Biaxially oriented polyester film

Abstract

[Problem] To provide a biaxially oriented polyester film having a smooth release surface which suppresses roughness of a release layer caused by surface shape after winding into a roll by having highly smooth surfaces on both sides. [Means for solving the problem] A biaxially oriented polyester film, in a case where a value of the maximum protrusion height belonging to the top 5% of values of the maximum protrusion height in each field of view obtained by the following method is respectively denoted as Sp5% A (nm), Sp5% B (nm) in one side (A side) and the other side (B side) thereof, Sp5% A is 110 or less, Sp5% B is 150 or more and 1000 or less. (Maximum protrusion height measurement method) Using a scanning white light interference microscope (VertScan), using a 10 times objective lens, a surface image of a 561 μm square field of view is measured in 100 fields of view, a value of the maximum protrusion height Sp in each field of view is found, and a value belonging to the top 5% of these SP values is taken as Sp5% value.

Description

Technical Field

[0001] This invention relates to a biaxially oriented polyester film, which has surfaces with specific characteristics on both sides of the film. Background Technology

[0002] Thermoplastic resins are used in various industrial fields due to their good processability. Furthermore, products made by processing these thermoplastic resins into films play an important role in modern life, including industrial applications, optical products, packaging, and magnetic recording tapes. In recent years, the miniaturization, refinement, and high integration of electronic information equipment have led to increased demands on the process films used in the manufacturing processes of these devices, requiring improved processability.

[0003] The demand for release films used in electronic component manufacturing, especially in the rapidly developing process of multilayer ceramic capacitor manufacturing, is constantly increasing. A green sheet is a thin-film ceramic obtained by coating a ceramic slurry onto a release film and then drying it. In the release process, the surface smoothness of the release film becomes important. This is because if the unevenness of the release surface is transferred to the green sheet surface, defects arising from this unevenness will occur in subsequent green sheet stacking processes.

[0004] However, regarding the surface of the release layer, the surface roughness is caused by the propagation of the uneven shape of the substrate film surface. When the film is wound into a roll, the surface shape of the side opposite to the release surface is transferred to the release surface, making it difficult to maintain its surface smoothness. In particular, as the thickness of the green sheet for the next generation is reduced to 0.5 μm, it is necessary to maintain the smoothness of the release surface before and after winding.

[0005] To address such issues, for example, Patent Document 1 discloses a method that controls the surface roughness of both sides by controlling the particle size contained in the film, thereby suppressing the transfer of unevenness to the green sheet.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2015-208939 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] However, in Patent Document 1, the high particle content is insufficient for next-generation applications.

[0011] The purpose of this invention is to provide a biaxially oriented polyester film that, by controlling the height of the protrusions on both sides of the film and creating a highly smooth surface, not only exhibits excellent coating and peelability of the green sheet stacked with a release resin coating layer during sheet formation, but also significantly suppresses surface defects and sheet breakage caused by the transfer of uneven shapes to the green sheet. Furthermore, by controlling the particle size and stacking thickness of the particles contained in the film, the aforementioned surface smoothness, process transportability (suppression of surface damage defects and surface scraping), and winding properties (winding wrinkles and winding misalignment) are maintained even when using recycled resin raw materials as film raw materials.

[0012] Methods for solving problems

[0013] To solve the above-mentioned problems, the present invention adopts the following configuration. That is,

[0014] [I] A biaxially oriented polyester film having a surface (A surface) that satisfies the following condition (1), and a surface (B surface) opposite to surface A that satisfies the following condition (2).

[0015] Condition (1): The surface A has a protrusion, and Sp5%A is 110 or less, where the value of the maximum protrusion height that belongs to the top 5% of the values ​​of the maximum protrusion height in each field of view obtained by the following method is denoted as Sp5%A (nm).

[0016] Condition (2): The B-surface has a protrusion, and Sp5%B (nm) is 150 or more and 1000 or less, where the value of the maximum protrusion height that belongs to the top 5% of the values ​​of the maximum protrusion height in each field of view obtained by the following method is denoted as Sp5%B (nm).

[0017] (Method for determining the maximum protrusion height)

[0018] Using a scanning white interference microscope (VertScan) with a 10x objective lens, surface images of a 561 μm square field of view were measured in 100 fields of view. The maximum protrusion height Sp value in each field of view was determined, and the values ​​in the top 5% of these Sp values ​​were taken as the Sp5% values.

[0019] [II] According to the biaxially oriented polyester film described in [I], there are protrusions on the surface of the A side, where the number of protrusions with a height of 80 nm or more is denoted as N. 80nm A (pieces / mm) 2 In the case of N, 80nm A is below 0.4.

[0020] [III] According to the biaxially oriented polyester film described in [I] or [II], there are protrusions on the surface of the A side, and the number of protrusions with a height of 10 nm or more is denoted as N. 10nmA (pieces / mm) 2 In the case of N, 10nm A is between 300 and 1000.

[0021] [IV] The biaxially oriented polyester film according to any one of [I] to [III], wherein the polyester resin layer (P1 layer) is a layer having the A side.

[0022] [V] The biaxially oriented polyester film according to any one of [I] to [IV], wherein the thickness of the P1 layer is denoted as T. P1 In the case of (μm), T P1 It is 2 or more and 10 or less.

[0023] [VI] According to any one of [I] to [V], the biaxially oriented polyester film, wherein the P1 layer contains particles, and the maximum particle size of the particles contained in the P1 layer is denoted as D. P1 In the case of (μm), T P1 / D P1 The value is between 20 and 100.

[0024] [VII] According to the biaxially oriented polyester film described in [I], when the water contact angle of the A side is denoted as CaR (°), CaR is 100 or more and 120 or less.

[0025] [VIII] According to [VII], the biaxially oriented polyester film has a coating layer (R1 layer) having the A side, the coating layer (R1 layer) being disposed on a layer (P1 layer) with the polyester resin as the main component.

[0026] [IX] According to the biaxially oriented polyester film of [VII] or [VIII], the R1 layer is composed of at least one of silicone resin, long-chain alkyl resin and acrylic resin as the main component.

[0027] [X] According to any one of [VII] to [IX], the biaxially oriented polyester film, wherein the thickness of the R1 layer is denoted as T R1 In the case of (μm), T R1 It is above 0.01 and below 1.00.

[0028] [XI] According to any one of [I] to [X], the biaxially oriented polyester film, when the layer having the B side is designated as layer P2, has a configuration of at least three or more layers, such that a particle-containing layer P3 is present between layer P1 and layer P2.

[0029] [XII] According to any one of [I] to [XI], the biaxially oriented polyester film, wherein the P2 layer contains at least two types of particles with different particle sizes.

[0030] [XIII] The biaxially oriented polyester film according to any one of [I] to [XII], wherein the thickness of the P2 layer is denoted as T. P2 (μm), and the maximum particle size contained in the P2 layer is denoted as D. P2 In the case of (μm), T P2 / D P2 It is between 1 and 5.

[0031] [XIV] The biaxially oriented polyester film according to any one of [I] to [XIII] has its film thickness measured in the film width direction (the same direction as the film roll width direction), and the average film thickness is denoted as T. AVE (μm), the maximum value of the film thickness is denoted as T. MAX (μm), and the minimum value is denoted as T. MIN In the case of (μm), the thickness non-uniformity ΔT (%) expressed by the following formula (1) is 5.0 or less.

[0032] ΔT(%)=100×(T MAX -T MIN ) / T AVE ...Formula (1)

[0033] [XV] The biaxially oriented polyester film according to any one of [I] to [XIV] has a static friction coefficient of 0.8 or less between the A-side and the B-side.

[0034] [XVI] The biaxially oriented polyester film according to any one of [I] to [XV] is used as a support film for green sheet forming in the process of manufacturing multilayer ceramic capacitors.

[0035] Invention Effects

[0036] The biaxially oriented polyester film of the present invention has a highly smooth surface on both sides and excellent process transportability (suppression of surface damage defects and surface scraping) and winding ability (suppression of winding wrinkles and winding misalignment). In addition, it can suppress the transfer roughness caused by the uneven shape of the film surface after winding into a roll to the release layer. As a result, not only is the coating and peeling property of the stacked green sheet excellent, but also the cracking and surface defects of the green sheet can be suppressed.

[0037] In addition, the biaxially oriented polyester film of the present invention has good surface smoothness and release properties, and is particularly useful as a support film for green sheet forming in the process of manufacturing multilayer ceramic capacitors. Attached Figure Description

[0038] [ Figure 1 [A conceptual diagram illustrating the determination of Sp5%A using a scanning white interference microscope.]

[0039] [ Figure 2 [A conceptual diagram illustrating the determination of Sp5%B using a scanning white interference microscope.]

[0040] [ Figure 3 [Diagram of the three-layer structure of the biaxially oriented polyester film of the present invention]

[0041] [ Figure 4 [Diagram showing the four-layer structure of the biaxially oriented polyester film with coating layer according to the present invention] Detailed Implementation

[0042] The present invention will now be described in detail.

[0043] This invention relates to biaxially oriented polyester films.

[0044] The biaxially oriented polyester film of the present invention is a biaxially oriented polyester film having a surface (A surface) that satisfies the following condition (1) and a surface (B surface) opposite to surface A surface that satisfies the following condition (2).

[0045] Condition (1): In the above A plane, when the value of the maximum protrusion height belonging to the top 5% of the maximum protrusion heights in each field of view obtained by the following method is denoted as Sp5%A (nm), Sp5%A is 110 or less.

[0046] Condition (2): In the above B plane, when the value of the maximum protrusion height belonging to the top 5% of the maximum protrusion heights in each field of view obtained by the following method is denoted as Sp5%B (nm), Sp5%B is 150 or more and 1000 or less.

[0047] (Method for determining the maximum protrusion height)

[0048] Using a scanning white interference microscope (VertScan) with a 10x objective lens, surface images of a 561 μm square field of view were measured in 100 fields of view. The maximum protrusion height Sp value in each field of view was determined, and the top 5% of these Sp values ​​were taken as the Sp5% value. The detailed measurement method is described later.

[0049] The biaxially oriented polyester film of the present invention comprises a polyester resin layer (P1) having the aforementioned A side, an intermediate layer (P3), and a layer (P2) having a side opposite to the aforementioned A side (B side), preferably composed of a three-layer stack of P1 layer / P3 layer / P2 layer. Alternatively, the biaxially oriented polyester film of the present invention includes a coating layer (R1) having the aforementioned A side, and comprises a polyester resin layer (P1), an intermediate layer (P3), and a layer (P2) having a side opposite to the aforementioned A side (B side), preferably composed of a four-layer stack of R1 layer / P1 layer / P3 layer / P2 layer.

[0050] (Surface with protrusions: Surface A)

[0051] The surface A described above in this invention has protrusions. When the maximum protrusion height, which is among the top 5% of the maximum protrusion heights obtained by the method described later, is denoted as Sp5%A (nm), Sp5%A is 110 or less. In the case where the biaxially oriented polyester film of this invention is used as the process film for the green sheet in the manufacturing process of multilayer ceramic capacitors, Sp5%A reflects the height of the protrusions with uneven shapes transferred to the surface during the coating process of forming a green sheet requiring high smoothness, and affects the number of surface defects in the green sheet monomers and the number of defects in the process of stacking them to manufacture ceramic capacitors. The maximum protrusion height value, Sp5%A (nm), which is among the top 5% of the maximum protrusion heights obtained by the method described later in this invention, is a value measured using software attached to a scanning white interference microscope, based on ISO 25178, by the measurement method described later. By making the Sp5%A (nm) in surface A 110 or less, the number of surface defects on the green wafer, green wafer cracks, and defects in the process of manufacturing ceramic capacitors by stacking green wafers can be reduced. A more preferred range for the Sp5%A (nm) in surface A is 100 or less, and even more preferably 80 or less.

[0052] In this invention, the number N of protrusions with a height of 80 nm or more on surface A is... 80nm A (pieces / mm) 2 Preferably, the value is 0.4 or less, reflecting the number of coarse, uneven protrusions transferred onto the surface of the green sheet during the manufacturing process of multilayer ceramic capacitors, when used as a process film for the green sheet. The number of protrusions corresponding to each height in this invention is a value measured using software attached to a scanning white interference microscope, based on ISO 25178, by the measurement method described later. The number N of protrusions with a height of 80 nm or more is defined as follows. 80nm A (pieces / mm) 2 A value of 0.4 or less can suppress localized damage to the component, and sometimes further reduce the number of surface defects in green wafer monomers, green wafer breakage, and the number of defects in the process of stacking them to manufacture ceramic capacitors. N is the number of protrusions with a height of 80 nm or more mentioned above. 80nm A (pieces / mm) 2 A more preferred range is 0.3 or less, and even more preferably 0.2 or less.

[0053] In this invention, the number N of protrusions with a height of 10 nm or more on surface A is... 10nm A (pieces / mm) 2The value is preferably 300 or more and 1000 or less, which reflects the slippage resistance of surface A and the process rollers in the biaxially oriented polyester film forming process and the manufacturing process of laminated ceramic capacitors. This is achieved by increasing the number N of protrusions with a height of 10 nm or more. 10nm A (pieces / mm) 2 With a value of 300 or less, surface scratches caused by friction with the process rollers can be suppressed, thus preventing a decrease in film quality. Furthermore, by increasing the number N of protrusions with a height of 10 nm or more... 10nm A (pieces / mm) 2 The number of protrusions N, with a height of 10 nm or more, is below 1000, which can suppress winding misalignment during winding. 10nm A (pieces / mm) 2 The preferred range is 400 or more and 1000 or less.

[0054] (The opposite side of side A: side B)

[0055] The surface opposite to surface A (surface B) in this invention has protrusions. When the maximum protrusion height, which is among the top 5% of the maximum protrusion heights obtained by the method described later, is denoted as Sp5%B (nm), Sp5%B is 150 or more and 1000 or less. In the case where the biaxially oriented polyester film of this invention is used as the process film for the green sheet in the manufacturing process of laminated ceramic capacitors, Sp5%B is a value reflecting the height of the protrusions that transfer a raised or recessed shape to the surface of the green sheet or the surface of the laminated green sheet requiring high smoothness during winding. It not only transfers the raised or recessed shape to the surface in contact with the green sheet, but also, due to the partial pressing of the green sheet into the release resin coating layer side, more significantly transfers the raised or recessed shape to the surface of the release resin coating layer, thus affecting the number of surface defects on the green sheet monomers and the number of defects in the process of laminating them to manufacture ceramic capacitors. The Sp5%B (nm) value described above in this invention is determined using software attached to a scanning white interference microscope and is a value measured using the measurement method described later, based on ISO 25178. By setting the Sp5%B (nm) value to 1000 or less, the number of surface defects on the green sheet, green sheet breakage, and defects in the process of manufacturing ceramic capacitors by stacking green sheets can be reduced. A more preferred upper limit for the Sp5%B (nm) value is 700 or less. Furthermore, by setting the Sp5%B (nm) value to 150 or more, the slip properties on both sides of the biaxially oriented polyester film are improved, and the generation of winding wrinkles during winding can be suppressed. A more preferred lower limit for the Sp5%B (nm) value is 180 or more, and even more preferably 200 or more.

