Biaxially oriented polyester film

Abstract

To provide a biaxially oriented polyester film which suppresses scraping of a coating layer after being wound as a roll while having excellent resist characteristics for next-generation fine wiring by providing a highly smooth surface having protrusions and a controlled surface elastic modulus on one surface of a film and a coating layer having controlled surface properties on the opposite side.SOLUTION: There is provided a biaxially oriented polyester film having a surface (A surface) satisfying the following (1) in which a coating layer provided on the opposite side to the A surface satisfies the following (2) and (3). (1) When the number of protrusions having a height of 1 nm or more and less than 10 nm measured by AFM (Atomic Force Microscope) is defined as N1-10nmA (pieces / 25 μm2) on the A surface, N1-10nmA is 100 or more and 1000 or less. (2) The thickness of the coating layer is 10 nm or more and 200 nm or less. (3) The coating layer contains 0.5 mass% or more and 10 mass% or less of particles having an average primary particle diameter of 3 nm or more and 300 nm or less based on the entire coating layer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a biaxially oriented polyester film having surfaces with specific properties on both sides of the film. [Background technology]

[0002] Due to its excellent processability, polyester resin is used in a wide range of industrial fields. Furthermore, products made from these polyester resins in the form of films (polyester films) play an important role in today's life, including industrial applications, optical products, packaging, and magnetic recording tapes. In recent years, electronic information devices have become smaller and more highly integrated, and consequently, the wiring in these devices has also become finer. To fabricate the fine wiring in these electronic information devices, a transparent film is used as a support, and a photocurable resin layer (resist layer) is applied to the surface. This film is then attached to a substrate to which a thin copper film is laminated, and the copper wiring shape is drawn using photoresist technology on the film. After the film is peeled off, a dry film resist method is often used. Next-generation products require extremely fine processing with wiring widths of 2 to 5 μm. Generally, polyester films are formed during the manufacturing process and then wound into rolls. At this time, if the film surface is too smooth, the films will stick together, worsening the winding performance of the film. Therefore, a method is known in which particles are added to the film to roughen the film surface to a certain extent (forming protrusions on the film surface) in order to ensure the winding performance of the film. By reducing the amount of added particles or by reducing the diameter of the added particles, the optical properties of the film that contribute to resist wiring can be improved. In particular, by applying a coating layer of a thin film containing particles to the film surface using a coating method, it is possible to achieve both the optical properties and the winding performance of the film. For example, Patent Document 1 discloses a technology that controls excellent optical properties by applying a coating layer containing particles of a specific particle size on top of a particle-containing film. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-63341 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, it has been found that with films containing particles like those described in Patent Document 1, surface protrusions originating from the surface particles cause friction between the film's roll winding process, slitting process, and post-processing, leading to abrasion of the coating layer and detachment of particles contained in the coating layer, resulting in a deterioration of optical properties over time.

[0005] The present invention aims to provide a polyester film in which abrasion and particle shedding of the coating layer are suppressed by forming fine protrusions of controlled height on the film surface to create a highly smooth surface, and by controlling the surface modulus of the surface having protrusions and the surface properties of the coating layer. [Means for solving the problem]

[0006] To solve the above problems, the present invention has the following configuration. That is, [I] A biaxially oriented polyester film having a surface (Side A) that satisfies (1) below, and a coating layer provided opposite to Side A that satisfies (2) and (3) below. (1) The number of protrusions with a height of 1 nm or more and less than 10 nm measured on surface A by AFM (Atomic Force Microscope) is N 1-10nm A(pcs / 25μm 2 If we consider N 1-10nm A must be between 100 and 1000. (2) The thickness of the coating layer is 10 nm or more and 200 nm or less. (3) The coating layer contains 0.5% by mass or more and 10% by mass or less of particles with an average primary particle diameter of 3 nm or more and 300 nm or less, relative to the entire coating layer. [II] When the number of protrusions with a height of 50 nm or more that can be measured on the A surface with an optical interference microscope is N 50nm (per mm 2 ), the biaxially oriented polyester film according to [I], where N 50nm A is 50 or less. [III] In the measurement of the surface elastic modulus using AFM on the A surface, when the maximum elastic modulus of the protrusions with a height of 10 nm or more on the A surface is F MAX (GPa), and the average elastic modulus in the range of 1 nm or more and less than 10 nm in height is F AVE (GPa), the biaxially oriented polyester film according to [I] or [II], where F MAX / F AVE is 50 or less. [IV] When the layer constituting the A surface is the P1 layer, the main component of the P1 layer is a polyester resin, and the intrinsic viscosity IV P1 (dl / g) of the polyester resin is 0.45 or more and 0.55 or less. The biaxially oriented polyester film according to any one of [I] to [III]. [V] When the surface of the coating layer is the B surface, and the surface free energy of the B surface is E B (mN / m), and the surface free energy of the A surface is E A (mN / m), the absolute value |E A - E B | (mN / m) of the difference in surface free energy between both sides of the film is 5 or more. The biaxially oriented polyester film according to any one of [I] to [IV]. [VI] The biaxially oriented polyester film according to [V], where the difference in surface free energy E A - E B (mN / m) between both sides of the film is 5 or more. [VII] The biaxially oriented polyester film according to [V], where the difference in surface free energy E A - E B (mN / m) between both sides of the film is -5 or less. [VIII] The biaxially oriented polyester film according to any one of [I] to [VII], which is used as a base film for a dry film resist.

Advantages of the Invention

[0007] This invention provides a biaxially oriented polyester film that offers excellent resist properties for next-generation fine wiring while suppressing abrasion of the coating layer and particle shedding after being wound into a roll. This is achieved by having a highly smooth surface with protrusions and controlled surface modulus on one side of the film, and a coating layer with controlled surface properties on the opposite side. [Brief explanation of the drawing]

[0008] [Figure 1] This is a conceptual diagram representing the protrusions on surface A as measured by AFM and scanning white light interference microscopy. [Figure 2] Diagram of the two-layer structure of the biaxially oriented polyester film of the present invention [Figure 3] Three-layer structure diagram of a polyester film having the coating layer of the present invention [Modes for carrying out the invention]

[0009] The present invention will be described in detail below.

[0010] This invention relates to a biaxially oriented polyester film. A biaxially oriented polyester film having a surface (Side A) that satisfies (1) below, and a coating layer provided opposite to Side A that satisfies (2) and (3) below. (1) The number of protrusions with a height of 1 nm or more and less than 10 nm measured by AFM on surface A is N 1-10nm (pcs / 25μm 2 If we consider N 1-10nm The value must be between 100 and 1000. (2) The thickness of the coating layer is 10 nm or more and 200 nm or less. (3) The coating layer contains 0.5% by mass or more and 10% by mass or less of particles with an average primary particle diameter of 3 nm or more and 300 nm or less, relative to the entire coating layer.

[0011] The biaxially oriented polyester film of the present invention preferably has a two-layer laminated structure of P1 layer / P2 layer, having a polyester resin layer (P1 layer) having the A side and a coating layer (P2 layer) having the opposite side (B side) to the A side, and preferably has a three-layer laminated structure of P1 layer / P3 layer / P2 layer, having an intermediate layer (P3) between the P1 layer and the coating layer which does not contain particles.

[0012] (Surface with protrusions: Surface A) In the present invention, surface A has protrusions, and the number of protrusions with a height of 1 nm or more and less than 10 nm obtained by AFM (Atomic Force Microscope) measurement according to the method described later is N 1-10nm A(pcs / 25μm 2 If we consider N 1-10nm The value is between 100 and 1000. When the biaxially oriented polyester film of the present invention is used as a base film for dry film resist, N 1-10nm A represents the number of fine protrusions formed on the surface of surface A, and is a value that affects the slipperiness of surface A and the resist characteristics for fine wiring when a resist layer is applied to surface A and exposure processing is performed from the side opposite to surface A. It also affects the winding shape of the roll and the scratching of surface A when a biaxially oriented polyester film is manufactured and wound into a film roll. N on surface A 1-10nm A(pcs / 25μm 2 When the N on surface A becomes 100 or more, the contact area with the coated layer surface (surface B) on the opposite side of surface A is reduced during roll winding, thereby reducing friction between the surfaces and improving the winding appearance of the film roll. 1-10nm A(pcs / 25μm 2 By setting the N on side A to 1000 or less, the friction on both sides of the film is excessively reduced, and the occurrence of film roll misalignment can be suppressed. 1-10nm A(pcs / 25μm 2 A more preferable range for this is 250 or higher.

[0013] In the present invention, the number of protrusions N on surface A with a height of 50 nm or more, obtained by scanning white light interference microscopy measurement described later, is... 50nm A (pieces / mm 2 ) is preferably 50 or less. 50nm A (pieces / mm 2 The number of protrusions on surface A that damage the coating layer during film roll winding is a value that reflects the number of protrusions present on surface A that cause scraping of the coating layer and the generation of foreign matter when friction occurs with surface B, and also induces particle detachment by collision with protrusions containing particles on surface B. The number of protrusions on surface A with a height of 50 nm or more in this invention is a value measured by the measurement method described later, based on ISO 25178, which is obtained by software attached to a scanning white light interference microscope. The number of protrusions with a height of 50 nm or more N 50nm A (pieces / mm 2 By setting the number of protrusions N of height 50 nm or more on surface A, damage to the coating layer can be suppressed, and when used as a process film for dry film resist, it is possible to suppress the decrease in the yield of resist wiring formation due to foreign matter contamination caused by the scraping of the coating layer. 50nm A (pieces / mm 2 A more preferable range for this is 15 or less.

[0014] (Polyester resin layer constituting surface A: P1 layer) In the biaxially oriented polyester film of the present invention, it is preferable that the A surface is composed of a layer (P1 layer) mainly composed of polyester resin.

[0015] (Polyester resin) In this invention, a biaxially oriented polyester film refers to a film whose main component is polyester resin. Here, the main component refers to a component that is present in more than 50% by mass of 100% by mass of the total components of the film.

[0016] Furthermore, the polyester resin referred to in this invention is obtained by polycondensation of a dicarboxylic acid component and a diol component. In this specification, a component refers to the smallest unit that can be obtained by hydrolysis of polyester.

[0017] Examples of dicarboxylic acid components constituting such polyesters include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, and 4,4'-diphenyletherdicarboxylic acid, or their ester derivatives.

[0018] Furthermore, examples of diol components that make up such polyesters include aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol; alicyclic diols such as cyclohexanedimethanol and spiroglycol; and compounds in which multiple of the above-mentioned diols are linked together.

[0019] In the present invention, the polyester resins used are preferably polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene-2,6-naphthalenedicarboxylate (PEN), and polyesters copolymerized with isophthalic acid or naphthalenedicarboxylic acid in part of the dicarboxylic acid component of PET, and polyesters copolymerized with cyclohexanedimethanol, spiroglycol, or diethylene glycol in part of the diol component of PET, with polyethylene terephthalate being particularly preferred.

[0020] In the biaxially oriented polyester film of the present invention, the polyester film is preferably biaxially oriented. Biaxial orientation improves the mechanical strength of the film, making it less prone to wrinkling and improving windability. Furthermore, by applying uniform stretching stress during the stretching process, the surface smoothness can be made uniform throughout the entire film. Biaxial orientation, as used here, refers to a pattern that shows biaxial orientation when measured by wide-angle X-ray diffraction. Polyester films can generally be obtained by stretching an unstretched thermoplastic resin sheet in the longitudinal and width directions of the sheet, and then performing heat treatment to complete the crystal orientation. Detailed film formation conditions will be described later.

[0021] In the A surface of the P1 layer of the present invention, the number of protrusions with a height of 1 nm or more and less than 10 nm obtained by the AFM (Atomic Force Microscope) measurement is N 1-10nm A(pcs / 25μm 2 Methods for achieving the above range include, for example, a method of transferring the shape to the surface using a mold, such as nanoimprinting, and a method of performing plasma surface treatment by atmospheric pressure glow discharge on an unstretched sheet, followed by biaxial stretching. From the viewpoint of inline film formation suitability and the number of fine protrusions formed, it is more preferable to perform plasma treatment by atmospheric pressure glow discharge followed by biaxial stretching.

