Biaxially oriented polyester film for dry film resist support

Abstract

To provide a biaxially oriented polyester film for a support of a dry film resist which is excellent in processing suitability in a lamination step while being excellent in resist characteristics for next-generation fine wiring obtained by providing a surface having protrusions whose height is controlled on one surface of the film and controlling heat shrinkage of the film.SOLUTION: The biaxially oriented polyester film for a support of a dry film resist has a surface (A-surface) having protrusions on at least one side and satisfies the following requirements (1) to (3): (1) when a maximum protrusion height of the A- surface is SpA (nm), SpA is 30 or more and 80 or less; (2) when L150°C(%) is a widthwise dimensional shrinkage rate of the biaxially oriented polyester after being heated at 150°C for 30 minutes, L150°C(%) is -0.5 or more and 0.5 or less; (3) when the layer (P1-layer) constituting the A-surface contains particles, number-based particle size distribution measurement of the particles is performed, secondary particle sizes are plotted on a horizontal axis, and abundance ratios of the particles are plotted on a vertical axis, the plotted result shows at least one or more peaks (secondary particle peak diameter D2(nm)) in a region of the secondary particle size between 100 nm and 250 nm and no peaks in the region of the secondary particle size exceeding 250 nm.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a biaxially oriented polyester film for a dry film resist support having a surface with specific protrusions and thermodynamic properties.

Background Art

[0002] Due to its good processability, polyester resin is used in various industrial fields. In addition, products obtained by processing these polyester resins into film form (polyester films) play an important role in today's life, such as industrial applications, optical product applications, packaging applications, and magnetic recording tape applications. In recent years, in electronic information devices, miniaturization and high integration have advanced, and accordingly, the wiring of electronic information devices has also become finer. For the production of these fine wirings in electronic information devices, a transparent film is used as a support, and a photo-curable resin layer (resist layer) is provided on the surface. This is adhered to a substrate with a thin film copper laminated thereon, and the copper wiring shape is depicted using the photoresist technology for the entire film. After film peeling, the dry film resist method is often used, and in next-generation products, it is necessary to perform very fine processing with a wiring width of 2 to 5 μm. Generally, polyester films are formed during the manufacturing process and then wound into rolls. If the film surface is too smooth, the films will stick together, worsening the winding performance. Therefore, to ensure the winding performance of the film, 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). By reducing the amount of added particles or reducing the diameter of the added particles, the optical properties of the film that contribute to resist wiring can be improved. On the other hand, because the number and height of protrusions on the film surface are reduced, in the lamination process in which the film with the resist layer is bonded to a metal substrate on which wiring is formed, the adhesion with the metal roll increases when conveyed under tension, increasing friction and reducing handling performance. Furthermore, during lamination, pressure is generally applied using rubber rolls heated to 90°C to 120°C to ensure close contact with the metal substrate. However, if the thermal dimensional changes of the film are large, the pressure applied during lamination will not be uniform, resulting in wrinkles (hereinafter sometimes referred to as lamination wrinkles), which can lead to defects in the resist wiring. To achieve both optical properties and handling and lamination suitability, for example, Patent Document 1 describes a technique for achieving both optical properties and handling by providing a particle-containing coating layer on a polyester film containing fine particles, and Patent Documents 2 and 3 describe a technique for controlling the thermal shrinkage of the film by controlling the film manufacturing conditions. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-188612 [Patent Document 2] Japanese Patent Publication No. 2015-182261 [Patent Document 3] Japanese Patent Publication No. 2021-160240 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, in films having a coating layer like the one described in Patent Document 1, friction with the metal rolls during the processing process generates shavings over time, which are mixed into the film as foreign matter, posing a challenge for long-term production. Furthermore, when strengthening the coating layer with a thermocrosslinkable resin, the drying temperature must be high and the drying time long, which necessitates a reduction in the film formation speed, making it undesirable from a productivity standpoint. Furthermore, in films with controlled thermal shrinkage, such as those described in Patent Documents 2 and 3, handling properties are provided by roughening the surface by incorporating coarse particles on one or both sides of the film. As a result, the optical properties are insufficient for next-generation resist fine wiring with a wiring width of 2 to 5 μm. As mentioned above, reducing the diameter of the incorporated particles results in a trade-off between optical properties and handling properties, making it difficult to achieve both. In addition, for handling properties with metal rolls in the lamination process, it is necessary to form protrusions on the surface of the film that suppress adhesion with the metal rolls while using particles of a size that does not affect the resist properties. The present invention aims to provide a biaxially oriented polyester film for dry film resist supports that exhibits excellent resist properties for next-generation fine wiring while also being highly suitable for processing in the lamination process. [Means for solving the problem]

[0005] To solve the above problems, the present invention has the following configuration. That is, [I] A biaxially oriented polyester film for a dry film resist support having a surface with protrusions (surface A) on at least one side, and satisfying the following requirements (1) to (3). (1) When the maximum protrusion height of surface A is defined as SpA (nm), SpA is 30 or more and 80 or less. (2) The dimensional shrinkage rate after heating the biaxially oriented polyester film at a temperature of 150°C for 30 minutes is L 150℃ (%), L 150℃ (%) is between -0.5 and 0.5 (3) When the layer constituting surface A (P1 layer) contains particles and the particle size distribution is measured based on the number of particles, and the secondary particle diameter is plotted on the horizontal axis and the particle abundance ratio is plotted on the vertical axis, there is at least one peak (secondary particle peak diameter D2 (nm)) in the region where the secondary particle diameter is 100 nm or more and 250 nm or less, and there is no peak in the region where the secondary particle diameter is greater than 250 nm. [II] The biaxially oriented polyester film for a dry film resist support according to [II], wherein the arithmetic mean surface roughness of surface A is SaA (nm), and SaA is 1.6 or more and 4.5 or less. [III] The number of protrusions on surface A with a height of 50 nm or more is N 50nm A (pieces / mm 2 If we consider N 50nm A biaxially oriented polyester film for a dry film resist support according to [I] or [II], wherein A is 20 or more and 350 or less. [IV] The number of protrusions on surface A that are 10 nm or taller is N 10nm A (pieces / mm 2 If we consider N 10nm A biaxially oriented polyester film for a dry film resist support according to any of [I] to [III], wherein A is between 6000 and 50000. [V] In the particle size distribution measurement based on the number of particles contained in the P1 layer, particles with a secondary particle peak diameter D2 (nm) of 100 or more and 250 or less are aggregated particles formed by the aggregation of multiple particles with a primary particle peak diameter D1 (nm) of 10 or more and 160 or less, as described in any of [I] to [IV]. [VI] A biaxially oriented polyester film for a dry film resist support according to any one of [I] to [V], wherein the concentration of particles contained in the P1 layer is 0.01% by mass or more and 1.0% by mass or less of the entire P1 layer. [VII] A biaxially oriented polyester film for a dry film resist support according to any one of [I] to [VI], wherein the surface opposite to surface A is called surface B, and the maximum protrusion height of surface B is SpB (nm), and SpB is greater than SpA and between 50 and 200. [Effects of the Invention]

[0006] The present invention relates to a biaxially oriented polyester film for a dry film resist support, which has excellent resist characteristics for next-generation fine wiring and excellent processing suitability in a lamination process.

