Laminated polyester film

Abstract

The purpose of the present invention is to provide a laminated polyester film having excellent abrasion resistance and transparency, and excellent processability such as workability and slipperiness when winding the film into a roll.　The present invention pertains to a laminated polyester film comprising a functional layer on at least one surface of a polyester film. The air release index (mmH2O) of the surface having the functional layer is at most 493 mmH2O, and the number of coarse objects having a shortest diameter of at least 3 μm and being present per 1 mm2 in the surface having the functional layer is at most 250.

Description

Laminated Polyester Film

[0001] The present invention relates to a laminated polyester film, and more particularly to a laminated polyester film that is excellent in transparency and slipperiness, is free from scratches, and is capable of forming a photoresist layer that has excellent resolution and pattern formability on the surface and edges, and that also has excellent abrasion resistance and antistatic properties, and further has good lamination processability, making it suitable for use as a photoresist for ultrafine lines.

[0002] BACKGROUND ART Polyester films, typified by polyethylene terephthalate and polyethylene naphthalate, have been used in various applications because they have excellent properties such as mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, and optical properties, and also have excellent cost performance.

[0003] One application example of polyester film is the film used in the dry film resist process, which is used in the manufacture of flexible printed wiring boards. Dry film resists, for example, consist of a three-layer structure: a substrate film, a photosensitive resin layer, and a protective film. The substrate film is typically a polyester film, which offers excellent mechanical and optical properties, chemical resistance, heat resistance, dimensional stability, and flatness. Briefly, the protective film is first peeled off, and the exposed photosensitive resin layer is then adhered to a conductive substrate attached to a board. Next, a glass plate or film (called a photomask) with a printed circuit is adhered to the substrate film, and light is irradiated from the photomask side. This irradiated light is typically ultraviolet light. Light passes through the transparent portions of the circuit printed on the photomask, and only the exposed portions of the photosensitive resin react. The glass plate and substrate film are then removed, and the unexposed portions of the photosensitive resin layer are removed using an appropriate solvent. Further, by etching with an acid or the like, the photosensitive resin layer is removed and the conductive substrate layer is formed as a circuit.

[0004] Recently, high reproducibility and resolution in circuit pattern formation have been required, leading to extremely complex circuits on printed circuit boards, with thin wires and narrower spacing between them. When exposing a photoresist layer in a photoresist film, as mentioned above, light passes through the support (substrate film). Therefore, if the support has low transparency, problems such as insufficient exposure of the photoresist layer or reduced resolution due to light scattering can occur. For this reason, it is important that the polyester film used as the support has low haze and excellent transparency. Furthermore, scratches on the film surface can cause problems such as scattering of transmitted light and reduced resolution, so the film surface must be free of scratches.

[0005] Polyester films with a smooth surface, high transparency, and low film haze are difficult to handle during the film production process, winding process, etc. When such a film roll is used, the surface is easily scratched, and air trapped in the film is difficult to escape during the winding process, resulting in wrinkles and other problems.

[0006] It is important for the polyester film used as the support to have a suitable degree of slipperiness in order to improve the handleability when a photoresist layer is formed on the support to produce a photoresist film, or to improve the handleability of the photoresist film itself. Furthermore, air release properties are also required to prevent problems such as air bubbles from entering between the support and the glass plate on which the circuit pattern is formed during the production of a printed circuit board, impairing the reproducibility of the circuit pattern.

[0007] In order to satisfy these market demands, a method of incorporating particles into a polyester film to form fine protrusions on the surface has been used, and many particle blending techniques, multilayering techniques, and combinations of these techniques have been disclosed for forming protrusions on the film surface (see, for example, Patent Documents 1 to 10). Furthermore, Patent Documents 3 and 4 above disclose techniques for improving the handleability of polyester films for photoresists when produced, preventing the adhesion of dust and foreign matter, and the handleability of photoresist films themselves using such films, by blending an antistatic agent.

[0008] The above-mentioned techniques have improved the handling properties while maintaining the transparency of the film. In particular, the techniques of Patent Documents 3 and 4 contain particles only in a thin surface layer formed on a polyester film support, and the content is kept to a low level, resulting in extremely high transparency and antistatic properties, and have attracted attention for their excellent optical properties as polyester films for ultrafine line photoresists.

[0009] However, conventional techniques, including this technique, have been designed with a focus on handling, primarily on the slipperiness of the film, and no consideration has been given to the abrasion resistance of the film during processing. As a result, for example, in the process of laminating a composite film, in which a resist layer is laminated on a photoresist film, onto a wiring board, friction with a film holding device used to cut the composite film to the dimensions of the wiring board causes scratches on the side of the composite film opposite to the side on which the resist layer is formed, resulting in a problem of a decrease in the light transmittance of the composite film and a decrease in the resolution of the resist.

[0010] Furthermore, problems have become apparent regarding scratches on the film surface due to friction with rolls used to press the composite film onto the wiring board during the lamination process, and surface contamination of the composite film due to resin powder generated by the scratches. Therefore, there has been a strong demand for the development of a polyester film for ultrafine line photoresists that maintains transparency and handleability while also improving abrasion resistance.

[0011] In order to solve such problems, Patent Document 11 discloses that a resin composition layer containing silica particles is formed on the surface of a laminated polyester film opposite to the resist layer side, and by increasing the thickness of the resin composition layer, the particles are prevented from falling off and the abrasion resistance is improved.

[0012] JP 10-46012 A JP 10-128930 A JP 2000-221688 A JP 2001-117237 A JP 2002-60598 A JP 2002-62661 A JP 2002-72486 A JP 2002-278072 A JP 2002-341546 A JP 2003-43691 A JP 2006-327158 A JP 2019-143132 A

[0013] As described above, the techniques of Patent Documents 1 to 10 require further improvement in properties for use as polyester films for ultrafine line photoresists, and Patent Documents 11 and 12 were developed to solve this problem.

[0014] However, the required level of abrasion resistance is becoming higher, and further improvement is required. Also, as shown in Patent Document 12, a polyester film for a dry film resist substrate that is substantially free of particles having a particle size of more than 1 μm may cause blocking of the film depending on the resist formation conditions, for example, ultraviolet irradiation.

[0015] The present invention has been made in view of the problems of the prior art. That is, an object of the present invention is to provide a laminated polyester film that is excellent in abrasion resistance and transparency, and is excellent in workability when wound into a roll and in processability such as easy lubricity.

[0016] As a result of extensive investigations into achieving the above object, the present inventors have found that the above problems can be solved by making a film with a specific structure, and have thus completed the present invention.

