conventionally known stretching methods such as screw type, pantograph type, and linear drive type can be used. The longitudinal direction (machine direction) of the film refers to the direction in which the film progresses during the film manufacturing process, i.e., the winding direction of the film roll. The width direction refers to the direction parallel to the film surface and perpendicular to the longitudinal direction, that is, the direction parallel to the central axis of the roll when the film is in a roll form.

[0037] <Cured resin layer> Next, the cured resin layer constituting the laminated polyester film in the present invention will be described.

[0038] The cured resin layer constituting the laminated polyester film must be a cured product of a resin composition containing the following compounds (a), (b), (c), and (d). (a) At least one selected from the group consisting of (a1) a polymer obtained by doping a compound comprising thiophene or a thiophene derivative with another anionic compound, and (a2) a polymer obtained by self-doping a compound comprising thiophene or a thiophene derivative having an anionic group. (b) (meth)acrylic polymer having a styrene structure (c)(c1) At least one compound or derivative thereof selected from the group consisting of polyglycerin and (c2) alkylene oxide adducts to polyglycerin. (d) Release agent

[0039] Compound (a) is at least one selected from the group consisting of (a1) a polymer obtained by doping a compound comprising thiophene or a thiophene derivative with another anionic compound, and (a2) a polymer obtained by self-doping a compound comprising thiophene or a thiophene derivative having an anionic group. These substances are preferred because they exhibit excellent conductivity. Examples of compound (a) include those obtained by polymerizing a compound of formula (1) or formula (2) below in the presence of a polyanion. Furthermore, polymers (a1) and (a2) may be used in combination.

[0040] [ka]

[0041] In the above equation (1), R 1 and R 2 Each of these independently represents a hydrogen atom or an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group having 1 to 20 carbon atoms.

[0042] [ka]

[0043] In equation (2) above, n represents an integer from 1 to 4.

[0044] Examples of polyanions used during polymerization include poly(meth)acrylic acid, polymaleic acid, polystyrene sulfonic acid, and polyvinyl sulfonic acid. A method for producing such polymers can be employed, for example, the method described in Japanese Patent Publication No. 7-90060.

[0045] In the present invention, a compound of formula (2) in which n is 2 and polystyrene sulfonic acid is used as the polyanion is preferably used.

[0046] If these polyanions are acidic, some or all of them may be neutralized. Ammonia, organic amines, and alkali metal hydroxides are preferred bases for neutralization.

[0047] Compound (b) is a (meth)acrylic polymer having a styrene structure.

[0048] A styrene structure is a structure introduced by styrene and styrene derivatives. The styrene may also have substituents such as alkyl groups (methyl or ethyl) or phenyl groups. From the viewpoint of preventing oligomer precipitation due to heat treatment, preferably styrene substituted with an alkyl group having 4 or fewer carbon atoms, or unsubstituted styrene, and more preferably unsubstituted styrene.

[0049] (Meth)acrylic polymers are polymers whose constituent units are (meth)acrylic acid or alkyl (meth)acrylate. In other words, compound (b) is a copolymer of styrene or a styrene derivative and (meth)acrylic acid or an alkyl (meth)acrylate ester.

[0050] In this invention, the term "(meth)acrylic acid" refers to either or both "acrylic acid" and "methacrylic acid." Similarly, "(meth)acrylate" refers to either or both "acrylate" and "methacrylate," and "(meth)acryloyl" refers to either or both "acryloyl" and "methacryloyl."

[0051] Examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate. The alkyl (meth)acrylate may also be an alkyl (meth)acrylate containing a hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. These may be used individually or in combination of two or more. In particular, from the viewpoint of preventing oligomer precipitation due to heat treatment, polymers with (meth)acrylic acid as a constituent unit are preferred, and polymers with acrylic acid as a constituent unit are preferred. That is, the acrylic structure of the (meth)acrylic polymer is preferably a structure derived from (meth)acrylic acid. The (meth)acrylic polymer may have a double bond that is capable of radical polymerization.

[0052] (Meth)acrylic polymers having a styrene structure can also be combined with other polymerizable monomers copolymerizable with the above-mentioned components. Examples of copolymerizable monomers include hydroxyl group-containing dibasic acid ester compounds such as monobutyl hydroxyfumarate and monobutyl hydroxyitaconate; various nitrogen-containing compounds such as (meth)acrylamide, diacetone acrylamide, N-methylolacrylamide, or (meth)acrylonitrile; various vinyl esters such as vinyl propionate and vinyl acetate; various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane; phosphorus-containing vinyl monomers; various vinyl halides such as vinyl chloride and pyridene chloride; and various conjugated dienes such as butadiene.

[0053] The proportion of (meth)acrylic acid or alkyl (meth)acrylate in a (meth)acrylic polymer having a styrene structure is, for example, 3 mol% or more, preferably 5 to 40 mol%, more preferably 10 to 30 mol%, and even more preferably 15 to 25 mol%, based on the total amount of monomers constituting the (meth)acrylic polymer having a styrene structure. When the proportion of (meth)acrylic acid or alkyl (meth)acrylate is 3 mol% or more, an effect of preventing oligomer precipitation due to heat treatment is exhibited. Furthermore, when it is below the above upper limit, the proportion of styrene structure increases, and the durability of the antistatic performance can be ensured.

[0054] The proportion of styrene and styrene derivatives in a (meth)acrylic polymer having a styrene structure is, for example, 50 to 97 mol%, preferably 60 to 95 mol%, more preferably 70 to 90 mol%, and even more preferably 75 to 85 mol%, based on the total amount of monomers constituting the (meth)acrylic polymer having a styrene structure. If the proportion of styrene and styrene derivatives is above the lower limit, the durability of the antistatic performance is ensured, and if it is below the upper limit, the effect of preventing oligomer precipitation due to heat treatment is ensured.

[0055] The mechanism by which the precipitation of oligomeric components contained in the polyester film is suppressed is presumed to be as follows. When polyester film is heated above its glass transition temperature, oligomer components precipitate on its surface. However, it is hypothesized that by forming a cured resin layer on the polyester film using a resin composition containing a (meth)acrylic polymer with a styrene structure, the aromatic rings contained in the styrene are stacked parallel to the film, thereby preventing the precipitation of oligomer components.

[0056] Compound (c) is at least one compound or derivative thereof selected from the group consisting of (c1) polyglycerol and (c2) alkylene oxide adducts to polyglycerol. Polyglycerol is a compound represented by the following general formula (3).