Brief Description of the Drawings

[0007] [Figure 1] It is a conceptual diagram showing the protrusions on the A side measured by a scanning white interference microscope. [Figure 2] Two-layer configuration diagram of the biaxially oriented polyester film of the present invention [Figure 3] Three-layer configuration diagram of the polyester film when having the coating layer of the present invention

Embodiments for Carrying Out the Invention

[0008] Hereinafter, the present invention will be described in detail.

[0009] The present invention relates to a biaxially oriented polyester film. A biaxially oriented polyester film for a dry film resist support having at least one side with a surface (A side) having protrusions and satisfying the following requirements (1) to (3). (1) When the maximum protrusion height of the A side is SpA (nm), SpA is 30 or more and 80 or less (2) When the dimensional shrinkage rate in the width direction after heating the polyester film at 150 ° C for 30 minutes is L 150℃ (%), L 150℃ (%) is -0.5 or more and 0.5 or less (3) The layer (P1 layer) constituting the A side contains particles. When performing a number-based particle size distribution measurement of the particles and plotting the secondary particle diameter on the horizontal axis and the particle abundance ratio on the vertical axis, there is at least one peak (secondary particle peak diameter D2 (nm)) in the region where the secondary particle diameter is 100 nm or more and 250 nm or less, and there is no peak in the region where the secondary particle diameter exceeds 250 nm.

[0010] The biaxially oriented polyester film of the present invention preferably has a laminated structure of at least two layers, such as a P1 layer / P2 layer, in which a polyester resin layer (P1 layer) having the A surface and a P2 layer containing particles on the side of the P1 layer opposite to the A surface are provided. From the viewpoint of improving the optical properties of the biaxially oriented polyester film of the present invention, it is preferable to have an intermediate layer (P3 layer) that does not contain particles between the P1 layer and the P2 layer, and it is more preferable to have a laminated structure of at least three layers, such as a heterogeneous three-layer laminated structure consisting of P1 layer / P3 layer / P2 layer.

[0011] (Surface with protrusions: Surface A) In the present invention, surface A has protrusions, and when the maximum protrusion height obtained by scanning white light interference microscopy measurement according to the method described later is defined as SpA (nm), SpA is between 30 and 80. When the biaxially oriented polyester film of the present invention is used as a film for a dry film resist support, SpA is a value that reflects the maximum height of the protrusions present on surface A, and is a value that affects the slipperiness of surface A with the metal roll, and the resist characteristics for fine wiring when a resist layer is provided on the side opposite to surface A and exposure processing is performed from surface A. An SpA of 30 or more suppresses a decrease in handling performance when the film is transported on a metal roll under high tension during the processing step, and an SpA of 80 or less suppresses the occurrence of defects in the wiring shape due to light scattering on surface A when resist wiring is formed by exposure. A more preferable range for SpA is 30 to 80, and even more preferable is 40 to 70. In the biaxially oriented polyester film for dry film resist support of the present invention, it is preferable that the arithmetic mean surface roughness SaA (nm), obtained by scanning white light interference microscopy measurement according to the method described later, is 1.6 or more and 4.5 or less on surface A. The arithmetic mean surface roughness SaA (nm) of surface A is a value that represents the smoothness of surface A and is a value that affects the slipperiness of both sides of the biaxially oriented polyester film. It is also a value that affects the fine wiring resist characteristics when the biaxially oriented polyester film is used as a film for dry film resist support and a resist layer is provided on the side opposite to surface A, and exposure is performed from the side of surface A. When SaA is 1.6 or higher, it is possible to suppress the occurrence of wrinkles in the film roll when the film is wound and film is formed at high speed, and when it is 4.5 or lower, it is possible to suppress the occurrence of defects in the resist wiring due to light scattering on the A side. A more preferable range for SaA is 1.8 to 4.0. In the A surface of the biaxially oriented polyester film of the present invention, the number of protrusions with a height of 10 nm or more obtained by scanning white light interference microscopy measurement according to the method described later is N 10nm A (pieces / mm 2 ) when N 10nm It is preferable that A is between 6000 and 50000. When the biaxially oriented polyester film of the present invention is used as a film for a dry film resist support, N 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 placed on surface A and exposure processing is performed from the side opposite to surface A. 10nm When manufacturing biaxially oriented polyester film and winding it into a film roll, A affects the winding shape of the roll and the likelihood of scratches on side A. N on surface A 10nm A (pieces / mm 2When the number of sides (N) on the A side becomes 6000 or more, the contact area (contact area) with the P2 layer surface (B side) on the opposite side of the A side is reduced during roll winding, and friction between the sides is reduced, thereby improving the winding appearance of the film roll. 10nm A (pieces / mm 2 By setting the N on side A to 50000 or less, the friction on both sides of the film is excessively reduced, and the occurrence of film roll misalignment can be suppressed. 10nm A (pieces / mm 2 A more preferable range for ) is 7000 to 35000, and an even more preferable range is 10000 to 25000.

[0012] 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 20 or more and 350 or less. 50nm A (pieces / mm 2 The number of protrusions N, which are 50 nm or taller, is determined by the software attached to the scanning white light interference microscope. Based on ISO 25178, it is a value measured by the measurement method described later, and reflects the number of high protrusions present on surface A that suppress adhesion with the smooth metal roll, and is a value that affects the process suitability of surface A in the processing steps. 50nm A (pieces / mm 2 By setting the ratio to 20 or more, the contact area with the process metal roll can be reduced even when tension is applied, improving the ease of sliding with the metal roll. 50nm A (pieces / mm 2 By setting the value to 350 or less, it is possible to suppress the occurrence of defects in the wiring shape when forming fine wiring resist. 50nm A (pieces / mm 2 A more preferable range for ) is 30 to 300, and an even more preferable range is 60 to 200. (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.

[0013] (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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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. The biaxially oriented polyester film of the present invention, due to its biaxial orientation, has improved mechanical strength, 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. Detailed film formation conditions will be described later.