[0017] That is, the present invention comprises the following:

[0018] [1] A polyester film having a functional layer on at least one side thereof, the air release index (mmH2O) of the side having the functional layer being 493 mmH2O or less, and 2 A laminated polyester film in which the number of coarse particles having a minimum diameter of 3 μm or more per unit area is 250 or less.

[0019] [2] The laminated polyester film according to [1], having a haze of 1.0% or less.

[0020] [3] A laminated polyester film according to [1] or [2], in which the logarithm (log(Ω / □)) of the surface resistivity (Ω / □) of at least one side of the laminated polyester film measured under an environment of a temperature of 23°C and a humidity of 65% RH is 13 or less.

[0021] [4] The laminated polyester film according to any one of [1] to [3], wherein the functional layer contains particles, the particles have a D50 of 1 μm or less, and the D90 / D50 of the particles is 3 or less.

[0022] [5] The laminated polyester film according to any one of [1] to [4], which is used for a photoresist for ultrafine lines.

[0023] [6] A support for a fine line photoresist, comprising the laminated polyester film according to any one of [1] to [4].

[0024] [7] An ultrafine line photoresist film comprising the laminated polyester film according to any one of [1] to [4].

[0025] The laminated polyester film of the present invention is suitable as a polyester film for ultrafine line photoresists. This is because the present invention has excellent transparency, slipperiness, antistatic properties, and abrasion resistance, and has a scratch-free surface, making it suitable as a support for ultrafine line photoresist films. Photoresist films using the polyester film for ultrafine line photoresists of the present invention as a support exhibit excellent photoresist layer resolution, pattern formability on the surface and edges, and adhesion of the photoresist layer. Furthermore, they exhibit excellent handling properties and durability, such as blocking and abrasion resistance, when producing photoresist films using the polyester film for ultrafine line photoresists of the present invention as a support, making them suitable for processing such as lamination and useful for industrial applications.

[0026] Furthermore, since the air release index of the surface having the functional layer satisfies a predetermined condition, the air trapped when the film is wound into a roll can be easily released, and the film can be wound up in close contact with each other. Furthermore, for example, it is possible to prevent the film from shifting toward the core during storage or transportation, and to prevent damage due to shifting.

[0027] As used herein, the phrase "comprising" is intended to encompass the phrases "consisting essentially of" and "consisting of."

[0028] In this specification, with regard to a numerical range, "to" means equal to or greater than the leftmost numerical value and equal to or less than the rightmost numerical value. For example, "0.5 to 10% by mass" and "0.5% to 10% by mass" both mean "0.5% by mass or greater and 10% by mass or less." Furthermore, with regard to a numerical range, "equal to or greater than" means "the same as or greater than," and "equal to or less than" means "the same as or less than."

[0029] In the numerical ranges described in stages in this specification, the upper or lower limit of a numerical range in a certain stage can be arbitrarily combined with the upper or lower limit of a numerical range in the same stage or in another stage. In addition, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in an example or a value that can be unambiguously derived from an example.

[0030] (Polyester Film Substrate) The polyester film constituting the laminated polyester film of the present invention (preferably a polyester film for ultrafine line photoresists) (hereinafter sometimes simply referred to as the main layer film) is preferably a biaxially oriented polyester film having a thickness of 12 to 25 μm, and examples thereof include films made of polyester-based resins primarily composed of polyesters such as aromatic linear polyesters composed of aromatic dicarboxylic acids and diols, such as polyethylene terephthalate and polyethylene naphthalate, aliphatic linear polyesters composed of aliphatic dicarboxylic acids and diols, and copolymers thereof. Among these, films made of aromatic linear polyester resins, such as polyethylene terephthalate and polyethylene naphthalate, are preferred. The main layer film of the present invention may be formed from one or a mixture of two or more of the above polyester-based resins. Such a main layer film may be a single layer or a multi-layer structure consisting of two or more layers. The film thickness is preferably 12 to 25 μm, more preferably 13 to 20 μm, and even more preferably 14 to 20 μm. When the thickness of the file is 12 to 25 μm, the resolution is good, the strength is excellent, and the file is less likely to break during the peeling operation.

[0031] The catalyst for polycondensation used in producing the polyester resin is not particularly limited, but antimony trioxide is preferred because it is inexpensive and has excellent catalytic activity. It is also preferred to use a germanium compound or a titanium compound. More preferred polycondensation catalysts include catalysts containing aluminum and / or its compound and a phenolic compound, catalysts containing aluminum and / or its compound and a phosphorus compound, and catalysts containing an aluminum salt of a phosphorus compound.

[0032] The polyester film substrate in the present invention is not particularly limited in terms of its layer structure, and may be a single-layer polyester film, a two-layer structure having different components, or a polyester film substrate consisting of at least three layers, including an outer layer and an inner layer.

[0033] The air release index (mmH2O) of at least one surface of the laminated polyester film of the present invention is 493 mmH2O or less, more preferably 492 mmH2O or less, even more preferably 490 mmH2O or less, and particularly preferably 488 mmH2O or less.

[0034] When the air release index is 493 mmH2O or less, air trapped when the film is wound into a roll can be easily released, allowing the film to be wound up with tight contact between the film layers. This prevents the film from shifting toward the core during storage or transportation, and prevents damage due to shifting.

[0035] The air release index is preferably 450 mmH2O or more, such as 460 mmH2O or more, and may be 465 mmH2O or more, such as 470 mmH2O or more. The air release index can be 450-493 mmH2O, 460-493 mmH2O, 465-493 mmH2O, 470-493 mmH2O, 450-492 mmH2O, 460-492 mmH2O, 465-492 mmH2O, 470-492 mmH2O, 450-490 mmH2O, 460-490 mmH2O, 465-490 mmH2O, 470-490 mmH2O, 450-488 mmH2O, 460-488 mmH2O, 465-488 mmH2O, 470-488 mmH2O, etc.

[0036] A smaller air release index is preferable, but if it is 450 mmH2O or more, it is possible to prevent air trapped when the film is wound into a roll from being completely released, improving the adhesion of the film and preventing blocking.

[0037] Furthermore, the laminated polyester film of the present invention has an appropriate air release index, so that the layer structure of the laminated polyester film can be transported and maintained without being crushed.

[0038] The present invention can prevent the layer structure from being crushed during storage and transportation of a film roll, thereby enabling more uniform exposure of the photoresist layer, thereby enabling the formation of a photoresist layer with excellent resolution and pattern formability on the surface and edges.