[0056] (Polyester resin layer: P1 layer)

[0057] The biaxially oriented polyester film of the present invention has a layer (P1 layer) with polyester resin as the main component. When the surface of the P1 layer is the outermost surface of the biaxially oriented polyester film, the surface of the P1 layer that is the outermost surface is preferably the A-side described above. Hereinafter, the case where the surface of the P1 layer is the outermost surface of the biaxially oriented polyester film and is the A-side described above is sometimes referred to as the A-side of the P1 layer.

[0058] By making the surface of layer P1 the outermost surface of the biaxially oriented polyester film and also the aforementioned surface A, when a coating layer is provided on the surface of layer P1, the maximum height and number of protrusions on the surface of the coating layer can be controlled within a preferred range. In particular, the thickness of the coating layer (R1), described later, is denoted as T. R1 (μm) and T R1 When the value is 0.01 or higher and 0.30 or lower, it is preferable to control the coating layer surface to meet the requirements of the A surface by making the surface of the P1 layer meet the requirements of the A surface.

[0059] (Polyester resin)

[0060] In this invention, the term "biaxially oriented polyester film" refers to a film in which polyester resin is the main component. Here, "main component" means a component contained in an amount greater than 50% by mass out of 100% of the total components of the film.

[0061] Furthermore, the polyester resin referred to in this invention is a resin formed by the condensation polymerization of a dicarboxylic acid constituent and a diol constituent. It should be noted that, in this specification, the term "constituent" refers to the smallest unit that can be obtained by hydrolyzing the polyester.

[0062] Examples of dicarboxylic acid components constituting such polyesters include 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, 4,4'-diphenyl ether dicarboxylic acid, and other aromatic dicarboxylic acids or their ester derivatives.

[0063] In addition, examples of diols constituting 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 cyclohexanediol and spirocyclodiol; and alcohols formed by linking multiple of the above diols together.

[0064] From the viewpoint of mechanical properties and transparency, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene 2,6-naphthalenedicarboxylate (PEN), and polyesters obtained by copolymerizing isophthalic acid and naphthalic acid in a portion of the dicarboxylic acid component of PET, and polyesters obtained by copolymerizing cyclohexanediol, spirocyclodiol, and diethylene glycol in a portion of the diol component of PET, are particularly preferred, among which polyethylene terephthalate is especially preferred.

[0065] The polyester film in the biaxially oriented polyester film of the present invention preferably exhibits biaxial orientation. Due to biaxial orientation, the mechanical strength of the film is improved, thereby reducing wrinkles and improving windability. Furthermore, uniform tensile stress is applied during the stretching process, resulting in uniform surface smoothness throughout the entire film area. Here, biaxial orientation refers to a pattern exhibiting biaxial orientation in wide-angle X-ray diffraction. The polyester film is typically obtained by stretching an unstretched thermoplastic resin sheet along its length and width directions, followed by heat treatment to achieve crystal orientation. This will be described in detail below.

[0066] As a method for ensuring that the Sp5%A (nm) is within the aforementioned range in the A-side of the P1 layer of the present invention, with the aim of decomposing / removing deteriorated foreign matter from the polyester resin present on the surface and thereby reducing coarse protrusions, examples include corona treatment and plasma surface treatment using atmospheric pressure glow discharge. From the viewpoint of suppressing excessive deterioration of the polyester resin constituting the A-side of the P1 layer and the generation of foreign matter due to surface treatment, plasma surface treatment using atmospheric pressure glow discharge is more preferable.

[0067] Plasma surface treatment using atmospheric pressure glow discharge can be performed during the polyester film manufacturing process on the unstretched film after extrusion, or on the stretched film. However, from the viewpoint of imparting smoothness and slip resistance to surface A, it is most preferable to perform plasma surface treatment using atmospheric pressure glow discharge on the unstretched film. This is because, by using plasma surface treatment with atmospheric pressure glow discharge, the amorphous polyester portion can be removed, and in the subsequent stretching process, the remaining crystalline polyester portion on the surface undergoes crystal growth in the form of protrusions, thereby forming fine protrusions on the surface.

[0068] Atmospheric pressure, as referred to here, is in the range of 700 to 780 Torr. In atmospheric pressure glow discharge processing, a membrane to be processed is introduced between opposing electrodes and a grounding roller. A plasma-excited gas is introduced into the device, and a high-frequency voltage is applied between the electrodes, thereby exciting the gas with plasma and causing glow discharge between the electrodes. As a result, the membrane surface is micro-processed (ashed) to form protrusions.

[0069] The term "plasma-excited gas" refers to a gas that can be excited by plasma under the conditions described above. Examples of plasma-excited gases include, for instance, rare gases such as argon, helium, neon, krypton, and xenon, nitrogen, carbon dioxide, oxygen, or fluorocarbons such as tetrafluoromethane, and mixtures thereof. Furthermore, a single plasma-excited gas can be used alone, or two or more can be combined in any mixing ratio. From the viewpoint that the activity increases when excited by plasma, oxygen is preferably included in addition to at least one of argon, oxygen, and carbon dioxide. Furthermore, by using a highly active plasma-excited gas, the number of fine protrusions formed on the film surface can be increased, sometimes further improving slipability.

[0070] The frequency of the high-frequency voltage used in plasma treatment is preferably in the range of 1 kHz to 100 kHz. Furthermore, from the viewpoint of protrusion formation, it is preferable that the discharge treatment intensity (E value) determined using the following method is 50 to 2000 W·min / m. 2 The processing is carried out under conditions within the range of 150–1000 W·min / m², more preferably 150–1000 W·min / m². 2 By increasing the discharge treatment intensity (E value) to 50 W·min / m 2 The above methods can achieve the effect of forming fine protrusions on the surface and reduce the thickness unevenness in the width direction of the biaxially oriented polyester film, as described later, by suppressing the discharge treatment intensity (E value) to 2000 W·min / m. 2 The following method can suppress the formation of surface foreign matter with a height of 80 nm or more due to excessive damage to the surface of the polyester film.

[0071] <Method for determining discharge treatment intensity (E value)>

[0072] E = Vp × Ip / (S × Wt)

[0073] E: E value (W·min / m 2 )

[0074] Vp: Applied voltage (V)

[0075] Ip: Applied current (A)

[0076] S: Processing speed (m / min)

[0077] Wt: Processing width (m)

[0078] Generally, when the surface of polyester film, especially PET and PEN, which have amorphous and crystalline regions, is ashed by atmospheric pressure glow discharge treatment, the ashing begins gradually from the soft amorphous regions. By subdividing the region into crystalline and amorphous parts, finer protrusions can be formed by atmospheric pressure glow discharge treatment. Furthermore, by pre-increasing the crystalline region, the soft amorphous region is deeply scraped away, thereby further increasing the height of the protrusions formed after the stretching process.

[0079] The thickness of the P1 layer of this invention is denoted as T. P1 In the case of (μm), T P1 The thickness (μm) is preferably 2 or more and 10 or less. This is achieved by adjusting the thickness T of the P1 layer described above. P1 With a particle size (μm) of 2 or higher, even when coarse particles are added to the P3 and P4 layers (described later), the influence of the particle shape on the A-surface can be minimized. In particular, regarding the coarse particles added to the P3 and P4 layers (described later), when the particle size at the largest peak in the volumetric particle size distribution analysis (described later) is greater than 800 nm, the influence on the A-surface becomes more significant. Therefore, it is more preferable to have a thickness T of the P1 layer... P1 The value (μm) is set to 3 or more, and more preferably 5 or more.

[0080] In addition, by making the thickness T of the above-mentioned P1 layer P1 With a thickness (μm) of 10 or less, the proportion of the intermediate layer (P3) using the recycled raw material described later can be increased while suppressing the total film thickness. The thickness T of the aforementioned P1 layer... P1 A more preferred range for the upper limit value of (μm) is 8 or less.

[0081] The P1 layer of the biaxially oriented polyester film of the present invention may contain particles and additives such as heat stabilizers, oxidation stabilizers, antistatic agents, organic / inorganic slip agents, nucleating agents, dyes, dispersants, coupling agents, and wavelength conversion materials, within a range that does not impair the effects of the present invention.

[0082] Furthermore, in the P1 layer of the biaxially oriented polyester film of the present invention, particles may be contained in order to control the Sp5%A (nm) in the A-side of the P1 layer, but it is more preferable that the layer does not contain particles.

[0083] There are no particular limitations on the particles added; either inorganic or organic particles can be used, or two or more types of particles can be used in combination. Examples of inorganic particles include calcium carbonate, magnesium carbonate, zinc carbonate, titanium dioxide, zinc oxide, cerium oxide, magnesium oxide, barium sulfate, zinc sulfide, calcium phosphate, aluminum oxide (α-alumina, β-alumina, γ-alumina, δ-alumina), mica, mica titanium dioxide, zeolite, talc, clay, kaolin, lithium fluoride, calcium fluoride, montmorillonite, zirconium oxide, wet silica, dry silica, and colloidal silica. Examples of organic particles include organic particles composed of acrylic resins, styrene resins, silicone resins, polyimide resins, and core-shell organic particles.

[0084] Regarding the average particle size of the aforementioned particles, in order to prevent the formation of protrusions larger than 110 nm on the aforementioned surface, it is preferable that the average particle size is 10 nm or more and 100 nm or less.

[0085] From the viewpoint of suppressing scraping of the coating layer (R1 layer) described later during process transport, it is preferable to have an average primary particle size of 50 nm or less in the P1 layer and to use particles with high Mohs hardness. Regarding scraping during process transport, there is a situation where, when a load is suddenly applied to the surface of the coating layer and the resin constituting the coating layer deforms excessively along with the adjacent P1 layer, local scraping occurs, starting with particles of high hardness, along with the coating layer.

[0086] Therefore, by containing particles with high Mohs hardness in adjacent P1 layers and creating a dispersed state with an average primary particle size of 50 nm or less, the P1 layer itself exhibits high surface hardness, thereby suppressing deformation and thus inhibiting scratching of the coating layer. Alumina (Mohs hardness: 9) is preferably used as the particle with high Mohs hardness. A more preferred range for the average primary particle size is 30 nm or less, and even more preferably 20 nm or less.

[0087] When the P1 layer contains alumina with an average primary particle size of 50 nm or less, the particle addition amount for the P1 layer is preferably set to 0.5% by mass or less. By setting the particle addition amount to 0.5% by mass or less, it is possible to suppress the agglomeration of individual particles and the sudden formation of coarse particles larger than 110 nm, thereby suppressing surface defects and flake breakage in the green sheet. The preferred range for the particle addition amount of alumina with an average primary particle size of 50 nm or less is 0.3% by mass or less.

[0088] As a more preferred method, the thickness of layer P1 is denoted as T. P1 (μm), and the largest particle size contained in the P1 layer is denoted as D. P1 In the case of (μm), T P1 / DP1 Preferably, the value is between 20 and 100. P1 / D P1 It is a value reflecting the proportion of particles in the P1 layer, determined by adjusting T. P1 / D P1 With a value of 20 or higher, it is possible to suppress the formation of coarse protrusions on the aforementioned surfaces, by making T P1 / D P1 With a value below 100, it can increase the number of protrusions with a height of 10 nm or more and improve the slipperiness of the P1 layer.

[0089] Furthermore, the amount of particles contained in the P1 layer of the present invention is not particularly limited, but in order to prevent the formation of protrusions of 110 nm or more on the surface, it is preferably set to 0.5% by mass or less. More preferably, it is 0.2% by mass or less, and even more preferably, it is 0.1% by mass or less.

[0090] (Layer with the above-mentioned side B: P2 layer)

[0091] When the layer having the above-mentioned B side in the biaxially oriented polyester film of the present invention is used as the P2 layer, the P2 layer is preferably composed of polyester resin as the main component, just like the above-mentioned P1 layer.

[0092] The particles contained in the P2 layer of the present invention preferably have an average particle size of 100 nm or more and 900 nm or less, as determined by the method described later.

[0093] Furthermore, regarding the average particle size of the aforementioned particles (detailed in the description of the measurement method below), it is preferable to contain two or more types of particles with different average particle sizes. By containing particles with different average particle sizes, a surface with a large number of protrusions of varying heights can be formed, which can sometimes efficiently reduce the contact area between the films and suppress air mixing during winding. As a preferred combination of average particle sizes, when performing a volume-based particle size distribution measurement on the added particles, plotting the particle size on the horizontal axis and the particle presence ratio on the vertical axis, it is preferable to have two peaks in the region with a particle size of 30 nm or more and less than 1200 nm, and more preferably, one or more peaks in the region with a particle size of 30 nm or more and less than 400 nm and in the region with a particle size of 400 nm or more and less than 1200 nm.

[0094] As a more preferred method for determining the particle size contained in the P2 layer, the thickness of the P2 layer is denoted as T. P2 (μm), and the largest particle size contained in the P2 layer is denoted as D. P2 In the case of (μm), T P2 / D P2 Preferably, the value is 1 or higher and 5 or lower. T P2 / D P2It is a value reflecting the proportion of particles in the P2 layer, determined by adjusting T. P2 / D P2 A value of 1 or higher can suppress the formation of large protrusions on the aforementioned B surface, by making T P2 / D P2 When the thickness is 5 or less, the air expulsion performance becomes good when the films overlap, which can suppress the formation of wrinkles when winding them into rolls. The thickness of the P2 layer, T... P2 (μm) is not particularly limited, but by setting it to 1 or more and 10 or less, the correlation between the above particles and the stacking thickness can be easily controlled. In addition, the proportion of the P3 layer described later can be increased under the same film thickness, thereby improving recyclability.

[0095] Regarding the particles contained in the P2 layer of the biaxially oriented polyester film of the present invention, there is no limitation, similar to that of the P1 layer, and either inorganic particles or organic particles can be used. Examples of inorganic particles include, for example, calcium carbonate, magnesium carbonate, zinc carbonate, titanium dioxide, zinc oxide, cerium oxide, magnesium oxide, barium sulfate, zinc sulfide, calcium phosphate, aluminum oxide (α-alumina, β-alumina, γ-alumina, δ-alumina), mica, mica titanium, zeolite, talc, clay, kaolin, lithium fluoride, calcium fluoride, montmorillonite, zirconium oxide, wet silica, dry silica, colloidal silica, etc. Examples of organic particles include organic particles composed of acrylic resins, styrene resins, silicone resins, polyimide resins, etc., and core-shell organic particles.