[0018] In the A surface of the P1 layer of the present invention, the maximum protrusion height SpA and the number of protrusions N with a height of 10 nm or more are obtained by scanning white light interference microscopy. 10nm A and the number of protrusions with a height of 50 nm or more N 50nm Methods for setting A to the aforementioned range include adding particles having a specific particle size as described later, transferring a shape to the surface using a mold, such as in nanoimprinting, and performing plasma surface treatment by atmospheric pressure glow discharge on an unstretched sheet followed by biaxial stretching. In particular, from the viewpoint of increasing the number of fine protrusions formed on the P1 layer while using minute particles that do not degrade optical properties for fine wiring, it is more preferable to incorporate a particle master pellet containing minute particles, as described later, into the P1 layer, perform plasma treatment by atmospheric pressure glow discharge, and then perform biaxial stretching. Plasma surface treatment by atmospheric pressure glow discharge (hereinafter sometimes referred to as atmospheric pressure plasma treatment) 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. 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. 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.

[0019] 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 2The following conditions can be met to prevent excessive damage to the polyester film and reduce the generation of surface foreign matter.

[0020] <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 10nm A can be increased. Regarding the particles contained in the P1 layer, either inorganic or organic particles may be used, and two or more types of particles may be used in combination. However, when the particle size distribution measurement based on the number of particles contained in the P1 layer is performed as described below, and the particle size is plotted on the horizontal axis and the particle abundance ratio on the vertical axis, it is necessary that there is at least one peak in the region where the particle size is between 100 nm and 250 nm, and no peak in the region where the particle size is greater than 250 nm. By including particles with a particle size of 100 nm or more in the P1 layer, it is possible to provide smooth sliding with the process metal roll in the lamination process, and by setting the particle size to 250 nm or less, it is possible to suppress the occurrence of pinhole defects when forming resist wiring. More preferably, when the peak position of the particle size obtained by the number-based particle size distribution measurement is defined as the secondary particle peak diameter D2 (nm), it is preferable that, among the particles where the secondary particle peak diameter D2 (nm) is 100 to 250, there exist aggregated particles formed by the aggregation of multiple particles where the primary particle peak diameter (D1 (nm)) obtained by the method described later is 10 to 160. By using aggregated particles, each particle has a primary particle diameter D1 (nm) that does not degrade the resist properties for fine wiring, while forming particles where the secondary particle peak diameter D2 (nm) is 100 to 250, which can help form high protrusions that provide the aforementioned smooth sliding properties with the metal roll. Examples of usable 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, and silica (wet silica, dry silica, 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. Among the inorganic particles, alumina is preferred because it easily forms aggregated particles, and among the organic particles, styrene resin is preferred because its refractive index is close to that of the biaxially oriented polyester film. The particles contained in the P1 layer can be the exemplified inorganic and organic particles used individually or in combination of two or more types. Here, aggregated particles are particles formed by the aggregation of at least two particles having a primary particle peak diameter D1 (nm) obtained by the method described later, resulting in a secondary particle peak diameter D2 (nm) that is larger than the primary particle peak diameter D1 (nm). Regarding the relationship between the primary particle peak diameter D1 (nm) and the secondary particle peak diameter D2 (nm) of aggregated particles, it is more preferable that the secondary particle peak diameter D2 (nm) is 1.1 times or more the primary particle peak diameter D1 (nm), even more preferable that the secondary particle peak diameter D2 (nm) is 1.3 times or more the primary particle peak diameter D1 (nm), and most preferable that the secondary particle peak diameter D2 (nm) is 1.5 times or more the primary particle peak diameter D1 (nm). As for the form of aggregated particles, aggregated particles may be formed by the aggregation of multiple particles of one type contained in the P1 layer, or, if the P1 layer contains two or more types of particles, aggregated particles may be formed by the aggregation of multiple particles of each of those types. Furthermore, regarding the particle size of the particles contained in the P1 layer, from the viewpoint of suppressing light scattering (Mie scattering) of the 365 nm wavelength resist light used to form fine wiring, it is preferable that the particle size is smaller than 180 nm, which is half the wavelength of 365 nm. For this reason, when the primary particle peak diameter of the particles constituting the aggregated particles of the present invention is D1 (nm), it is preferable that D1 be between 10 and 160 from the viewpoint of suppressing light scattering of the resist light as much as possible. Furthermore, by setting the secondary particle peak diameter D2 (nm) of the aggregated particles to 100 or more and 250 or less, the formation of protrusions that provide smooth sliding between surface A and the process metal roll can be promoted.

[0021] Furthermore, from the viewpoint of maintaining good optical properties for fine wiring resists of biaxially oriented polyester films, the concentration of aggregated particles contained in the P1 layer of the present invention is preferably 0.01% by mass or more and 1.0% by mass or less of the total P1 layer.

[0022] In the biaxially oriented polyester film of the present invention, a preferred method for forming aggregated particles is to create a particle master pellet by pre-mixing the particles to be contained in the P1 layer with a polyester resin, and then mix it with the polyester resin constituting the P1 layer and perform melt extrusion. This method disperses the particles throughout the P1 layer and suppresses the generation of aggregated particles whose secondary particle diameter exceeds 365 nm, which is the wavelength of the resist light. Furthermore, the intrinsic viscosity of the particle master pellet is IV MP (dl / g), the intrinsic viscosity of the polyester resin to be mixed is IV PET (dl / g) MP is IV PET A higher value is preferable. This is preferable because, when the P1 layer is extruded, the uniformly dispersed particles undergo gradual aggregation due to the difference in the intrinsic viscosity of the surrounding polyester resin, thereby creating aggregated particles that contribute to the aforementioned protrusions on surface A. The intrinsic viscosity of the particle master pellets for forming the P1 layer (IV MP ) and the intrinsic viscosity (IV) of the polyester resin to be mixed. PET The difference in intrinsic viscosity between ) and IV MP -IV PET In that case, IV MP -IV PET A preferred range is 0.1 or higher, and more preferably 0.3 or higher. In the biaxially oriented polyester film of the present invention, the intrinsic viscosity (IV) of the entire P1 layer is set to IV P1 If (dl / g), then IV P1 (dl / g) is preferably 0.45 or more and 0.60 or less. IV is a number that reflects the length of the molecular chain; the shorter the molecular chain, the easier it is for the polyester molecules to orient and crystallize when stretched and heat-treated. P1By setting the (dl / g) value to 0.60 or less, protrusion formation in the biaxial stretching film manufacturing process can be promoted, improving slipperiness. Furthermore, in the lamination process, the shorter molecular chains increase surface molecular mobility. Therefore, when in contact with a laminating roll heated to 90-120°C, the surface softens and becomes more conformable to the roll, suppressing wrinkles and air bubbles during lamination. IV P1 By setting the pressure to 0.45 dl / g or higher, it is possible to suppress the formation of air bubbles during melt extrusion of polyester resin, which can cause the film to tear and make biaxially oriented film formation difficult. The thickness of the P1 layer in the biaxially oriented polyester film of the present invention is T P1 When T is set to (μm), P1 The thickness of the P1 layer is preferably 0.5 μm or more. By making the thickness of the P1 layer 0.5 μm or more, particles can be incorporated into the P1 layer as described above, making it easier to control the surface shape of the A surface by plasma treatment using atmospheric pressure glow discharge. The upper limit of the thickness of the P1 layer is preferably 2.5 μm or less, from the viewpoint of suppressing a decrease in the overall optical properties of the film. (The opposite side from side A: side B) In the polyester film of the present invention, if the surface opposite to surface A is designated as surface B, the maximum protrusion height SpB (nm) obtained by scanning white light interference microscopy measurement of surface B, as described later, is preferably greater than SpA (nm) and between 50 and 200.