[0039] Here, in the present invention, "being able to suppress the collapse of the layer structure" means, for example, a state in which there is little deformation in the thickness direction of the laminated film, a state in which there is little change in the thickness unevenness of the laminated film before and after winding, a state in which the polyester film and the functional layer are uniformly adhered to each other without deformation, a state in which there is little deformation in the thickness direction of the functional layer and the number of bulky objects described in the present invention falls within a specified range, etc.

[0040] Although interpretation should not be limited to a specific theory, it is believed that, for example, the present invention can suppress the localized presence of air in a film roll, thereby suppressing the layer structure of the film from being crushed due to uneven distribution of air during winding.

[0041] Since the layer structure can be maintained before and after winding of the film, uneven exposure caused by variations in the film thickness during exposure of the photoresist layer can be avoided, and the exposure amount can be made uniform. Therefore, the present invention is suitable for use in polyester films for ultrafine line photoresists.

[0042] The air release index can be measured by the measurement method described in the examples below.

[0043] The air release index of the present invention can be determined, for example, by laminating a resin composition layer containing 5 to 20 mass % of particles (a) having an average particle size of 0.01 to 0.1 μm and 0.1 to 1 mass % of particles (b) having a 50% volume particle size D50 of 0.3 to 1 μm on the surface opposite to the surface on which the resist layer is laminated, and by coating the resin composition by wet coating and then transporting the coated surface directly to a drying oven without vibrating it on a roll, thereby preventing the collapse of protrusions due to the particles.

[0044] The layer formed using the resin composition layer is the functional layer in the present invention.

[0045] The present invention can prevent the layer structure from being crushed during storage and transportation of a film roll even after exposure of the photoresist layer, and therefore, since blocking of the film can be prevented even after exposure, the laminated polyester film can be easily separated into the functional layer and the polyester film using known techniques, and is also excellent in recyclability.

[0046] The upper limit of the haze of the laminated polyester film of the present invention is preferably 1.0%, more preferably 0.9%, and even more preferably 0.8%. When the haze is 1.0% or less, good resolution tends to be obtained.

[0047] Although a small haze is preferable, from a practical standpoint, the haze is 0.01% or more, for example, 0.05% or more. The haze may be 0.01 to 1.0%, 0.05 to 1.0%, 0.01 to 0.9%, 0.05 to 0.9%, 0.01 to 0.8%, 0.05 to 0.8%, etc.

[0048] The surface of the laminated polyester film of the present invention opposite to the surface on which the resist layer is laminated, i.e., the functional layer surface of the laminated polyester film, may have a logarithm of surface resistivity (Ω / □) at 23°C and 65% RH of not more than 13. The logarithm of such surface resistivity is preferably not more than 12, more preferably not more than 11.

[0049] The logarithm of the surface resistivity (Ω / □) may be 7 or greater, for example, 9 or greater. The logarithm of the surface resistivity (Ω / □) may be 7 to 13, 9 to 13, 7 to 12, 9 to 12, 7 to 11, 9 to 11, or the like.

[0050] By setting the logarithm of the surface resistivity to 13 or less, the polyester film can be prevented from becoming too charged, and the polyester film can be easily handled in the process of producing a main layer film or in the process of producing a photoresist film using the polyester film as a support. For example, adhesion of dust and foreign matter can be reduced, and the photoresist film itself using the polyester film for photoresists of the present invention as a support can be easily handled.

[0051] The upper limit of the static friction coefficient between one side and the opposite side of the laminated polyester film of the present invention is preferably 0.8, more preferably 0.7. A static friction coefficient of 0.8 or less makes it possible to obtain a laminated polyester film that is less susceptible to scratches during the winding process. Regarding the coefficient of friction, adding particles to the functional layer can impart slipperiness while maintaining transparency. While a smaller static friction coefficient is preferable, the coefficient of friction of the laminated polyester film is usually 0.1 or more. The static friction coefficient can be 0.1 to 0.8, 0.1 to 0.7, etc. The static friction coefficient can be measured by the measurement method described in the Examples below.

[0052] The surface of the laminated polyester film of the present invention opposite to the surface on which the resist layer is laminated, i.e., 1 mm 2 The number of coarse particles having a minimum diameter of 3 μm or more present per particle is 250 or less, more preferably 200 or less, even more preferably 150 or less, and particularly preferably 100 or less.

[0053] 1mm in the functional layer 2 When the number of coarse particles having a minimum diameter of 3 μm or more per unit area is 250 or less, the rate of occurrence of exposure defects during exposure of the photoresist layer can be reduced. The number of coarse particles can be measured by the measurement method in the Examples described below.

[0054] On the other hand, 1 mm in the functional layer 2 The number of coarse particles having a minimum diameter of 3 μm or more per 1 mm in the functional layer may be 0 or more, but in order to satisfy the air release index according to the present invention, it is preferably 5 or more, and may be 10 or more. When the lower limit satisfies such a condition, the adhesion of the film is improved and blocking can be suppressed. 2 The number of coarse particles having a shortest diameter of 3 μm or more present per particle may be 0 to 250, 0 to 200, 0 to 150, 0 to 100, 5 to 250, 5 to 200, 5 to 150, 5 to 100, 10 to 250, 10 to 200, 10 to 150, 10 to 100, etc.

[0055] In a preferred embodiment, the above-described properties are imparted by laminating, on the surface opposite to the surface on which the resist layer is to be laminated, a resin composition layer containing 5 to 20 mass% of particles (a) having an average particle size of 0.01 to 0.1 μm, 0.1 to 1 mass% of particles (b) having a 50% volume particle size D50 of 0.3 to 1 μm, 1 to 3 mass% of a wax agent, and 1 to 10 mass% of an antistatic agent. This embodiment maintains high transparency, which is important for achieving high resolution in photoresists, and easily improves the handleability and abrasion resistance of the polyester film for ultrafine line photoresists and composite films obtained by laminating the film with a resist layer.

[0056] For details of the 50% volume particle size D50, see the description of JP-A-2015-174383, etc.

[0057] The resin used to form the resin composition layer can be any resin that is transparent, capable of fixing the particles, wax, antistatic agent, etc., to the polyester film surface, and resistant to abrasion. However, a preferred embodiment is at least one resin selected from the group consisting of polyester-based resins, polyurethane-based resins, acrylic-based resins, amino-based resins, epoxy-based resins, and oxazoline-based resins. The resin may be either a commercially available product or a custom-made product with a specific composition. It may also be classified as either a non-crosslinked or crosslinked product. The type of crosslinking agent is also not important. The resin is used in the form of a solution or dispersion in an organic solvent or a solution or dispersion in an aqueous solvent. A dispersion in an aqueous solvent, i.e., a water-dispersed resin, is particularly preferred in terms of work environment and coatability.