[0022] Plasma surface treatment by atmospheric pressure glow discharge can be performed on the unstretched film after extrusion or on the stretched film during the polyester film manufacturing process. However, from the viewpoint of imparting smoothness and slipperiness to surface A, it is most preferable to perform the plasma surface treatment by atmospheric pressure glow discharge on the unstretched film. This is because the amorphous polyester portion is scraped off by the plasma surface treatment by atmospheric pressure glow discharge, and in the subsequent stretching and film formation process, the crystalline polyester portion remaining on the surface grows as convex parts, forming fine protrusions on the surface.

[0023] The atmospheric pressure referred to here is in the range of 700 Torr to 780 Torr. In atmospheric pressure glow discharge processing, the film to be processed is guided between opposing electrodes and an earth roll, a plasma-excitable gas is introduced into the apparatus, and a high-frequency voltage is applied between the electrodes to plasma-excite the gas and cause a glow discharge between the electrodes. As a result, the surface of the film is finely processed (ashed) and protrusions are formed.

[0024] A plasma-excitable gas is a gas that can be plasma-excited under the conditions described above. Examples of plasma-excitable gases include noble gases such as argon, helium, neon, krypton, and xenon, nitrogen, carbon dioxide, oxygen, or chlorofluorocarbons such as tetrafluoromethane, and mixtures thereof. Furthermore, a single plasma-excitable gas may be used alone, or two or more gases may be combined in any mixing ratio.

[0025] The frequency of the high-frequency voltage used in plasma processing is preferably in the range of 1 kHz to 100 kHz. Furthermore, the discharge treatment intensity (E value) determined by the following method is 50 to 1000 W·min / m². 2 Processing within this range is preferable from the viewpoint of protrusion formation, and more preferably 150-800 W·min / m 2 The discharge treatment intensity (E value) is 50 W·min / m². 2 As a result, protrusions can be sufficiently formed, and the discharge treatment intensity (E value) is 1000 W·min / m 2 The following conditions can be met to prevent excessive damage to the polyester film and reduce the generation of surface foreign matter.

[0026] <How to determine the discharge treatment intensity (E value)> E = Vp × Ip / (S × Wt) E: E value (W·min / m) 2 ) Vp: Applied voltage (V) Ip: Applied current (A) S: Processing speed (m / min) Wt: Processing width (m) Generally, when ashing the surface of polyester films, especially films with amorphous and crystalline regions such as PET and PEN, using atmospheric pressure glow discharge treatment, the ashing starts from the softer amorphous regions. By subdividing the crystalline and amorphous regions, it is possible to form finer protrusions by atmospheric pressure glow discharge treatment, and the aforementioned N 1-10nm A can be increased.

[0027] In the A surface of the P1 layer of the present invention, the number of protrusions with a height of 1 nm or more and less than 10 nm obtained by the AFM (Atomic Force Microscope) measurement is N 1-10nm A(pcs / 25μm 2 Methods for achieving the above range include controlling the particle size and amount of particles contained in the P1 layer, or forming resin domains by alloying a polyester resin or other resin having a different skeleton from the main polyester resin, thereby creating high protrusions due to the difference in stretchability with the polyester film.

[0028] Regarding the added particles, either inorganic or organic particles may be used, and two or more types of particles may be used in combination. Examples of inorganic particles include calcium carbonate, magnesium carbonate, zinc carbonate, titanium dioxide, zinc oxide, cerium oxide, magnesium oxide, barium sulfate, zinc sulfide, calcium phosphate, alumina (α-alumina, β-alumina, γ-alumina, δ-alumina), mica, titanium mica, zeolite, talc, clay, kaolin, lithium fluoride, calcium fluoride, montmorillonite, zirconia, wet silica, dry silica, and colloidal silica. Examples of organic particles include organic particles composed of acrylic resins, styrene resins, silicone resins, polyimide resins, and core-shell type organic particles.

[0029] The average particle diameter of the aforementioned particles is determined by the number of protrusions N with a height of 50 nm or more, while providing slipperiness to the A surface. 50nm From the viewpoint of controlling A within a desirable range, it is preferable that the average particle diameter is 10 nm or more and 100 nm or less.

[0030] Furthermore, the amount of particles contained in the P1 layer of the present invention is preferably 0.5% by mass or less, from the viewpoint of preventing the excessive formation of protrusions with a height of 50 nm or more due to particle aggregation. More preferably 0.2% by mass or less, and even more preferably 0.1% by mass or less.

[0031] The resin alloyed with the P1 layer is not particularly limited as long as it can be melt-extruded simultaneously with the polyester resin. For example, multiple types of polyester resins and copolymers as exemplified above can be used, or other resins such as the polyetherimide resin described in Japanese Patent Application Publication No. 2021-55077 can be used.

[0032] In the biaxially oriented polyester film of the present invention, the intrinsic viscosity (IV) of the P1 layer is set to IV P1 If (dl / g), then IV P1 (dl / g) is preferably 0.45 or more and 0.55 or less. IV is a number that reflects the length of the molecular chain; shorter molecular chains tend to facilitate orientation and crystallization of polyester molecules during stretching and heat treatment, promoting protrusion formation in the stretching and film-forming process and improving slipperiness. Furthermore, as crystallization progresses after film formation, even when particles described later are present, the surface modulus can be made more uniform, thereby suppressing abrasion of the coated layer. IV P1 By setting the pressure to 0.45 dl / g or higher, it is possible to suppress the difficulty in film formation caused by the generation of air bubbles due to insufficient pressure during melt extrusion of polyester resin.

[0033] In the polyester film of the present invention, the maximum elastic modulus of the protrusions on surface A that are 10 nm or taller, obtained by AFM (Atomic Force Microscope) measurement described later, is F MAX (GPa), the average modulus of elasticity at a height of less than 10 nm is F AVE If we consider (GPa), then F MAX / F AVE It is preferable that it is 50 or less. MAX / F AVEThis value represents the ratio of the surface modulus of the protrusions with a height of 10 nm or more formed by the aforementioned particle addition or resin alloy to the surface modulus of the main component polyester resin, and reflects the uniformity of the surface modulus of surface A.

[0034] Said F MAX / F AVE By setting this to 50 or less, the difference between the elastic modulus of the high protrusions on surface A and the polyester resin of the base surface is reduced, causing uniform elastic deformation across the entire surface when the coating layer having surface A and surface B comes into contact. This suppresses the coating layer from being scraped off by catching on localized high-elasticity areas. MAX / F AVE A more preferred range is 30 or less, and even more preferably 10 or less. If no protrusions of 10 nm or more in height exist on surface A, the maximum elastic modulus of the protrusions in the region of 1 nm or more and less than 10 nm in height, obtained by AFM (Atomic Force Microscope) measurement, is F MAX This will be explained in more detail later.

[0035] (Coated layer: P2 layer) In the biaxially oriented polyester film of the present invention, when the coating layer formed opposite to the A surface is designated as the P2 layer, it is preferable that the coating composition be composed of at least one functional additive (A) selected from antistatic agents and release agents, and at least one resin or compound (B) selected from polyester resin, urethane resin, epoxy resin, melamine resin, oxazoline compound, carbodiimide compound, acrylic resin, and silicone resin, and particulate components (C).

[0036] <Functional Additive (A)> In the present invention, the coating composition of the coating layer (P2 layer) preferably contains at least one functional additive (A) selected from antistatic agents and release agents. This is not only to control the surface free energy of the coating layer surface (B surface) described later, but also because, when used as a base film for dry film resist, a release agent improves smoothness with the film transport and process rolls, and an antistatic agent suppresses the adhesion of foreign matter to the film surface when the film roll is unwound.

[0037] (Release agent) Examples of release agents that can be used in the present invention include long-chain alkyl group-containing resins, olefin resins, fluorine compounds, and wax-based compounds. Among these, long-chain alkyl group-containing resins are preferred because they can provide good release properties.

[0038] The long-chain alkyl group-containing compound may be a commercially available product. Specifically, it may be the "Ashiorezin" (registered trademark) series of long-chain alkyl compounds manufactured by Ashio Sangyo Co., Ltd., the "Piroyl" series of long-chain alkyl compounds manufactured by Lion Specialty Chemicals Co., Ltd., or the "Rezem" series of aqueous dispersions of long-chain alkyl compounds manufactured by Chukyo Oil & Fat Co., Ltd. The release agent (A) preferably has an alkyl group having 12 or more carbon atoms, and more preferably has an alkyl group having 16 or more carbon atoms. By increasing the number of carbon atoms of the alkyl group to 12 or more, the hydrophobicity is increased, and sufficient release performance can be achieved as a release agent (A). If the number of carbon atoms of the alkyl group is less than 12, the release performance may be insufficient. There is no particular upper limit to the number of carbon atoms of the alkyl group, but it is preferable if it is 25 or less because it is easier to manufacture.

[0039] The resin having an alkyl group with 12 or more carbon atoms is more preferably a resin having a side chain of an alkyl group with 12 or more carbon atoms in a polymethylene main chain. Since the main chain is polymethylene, the number of hydrophilic groups in the entire resin is reduced, which can improve the release effect of the release agent (A).

[0040] Furthermore, the presence or absence of C12 alkyl groups can be evaluated from the laminated film, for example, by using the intensity of the alkyl group in the signal obtained by TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry). In this case, by using a cutting method by ion sputtering in combination, it is possible to perform continuous measurements in the depth direction, and the distribution state of alkyl group-containing compounds can also be evaluated.

[0041] (Antistatic agent) The antistatic agents that can be used in the present invention may be polystyrene sulfonic acid copolymers, ion-conductive types having tertiary amino groups or quaternary ammonium groups in the polymer backbone, or electron-conductive types such as polythiophene compounds, polyaniline compounds, or antimony-doped tin oxide compounds. Among these, a combination of a polythiophene compound and polystyrene sulfonic acid, which is an acidic polymer in a free acid state, is readily available, inexpensive, and easy to use.

[0042] As polythiophene-based conductive compounds, for example, compounds having a structure in which the 3rd and 4th positions of the thiophene ring are substituted can be used. Furthermore, compounds in which oxygen atoms are bonded to the carbon atoms at the 3rd and 4th positions of the thiophene ring can be suitably used. Compounds in which hydrogen atoms or carbon atoms are directly bonded to the carbon atoms may not readily allow for aqueous coating. The above compounds can be produced by methods disclosed in, for example, Japanese Patent Application Publication No. 2000-6324, European Patent No. 602713, and U.S. Patent No. 5,391,472, but other methods may also be used.

[0043] For example, by using an alkali metal salt of 3,4-dihydroxythiophene-2,5-dicarboxyester as a starting material to obtain 3,4-ethylenedioxythiophene, and then reacting it with potassium peroxodisulfate, iron sulfate, and the previously obtained 3,4-ethylenedioxythiophene in an aqueous solution of polystyrene sulfonic acid, a composition can be obtained in which a polythiophene such as poly(3,4-ethylenedioxythiophene) is complexed with an acidic polymer such as polystyrene sulfonic acid.

[0044] Furthermore, an aqueous paint composition containing poly-3,4-ethylenedioxythiophene and polystyrene sulfonic acid, such as the one sold by HCStarck GmbH (Germany) as "Baytron" P, can be used.

[0045] On the other hand, examples of acidic polymers in a free acid state include polymeric carboxylic acids, polymeric sulfonic acids, and polyvinyl sulfonic acids. Examples of polymeric carboxylic acids include polyacrylic acid, polymethacrylic acid, and polymaleic acid. Examples of polymeric sulfonic acids include polystyrene sulfonic acid, with polystyrene sulfonic acid being particularly preferred in terms of antistatic properties. The free acid may also take the form of a salt in which a portion has been neutralized. It can also be used in a copolymerized form with other copolymerizable monomers, such as acrylic acid esters, methacrylic acid esters, and styrene. The molecular weight of the polymeric carboxylic acid and polymeric sulfonic acid is not particularly limited, but in terms of the stability and antistatic properties of the coating agent, its weight-average molecular weight is preferably 1,000 to 1,000,000, and more preferably 5,000 to 150,000. Furthermore, it may contain alkali salts such as lithium salts and sodium salts, or ammonium salts, to the extent that it does not impair the properties of the invention. Even in the case of a salt in which the polyanion has been neutralized, it is thought to act as a topant. This is because polystyrene sulfonic acid and its ammonium salt, which function as very strong acids, shift the equilibrium to the acidic side as the equilibrium reaction proceeds after neutralization.