[0023] The maximum protrusion height SpB(nm) of the B surface is a parameter that represents the surface roughness with high protrusions present on the B surface, corresponding to the formation of protrusions on the B surface. By setting SaB(nm) to 50 or more, the winding performance of the roll can be improved when the number of protrusions on the A surface is set to the preferred configuration described above, and wrinkle formation can be suppressed when the film roll is wound at high speed. This is because when the A surface and the B surface come into contact during roll winding, the high protrusions on the B surface receive the surface irregularities of the A surface, creating minute gaps. Suppression of roll wrinkles during winding can be improved by increasing the maximum protrusion height SpB(nm) of the B surface. Furthermore, by setting the maximum protrusion height SpB(nm) of the B surface to 200 or less, when a resist layer is provided on the B surface and resist exposure is performed from the A surface side, the occurrence of pinhole defects caused by the presence of coarse protrusions on the B surface can be suppressed.

[0024] (Layer with side B: P2 layer) In order to control the maximum protrusion height SpB (nm) of the B-plane in the biaxially oriented polyester film of the present invention to a preferred range, it is preferable that the layer having the B-plane (P2 layer) contains particles having a specific particle size at a specific concentration.

[0025] Specifically, it is preferable that the P2 layer contains two or more particles of different sizes, and that when the particle count-based particle size distribution measurement described later is performed on the particles contained in the P2 layer, and the secondary particle diameter is plotted on the horizontal axis and the particle abundance ratio on the vertical axis, there are at least two peaks in the region where the secondary particle diameter is 100 nm or more and less than 700 nm. More preferably, there is at least one peak in the region of 100 nm or more and less than 250 nm and the region of 250 nm or more and less than 700 nm, and even more preferably, there is at least one peak in the region of 100 nm or more and less than 250 nm and the region of 250 nm or more and less than 700 nm. Furthermore, it is preferable that the P2 layer does not contain particles in the region of 700 nm or more when the particle count-based particle size distribution measurement is performed.

[0026] Regarding the particle content contained in the P2 layer, it is preferable that the concentration of the particle having the smallest secondary particle size peak among the contained particles between 100 nm and less than 700 nm is between 0.02% by mass and 1.0% by mass. Furthermore, it is preferable that the concentration of the particle having the largest particle size peak among the contained particles between 100 nm and less than 7000 nm is between 0.005% by mass and 0.1% by mass. By setting the above range, it is possible to set the SpB within a preferred range, thereby suppressing pinhole defects in the resist wiring of the polyester film of the present invention while improving the winding properties of the film roll. As particles to be contained in the P2 layer, inorganic particles and organic particles as exemplified for particles to be contained in the P1 layer can be used.

[0027] The thickness of the P2 layer in the polyester film of the present invention is T P2 When T is set to (μm), P2 It is preferable that the thickness of the P2 layer be between 0.4 μm and 1.0 μm. By making the thickness of the P2 layer 0.4 μm or more, it becomes easier to control the surface shape of the B surface, and by making the thickness of the P2 layer 1.0 μm or less, it is possible to suppress the deterioration of the optical properties of the entire film.

[0028] (Middle layer: P3 layer) The biaxially oriented polyester film of the present invention may have a P3 layer between the P1 layer having the A-plane and the particle-containing layer (P2 layer). For example, when the P1 layer contains particles, it is preferable to have a three-layer configuration of P1 / P3 / P2 layers, 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, when 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 configuration of P1 / P3 / P2 layers, 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.

[0029] (Biaxially oriented polyester film) The biaxially oriented polyester film of the present invention, due to its biaxial orientation, has improved mechanical strength, 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. The biaxially oriented polyester film of the present invention has a dimensional shrinkage rate in the width direction after heating at a temperature of 150°C for 30 minutes, obtained by the method described later, which is L 150℃ (%), L 150℃ The percentage (%) is between -0.5 and 0.5. Dimensional shrinkage rate L 150℃ The value (%) reflects the amount of dimensional shrinkage that occurs when the biaxially oriented polyester film of the present invention is exposed to high temperatures, due to the relaxation of the orientation of polyester molecules within the film. This value represents the degree of molecular orientation of the biaxially oriented polyester film and affects the occurrence of laminate wrinkles when a resist layer is applied and pressure and adhesion are performed on a metal substrate using a high-temperature laminating roll, due to the thermal dimensional change (thermal shrinkage) of the film, which prevents uniform pressure from being applied by the laminating roll. Dimensional shrinkage rate L 150℃ By setting the (%) to 0.5 or less, the thermal dimensional stability of the film is improved, and the occurrence of lamination wrinkles becomes less likely. 150℃ By setting the (%) to -0.5 or higher, the reduction in strength due to poor orientation of the biaxially oriented polyester film can be suppressed, and the occurrence of film tearing in the width direction during processing under tension can be suppressed. From a similar viewpoint, the dimensional shrinkage rate L 150℃ A more preferable range for (%) is -0.5% to 0.2%. In the biaxially oriented polyester film of the present invention, when the intrinsic viscosity (IV) of the entire film is IV (dl / g), it is preferable that IV (dl / g) is 0.55 or more and 0.80 or less. Setting IV (dl / g) to 0.55 or less improves the mechanical properties in the stretching film-forming process and suppresses the reduction in film yield due to film tearing. Setting IV to 0.8 or less suppresses extrusion defects in the melt extrusion process.

[0030] 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. 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 0.5 or more and 1.3 or less. By setting the static friction coefficient (μs) of both sides of the film to 0.5 or more, excessive sliding of the films against each other during roll winding can be suppressed, and friction with the high-temperature laminating roll is reduced during the process of applying a resist layer and laminating with a metal plate, thereby suppressing the occurrence of lamination wrinkles. By setting the static friction coefficient (μs) of both sides of the film to 1.3 or less, the adhesion between both sides of the film during roll winding can be suppressed, preventing wrinkles from forming and deterioration of the winding appearance. A more preferable range for the static friction coefficient is 0.6 or more and 1.2 or less, and an even more preferable range is 0.7 or more and 1.1 or less. 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.

[0031] (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.

[0032] 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.

[0033] 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, extruded from a die onto a cooled cast drum, and processed into 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 process it into a sheet (solution casting method).

[0034] 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.

[0035] 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).