[0096] The amount of particles added to the P2 layer of the biaxially oriented polyester film of the present invention is not particularly limited, but from the viewpoint of controlling the Sp5%B (nm) in the B side within a preferred range, it is preferable to set the concentration in the P2 layer to 3% by mass or less. If the concentration in the P2 layer is greater than 3% by mass, the film will partially become cloudy even when using particles with an average particle size within the preferred range, and sometimes the light transmittance and haze described later will deviate from the preferred range. More preferably, it is 2% by mass or less, and even more preferably 1% by mass or less.

[0097] Regarding the method of setting the P2 layer in the biaxially oriented polyester film of the present invention, the following methods can be used: a method of extruding the film together with the P1 layer and the P3 layer described later (co-extrusion); a method of feeding other resin layer raw materials into an extruder and melt-extruding the film to the middle of film formation, and laminating it while extruding it from the nozzle (melt lamination); a method of stacking the film formed by means of an adhesive layer, etc.

[0098] (Middle layer: P3 layer)

[0099] The biaxially oriented polyester film of the present invention preferably has a P3 layer between the P1 layer and the P2 layer. The particles / additives contained in the P3 layer can be added as long as they do not affect the smoothness of the surface (A side) of the P1 layer and the surface (B side) of the P2 layer. From the viewpoint of reducing the environmental impact of the film product, it is preferable to add the biaxially oriented polyester film of the present invention to the P3 layer to effectively use it as a recycling material. The recycling material of the biaxially oriented polyester film can be a recycling material formed entirely from the biaxially oriented polyester film, or it can be a recycling material formed by removing the P1 layer, especially the P1 layer or P2 layer with the coating layer (R1 layer described later) laminated thereon. As a method for producing recycled raw materials, commonly used methods can be employed. Examples include: temporarily crushing the film scraps generated during the slitting process in the film-making process and then pressing them to form a sheet; melting and extruding the crushed film to form small sheets; recycling waste film used in the manufacturing process of laminated ceramic capacitors, peeling off the coating layer on the polyester film using water or an alkaline solution, temporarily crushing it, and then pressing it to form a sheet; and melting and extruding the crushed film to form small sheets.

[0100] The content of the recycled raw material component in the P3 layer is preferably set to 15% by mass or more and 50% by mass or less. By making the content of the recycled raw material 15% by mass or more, the scrap film generated in the above-mentioned film-making process can be effectively used as a biaxially oriented polyester film without being discarded. By setting it to 50% by mass or less, excessive reduction in strength and durability as a biaxially stretched film can be suppressed.

[0101] (Biaxially oriented polyester film)

[0102] The polyester film in the biaxially oriented polyester film of the present invention preferably exhibits biaxial orientation. Due to biaxial orientation, the mechanical strength of the film is improved, thereby reducing wrinkles and improving windability. Furthermore, uniform tensile stress is applied during the stretching process, resulting in uniform surface smoothness throughout the entire film area. Here, biaxial orientation refers to a pattern exhibiting biaxial orientation in wide-angle X-ray diffraction. The polyester film is typically obtained by stretching an unstretched thermoplastic resin sheet along its length and width directions, followed by heat treatment to achieve crystal orientation. This will be described in detail below.

[0103] In the biaxially oriented polyester film of the present invention, the intrinsic viscosity (IV) of the polyester film is preferably 0.50 dl / g or higher, more preferably 0.60 dl / g or higher. IV is a number reflecting the length of the molecular chain. When the molecular chain is long, crystalline and amorphous portions are easily formed clearly within the same molecular chain, thus making it easier to form finer protrusions through atmospheric pressure glow discharge treatment, which is therefore preferred. In addition, by setting IV to 0.50 dl / g or higher, the polyester molecular chain is shortened, thereby enabling crystallization and suppressing the situation where frequent breakage occurs during the stretching process, making film formation difficult.

[0104] The biaxially oriented polyester film of the present invention preferably has a configuration of at least three layers (P1 layer / P3 layer / P2 layer) having the above-described P1 layer, P2 layer, and P3 layer, and having the above-described surfaces and their opposite surfaces disposed on the outermost surface.

[0105] There are no particular limitations on the method for stacking other resin layers such as P1, P2, and P3 layers. The following methods can be used: co-extrusion method described later; a method of feeding other resin layer raw materials into an extruder and melt-extruding them into a film during film formation, and laminating them while extruding them from a nozzle (melt lamination method); a method of stacking the film formed by means of an adhesive layer, etc. Among these, the co-extrusion method, which can simultaneously form protrusions and stack them through the above-described processes, is preferred.

[0106] Regarding the biaxially oriented polyester film of the present invention, from the viewpoint of film roll winding performance, the static friction coefficient (μs) between the two surfaces of the film (surface A and surface B) is preferably 0.3 or more and 0.8 or less. By making the static friction coefficient (μs) between the two surfaces of the film 0.3 or more, excessive sliding between the films during winding can be prevented, thus preventing winding misalignment. By making the static friction coefficient (μs) between the two surfaces of the film 0.8 or less, wrinkles caused by the two surfaces of the film coming together during winding can be prevented. As an upper limit for the static friction coefficient (μs) between the two surfaces of the film (surface A and surface B), 0.7 or less is more preferred, and 0.6 or less is even more preferred.

[0107] Furthermore, the biaxially oriented polyester film of the present invention may have a coating layer (R1 layer) as described later provided on its outermost surface. As a configuration in which the biaxially oriented polyester film of the present invention has a coating layer, it is preferable to have a configuration of at least four layers (R1 layer / P1 layer / P3 layer / P2 layer) including the above-described P1 layer, P2 layer, P3 layer and R1 layer as the coating layer, and arranged with R1 layer and P2 layer as the outermost surface.

[0108] When the total layer thickness of the biaxially oriented polyester film of the present invention is denoted as T (μm), T is preferably 15 or more and 100 or less. By making the total layer thickness T (μm) 15 or more, when used as a film in the manufacturing process of biaxially oriented polyester film and in the manufacturing process of laminated ceramic capacitors, film breakage due to stretching and heat treatment in the processing process can be suppressed. In addition, by making the total layer thickness T (μm) 100 or less, the film rigidity of the biaxially oriented polyester film can be prevented from increasing excessively, resulting in good processability in the heat lamination process when manufacturing electronic components. A more preferred range for the total layer thickness T (μm) is 20 or more and 50 or less.

[0109] When the thickness unevenness of the biaxially oriented polyester film of the present invention is denoted as ΔT (%), ΔT is preferably 5.0 or less. The aforementioned thickness unevenness ΔT (%) is measured by measuring the film thickness in the width direction of the film roll using the measurement method described later, and the average thickness of the film is denoted as T. AVE (μm), the maximum value of the film thickness is denoted as T. MAX (μm), the minimum value is denoted as T MIN In the case of (μm), the value is represented by the following equation (1).

[0110] ΔT(%)=100×(T MAX -T MIN ) / T AVE ...Formula (1)

[0111] By setting ΔT(%) to 5.0 or less, the surface shape of the aforementioned surface is maintained throughout the entire area of ​​the film roll, thereby preventing changes in the surface shape and the generation of surface defects in the workpiece due to local thickness unevenness. Furthermore, from the viewpoint of film winding properties, setting ΔT(%) to 5.0 or less can suppress winding misalignment caused by uneven film thickness. A more preferred range for ΔT(%) is 3.0 or less.

[0112] As a method to control ΔT(%) within a preferred range, examples include: making the slit width of the T-die during extrusion uniform in the width direction to reduce thickness unevenness of the polyester film; reducing the unevenness of the stretching temperature in the width direction during stretching using a tenter frame (described later), and keeping the relaxation treatment within an appropriate range, thereby making the temperature acting on the biaxially oriented polyester film uniform in the width direction, thus suppressing thickness unevenness caused by poor stretching, etc. Furthermore, thickness unevenness can be reduced by implementing the aforementioned plasma surface treatment using atmospheric pressure glow discharge. This is because, by employing plasma surface treatment using atmospheric pressure glow discharge, when using the roll stretching method in the length direction (described later), the film-roll adhesion is improved, thereby increasing the heating efficiency of the film before stretching. Furthermore, the film does not slide on the stretching roll during stretching and stretches uniformly, thereby suppressing thickness unevenness in the width direction.

[0113] The aforementioned plasma surface treatment using atmospheric pressure glow discharge can also be used to reduce coating thickness unevenness when a coating layer (R1 layer) is formed. By performing the surface treatment, the maximum protrusion height on the surface of the P1 layer is controlled within a preferred range, thereby suppressing the increase in thickness unevenness caused by partial coating defects. Furthermore, because the functional groups generated by the surface treatment remain on the surface of the P1 layer after the polyester film is formed, the affinity with the coating layer is improved, coating properties are enhanced, and the generation of partial coating thickness unevenness is suppressed. These effects are reflected in the coating layer thickness, i.e., T. R1 It is particularly easy to obtain when the μm is above 0.01 and below 0.30.

[0114] (Coating layer: R1 layer)

[0115] The biaxially oriented polyester film of the present invention may have a coating layer (R1) having the above-mentioned A side on its outermost surface.

[0116] The aforementioned R1 layer preferably uses a mixture containing a release agent (A) and a mixture selected from epoxy resin, melamine resin, and... The coating composition comprises at least one resin or compound (B) selected from zoline compounds, carbodiimide compounds, acrylic resins, and silicone resins. Furthermore, layer R1 preferably comprises at least one of acrylic resins and silicone resins as its main component.

[0117] By configuring it in this way, when the water contact angle of the outermost surface of the R1 layer is denoted as CaR(°), it is possible to control CaR(°) to be 100 or more and 120 or less, allowing for good formation and peeling of the target component. By making the water contact angle of the R1 layer surface, i.e., CaR(°), 100 or more, good release properties from the green sheet are achieved; and by making the water contact angle of the R1 layer surface, i.e., CaR(°), 120 or less, coating can be performed without rejecting the green sheet. A more preferred lower limit for CaR(°) is 105 or more.

[0118] The amount of organosilicon compounds contained in the P1 layer is described in detail below. It can be calculated in time-of-flight two-stage ion mass spectrometry (GCIB-TOF-SIMS) as the ratio (P / K)[-] of the peak intensity (P) of the fragment from polydimethylsiloxane to the peak intensity (K) of the fragment detected at its maximum intensity.

[0119] When using the biaxially oriented polyester film of the present invention as the film for the green sheet demolding process in the manufacturing process of multilayer ceramic capacitors, the tape peel force between the film and the surface (A surface) of the R1 layer obtained by the measurement method described later is denoted as FA (mN / 19mm). FA is preferably 5 or more and 50 or less. By setting FA (mN / 19mm) to 50 or less, the green sheet made of thin-film ceramic such as barium titanate can be peeled off without causing breakage or defects. By setting FA (mN / 19mm) to 5 or more, defects such as the green sheet accidentally lifting off the surface during process transport can be prevented. A more preferred range for the tape peel force FA (mN / 19mm) on the surface is 5 or more and 30 or less.

[0120] <Mold Release Agent (A)>

[0121] In this invention, the term "release agent (A)" refers to a compound that imparts release properties to the surface of a coating layer by being included in the coating composition. Examples of release agents (A) that can be used in this invention include resins containing long-chain alkyl groups, olefin resins, fluorinated compounds, and wax compounds. Among these, resins containing long-chain alkyl groups are preferred from the viewpoint of imparting good peelability.

[0122] The compound containing long-chain alkyl groups can be a commercially available compound. Specifically, the "Asiarejin" series (registered trademark) of long-chain alkyl compounds manufactured by Asio Industries, Ltd., the "Pierreil" series of long-chain alkyl compounds manufactured by Lion Special Kemical Co., Ltd., and the "Rezem" series of aqueous dispersions of long-chain alkyl compounds manufactured by Chukyo Oils & Fats Co., Ltd. are all acceptable. The aforementioned release agent (A) preferably has an alkyl group with 12 or more carbon atoms, and more preferably has an alkyl group with 16 or more carbon atoms. By having the alkyl group have 12 or more carbon atoms, the hydrophobicity is increased, and it can exhibit sufficient release performance as a release agent (A). If the alkyl group has fewer than 12 carbon atoms, there is a concern that the release performance may become insufficient. There is no particular upper limit to the number of carbon atoms in alkyl groups, but it is preferred if it is 25 or less, as it is easy to manufacture.

[0123] The resin having alkyl groups with 12 or more carbon atoms is more preferably a resin having alkyl side chains with 12 or more carbon atoms on the main chain of polymethylene. By making the main chain polymethylene, the number of hydrophilic groups in the resin as a whole is reduced, which makes the release effect of the release agent (A) better.

[0124] It should be noted that the presence or absence of alkyl groups with 12 carbon atoms can also be evaluated by using the intensity of the signal attributed to alkyl groups in the signal obtained from a laminated membrane, for example, by TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry). In this case, the distribution of alkyl-containing compounds can also be evaluated by continuously measuring in the depth direction using a cutting method employing ion sputtering.

[0125] <Resin or compound (B)>

[0126] Examples of resins or compounds (B) that can be used in the R1 layer of the present invention include epoxy resin, melamine resin, etc. Azoline compounds, carbodiimide compounds, acrylic resins, and silicone resins are among the preferred materials. Melamine resins and acrylic resins are preferred because the interactions involving hydroxyl groups are easily controlled, and the resin layer formed by high-temperature heating is easily modulated.

[0127] As an epoxy resin that can be used as a resin or compound (B), for example, sorbitol polyglycidyl ether crosslinking agents, polyglycerol polyglycidyl ether crosslinking agents, diglycerol polyglycidyl ether crosslinking agents, and polyethylene glycol diglycidyl ether crosslinking agents can be used. Commercially available epoxy resins can be used, such as epoxy compounds "Denacol" (registered trademark) EX-611, EX-614, EX-614B, EX-512, EX-521, EX-421, EX-313, EX-810, EX-830, EX-850, etc. manufactured by Nagasekec Co., Ltd., diepoxy / polyepoxy compounds (SR-EG, SR-8EG, SR-GLG, etc.) manufactured by Sakamoto Pharmaceutical Co., Ltd., and epoxy crosslinking agents "EPICLON" (registered trademark) EM-85-75W or CR-5L manufactured by Dai Nippon Inki Kogyo Co., Ltd., etc. Among these, water-soluble epoxy resins are preferred.