[0046] <Resin or compound (B)> Examples of resins or compounds (B) that can be used in the P2 layer of the present invention include polyester resins, epoxy resins, melamine resins, oxazoline compounds, carbodiimide compounds, isocyanate compounds, acrylic resins, and silicone resins.

[0047] The polyester resin that can be used as the resin or compound (B) is preferably one having ester bonds in the main chain or side chains, and obtained by polycondensation of a dicarboxylic acid and a diol.

[0048] Aromatic, aliphatic, and alicyclic dicarboxylic acids can be used as raw materials for polyester resins. Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 2,5-dimethylterephthalic acid, 1,4-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2-bisphenoxyethane-p,p'-dicarboxylic acid, and phenylindanedicarboxylic acid. Examples of aliphatic and alicyclic dicarboxylic acids include succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedionic acid, dimer acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and their ester-forming derivatives.

[0049] Diol components used as raw materials for polyester resins include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl- 1,6-Hexanediol, 1,2-Cyclohexanedimethanol, 1,3-Cyclohexanedimethanol, 1,4-Cyclohexanedimethanol, 2,2,4,4-Tetramethyl-1,3-Cyclobutanediol, 4,4'-Thiodiphenol, Bisphenol A, 4,4'-Methylenediphenol, 4,4'-(2-Norbornylidene)diphenol, 4,4'-Dihydroxybiphenol, o-, m-, and p-Dihydroxybenzene, 4,4'-Isopropylidenephenol, 4,4'-Isopropylidenebinediol, Cyclopentane-1,2-Diol, Cyclohexane-1,2'-Diol, Cyclohexane-1,2-Diol, Cyclohexane-1,4-Diol, etc. can be used.

[0050] Furthermore, as the polyester resin, it is also possible to use modified polyester copolymers, such as block copolymers or graft copolymers modified with acrylic, urethane, epoxy, etc.

[0051] Examples of epoxy resins that can be used as resin or compound (B) include sorbitol polyglycidyl ether-based crosslinking agents, polyglycerol polyglycidyl ether-based crosslinking agents, diglycerol polyglycidyl ether-based crosslinking agents, and polyethylene glycol diglycidyl ether-based crosslinking agents. Commercially available epoxy resins may also be used, such as the epoxy compounds "Denacol" (registered trademark) EX-611, EX-614, EX-614B, EX-512, EX-521, EX-421, EX-313, EX-810, EX-830, EX-850 etc. manufactured by Nagase Chemtec Corporation, diepoxy / polyepoxy compounds (SR-EG, SR-8EG, SR-GLG etc.) manufactured by Sakamoto Pharmaceutical Co., Ltd., and the epoxy crosslinking agent "EPICLON" (registered trademark) EM-85-75W or CR-5L manufactured by Dainippon Ink & Industries, Ltd., among which water-soluble ones are preferred.

[0052] Examples of melamine resins that can be used as resin or compound (B) include melamine, methylolated melamine derivatives obtained by condensing melamine with formaldehyde, compounds partially or completely etherified by reacting methylolated melamine with a lower alcohol, and mixtures thereof. The melamine resin may be a monomer or a condensate consisting of two or more polymers, or a mixture thereof. Examples of lower alcohols used for etherification include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, and isobutanol. Functional groups include imino groups, methylol groups, or alkoxymethyl groups such as methoxymethyl groups and butoxymethyl groups in one molecule, and include imino-type methylated melamine resins, methylol-type melamine resins, methylol-type methylated melamine resins, and fully alkyl-type methylated melamine resins. Among these, methylolated melamine resins are most preferably used.

[0053] Furthermore, the oxazoline compound that can be used as a resin or compound (B) is preferably one that has an oxazoline group as a functional group in the compound, and is composed of an oxazoline group-containing copolymer obtained by copolymerizing at least one monomer containing an oxazoline group with at least one other monomer.

[0054] Examples of monomers containing an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. One or more of these can be used as a mixture. Among these, 2-isopropenyl-2-oxazoline is preferred because it is readily available industrially.

[0055] In oxazoline compounds, at least one other monomer used with a monomer containing an oxazoline group is a monomer copolymerizable with the oxazoline group-containing monomer, such as acrylic acid esters or methacrylic acid esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, and 2-ethylhexyl methacrylate; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, and maleic acid; acrylonitrile; and methacrylonitrile. Any unsaturated nitriles, unsaturated amides such as acrylamide, methacrylamide, N-methylolacrylamide, and N-methylolmethacrylamide, vinyl esters such as vinyl acetate and vinyl propionate, vinyl ethers such as methyl vinyl ether and ethyl vinyl ether, olefins such as ethylene and propylene, halogen-containing α,β-unsaturated monomers such as vinyl chloride, vinylidene chloride, and vinyl fluoride, and α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene can be used, and one or more of these can be used as mixtures.

[0056] Furthermore, carbodiimide compounds that can be used as resins or compound (B) are compounds that have one or more carbodiimide groups or cyanamide groups in a tautomer relationship therewith as functional groups within the molecule. Specific examples of such carbodiimide compounds include dicyclohexylmethanecarbodiimide, dicyclohexylcarbodiimide, tetramethylxylylenecarbodiimide, and urea-modified carbodiimide, and these can be used individually or as a mixture of two or more.

[0057] The coating layer of the biaxially oriented polyester film of the present invention may contain an isocyanate compound as the resin or compound (B). Examples of isocyanate compounds include tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, metaxylylene diisocyanate, hexamethylene-1,6-diisocyanate, 1,6-diisocyanate hexane, adducts of tolylene diisocyanate and hexanetriol, adducts of tolylene diisocyanate and trimethylolpropane, polyol-modified diphenylmethane-4,4'-diisocyanate, carbodiimide-modified diphenylmethane-4,4'-diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, 3,3'-vitrylene-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, and metaphenylene diisocyanate.

[0058] Furthermore, since isocyanate groups readily react with water, in terms of the pot life of the coating agent, blocked isocyanate compounds, in which the isocyanate groups are masked with a blocking agent, can be suitably used. In this case, when heat is applied during the drying process after coating the polyester film with the coating composition, the blocking agent dissociates, exposing the isocyanate groups, and as a result, the crosslinking reaction proceeds.

[0059] The acrylic resin that can be used as the resin or compound (B) is not particularly limited, but one composed of alkyl methacrylate and / or alkyl acrylate is preferred.

[0060] Preferably, alkyl methacrylates and / or alkyl acrylates include methacrylic acid, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, acrylic acid, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, maleic acid, itaconic acid, acrylamide, N-methylolacrylamide, and diacetoneacrylamide. One or more of these can be used.

[0061] Furthermore, the urethane resin that can be used as the resin or compound (B) is preferably a resin obtained by reacting a polyhydroxy compound and a polyisocyanate compound by known polymerization methods for urethane resins, such as emulsion polymerization or suspension polymerization.

[0062] Examples of polyhydroxy compounds include polyethylene glycol, polypropylene glycol, polyethylene-propylene glycol, polytetramethylene glycol, hexamethylene glycol, tetramethylene glycol, 1,5-pentanediol, diethylene glycol, triethylene glycol, polycaptolactone, polyhexamethylene adipate, polyhexamethylene sebacate, polytetramethylene adipate, polytetramethylene sebacate, trimethylolpropane, trimethylolethane, pentaerythritol, polycarbonate diol, and glycerin.

[0063] Examples of polyisocyanate compounds that can be used include hexamethylene diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate, adducts of tolylene diisocyanate and trimethylenepropane, and adducts of hexamethylene diisocyanate and trimethylolethane.

[0064] The silicone resin that can be used as resin or compound (B) may be a type mainly composed of a curable silicone resin or a type mainly composed of a modified silicone resin. As for the curable silicone resin, any curing reaction type can be used, such as addition type, condensation type, UV curing type, electron beam curing type, solvent-free type, or a type combining heat and UV curing. As for the modified silicone resin, it may be a modified silicone resin obtained by graft polymerization with organic resins such as epoxy resins, urethane resins, or alkyl resins.

[0065] In the coating composition forming the coating layer of the biaxially oriented polyester film of the present invention, it is preferable to include at least one selected from melamine resin, isocyanate compound, oxazoline compound, and carbodiimide compound to suppress abrasion of the coating layer during the film formation and processing steps, thereby improving the strength of the coating layer by constructing a crosslinked structure within the coating layer.

[0066] <Particle component (C)> The coating composition forming the coating layer of the biaxially oriented polyester film of the present invention can improve the slipperiness of the biaxially oriented polyester film by including a particulate component (C) in addition to a functional additive (A) and a resin or compound (B).

[0067] In the present invention, suitable particulate components (C) include oxide fine particles of elements located on and to the left of the diagonal line connecting boron (B), silicon (Si), arsenic (As), tellurium (Te), and astatine (At).

[0068] Examples of such particulate components (C) include SiO2, TiO2, ZrO2, ZnO, CeO2, SnO2, Sb2O5, indium-doped tin oxide (ITO), phosphorus-doped tin oxide (PTO), Y2O3, La2O3, and Al2O3.

[0069] These particulate components (C) may be used individually or in combination of two or more. From the viewpoint of dispersion stability and refractive index, SiO2, TiO2, and ZrO2 are particularly preferred.

[0070] Here, we will explain the number-average particle diameter of the particle component (C). The number-average particle diameter here refers to the particle diameter determined by a transmission electron microscope (TEM). The magnification was set to 500,000x, and the number-average particle diameter was calculated by measuring the outer diameter of 10 particles present in the image, for a total of 100 particles across 10 fields of view. Here, the outer diameter represents the maximum diameter of the particle (i.e., the major axis of the particle, indicating the longest diameter within the particle), and similarly, it represents the maximum diameter of the particle even if the particle has an internal cavity.

[0071] The particle component (C) used in the coating layer (P2 layer) of the biaxially oriented polyester film of the present invention preferably has an average primary particle diameter of 3 nm or more and 300 nm or less. More preferably, it is 30 nm or more and 200 nm or less, and most preferably 50 nm or more and 180 nm or less. By making the average primary particle diameter of the particle component (C) 3 nm or more, protrusions are formed on the surface of the coating layer, improving the ease of sliding with the process metal roll on the B side and improving the ease of sliding on both sides of the film. Furthermore, the aggregation of particles and localized scattering within the coating layer can prevent the induction of abrasion of the coating layer. On the other hand, by making the average primary particle diameter of the particle component (C) 300 nm or less, the deterioration of the resist characteristics for fine wiring can be kept to a minimum even when used as a process film for dry film resists.

[0072] Methods for producing the particulate component (C) include, for example, the following methods (i) to (iv) when surface-treating the particulate component (C) with acrylic resin. In this invention, surface treatment refers to a process in which acrylic resin is adsorbed and attached to all or part of the surface of the particulate component (C). (i) A method of adding a mixture of particulate component (C) and acrylic resin, which has been pre-mixed, to a solvent and then dispersing it. (ii) A method of dispersing particulate component (C) and acrylic resin in order in a solvent. (iii) A method of pre-dispersing particulate component (C) and acrylic resin in a solvent and mixing the resulting dispersion. (iv) A method in which particulate component (C) is dispersed in a solvent, and then an acrylic resin is added to the resulting dispersion.

[0073] The desired effect can be achieved by any of these methods, and the resin used for surface treatment is not limited to acrylic resin; the methods can also be applied to the aforementioned resins.

[0074] Furthermore, dissolvers, high-speed mixers, homomixers, mixers, ball mills, roll mills, sand mills, paint shakers, SC mills, annular mills, pin mills, etc., can be used as dispersion devices.

[0075] Furthermore, as a dispersion method, the above-mentioned apparatus is used to rotate the rotating shaft at a peripheral speed of 5 to 15 m / s. The rotation time is 5 to 10 hours.

[0076] Furthermore, using dispersion beads such as glass beads during dispersion is preferable in terms of improving dispersibility. The bead diameter is preferably 0.05 to 0.5 mm, more preferably 0.08 to 0.5 mm, and particularly preferably 0.08 to 0.2 mm. Mixing and stirring can be done by shaking the container by hand, using a magnetic stirrer or stirring blade, or by ultrasonic irradiation or vibration dispersion.