[0058] In the present invention, the particles contained in the resin composition layer are preferably two types of particles having different average particle sizes, from the viewpoint of improving lubricity and abrasion resistance while maintaining transparency. The particles (a) are preferably colloidal silica having an average particle size of 0.02 to 0.08 μm, and more preferably 7 to 17% by mass of the resin component, and even more preferably 5 to 14% by mass of colloidal silica having an average particle size of 0.03 to 0.06 μm.

[0059] The colloidal silica is typically a colloidal dispersion in which ultrafine particles of silicic anhydride (silica) are stably dispersed in water, and is commercially available under brand names such as Lualox from du Pont and Snowtex from Nissan Chemical. While various methods for producing such colloidal silica are known, it is generally produced using an ion exchange resin. Specifically, it is produced by passing an aqueous solution of sodium silicate through a cation exchange resin to form a sol, which is then heated to 60°C or higher to age the sol and grow it into independently dispersed particles. A new sol that has been passed through an ion exchange resin composition layer is then added to the sol, allowing polymerization and precipitation to grow the particle size and produce a stabilized sol. Such colloidal silica sols may be organic solvent-based or aqueous-dispersed. The solvent may be appropriately selected depending on the solvent used to dissolve or disperse the resin. Furthermore, such sols are available in alkaline and acidic stabilized forms, and this selection may be made appropriately depending on the type of resin and actinic crosslinking agent used.

[0060] The upper limit of the 50% volume particle size D50 of the particles (b) is preferably 1 μm, more preferably 0.9 μm, and even more preferably 0.8 μm. When the 50% volume particle size D50 is 1 μm or less, the particle size is 1 mm 2 on the side of the laminated polyester film opposite to the side on which the resist layer is laminated. 2 This reduces the amount of coarse particles of 3 μm or more per particle, and improves abrasion resistance. The lower limit of the 50% volume particle size D50 is preferably 0.35 μm, more preferably 0.4 μm, and even more preferably 0.5 μm. When the 50% volume particle size D50 is 0.5 μm or more, the air release index can be reduced. The 50% volume particle size D50 of particles (b) can be 0.4 to 1 μm, 0.5 to 1 μm, 0.4 to 0.9 μm, 0.5 to 0.9 μm, 0.4 to 0.8 μm, 0.5 to 0.8 μm, or the like.

[0061] The upper limit of the 90% volume particle size D90 / 50% volume particle size D50 of the particles (b) is preferably 3. When the 90% volume particle size D90 / 50% volume particle size D50 is 3 or less, the particle size is 1 mm 2 on the side of the laminated polyester film opposite to the side on which the resist layer is laminated. 2The 90% volume particle size D90 / 50% volume particle size D50 can be 1.0 to 3.0, or 1.0 to 2.0, for example.

[0062] Furthermore, the particles (b) are preferably organic particles.

[0063] The wax agent is not particularly limited as long as it does not impair transparency, and conventionally known wax agents can be used, but it is more preferable to use a polymer-based wax component. Examples include polyethylene-based, polypropylene-based, and fatty acid-based wax agents, with polyethylene-based wax agents being particularly preferred. The weight-average molecular weight of these wax components is preferably 1,000 to 10,000, more preferably 1,500 to 6,000. A molecular weight of less than 1,000 is likely to result in transfer contamination due to leaching from the interior of the resin composition layer to the surface, while a molecular weight of more than 10,000 results in insufficient improvement in slipperiness. The blending amount of these wax components relative to the resin component is more preferably 1 to 10% by mass, even more preferably 1.2 to 8% by mass, and particularly preferably 2 to 5% by mass. Blending the two types of particles with different particle sizes and the wax in the above blending ratio with the resin component can maintain high transparency while imparting slipperiness and abrasion resistance, making it easy to impart the properties required for the polyester film for ultrafine line photoresists.

[0064] The antistatic agent is a compound used for the purpose of imparting antistatic properties. Examples include polymeric antistatic agents composed of one or more polymers of unsaturated monomers having a sulfonate group (e.g., sodium vinyl sulfonate, sodium methallyl sulfonate, sodium styrene sulfonate, ammonium vinyl sulfonate, potassium methacrylate sulfonate, lithium styrene sulfonate, etc.); and low-molecular-weight antistatic agents such as R-SO3X (where R represents an alkyl group, an aryl group, or an aromatic group having an alkyl group, and X represents a metal ion (e.g., Li, Na, K, etc.), an ammonium ion, an amine ion, or a phosphate ester ion) or dimers thereof. However, the antistatic agent is not limited to the above compounds as long as it has a sulfonate group with excellent heat resistance and has the function of exhibiting antistatic properties. In order to efficiently exhibit antistatic properties, it is more preferable to use a low-molecular-weight antistatic agent.

[0065] Examples of alkyl sulfonates include sodium pentane sulfonate, sodium octanesulfonate, lithium octanesulfonate, potassium octanesulfonate, and sodium tetradecyl sulfonate.

[0066] Examples of aryl sulfonates include sodium benzyl sulfonate, sodium toluyl sulfonate, and sodium naphthyl sulfonate. Examples of aromatic sulfonates having an alkyl group include metal salts of alkyl (carbon number: 8 to 20) benzenesulfonates (e.g., Li, K, and Na salts), such as sodium dodecylbenzenesulfonate, sodium alkylnaphthalenesulfonate, and sodium alkylphenyl ether disulfonate.

[0067] Furthermore, as the polymeric antistatic agent made of a polymer of an unsaturated monomer having a sulfonate group, it is preferable to use a styrene resin containing a sulfonate group component in the molecule, such as polystyrene sulfonate.

[0068] A distinctive feature of this polymeric antistatic agent is the high hydrophilicity of its sulfonic acid component. Examples of styrene-based resins containing a sulfonate group moiety within the molecule include homopolymers of sodium, potassium, lithium, ammonium, or phosphonium salts of polystyrene sulfonic acid, and copolymers of acrylic monomers such as acrylates or methacrylates with styrene sulfonic acid monomers. For example, it is preferable to use a styrene-based resin containing a sulfonate group moiety within the molecule, such as polystyrene sulfonate. The weight-average molecular weight of the polystyrene sulfonate salt is 1,000 to 150,000, preferably 10,000 to 70,000. A molecular weight less than 1,000 makes it difficult to achieve water resistance in the coating film, while a molecular weight greater than 150,000 makes it difficult to uniformly mix with the copolymer polyester.