[0036] (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.

[0037] Preferably, the obtained uniaxially oriented film, stretched in the longitudinal direction, is guided to a tenter while both ends are held with clips, and stretched by 3 to 5 times in a direction perpendicular to the longitudinal direction (width direction) in an atmosphere heated to a temperature of 70°C to 160°C. 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 the resin melting point -5°C. By setting the heat treatment temperature to 200°C or higher, the orientation of the biaxially oriented polyester film is relaxed while promoting crystal growth, resulting in a film with excellent mechanical properties. Furthermore, by setting the heat treatment temperature to 250°C or lower, the occurrence of film tearing due to the melting of the polyester film is suppressed, and production can be carried out with high productivity. A more preferable range is between 220°C and 235°C.

[0038] 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 230°C. Furthermore, to impart dimensional stability after heat treatment, it is preferable to perform a relaxation treatment at a temperature lower than the heat treatment temperature, in the range of 1% to 6%. By performing a relaxation treatment of 1% or more, the dimensional stability when using biaxially oriented polyester film in a high-temperature environment can be improved, and by performing it at 6% or less, an appropriate tension can be continuously applied to the biaxially oriented polyester film, preventing the deterioration of thickness unevenness. In addition, it is preferable to set the temperature during the relaxation treatment to 150°C to 220°C. By setting the temperature during the relaxation treatment to 150°C or higher, it is possible to suppress thermal shrinkage during pressing with high-temperature rolls in the lamination process, thereby suppressing the occurrence of wrinkles during lamination, and by setting the temperature to 220°C or lower, it is possible to suppress excessive crystallization of the film, thereby suppressing film tearing in the lamination process where tension is applied during transport and processing. 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.

[0039] [Method for evaluating characteristics] A. 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 and setting the measurement mode to WAVE mode, 90 fields of view measurements are taken with 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 results of each measurement is taken as the number of protrusions on that sample. Furthermore, the sample film to be measured is sandwiched between two metal frames containing rubber gaskets, ensuring that the film is taut within the frames (eliminating any sagging or curling of the sample) before measuring the sample surface.

[0040] 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.

[0041] (Image processing conditions) Image processing is performed in the following order. • Interpolation process: Full interpolation • Filtering: Median (3x3 pixels) • Surface correction: 4th order.

[0042] (i) Arithmetic mean surface roughness (SaA) Scanning white-light interference microscopy measurements were performed on the surface (A surface) of the laminated polyester film over 90 fields of view. For each measurement image processed as described above, the arithmetic mean surface roughness Sa (nm) was obtained by selecting "Height Parameters" along with the following analysis conditions in the "ISO Parameter" analysis within the surface analysis software and outputting the resulting numerical values ​​to the parameter sheet. The average value of the 90 fields of view was defined as the arithmetic mean surface roughness SaA (nm) of the measured surface. (ISO parameter analysis conditions) ISO parameter analysis will be performed under the following conditions. • S-Filter: Automatic Regular probability paper Number of divisions: 300 Upper limit of calculation range: 3.000 Lower limit of calculation range: -3.000 • Parameters: Select only "Height Parameters" • Output: Select "Parameter List" (Parameter sheet output) By selecting "Height Parameters" in the "ISO Parameters" window displayed by the above ISO parameter analysis and clicking "Add to Parameter Sheet," the "Sa[μm]" displayed in the "ISO Parameters" tab of the "Parameter Sheet" window can be converted to nm units and used. (ii) Maximum projection height (SpA, SpB) Microscopic observation of the surface (surface A) is performed for 90 fields in the same manner as in (i) above. For each measurement image after the image processing described above, the maximum protrusion height Sp (nm) is determined from the value obtained by converting the "Peak [μm]" displayed in the "ISO Parameters" tab of the "Parameter Sheet" window to nm units, and the average value of the 90 fields is taken as the maximum protrusion height SpA (nm) of the surface (surface A). Similarly, microscopic observations are performed on surface B, which is the opposite surface to surface A, for 90 fields of view. The maximum protrusion height Sp(nm) for each measurement image after the aforementioned image processing is determined, and the average value of the 90 fields of view is taken as the maximum protrusion height SpB(nm) of the surface (surface B).

[0043] (iii) 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 )

[0044] 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 ) (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 μm³ Aspect ratio: r≧0.0000 Histogram: Number of divisions: 50 (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.

[0045]

number

[0046] • 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): Height at each image point (x,y) in the measured image after the image processing described above. (iv) Number of protrusions with a height of 10 nm or more (N 10nm A) In the same manner as in item (iii) above, perform particle analysis processing on the surface (surface A), and change the "height threshold setting value" in the "particle analysis conditions" for each measurement field to 0.01 μm (R 10nm The number of particles (particles) displayed on the "particle analysis" screen, which is detected by ) is divided by the measurement area (113 μm × 113 μm) to determine the number of protrusions (particles / mm²) with a height of 10 nm or more. 2 )

[0047] 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 10 nm or taller. 10nm A (pieces / mm 2 )

[0048] B. Dimensional shrinkage rate in the width direction L 150℃ (%) A 10mm x 150mm rectangle was cut from a biaxially oriented polyester film in both the longitudinal and width directions to form a sample. Markings were drawn on the sample at 100mm intervals, and a 2.1g weight was suspended from it. The sample was then placed in a hot air oven heated to 150°C for 30 minutes for heat treatment. The distance between the markings after heat treatment was measured, and the thermal shrinkage rate was calculated from the change in the distance between the markings before and after heating, serving as an indicator of dimensional stability. Measurements were performed on 5 samples in both the longitudinal and width directions for each film, and the average value was used for sample L. 150℃ It is used as a percentage (%).

[0049] C. 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). (ii) Lamination thickness (T P1 , T P2 , 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.

[0050] D. 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: 120mm Measurement speed: 210mm / min.

[0051] E. Slipperiness with metal plates After conditioning the biaxially oriented polyester film of the present invention at 23°C and 65%RH, two rectangular pieces measuring 65mm in width and 120mm in length are cut out as samples, with the film formation line direction being the longitudinal side. These samples are then measured using a friction tester (manufactured by Toyo Seiki Co., Ltd.) under a 23°C, 65%RH atmosphere. A rectangular sample is placed on the measuring sample stage of the apparatus so that the pulling direction of the apparatus is in the longitudinal direction of the rectangular sample, and side A is facing upwards (not in contact with the sample stage). The sample is then secured to the sample stage with tape. A metal sample plate is attached to one side of a thread connected to the load detection U-gauge of the apparatus, and the metal plate surface is set so that it overlaps with side A of the fixed sample. The total load of the metal plate and thread is 200g. A weight with a load of 1kg is placed on top and left for 20 seconds to allow side A of the sample and the surface of the metal plate to adhere closely together. Then, the maximum load (in Newtons; N) detected when the thread with the metal plate attached is pulled under the following conditions is measured. Seven measurements are taken, and the average of the five measurements, excluding the highest and lowest values, is used as the slipperiness of the sample with respect to the metal plate. (metal plate) Material: Stainless steel Surface roughness: Arithmetic mean roughness 0.012 μm (Measurement conditions) Measurement distance: 70mm Measuring speed: 100mm / min.