[0077] The content of particulate component (C) in the coating layer is preferably 0.5% by mass or more and 10% by mass or less relative to the entire coating layer. More preferably, it is 1% by mass or more and 7% by mass or less. By setting the content of particulate component (C) to 0.5% by mass or more and 10% by mass or less relative to the entire resin layer, surface protrusions derived from particles can be formed on the B surface without impairing the film-forming properties of the coating layer, thereby improving the slipperiness of both the process metal roll and the film on the B surface. As a result, it is possible to sufficiently achieve both suppression of abrasion and particle shedding of the coating layer and slipperiness.

[0078] The thickness of the P2 layer in the present invention is T P2 When T is set to (μm) P2 It is preferable that the value of T is between 0.01 and 0.20. P2 By setting (μm) to 0.01 or greater, the wettability of the coated layer surface, as described later, can be controlled, and the shedding of the contained particulate component (C) can be prevented. P2 By setting the (μm) to 0.20 or less, it is possible to sufficiently form protrusions due to the contained particles, and when the biaxially oriented polyester film of the present invention is used as a process film for dry film resist, it is possible to suppress the deterioration of the resist properties for fine wiring that originate from the particles contained in the coating layer.

[0079] In the present invention, when using the aforementioned coating composition, the method for constructing the P2 layer can be either an off-coat method, in which coating is performed after the polyester film is manufactured, or an in-line coat method, in which coating and drying are performed during the polyester film manufacturing process. However, if the layer in contact with the P2 layer in the biaxially oriented polyester film does not contain particles, it is preferable to use the in-line coat method from the viewpoint of providing smoothness during film formation.

[0080] (Coated layer surface: Side B) Preferably, the wettability of the surface of the coated layer (P2 layer) of the biaxially oriented polyester film of the present invention is different from that of surface A. Specifically, the surface free energy of surface A is E A (mN / m) and the surface free energy of surface B is EB When (mN / m), |E| is the absolute value of the difference in surface free energy between surface A and surface B. A -E B |(mN / m) is preferably 5 or greater. The above |E A -E B When |(mN / m) is 5 or more, the slipperiness tends to improve by suppressing adhesion between both sides of the biaxially oriented polyester film. The difference in surface free energy between side A and side B |E A -E B A more preferred range for |(mN / m) is 10 or more, and even more preferably 20 or more.

[0081] The difference in surface free energy between side A and side B in the biaxially oriented polyester film of the present invention is |E A -E B If |(mN / m) is 5 or greater, it is acceptable for the surface free energy of either face to be large, E A -E B (mN / m) is preferably 5 or more or -5 or less, more preferably 10 or more or -10 or less, and even more preferably 20 or more or -20 or less.

[0082] (Middle layer: P3 layer) The biaxially oriented polyester film of the present invention may have a P3 layer between the P1 layer and the coating layer (P2 layer). For example, if the P1 layer contains particles, it is preferable to have a three-layer structure of P1 / P3 / P2, with a particle-free P3 layer between the P1 and P2 layers, from the viewpoint of improving the optical properties of the polyester film. Furthermore, if the intrinsic viscosity of the polyester resin constituting the P1 layer is controlled to the above-mentioned preferred range, it is preferable to have a three-layer structure of P1 / P3 / P2, where the P3 layer is made of a polyester resin with an intrinsic viscosity (IV) of 0.55 or higher, from the viewpoint of improving the overall mechanical properties of the polyester film.

[0083] (Biaxially oriented polyester film) In the biaxially oriented polyester film of the present invention, the polyester film is preferably biaxially oriented. Biaxial orientation improves the mechanical strength of the film, making it less prone to wrinkling and improving windability. Furthermore, by applying uniform stretching stress during the stretching process, the surface smoothness can be made uniform throughout the entire film. Biaxial orientation, as used here, refers to a pattern that shows biaxial orientation when measured by wide-angle X-ray diffraction. Polyester films can generally be obtained by stretching an unstretched thermoplastic resin sheet in the longitudinal and width directions of the sheet, and then applying heat treatment to complete the crystal orientation. More details will be described later.

[0084] In the biaxially oriented polyester film of the present invention, the intrinsic viscosity (IV) of the entire polyester film is preferably 0.50 dl / g or higher, and more preferably 0.55 dl / g or higher. By setting IV to 0.50 dl / g or higher, it is possible to suppress crystallization that progresses due to the short polyester molecular chains, which would cause frequent breakage during the stretching process and make film formation difficult.

[0085] As described above, the biaxially oriented polyester film of the present invention may have a two-layer configuration (P1 layer / P2 layer) where the A-side and the B-side are the outermost surfaces of each other, or it may have a configuration of at least three layers (P1 layer / P3 layer / P2 layer) with an intermediate layer P3 layer between the P1 layer and the P2 layer. There are no particular limitations on the method for laminating the P1 layer and P3 layer, which are made of polyester resin. Methods such as the co-extrusion method described later, a method in which other resin layer raw materials are introduced into an extruder during the film formation process and melt-extruded to laminate while being extruded from a die (melt lamination method), and a method of laminating the films after film formation with an adhesive layer in between can be used. Among these, the co-extrusion method, which can form protrusions by the aforementioned process and laminate simultaneously, is preferred.

[0086] From the viewpoint of film roll winding performance, the static friction coefficient (μs) of both sides of the biaxially oriented polyester film of the present invention is preferably 0.4 or more and 1.3 or less. Setting the static friction coefficient (μs) of both sides of the film to 0.4 or more suppresses excessive slippage between the films during roll winding, thereby preventing roll winding misalignment. Setting the static friction coefficient (μs) of both sides of the film to 1.3 or less suppresses wrinkle formation and deterioration of the winding appearance due to the films adhering tightly to each other during roll winding. A more preferable range for the static friction coefficient is 0.5 or more and 1.1 or less.

[0087] When the total thickness of the biaxially oriented polyester film of the present invention is T (μm), it is preferable that T is between 10 and 100. By setting the total thickness T (μm) to 10 or more, it is possible to suppress film tearing during the coating process of the resist layer, the high-temperature lamination process, and the heat treatment process when the biaxially oriented polyester film is used in the manufacturing process and as a process film for dry film resists. Furthermore, by setting the total thickness T (μm) to 100 or less, it is possible to prevent the film rigidity of the biaxially oriented polyester film from becoming excessively high, thereby improving processability. A more preferable range for the total thickness T (μm) is between 15 and 100.

[0088] (Method for manufacturing biaxially oriented polyester film) Next, the method for producing the biaxially oriented polyester film of the present invention will be described with examples, but the present invention is not to be interpreted as being limited only to what can be obtained by such examples.

[0089] A conventional polymerization method can be used to obtain the polyester film used in the present invention. For example, it can be obtained by transesterifying or esterifying a dicarboxylic acid component such as terephthalic acid or its ester-forming derivative with a diol component such as ethylene glycol or its ester-forming derivative using a known method, followed by a melt polymerization reaction. Alternatively, if necessary, the polyester obtained by the melt polymerization reaction may be subjected to a solid-phase polymerization reaction at a temperature below the melting point of the polyester.

[0090] The polyester film of the present invention can be obtained by conventionally known manufacturing methods. Specifically, the polyester film of the present invention can be produced by a method in which, if necessary, a dried raw material is heated and melted in an extruder and extruded from a die onto a cooled cast drum to form a sheet (melt casting method). As another method, a method can also be used in which the raw material is dissolved in a solvent, the solution is extruded from a die onto a support such as a cast drum or endless belt to form a film, and then the solvent is dried and removed from the film layer to form a sheet (solution casting method).

[0091] When manufacturing a biaxially oriented polyester film with two or more layers by the melt casting method, a suitable method is used in which an extruder is used for each layer constituting the biaxially oriented polyester film, the raw materials for each layer are melted, and these are laminated in a molten state in a confluence device provided between the extruder and the die, then guided to the die, and extruded from the die onto a cast drum to process into a sheet (co-extrusion method). The laminated sheet is then adhered to a cast drum cooled to a surface temperature of 20°C to 60°C by electrostatics and cooled and solidified to produce an unstretched film. By setting the surface temperature of the cast drum to 20°C or higher, the crystalline polyester portion on the surface of the unstretched film can be increased, and the effect of forming fine protrusions after stretching by plasma surface treatment by atmospheric pressure glow discharge can be obtained. Furthermore, by setting the surface temperature of the cast drum to 60°C or lower, adhesion of the unstretched film to the cast drum can be suppressed, and an unstretched film with less thickness unevenness in the film running direction can be obtained. A more preferable range for the surface temperature of the cast drum is 25°C to 55°C.

[0092] Next, the unstretched film obtained here is subjected to a surface treatment such as plasma surface treatment by atmospheric pressure glow discharge. These surface treatments may be performed immediately after obtaining the unstretched film or after stretching in the direction of the film's running (hereinafter sometimes referred to as the longitudinal direction), but in this invention, surface treatment on the unstretched film is preferable from the viewpoint of further promoting the formation of the aforementioned protrusions. Furthermore, the surface to be treated may be either the surface that was in contact with the cast drum (drum surface) or the surface that was not in contact with the cast drum (non-drum surface).

[0093] (Sequential biaxial stretching) Regarding the stretching conditions when biaxially stretching an unstretched film, if the polyester film of the present invention is mainly composed of polyester, it is preferable to guide the unstretched film to a group of rolls heated to 70°C or higher, stretch it in the longitudinal direction (vertical direction, i.e., the direction of film travel), and cool it with a group of rolls set to a temperature of 20°C to 50°C for longitudinal stretching. There is no particular lower limit to the heating roll temperature in longitudinal stretching as long as the stretchability of the sheet is not impaired, but it is preferable to exceed the glass transition temperature of the polyester resin used. Furthermore, the preferred range for the longitudinal stretching ratio is 3 to 5 times. A more preferred range is 3 to 4 times. If the longitudinal stretching ratio is 3 times or higher, orientation crystallization will progress and the film strength can be improved. On the other hand, by setting the stretching ratio to 5 times or lower, it is possible to suppress excessive orientation crystallization of the polyester resin accompanying stretching, which can make the film brittle and cause tearing during film formation.

[0094] An inline coating is performed on a process film (uniaxially oriented film) stretched in the longitudinal direction, applying a coating composition that forms the P2 layer to the side opposite to the A side, and then stretching and drying it in the width direction. Any known coating method can be used for applying the coating composition. Examples include wire bar coating, reverse coating, gravure coating, die coating, blade coating, dip coating, air knife coating, curtain coating, and roller coating.

[0095] Regarding stretching in the direction perpendicular to the longitudinal direction (width direction), it is preferable to guide the film to a tenter while holding both ends with clips, and stretch it by 3 to 5 times its original length in the direction perpendicular to the longitudinal direction (width direction) in an atmosphere heated to a temperature of 70°C to 160°C.

[0096] When forming the P2 coating layer, it is preferable to gradually increase the temperature in accordance with the stretching ratio when stretching in the width direction. This is because as stretching in the width direction progresses, the molecular chain orientation of the polyester resin progresses, and by continuously supplying the amount of heat necessary for stretching, it is possible not only to suppress the occurrence of stretching defects, but also to form a coating layer with a uniform thickness in the width direction in the coating composition coated using the above method. By forming the coating layer with a uniform thickness, the occurrence of locally thicker areas that become starting points for coating layer abrasion and the aggregation of particles contained in the coating layer are suppressed, thereby suppressing particle shedding. As a specific method for gradually increasing the stretching temperature (hereinafter sometimes referred to as gradual temperature increase), it is preferable to divide the stretching temperature in the stretching section within the tenter into at least three sections and increase the stretching temperature in proportion to the stretching ratio.

[0097] Subsequently, it is preferable to heat-treat the stretched film to stabilize its internal orientation structure. The thermal history temperature of the film during heat treatment can be confirmed by the minute endothermic peak (sometimes called Tmeta) temperature that appears just below the melting point temperature, measured by a differential scanning calorimeter (DSC) as described later. When polyester (melting point 255°C) is the main component, it is preferable to set the tenter device temperature so that the maximum temperature inside the tenter is between 200°C and 250°C. When other thermoplastic resins are the main component, it is preferable to set the temperature to below the resin melting point -55°C or below -5°C. Setting the heat treatment temperature to 200°C or higher improves the dimensional stability of the biaxially oriented polyester film and promotes the progress of intermolecular crosslinking reactions when forming the P2 layer, allowing for the formation of a stronger coating layer (P2 layer). Furthermore, setting the heat treatment temperature to 250°C or lower suppresses the occurrence of film tearing due to the melting of the polyester film, enabling productive manufacturing. A more preferable range is between 220°C and 245°C.