[0057] [ka]

[0058] In the above formula, n is 2 or greater. In the present invention, n in the formula is usually in the range of 2 to 20, preferably 3 to 15, and more preferably 3 to 12.

[0059] Alkylene oxide adducts to polyglycerin have a structure in which alkylene oxide is added to the hydroxyl group of polyglycerin represented by general formula (3) through addition polymerization. The structure of the alkylene oxide attached to each hydroxyl group of the polyglycerol skeleton may be the same or different. Furthermore, it is sufficient that at least one hydroxyl group in the molecule has an alkylene oxide or its derivative attached; it is not necessary for all hydroxyl groups to have an alkylene oxide or its derivative attached.

[0060] The preferred alkylene oxides to be added to polyglycerin are ethylene oxide or propylene oxide. If the alkylene chain of the alkylene oxide becomes too long, the hydrophobicity increases, the dispersibility in the coating solution deteriorates, and the antistatic properties and transparency of the cured resin layer tend to worsen. Ethylene oxide is particularly preferred. The number of alkylene oxides added to the polyglycerin is preferably 200 to 2000, more preferably 300 to 1000, and even more preferably 400 to 900, in terms of the number-average molecular weight of the final compound.

[0061] The above-mentioned polyglycerin, or alkylene oxide adduct to polyglycerin, may be used individually or in combination of two or more types.

[0062] In the present invention, the resin composition forming the cured resin layer may contain a crosslinking agent for the purpose of improving the durability of the cured resin layer, particularly the durability of its antistatic properties. Various known crosslinking agents can be used, including, for example, melamine compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, oxazoline compounds, and silane coupling compounds. Among these, at least one selected from the group consisting of melamine compounds, epoxy compounds, isocyanate compounds, and carbodiimide compounds is preferred in terms of suppressing the decrease in antistatic properties after exposure to air, and melamine compounds are more preferred from the viewpoint of further improving the durability of the cured resin layer. These may be used alone or in combination of two or more.

[0063] Melamine compounds are compounds that have a melamine skeleton within them. For example, alkylolated melamine derivatives, compounds partially or completely etherified by reacting alkylolated melamine derivatives with alcohol, and mixtures thereof can be used. Suitable alcohols for etherification include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, and isobutanol. The melamine compound may be a monomer or a polymer of two or more units, or a mixture thereof. Furthermore, a compound in which urea or the like is co-condensed with a portion of the melamine can also be used, and a catalyst can be used to increase the reactivity of the melamine compound.

[0064] In forming the cured resin layer, various conventionally known polymers, such as polyester resins, acrylic resins, and urethane resins, can be used in combination as binders to improve the appearance and transparency of the coating.

[0065] Within the limits that do not impair the spirit of the present invention, the cured resin layer may contain particles for purposes such as improving blocking properties or slipperiness.

[0066] The proportion of compound (a) in the total nonvolatile components of the resin composition forming the cured resin layer is usually 2 to 30% by mass, more preferably 3 to 15% by mass, and even more preferably 5 to 12% by mass. When the proportion of compound (a) is below the upper limit, the strength and transparency of the cured resin layer are good. On the other hand, when the proportion of compound (a) is above the lower limit, sufficient antistatic performance is obtained, and the antistatic performance does not decrease after exposure to air.

[0067] The proportion of compound (b) in the total nonvolatile components of the resin composition of the cured resin layer is typically in the range of 5 to 80% by mass, preferably 10 to 50% by mass, and more preferably 12 to 40% by mass. If the proportion of compound (b) is below the upper limit, the proportion of other components increases, resulting in sufficient antistatic properties and a good coating appearance. On the other hand, if the proportion of compound (b) is above the lower limit, sufficient film-forming properties can be ensured while sufficiently suppressing oligomer precipitation, resulting in a uniform coating.

[0068] The proportion of compound (c) in the total nonvolatile components of the resin composition of the cured resin layer is typically in the range of 10 to 85% by mass, preferably 40 to 70% by mass, and more preferably 45 to 65% by mass. If the proportion of compound (c) is below the upper limit, the proportions of other components increase, resulting in sufficient antistatic properties and film-forming properties. On the other hand, if the proportion of compound (c) is above the lower limit, the transparency of the cured resin layer is good.

[0069] When a crosslinking agent is used in combination with the cured resin layer, the proportion of the crosslinking agent to the total nonvolatile components in the resin composition is usually 30% by mass or less, preferably 1 to 25% by mass, and more preferably 3 to 20% by mass. Using a crosslinking agent within this range provides sufficient antistatic performance, suppresses deterioration of antistatic properties after exposure to air, and improves the strength of the cured resin layer.

[0070] (d) Release agent This composition contains (d) a release agent (hereinafter also referred to as compound (d)). There are no particular restrictions on the release agent, and conventionally known release agents can be used. Examples include waxes, long-chain alkyl group-containing compounds, fluorine compounds, and silicone compounds. Among these, it is preferable that it be at least one of waxes and long-chain alkyl group-containing compounds, and more preferably wax from the viewpoint of achieving both antistatic properties and lubricity. In this composition, (d) the release agent may be used alone or in combination of two or more types.

[0071] In the present invention, the resin composition that forms the cured resin layer exhibits good antistatic properties by containing components (a) to (c) as described above. Furthermore, since this resin composition contains a mold release agent (d), the slippery effect of the mold release agent reduces the load applied to the surface of the cured resin layer when an external force is applied to the surface of the cured resin layer in some form, such as abrasion (for example, contact between the conveyor roll and the cured resin layer during the processing step, abrasion, etc.). The proportion of compound (d) in the total nonvolatile components of the resin composition of the cured resin layer is usually in the range of 10% by mass or less, preferably 8% by mass or less, and more preferably 6% by mass or less. On the other hand, the lower limit is preferably 1% by mass or more.

[0072] (wax) Examples of the above-mentioned waxes include natural waxes, synthetic waxes, and modified waxes. Examples of natural waxes include plant-based waxes, animal-based waxes, mineral waxes, and petroleum waxes. Examples of plant-based waxes include candelilla wax, carnauba wax, rice wax, wood wax, and jojoba oil. Examples of animal-derived waxes include beeswax, lanolin, and whale wax. Examples of mineral-based waxes include montan wax, ozokerite, and ceresin. Examples of petroleum waxes include paraffin wax, microcrystalline wax, and petrolatum.