[0052] F. 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). (ii) Intrinsic viscosity of the P1 layer (IV P1 ) In the 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) The intrinsic viscosity of the particle master pellet used to form the P1 layer (IV MP ) Regarding the particle master pellets used as raw material for the P1 layer, the intrinsic viscosity of the particle master pellets is determined in the same manner as in item (i) above. MP ) was obtained. (iv) The intrinsic viscosity of the polyester resin used to construct the P1 layer (IV MP ) Regarding the polyester resin used as the raw material for the P1 layer, the intrinsic viscosity of the polyester resin is determined in the same manner as in item (i) above. PET ) was obtained. (v) Intrinsic viscosity of biaxially oriented polyester film (IV) The biaxially oriented polyester film of the present invention was measured in the same manner as in item (i) above to obtain the intrinsic viscosity (IV) of the biaxially oriented polyester film.

[0053] (vi) 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).

[0054] G. Evaluation of contained particles (i) Particle observation 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, P2, or P3 layers were observed at 10,000 to 100,000 times magnification using a TEM (transmission electron microscope: Hitachi H7100FA model) as described below to obtain cross-sectional images containing particles.

[0055] Measurement equipment: Transmission electron microscope (TEM), Hitachi H-7100FA model. Measurement conditions: Acceleration voltage 100kV Measurement magnification: 10,000 times to 100,000 times Sample preparation: Ultrathin film sectioning method (RuO4 staining).

[0056] (ii) Particle size distribution analysis (secondary particle peak diameter D2) The particle size distribution of particles present in the P1, P2, or P3 layers was determined from the cross-sectional images obtained by the method described in (i) above 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 each particle was measured for more than 400 particles present in the cross-sectional images. For the obtained equivalent circle diameters of the particles, a number-based particle size distribution measurement was performed with the horizontal axis representing particle diameter (equivalent circle diameter) and the vertical axis representing the particle abundance ratio. Here, the particle diameter (equivalent circle diameter) that forms the horizontal axis in the number-based particle size distribution is expressed in classes at 10 nm intervals starting from 0 nm (particles with a particle diameter greater than 0 nm and less than or equal to 10 nm are included in the 10 nm class, and particles with a particle diameter greater than 10 nm and less than or equal to 20 nm are included in the 20 nm class, and their abundance ratios are plotted). From the obtained particle size distribution chart, the particle diameter (equivalent circle diameter) of the peak top showing the maximum is defined as the secondary particle peak diameter D2 (nm). In this case, if aggregated particles consisting of multiple connected particles are observed, the aggregated particle is treated as a single particle, its equivalent circle diameter is determined, and the number-based particle size distribution measurement is performed. When a biaxially oriented polyester film contains two or more types of particles with different particle sizes, the above particle size distribution based on particle count will have a distribution with two or more peaks. In this case, the value of each peak is taken as the secondary particle peak diameter of each particle.

[0057] (iii) Primary particle peak diameter D1 In the same manner as described in (i) and (ii) above, the cross-section of the biaxially oriented polyester film of the present invention is observed using a transmission electron microscope (TEM) at a magnification of 200,000 to 800,000 times to obtain a cross-sectional image. For 400 particles present in the cross-sectional image, the equivalent circle diameter of each constituent particle is determined, and the particle size distribution measurement is performed in the same manner as in item (ii) above, and the particle diameter (equivalent circle diameter) of the peak top showing the maximum is defined as the primary particle peak diameter D1 (nm). In this case, if aggregated particles consisting of multiple connected particles are confirmed, the equivalent circle diameter of each particle constituting the aggregated particle (the smallest particle that cannot be further divided) is determined, and the particle size distribution measurement is performed using that value. When a biaxially oriented polyester film contains two or more types of particles with different particle sizes, the above particle size distribution based on particle count will have a distribution with two or more peaks. In this case, each peak value is taken as the primary particle peak diameter of each particle.

[0058] (iv) Particle content concentration A 1g sample, obtained by scraping only the P1 layer portion of the biaxially oriented polyester film of the present invention, was placed in 200ml of 1N-KOH methanol solution and heated under reflux to dissolve the polymer. After dissolution, 200ml of water was added to the solution, and the liquid was centrifuged to settle the particles, and the supernatant was removed. The particles were then washed with water and centrifuged twice. The particles obtained in this way were dried, and their mass (g) was measured to calculate the concentration (mass%) of the particles contained in the P1 layer portion of the biaxially oriented polyester film. If organic particles are present in the contained particles, a solvent that dissolves the polymer but not the organic particles was selected. The polymer was dissolved without superheating or refluxing, and the particles were centrifuged to calculate the particle content (mass%) in the P1 or P2 layer. Whether the contained particles are organic or inorganic can be confirmed by observing the particles using commonly known methods such as SEM-EDX, and checking for the presence or absence of inorganic substances.

[0059] [Method for evaluating application characteristics] H. Winding ability (i) Evaluation of wrinkles The biaxially oriented polyester film of the present invention was fabricated at a speed of 100 m / min or more, and then slit to a width of 1000 mm at a speed of 130 m / min or more. Ten consecutive 4000 m slit roll windings were performed. The winding wrinkles of the resulting 10 film slit rolls were evaluated as follows.

[0060] A: Out of 10 rolls, one or fewer rolls have wrinkles. B: Of the 10 rolls, 2 to 3 rolls have wrinkles or creases. C: Of the 10 rolls, 4 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. (ii) Evaluation of winding misalignment The occurrence of winding misalignment in the 10 film slit rolls obtained in the previous section (i) was evaluated as follows.

[0061] 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.