[0098] The range of Tmeta, which represents the thermal history temperature experienced by the film during heat treatment, is preferably 190°C to 245°C when polyester resin is the main component, for the reasons mentioned above. A more preferable range is 210°C to 240°C.

[0099] Furthermore, to impart dimensional stability after heat treatment, a relaxation treatment may be performed in the range of 1% to 6%. By performing a relaxation treatment of 1% or more, the dimensional stability of the biaxially oriented polyester film can be improved when used in a high-temperature environment, while by performing a relaxation treatment of 6% or less, an appropriate tension can be continuously applied to the biaxially oriented polyester film, preventing the deterioration of thickness uniformity.

[0100] The stretching ratio should be 3 to 5 times in both the longitudinal and width directions, but the area ratio (stretching ratio in the longitudinal direction × stretching ratio in the width direction) is preferably 9 to 22 times, and more preferably 9 to 20 times. By setting the area ratio to 9 times or more, the molecular orientation of the resulting biaxially oriented polyester film can be promoted and its durability can be improved, and by setting the area ratio to 22 times or less, the occurrence of tearing during stretching can be suppressed.

[0101] [Method for evaluating characteristics] A. Evaluation of the number of protrusions using AFM (Atomic Force Microscope) Number of protrusions with a height of 1 nm or more and less than 10 nm: N 1-10nm A(pcs / 25μm 2 ) A 5 μm square field of view (measurement size: 5 μm × 5 μm, measurement area: 25 μm) can be obtained by the following measurement method. 2The image of the surface (A side) of 1nm is analyzed using the attached analysis software (NanoScope Analysis Version 1.40). After performing only the Flatten process on the obtained Height Sensor image of the film surface as described below, the reference plane of the film surface is automatically determined by setting the Particle Analysis analysis mode as follows. The reference plane is the plane with a height of 0 nm determined under the following Flatten process conditions. From this reference plane, the threshold height of the protrusion height is 1 nm (R) at 25 μm 10nm and the average value of the protrusion density per 2 (value in the Density row, Mean column) is N 10nm (number / 25 μm 2 ). When the average value of the protrusion density per 1-10nm 25 μm at 10 nm (R 2 ) is N N 1-10nm (number / mm 2 ), the value obtained by the following formula is the number of protrusions N 1nm A (number / mm 2 ) with a height of 1 nm or more and less than 10 nm in the measurement image. 10nm (number / mm 2 ) The above analysis is performed on all 20 measurement images for each sample, and the average value is taken as the number of protrusions N 1-10nm A (number / mm 2 ) with a height of 1 nm or more and less than 10 nm on the A side of the sample.

[0102] [AFM Measurement Method] · Equipment: Atomic Force Microscope (AFM) manufactured by Bruker Dimention Icon with ScanAsyst · Cantilever: Silicon nitride probe ScanAsyst Air · Scanning mode: ScanAsyst · Scanning speed: 0.977 Hz​​​​​ • Scanning direction: Scanning is performed in the width direction of the measurement sample prepared using the method described later. • Measurement field of view: 5 μm square • Sample line: 512 ·Peak Force Set Point:0.0195V~0.0205V Feedback Gain: 10-20 LP Deflection BW: 40 kHz ·ScanAsyst Noise Threshold: 0.5nm • Sample preparation: 23°C, 65% RH, stand for 24 hours. AFM measurement environment: 23°C, 65%RH • Method for preparing measurement samples: Double-sided tape was attached to one side of an AFM sample disc (15 mm in diameter), and the AFM sample disc was bonded to the side of the biaxially oriented thermoplastic resin film of the present invention, cut to approximately 15 mm x 13 mm (longitudinal direction x width direction), opposite to the aforementioned surface (measurement surface), to create a measurement sample.

[0103] • Number of sample measurements: Each sample is measured 20 times, with each sample being moved to a different location so that they are at least 5 μm apart from each other.

[0104] • Measurement values: The aforementioned analysis is performed on the 20 images measured, and each value is measured and its average value is treated as the individual values ​​of the sample. [Flattening process] • Flatten Order: 3rd ·Flatten Z Threshholding Direction:No theresholding ·Find Threshold for:the whole image ·Flatten Z Threshold %:0.00 % • Mark Excluded Data: Yes [Particle Analysis Mode Settings] (Detect tab) • Threshold Height: Enter according to each value. Feature Direction: Above ·X Axis:Absolute Number Histogram Bins: 512 ·Histogram Filter Cutoff:0.00 nm • Min Peak to Peak: 1.00 nm Left Peak Cutoff: 0.00000% Right Peak Cutoff: 0.00000% (Modify tab) Beughbirhood Size: 3 • Number of Pixels Off: 1 • Do not perform any Dilate / Erode operations. (Select tab) ·Image Cursor Mode:Particle Select Bound Particles: Yes ·Non-Representative Particles:No ·Height Reference: Relative To Max Peak Number Histogram Bins: 50 When determining the aforementioned values, no specific peaks or areas in the analyzed image are selected. Do not select a specific location in any of the histograms for Diameter, Height, or Area.

[0105] Surface modulus evaluation using B.AFM (Atomic Force Microscope) (i) Maximum modulus F at protrusion height of 10 nm or more MAX The image of the surface (surface A) with a 30 μm square field of view obtained by the following measurement method is analyzed using the attached analysis software (NanoScope Analysis Version 1.40). After applying only the Flattening process described below to the Height Sensor image of the obtained film surface, the location of the protrusion with a maximum protrusion height of 10 nm or more is identified, and the elastic modulus of the location corresponding to the target protrusion is confirmed in the DMT Modulus image using the following procedure. First, the DMT Modulus image is retrieved from Section mode, and a Section image (2D graph, vertical axis: elastic modulus, horizontal axis: scanning measurement position) is displayed using a Horizontal Line passing through the apex of the target protrusion, and numerical data of the 2D graph is obtained. At this time, the aforementioned Flattening process is not performed on the DMT Modulus image. The maximum elastic modulus of the target protruding portion in the Section image is F. MAX We will seek it as follows.

[0106] (ii) Average modulus F in the region less than 10 nm in height AVE Similarly to the previous section (i), the average modulus of elasticity in the region with a height of less than 10 nm in the Height Sensor image of the same Section image is obtained as the average value of the numerical values ​​corresponding to the scanning measurement position, F AVE To obtain.

[0107] (iii) Ratio of surface modulus F MAX / F AVE F on the same scan line, which can be determined in the previous sections (i) and (ii). MAX F AVE By dividing by F MAX / F AVE The following is obtained. A similar analysis was performed on five different sets of DMT Modulus images and Height Sensor images, and the average of the five analysis values ​​was taken as the ratio of the surface modulus of the sample F. MAX / F AVE Let's assume that. • Equipment: Bruker Atomic Force Microscope (AFM) Dimension Icon with ScanAsyst Cantilever: TAP525A • Scanning mode: QNM mode • Scanning speed: 0.977Hz • Scanning direction: Scanning is performed in the width direction of the measurement sample prepared using the same method as in item A above. ·Measurement field of view: 30μm square • Sample line: 512 • Sample preparation: 23°C, 65% RH, stand for 24 hours. AFM measurement environment: 23°C, 65%RH.

[0108] C. Evaluation using a scanning white-light interference microscope (VertScan) A 6cm x 6cm sample is taken from a biaxially oriented polyester film. For each sample, a scanning white-light interference microscope (device: Hitachi High-Tech Science Corporation "VertScan" (registered trademark) VS1540) is used to measure the surface of the biaxially oriented polyester film using a 50x objective lens, with 90 fields of view in a measurement area of ​​113μm x 113μm. The sample set is placed on the stage so that the measurement Y-axis is in the longitudinal direction of the sample film (the direction in which the film is wound). If the longitudinal direction of the sample is unknown, the measurement is taken so that the measurement Y-axis is in any direction of the sample film, then rotated 120 degrees and measured again, and then rotated another 120 degrees and measured again. The average of the measurement results is taken as the number of protrusions on that sample. The sample film to be measured is sandwiched between two metal frames with rubber gaskets so that the film inside the frames is taut (no slack or curl in the sample) and the sample surface is measured.

[0109] The obtained microscope images are processed using the built-in surface analysis software VS-Viewer Version 10.0.3.0 under the following conditions to determine the arithmetic mean surface roughness and the number of protrusions at each height.

[0110] (Image processing conditions) Image processing is performed in the following order. • Interpolation process: Full interpolation • Filtering: Median (3x3 pixels) • Surface correction: 4th order.

[0111] (i) Number of protrusions with a height of 50 nm or more (N 50nm A) Following the above, after observing the surface (surface A) under a microscope and performing image processing, particle analysis processing was performed using the surface analysis software VS-Viewer Version 10.0.3.0 built into the microscope under the following conditions, with a height threshold of 50 nm (R 50nm The number of particles (particles) displayed on the "Particle Analysis" screen, which detects particles at a height threshold of 0.05 μm, is divided by the measurement area (113 μm × 113 μm) to determine the number of protrusions (particles / mm²) with a height of 50 nm or more. 2 )

[0112] (Particle analysis conditions) The protrusion analysis process will be performed under the following conditions. ·Analysis type: sudden analysis Image correction: None ·process Height threshold: 0.05 μm Particle shaping: None Reference height: Zero plane (average plane) • Subject to evaluation Height / Depth: -10000μm ≤ h ≤ 10000μm Maximum diameter: -10000μm ≤ d ≤ 10000μm Volume: V ≥ 0.0000 μm 3 Aspect ratio: r≧0.0000 • Histogram: 50 divisions The same procedure was performed on all 90 fields of view, and the average value was used to determine the number of protrusions N on surface A of the sample that are 50 nm or taller. 50nm A (pieces / mm 2 )

[0113] (Reference height: Zero plane (average plane)) As the "zero plane (average plane)" in the setting of the reference height (height 0 nm) mentioned above, the plane of the "average height (Ave)" that is automatically determined by the following formula in the measurement image (113 μm × 113 μm) obtained by observing the microscope image using the method described above and applying the image processing described above is used.

[0114]

number

[0115] • lx: Range length in the X direction in each measurement image after the aforementioned image processing. ·ly: Y-direction range length in each measurement image after the aforementioned image processing. h(x,y): The height at each image point (x,y) in the measured image after the aforementioned image processing.

[0116] D. Surface free energy (E A , E B ) First, the laminated film is left in an atmosphere at room temperature (23°C) and relative humidity (65%) for 24 hours. Then, under the same atmosphere, the contact angles of four solutions—pure water, ethylene glycol, formamide, and diiodomethane—are measured at five points on the surface side of the resin layer of the laminated film using a DropMaster DM-501 contact angle analyzer manufactured by Kyowa Interface Science Co., Ltd. The average of the three measurements obtained by excluding the maximum and minimum values ​​from the five measurements is taken as the contact angle for each solution.

[0117] Next, using the contact angles of the four types of solutions obtained, the dispersion force component (γ) of the solid surface free energy (γ) proposed by Hata et al. was used. S d ), polar force component (γ S p ), and hydrogen bonding component (γ S h The dispersion force, polar force, hydrogen bonding force, and surface free energy (the sum of the dispersion force and polar force) are calculated by separating the three components and using the geometric mean method based on the extended Fowkes equation (extended Fowkes equation).

[0118] The specific calculation method is shown below. The meaning of each symbol is explained below. γ S L If is the tension at the interface between the solid and the liquid, then equation (2) holds.

[0119] γ S L : Surface free energy of the resin layer and the known solutions listed in Table 1 γ S : Surface free energy of the resin layer γ L Surface free energies of known solutions listed in Table 1 γ S d : Dispersion force component of the surface free energy of the resin layer γ S p : Polar force component of the surface free energy of the resin layer γ S h : Hydrogen bonding force component of the surface free energy of the resin layer γ L d Dispersion force component of the surface free energy of known solutions listed in Table 1 γ L p : Polar force component of the surface free energy of known solutions listed in Table 1 γ L h : Hydrogen bonding force component of surface free energy of known solutions listed in Table 1 γ S L =γ S +γ L -2(γ S d ·γ L d ) 1 / 2 -2(γ S p ·γ L p) 1 / 2 -2(γ S h ·γ L h ) 1 / 2 ... Formula (2).