[0069] The blending amount of the antistatic agent relative to the resin component is preferably 2 to 9% by mass, more preferably 3 to 8% by mass. An antistatic agent blending amount of less than 1% by mass is undesirable because the antistatic properties deteriorate. Conversely, an antistatic agent blending amount exceeding 10% by mass is undesirable because the antistatic property improvement effect saturates and the antistatic agent contaminates rolls and the like in the film manufacturing and processing steps.

[0070] Since the wax agent and antistatic agent tend to segregate on the film surface, their blending ratio affects antistatic properties, slipperiness, and abrasion resistance. When the total blending amount of the wax agent and antistatic agent is 100% by mass, the upper limit of the blending amount of the wax agent is preferably 80% by mass, more preferably 70% by mass, and particularly preferably 60% by mass. By setting the blending amount of the antistatic agent to 80% by mass or less, the slipperiness and abrasion resistance of the wax agent can be exhibited. When the total blending amount of the wax agent and antistatic agent is 100% by mass, the lower limit of the blending amount of the antistatic agent is preferably 10% by mass, more preferably 20% by mass, particularly preferably 30% by mass, and most preferably 40% by mass. Setting the blending amount of the antistatic agent to 10% by mass or more is preferable because it can improve antistatic performance.

[0071] In a more preferred embodiment of the present invention, the resin composition layer contains 0.1 to 10% by mass of a silicone and / or fluorine-based surfactant. Examples of silicone surfactants include dimethyl silicone, aminosilane, acrylic silane, vinylbenzyl silane, vinylbenzylaminosilane, glycidyl silane, mercaptosilane, dimethylsilane, polydimethylsiloxane, polyalkoxysiloxane, hydrogen-modified siloxane, vinyl-modified siloxane, acetate-modified siloxane, amino-modified siloxane, carboxyl-modified siloxane, halogen-modified siloxane, epoxy-modified siloxane, methacryloxy-modified siloxane, mercapto-modified siloxane, fluorine-modified siloxane, alkyl group-modified siloxane, phenyl-modified siloxane, and alkylene oxide-modified siloxane.

[0072] Examples of fluorine-based surfactants include tetrafluoroethylene, perfluoroalkylammonium salts, perfluoroalkylsulfonic acid amides, perfluoroalkyl sodium sulfonates, perfluoroalkyl potassium salts, perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, perfluoroalkyl ethylene oxide adducts, perfluoroalkyltrimethylammonium salts, perfluoroalkylaminosulfonates, perfluoroalkyl phosphates, perfluoroalkyl alkyl compounds, perfluoroalkylalkyl betaines, and perfluoroalkyl halides.

[0073] The amount of the surfactant is more preferably 0.1 to 9% by mass, and even more preferably 0.3 to 8% by mass, because the addition of the surfactant improves the affinity of the resin composition layer to the base film during coating, resulting in a coating film with good appearance.

[0074] It is more preferable to add a crosslinking agent to the resin composition layer to prevent particle shedding. As the crosslinking agent, a blocked isocyanate-based crosslinking agent or an oxazoline-based crosslinking agent is preferable. A trifunctional or higher polyisocyanate, which is a precursor of the blocked isocyanate, can be suitably obtained by introducing an isocyanate monomer. Examples of such a crosslinking agent include biuret compounds, nurate compounds, and adduct compounds obtained by modifying an isocyanate monomer such as an aromatic diisocyanate, an aliphatic diisocyanate, an araliphatic diisocyanate, or an alicyclic diisocyanate having two isocyanate groups. Among these, it is more preferable to use a biuret compound.

[0075] The biuret form is a self-condensation product having a biuret bond formed by the self-condensation of an isocyanate monomer, and examples thereof include the biuret form of hexamethylene diisocyanate.

[0076] The nurate is a trimer of an isocyanate monomer, and examples thereof include a trimer of hexamethylene diisocyanate, a trimer of isophorone diisocyanate, and a trimer of tolylene diisocyanate.

[0077] The adduct refers to a tri- or higher functional isocyanate compound obtained by reacting an isocyanate monomer with a tri- or higher functional low-molecular-weight active hydrogen-containing compound, and examples thereof include a compound obtained by reacting trimethylolpropane with hexamethylene diisocyanate, a compound obtained by reacting trimethylolpropane with tolylene diisocyanate, a compound obtained by reacting trimethylolpropane with xylylene diisocyanate, and a compound obtained by reacting trimethylolpropane with isophorone diisocyanate.

[0078] The resin composition layer may contain known additives such as antioxidants, heat stabilizers, weather stabilizers, and organic lubricants, as long as the effects of the present invention are not impaired.

[0079] In the present invention, it is important to maintain high transparency while imparting lubricity and abrasion resistance. Therefore, when preparing the coating solution, it is a further preferred embodiment to also control the temperature of the raw materials before preparation in order to prevent particle aggregation caused by temperature differences between the materials when they are mixed. It is also further preferred to add each material while constantly stirring the coating solution tank in which the preparation is performed. Furthermore, it is a further preferred embodiment to install a filter before the coating device to remove fine aggregates that were contained in the raw materials before preparation or that were generated by component aggregation during preparation.

[0080] In the present invention, the lamination method of the resin composition layer is not limited, but a preferred embodiment is to form it by a so-called in-line coating method, in which the resin composition layer is laminated on an unstretched film or a uniaxially stretched film in the polyester film manufacturing process. The in-line coating method improves the adhesion and adhesion durability between the base film and the resin composition layer. It is also economically advantageous.

[0081] The resin composition layer can be formed by a commonly used method such as gravure coating, kiss coating, dip coating, spray coating, curtain coating, air knife coating, blade coating, or reverse roll coating.

[0082] In the present invention, it is important to maintain high transparency while imparting lubricity and abrasion resistance. To achieve this, it is important to minimize the aggregation of particles in the coating solution that forms the resin composition layer. For example, a decrease in the liquid temperature of the coating solution increases the aggregation of the particles. On the other hand, an increase in the liquid temperature of the coating solution deteriorates the wettability, so one preferred embodiment is to strictly control the liquid temperature within ±1°C. By adopting such an embodiment, the high quality of the laminated polyester film of the present invention can be stably maintained.