[0128] As a melamine resin that can be used as a resin or compound (B), for example, melamine, hydroxymethylated melamine derivatives obtained by condensing melamine with formaldehyde, compounds obtained by reacting hydroxymethylated melamine with a lower alcohol to partially or completely etherify them, and mixtures thereof can be used. Furthermore, as a melamine resin, any resin can be a condensate formed from monomers or polymers of two or more monomers, or a mixture thereof. As the lower alcohol used in etherification, methanol, ethanol, isopropanol, n-butanol, and isobutanol can be used. It includes imino-type methylated melamine resins, hydroxymethyl-type melamine resins, hydroxymethyl-type methylated melamine resins, and fully alkyl-type methylated melamine resins, etc., having imino, hydroxymethyl, or alkoxymethyl groups such as methoxymethyl or butoxymethyl as functional groups in one molecule. Among these, hydroxymethylated melamine resins are most preferably used.

[0129] Additionally, it can be used as a resin or compound (B). Azoline compounds are compounds that have the following properties in this compound: Compounds containing an oxazolinyl group as a functional group are preferably composed of at least one of the following functional groups: A monomer containing an oxazolinyl group and copolymerized with at least one other monomer to obtain a product containing an oxazolinyl group. Compounds composed of copolymers of zoline groups.

[0130] As containing Monomers with an oxazolinyl group can use 2-vinyl-2- Azoline, 2-vinyl-4-methyl-2- Azoline, 2-vinyl-5-methyl-2- Azoline, 2-isopropenyl-2- Azazoline, 2-isopropenyl-4-methyl-2- Azoline and 2-isopropenyl-5-ethyl-2- Azoline, etc., or a mixture of one or more of them can be used. Among them, 2-isopropenyl-2- Azoline is readily available industrially and is therefore suitable.

[0131] exist Among zoline compounds, those containing The monomer containing the zolyl group and at least one other monomer used is capable of reacting with the monomer containing the zolyl group. Monomers for copolymerization of azolinyl monomers may include, for example, acrylates or methacrylates such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, and 2-ethylhexyl methacrylate; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, and maleic acid; unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated amides such as acrylamide, methacrylamide, N-hydroxymethylacrylamide, and N-hydroxymethylmethylacrylamide; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; olefins such as ethylene and propylene; halogen-containing α,β-unsaturated monomers such as vinyl chloride, vinylidene chloride, and vinyl fluoride; and α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene. One or a mixture of two or more of these monomers may also be used.

[0132] Additionally, carbodiimide compounds that can be used as resins or compounds (B) are compounds in which one or more carbodiimide groups or cyanamide groups that are tautomerically related to carbodiimide are functional groups within the molecule. Specific examples of such carbodiimide compounds include dicyclohexylmethane carbodiimide, dicyclohexylcarbodiimide, tetramethylphenyldimethylene carbodiimide, and urea-modified carbodiimide, and mixtures of one or more of these compounds may also be used.

[0133] The coating layer of the biaxially oriented polyester film of the present invention may also contain an isocyanate compound as a resin or compound (B). Examples of isocyanate compounds include, for example, toluene diisocyanate, diphenylmethane-4,4'-diisocyanate, isophthalene diisocyanate, hexamethylene-1,6-diisocyanate, 1,6-diisocyanatohexane, an adduct of toluene diisocyanate and glycerol, an adduct of toluene diisocyanate and trimethylolpropane, polyol-modified diphenylmethane-4,4'-diisocyanate, carbodiimide-modified diphenylmethane-4,4'-diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, 3,3'-dibenzyl-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, isophthalene diisocyanate, etc.

[0134] Furthermore, isocyanate groups readily react with water; therefore, considering the pot life of the coating agent, it is suitable to use end-capped isocyanate compounds obtained by masking the isocyanate groups with a blocking agent or the like. In this case, by applying heat during the drying process after coating the coating composition onto the polyester film, the blocking agent dissociates, exposing the isocyanate groups, and as a result, the crosslinking reaction proceeds.

[0135] There are no particular limitations on the acrylic resins that can be used as resins or compounds (B), but acrylic resins composed of alkyl methacrylates and / or alkyl acrylates are preferred.

[0136] As alkyl methacrylates and / or alkyl acrylates, preferably used are methacrylic acid, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, acrylic acid, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, maleic acid, itaconic acid, acrylamide, N-hydroxymethylacrylamide, diacetone acrylamide, etc. One or more of these can be used.

[0137] In addition, the urethane resin that can be used as a resin or compound (B) is preferably a resin obtained by reacting a polyhydroxy compound with a polyisocyanate compound using a polymerization method known for urethane resins, such as emulsion polymerization or suspension polymerization.

[0138] Examples of polyhydroxy compounds include polyethylene glycol, polypropylene glycol, polyethylene / propylene glycol, polybutylene glycol, hexamethylene glycol, tetramethylene glycol, 1,5-pentanediol, diethylene glycol, triethylene glycol, polycaprolactone, polyhexanediol adipate, polyhexanediol sebacate, polybutylene adipate, trimethylolpropane, trimethylolethane, pentaerythritol, polycarbonate glycol, and glycerol.

[0139] As polyisocyanate compounds, examples such as hexamethylene diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, adducts of toluene diisocyanate and trimethylene propane, and adducts of hexamethylene diisocyanate and trimethylolethane can be used.

[0140] The silicone resin that can be used as a resin or compound (B) can be a type with a curable silicone resin as the main component or a type with a modified silicone resin as the main component. As a type of curable silicone resin, any curing reaction type can be used, such as addition-type / condensation-type / UV-curable / electron-beam-curable / solvent-free type, or a combination of heat and UV curing. As a type of modified silicone resin, it can be a modified silicone resin obtained by graft polymerization with organic resins such as epoxy resin, urethane resin, and alkyl resin.

[0141] In the coating composition forming the coating layer of the biaxially oriented polyester film of the present invention, the mass ratio of release agent (A) to resin or compound (B) is preferably in the range of 10 / 90 to 45 / 55. More preferably, it is in the range of 15 / 85 to 45 / 55. By setting it to such a range, the release agent (A) in the resin layer is sufficient, which enables good initial tape peel strength. At the same time, the resin or compound (B), which is easily affected by heating, is also sufficient, thus enabling good peel characteristics before and after heating.

[0142] In the coating layer (R1) of the present invention, particles can be contained within a range that has no effect on the Sp5%A (nm) of the A-side.

[0143] The thickness of the R1 layer in this invention is denoted as T. R1 In the case of (μm), T R1 Preferably, it is 0.01 or higher and 1.00 or lower. By making the above T... R1 With a μm value of 0.01 or higher, it can exhibit a peeling function relative to the object component, by making the above T R1 A thickness (μm) of 1.00 or less can reduce uneven drying of the coating composition and suppress localized uneven coating layer formation. The thickness T of the aforementioned R1 layer... R1 A more preferred range is 0.01 or higher and 0.30 or lower.

[0144] The method of constituting the R1 layer in this invention is not particularly limited. When using the coating composition described above, any method can be used, such as an offline coating method that coats the coating after the polyester film is manufactured, or an online coating method that coats and dries the coating during the polyester film manufacturing process.

[0145] (Object components set on the above surface)

[0146] <Ceramic Slurry>

[0147] When using the biaxially oriented polyester film of the present invention as a support film for forming green sheets in the process of manufacturing multilayer ceramic capacitors, it is preferable to coat the above-mentioned surface of the release resin coating layer (R1) with a ceramic slurry for green sheets.

[0148] There are no particular limitations on the raw materials of ceramics used to form ceramic slurries; various dielectric materials can be used. Examples include oxides formed from metals such as titanium, aluminum, barium, lead, zirconium, silicon, and yttrium, barium titanate, and Pb(Mg) oxide. 1 / 3 ,Nb 2 / 3 O3, Pb(Sm) 1 / 2 ,Nb 1 / 2 O3, Pb(Zn) 1 / 3 ,Nb 2 / 3 PbO3, PbThO3, PbZrO3, etc. They can be used as monomers or in combination of two or more.

[0149] As binder resins constituting ceramic slurries, various polymers can be used, such as polyurethane resin, urea resin, melamine resin, epoxy resin, vinyl acetate resin, acrylic resin, polyvinyl alcohol, and polyvinyl butyral. They can be used as monomers or in combination of two or more.

[0150] The solvent for ceramic slurry can be water or an organic solvent. In the case of organic solvents, toluene, ethanol, methyl ethyl ketone, isopropanol, γ-butyrolactone, etc., can be used. They can be used as monomers or in combination of two or more. Additionally, plasticizers, dispersants, antistatic agents, surfactants, etc., can be added to the ceramic slurry as needed.

[0151] (Manufacturing method of biaxially oriented polyester film)

[0152] Next, an example of a method for manufacturing the biaxially oriented polyester film of the present invention will be given, but it is not to be construed that the present invention is limited to the products obtained from such examples.

[0153] As a method for obtaining the polyester film used in this invention, a conventional polymerization method can be employed. For example, it can be obtained by subjecting a dicarboxylic acid component such as terephthalic acid or its ester-forming derivative, and a diol component such as ethylene glycol or its ester-forming derivative, to an transesterification reaction or an esterification reaction using a known method, followed by a melt polymerization reaction. Alternatively, if necessary, the polyester obtained in the melt polymerization reaction can be subjected to a solid-state polymerization reaction below the melting point temperature of the polyester.

[0154] The polyester film of the present invention can be obtained using conventionally known manufacturing methods. Specifically, the polyester film of the present invention can be produced by the following method (melt casting): a raw material that has been dried as needed is heated and melted in an extruder, and extruded from a nozzle onto a cooled casting drum to form a sheet. Alternatively, the following method (solution casting) can be used: the raw material is dissolved in a solvent, the solution is extruded from a nozzle onto a support such as a casting drum or annular belt to form a film, and then the solvent is dried and removed from such a film to form a sheet.

[0155] When manufacturing two or more layers of biaxially oriented polyester film using melt casting, the following method (co-extrusion) is suitable: The raw materials for each layer constituting the biaxially oriented polyester film are melted using an extruder. These layers are then stacked in a molten state using a confluence device located between the extruder and the nozzle, and introduced into the nozzle. The film is then extruded from the nozzle onto a casting drum to form a sheet. This stacked sheet is then electrostatically bonded to a casting drum with a surface temperature cooled to 20°C or higher and 60°C or lower, and cooled and solidified to produce an unstretched film. By setting the surface temperature of the casting drum to 20°C or higher, the crystalline polyester portion on the surface of the unstretched film can be further increased, achieving the effect of forming fine protrusions after stretching through plasma surface treatment using atmospheric pressure glow discharge. Furthermore, by setting the surface temperature of the casting drum to 60°C or lower, adhesion of the unstretched film to the casting drum can be suppressed, resulting in an unstretched film with less thickness unevenness in the film travel direction. A more preferred range for the surface temperature of the casting drum is 25°C or higher and 55°C or lower.

[0156] Next, the unstretched film obtained therein undergoes surface treatments such as plasma surface treatment using atmospheric pressure glow discharge. These surface treatments can be performed immediately after obtaining the unstretched film or after stretching along the film's travel direction (hereinafter, sometimes referred to as the length direction). In this invention, from the viewpoint of further promoting the formation of the aforementioned protrusions, it is preferable to perform surface treatment on the unstretched film. Furthermore, the surface to which the surface treatment is performed can be any surface that has been in contact with the casting drum (drum surface) or a surface that has not been in contact with the casting drum (non-drum surface).

[0157] (Sequential biaxial stretching)

[0158] There are no particular limitations on the stretching conditions when biaxially stretching the unstretched film. In the case where the polyester film of the present invention uses polyester as the main component, for stretching in the longitudinal direction, it is preferable to feed the unstretched film into a roller assembly heated to 70°C or higher, stretch it along the longitudinal direction (longitudinal direction, i.e., the direction of film travel), and cool it using a roller assembly set to a temperature of 20°C or higher and 50°C or lower. Regarding the lower limit of the heating roller temperature during longitudinal stretching, there are no particular limitations as long as it does not impair the stretchability of the sheet, but it is preferable to be higher than the glass transition temperature of the polyester resin used. Furthermore, the preferred range for the longitudinal stretching ratio is 3 times or more and 5 times or less. A more preferred range is 3 times or more and 4 times or less. If the longitudinal stretching ratio is 3 times or more, orientation crystallization can occur, which can improve the film strength. On the other hand, by keeping the stretching ratio at 5 times or less, it is possible to suppress excessive orientation crystallization of the polyester resin accompanying stretching, which could lead to brittleness and breakage during film formation.

[0159] Regarding stretching in the direction perpendicular to the length direction (width direction), it is preferable to hold both ends of the film with clamps while feeding it into the tenter frame. The film is stretched 3 to 5 times its original length in an atmosphere heated to 70°C to 160°C. The stretched film is then heat-treated to stabilize its internal orientation structure. The thermal history temperature experienced by the film during heat treatment can be determined using the small endothermic peak (sometimes called Tmeta) temperature appearing directly below the melting point temperature as measured by differential scanning calorimetry (DSC), as described later. However, when polyester (melting point 255°C) is the main component, it is preferable to set the tenter frame temperature to be 200°C to 250°C or higher. When other thermoplastic resins are used as the main component, it is preferable to set the temperature to be below -55°C and below -5°C of the resin melting point. By setting the heat treatment temperature to 200°C or higher, the dimensional stability of the biaxially oriented polyester film can be improved. By setting the heat treatment temperature to 250°C or lower, film breakage due to melting of the polyester film can be suppressed, resulting in efficient manufacturing. A more preferred range is 220°C or higher and 245°C or lower.

[0160] As for the range of Tmeta, which represents the thermal history temperature that the film withstands during heat treatment, when polyester resin is the main component, it is preferably 190°C or higher and 245°C or lower for the reasons mentioned above. An even more preferred range is 210°C or higher and 240°C or lower.

[0161] Furthermore, with the aim of imparting dimensional stability after heat treatment, relaxation treatment can be performed within a range of 1% to 6%. By making the relaxation treatment 1% or more, the dimensional stability of the biaxially oriented polyester film when used in high-temperature environments can be improved. By making the relaxation treatment 6% or less, a moderate tension can be continuously applied to the biaxially oriented polyester film to prevent the deterioration of thickness unevenness.

[0162] The stretch ratio is set to 3 times or more and 5 times or less in both the length and width directions, and the area ratio (stretch ratio in the length direction × stretch ratio in the width direction) is preferably 9 times or more and 22 times or less, more preferably 9 times or more and 20 times or less. By setting the area ratio to 9 times or more, the molecular orientation of the obtained biaxially oriented polyester film can be promoted, thereby improving durability, and by setting the area ratio to 22 times or less, breakage during stretching can be suppressed.