[0062] I. Dry Film Resist Suitability Evaluation (i) Create resist wiring pattern The photoresist will be evaluated using projection exposure according to the following methods a. to c. a. A photosensitive resin layer is applied to the side (side B) of the biaxially oriented film of the present invention opposite to side A by gravure coating in a darkroom to a coating thickness of 15 μm. The photosensitive resin layer is a mixture consisting of a copolymer polymer of methacrylic acid, methyl methacrylate, ethyl acrylate, and butyl methacrylate as thermoplastic resins, trimethylolpropane triacrylate and polyethylene glycol (number average molecular weight 600) dimethacrylate as photosensitive materials, benzophenone and dimethylaminobenzophenone as photopolymerization initiators, hydroquinone as a stabilizer, and methyl violet as a colorant. b. The laminate consisting of the obtained film of the present invention and the photosensitive resin layer is placed on top of a 6-inch Si wafer that has been mirror-polished on one side, and laminated using a rubber roller. A reticle patterned with chromium metal is placed on top of it, and projection exposure is performed from the reticle (from the A-side of the biaxially oriented polyester film of the present invention) 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 photosensitive resin layer, the photosensitive resin layer is placed in a container containing developer 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. (ii) Evaluation of the shape of the micro-wiring resist 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 shape of the fine wiring resist of the film is evaluated as follows. A: The number of missing pieces is 3 or less. B: The number of missing pieces is between 4 and 7. C: The number of missing pieces is between 8 and 10. D: The number of missing pieces is 11 or more. In terms of evaluating the shape of the fine wiring resist, A to C are good, with A being the best among them. (iii) Pinhole defects in fine wiring 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 pinhole defect evaluation of the film is evaluated as follows. A: Number of pinhole defects: 0 B: The number of pinhole defects is between 1 and 5. C: The number of pinhole defects is between 6 and 10. D: The number of pinhole defects exceeds 10. For evaluating pinhole defects in fine wiring, A to C indicate good performance, with A being the best.

[0063] J. Laminate Suitability Assessment Using the method described in Section H above, a laminated roll measuring 1000m in length and 1500mm in width, having a photosensitive resin layer on the B-side of a biaxially oriented polyester film, is laminated onto a metal substrate having copper foil on its surface heated to approximately 50-60°C via a roll-to-roll process. For the lamination, a silicone rubber roll heated to 100°C is used to clamp the laminate from both sides under a pressure of 0.5MPa, causing the surface of the photosensitive resin layer in the laminate and the surface of the copper foil on the metal substrate to adhere to each other through heat. The transport speed of the apparatus is 5m / min. (i) Evaluation of tearing of the process film When laminating a laminate consisting of a biaxially oriented polyester film, a photosensitive resin layer, and a metal substrate, the process tear evaluation is performed as follows based on the number of times the film tears during the process. A: Film does not tear. B: Film tearing occurred once per 1000m. C: Film tearing occurred 2 to 3 times per 1000m. D: Film tearing occurred 4 times or less per 1000m. In terms of process failure evaluation, A to C indicate good performance, with A being the best. (ii) Evaluation of defects in metal rolls during the process The surface of the laminated structure, consisting of a biaxially oriented polyester film, a photosensitive resin layer, and a metal substrate, is checked for surface scratches, and the process metal roll scratch evaluation is performed as follows. A: No surface scratches will occur. B: Surface scratches occur at a rate of 1 to 5 times per 1000m. C: Surface scratches occur 6 to 10 times per 1000m. D: Surface scratches occur more than 10 times per 1000m. In terms of laminate wrinkle evaluation, A to C indicates good quality, with A being the best. (iii) Laminate wrinkle evaluation The presence or absence of wrinkles on the surface of the laminated structure, consisting of a biaxially oriented polyester film, a photosensitive resin layer, and a metal substrate, is checked, and the laminate wrinkle evaluation is performed as follows. A: No lamination wrinkles occur. B: Laminate wrinkles occur 1 to 5 times per 1000m. C: Laminate wrinkles occur 6 to 10 times per 1000m. D: Laminate wrinkles occur more than 10 times per 1000m. In terms of laminate wrinkle evaluation, A to C indicates good quality, with A being the best. [Examples]

[0064] The present invention will be described below with reference to examples, but the present invention is not necessarily limited to these examples.

[0065] [Preparation of PET-1] Terephthalic acid and ethylene glycol were polymerized using antimony trioxide as a catalyst by a conventional method to obtain a melt-polymerized PET that is substantially particle-free. 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. Subsequently, the obtained polyester pellets were dried at 160°C for 6 hours to crystallize, and then solid-phase polymerization was carried out at 220°C under a vacuum of 0.3 Torr for 8 hours to obtain solid-phase polymerized PET (PET-1). The glass transition temperature of the obtained solid-phase polymerized PET was 81°C, the melting point was 255°C, and the intrinsic viscosity was 0.54. [Preparation of PET-2] In the same manner as in the previous section [Preparation of PET-1], solid-phase polymerized PET resin pellets (PET-2) with a glass transition temperature of 81°C, a melting point of 255°C, and an intrinsic viscosity of 0.64 were obtained. [Manufacturing of MB-A] During the polymerization of PET-2 as described above, alumina particles (alumina-1) with a primary particle size of 20 nm, dispersed in ethylene glycol, were added in an amount of 2% by mass relative to the PET to obtain particle master pellet MB-A. The obtained particle master pellet MB-A had a glass transition temperature of 80°C, a melting point of 255°C, and an intrinsic viscosity of 0.60. [Production of MB-B~F] In the same manner as in the previous section [Production of MB-A], particles dispersed in ethylene glycol as shown in Table 1 were added to the polymerization of PET-2 in the amount shown in Table 1 relative to the PET, thereby obtaining particle master pellets MB-B~F. The properties of the particle master pellets were as shown in Table 1.

[0066] [Table 1]

[0067] (Example 1) PET resin pellets PET-1 and PET-2, and particle master pellets MB-A to D were dried under reduced pressure at 180°C for 2.5 hours. The mixtures were then blended to the amounts of P1, P2, and P3 layers as shown in Table 2. These mixtures were supplied to three separate extruders, melt-extruded, filtered, and then combined in a feed block to form three layers (P1 / P3 / P2 layers). The mixtures were then wound onto a cooling cast roll maintained at 35°C via a T-die using an electrostatic casting method and cooled and solidified to obtain an unstretched film. This unstretched film was guided between opposing electrodes and an earth roll, nitrogen gas was introduced into the apparatus, and the processing strength (E value) reached 250 W·min / m2 Under these conditions, plasma treatment was performed on the surface of the P1 layer using atmospheric pressure glow discharge.

[0068] After processing, the unstretched film was 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 3. First, it was guided to a group of stretching rolls heated to 60°C to 100°C in the longitudinal direction and stretched to a total of 3.6 times its original length by the stretching operation. Then it was guided to a tenter and stretched to a total of 3.8 times its original length in the width direction. After heat treatment at a constant length of 235°C and a 3% relaxation treatment in the width direction, a biaxially oriented polyester film with a thickness of 16 μm was obtained.

[0069] [Table 2]

[0070] [Table 3]

[0071] The composition, film properties, surface properties, and thermal properties of the obtained biaxially oriented polyester film are shown in Tables 4 and 5.

[0072] [Table 4]

[0073] [Table 5]

[0074] As shown in Table 6, the film exhibited good suitability for production and application, including good roll winding properties, lamination suitability, and dry film resist suitability.