[0073] Examples of synthetic waxes include synthetic hydrocarbons, modified waxes, hydrogenated waxes, fatty acids, acid amides, amines, imides, ester waxes, and ketones. Other examples of synthetic waxes include Fischer-Tropsch wax (also known as sazole wax) and polyethylene wax. In addition, low molecular weight polymers (specifically polymers with a number average molecular weight of 500 to 20,000) can be mentioned, namely polypropylene, ethylene-acrylic acid copolymers, polyethylene glycol, polypropylene glycol, and block polymers or graft polymers of polyethylene glycol and polypropylene glycol.

[0074] Examples of modified waxes include montan wax derivatives, paraffin wax derivatives, and microcrystalline wax derivatives. Here, a derivative refers to a compound obtained by any of the following treatments: purification, oxidation, esterification, saponification, or a combination thereof. Examples of hydrogenated waxes include hydrogenated castor oil and hydrogenated castor oil derivatives.

[0075] Among these, synthetic wax is preferred as the mold release agent, polyethylene wax is more preferred, and oxidized polyethylene wax is even more preferred. Furthermore, when the resin composition is diluted with a solvent such as water to prepare the coating solution, the wax may be dispersed with a surfactant or the like to form a wax emulsion, which may then be incorporated into the coating solution.

[0076] The number-average molecular weight of synthetic waxes is typically 500 to 30,000, preferably 1,000 to 15,000, and more preferably 2,000 to 8,000, from the viewpoint of handling ease. The number-average molecular weight is a polystyrene-based value measured using gel permeation chromatography (GPC).

[0077] When forming the cured resin layer, considering heating for crosslinking and the like, the melting or softening point of the wax is preferably 80°C or higher, and more preferably 110°C or higher. On the other hand, from the viewpoint of controlling the phase separation performance after heat treatment, the melting or softening point of the wax is preferably 200°C or lower, more preferably 170°C or lower, and even more preferably 150°C or lower. The melting point (softening point) of wax can be measured using a differential scanning calorimetry (DSC).

[0078] (Long-chain alkyl group-containing compounds) A long-chain alkyl group-containing compound is a compound having a linear or branched alkyl group with typically 6 or more carbon atoms, preferably 8 or more, and more preferably 12 or more. Examples of alkyl groups include hexyl, octyl, decyl, lauryl, octadecyl, and behenyl groups, which have approximately 6 to 30 carbon atoms. Examples of compounds containing alkyl groups include various long-chain alkyl group-containing polymer compounds, long-chain alkyl group-containing amine compounds, long-chain alkyl group-containing ether compounds, and long-chain alkyl group-containing quaternary ammonium salts. Considering heat resistance, polymer compounds are preferred, and polymer compounds having long-chain alkyl groups as side chains are more preferred.

[0079] Polymer compounds having long-chain alkyl groups as side chains can be obtained by reacting a polymer having a reactive group with a compound having an alkyl group that can react with the reactive group. Examples of the reactive group include hydroxyl groups, amino groups, carboxyl groups, and acid anhydrides. Examples of compounds having these reactive groups include polyvinyl alcohol, polyethyleneimine, polyethyleneamine, reactive group-containing polyester resins, and reactive group-containing poly(meth)acrylic resins. Among these, polyvinyl alcohol is preferred considering ease of handling. The degree of polymerization of the polyvinyl alcohol used is not particularly limited, but is usually 100 or more, preferably in the range of 300 to 40000. The degree of saponification of the polyvinyl alcohol is also not particularly limited, but is usually 70 mol% or more, preferably in the range of 70 to 99.9 mol%, more preferably 80 to 97 mol%, and even more preferably 86 to 95 mol%.

[0080] Compounds having alkyl groups that can react with the above-mentioned reactive groups include, for example, long-chain alkyl-containing isocyanates such as hexyl isocyanate, octyl isocyanate, decyl isocyanate, lauryl isocyanate, octadecyl isocyanate, and behenyl isocyanate; long-chain alkyl-containing acid chlorides such as hexanoyl chloride, octanoyl chloride, decanoyl chloride, lauroyl chloride, octadecanoyl chloride, and behenoyl chloride; long-chain alkyl-containing amines; and long-chain alkyl-containing alcohols. Among these, long-chain alkyl group-containing isocyanates are preferred, and octadecyl isocyanates are particularly preferred, considering ease of handling.

[0081] Polymeric compounds having long-chain alkyl groups as side chains can also be obtained by polymerization of long-chain alkyl (meth)acrylates or by copolymerization of long-chain alkyl (meth)acrylates with other vinyl group-containing monomers. Examples of long-chain alkyl (meth)acrylates include hexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, octadecyl (meth)acrylate, and behenyl (meth)acrylate.

[0082] (Fluorine compounds) Fluorine compounds are compounds that contain fluorine atoms. Organic fluorine compounds are preferred from the viewpoint of the appearance when applied by in-line coating. Examples include perfluoroalkyl group compounds, polymers of olefin compounds containing fluorine atoms, and aromatic fluorine compounds such as fluorobenzene. From the viewpoint of effectively obtaining the ability to form irregularities through moderate phase separation with a small content, it is preferable that the compound has a perfluoroalkyl group. Furthermore, fluorine compounds that contain long-chain alkyl compounds as described above can also be used.

[0083] Examples of perfluoroalkyl group-containing compounds include perfluoroalkyl group-containing (meth)acrylates and their polymers, such as perfluoroalkyl (meth)acrylate, perfluoroalkyl methyl (meth)acrylate, 2-perfluoroalkyl ethyl (meth)acrylate, 3-perfluoroalkyl propyl (meth)acrylate, 3-perfluoroalkyl-1-methylpropyl (meth)acrylate, and 3-perfluoroalkyl-2-propenyl (meth)acrylate; and perfluoroalkyl group-containing vinyl ethers and their polymers, such as perfluoroalkyl methyl vinyl ether, 2-perfluoroalkyl ethyl vinyl ether, 3-perfluoropropyl vinyl ether, 3-perfluoroalkyl-1-methylpropyl vinyl ether, and 3-perfluoroalkyl-2-propenyl vinyl ether. Polymers are preferable when considering heat resistance. The polymer may be a polymer of a single compound or a polymer of multiple compounds. From the viewpoint of effectively imparting lubricity with a small content, the perfluoroalkyl group preferably has 3 to 11 carbon atoms. Furthermore, it may be a polymer with a compound containing the long-chain alkyl compound mentioned above, and from the viewpoint of adhesion to the polyester film substrate, a polymer with vinyl chloride is also preferably used.