[0163] (Manufacturing method of biaxially oriented polyester film)

[0164] An example of a manufacturing method for setting a release layer on a biaxially oriented polyester film obtained by the above manufacturing process through offline coating is given, but it is not to be construed as the present invention being limited to the products obtained by such an example.

[0165] After coating the coating composition onto the biaxially oriented polyester film of the present invention, it is dried at a temperature of 60°C or higher and 110°C or lower, thereby forming a coating layer. There is no particular limitation on the drying time, but by setting it to 30 seconds or less, the productivity of the coating process can be improved.

[0166] As a coating method for the above-mentioned coating composition, known coating methods can be used, such as gravure coating, reverse gravure coating and other roller coating methods, bar coating using a wire bar, mold coating, lip coating, spraying, air knife coating and so on.

[0167] [Methods for evaluating characteristics]

[0168] A. Evaluation using a scanning white interference microscope (VertScan)

[0169] A 6cm × 6cm sample was taken from a biaxially oriented polyester film. For each sample, a scanning white interference microscope (device: Hitachi VertScan VS1540, registered trademark) with a 10x objective lens was used to measure the aforementioned surface of the biaxially oriented polyester film with a measurement area of ​​561μm × 561μm. Regarding sample setup, the sample was placed on the stage with the Y-axis as the length direction of the sample film (the direction in which the film is rolled). It should be noted that in the case of samples where the length direction is unclear, measurements were taken with the Y-axis as any one direction of the sample film, then with the Y-axis rotated 120 degrees, and then again with the Y-axis rotated 120 degrees. The average of these measurements was taken as the number of protrusions in the sample. In addition, the sample membrane to be measured is clamped into two metal frames with rubber pads, thereby tautening the membrane inside the frames (eliminating the loose or curled state of the sample) for surface measurement.

[0170] For the obtained microscope images, the surface analysis software VS-ViewerVersion 10.0.3.0, which is built into the microscope, was used to perform image processing under the following conditions, thereby determining the arithmetic mean surface roughness and the number of protrusions at each height.

[0171] (Image processing conditions)

[0172] Perform image processing in the following order.

[0173] • Interpolation processing: Full interpolation

[0174] • Filtering: Median (3×3 pixels)

[0175] • Surface correction: 4 times.

[0176] (i) The top 5% of the maximum protrusion height (Sp5%A and Sp5%B)

[0177] Regarding the aforementioned surface (surface A) of the biaxially oriented polyester film, measurements were taken in 100 fields of view using a scanning white interference microscope. For each measurement image that underwent the aforementioned image processing, the maximum protrusion height Sp (nm) for each of the 100 fields of view was calculated by converting the "Peak [μm]" displayed in the "ISO Parameters" tab of the "Parameter Table" window in the surface analysis software into nm units. The top 5% of the values ​​(the fifth largest value in the case of 100 fields of view) were taken as the top 5% of the maximum protrusion height of the aforementioned surface (surface A), Sp5%A (nm).

[0178] Similarly, scanning white interference microscope measurements were performed on the B-side. For each measurement image that underwent the above image processing, the maximum protrusion height Sp (nm) for each of the 100 fields of view was calculated by converting the "Peak [μm]" displayed in the "ISO Parameters" tab of the "Parameter Table" window in the surface analysis software into nm units. The top 5% of the values ​​(the fifth largest value in the case of 100 fields of view) were taken as the top 5% of the maximum protrusion height of the B-side Sp5%B (nm).

[0179] (ISO parameter analysis conditions)

[0180] ISO parameter analysis was performed under the following conditions.

[0181] • S-Filter: Automatic

[0182] Normal probability paper

[0183] Number of divisions: 300

[0184] Upper limit of the calculation range: 3.000

[0185] Lower limit of the calculation range: -3.000

[0186] • Parameters: Select only "Height Parameters"

[0187] • Output: Select "Parameter List"

[0188] (Parameter table output)

[0189] Select "HeightParameters" in the "ISO Parameters" window displayed by the above ISO parameter analysis, and then "Append to Parameter Table". This will convert the "Peak [μm]" value displayed in the "ISO Parameters" tab of the "Parameter Table" window into nm units for use.

[0190] (ii) Number of protrusions with a height of 80 nm or more (N) 80nm A)

[0191] Following the same procedure as described in (i), after microscopic image observation and image processing of the surface (surface A), particle analysis 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 80 nm (R... 80nm The number of particles displayed in the "Particle Analysis" screen (with a height threshold setting of 0.08 μm) is divided by the measurement area (561 μm × 561 μm) to calculate the number of protrusions with a height of 80 nm or more (particles / mm). 2 ).

[0192] (Conditions for particle analysis)

[0193] Protrusion analysis was performed under the following conditions.

[0194] • Type of analysis: Protrusion analysis

[0195] • Image correction: None

[0196] ·deal with

[0197] Height threshold: 0.08 μm, (N mentioned later) 10nm Analysis A: 0.01μm

[0198] Particle shaping: None

[0199] Reference height: Zero plane (average plane)

[0200] • Target

[0201] Height / Depth: -10000μm≤h≤10000μm

[0202] Longest diameter: -10000μm≤d≤10000μm

[0203] Volume: V≥0.0000μm 3

[0204] Aspect ratio: r≥0.0000

[0205] • Histogram: number of segments 50

[0206] The same operation was performed on all 100 fields of view measured, and their average value was taken as the number N of protrusions with a height of 80 nm or more on the A-side of the sample. 80nm A (pieces / mm) 2 ).

[0207] (Reference height: Zero plane (average plane))

[0208] As the zero plane (average plane) in the above-mentioned reference height setting, the microscope image is observed using the above method. In the measurement image (561μm×561μm) obtained by performing the above image processing, the plane of the average height (Ave) automatically calculated by the following formula is used.

[0209]

[0210] • lx: The length of the X-direction range in each measurement image after the above image processing.

[0211] ·ly: The length of the Y-direction range in each measured image after the above image processing.

[0212] • h(x, y): The height of each image point (x, y) within the measured image after the above image processing.

[0213] (iii) Number of protrusions with a height of 10 nm or more (N) 10nm A)

[0214] Following the same procedure as described in (i), after microscopic observation and image processing of the surface (surface A), particle analysis 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 10 nm (R... 10nm The number of particles displayed in the "Particle Analysis" screen (with a height threshold setting of 0.01 μm) is divided by the measurement area (561 μm × 561 μm) to calculate the number of protrusions with a height of 10 nm or more (particles / mm). 2 ).

[0215] The same operation was performed on all 100 fields of view measured, and their average value was taken as the number N of protrusions with a height of 10 nm or more on the A-side of the sample. 10nm A (pieces / mm) 2 ).

[0216] B. Water contact angle (CaR)

[0217] After the biaxially oriented polyester film of the present invention was placed in an atmosphere with a room temperature of 23°C and a humidity of 65% for 24 hours, the contact angle between the above-mentioned surface (surface A) and water was measured under this atmosphere using a contact angle meter CA-D type (manufactured by Kyowa Interface Science Co., Ltd.) based on JIS K6768. Five measurements were taken, and the average of the three measurements excluding the maximum and minimum values ​​was taken as the water contact angle CaR (°) of the above-mentioned surface A.

[0218] C. Film thickness

[0219] (i) Total layer thickness

[0220] Regarding the total layer thickness of the biaxially oriented polyester film, a dial gauge was used to measure the thickness at five arbitrary locations with ten films overlapped, according to JIS K7130 (1992) A-2 method. The average value was divided by 10 to obtain the total layer thickness T (μm).

[0221] (ii) Stack thickness (T) P1 T P2 )

[0222] Using a thin-film slicer, a cross-section of the biaxially oriented polyester film is cut along a direction parallel to the film width. This cross-section is observed using a scanning electron microscope at a magnification between 5000 and 20000, and the thickness ratio of each layer is determined. The thickness of each layer is calculated from the determined layer ratio and the total film thickness obtained in step (i) above.

[0223] (iii) Thickness of coating layer (R1) (T) R1 )

[0224] The biaxially oriented polyester film was stained with ruthenium tetroxide (RuO4) and / or osmium tetroxide (OsO4). The biaxially oriented polyester film was frozen and cut along its thickness direction to obtain 10 ultrathin sections for resin layer cross-section observation. Each section was observed using a TEM (transmission electron microscope: Hitachi, Ltd. H7100FA type) at magnifications between 10,000 and 1,000,000, and cross-sectional photographs were obtained. The average thickness of the release resin coating layer (R1 layer) with the aforementioned surface at these 10 points (10 sections) was taken as the thickness T of the release resin coating layer. R1 (μm).

[0225] (iv) Uneven thickness ΔT in the width direction of the membrane roll

[0226] The full width measurement of a biaxially oriented polyester film roll was performed using a contact continuous thickness gauge (KG601B manufactured by Anritsu Corporation).

[0227] In the obtained film thickness, according to the following formula (1), from the maximum value (T) MAX Subtract the minimum value (T) MIN This results in uneven thickness, which is then divided by the average value (T). AVE The percentage unit was converted to obtain ΔT (%). Three measurements were taken at every 15m along the unwinding direction of the film, and ΔT was calculated for each location. The maximum value of these measurements was taken as the thickness unevenness ΔT (%) of the biaxially oriented polyester film.

[0228] ΔT(%)=100×(T MAX -T MIN ) / T AVE ...Formula (1)

[0229] The width direction of the aforementioned film roll refers to the direction perpendicular to the unwinding direction within the film plane of the biaxially oriented polyester film of the present invention. In cases where the unwinding direction is unclear in a biaxially oriented polyester film cut to a specific size, thickness unevenness is measured in two directions: a specific direction and a direction inclined at 90° within the film plane from the aforementioned measurement direction. The maximum value of these two directions is taken as the thickness unevenness ΔT (%) of the biaxially oriented polyester film.

[0230] Similarly, in the case of biaxially oriented polyester film cut to a specific size and where it is difficult to perform three measurements every 15m in the unwinding direction, the thickness unevenness in the width direction is measured at three equal division points of the total width in the unwinding direction, and the maximum value of these measurements is taken as the thickness unevenness ΔT (%) of the biaxially oriented polyester film.

[0231] D. Tape peel strength (FA)

[0232] The tape peel strength was measured as described below.

[0233] First, an acrylic polyester adhesive tape (manufactured by Nitto Denko Co., Ltd., Nitto 31B tape, 19mm wide) was bonded to the coating layer of the biaxially oriented polyester film of the present invention, and a 2kgf roller was passed back and forth once from above to create a tape-bonded laminated film. Then, the tape-bonded laminated film was left to stand at 25°C and 65% RH for 24 hours, and the peel force (N / 19mm) was measured using a Shimadzu universal testing machine "Autograf AG-1S" at a peel angle of 180° and a tensile speed of 300mm / min. The average peel force over 5 to 10 seconds was calculated from the peel force (N / 19mm) versus test time (sec) curve obtained by the measurement. Five identical measurements were performed, and the average of the three measurements after removing the maximum and minimum values ​​was taken as the peel force FA (mN / 19mm) of the laminated film.

[0234] E. Static friction coefficient (μs)

[0235] After conditioning the biaxially oriented polyester film of the present invention at 23°C and 65% RH, two strips with a width of 75 mm and a length of 100 mm were cut out as samples, with the direction of the film production line as the length direction. The samples were then measured using a slip coefficient measuring device (model ST-200, manufactured by Technonis Co., Ltd.) at 23°C and 65% RH. On the measuring data stage of the device, the strip sample was positioned and fixed with the stretching direction of the device aligned with the length direction of the strip sample, and the aforementioned surface side facing upwards. Another strip sample was placed on top of it with the aforementioned surface facing upwards and the stretching direction aligned with the length direction, so that the aforementioned surface was in contact with the opposite surface of the strip sample. The end of the sample was then fixed to a U-shaped pressure gauge for load detection of the device. The membrane was then allowed to stand, and a 200g weight was placed on top of it, with a 6.5cm x 6.5cm telegraph sheet as the sample contact surface. After ensuring close contact between the samples, the upper membrane was stretched under the following conditions, and the static friction coefficient was measured. Ten measurements were performed, and the average of the six measurements excluding the first two and last two points was used as the static friction coefficient (μs).

[0236] Measurement distance: 12mm

[0237] Measurement speed: 210 mm / min.

[0238] F. Polymer Properties

[0239] (i) Intrinsic viscosity (IV)

[0240] The test sample (polyester resin (raw material), particle masterbatch, or sample obtained by separating only the P1 layer) was dissolved in 100 ml of o-chlorophenol (solution concentration C (test sample weight / solution volume) = 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 (2), and the obtained value was taken as the intrinsic viscosity (IV).

[0241] ηsp / C=[η]+K[η] 2 ·C···(2)

[0242] (Here, ηsp = (solution viscosity / solvent viscosity) - 1, and K is the Hutchins constant (0.343).)

[0243] It should be noted that the following method was used to determine the presence of insoluble substances such as inorganic particles in the solution obtained by dissolving the test sample.

[0244] (1-1) Dissolve the test sample in 100 mL of o-chlorophenol to prepare a solution with a concentration greater than 1.2 g / 100 mL. Here, the weight of the test sample supplied to o-chlorophenol is taken as the weight of the test sample.

[0245] (1-2) Next, the solution containing insoluble matter is filtered, and the weight of the insoluble matter and the volume of the filtrate are measured.

[0246] (1-3) Add o-chlorophenol to the filtered filtrate and adjust it so that (the weight of the sample (g) - the weight of the insoluble matter (g)) / (the volume of the filtered filtrate (mL) + the volume of the added o-chlorophenol (mL)) becomes 1.2 g / 100 mL.

[0247] (For example, when preparing a concentrated solution with a sample weight of 2.0 g / 100 mL, if the weight of the insoluble matter after filtration is 0.2 g and the volume of the filtrate is 99 mL, an additional 51 mL of o-chlorophenol is added for adjustment. ((2.0 g - 0.2 g) / (99 mL + 51 mL) = 1.2 g / 100 mL))

[0248] (1-4) Using the solution obtained in (1-3), the viscosity at 25°C is measured using an Ostwald viscometer. Using the obtained solution viscosity and solvent viscosity, [η] is calculated from the above formula (3), and the obtained value is used as the intrinsic viscosity (IV).

[0249] (ii) Amount of terminal carboxyl groups (unit: eq / t, recorded as COOH amount in the table).

[0250] The determination was performed using Maulice's method. (Reference: MJ Maulice, F. Huizinga, Anal. Chem. Acta, 22, 363 (1960)).

