Laminated polyester film and release film for forming resin sheet

Abstract

The purpose of the present invention is to provide a laminated polyester film capable of effectively suppressing winding misalignment after mold release while ensuring winding characteristics of a large roll before mold release. The laminated polyester film has a layer A and a layer B on the front surface and the back surface. The layer A contains particles having a particle size distribution in which the frequency of the average particle diameter (D50) is 13% or more. The B layer has a surface on which the release layer is provided. The static friction coefficient ([mu] s) when the surface of the B layer and the surface of the A layer are in contact with each other is 0.3-0.6. The laminated polyester film is used as a release film for forming a resin sheet.

Description

Technical Field

[0001] The present invention relates to a laminated polyester film having at least two layers, and a release film for forming a resin sheet having a release layer provided on the surface of the laminated polyester film. Background Art

[0002] Release films based on polyethylene terephthalate films are used to form ceramic products such as laminated ceramic capacitors and ceramic substrates. In recent years, as the miniaturization and high-capacity of laminated ceramic capacitors have progressed, there has been a trend toward increasingly thinner ceramic green sheets (hereinafter sometimes referred to as "green sheets" or "ceramic sheets," etc.). As ceramic green sheets become thinner, especially when forming thin film green sheets with a thickness of less than 1 μm, various problems may arise if there are large protrusions on the release surface of the release film. For example, when applying ceramic slurry on the release film, the slurry shrinks or pinholes are generated, and when peeling the green sheet, the green sheet breaks. When such problems occur, the defective rate of the laminated ceramic capacitor deteriorates.

[0003] To achieve the flattened surface of the release film, the layer opposite the release layer (Layer A) contains particles to enhance winding properties. If coarse protrusions also form on the surface of Layer A, which contains particles, there is a risk of pinholes forming in the ceramic green sheet. Therefore, small particles are added to Layer A at a high concentration. A release agent is then applied to the flattened Layer B, completing the winding process before coating the green sheet.

[0004] For example, Patent Document 1 discloses a film having substantially no lubricant on the surface to be coated with a release agent.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-305806 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] In recent years, the further thinning of green sheets and the accompanying improvements in release formulations have led to changes in peel strength, static friction coefficient, and other properties. Consequently, after release coating, the static friction coefficients of the front and back sides of the film change to a low value, causing slippage between the front and back sides of the film during roll winding, leading to roll misalignment. Furthermore, vibration during roll transport can cause further roll misalignment.

[0010] Simply reducing the amount of pellets added in conventional formulations increases the static friction coefficient and improves winding misalignment after demolding. However, this deteriorates the winding properties of large rolls in biaxially oriented film production before demolding, leading to problems such as wrinkles (specifically, convex wrinkles formed by air entrainment during large roll winding) and reduced flatness. Large rolls are defined as rolls with a width of 5 meters or more.

[0011] An object of the present invention is to provide a laminated polyester film that can ensure the winding properties of a large roll before the demolding process and effectively suppress the winding displacement after the demolding process.

[0012] Solutions for solving problems

[0013] The present invention may include the following configurations.

[0014] 1. A laminated polyester film for use as a release film for forming a resin sheet, characterized in that it is a laminated polyester film having an A layer and a B layer on the front and back surfaces,

[0015] The A layer contains particles having a particle size distribution with an average particle size (D50) frequency of 13% or more, the B layer contains substantially no particles, and the surface roughness SRa of the B layer is 0.004 μm or less.

[0016] The static friction coefficient (μs) when the surface of the B layer and the surface of the A layer are in contact with each other is 0.3 or more and 0.6 or less.

[0017] 2. The laminated polyester film according to 1. above, wherein the intrinsic viscosity is 0.50 dl / g to 0.65 dl / g.

[0018] 3. The laminated polyester film according to 1. or 2. above, wherein the particles in layer A are silica particles, and the average particle size (D50) of the silica particles is 0.6 μm or more and 1.5 μm or less.

[0019] 4. The laminated polyester film according to any one of 1. to 3. above, which has a thickness of 12 μm to 50 μm.

[0020] 5. The laminated polyester film according to any one of 1. to 4. above, wherein at least one of layer A and layer B comprises at least ethylene glycol and terephthalic acid as constituent components.

[0021] At least one of the ethylene glycol and the terephthalic acid is derived from a biomass resource.

[0022] 6. A release film for forming a resin sheet, comprising:

[0023] The laminated polyester film according to any one of 1. to 5. above; and

[0024] A release layer provided on the surface of layer B of a laminated polyester film.

[0025] It should be noted that the above-mentioned structure 1. can also be expressed as follows.

[0026] A laminated polyester film for use as a release film for forming a resin sheet, comprising a first surface and a second surface opposite to the first surface.

[0027] The laminated polyester film comprises:

[0028] A layer having a first surface, and

[0029] A layer B having a second side,

[0030] Layer A contains particles with an average particle size (D50) of 13% or more.

[0031] The B layer contains substantially no particles, and the surface roughness SRa of the second surface is less than 0.004 μm.

[0032] The static friction coefficient (μs) when the second surface and the first surface are in contact with each other is 0.3 or more and 0.6 or less.

[0033] The present invention may also include the following configurations.