[0083] The thickness of the resin composition layer is not particularly limited, but in the present invention, the final thickness after drying is preferably 0.01 to 0.2 μm, more preferably 0.015 to 0.16 μm, and even more preferably 0.02 to 0.12 μm. If the thickness is 0.01 μm or more, the effect of improving slip properties and abrasion resistance will be enhanced, while if it is 0.2 μm or less, transparency will decrease, which is not preferred.

[0084] In the present invention, when the resin composition layer is laminated, slip properties and abrasion resistance are imparted to the laminated polyester film, so that it is not necessary to incorporate particles into the main layer film from the viewpoint of transparency.

[0085] The phrase "there is no need to include particles in the main layer film" means that particles are not intentionally included, not that the resulting film contains no particles at all. This is because even if particles are not intentionally included in the film, contaminants from foreign substances or dirt adhering to the raw resin or the production line or equipment during the film manufacturing process may peel off and be mixed into the film. For example, in the case of inorganic particles, the resulting film is considered to be substantially free of particles if the content of inorganic elements quantified by fluorescent X-ray analysis is 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit.

[0086] Therefore, in order to make the haze of the laminated film 1.0% or less, a preferred embodiment of the present invention is a laminated structure in which the biaxially oriented polyester film of the main layer of the polyester film support does not substantially contain particles, and particles are contained only in the resin composition layer laminated on the side opposite to the main layer film on which the resist layer is laminated to the support.

[0087] Therefore, in the preferred embodiment described above, it is not necessary to form a functionality-imparting layer for the purpose of imparting slipperiness, etc., on the surface of the main layer film on which the resist layer is laminated. Not taking such measures is recommended because the effects of the present invention can be more significantly exhibited, but methods such as incorporating particles in the film that will be the main layer of the support and laminating a functionality-imparting layer on the surface on which the resist layer is formed are also not excluded, as long as they do not impair the effects of the present invention.

[0088] Regarding scratches on the film surface, in addition to taking measures to prevent scratches occurring during the processing steps described above, sufficient consideration must also be given to the occurrence of scratches during the manufacturing process of the film that will become the main layer. For example, since a large surface roughness of a roll such as an applicator roll in the coating step can lead to scratches, a preferred embodiment is to set the surface roughness of such rolls to 0.2 S or less. In addition, in order to prevent the accumulation of scratch-causing factors such as deposits, adhesions, and foreign matter on the roll surface, a method of installing roll cleaners at the preheating entrance and cooling roll in the longitudinal stretching step is also one preferred embodiment.

[0089] There is also a method for making the cleanliness in the film production process Class 1,000 or less (1,000 or less particles of 0.5 μm or more per cubic foot of volume), and it is a preferred embodiment to use Class 100 or less clean air around the rolls, and also to use Class 100 or less clean air for the air cooling device for cooling the opposite roll surface in the casting process.

[0090] Another preferred embodiment is to individually and precisely control the speed of the rolls through which the film passes during the film manufacturing process, thereby minimizing the speed difference between the film and the rolls and taking measures to prevent scratches due to friction.

[0091] Another example is a method of cleaning the roll before film production by scraping off defects on the roll with an abrasive. Another example is a method of providing a static eliminator so that the film's charge is kept at ±1500 V or less throughout the entire process to prevent the film from attracting dust and other particles due to static electricity, which can lead to defects. The process from casting the film that will become the main layer of the support to the tenter (described below) is a process where scratches are most likely to occur, and it is therefore preferable to lay out this section compactly and limit the transit time to 5 minutes or less, as this can contribute to suppressing the occurrence of defects.

[0092] 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 methods used in the present invention will be described below.

[0093] The effectiveness of the present invention will be explained below with reference to examples, but the present invention is not limited to these. The physical properties in the following examples were evaluated using the following methods.

[0094] (1) D50 and D90 of particles were measured using a laser diffraction particle size distribution analyzer SALD-7500 nano (Shimadzu Corporation). Prior to measurement, particles were weighed out using ion-exchanged water as a solvent to a concentration equivalent to a 0.2% by mass slurry, stirred for 10 minutes in a mixer (e.g., a National MXV253 kitchen mixer), cooled to room temperature, and then measured using a high-concentration measurement unit. The refractive index of the inorganic particle with the highest mass percentage used was retrieved from the database built into the analyzer, and the particle size was calculated. The 50% volume particle size (D50) and 90% volume particle size (D90) were determined from the particle size distribution measurement results, and D90 / D50 was calculated.

[0095] (2) Resin Composition Layer Thickness The cross section of the film was cut into ultrathin sections, and the sections were stained with RuO4, OsO4, or a combination of both. The sections were observed and photographed using a TEM (transmission electron microscope). The thickness of the resin composition layer was measured from the photographs of the cross section of the film. The resin composition layer thickness was calculated as the average value of 30 sections within the measurement field of view.

[0096] (3) Air Release Index: Measurements were performed in accordance with JIS P 8155:2010, "Paper and Paperboard - Smoothness Testing Method - Oken Method." The Oken-type smoothness tester used was a device manufactured by Kumagai Riki Kogyo Co., Ltd. (Product Number No. 2040-C). While the JIS stipulates a pressure of 98.1 ± 1.0 kPa for the test specimen, applying this pressure to the film directly proved difficult to reproduce the air release characteristics during film roll winding. After extensive investigation, the authors confirmed that applying a pressure of 48 kPa ± 1.0 kPa to the test specimen and a measurement time of 150 seconds accurately reproduced the air release characteristics during film roll winding. The water column value (mmH2O) obtained from the measurement was used as the air release index.

[0097] (4) Static Friction Coefficient: Measured in accordance with JIS K 7125. However, the load cell and the sample were directly connected without using a spring, the mass of the sliding piece was 4.4 kgf, and the test speed was 200 mm / min. Three measurements were taken for each sample, and the average value was used as the static friction coefficient.

[0098] (5) Amount of coarse particles with a minimum diameter of 3 μm or more A 6 cm x 6 cm sample was taken from the laminated polyester film, and for each sample, a scanning white light interference microscope (device: Hitachi High-Tech Science Corporation's "VertScan" (registered trademark) VS1540) was used to measure the surface opposite the surface on which the resist layer of the laminated polyester film was laminated, with a measurement area of ​​936 μm x 702 μm and 36 fields of view using a 10x objective lens. The sample was set on a stage so that the measurement Y axis was in the longitudinal direction of the sample film (the direction in which the film was wound). In addition, for samples where the longitudinal direction was unknown, the measurement was performed so that the measurement Y axis was in any one direction of the sample film, then rotated 120 degrees, and then rotated 120 degrees again, and the average of each measurement result was used as the number of protrusions on the sample. The sample film to be measured was sandwiched between two metal frames containing rubber packing, so that the film inside the frames was kept taut (without sagging or curling of the sample) and the sample surface was measured.