[0251] That is, weigh 0.5 g of the test sample (polyester (raw material) or polyester film obtained by separating only the P1 layer) with an accuracy of 0.001 g. Add 50 ml of a solvent obtained by mixing o-cresol and chloroform at a mass ratio of 7 / 3 to the sample, heat to an internal temperature of 90°C, and stir for 20 minutes to dissolve. Also, use only the mixed solvent as a blank solution and heat it separately. Cool the solution to room temperature and titrate using a potential difference titration apparatus with a 1 / 50 N potassium hydroxide methanol solution. Also, titrate the blank solution containing only the mixed solvent in the same way.

[0252] The value calculated by the following formula shall be used as the amount of terminal carboxyl group in the sample to be measured.

[0253] Terminal carboxyl group amount (equivalent / t) = {(V1-V0)×N×f}×1000 / S

[0254] Here, V1 is the titration volume of the sample solution (mL), V0 is the titration volume of the blank solution (mL), N is the equivalent concentration of the titration solution (N), f is the factor of the titration solution, and S is the mass of the polyester composition (g).

[0255] G. Includes particle evaluation

[0256] (i) Average particle size

[0257] Regarding the biaxially oriented polyester film of the present invention, small sheets were prepared by cutting along a direction perpendicular to the surface using a thin-film slicer. The cross-sections of these sheets were observed and photographed using a field emission scanning electron microscope (JSM-6700F, manufactured by Nippon Electron Co., Ltd.) at magnifications between 10,000 and 30,000. The particle size distribution of particles present in the P1, P2, or P3 layers was determined from the cross-sectional photographs using Image-Pro Plus (Ropper Co., Ltd., Japan) image analysis software. Cross-sectional photographs were selected from different arbitrary measurement fields, and the equivalent circle diameters of at least 400 particles randomly selected from the cross-sectional photographs were measured to obtain the volume-based average particle size. In cases where the particles contain two or more types of particles based on the elemental analysis of the constituent particles, the equivalent circle diameters of at least 200 particles for each particle were measured, and the average particle size was determined from the average of the volume-based equivalent circle diameters.

[0258] (ii) Particle size distribution analysis

[0259] A volumetric particle size distribution analysis was performed on the particle size obtained using the method described in (i) above. Here, the particle size, which serves as the horizontal axis in the volumetric particle size distribution, is represented by 10 nm increments starting from 0 nm. The particle size at the apex of the obtained particle size distribution map was read.

[0260] (iii) Maximum particle size (D) P1 D P2 )

[0261] Regarding the particle size obtained using the method described in (i) above, the maximum value is taken as the maximum particle size contained in the layer.

[0262] (iv) Particle content

[0263] The P1 or P2 layer portion of the biaxially oriented polyester film of the present invention is partially immersed in 200 ml of 1N-KOH methanol solution and heated under reflux to dissolve the polymer. 200 ml of water is added to the dissolved solution, and the liquid is then centrifuged to allow the particles to settle, removing the supernatant. Water is further added to the particles for washing, centrifugation, and this process is repeated twice. The particles obtained as described above are dried, their mass is measured, and the particle content (mass %) in each layer is calculated. In cases where the added particles contain organic particles, a solvent in which the polymer dissolves but the organic particles do not dissolve is selected. The polymer is dissolved under reflux without overheating, the particles are centrifuged, and the particle content (mass %) is calculated.

[0264] [Evaluation methods for application characteristics]

[0265] H. Surface defects during process transport

[0266] For the biaxially oriented polyester film of the present invention, film forming was performed at a film forming speed of 100 m / min or higher, and 10 consecutive 5000 m film rolls were collected. The 10 film rolls were unwound, and surface damage defects on the surface of the release resin coating layer (the aforementioned surface) were evaluated as follows.

[0267] AA: Of the 10 rolls, 0 rolls had surface damage defects.

[0268] A: Of the 10 rolls, more than one but less than two rolls had surface damage defects.

[0269] B: Of the 10 rolls, 3 to 4 rolls had surface damage defects.

[0270] C: Of the 10 rolls, 5 to 6 rolls had surface damage defects.

[0271] D: Of the 10 rolls, more than 7 rolls had surface damage defects.

[0272] As surface defects during process transport, A to C are considered good, with AA being the best.

[0273] I. Surface scraping properties during process transport

[0274] Regarding the surface scrapability during process transport, the following tests were conducted using a belt travel tester and a single blade, and the evaluation was based on the amount of scraping powder adhering to the single blade.

[0275] First, a biaxially oriented polyester film with a coated layer was cut into strips with a width of 12.65 mm and a length of 25 cm. After being conditioned for one day at 23°C and 65% RH, it was used as a sample. A strip travel tester SFT-700 (manufactured by Yokohama System Research Institute Co., Ltd.) was equipped with the following device. Under the condition of 23°C and 65% RH, a load of 300 g was applied to the end of the strip sample, and it was traveled 10 cm at a speed of 3.33 cm / s while under tension along the length direction.

[0276] At this time, the sample is moved forward with the carbon steel razor pressed against the surface of the release resin coating layer of the biaxially oriented polyester film with the coating layer (the aforementioned surface) by 1 mm.

[0277] Then, using an optical microscope at 200x magnification, the surface through which the single-edged membrane passed was observed, and the accumulation height of the scraping powder deposited on the blade tip was determined. This scraping accumulation height was observed at any 5 points within a 12.65mm range through which the single-edged membrane passed, and their average value was used to evaluate the surface scraping properties of the sample during process transport.

[0278] A: The accumulation height of the scraping powder is less than 20μm.

[0279] B: The accumulation height of the scraping powder is greater than 20μm and less than 30μm.

[0280] C: The stacking height of the scraping powder is greater than 30μm and less than 40μm.

[0281] D: The buildup height of the scraping powder is greater than 40μm.

[0282] As for surface scraping properties during process transport, A to C are good, with A being the best.

[0283] (Device Composition)

[0284] Guide diameter: 6mmΦ

[0285] Guide material: SUS27 (surface roughness 0.2S)

[0286] Winding angle: 90°

[0287] Single-edged: Carbon steel razor (Fezar Safety Razor Co., Ltd., FAS-10)

[0288] Single-blade setting direction: The single-blade is set so that its width direction is parallel to the width direction of the strip, and the angle between the single-blade and the surface of the release resin coating layer is 90°.

[0289] Single-blade pressing length: 1mm along the sample thickness direction

[0290] (Measurement conditions)

[0291] Travel distance: 10cm

[0292] Travel speed: 3.33 cm / second.

[0293] J. Wrapping misalignment

[0294] For the biaxially oriented polyester film of the present invention, film formation was performed at a film formation speed of 100 m / min or higher, and 10 consecutive 5000 m rolls were collected. The occurrence of winding misalignment in the 10 film rolls obtained was evaluated as follows.

[0295] A: Of the 10 rolls, fewer than 2 rolls were found to have miswound.

[0296] B: Of the 10 rolls, 3 to 4 rolls were miswound.

[0297] C: Of the 10 rolls, 5 to 6 rolls were miswound.

[0298] D: Of the 10 rolls, more than 7 rolls were found to have miswound.

[0299] As for winding misalignment, A to C are considered good, with A being the best.

[0300] As for process transportability, A to C are good, with A being the best.

[0301] K. Curled pleats

[0302] For the biaxially oriented polyester film of the present invention, film formation was performed at a film formation speed of 100 m / min or higher, and 10 consecutive 5000 m rolls were collected. The generation of winding wrinkles in the 10 film rolls obtained were evaluated as follows.

[0303] A: Of the 10 rolls, fewer than 2 rolls produced folds and wrinkles.

[0304] B: Of the 10 rolls, 3 to 4 rolls produced folds and wrinkles.

[0305] C: Of the 10 rolls, 5 to 6 rolls produced folds and wrinkles.

[0306] D: Of the 10 rolls, more than 7 rolls produced folds and wrinkles.

[0307] As for the rolled pleats, A to C are good, with A being the best.

[0308] L. Evaluation of the spreadability / peelability of raw slices

[0309] (i) Ceramic slurry preparation

[0310] 100 parts by weight of barium titanate (manufactured by Fuji Titan Industry Co., Ltd., trade name HPBT-1), 10 parts by weight of polyvinyl butyral (manufactured by Sekisui Chemicals Co., Ltd., trade name BL-1), 5 parts by weight of dibutyl phthalate, and 60 parts by weight of toluene-ethanol (mass ratio 30:30) were mixed / dispersed using a jet mill for 20 hours, and then filtered to prepare a paste-like ceramic slurry.

[0311] (ii) Formation of raw sheets

[0312] Using a die-coating machine, the obtained ceramic slurry is coated onto the aforementioned surface A of the biaxially oriented polyester film of the present invention with a final thickness of 0.7 μm, and then dried to form a green sheet.

[0313] (iii) Coating properties of ceramic slurry

[0314] The operation of forming a green sheet using ceramic slurry as described in item (ii) above was performed 10 times, the occurrence of depressions was visually evaluated, and the coatability of the ceramic slurry was evaluated based on the number of occurrences.

[0315] A: The dent occurs 0 out of 10 times.

[0316] B: The dent occurs more than once but less than three times out of ten.

[0317] C: The dents occur more than 4 times but less than 5 times out of 10.

[0318] D: The dents occurred more than 6 out of 10 times.

[0319] As for the coatability of ceramic slurry, A to C are good, with A being the best.

[0320] (iv) Peelability of raw slices

[0321] Similar to step (ii) above, the ceramic slurry prepared above was applied to the surface of the biaxially oriented polyester film of the present invention to a final thickness of 0.7 μm using a die-coating machine, and then dried to form a green sheet. An acrylic polyester adhesive tape (manufactured by Nitto Denko Co., Ltd., Nitto 31B tape, 19 mm wide) was bonded to the green sheet of the biaxially oriented polyester film as a support. The peel force (mN / 19 mm) was measured using a Shimadzu universal testing machine "Autograf AG-1S" at a peel angle of 180° and a tensile speed of 300 mm / min. The average peel force over 5 to 10 seconds was calculated from the peel force (mN / 19 mm) versus test time (sec) curve obtained by the measurement. Five measurements were performed, and the average of the three measurements after removing the maximum and minimum values ​​was taken as the peel force (mN / 19mm) of the biaxially oriented polyester film. The peel force of the raw film was evaluated.

[0322] A: The peel strength of the raw sheet is above 5mN / 19mm and below 20mN / 19mm.

[0323] B: The peel strength of the raw sheet is greater than 20mN / 19mm and less than 30mN / 19mm.

[0324] C: The peel strength of the raw sheet is greater than 30mN / 19mm and less than 50mN / 19mm.

[0325] D: The peel strength of the raw sheet is greater than 50mN / 19mm.

[0326] As for the peeling power of raw slices, A to C are good, with A being the best.

[0327] (v) The film breaks apart.

[0328] Regarding the five samples used for peel force testing in item (iv) above, the presence or absence of sheet breakage was confirmed for the raw sheets after peeling from the biaxially oriented polyester film, and the sheet breakage of the raw sheets was evaluated.

[0329] A: No film breakage was observed in any of the 5 images.

[0330] B: One out of five images shows a tear in the film.

[0331] C: Two out of five images show visible film tearing.

[0332] D: More than 3 out of 5 images show film tearing.

[0333] For raw slices, slice breakage is classified as A to C as good, with A being the best.

[0334] (vi) Surface defects after peeling of raw sheets

[0335] Regarding the peel surfaces (the surfaces that came into contact with the release resin coating layer) of the three biaxially oriented polyester films used to calculate the average peel force in item (iv) above, a scanning electron microscope (SEM) at 5000x was used to observe them to confirm the presence or absence of surface defects with an average equivalent circle diameter of 1 μm or more and surface defects with an average equivalent circle diameter of 0.5 μm or more, and the surface defects of the peeled green sheets were evaluated.

[0336] AA: No surface defects with an average equivalent circle diameter greater than 0.5 μm were observed in any of the three images.

[0337] A: No surface defects with an average equivalent circle diameter greater than 1.0 μm were observed in any of the three images.

[0338] B: One of the three images shows a surface defect with an average equivalent circle diameter greater than 1.0 μm.

[0339] C: Surface defects with an average equivalent circle diameter of more than 1.0 μm can be observed in 2 out of 3 images.

[0340] D: Surface defects with an average equivalent circle diameter of over 1.0 μm can be observed in all three images.

[0341] As surface defects after peeling of raw sheets, A to C are considered good, with AA being the best.

[0342] Example

[0343] The present invention will be described below with examples, but the present invention is not necessarily limited thereto.

[0344] [Manufacturing of PET-1] Dimethyl terephthalate (DMT) was mixed with 1.9 mol of ethylene glycol (relative to 1 mol of DMT), 0.05 parts by weight of magnesium acetate tetrahydrate (relative to 100 parts by weight of DMT), and 0.015 parts by weight of phosphoric acid, followed by heated transesterification. Then, 0.025 parts by weight of antimony trioxide was added, and the mixture was heated to a higher temperature and subjected to polycondensation under vacuum to obtain substantially particle-free polyester granules. The resulting melt-polymerized PET had a glass transition temperature of 81°C, a melting point of 255°C, and an intrinsic viscosity of 0.55.

[0345] The obtained polyester granules were then dried at 160°C for 6 hours to crystallize them, followed by solid-state polymerization at 220°C and a vacuum of 0.3 Torr for 8 hours to obtain solid-state polymerized PET. The obtained solid-state polymerized PET had a glass transition temperature of 81°C, a melting point of 255°C, and an intrinsic viscosity of 0.63.

[0346] [Manufacturing of PET-2]

[0347] The biaxially oriented polyester film obtained in Example 1 (described later) with the intermediate layer (P3 layer) composed solely of PET-1 resin was pulverized, remelted at 280°C, and extruded to obtain PET-2 as a recycled raw material. The obtained recycled raw material PET-2 has a glass transition temperature of 81°C, a melting point of 255°C, and an intrinsic viscosity of 0.60.

[0348] [Manufacturing of PET-3]

[0349] In Example 1 described later, the resin constituting the intermediate layer (P3 layer) was PET-1 only, and the silica-6 described later was contained in the P2 layer in such a way that it was 1.0% of the entire P2 layer. Otherwise, the film was formed in the same manner as in Example 1, and the coating layer was formed by online coating using the coating composition C described later, thereby obtaining a biaxially oriented polyester film with a coating layer.

[0350] On the surface of the coating layer of the obtained biaxially oriented polyester film (surface A above), after forming / peeling a green sheet according to the above-described "evaluation of coating / peelability of green sheet", the coating layer of the biaxially oriented polyester film was removed using an alkaline solution. The remaining biaxially oriented polyester film was then pulverized, remelted at 280°C, and extruded to obtain PET-3 as a recycled raw material. The obtained recycled raw material PET-3 has a glass transition temperature of 81°C, a melting point of 255°C, and an intrinsic viscosity of 0.59.