[0120] Furthermore, the state when a smooth solid surface and a liquid droplet are in contact at a contact angle (θ) can be expressed by the following equation (Young's equation).

[0121] γ S =γ S L +γ L cosθ ... Formula (3).

[0122] Combining equations (2) and (3), we obtain the following equation. (γ S d ·γ L d ) 1 / 2 +(γ S p ·γ L p ) 1 / 2 +(γ S h ·γ L h ) 1 / 2 =γ L (1+cosθ) / 2 ··· Formula (4).

[0123] In practice, the contact angle (θ) of four types of solutions—water, ethylene glycol, formamide, and diiodomethane—and the surface tension of each component (γ) of the known solutions listed in Table 1 are used. L d gamma L p gamma L h Substitute ) into equation (4) and solve the four simultaneous equations. As a result, the surface free energy (γ) of the solid and the dispersion force component (γ) are obtained. S d ), polar force component (γ S p ), and hydrogen bonding component (γ S h ) is calculated.

[0124] E. Film thickness (i) Total thickness The total thickness of the biaxially oriented polyester film was measured using a dial gauge at five arbitrary points with 10 layers of film stacked, in accordance with JIS K7130 (1992) A-2 method. The average value was divided by 10 to obtain the total film thickness T (μm).

[0125] (ii) Lamination thickness (T P1 , T P3 ) A cross-section of a biaxially oriented polyester film is cut using a microtome in a direction parallel to the film width. The cross-section is observed with a scanning electron microscope at a magnification of 5,000 to 20,000 times, and the thickness ratio of each laminated layer is determined. The thickness of each layer is calculated from the determined layering ratio and the total film thickness obtained in item (i) above.

[0126] (iii) Thickness of the coating layer (P2) (T P2 ) A biaxially oriented polyester film is stained with ruthenium tetroxide (RuO4) and / or osmium tetroxide (OsO4). The biaxially oriented polyester film is frozen and cut in the film thickness direction to obtain 10 ultrathin section samples for observation of the resin layer cross-section. Each sample cross-section is observed at 10,000 to 1,000,000x magnification using a TEM (transmission electron microscope: Hitachi H7100FA) to obtain cross-sectional images. The measured thickness of the release resin layer (P1 layer) having the aforementioned surface at these 10 points (10 samples) is averaged to determine the thickness T of the release resin layer. P2 Let it be (μm).

[0127] F. Static friction coefficient (μs) After conditioning the biaxially oriented polyester film of the present invention at 23°C and 65%RH, two rectangular pieces measuring 75mm in width and 100mm in length are cut out as samples, with the film formation line direction being the longitudinal direction. The slip coefficient is measured using a slip coefficient measuring device (model ST-200, manufactured by TechnoNeeds Co., Ltd.) under a 23°C, 65%RH atmosphere. The rectangular sample is set and fixed on the measurement sample stage of the device so that the tension direction of the device is the longitudinal direction of the rectangular sample and the A-side is facing upwards. The other rectangular sample is placed on top of it with the A-side facing upwards and the tension direction being the longitudinal direction, so that the A-side and the opposite side (B-side) are in contact, and the end of the sample is fixed to the U-gauge for load detection of the device. The film is then left to stand, and a 200g weight is placed on top of it, with a 6.5cm x 6.5cm Teflon® resin sheet on the sample contact surface, to ensure close contact between the samples. The static friction coefficient is then measured when the upper film is pulled under the following conditions. Ten measurements are taken, and the average of the six measurements (excluding the top two and bottom two) is taken as the static friction coefficient (μs). Measurement distance: 12mm Measurement speed: 210mm / min.

[0128] G. Polymer Properties (i) Intrinsic viscosity (IV) The sample to be measured (polyester resin (raw material) or the polyester film of the present invention) was dissolved in 100 ml of orthochlorophenol (solution concentration C (weight of sample / volume of solution) = 1.2 g / 100 ml), and the viscosity of the solution at 25°C was measured using an Ostwald viscometer. The viscosity of the solvent was also measured in the same manner. Using the obtained solution viscosity and solvent viscosity, [η] was calculated using the following formula (5), and the obtained value was taken as the intrinsic viscosity (IV) of the entire polyester film. ηsp / C = [η] + K[η] 2 ·C ···(5) (Here, ηsp = (solution viscosity / solvent viscosity) - 1, and K is the Huggins constant (assumed to be 0.343).) If the solution in which the sample was dissolved contained insoluble matter such as inorganic particles, the measurement was performed using the following method. (1-1) Dissolve the sample in 100 mL of orthochlorophenol to prepare a solution with a concentration greater than 1.2 g / 100 mL. Here, the weight of the sample subjected to orthochlorophenol is defined as the weight of the sample. (1-2) Next, the solution containing the insoluble matter is filtered, and the weight of the insoluble matter and the volume of the filtrate after filtration are measured. (1-3) Add orthochlorophenol to the filtered filtrate and adjust the concentration so that (weight of sample (g) - weight of insoluble matter (g)) / (volume of filtered filtrate (mL) + volume of added orthochlorophenol (mL)) is 1.2 g / 100 mL. (For example, when a concentrated solution is prepared with a sample weight of 2.0 g / 100 mL, if the weight of insoluble matter after filtering the solution is 0.2 g and the volume of the filtrate after filtering is 99 mL, then an adjustment should be made by adding 51 mL of orthochlorophenol. ((2.0 g - 0.2 g) / (99 mL + 51 mL) = 1.2 g / 100 mL)) Using the solutions obtained in (1-4) and (1-3), measure the viscosity at 25°C using an Ostwald viscometer. Using the obtained solution viscosity and solvent viscosity, calculate [η] using the above formula (5), and the obtained value is taken as the intrinsic viscosity (IV).

[0129] (ii) Intrinsic viscosity of the P1 layer (IV P1 ) In the biaxially oriented polyester film of the present invention, only the P1 layer portion is scraped off and the intrinsic viscosity of the P1 layer is measured in the same manner as in item (i) above. P1 ) was obtained. (iii) Intrinsic viscosity of the film (IV) F ) The entire layer of the biaxially oriented polyester film of the present invention is prepared in the same manner as in item (i) above, and the intrinsic viscosity of the film (IV F ) was obtained.

[0130] (iv) Amount of terminal carboxyl groups (unit: eq / t, referred to as COOH amount in the table.) The measurement was performed using Maulice's method. (Reference: MJ Maulice, F. Huizinga, Anal. Chem. Acta, 22, 363 (1960)). Specifically, 0.5 g of the sample (polyester (raw material) or polyester film with only the P1 layer separated) is weighed to an accuracy of 0.001 g or less. 50 ml of a solvent mixture of o-cresol / chloroform in a mass ratio of 7 / 3 is added to the sample, and the mixture is heated until the internal temperature reaches 90°C, then heated and stirred for 20 minutes to dissolve. The mixed solvent alone is also heated separately as a blank solution. The solution is cooled to room temperature, and titration is performed using a potentiometric titrator with a 1 / 50 N potassium hydroxide methanol solution. The blank solution of only the mixed solvent is also titrated in the same manner. The value calculated using the following formula was defined as the amount of terminal carboxyl groups in the sample being measured. Amount of terminal carboxyl groups (equivalents / t) = {(V1-V0) × N × f} × 1000 / S Here, V1 is the titration volume in the sample solution (mL), V0 is the titration volume in the blank solution (mL), N is the normality of the titrant (N), f is the titrant factor, and S is the mass of the polyester composition (g).

[0131] H. Evaluation of particle content (i) Average particle diameter of particles contained in the P1 and P2 layers Regarding the biaxially oriented polyester film of the present invention, small pieces were prepared by cutting perpendicular to the surface using a microtome, and the cross-sections of the P1 or P3 layers were observed at 10,000 to 1,000,000x magnification using a TEM (transmission electron microscope: Hitachi, Ltd., model H7100FA) to obtain cross-sectional images. From these cross-sectional images, the particle size distribution of particles present in the P1, P2, or P3 layers was determined using the image analysis software Image-Pro Plus (Nippon Roper Co., Ltd.). Cross-sectional images were selected from different arbitrary measurement fields, and the equivalent circle diameter of 400 or more particles arbitrarily selected from the cross-sectional images was measured, and the number-average particle diameter was obtained from the average value based on the number of particles. If two or more types of particles were contained based on the elemental analysis of the particles below, the equivalent circle diameter of 200 or more particles was measured for each type, and the number-average particle diameter was obtained from the average value of the number-based equivalent circle diameters.

[0132] (ii) Average primary particle diameter of particles contained in the P2 layer In accordance with item (i) above, the analysis of particles in the cross-sectional photograph of the P2 layer was performed as described in item (i). At this time, particles that were aggregated in groups of multiple particles were excluded from the particles to be observed. The average value of the obtained equivalent diameter of the reference circle was taken as the average primary particle diameter of the particles contained in the P2 layer.

[0133] (iii) particle content; The P1 layer of the biaxially oriented polyester film of the present invention was placed in 200 ml of a 1N-KOH methanol solution and heated under reflux to dissolve the polymer. After dissolution, 200 ml of water was added to the solution, and the liquid was centrifuged to allow the particles to settle, and the supernatant was removed. The particles were then washed with water and centrifuged twice. The particles obtained in this way were dried, and the particle content (mass%) in each layer was calculated by weighing them. When organic particles were included in the added particles, a solvent that dissolves the polymer but not the organic particles was selected, the polymer was dissolved without superheating under reflux, and the particles were centrifuged to calculate the particle content (mass%).

[0134] [Method for evaluating application characteristics] I. Winding capability (1) Evaluation of wrinkles The biaxially oriented polyester film of the present invention was fabricated under conditions of a film-forming speed of 100 m / min or more, and 10 consecutive roll windings of 5000 m were performed. The occurrence of winding wrinkles in the 10 resulting film rolls was evaluated as follows.

[0135] A: Out of 10 rolls, 2 or fewer rolls have wrinkles. B: Of the 10 rolls, 3 to 4 rolls have wrinkles or creases. C: Of the 10 rolls, 5 to 6 rolls have wrinkles or creases. D: Of the 10 rolls, 7 or more have wrinkles or creases. In terms of wrinkle resistance, A to C indicates good quality, with A being the best.

[0136] (2) Evaluation of winding misalignment The occurrence of winding misalignment in the 10 film rolls obtained in the previous section (1) was evaluated as follows.

[0137] A: Out of 10 rolls, one or fewer rolls experienced winding misalignment. B: Of the 10 rolls, 2 to 4 rolls exhibited winding misalignment. C: Of the 10 rolls, 5 to 6 rolls exhibited winding misalignment. D: Of the 10 rolls, 7 or more rolls showed winding misalignment. In terms of winding misalignment evaluation, A to C indicate good performance, with A being the best.

[0138] J. Durability evaluation of the coating layer (1) Evaluation of abrasion of the coating layer The biaxially oriented polyester film of the present invention is manufactured under conditions of a film manufacturing speed of 100 m / min or more, and a continuous 1000 m roll is wound onto it. The resulting roll is unwound, and the process of rewinding it onto a new roll is repeated twice. The obtained 1000m film rolls, which had been rewound multiple times, were inspected for scratches on the B-side, and the abrasion of the coating layer was evaluated as follows. A: No scratches were found on the coated surface of the rolled-up roll. B: There are one to three scratches on the surface of the coated layer of the rolled-up roll. C: There are 4 to 9 scratches on the surface of the coated layer of the rolled-up roll.

[0139] D: There are more than 10 scratches on the surface of the coated layer of the rolled-up roll. In terms of the abrasion resistance evaluation of the coating layer, A to C indicate good performance, with A being the best among them.

[0140] (2) Evaluation of particle shedding in the coated layer In accordance with Section I above, a 1000m film roll that had been rewound multiple times was subjected to observation for foreign matter defects of 1μm or larger, and the abrasion of the coated layer was evaluated as follows. A: No foreign matter defects occur in the rewound roll. B: The rolled-up roll had one to three foreign object defects. C: The rolled-up roll has 4 to 9 scratches.