[0099] The obtained microscope images were subjected to image processing using the surface analysis software VS-Viewer Version 10.0.3.0 built into the microscope under the following conditions to determine the number of protrusions of each height.

[0100] (Image processing conditions) Image processing was performed in the following order: Interpolation processing: complete interpolation Filter processing: Gaussian (cutoff 100) Surface correction: fourth order Furthermore, particle analysis processing was performed under the following conditions, and the number of particles displayed on the "Particle analysis" screen detected at a height threshold of 25 nm (height threshold setting value: 0.025 μm) was used as the amount of coarse particles with a minimum diameter of 3 μm or more.

[0101] (Particle Analysis Conditions) Protrusion analysis processing was carried out under the following conditions.

[0102] Analysis type: Projection analysis Image correction: None Processing Height threshold: 0.025 μm Reference height: Zero plane (average plane) The same procedure was performed for all 36 measured fields, and the total number of particles with a minimum diameter of 3 μm or more was calculated. 2 ) to obtain the number of large particles of 3 μm or more (pieces / mm ２ ) is required.

[0103] (6) Antistatic Properties (Surface Resistivity) The film was cut into a size of 5 cm x 10 cm and seasoned for 24 hours under environmental conditions of a temperature of 23°C and a humidity of 65% RH. The antistatic properties of the surface on which the resin composition layer of the film was laminated were then measured using a surface resistivity meter (manufactured by Mitsubishi Petrochemical Co., Ltd.) under an applied voltage of 500 V, a temperature of 23°C, and a humidity of 65% RH. The surface resistivity (Ω / □) was measured and expressed in logarithm (log(Ω / □)). Five randomly selected samples were subjected to the measurement, and the average of the five measured values ​​was calculated.

[0104] (7) Abrasion Resistance (Abrasion Resistance Index) Using a Gakushin-type friction fastness tester (manufactured by Yamaguchi Scientific Industry Co., Ltd.), friction was applied to the resin laminate surface of a sample having a width of 3 cm and a length of 20 cm under the conditions of a load of 500 gf and 40 reciprocating motions. Aluminum foil was used as the test object, and the abrasion resistance of the resin composition layer was evaluated on a three-point scale by observing the aluminum foil surface after the friction load.

[0105] ⊚: No transfer of particles to the aluminum foil was observed.

[0106] ◯: Slight transfer of particles onto the aluminum foil is observed.

[0107] ×: Many particles were transferred to the aluminum foil.

[0108] (8) Film Roll Slippage A sample film was wound into a roll of 1000 m, and the obtained film roll was observed. The film roll was evaluated as ◯ when no slippage occurred, Δ when slight slippage occurred, and × when significant slippage occurred.

[0109] (9) Haze: Measured using a turbidity meter (manufactured by Nippon Denshoku Co., Ltd., NDH2000) in accordance with JIS K 7136-2000 "Method for determining haze of plastics - transparent materials."

[0110] Preparation of aqueous dispersion (C-1WD) of blocked isocyanate crosslinking agent (C-1) To a flask equipped with a stirrer, thermometer, and reflux condenser, 125.2 parts by mass of a polyisocyanate compound having a biuret structure made from hexamethylene diisocyanate (Duranate 24A-100, manufactured by Asahi Kasei Chemicals, NCO concentration 23.1%), 50.0 parts by mass of dipropylene glycol dimethyl ether, and 68.8 parts by mass of 3,5-dimethylpyrazole were added, and the mixture was stirred at 70°C under a nitrogen atmosphere for 2 hours. The infrared spectrum of the reaction solution was then measured, and it was confirmed that the absorption of the isocyanate group had disappeared. Next, after cooling to room temperature, 6 parts by mass of polyethylene glycol (n = 12) monolaurate was added, and the mixture was stirred for 2000 min. －１ Water was added while stirring and mixing at 50°C. The concentration was adjusted with water to prepare an aqueous dispersion (C-1WD) of the blocked isocyanate crosslinking agent (C-1) having a solids content of 30.0% by mass.

[0111] (Example 1) (1) Preparation of Coating Solution A coating solution was prepared by mixing the following coating agent with a mixed solvent of water and isopropanol. Polyester water dispersion 8.00 parts by mass (Vylonal MD1200, manufactured by Toyobo Co., Ltd., solid content 30% by mass) Particles (a) 1.00 parts by mass (Snowtex OL, manufactured by Nissan Chemical Co., Ltd., colloidal silica with an average particle size of 0.045 μm, solid content 20% by mass) Particles (b) 1.50 parts by mass (acrylic particles with D50 of 0.57 μm and D90 / D50 of 1.3, solid content 2% by mass) Surfactant 0.50 parts by mass (silicone-based, solid content 10% by mass) Wax agent 0.80 parts by mass (Hitec E9015, manufactured by Toho Chemical Co., Ltd., solid content 20% by mass) Antistatic agent 0.80 parts by mass (alkyl sulfonate TB214, solid content 16.7%

[0112] (2) Production of Laminated Polyester Film As a raw polymer for the film, PET resin pellets having an intrinsic viscosity of 0.62 dl / g (solvent: phenol / tetrachloroethane = 60 / 40) and containing substantially no particles were dried at 135°C for 6 hours under a reduced pressure of 133 Pa. Thereafter, the pellets were fed into an extruder and melt-extruded into a sheet at about 280°C, followed by rapid cooling and solidification on a rotating cooled metal roll maintained at a surface temperature of 20°C, thereby obtaining an unstretched PET sheet.

[0113] This unstretched PET sheet was heated to 100° C. using a group of heated rolls and an infrared heater, and then stretched 3.5 times in the longitudinal direction using a group of rolls with different peripheral speeds to obtain a uniaxially stretched PET film.

[0114] Next, the coating solution, which had been left to stand at room temperature for 5 hours or more, was applied to one side of a PET film by roll coating, and then the film was stretched 4.0 times in the width direction at 120°C using a tenter. With the length of the film in the width direction fixed, the film was heated at 230°C for 5 seconds, and then subjected to a 3% width direction relaxation treatment at 100°C for 10 seconds to obtain a laminated polyester film with a thickness of 16 μm. The evaluation results of this film are shown in Table 1. The coating amount after final drying (after biaxial stretching) was 0.05 g / m ２ The thickness of the functional layer after drying was adjusted to 50 nm.