[0351] [Manufacturing of MB-A] During the polymerization of PET-1, silica particles (silica-1) with an average primary particle size of 65 nm, dispersed in ethylene glycol, were added at a rate of 1% by mass relative to PET to obtain PET-based masterbatch MB-A. The resulting melt-polymerized MB-A has a glass transition temperature of 81°C, a melting point of 255°C, and an intrinsic viscosity of 0.62.

[0352] [Manufacturing of MB-B to MB-G] MB-B to MB-G were obtained by changing the type of silica particles added as described in Table 1, otherwise operating in the same manner as MB-A. The properties of the obtained MB-B to MB-G are shown in Table 1.

[0353] 【surface@@

[0354]

[0355] [Mold Release Agent (A)]

[0356] • Resins containing long-chain alkyl groups (a-1)

[0357] 2-Hydroxyethyl acrylate (HEA) (manufactured by Kanto Chemical Co., Ltd.), α,α'-azobisisobutyronitrile (AIBN) (manufactured by Kanto Chemical Co., Ltd.) as a polymerization initiator, cumyl dithiobenzoate (CDB) as a RAFT agent, and toluene as a solvent were packaged into 25 mL pressure-resistant glass ampoules for polymerization at a weight ratio of HEA / CDB / AIBN / toluene = 0.35 / 0.03 / 0.007 / 2.27. Next, the mixed solution in the ampoule was degassed twice using a freeze-drying method, and the ampoule was then sealed and heated in an oil bath at 100°C for 18 hours to obtain a reaction solution containing the polymer.

[0358] Docdecyl acrylate, AIBN as a polymerization initiator, and toluene as a solvent were added to the reaction solution in the ampoule at a weight ratio of 4.65 / 0.003 / 1.3 g (docdecyl acrylate / AIBN / toluene). After two freeze-degassing cycles, the ampoule was sealed and heated at 100°C for 48 hours. Then, the polymerization solution was added dropwise to 20 times its weight of hexane and stirred to precipitate a solid. The obtained solid was filtered and dried under vacuum overnight at 40°C to obtain a resin containing long-chain alkyl groups (as a long-chain alkyl group-containing block copolymer having alkyl groups with 22 carbon atoms) (a-2).

[0359] The obtained resin (a-1) containing long-chain alkyl groups was emulsified as described below to prepare an aqueous resin emulsion. 375 g of water was added to a 1 L homogenizer, followed by 45 g of polyoxyethylene nonylphenyl ether, 30 g of polyoxyethylene polyoxypropylene glycol, 200 g of the long-chain alkyl-containing resin a1, and 150 g of toluene. The mixture was heated to 70 °C and stirred uniformly. The mixture was then transferred to a pressure homogenizer for emulsification, followed by further depressurization under heating to remove the toluene by distillation.

[0360] Polyether-modified polydimethylsiloxane

[0361] The polyether-modified polydimethylsiloxane (TSF4446; solid content concentration of 100%) produced by Momentibu was used.

[0362] [Resin or compound (B)]

[0363] • Organosilicon resin (b-1):

[0364] A coating agent containing organosilicon (model X-62-7655) manufactured by Shin-Etsu Chemical Industry Co., Ltd., a coating agent containing organosilicon (model X-62-7622) manufactured by Shin-Etsu Chemical Industry Co., Ltd., and a catalyst (model CAT-7605) manufactured by Shin-Etsu Chemical Industry Co., Ltd. were mixed in a mass ratio of 95:5:1.

[0365] Fluorinated organosilicon resin (b-2):

[0366] A coating agent containing silicone components (model KR-400) manufactured by Shin-Etsu Silicone Co., Ltd. was used.

[0367] • Acrylic resins (b-3)

[0368] Methyl methacrylate (α), hydroxyethyl methacrylate (β), and urethane acrylate oligomer (manufactured by Negami Kogyo Co., Ltd., Art Reigen (registered trademark) UN-3320HA, with 6 acryloyl groups) (γ) were loaded into a stainless steel reaction vessel at a mass ratio of (α) / (β) / (γ) = 94 / 1 / 5. Two parts by weight of sodium dodecylbenzenesulfonate as an emulsifier were added relative to 100 parts by weight of the total (α) to (γ) mixtures, and the mixture was stirred to prepare mixture 1. Next, a reaction apparatus equipped with a stirrer, reflux condenser, thermometer, and dropping funnel was prepared. 60 parts by weight of the above mixture 1, 200 parts by weight of isopropanol, and 5 parts by weight of potassium persulfate as a polymerization initiator were loaded into the reaction apparatus and heated to 60°C to prepare mixture 2. Mixture 2 was maintained at 60°C for 20 minutes. Next, a mixture 3 was prepared, consisting of 40 parts by weight of mixture 1, 50 parts by weight of isopropanol, and 5 parts by weight of potassium persulfate. Then, using a dropping funnel, mixture 3 was added dropwise to mixture 2 over a period of 2 hours to prepare mixture 4. Mixture 4 was then heated to 60°C and maintained for 2 hours. After cooling mixture 4 to below 50°C, it was transferred to a container equipped with a stirrer and a vacuum distillation apparatus. 60 parts by weight of 25% ammonia and 900 parts by weight of pure water were added, and while heating to 60°C, isopropanol and unreacted monomers were recovered under reduced pressure to obtain an acrylic resin (b-3) dispersed in pure water.

[0369] • Hydroxymethylated melamine resin (b-4)

[0370] The product used was "Nikarak" (registered trademark) MW-035 (70% by mass solids, solvent: water) manufactured by Sanwa Kemikal Co., Ltd.

[0371] • Acrylic polyol resins containing long-chain alkyl groups (b-5)

[0372] The process is carried out in the same manner as described in the acrylic resin (b-3) above, mixing in a ratio of 20 mol% stearyl methacrylate, 40 mol% hydroxyethyl methacrylate and 40 mol% methyl methacrylate, diluting with toluene to a solids concentration of 40% by mass, adding 0.5 mol% azobisisobutyronitrile under a nitrogen stream to copolymerize and obtain resin solution A.

[0373] • Hexamethoxyhydroxymethyl melamine (b-6)

[0374] [Blending of coating compositions A through C]

[0375] The release agent (A) and resin or compound (B) obtained as described above are mixed in the mass ratio of solid components as shown in Table 2 to prepare coating compositions A to C.

[0376] Table 2

[0377]

[0378] (Example 1)

[0379] PET-1, PET-2, MB-B, and MB-C were dried under reduced pressure at 180°C for 2.5 hours. They were then blended in the amounts of layers P1, P2, and P3 as listed in Table 3, and fed to three extruders for melt extrusion. After filtration, the mixture was combined in a stack of three layers (P1 / P3 / P2) using a feed block. It was then wound onto a cooling casting roller maintained at 42°C using an electrostatic casting method via a T-die for cooling and solidification, yielding an unstretched film. This unstretched film was then introduced between the opposing electrode and grounding roller. Nitrogen gas was introduced into the device, and the processing intensity (E value) was 250 W·min / m³. 2 Under these conditions, the surface of the P1 layer was subjected to plasma treatment using atmospheric pressure glow discharge.

[0380] After the treated unstretched film passes through an antistatic roller with the roller temperature set to 30°C, it is subjected to sequential biaxial stretching under the conditions described in Table 4. First, in the length direction, it is fed into a stretching roller group heated to 60°C to 100°C and stretched at a total ratio of 3.8 times through three stages of stretching operation. Then, it is fed into a tenter frame and stretched 4.4 times in the width direction at a stretching temperature of 90°C to 140°C. After heat treatment at 235°C at a fixed length, a 3% relaxation treatment is performed in the width direction to obtain a biaxially oriented polyester film with a thickness of 35 μm.

[0381] [Table 3]

[0382]

[0383] [Table 4]

[0384]

[0385] The composition, particle content, surface properties, and membrane properties of the obtained biaxially oriented polyester film are shown in Tables 5 and 6.

[0386] Furthermore, the surface properties of the P1 layer, with polyester resin as the main component, are as follows. The first 5% of the maximum protrusion height: 75 nm.

[0387] Number of protrusions with a height of 80nm or more: 0.1 per mm 2

[0388] Number of protrusions with a height of 10nm or more: 500 / mm2

[0389] [Table 5]

[0390]

[0391] [Table 6]

[0392] Table 6

[0393]

[0394] Next, coating composition A is applied to the surface of layer P1 of the obtained biaxially oriented polyester film using a gravure coating method, as described in Table 7. The coating is then dried at 100°C for 30 seconds to form a coating layer (R1) with a final thickness of 0.1 μm, thus obtaining the biaxially oriented polyester film. The biaxially oriented polyester film consists of four layers: R1 layer, P1 layer, P3 layer, and P2 layer. Furthermore, the thickness of the obtained biaxially oriented polyester film with the coating layer is uneven, as described in Table 7.

[0395] As shown in Table 8, the film exhibits good process transportability (surface damage defects, surface scraping), winding properties (winding wrinkles, winding misalignment), and coating / peelability with the raw sheet (coating properties (dents), peeling properties, sheet breakage, surface defects).

[0396] [Table 7]

[0397]

[0398] [Table 8]

[0399]

[0400] (Examples 2-4)

[0401] In Example 2, the P1 layer contained particles at the concentration shown in Table 3. In Examples 3 and 4, the particle composition of the P2 layer was changed as shown in Table 3. Otherwise, the procedure was the same as in Example 1, resulting in a biaxially oriented polyester film with a thickness of 35 μm. The composition, particle content analysis, surface properties, and film properties of the obtained biaxially oriented polyester films are shown in Tables 5-7.

[0402] In addition, the surface characteristics of the P1 layer surface with polyester resin as the main component in Examples 2 to 4 are as follows.

[0403] (Example 2)

[0404] The first 5% of the maximum protrusion height: 110nm

[0405] Number of protrusions with a height of 80nm or more: 0.3 per mm 2

[0406] Number of protrusions with a height of 10nm or more: 700 / mm 2

[0407] (Examples 3 and 4)

[0408] The first 5% of the maximum protrusion height: 75nm

[0409] Number of protrusions with a height of 80nm or more: 0.1 per mm 2

[0410] Number of protrusions with a height of 10nm or more: 500 / mm 2

[0411] As shown in Table 8, the evaluation of production adaptability and application adaptability in Example 2, although surface scraping, sheet breakage, and surface defects worsened compared to Example 1, were still within practical limits. The film exhibits other properties as good as that of Example 1.

[0412] In Example 3, although the winding misalignment and surface defects of the green sheet worsened compared to Example 1, they were still within practical limits. The film exhibits other properties as good as those in Example 1.

[0413] In Example 4, although the winding wrinkles deteriorated compared to Example 1, they remained within practical limits. The film exhibits other properties as good as that of Example 1.

[0414] (Examples 5 and 6)

[0415] In Examples 5 and 6, the layer thickness of P1 was changed as described in Table 4. Otherwise, the procedure was the same as in Example 1, resulting in biaxially oriented polyester films with a thickness of 35 μm. The composition, particle content analysis, surface properties, and film properties of the obtained biaxially oriented polyester films are shown in Tables 5-7.

[0416] In addition, the surface characteristics of the P1 layer surface with polyester resin as the main component in Examples 5 and 6 are as follows.

[0417] (Example 5)

[0418] The first 5% of the maximum protrusion height: 90nm

[0419] Number of protrusions with a height of 80nm or more: 0.4 per mm 2

[0420] Number of protrusions with a height of 10nm or more: 600 / mm2

[0421] (Example 6)

[0422] The first 5% of the maximum protrusion height: 95nm

[0423] Number of protrusions with a height of 80nm or more: 0.5 per mm 2

[0424] Number of protrusions with a height of 10nm or more: 650 / mm 2

[0425] As shown in Table 8, the evaluation of production adaptability and application adaptability showed that surface scratching and sheet cracking in Example 5 were worse than in Example 1, and sheet cracking in Example 6 was further worse. Surface defects were also worse than in Example 1, but all were within practical limits. Other properties were as good as in Example 1.

[0426] (Examples 7-9)

[0427] In Examples 7-9, the processing intensity of the plasma treatment using atmospheric pressure glow discharge was changed as described in Table 4. Otherwise, the procedure was the same as in Example 1, and a biaxially oriented polyester film with a thickness of 35 μm was obtained. The composition, particle content analysis, surface properties, and film properties of the obtained biaxially oriented polyester film are shown in Tables 5-7.

[0428] In addition, the surface characteristics of the P1 layer surface, which uses polyester resin as the main component, in Examples 7 to 9 are as follows.

[0429] (Example 7)

[0430] The first 5% of the maximum protrusion height: 75nm

[0431] Number of protrusions with a height of 80nm or more: 0.06 per mm 2

[0432] Number of protrusions with a height of 10nm or more: 400 / mm 2

[0433] (Example 8)

[0434] The first 5% of the maximum protrusion height: 75nm

[0435] Number of protrusions with a height of 80nm or more: 0.1 per mm 2

[0436] Number of protrusions with a height of 10nm or more: 330 / mm 2

[0437] (Example 9)

[0438] The first 5% of the maximum protrusion height: 75nm

[0439] Number of protrusions with a height of 80nm or more: 0.1 per mm 2

[0440] Number of protrusions with a height of 10nm or more: 300 / mm 2

[0441] As shown in Table 8, the evaluation of production adaptability and application adaptability showed that the surface damage defects in Example 7 were worse than those in Example 1. In addition to surface damage defects, winding misalignment and raw sheet surface defects in Examples 8 and 9 were also worse than those in Example 1, but all remained within practical limits. Other properties were as good as those in Example 1.

[0442] (Examples 10-12)

[0443] In Examples 10 and 11, the coating composition applied to the biaxially oriented polyester film was changed as described in Table 7. In Example 12, the thickness of the coating layer was changed as described in Table 7. Otherwise, the procedure was the same as in Example 1, and a biaxially oriented polyester film with a thickness of 35 μm was obtained. The composition, particle content analysis, surface properties, and film properties of the obtained biaxially oriented polyester film are shown in Tables 5 to 7.

[0444] In addition, the surface characteristics of the P1 layer surface, which uses polyester resin as the main component, in Examples 10-12 are as follows.

[0445] (Examples 10-12)

[0446] The first 5% of the maximum protrusion height: 75nm

[0447] Number of protrusions with a height of 80nm or more: 0.1 per mm 2

[0448] Number of protrusions with a height of 10nm or more: 500 / mm 2

[0449] As shown in Table 8, the evaluation of production adaptability and application adaptability shows that in Example 10, the coatability of the raw sheet is better than that of Example 1, and in Examples 11 and 12, the peelability of the raw sheet is better than that of Example 1. Other properties are as good as those of Example 1.