[0084] (Silicone compounds) Silicone compounds are compounds that have a silicone structure within their molecules, and examples include silicone emulsions, acrylic grafted silicones, silicone grafted acrylics, amino-modified silicones, perfluoroalkyl-modified silicones, and alkyl-modified silicones. Considering heat resistance, it is preferable to include a curable silicone resin. Any type of curing reaction can be used for the curing type silicone resin, including addition reaction, condensation reaction, UV curing, and electron beam curing.

[0085] The thickness of the cured resin layer can be determined from the amount of cured resin composition applied to obtain the desired film thickness. In this case, the thickness of the cured resin layer is preferably 0.002 g / m².2 1.0 g / m or less, more preferably 0.005 g / m 2 or more and 0.25 g / m 2 or less, even more preferably 0.02 g / m 2 or more and 0.10 g / m 2 or less, corresponding to the coating amount described above. If the thickness of the cured resin layer is within the above range, precipitation of the oligomer component can be suppressed, and good antistatic properties can be imparted. 2 As another method, the surface of the cured resin layer can be stained with RuO4, embedded in an epoxy resin, and then the section prepared by the ultramicrotomy method can be stained again with RuO4, and the cross section of the resin layer can be measured using TEM (H-7650 manufactured by Hitachi High-Technologies Corporation, acceleration voltage 100 kV). In this case, the thickness of the cured resin layer is preferably 0.002 μm or more and 1.0 μm or less, more preferably 0.005 μm or more and 0.25 μm or less, even more preferably 0.02 μm or more and 0.10 μm or less. It can be presumed that unreacted substances, compounds after reaction, or mixtures thereof of various compounds of the resin composition are present in the cured resin layer.

[0086] The method for forming the cured resin layer will be described below. The formation of the cured resin layer can be carried out using a coating liquid obtained by diluting the cured resin composition with a solvent. The cured resin layer may be provided by in-line coating (coating and stretching method) that treats the film surface during the film-forming process of the polyester film, or may be provided by off-line coating that is applied outside the system on a once-produced film. In the present invention, the cured resin layer is preferably formed by in-line coating.

[0087] In-line coating is a method of performing coating within the process of manufacturing a polyester film. Specifically, it is a method of performing coating at an arbitrary stage from melting and extruding polyester to stretching and then heat-fixing and winding up. Usually, coating is performed on any of the unstretched sheet obtained by melting and quenching, the uniaxially stretched film, or the biaxially stretched film before heat-fixing.​

[0088] While not limited to the following, for example, in sequential biaxial stretching, a method in which a uniaxially stretched film stretched in the longitudinal direction (machine direction) is coated and then stretched in the width direction is particularly advantageous. With this method, film formation and cured resin layer formation can be performed simultaneously, which offers advantages in terms of manufacturing costs. In addition, since stretching is performed after coating, the thickness of the cured resin layer can be varied according to the stretching ratio, making thin-film coating easier compared to offline coating.

[0089] Furthermore, by providing a cured resin layer on the film before stretching, the cured resin layer can be stretched together with the polyester film, thus allowing the cured resin layer to adhere firmly to the polyester film. Furthermore, in the manufacturing of biaxially oriented polyester film, the film can be restrained in both the longitudinal and width directions by gripping the film edges with clips or the like while stretching, allowing for high-temperature processing during the heat-setting process while maintaining flatness without wrinkles or other defects. As described above, the heat treatment applied after coating can reach temperatures that cannot be achieved by other methods, improving the film-forming properties of the cured resin layer, allowing for stronger adhesion between the cured resin layer and the polyester film, and further resulting in a more robust cured resin layer.

[0090] Conventional coating methods such as air doctor coating, blade coating, rod coating, bar coating, knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss roll coating, cast coating, spray coating, curtain coating, calender coating, and extrusion coating can be used as methods for applying the coating solution to the polyester film.

[0091] Furthermore, to the extent that the spirit of the present invention is not impaired, the coating liquid that forms the cured resin layer may optionally contain defoaming agents, coating properties improvers, thickeners, inorganic and organic particles, organic lubricants, ultraviolet absorbers, antioxidants, foaming agents, dyes, pigments, etc.

[0092] The drying and curing conditions when forming a cured resin layer on a polyester film are not particularly limited. For example, when providing a cured resin layer by offline coating, it is generally preferable to perform heat treatment at 80-200°C for 3-40 seconds, preferably at 100-180°C for 3-40 seconds.

[0093] On the other hand, when a cured resin layer is provided by in-line coating, it is generally preferable to perform heat treatment at 70 to 270°C for 3 to 200 seconds, more preferably at 100 to 250°C for 10 to 100 seconds.

[0094] Regardless of whether it is offline coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as needed. The polyester film constituting the laminated polyester film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

[0095] The master roll width of the laminated polyester film of the present invention, which has a cured resin layer on at least one surface of the polyester film, is not particularly limited, but from the viewpoint of productivity, it is preferably 4000 mm or more, more preferably 5000 mm or more, and even more preferably 6000 mm or more. On the other hand, from the viewpoint of workability, the upper limit of the master roll width is preferably 20000 mm or less, and more preferably 10000 mm or less.

[0096] The master roll of the laminated polyester film described above can be further slit to produce rolls of a manageable size. The width of the slit roll of the laminated polyester film obtained after slitting is not particularly limited, but from the viewpoint of productivity, it is preferably 1500 mm or more, more preferably 1600 mm or more, and even more preferably 1800 mm or more. On the other hand, from the viewpoint of workability, the upper limit is preferably 5000 mm or less.

[0097] <Physical properties of laminated polyester film> (Film Haze) Regarding laminated polyester films, for example, high transparency may be required even after prolonged exposure to a high-temperature atmosphere. The initial film haze is preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 2.0% or less. When the initial film haze is 5.0% or less, visibility is good, making it suitable for applications requiring high visibility, such as optical applications.

[0098] (Birefringence of film) Birefringence of polyester film (Δn × 10) 3 ) is preferably 50 or more, more preferably 55 or more. By satisfying the aforementioned range, stable performance can be ensured regardless of the product sampling location, even when the film is widened.