[0115] (Example 2) A laminated polyester film was obtained in the same manner as in Example 1, except that the particles (b) were changed to polystyrene particles (solid content concentration 2%) having a D50 of 0.70 μm and a D90 / D50 of 1.3, and the amount of particles (b) added was changed to 1.25 parts by mass.

[0116] (Example 3) A laminated polyester film was obtained in the same manner as in Example 1, except that the particles (b) were changed to acrylic particles (solid content concentration 2%) having a D50 of 0.73 μm and a D90 / D50 of 1.2, and the amount of particles (b) added was changed to 0.75 parts by mass.

[0117] Example 4 A laminated polyester film was obtained in the same manner as in Example 1, except that the following coating agent was mixed into a mixed solvent of water and isopropanol. Polyester water dispersion 8.00 parts by mass (Vylonal MD1200, manufactured by Toyobo Co., Ltd., solid content 30% by mass) Crosslinker C-1WD 0.80 parts by mass (solid content 30% by mass) Particles (a) 1.00 parts by mass (Snowtex OL, manufactured by Nissan Chemical Co., Ltd., colloidal silica with an average particle size of 0.045 μm, solid content 20% by mass) Particles (b) 1.50 parts by mass (acrylic particles with D50 of 0.57 μm and D90 / D50 of 1.3, solid content 2% by mass) Surfactant 0.50 parts by mass (silicone-based, solid content 10% by mass) Wax agent 0.80 parts by mass (Hitec E9015, manufactured by Toho Chemical Co., Ltd., solid content 20% by mass) Antistatic agent 0.80 parts by mass (alkyl sulfonate TB214, solid content 16.7% by mass)

[0118] Example 5 A laminated polyester film was obtained in the same manner as in Example 1, except that the particles (b) were changed to polystyrene particles (solid content concentration: 2%) having a D50 of 0.31 μm and a D90 / D50 ratio of 1.5.

[0119] (Example 6) A laminated polyester film was obtained in the same manner as in Example 1, except that the particles (b) were changed to silica particles (solid content concentration 2%) having a D50 of 0.80 μm and a D90 / D50 of 2.8, and the amount of particles (b) added was changed to 0.75 parts by mass.

[0120] Comparative Example 1 A laminated polyester film was obtained in the same manner as in Example 1, except that the particles (b) were changed to silica particles (solid content concentration: 2%) having a D50 of 0.28 μm and a D90 / D50 of 1.7.

[0121] (Comparative Example 2) A laminated polyester film was obtained in the same manner as in Example 1, except that the particles (b) were changed to silica particles (solid content concentration 2%) having a D50 of 0.93 μm and a D90 / D50 of 3.2, and the amount of particles (b) added was changed to 0.75 parts by mass.

[0122] (Comparative Example 3) A laminated polyester film was obtained in the same manner as in Example 1, except that the particles (b) were changed to silica particles (solid content concentration 2%) having a D50 of 1.46 μm and a D90 / D50 of 3.8, and the amount of particles (b) added was changed to 0.75 parts by mass.

[0123] (Comparative Example 4) A laminated polyester film was obtained in the same manner as in Example 1, except that the particles (b) were changed to silica particles (solid content concentration 2%) having a D50 of 2.36 μm and a D90 / D50 of 2.2, and the amount of particles (b) added was changed to 0.75 parts by mass.

[0124] Table 1 summarizes the evaluation results for each example and comparative example.

[0125]

[0126] The present invention showed favorable results in all of the following: air release index, static friction coefficient, amount of coarse particles (number of coarse protrusions) with a minimum diameter of 3 μm or more, antistatic properties, abrasion resistance, and film winding slippage. That is, the present invention is suitable as a support for ultrafine line photoresist films.

[0127] Furthermore, photoresist films using the polyester film for ultrafine line photoresists of the present invention as a support exhibit excellent resolution of the photoresist layer, excellent pattern formability on the surface and edges, and excellent adhesion of the photoresist layer.Furthermore, the polyester film for ultrafine line photoresists of the present invention has excellent handling properties and durability, such as blocking and abrasion resistance, when used as a support to produce photoresist films, and is therefore suitable for processing such as lamination, making it useful for industrial use.

[0128] On the other hand, the air release index was outside the range of the present invention, and the film experienced winding slippage in Comparative Example 1. In Comparative Examples 2 and 3, the number of coarse particles of 3 μm or more was outside the range of the present invention, and the abrasion resistance did not satisfy the required characteristics.

[0129] In Comparative Example 4, the number of coarse particles of 3 μm or more was outside the range of the present invention, and the abrasion resistance did not satisfy the required characteristics. In addition, the surface was uneven, and the film was not suitable for producing a photoresist for ultrafine lines.

[0130] The polyester film for ultrafine line photoresists of the present invention has excellent properties such as transparency, slipperiness, antistatic properties, and abrasion resistance, making it suitable for use as a support for ultrafine line photoresists. Photoresist films using the polyester film for ultrafine line photoresists of the present invention as a support also exhibit excellent photoresist layer resolution, surface and edge pattern formability, and adhesion to the photoresist layer. Furthermore, when the polyester film for ultrafine line photoresists of the present invention is used as a support, it exhibits excellent handling and durability, such as blocking resistance and abrasion resistance, during the production of photoresist films, making it suitable for use in applications such as lamination and exhibiting excellent processability. Therefore, the polyester film of the present invention is particularly suitable as a support for ultrafine line photoresists. Furthermore, the technical concept of the present invention can also be applied to other industrial films, such as base films for optical functional films that require high transparency. Therefore, the present invention will make a significant contribution to industry.

Claims

1. A polyester film having a functional layer on at least one side thereof, the air release index (mmH2O) of the side having the functional layer is 493 mmH2O or less, and 2 The laminated polyester film has 250 or less large objects having a minimum diameter of 3 μm or more per unit area.

2. The laminated polyester film according to claim 1, which has a haze of 1.0% or less.

3. A laminated polyester film as described in claim 1, in which the logarithm (log(Ω / □)) of the surface resistivity (Ω / □) of at least one side of the laminated polyester film measured under an environment of a temperature of 23°C and a humidity of 65% RH is 13 or less.

4. The laminated polyester film according to claim 1, wherein the functional layer contains particles, the particles have a D50 of 1 μm or less, and the D90 / D50 of the particles is 3 or less.

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