[0450] (Example 13)

[0451] In Example 13, the composition of the biaxially oriented polyester film was changed as described in Tables 3 and 4, and it was set to a two-layer composition. Otherwise, the operation was the same as in Example 1, and a biaxially oriented polyester film with a thickness of 35 μm was obtained. The composition, particle content analysis, surface properties, and film properties of the obtained biaxially oriented polyester film are shown in Tables 5 to 7.

[0452] In addition, the surface characteristics of the P1 layer surface in Example 13, which uses polyester resin as the main component, are as follows.

[0453] The first 5% of the maximum protrusion height: 110nm

[0454] Number of protrusions with a height of 80nm or more: 0.4 per mm 2

[0455] Number of protrusions with a height of 10nm or more: 600 / mm 2

[0456] As shown in Table 8, the evaluation of production adaptability and application adaptability in Example 13, although the surface scraping, sheet cracking, and surface defects worsened compared to Example 1, were still within practical limits. It is a film with other properties as good as Example 1.

[0457] (Example 14)

[0458] In Example 14, the composition of the biaxially oriented polyester film was changed as described in Tables 3 and 4. Otherwise, the procedure was the same as in Example 1, and a biaxially oriented polyester film with a thickness of 35 μm was obtained. The composition, particle content analysis, surface properties, and film properties of the obtained biaxially oriented polyester film are shown in Tables 5 to 7.

[0459] In addition, the surface characteristics of the P1 layer surface in Example 14, which uses polyester resin as the main component, are as follows.

[0460] The first 5% of the maximum protrusion height: 85nm

[0461] Number of protrusions with a height of 80nm or more: 0.3 per mm 2

[0462] Number of protrusions with a height of 10nm or more: 550 / mm 2

[0463] As shown in Table 8, the evaluation of production adaptability and application adaptability in Example 14, although the surface scraping and sheet breakage of the green sheet deteriorated compared to Example 1, were still within the practical range. Other properties were as good as those in Example 1.

[0464] (Examples 15 and 16)

[0465] In Examples 15 and 16, the composition of the biaxially oriented polyester film was modified by using PET-3, a recycled raw material, in the P3 layer, which serves as the intermediate layer. Other than this, the operation was the same as in Example 1, resulting in a biaxially oriented polyester film with a thickness of 35 μm composed of three laminated layers. The composition, particle content analysis, surface properties, and film properties of the obtained biaxially oriented polyester film are shown in Tables 5-7.

[0466] In addition, the surface characteristics of the P1 layer surface with polyester resin as the main component in Examples 15 and 16 are as follows.

[0467] (Example 15)

[0468] The first 5% of the maximum protrusion height: 100nm

[0469] Number of protrusions with a height of 80nm or more: 0.4 per mm 2

[0470] Number of protrusions with a height of 10nm or more: 700 / mm 2

[0471] (Example 16)

[0472] The first 5% of the maximum protrusion height: 85nm

[0473] Number of protrusions with a height of 80nm or more: 0.3 per mm 2

[0474] Number of protrusions with a height of 10nm or more: 600 / mm 2

[0475] As shown in Table 8, the evaluation of production adaptability and application adaptability in Example 15 contained particles with a diameter greater than 800 nm, which showed a very large peak in the volumetric particle size distribution analysis. Therefore, sheet breakage and surface defects were worse compared to Example 1. Example 16 made the P1 layer thicker than that in Example 15, thereby improving surface defects. On the other hand, sheet breakage was worse compared to Example 1, but both were within practical ranges. The film has other properties as good as that of Example 1.

[0476] (Example 17)

[0477] In Example 17, the composition of the biaxially oriented polyester film was changed as described in Tables 3 and 4. Otherwise, the procedure was the same as in Example 1, and a biaxially oriented polyester film with a thickness of 35 μm was obtained. The composition, particle content analysis, surface properties, and film properties of the obtained biaxially oriented polyester film are shown in Tables 5 to 7.

[0478] In addition, the surface characteristics of the P1 layer surface in Example 17, which uses polyester resin as the main component, are as follows.

[0479] The first 5% of the maximum protrusion height: 75nm

[0480] Number of protrusions with a height of 80nm or more: 0.1 per mm 2

[0481] Number of protrusions with a height of 10nm or more: 500 / mm 2

[0482] As shown in Table 8, the production adaptability and application adaptability evaluations indicate that although the winding wrinkles in Example 17 deteriorated compared to Example 1, they remain within practical limits. Other properties are as good as those of Example 1.

[0483] (Example 18)

[0484] In Example 18, the composition of the coating layer and the coating thickness were changed as described in Table 7 for the biaxially oriented polyester film. Otherwise, the procedure was the same as in Example 1, and a biaxially oriented polyester film with a thickness of 35 μm was obtained. The composition, particle content analysis, surface properties, and film properties of the obtained biaxially oriented polyester film are shown in Tables 5-7.

[0485] In addition, the surface characteristics of the P1 layer surface in Example 18, which uses polyester resin as the main component, are as follows.

[0486] The first 5% of the maximum protrusion height: 75nm

[0487] Number of protrusions with a height of 80nm or more: 0.1 per mm 2

[0488] Number of protrusions with a height of 10nm or more: 500 / mm 2

[0489] As shown in Table 8, the evaluation of production adaptability and application adaptability of Example 18, although the surface scraping and demolding properties of the green sheet deteriorated compared to Example 1, were still within the practical range. It is a film with other properties as good as Example 1.

[0490] (Comparative Example 1)

[0491] In Comparative Example 1, the particles contained in the P1 layer were changed as described in Table 3. Otherwise, the procedure was the same as in Example 1, and a biaxially oriented polyester film with a thickness of 35 μm was obtained. The composition, particle content analysis, surface properties, and film properties of the obtained biaxially oriented polyester film are shown in Tables 5-7.

[0492] Furthermore, the surface characteristics of the P1 layer surface in Comparative Example 1, which uses polyester resin as the main component, are described below.

[0493] The first 5% of the maximum protrusion height: 130nm

[0494] Number of protrusions with a height of 80nm or more: 0.5 per mm 2

[0495] Number of protrusions with a height of 10nm or more: 600 / mm 2

[0496] As shown in Table 8, the production adaptability and application adaptability evaluations of Comparative Example 1 show that the film formed in Comparative Example 1 has significantly deteriorated film quality in terms of sheet breakage and surface defects compared to Example 1.

[0497] (Compare Examples 2 and 3)

[0498] In Comparative Examples 2 and 3, the particles contained in the P2 layer were changed as described in Table 3. Otherwise, the procedure was the same as in Example 1, and a biaxially oriented polyester film with a thickness of 35 μm was obtained. The composition, particle content analysis, surface properties, and film properties of the obtained biaxially oriented polyester film are shown in Tables 5 to 7.

[0499] Furthermore, the surface characteristics of the P1 layer surface in Comparative Examples 2 and 3, which uses polyester resin as the main component, are described below.

[0500] The first 5% of the maximum protrusion height: 75nm

[0501] Number of protrusions with a height of 80nm or more: 0.1 per mm 2

[0502] Number of protrusions with a height of 10nm or more: 500 / mm 2

[0503] As shown in Table 8, the evaluation of production adaptability and application adaptability resulted in a film with significantly worse winding misalignment compared to Example 1 in Comparative Example 2, and a film with significantly worse surface damage defects and winding wrinkles compared to Example 1 in Comparative Example 3.

[0504] (Comparative Example 4)

[0505] In Comparative Example 4, the particles contained in the P1 layer were changed as described in Table 3. Otherwise, the procedure was the same as in Example 1, and a biaxially oriented polyester film with a thickness of 35 μm was obtained. The composition, particle content analysis, surface properties, and film properties of the obtained biaxially oriented polyester film are shown in Tables 5-7.

[0506] Furthermore, the surface characteristics of the P1 layer surface in Comparative Example 4, which uses polyester resin as the main component, are described below.

[0507] The first 5% of the maximum protrusion height: 115nm

[0508] Number of protrusions with a height of 80nm or more: 0.6 per mm 2

[0509] Number of protrusions with a height of 10nm or more: 850 / mm 2

[0510] As shown in Table 8, the production adaptability and application adaptability evaluations of Comparative Example 4 showed that the film with sheet breakage and surface defects was significantly worse than that of Example 1.

[0511] Industry availability

[0512] The biaxially oriented polyester film of the present invention has a release coating surface with excellent smoothness and a back surface with excellent smoothness. As a result, even after being wound into rolls, there is less transfer of the uneven shape to the surface of the green sheet, excellent coating / peelability, and it does not lose its smoothness even when recycled materials are used in the intermediate layer. Therefore, it is suitable for use as a process film for release of green sheets with low environmental impact.

[0513] Explanation of reference numerals in the attached figures

[0514] 1. A layer with side A (P1 layer or R1 layer)

[0515] 2. Surface with protrusions (Surface A)

[0516] 3. Zero plane (average plane; height 0 nm) in scanning white interferometry measurements.

[0517] 4. 10nm height line (R) 10nm )

[0518] 5. Height 80nm line (R) 80nm )

[0519] 6. Protrusions present on surface A

[0520] 7. The protrusion with the highest protrusion height value belonging to the top 5% of the maximum protrusion height values ​​in each field of view with surface A.

[0521] 8. The maximum protrusion height value that belongs to the top 5% of the maximum protrusion height values ​​in each field of view of surface A (Sp5%A).

[0522] 9. The protrusion with the greatest height existing on surface A.

[0523] 10. Layer with side B (P2 layer)

[0524] 11. The opposite side (side B) of the aforementioned side A, which has a protrusion.

[0525] 12. Protrusions on side B

[0526] 13. The protrusion of the maximum protrusion height value that belongs to the top 5% of the maximum protrusion height values ​​in each field of view with B-side.

[0527] 14. The maximum protrusion height value (Sp5%B) that belongs to the top 5% of the maximum protrusion height values ​​in each field of view of plane B.

[0528] 15. The protrusion with the greatest height on side B.

[0529] 16. Polyester resin layer (P1 layer) with side A

[0530] 17. Intermediate Layer (P3 Layer)

[0531] 18. Layer with side B (P2 layer)

[0532] 19. Biaxially oriented polyester film

[0533] 20. Coating layer with side A (R1 layer)

[0534] 21. Biaxially oriented polyester film with a coating layer

Claims

1. A biaxially oriented polyester film having a surface A satisfying the following condition (1), and a surface B opposite to surface A satisfying the following condition (2). Condition (1): The surface A has a protrusion, and the maximum protrusion height that belongs to the top 5% of the maximum protrusion height values ​​in each field of view obtained by the following method is denoted as Sp5%A, where Sp5%A is less than 110 nm. Condition (2): The B-surface has a protrusion, and the maximum protrusion height, which is among the top 5% of the maximum protrusion height values ​​obtained by the following method in each field of view, is denoted as Sp5%B. Sp5%B is 150nm or more and 1000nm or less. Method for determining the maximum protrusion height: Using a VertScan scanning white interference microscope with a 10x objective lens, surface images of a 561 μm square field of view were measured in 100 fields of view. The maximum protrusion height Sp value in each field of view was calculated, and the top 5% of these Sp values ​​were taken as the Sp5% value. Let the layer having the B side be designated as layer P2, and the thickness of layer P2 be designated as T. P2 The maximum particle size contained in layer P2 is denoted as D. P2 In the case of T P2 / D P2 The T is 1 or more and 5 or less. P2 and D P2 The unit is μm.

2. The biaxially oriented polyester film according to claim 1, wherein protrusions exist on the surface of side A, and the number of protrusions with a height of 80 nm or more is denoted as N. 80nm In case A, N 80nm A is 0.4 pieces / mm 2 the following.

3. The biaxially oriented polyester film according to claim 2, wherein protrusions exist on the surface of side A, and the number of protrusions with a height of 10 nm or more is denoted as N. 10nm In case A, N 10nm A is 300 pieces / mm 2 More than 1000 pieces / mm 2 the following.

4. The biaxially oriented polyester film according to any one of claims 1 to 3, comprising a layer P1 with polyester resin as the main component, wherein the surface of the P1 layer is the outermost surface of the biaxially oriented polyester film, and the P1 layer has the A side.

5. The biaxially oriented polyester film according to claim 4, wherein the thickness of the P1 layer is denoted as T. P1 In the case of T P1 It is between 2μm and 10μm.

6. The biaxially oriented polyester film according to claim 4, wherein the P1 layer contains particles, and the maximum particle size of the particles contained in the P1 layer is denoted as D. P1 In the case of T P1 / D P1 The value of D is between 20 and 100. P1 The unit is μm.

7. The biaxially oriented polyester film according to claim 1, wherein the water contact angle of the A-side is denoted as CaR, and CaR is 100° or more and 120° or less.

8. The biaxially oriented polyester film according to claim 7, comprising a layer P1 with polyester resin as the main component and a coating layer R1, wherein the R1 layer is disposed on the P1 layer, the surface of the R1 layer is the outermost surface of the biaxially oriented polyester film, and the R1 layer has the A side.

9. The biaxially oriented polyester film according to claim 8, wherein the R1 layer is composed of at least one of silicone resin, long-chain alkyl resin and acrylic resin as the main component.

10. The biaxially oriented polyester film according to claim 8, wherein the thickness of the R1 layer is denoted as T. R1 In the case of T R1 It is above 0.01μm and below 1.00μm.

11. The biaxially oriented polyester film according to claim 4, wherein the biaxially oriented polyester film has a configuration of at least three layers, such that a particle-containing P3 layer is present between the P1 layer and the P2 layer.

12. The biaxially oriented polyester film according to any one of claims 1 to 3, wherein the P2 layer contains two or more types of particles with different average particle sizes.

13. The biaxially oriented polyester film according to any one of claims 1 to 3, wherein the film thickness is measured in the film width direction, i.e., in the same direction as the film roll width direction, and the average film thickness is denoted as T. AVE The maximum film thickness is denoted as T. MAX And denote the minimum value as T. MIN In the case where the thickness non-uniformity ΔT, as expressed by the following equation (1), is less than 5.0%, the T... AVE T MAX and T MIN The unit is μm. ΔT (%) = 100 × (T) MAX -T MIN ) / T AVE ...Formula (1).

14. The biaxially oriented polyester film according to any one of claims 1 to 3, wherein the static friction coefficient between the A-side and the B-side is 0.8 or less.

15. The biaxially oriented polyester film according to any one of claims 1 to 3, which is used as a support film for green sheet forming in the process of manufacturing multilayer ceramic capacitors.

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