[0099] The antistatic properties of a laminated polyester film can be evaluated by measuring the surface resistivity of the cured resin layer.

[0100] Cured resin layer (surface resistivity I) The surface resistivity of the cured resin layer is not particularly limited, but for example, preferably 1 × 10⁻⁶. 8 Ω / □ or less, more preferably 1 × 10 7 Ω / □ or less, more preferably 1 × 10 6 It is less than or equal to Ω / □. There is no particular lower limit for surface resistivity, but considering the cost of antistatic agents, it is 1 × 10 4It is preferable to have a surface resistivity of Ω / □ or higher. The lower the surface resistivity of the cured resin layer, the better the antistatic properties. For example, peeling charge during the process of peeling the release film from the adhesive layer provided on the cured resin layer can be suppressed, and the adhesion of foreign matter can be prevented.

[0101] Cured resin layer after rubbing treatment (surface resistivity II) Regarding the surface resistivity of the cured resin layer surface after rubbing treatment, preferably 1 × 10⁻⁶ 8 Ω / □ or less, more preferably 1.0 × 10 8 Ω / □ or less, more preferably 1 × 10 7 Ω / □ or less, more preferably 1 × 10 6 It is less than or equal to Ω / □. There is no particular lower limit for surface resistivity, but considering the cost of antistatic agents, it is 1 × 10 4 It is preferable to set it to Ω / □ or greater.

[0102] Cured resin layer (surface resistivity III) after rubbing treatment following humidification (exposure to a 23°C, 90%RH atmosphere for 24 hours). The surface resistivity of the cured resin layer surface after rubbing treatment following humidification (exposure to a 23°C, 90%RH atmosphere for 24 hours) is preferably 1 × 10⁻⁶. 9 Ω / □ or less, more preferably 3 × 10 8 Ω / □ or less, more preferably 1 × 10 7 It is less than or equal to Ω / □. There is no particular lower limit for surface resistivity, but considering the cost of antistatic agents, it is 1 × 10 4 It is preferable to set it to Ω / □ or greater.

[0103] Cured resin layer after 7 days of exposure to air (surface resistivity IV) The surface resistivity of the cured resin layer surface after 7 days of exposure to air is preferably 1 × 10⁻⁶. 8 Ω / □ or less, more preferably 1 × 10 7 Ω / □ or less, more preferably 1 × 10 6 It is less than or equal to Ω / □. There is no particular lower limit for surface resistivity, but considering the cost of antistatic agents, it is 1 × 10 4 It is preferable to set it to Ω / □ or greater.

[0104] (Arithmetic mean height (Sa) and maximum peak height (Sp) of the polyester film surface opposite to the side where the cured resin layer is provided.) The arithmetic mean height (Sa) of the polyester film surface on the side opposite to the side where the cured resin layer is provided is preferably 40 nm or less, more preferably 30 nm or less, even more preferably 20 nm or less, particularly preferably 15 nm or less, and most preferably 13 nm or less. The maximum peak height (Sp) of the polyester film surface on the side opposite to the side where the cured resin layer is provided is preferably 350 nm or less, more preferably 300 nm or less, and even more preferably 280 nm or less. When the Sa and Sp values ​​of the polyester film surface on the aforementioned side are within the specified range, the surface on the side where the cured resin layer is to be applied becomes suitable for stronger adhesion between the cured resin layer and the polyester film. Furthermore, it is possible to impart excellent properties (low haze value, appropriate gloss value) to the laminated polyester film.

[0105] (Arithmetic mean height (Sa) and maximum peak height (Sp) of the surface of the cured resin layer) The arithmetic mean height (Sa) of the surface of the cured resin layer is preferably 30 nm or less, more preferably 20 nm or less, even more preferably 15 nm or less, and particularly preferably 13 nm or less. The maximum peak height (Sp) on the surface of the cured resin layer is preferably 350 nm or less, more preferably 300 nm or less, and even more preferably 280 nm or less. If the Sa and Sp on the surface of the cured resin layer are within the above range, then, for example, in a film laminate embodiment that further has functional layers such as an adhesive layer or a release layer on the cured resin layer (described later), problems when attaching it to an object can be avoided.

[0106] The arithmetic mean height (Sa, ISO 25178 Surface Texture) is a parameter that extends Ra (arithmetic mean height of a line) to a surface, and represents the average of the absolute differences in height between each point relative to the average surface. The maximum peak height (Sp, ISO 25178 Surface Texture) is a three-dimensional extension of the two-dimensional maximum peak height (Rp), and represents the maximum height from the surface where the height is 0 in the measurement area.

[0107] The laminated polyester film of the present invention preferably further has a functional layer. That is, in one embodiment of the present invention, a laminated polyester film with a functional layer is provided, wherein the functional layer is further provided on or on the opposite side of the cured resin layer of the laminated polyester film of the present invention. For example, when the functional layer is on top of the cured resin layer, it is preferable to have a layer structure in the order of polyester film / cured resin layer / functional layer. Examples of functional layers include adhesive layers, bonding layers, release layers, hard coat layers, and ink layers, which are layers provided to impart various functions.

[0108] When an acrylic adhesive layer or a urethane adhesive layer is formed on the cured resin layer, the cured resin layer functions as a release layer for those adhesive layers. However, when a silicone adhesive layer is formed, the cured resin layer functions as an easy-adhesion layer.

[0109] <Adhesive layer> In the laminated polyester film of the present invention, it is preferable that an adhesive layer is provided on the cured resin layer. The adhesive layer is preferably an acrylic adhesive layer, a urethane adhesive layer, or a silicone adhesive layer.

[0110] (Silicone-based adhesive layer) The silicone adhesive that constitutes the silicone-based adhesive layer can be any adhesive whose main component is silicone resin. The term "main component resin" refers to the resin that makes up the adhesive by the largest proportion (mass) of the resins in the adhesive. Examples of silicone adhesives include addition reaction type, peroxide curing type, or condensation reaction type silicone adhesives. Among these, addition reaction type silicone adhesives are preferred from the viewpoint of being able to cure at low temperatures and in a short time. These addition reaction type silicone adhesives form an adhesive layer on the support by curing. When an addition reaction type silicone adhesive is used as the silicone adhesive, the silicone adhesive may contain a catalyst such as a platinum catalyst.