[0075] [Table 6]

[0076] (Examples 2-5) In Examples 2-5, a biaxially oriented polyester film with a thickness of 16 μm was obtained in the same manner as in Example 1, except that the formulation of particles contained in the P1 layer was changed as shown in Table 2. The composition, film properties, surface properties, thermal properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Tables 4-6. In Example 2, surface scratches during the lamination process were worse than in Example 1; in Example 3, the shape of the fine wiring resist was worse; in Example 4, the shape of the fine wiring resist, pinhole defects, and film roll misalignment were worse; and in Example 5, film roll wrinkles and surface scratches during the lamination process were worse than in Example 1. However, these were all within the range of practical use, and otherwise the films were as good as in Example 1. (Examples 6 and 7) In Examples 6 and 7, a biaxially oriented polyester film with a thickness of 16 μm was obtained in the same manner as in Example 1, except that the temperature during the relaxation treatment was changed as shown in Table 3. The composition, film properties, surface properties, thermal properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Tables 4 to 6. In Example 6, lamination wrinkles during the lamination process worsened compared to Example 1, and in Example 7, film tearing during the lamination process worsened compared to Example 1, but these were still within the range of practical use. Otherwise, the films were of good quality, similar to Example 1. (Examples 8 and 9) In Examples 8 and 9, a biaxially oriented polyester film with a thickness of 16 μm was obtained in the same manner as in Example 1, except that the formulation of particles contained in the P1 layer was changed as shown in Table 2, and the treatment intensity of the atmospheric pressure glow discharge treatment applied to the surface of the P1 layer was changed as shown in Table 3. The composition, film properties, surface properties, thermal properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Tables 4 to 6. In Example 8, the film roll misalignment and the shape of the fine wiring resist were worse than in Example 1, and in Example 9, the film roll wrinkles and surface scratches during the lamination process were worse than in Example 1, but these were still within the range of practical use. Otherwise, the film was of good quality, similar to Example 1.

[0077] (Examples 10, 11) In Examples 10 and 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 particles contained in the P2 layer were changed as shown in Table 3. The composition, film properties, surface properties, thermal properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Tables 4 to 6. In Example 10, the shape of the fine wiring resist and pinhole defects were worse than in Example 1, and in Example 11, the wrinkles during roll winding 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.

[0078] (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 did not contain particles. The composition, film properties, surface properties, thermal properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Tables 4 to 6. Comparative Example 1 was a film that exhibited significantly worse wrinkles during roll winding and surface scratches during the lamination process compared to Example 1.

[0079] (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 P1 layer was not subjected to atmospheric pressure glow discharge treatment (plasma treatment). The composition, film properties, surface properties, thermal properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Tables 4 to 6. Comparative Example 2 was a film that showed significantly worse wrinkles during roll winding and surface scratches during the lamination process compared to Example 1. (Comparative Example 3) 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 formulation of particles contained in the P1 layer was changed as shown in Table 2. The composition, film properties, surface properties, thermal properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Tables 4 to 6. Comparative Example 3 resulted in a film with significantly inferior characteristics compared to Example 1, in terms of fine wiring resist shape, pinhole defects, and winding misalignment during roll winding. (Comparative Examples 4 and 5) In Comparative Examples 4 and 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 temperature during the relaxation treatment was changed as shown in Table 3. The composition, film properties, surface properties, thermal properties, production suitability, and application suitability of the obtained biaxially oriented polyester film are shown in Tables 4 to 6. In Comparative Example 4, the film exhibited significantly worse lamination wrinkles during the lamination process compared to Example 1, and in Comparative Example 5, the film exhibited significantly worse film tearing during the lamination process compared to Example 1. [Industrial applicability]

[0080] The biaxially oriented polyester film of the present invention has a surface on one side of the film with protrusions of controlled height, and by controlling the thermal shrinkage of the film, it exhibits excellent process transportability and lamination processability in the lamination process, as well as high transparency and good optical properties, making it suitable for use as a support film for dry film resists for fine wiring. [Explanation of symbols]

[0081] 1. Layer having surface A (P1 layer) 2. Surface with protrusions (Surface A) 3. Zero plane (average plane; height 0 nm) in scanning white light interference microscopy measurements 4. 10 nm high line (R) in scanning white light interference microscopy measurements 10nm ) 5. 50 nm height line (R) in scanning white light interference microscopy measurements. 50nm ) 6. Protrusions present on surface A 7. Coating layer having side B (P2 layer) 8. The opposite side from side A (side B) 9.2-layer (P1 layer / P2 layer) biaxially oriented polyester film 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 for a dry film resist support, having a surface with protrusions (surface A) on one side, satisfying the following requirements (1) to (3), and wherein, when the maximum protrusion height of the opposite surface (surface B) of surface A is SpB (nm), SpB is greater than SpA and is between 50 and 200. (1) When the maximum protrusion height of surface A is defined as SpA (nm), SpA is 30 or more and 80 or less. (2) The dimensional shrinkage rate in the width direction after heating the biaxially oriented polyester film at a temperature of 150°C for 30 minutes is L １５０℃ (%) If L １５０℃ (%) is between -0.5 and 0.5 (3) When the layer constituting surface A (P1 layer) contains particles, and the particle size distribution is measured based on the number of particles, and the secondary particle diameter is plotted on the horizontal axis and the particle abundance ratio is plotted on the vertical axis, at least one peak (secondary particle peak diameter D) is found in the region where the secondary particle diameter is 100 nm or more and 250 nm or less. ２ It has (nm) and does not have a peak in the region where the secondary particle diameter exceeds 250 nm.

2. The biaxially oriented polyester film for a dry film resist support according to claim 1, wherein the arithmetic mean surface roughness of surface A is SaA (nm), and SaA is 1.6 or more and 4.5 or less.

3. The number of protrusions on surface A with a height of 50 nm or more is N ５０ｎｍ A (pieces / mm ２ If we consider N ５０ｎｍ A biaxially oriented polyester film for dry film resist support according to claim 1 or 2, wherein A is 20 or more and 350 or less.

4. Let the number of protrusions with a height of 10 nm or more on the A side be N １０ｎｍ A (pieces / mm ２ ) When it is, N １０ｎｍ The biaxially oriented polyester film for a dry film resist support according to any one of claims 1 to 3, wherein A is 6,000 or more and 50,000 or less.

5. In the measurement of the particle size distribution based on the number of particles contained in the P1 layer, the secondary particle peak diameter D ２ Particles with a (nm) of 100 to 250 have a primary particle peak diameter D １ A biaxially oriented polyester film for a dry film resist support according to any one of claims 1 to 4, wherein aggregated particles are formed by the aggregation of multiple particles having a (nm) of 10 to 160.

6. The biaxially oriented polyester film for a dry film resist support according to any one of claims 1 to 5, wherein the concentration of particles contained in the P1 layer is 0.01% by mass or more and 1.0% by mass or less of the entire P1 layer.

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