[0141] D: There are more than 10 scratches on the rolled-up section. In evaluating particle shedding from the coated layer, A to C indicate good performance, with A being the best among them. K. Dry film resist suitability evaluation (i) Create resist wiring pattern The photoresist will be evaluated using the segmented reduction exposure method according to the following methods a. to c. a. A 10 μm thick photoresist layer is fabricated by coating a 6-inch Si wafer, which has been mirror-polished on one side, with "PMERN-HC600" negative resist manufactured by Tokyo Ohka Co., Ltd., and rotating it with a large spinner. Next, a preheat treatment is performed for approximately 20 minutes at a temperature of 70°C using a nitrogen-circulating ventilated oven. b. The surface of the polyester film is placed in contact with the resist layer, and the polyester film is laminated onto the photoresist layer using a rubber roller. A reticle patterned with chromium metal is then placed on top of the reticle, and projection exposure is performed on the reticle using an i-line (ultraviolet light with a peak at a wavelength of 365 nm) stepper equipped with a projection lens. c. After peeling the polyester film from the photoresist layer, the photoresist layer is placed in a container with developer solution N-A5 and developed for approximately 1 minute. After that, it is removed from the developer and washed with water for approximately 1 minute. The state of 30 resist wiring patterns with an L / S (μm) (Line and Space) of 5 / 5 μm created after development is observed using a scanning electron microscope (SEM) at a magnification of approximately 800 to 3000.

[0142] (ii) Evaluation of fine wiring resist characteristics Regarding the 30 resist wiring patterns observed in the previous section (i), the number of wiring patterns with a linear gap of 0.5 μm or more on the long side of the upper surface of the wiring pattern is confirmed, and the fine wiring resist characteristics of the film are evaluated as follows. A: Number of missing pieces: 0 B: The number of missing pieces is between 1 and 5. C: The number of missing pieces is between 6 and 10. D: The number of missing pieces exceeds 10. In terms of resist characteristics evaluation, A to C indicate good performance, with A being the best among them.

[0143] L. Extrusion Stability The biaxially oriented polyester film of the present invention was manufactured for 48 hours or more under conditions of a film manufacturing speed of 100 m / min or more, and the extrusion stability was evaluated as follows based on the number of film tears caused by bubbles generated from the die. A: No film tears caused by bubbles occurred during the 48-hour film formation process. B: During the 48-hour film formation process, one instance of film tearing due to bubbles occurred. C: During the 48-hour film formation process, film tears caused by bubbles occurred two to three times. D: During the 48-hour film formation process, film tears caused by bubbles occurred more than four times. In terms of extrusion stability, A through C are good, with A being the best among them. [Examples]

[0144] The present invention will be described below with reference to examples, but the present invention is not necessarily limited to these examples.

[0145] [Production of PET-1] Dimethyl terephthalate (DMT) was added with 1.9 moles of ethylene glycol per 1 mole of DMT and 0.05 parts by weight of magnesium acetate tetrahydrate per 100 parts by weight of DMT, and 0.015 parts by weight of phosphoric acid was added, followed by heating for transesterification. Subsequently, 0.025 parts by weight of antimony trioxide was added, and the temperature was raised by heating, and polycondensation was carried out under a vacuum state to obtain polyester pellets substantially free of particles. The glass transition temperature of the obtained melt-polymerized PET was 81 °C, the melting point was 255 °C, and the intrinsic viscosity was 0.45.

[0146] Thereafter, the obtained polyester pellets were dried at 160 °C for 6 hours for crystallization, and then solid-phase polymerization was carried out at 220 °C, a vacuum degree of 0.3 Torr for 8 hours to obtain solid-phase polymerization PET (PET-1). The glass transition temperature of the obtained solid-phase polymerization PET was 81 °C, the melting point was 255 °C, and the intrinsic viscosity was 0.54.

[0147] [Production of PET-2] In the same manner as in the above [Production of PET-1], solid-phase polymerization PET (PET-2) having a glass transition temperature of 81 °C, a melting point of 255 °C, and an intrinsic viscosity of 0.64 was obtained.

[0148] [Production of PET-3] In the same manner as in the above [Production of PET-1], solid-phase polymerization PET (PET-3) having a glass transition temperature of 81 °C, a melting point of 255 °C, and an intrinsic viscosity of 0.51 was obtained.

[0149] [Production of MB-A] During the polymerization of PET-1 in the above item, silica particles (silica-1) having an average primary particle diameter of 65 nm dispersed in ethylene glycol were added so that the addition amount to PET was 1% by mass to obtain PET-based particle master pellets MB-A. The glass transition temperature of the obtained melt-polymerized MB-A was 80 °C, the melting point was 255 °C, and the intrinsic viscosity was 0.53.

[0150] [Manufacture of MB-B] When polymerizing PET-2 in the previous section, silica particles (silica-1) with an average primary particle diameter of 65 nm dispersed in ethylene glycol were added so that the addition amount to PET was 1% by mass, and a PET-based particle master pellet MB-A was obtained. The glass transition temperature of the obtained melt-polymerized MB-A was 81 °C, the melting point was 255 °C, and the intrinsic viscosity was 0.63.

[0151] [Table 1]

[0152] [Functional additive (A)] [Antistatic agent] Polythiophene-based compound (a-1) In an aqueous solution of 1887 parts by mass containing 20.8 parts by mass of polystyrene sulfonic acid, which is an acidic polymer compound, 49 parts by mass of a 1% by mass aqueous solution of iron(III) sulfate, 8.8 parts by mass of 3,4-ethylenedioxythiophene, which is a thiophene compound, and 117 parts by mass of a 10.9% by mass aqueous solution of peroxodisulfuric acid were added. This mixture was stirred at 18 °C for 23 hours, and 154 parts by mass of a cation exchange resin (Lewatit Monoplus S100H) and 232 parts by mass of an anion exchange resin (Lewatit Monoplus M800) were added to this mixture and stirred for 2 hours. Then, the ion exchange resins were filtered off to obtain a polythiophene-based compound (a-1) (solid content concentration: 1.3% by weight) composed of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonic acid.

[0153] [Release agent] · Long-chain alkyl group-containing resin (a-2) In a 25 mL pressure-resistant glass polymerization ampoule, 2-hydroxyethyl acrylate (HEA) (manufactured by Kanto Chemical Co., Ltd.), α,α'-azobisisobutyronitrile (AIBN) (manufactured by Kanto Chemical Co., Ltd.) as a polymerization initiator, cumyl dithiobenzoate (CDB) as a RAFT agent, and toluene as a solvent were charged in a ratio of HEA / CDB / AIBN / toluene of 0.35 / 0.03 / 0.007 / 2.27 by weight (g). Next, the mixed solution in the ampoule was degassed twice by freeze-degassing, the ampoule was sealed, and heated in an oil bath at 100°C for 18 hours to obtain a reaction solution containing the polymer.

[0154] To the reaction solution in the ampoule, docosyl acrylate, AIBN as a polymerization initiator, and toluene as a solvent were added in a ratio of docosyl acrylate / AIBN / toluene = 4.65 / 0.003 / 1.3 by weight (g). After two freeze-degassing cycles, the ampoule was sealed and heated at 100°C for 48 hours. Subsequently, the polymerization solution was added dropwise to 20 times its mass of hexane and stirred to precipitate a solid. The obtained solid was filtered and dried overnight under vacuum at 40°C to obtain a long-chain alkyl group-containing resin (a-2), which is a block copolymer having an alkyl group with 22 carbon atoms.

[0155] The obtained long-chain alkyl group-containing resin (a-2) was emulsified as follows to obtain an aqueous resin emulsion. 375g of water was placed in a 1L homomixer, and 45g of polyoxyethylene nonylphenyl ether, 30g of polyoxyethylene polyoxypropylene glycol, 200g of long-chain alkyl group-containing resin (a-2), and 150g of toluene were added sequentially. The mixture was heated to 70°C and stirred uniformly. This mixture was transferred to a pressurized homogenizer for emulsification, and then the toluene was removed by distillation under reduced pressure and heating.

[0156] [Resin or compound (B)] • Polyester resin (b-1) Takamatsu Oil & Fat Co., Ltd.'s "PESRESIN" (registered trademark) A-210 (solid content concentration 30% by mass, solvent: water) was used.

[0157] • Acrylic resin (b-2) In a stainless steel reaction vessel, methyl methacrylate (α), hydroxyethyl methacrylate (β), and urethane acrylate oligomer (manufactured by Negami Kogyo Co., Ltd., Art Resin® UN-3320HA, with 6 acryloyl groups) (γ) were charged in a mass ratio of (α) / (β) / (γ) = 94 / 1 / 5. As an emulsifier, 2 parts by mass of sodium dodecylbenzenesulfonate were added to 100 parts by mass of the total of (α) to (γ), and the mixture was stirred to prepare Mixture 1. Next, a reaction apparatus equipped with a stirrer, reflux condenser, thermometer, and dropping funnel was prepared. 60 parts by weight of the above Mixture 1, 200 parts by weight of isopropyl alcohol, and 5 parts by weight of potassium persulfate as a polymerization initiator were charged into the reaction apparatus and heated to 60°C to prepare Mixture 2. Mixture 2 was maintained at 60°C for 20 minutes. Next, a mixture 3 was prepared consisting of 40 parts by weight of mixture 1, 50 parts by weight of isopropyl alcohol, and 5 parts by weight of potassium persulfate. Subsequently, mixture 3 was added dropwise to mixture 2 over 2 hours using a dropping funnel to prepare mixture 4. After that, mixture 4 was kept heated at 60°C for 2 hours. After the obtained mixture 4 was cooled to below 50°C, it was transferred to a container equipped with a stirrer and a vacuum device. 60 parts by weight of 25% aqueous ammonia and 900 parts by weight of pure water were added, and the isopropyl alcohol and unreacted monomers were recovered under reduced pressure while heating at 60°C to obtain acrylic resin (b-2) dispersed in pure water.

[0158] • Methylolated melamine resin (b-3) We used "Nikarac" (registered trademark) MW-035 (solid content concentration 70% by mass, solvent: water), manufactured by Sanwa Chemical Co., Ltd.

[0159] [Particle component (C)] ·Particle (c-1) We used "Spherica" ​​(registered trademark) 140 (silica particles, average particle primary diameter 140 nm) manufactured by JGC Catalysts & Chemicals Co., Ltd.

[0160] ·Particle (c-2) We used "Cataloid" (registered trademark) SI-80P (silica particles, average particle primary diameter 80 nm) manufactured by JGC Catalysts & Chemicals Co., Ltd.

[0161] · Particles (c-3) An aqueous dispersion of silica particles with an average primary particle diameter of 200 nm was used.

[0162] · Particles (c-4) “Cataloid-S” (registered trademark) SI-50 (silica particles, average primary particle diameter 20 nm) manufactured by Nisshuki Catalyst Co., Ltd. was used.

[0163] · Particles (c-5) “Seefoster” (registered trademark) KEW-30 (silica particles, average primary particle diameter 300 nm) manufactured by Nippon Catalyst Co., Ltd. was used.

[0164] · Particles (c-6) “Seefoster” (registered trademark) KEW-50 (silica particles, average primary particle diameter 500 nm) manufactured by Nippon Catalyst Co., Ltd. was used.

[0165] [Preparation of Paint Compositions A to G] The mold release agent (A), resin or compound (B), and particle component (C) obtained as described above were mixed at the solid content mass ratios shown in Table 2 to obtain paint compositions A to G.

[0166]

Table 2

[0167] (Example 1) PET-1 and PET-2 were dried under reduced pressure at 180 °C for 2.5 hours, then formulated so that the amounts of the P1 layer and P3 layer were as described in Table 3, supplied to two respective extruders, melt-extruded, filtered through a filter, and then combined at a feed block so as to be laminated into two layers (P1 layer / P3 layer configuration), and then wound and cooled and solidified on a cooling cast roll maintained at 35 °C via a T-die using an electrostatic application casting method to obtain an unstretched film. This unstretched film was led between opposing electrodes and an earth roll, nitrogen gas was introduced into the apparatus, and the treatment intensity (E value) was 240 W·min / m 2Under these conditions, plasma treatment was performed on the surface of the P1 layer using atmospheric pressure glow discharge.