[0111] For example, an addition-reaction type silicone adhesive can be prepared by diluting a silicone resin solution with a solvent such as toluene as needed, adding a catalyst such as a platinum catalyst, stirring until homogeneous, applying it to a support, and curing it at 100-130°C for 1-5 minutes. If necessary, a crosslinking agent or additives to control the adhesive strength may be added to the addition-reaction type silicone adhesive, or the base film may be treated with a primer before the formation of the adhesive layer.

[0112] Examples of commercially available silicone resins used in addition-reaction type silicone adhesives include SD4580PSA, SD4584PSA, SD4585PSA, SD4587LPSA, SD4560PSA, SD4570PSA, SD4600FCPSA, SD4593PSA, DC7651ADHESIVE, DC7652ADHESIVE, LTC-755, LTC-310 (all manufactured by Toray Dow Corning), KR-3700, KR-3701, KR-3704, X-40-3237-1, X-40-3240, Examples include X-40-3291-1, X-40-3229, X-40-3323, X-40-3306, X-40-3270-1 (all manufactured by Shin-Etsu Chemical Co., Ltd.), AS-PSA001, AS-PSA002, AS-PSA003, AS-PSA004, AS-PSA005, AS-PSA012, AS-PSA014, PSA-7465 (all manufactured by Arakawa Chemical Industries, Ltd.), TSR1512, TSR1516, TSR1521 (all manufactured by Momentive Performance Materials, Inc.).

[0113] The thickness of the silicone adhesive layer (after drying) is preferably 1 to 100 μm, more preferably 5 to 80 μm, even more preferably 10 to 60 μm, and still more preferably 20 to 50 μm.

[0114] (Acrylic adhesive layer) The acrylic adhesive layer can be formed from an adhesive composition containing a (meth)acrylic acid ester (co)polymer, and optionally further containing a photopolymerization initiator, a crosslinking agent, a silane coupling agent, and other materials. The acrylic adhesive layer can be formed from conventionally known adhesive compositions, for example, the adhesive composition described in Japanese Patent Application Publication No. 2019-210446 can be used.

[0115] <Urethane-based adhesive> As the urethane-based base polymer for urethane-based adhesives, a reaction product of a polyol and a polyisocyanate compound can be used. Examples of polyol components include high-molecular-weight polyols such as polyester polyols, polyether polyols, polycarbonate polyols, and caprolactone polyols. These polyol components may be used individually or in combination of two or more types. Examples of polyisocyanate compounds include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates. These polyisocyanate compounds may be used individually or in combination of two or more.

[0116] The thickness (after drying) of the acrylic adhesive layer and the urethane adhesive layer is preferably 1 to 100 μm, more preferably 5 to 80 μm, even more preferably 10 to 60 μm, and particularly preferably 20 to 50 μm.

[0117] From the viewpoint of ease of handling, the total thickness of the laminated polyester film with an adhesive layer is preferably 200 μm or less, more preferably 9 μm to 150 μm, even more preferably 12 μm to 125 μm, and even more preferably 25 μm to 100 μm.

[0118] <Applications of Laminated Polyester Film> The laminated polyester film of the present invention can be suitably used as a base material for various components, etc., from the viewpoint of having excellent adhesion to silicone adhesives. Furthermore, a laminated polyester film with a functional layer having the above-mentioned functional layer such as an adhesive can be suitably used as a surface protective film by laminating it to the surface of a component such as an optical component via a silicone adhesive. However, the present invention is not limited to this method of use.

[0119] <Film laminate> According to the present invention, a film laminate having the above-mentioned laminated polyester film can be provided. One first embodiment of the film laminate is a form in which various components are bonded together via a silicone adhesive layer on the cured resin layer of the functional layered laminated polyester film described above. As an example, a case in which an optical component (such as another resin film or glass substrate) is used will be described.

[0120] (Optical components) Examples of optical components include other resin films or glass substrates. Preferably, the other resin film is selected from polyester films, polyimide films, or cyclic polyolefin films.

[0121] As a second embodiment of the film laminate, "other release films" can also be laminated to the laminated polyester film via a silicone adhesive layer on the cured resin layer. The release layer constituting the release film is preferably a release layer containing at least one selected from the group consisting of a curable silicone resin, a fluorine-based compound, and a long-chain alkyl compound.

[0122] An example of the release layer is one that comprises, in sequence, a first layer formed from a silicone composition mainly containing a curable silicone that does not contain a fluorine substituent, and a second layer containing a component having a fluorine substituent.

[0123] Another example of the aforementioned release layer is a layer formed from a silicone composition mainly containing a curable silicone containing a fluorine substituent.

[0124] Furthermore, another example of the release layer is a layer formed from a silicone composition mainly containing a curable silicone that does not contain fluorine substituents.

[0125] The case of the acrylic adhesive or urethane adhesive described above is also included in the second embodiment described above.

[0126] <Method for manufacturing a film laminate> The method for manufacturing the film laminate of the present invention is not particularly limited. For example, the film laminate of the present invention can be manufactured by applying a silicone adhesive layer forming liquid to the cured resin layer of the silicone adhesive laminate polyester film of the present invention using an applicator to form a silicone adhesive layer, and then laminating an optical component (such as another resin film) or another release film onto the silicone adhesive layer. The method for applying the silicone adhesive layer forming liquid is not particularly limited and can be carried out by conventionally known methods. Furthermore, as described above, other resin films may be provided with a functional layer (such as release properties, hard coating properties, antistatic properties, anti-glare properties, improved visibility, fingerprint resistance, and stain resistance) on the surface in contact with the silicone adhesive layer.

[0127] <Applications of film laminates> Film laminates having a silicone adhesive with good durability and transparency can be suitably used in various applications by taking advantage of the heat resistance, cold resistance, weather resistance, and high transparency of the silicone adhesive itself. [Examples]

[0128] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention. The evaluation methods in the examples and comparative examples are as follows.

[0129] (1) Method for measuring the intrinsic viscosity of polyester One g of polyester, from which incompatible components had been removed, was accurately weighed, dissolved in 100 ml of a phenol / tetrachloroethane mixed solvent (50 / 50 by mass ratio), and measured at 30°C.

[0130] (2) Average particle size (d 50 Measurement method for :μm The average particle size was defined as the 50% cumulative (mass-based) value of the equivalent spherical distribution measured using a centrifugal sedimentation particle size distribution analyzer (SA-CP3 model, manufactured by Shimadzu Corporation).