[0168] After processing, the unstretched film is passed through an anti-static roll set to a roll temperature of 25°C, and then sequentially stretched in a biaxial stretcher under the conditions described in Table 4. First, it is guided to a group of stretching rolls heated to 60°C to 100°C in the longitudinal direction and stretched to a total of 3.5 times its original length. Then, in order to construct the P2 layer, which is the coating layer, on the surface of the P3 layer, inline coating is performed using a gravure coater with coating composition A so that the thickness of the coating layer after drying is the value described in Table 3. The coated film is then guided to a tenter and preheated to 80°C. After that, it is stretched in three equally lengthened sections set to 90°C, 110°C, and 130°C, increasing the temperature by 1.6 times in each section in stages, to achieve a total stretch of 4.1 times in the width direction. Finally, it is heat-treated at 235°C under constant length and relaxed by 3% in the width direction to obtain a biaxially oriented polyester film with a thickness of 16 μm and a coating layer on one side.

[0169] [Table 3]

[0170] [Table 4]

[0171] The composition, film properties, and surface properties of the obtained biaxially oriented polyester film are shown in Table 5.

[0172] [Table 5]

[0173] As shown in Table 6, the film exhibited good production suitability and application suitability, with excellent extrusion stability, film roll winding properties (wrinkling, winding misalignment), coating layer durability (abrasion, particle shedding), and fine wiring resist properties.

[0174] [Table 6]

[0175] (Example 2) In Example 2, a biaxially oriented polyester film with a thickness of 16 μm was obtained in the same manner as in Example 1, except that paint composition B was used to construct the P2 layer. The composition, film properties, surface properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Table 5. The production suitability and application suitability were as good as in Example 1, as shown in Table 6.

[0176] (Examples 3 and 4) In Examples 3 and 4, a biaxially oriented polyester film with a thickness of 16 μm was obtained in the same manner as in Example 1, except that the treatment intensity of the atmospheric pressure glow discharge treatment (plasma treatment) applied to the P1 layer was changed as shown in Table 4. The composition, film properties, surface properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Table 5. As shown in Table 6, the suitability for production and application was as follows: In Example 3, the static friction coefficient on both sides of the film was lower than in Example 1, and the winding misalignment of the film roll worsened, but it was within the range of practical use. Otherwise, it was a good film, similar to Example 1. In Example 4, the winding wrinkles of the film roll worsened compared to Example 1, but it was within the range of practical use. Otherwise, it was a good film, similar to Example 1.

[0177] (Examples 5 and 6) In Example 5, the thickness of the P2 layer, which is the coating layer, was changed as shown in Tables 3 and 4. Except for these changes, a biaxially oriented polyester film with a thickness of 16 μm was obtained in the same manner as in Example 1. The composition, film properties, surface properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Table 5. As shown in Table 6, the suitability for production and application was as follows: in Example 5, the winding wrinkles of the film roll and the fine wiring resist characteristics were worse than in Example 1, and in Example 6, the winding misalignment of the film roll and particle shedding of the coated layer were worse than in Example 1, but these were still within the range of practical use. Otherwise, the film was as good as in Example 1.

[0178] (Examples 7 and 8) In Examples 5 and 6, a biaxially oriented polyester film with a thickness of 16 μm was obtained in the same manner as in Example 1, except that the coating composition used to construct the P2 layer was changed as shown in Tables 3 and 4, and the particle size contained in the P2 layer was changed. The composition, film properties, surface properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Table 5. As shown in Table 6, the suitability for production and application was good, although in Example 7 the particle shedding of the coating layer and the fine wiring resist characteristics were worse than in Example 1, and in Example 8 the winding wrinkles of the film roll were worse than in Example 1, but still within the range of practical use. Otherwise, the film was good, similar to Example 1.

[0179] (Examples 9 and 10) In Examples 9 and 10, a biaxially oriented polyester film with a thickness of 16 μm was obtained in the same manner as in Example 1, except that the intrinsic viscosity of the P1 layer was changed by modifying the raw materials used for the P1 layer as shown in Table 3, and the amount of particles included was as shown in Table 3. The composition, film properties, surface properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Table 5. As shown in Table 6, the production suitability and application suitability were as follows: In Example 9, the intrinsic viscosity of the P1 layer was increased compared to Example 1, and particles were included. Although the durability of the coating layer (abrasion, particle shedding) and the fine wiring resist characteristics deteriorated, they were within a practical range. Otherwise, it was a good film, similar to Example 1. In Example 10, by setting the intrinsic viscosity of the P1 layer within a favorable range, the fine wiring resist characteristics deteriorated compared to Example 1, but were still within a practical range. Furthermore, even with the same particle concentration as Example 9, it was a film with good production suitability, similar to Example 1.

[0180] (Example 11) In Example 11, a biaxially oriented polyester film with a thickness of 16 μm was obtained in the same manner as in Example 1, except that the intrinsic viscosity of the P1 layer was changed by modifying the raw materials used for the P1 layer as shown in Table 3. The composition, film properties, surface properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Table 5. As shown in Table 6, the production suitability and application suitability were within the range of practical use, although extrusion stability and film roll misalignment deteriorated. Otherwise, the film was good, similar to Example 1.

[0181] (Example 12) In Example 12, a biaxially oriented polyester film with a thickness of 16 μm was obtained in the same manner as in Example 1, except that the coating composition for constructing the P2 layer, which is the coating layer, was changed as shown in Tables 3 and 4, and the particle size contained in the P2 layer was changed. The composition, film properties, surface properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Table 5. As shown in Table 6, in Example 12, while the film roll misalignment, particle shedding of the coating layer, and fine wiring resist characteristics were worse than in Example 1, they were still within the range of practical use. Otherwise, the film was as good as in Example 1.

[0182] (Comparative Example 1) In Comparative Example 1, a biaxially oriented polyester film with a thickness of 16 μm was obtained in the same manner as in Example 1, except that the P1 layer was not subjected to atmospheric pressure glow discharge treatment (plasma treatment). The composition, film properties, surface properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Table 5. As shown in Table 6, the suitability for production and application was significantly worse for Comparative Example 1 compared to Example 1, with significantly worse wrinkles in the film roll and worse friction on both sides of the film, resulting in significantly worse abrasion of the coating layer compared to Example 1.

[0183] (Comparative Example 2) In Comparative Example 2, a biaxially oriented polyester film with a thickness of 16 μm was obtained in the same manner as in Example 1, except that the P2 layer, which is a coating layer, was not provided on the surface of the P3 layer. The composition, film properties, surface properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Table 5. As shown in Table 6, the suitability for production and application was significantly worse for Comparative Example 2 compared to Example 1, with significantly worse wrinkles in the film roll and worse friction on both sides of the film, resulting in significantly worse abrasion of the coating layer compared to Example 1.

[0184] (Comparative Examples 3 and 4) In Comparative Example 3, a biaxially oriented polyester film with a thickness of 16 μm was obtained in the same manner as in Example 1, except that the thickness of the P2 layer was changed as shown in Table 4, and in Comparative Example 4, the coating composition constituting the P2 layer was changed as shown in Table 3. The composition, film properties, surface properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Table 5. As shown in Table 6, the production suitability and application suitability of the film were significantly inferior to those of Example 1. In Comparative Example 3, the abrasion of the coated layer and the fine wiring resist properties were significantly inferior, while in Comparative Example 4, the film roll misalignment, particle shedding of the coated layer, and fine wiring resist properties were significantly inferior.

[0185] (Comparative Example 5) In Comparative Example 5, a biaxially oriented polyester film with a thickness of 16 μm was obtained in the same manner as in Example 1, except that the paint composition and the thickness of the P2 layer were changed as shown in Tables 3 and 4. The composition, film properties, surface properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Table 5. As shown in Table 6, the suitability for production and application is as follows: In Comparative Example 6, the thinner coating layer resulted in a film with significantly worse particle shedding compared to Example 1.

[0186] (Comparative Example 6) In Comparative Example 6, a biaxially oriented polyester film with a thickness of 16 μm was obtained in the same manner as in Example 1, except that the treatment intensity of the atmospheric pressure glow discharge treatment (plasma treatment) applied to the P1 layer was changed as shown in Table 4. The composition, film properties, surface properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Table 5. As shown in Table 6, the suitability for production and application is as follows: In Comparative Example 6, increasing the treatment intensity of atmospheric pressure glow discharge treatment (plasma treatment) increased the number of protrusions with a height of 10 nm or more on surface A, resulting in a decrease in the static friction coefficient on both sides of the film compared to Example 1, and a film in which the winding misalignment of the film roll worsened significantly compared to Example 1. In addition, increasing the treatment intensity of atmospheric pressure glow discharge treatment (plasma treatment) increased the number of coarse foreign matter with a height of 50 nm or more on surface A, which is presumed to originate from degraded material of the P1 layer, compared to Example 1, and a film in which the abrasion of the coating layer and the fine wiring resist characteristics were significantly worse than in Example 1. [Industrial applicability]

[0187] The biaxially oriented polyester film of the present invention has a highly smooth surface with protrusions and a uniform surface modulus on one side of the film, and a thin film coating layer with controlled slipperiness and surface properties on the opposite side. This improves the durability of the coating layer (abrasion and shedding of contained particles) after winding it as a roll, making it suitable for use as a base film for dry film resists that meet the optical properties required for next-generation fine wiring. [Explanation of symbols]

[0188] 1. Layer having surface A (P1 layer) 2. Surface with protrusions (Surface A) 3. Zero plane (average plane; height 0 nm) in AFM measurement and scanning white light interference microscopy measurement. 4. A 10 nm high line (R) obtained by AFM measurement 10nm ) 5. Scanning white light interference microscopy measurement of a 50 nm high line (R 50nm ) 6. Protrusions present on surface A 7. Coating layer having side B (P2 layer) 8. The opposite side from side A (side B) 9. Biaxially oriented polyester film with a 2-layer structure (P1 layer / P2 layer) 10. Middle layer (P3 layer) 11.3-layer (P1 layer / P3 layer / P2 layer) biaxially oriented polyester film

Claims

1. A biaxially oriented polyester film having a surface (Side A) that satisfies (1) below, and a coating layer provided opposite to Side A that satisfies (2) to (4) below. (1) The number of protrusions with a height of 1 nm or more and less than 10 nm measured on surface A by AFM (Atomic Force Microscope) is N １－１０ｎｍ A (pcs / 25μm ２ ) If N １－１０ｎｍ A must be between 100 and 1000. (2) The thickness of the coating layer is 10 nm or more and 200 nm or less. (3) The coating layer contains 0.5% by mass or more and 10% by mass or less of particles with an average primary particle diameter of 3 nm or more and 300 nm or less, relative to the entire coating layer. (4) When surface modulus measurement of surface A using AFM is performed, if the maximum modulus of protrusions of 10 nm or more in height on surface A is F MAX (GPa) and the average modulus of protrusions of 1 nm or more in height and less than 10 nm is F AVE (GPa), then F MAX / F AVE is 50 or less.

2. The number of protrusions with a height of 50 nm or more obtained by measuring surface A with an optical interference microscope is N ５０ｎｍ (pcs / mm ２ ) If N ５０ｎｍ The biaxially oriented polyester film according to claim 1, wherein the ratio is 50 or less.

3. When the layer constituting surface A is defined as layer P1, the main component of layer P1 is polyester resin, and the intrinsic viscosity of the polyester resin is IV Ｐ１ The biaxially oriented polyester fiber according to claim 1 or 2, characterized in that the (dl / g) is 0.45 or more and 0.55 or less. Room.

4. Taking the surface of the coating layer as the B surface and the surface free energy of the B surface as E Ｂ (mN / m), and when the surface free energy of the A surface is E Ａ (mN / m), the absolute value |E Ａ - E Ｂ | (mN / m) is 5 or more, the biaxially oriented polyester film according to any one of claims 1 to 3.

5. E is the difference in surface free energy between both sides of the film. Ａ -E Ｂ The biaxially oriented polyester film according to claim 4, wherein (mN / m) is 5 or more.

6. E is the difference in surface free energy between both sides of the film. Ａ -E Ｂ The biaxially oriented polyester film according to claim 4, wherein (mN / m) is -5 or less.

7. A biaxially oriented polyester film according to any one of claims 1 to 6, used as a base film for dry film resist.

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