[0131] (3) Method for measuring film haze Measurements were taken using a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute Co., Ltd.) in accordance with JIS K 7136:2000.

[0132] (4) Birefringence Measurement Using an Abbe refractometer (NAR-1T, manufactured by Atago Optical Co., Ltd.), the maximum refractive index nγ within the film plane and the refractive index nβ perpendicular to it were measured, and Δn (=nγ-nβ) × 10⁻¹⁰ 3 The refractive index was determined. The refractive index was measured using a sodium D line at 23°C.

[0133] (5) Surface resistivity of the cured resin layer I A low resistivity meter (Loresta GP MCP-T600, manufactured by Nitto Seiko Analytech Co., Ltd.) was used to conditioned the sample for 30 minutes in a measurement atmosphere of 23°C and 50% relative humidity. Surface resistivity was then measured, and the value after 1 minute was taken as the surface resistivity. The resistivity correction factor (RCF value) was kept constant at 4.235. If the resistance value exceeded the upper limit of the measurable range, measurement was deemed impossible.

[0134] (6) Surface resistivity II of the cured resin layer surface (after rubbing treatment, without humidification) Using a rubbing tester (manufactured by Ohira Rika Kogyo Co., Ltd.), a 5cm x 7cm flat abrasive was tightly wrapped with four layers of 5cm x 10cm cupro nonwoven fabric (Ozu Sangyo Co., Ltd.'s "Bencot M-3II"), and the surface resistivity was measured after rubbing the resin layer surface of the laminated polyester film obtained in the examples and comparative examples for two back-and-forth strokes (over a 15cm length) under a load of 680g. The method for measuring surface resistivity is as described in (5).

[0135] (7) Surface resistivity of the cured resin layer (III) (after rubbing treatment and humidification) After adjusting the surface at 23°C and 90% RH for 24 hours, the rubbing treatment described in section (6) was performed, and the surface resistivity was measured. The method for measuring the surface resistivity is as described in section (5).

[0136] (8) Surface resistivity IV of the cured resin layer surface (after exposure to air) After 7 days of exposure to air, the rubbing treatment described in section (6) was performed, and the surface resistivity was measured. The method for measuring the surface resistivity is as described in section (5).

[0137] (9) Arithmetic mean height (Sa) and maximum peak height (Sp) In the laminated polyester films of the examples and comparative examples, a non-contact surface and layer cross-sectional shape measurement system, Vert Scan® R550GML (manufactured by Ryoka Systems Co., Ltd.), was used to measure a 640 μm × 480 μm area on the film surface and the surface of the cured resin layer on the side opposite to the side where the cured resin layer is provided, under the following measurement conditions. The arithmetic mean height (Sa) and maximum peak height (Sp) of the cured resin layer surface were calculated using the output obtained by a fourth-order polynomial correction. (Measurement conditions) CCD camera: SONY HR-50 1 / 3" Objective lens: 20x Lens barrel: 1X Body Zoom lens: No Relay Wavelength filter: 530 white Measurement mode: Under Wave conditions

[0138] The polyester used in the examples and comparative examples was prepared as follows. [Polyester (A)] 100 parts by mass of dimethyl terephthalate and 65 parts by mass of ethylene glycol were charged into a transesterification reactor equipped with a stirrer, a heating device, and a distillate separation column, and heated to 150°C to melt the dimethyl terephthalate. Next, an ethylene glycol solution of magnesium acetate tetrahydrate was added so that the amount of magnesium acetate added to the resulting polyester was 0.09% by mass. Subsequently, the temperature was raised to 225°C over 3 hours under atmospheric pressure, and then the mixture was stirred and maintained at 225°C for 1 hour and 15 minutes while methanol was distilled off to carry out the transesterification reaction, effectively completing the transesterification reaction and yielding a low-polymer polyester (oligomer). The obtained oligomer was transferred to a polycondensation reactor equipped with a stirrer and a distillation tube. An ethylene glycol solution of magnesium acetate tetrahydrate was added to the transferred oligomer so that the amount of magnesium acetate added relative to the resulting polyester resin was 0.09% by mass. Subsequently, an ethylene glycol solution of phosphoric acid was added as a heat stabilizer so that the amount of phosphoric acid added to the resulting polyester was 0.017% by mass. Next, an ethylene glycol solution of tetrabutyl titanate was added to the oligomer as a polycondensation catalyst in such a concentration of titanium atoms as 4.5 ppm by mass relative to the resulting polyester. Subsequently, the pressure was reduced from 101.3 kPa to 0.4 kPa over 85 minutes and maintained at 0.4 kPa. The temperature was then raised from 225°C to 280°C over 2 hours and maintained at 280°C for 1.5 hours to carry out a melt polycondensation reaction, yielding polyester A with an intrinsic viscosity (IV) of 0.63 dL / g.

[0139] [Polyester (B)] In the method for producing polyester (A), polyester (B) with an intrinsic viscosity (IV) of 0.63 dL / g was obtained using the same method as for producing polyester (A), except that 0.3 parts by mass of silica particles with an average particle size of 2 μm were added before melt polymerization.

[0140] Examples of compounds that make up the cured resin layer are as follows: (Compound (a)) A conductive agent consisting of polyethylenedioxythiophene and polystyrene sulfonic acid (Orgacon ICP1010, manufactured by Agfa-Agewalt) was neutralized with concentrated ammonia water to a pH of 9. Non-volatile component: 1.2% by mass, solvent: water

[0141] (Compound (b)) • Acrylic resin aqueous dispersion polymerized with the following composition Styrene / acrylic acid = 85 / 15 (mass%), non-volatile components; 30% by mass

[0142] (Compound (c)) • Polyglycerin with an average n=4 in equation (3) [ka]

[0143] (Compound (d)) ·wax In an emulsifying apparatus with a capacity of 1.5 L equipped with a stirrer, thermometer, and temperature controller, 300 g of polyethylene oxide wax with a melting point of 105°C, an acid value of 16 mg KOH / g, a density of 0.93 g / mL, and a number-average molecular weight of 5000, 650 g of deionized water, 50 g of decaglycerin monooleate surfactant, and 10 g of 48% potassium hydroxide aqueous solution were added. After purging the emulsifying apparatus with nitrogen, it was sealed and rapidly stirred at 150°C for 1 hour, then cooled to 130°C, passed through a high-pressure homogenizer under 400 atmospheres, and cooled to 40°C to obtain the wax emulsion.

[0144] (Crosslinking agent) (E): Hexamethoxymethylolmelamine

[0145] (Surfactants) • (F): A nonionic surfactant having a polyethylene oxide side chain, as shown in the formula below.

[0146] [ka] (In the formula, the mean of m+n is 10)

[0147] Example 1 A mixed raw material consisting of polyester (A) and (B) in proportions of 94% and 6% by mass, respectively, was used as the raw material for the outermost layer (surface layer), while polyester (A) alone was used as the raw material for the intermediate layer. The raw materials for the outermost and intermediate layers were each supplied to two extruders, melted at 285°C, and then co-extruded and cooled and solidified on a rotating cooling roll set at 40°C in a layer configuration of two types and three layers (thickness composition ratio of surface layer / intermediate layer / surface layer = 1 / 8 / 1) to obtain an unstretched sheet. Next, this film was stretched 3.5 times in the longitudinal direction while passing through a group of heated rolls at 85°C to obtain a uniaxially oriented film. On one side of this uniaxially oriented film, coating liquid 1 having the composition shown in Table 1 below was applied at a coating amount (after drying) of 0.05 g / m². 2 The film was then coated in the manner described above. Next, this film was guided into a tenter stretcher, stretched 4.3 times in the width direction at 100°C, and then heat-treated at 235°C. After that, a 2% relaxation treatment was performed in the width direction to obtain a laminated polyester film with a thickness of 50 μm. The Sa on the surface opposite to the side with the cured resin layer was 12 nm and the Sp was 274 nm. The evaluation results are shown in Table 2. As shown in Table 2, the resulting laminated polyester film exhibited good abrasion resistance and resistance to air exposure.

[0148] (Examples 2-4) In Example 1, a laminated polyester film was obtained by manufacturing in the same manner as in Example 1, except that the cured resin layer composition was determined by applying coating solutions 2 to 4 shown in Table 1. The results are shown in Table 2.

[0149] (Comparative Example 1) In Example 1, a laminated polyester film was obtained by manufacturing in the same manner as in Example 1, except that the cured resin layer composition was set to coating solution 5 as shown in Table 1. The results are shown in Table 2.

[0150] [Table 1]

[0151] [Table 2] [Industrial applicability]

[0152] The laminated polyester film of the present invention has excellent antistatic properties after rubbing treatment or exposure to air, making it suitable for applications where the inclusion of foreign matter is undesirable. For example, it is suitable for use as a surface protection film, which is bonded to various components via an adhesive layer.

Claims

1. A hardened resin layer is provided on at least one surface of the polyester film. The cured resin layer is a cured product of a resin composition containing the following compounds (a), (b), (c), and (d): The surface resistivity of the cured resin layer after the following rubbing treatment is 1 × 10 ８ (Ω / □) or less, A laminated polyester film in which the arithmetic mean height (Sa) of the surface opposite to the surface on which the cured resin layer is provided is 15 nm or less, and the maximum peak height (Sp) is 350 nm or less. (a) At least one selected from the group consisting of (a1) a polymer obtained by doping a compound comprising thiophene or a thiophene derivative with another anionic compound, and (a2) a polymer obtained by self-doping a compound comprising thiophene or a thiophene derivative having an anionic group. (b) A (meth)acrylic polymer having a styrene structure, wherein the proportion of styrene and styrene derivatives is 50 to 97 mol% based on the total amount of monomers constituting the (meth)acrylic polymer having a styrene structure. (c) At least one compound selected from the group consisting of (c1) polyglycerin and (c2) alkylene oxide adducts to polyglycerin, or a derivative thereof. (d) Release agent Rubbing treatment conditions: A flat friction plate measuring 5 cm x 7 cm is tightly wrapped with four layers of cupro nonwoven fabric (Ozu Sangyo Co., Ltd.'s "Bencot M-3II") measuring 5 cm x 10 cm, and rubbed against the surface of the resin layer of a laminated polyester film twice (over a 15 cm length) with a load of 680 g.

2. The laminated polyester film according to claim 1, wherein the acrylic structure of the (meth)acrylic polymer is a (meth)acrylic acid structure.

3. The laminated polyester film according to claim 1 or 2, wherein the release agent is wax.

4. The laminated polyester film according to any one of claims 1 to 3, wherein the resin composition contains at least one selected from the group consisting of melamine compounds, epoxy compounds, isocyanate compounds, and carbodiimide compounds as a crosslinking agent.

5. The laminated polyester film according to any one of claims 1 to 4, wherein the cured resin layer is provided by in-line coating (coating and stretching method).

6. The laminated polyester film according to any one of claims 1 to 5, wherein the polyester film has a multilayer structure comprising at least three layers.

7. The birefringence of the polyester film (Δn × 10) ３ A laminated polyester film according to any one of claims 1 to 6, wherein the ratio is 50 or more.

8. The laminated polyester film according to any one of claims 1 to 7, wherein the master roll width of the laminated polyester film is 6,000 mm or more.

9. The laminated polyester film according to claim 8, wherein the slit roll width of the laminated polyester film is 1500 mm or more.

10. The laminated polyester film according to any one of claims 1 to 9, wherein the (meth)acrylic polymer having a styrene structure is a polymer whose constituent units are acrylic acid or alkyl acrylate.

11. The laminated polyester film according to any one of claims 1 to 10, wherein the proportion of (meth)acrylic acid or alkyl (meth)acrylate ester in the (meth)acrylic polymer having a styrene structure is 5 to 40 mol%.

12. A laminated polyester film with a functional layer, wherein the functional layer is provided on or on the opposite side of the cured resin layer of the laminated polyester film according to any one of claims 1 to 11.

13. The functional layer is an adhesive layer, as described in claim 12, for the laminated polyester film with a functional layer.

14. The laminated polyester film with a functional layer according to claim 13, wherein the adhesive layer is a silicone-based adhesive layer.

15. The laminated polyester film with a functional layer according to claim 13, wherein the adhesive layer is an acrylic adhesive layer or a urethane adhesive layer.

16. The functional layer is a release layer, as described in claim 12, for the laminated polyester film with a functional layer.

17. A film laminate in which an optical member is bonded to the adhesive surface of a functional layer-equipped laminated polyester film according to any one of claims 12 to 16.

18. A film laminate comprising a functional layer-equipped laminated polyester film according to any one of claims 12 to 16, wherein a release film is laminated to the adhesive layer surface of the laminated polyester film.

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