[0034] 11. A laminated polyester film for use as a release film for forming a resin sheet, the laminated polyester film comprising a layer A and a layer B on the front and back surfaces thereof,

[0035] The A layer contains particles having a particle size distribution in which the frequency of the average particle diameter (D50) is 13% or more, and the B layer has a surface for providing a release layer.

[0036] The static friction coefficient (μs) when the surface of the B layer and the surface of the A layer are in contact with each other is 0.3 or more and 0.6 or less.

[0037] 12. The laminated polyester film according to 11. above, which has an intrinsic viscosity of 0.50 dl / g to 0.65 dl / g.

[0038] 13. The laminated polyester film according to 11. or 12. above, wherein the particles in layer A are silica particles, and the average particle size (D50) of the silica particles is 0.6 μm or more and 1.5 μm or less.

[0039] 14. The laminated polyester film according to any one of 11. to 13. above, which has a thickness of 12 μm to 50 μm.

[0040] 15. The laminated polyester film according to any one of 11. to 14. above, wherein at least one of the layer A and the layer B comprises at least ethylene glycol and terephthalic acid as constituent components.

[0041] At least one of the ethylene glycol and the terephthalic acid is derived from a biomass resource.

[0042] 16. The laminated polyester film according to any one of 11. to 15. above, wherein the surface roughness SRa of the layer B is 0.004 μm or less.

[0043] 17. The laminated polyester film according to any one of 11. to 16. above, wherein the layer B contains substantially no particles.

[0044] 18. A release film for forming a resin sheet, comprising:

[0045] The laminated polyester film according to any one of 11. to 17. above; and

[0046] A release layer provided on the surface of layer B of a laminated polyester film.

[0047] It should be noted that the above-mentioned structure of 11. can also be expressed as follows.

[0048] A laminated polyester film for use as a release film for forming a resin sheet, comprising a first surface and a second surface opposite to the first surface.

[0049] The laminated polyester film comprises:

[0050] A layer having a first surface, and

[0051] A layer B having a second side,

[0052] Layer A contains particles with an average particle size (D50) of 13% or more.

[0053] The second side is the surface for setting the release layer.

[0054] The static friction coefficient (μs) when the second surface and the first surface are in contact with each other is 0.3 or more and 0.6 or less.

[0055] Effects of the Invention

[0056] The present invention provides a laminated polyester film that maintains good winding properties for large rolls before demolding and suppresses winding misalignment after demolding. For example, increasing conveying speeds during processing can trap air as the film is wound, increasing the thickness of the interlayer air layer when the film is wound, which can adversely affect film winding misalignment. As a result, the present invention can suppress winding misalignment caused by high speeds compared to conventional methods. Furthermore, the present invention can also suppress winding misalignment by improving the release formulation to impart slippage. DETAILED DESCRIPTION

[0057] (first)

[0058] The laminated polyester film according to the embodiment of the present invention has the following configuration.

[0059] A laminated polyester film for use as a release film for forming a resin sheet, characterized in that it is a laminated polyester film having an A layer and a B layer on the front and back surfaces, the A layer containing particles having a particle size distribution with an average particle size (D50) having a frequency of 13% or more, and the static friction coefficient (μs) when the surface of the B layer and the surface of the A layer are in contact with each other is 0.3 or more and 0.6 or less.

[0060] Here, “a laminated polyester film having layer A and layer B on the front and back surfaces” means a laminated polyester film in which one surface of both surfaces is the surface of layer A and the other surface is the surface of layer B.

[0061] The "laminated polyester film for a release film for forming a resin sheet" refers to a laminated polyester film used as a base film of a release film (specifically, a release film for forming a resin sheet).

[0062] The "average particle size (D50)" refers to the particle size at which the cumulative frequency (i.e., cumulative number) reaches 50% in a number-based cumulative distribution. Hereinafter, the average particle size (D50) may be referred to as D50, D50 particle size, median particle size, or 50% particle size.

[0063] The “frequency of the average particle size (D50)” (hereinafter also referred to as D50 frequency) is the frequency of the interval (ie, particle size interval) where the cumulative frequency reaches 50% in a histogram of the frequency distribution based on the number of particles.

[0064] In the examples described below, D50 and D50 frequency are determined based on the definitions described here. D50 frequency and D50 are values measured using the methods described in the examples described below.

[0065] According to the laminated polyester film of the embodiment of the present invention, the static friction coefficient (μs) is 0.3 or greater, that is, the static friction coefficient (μs) is not excessively low. Therefore, when the laminated polyester film is subjected to a release process (that is, when a release layer is formed on the laminated polyester film), winding displacement that may occur when the laminated polyester film (that is, the release film) after the release process is wound can be suppressed. In other words, winding displacement after the release process can be suppressed.

[0066] Furthermore, the static friction coefficient (μs) is 0.6 or less, meaning it is not excessively high. Therefore, when air is trapped between the laminated polyester films during winding (i.e., when the laminated polyester films entrap air), the laminated polyester films can slide around the trapped air. This allows the trapped air to escape or disperse. Consequently, wrinkles that may form when the laminated polyester film is wound (specifically, convex wrinkles formed by air entrained during winding) can be reduced.

[0067] Furthermore, the frequency of the average particle size (D50) of the particles in layer A is 13% or greater, meaning that the particle size distribution of the particles in layer A is sharp. This reduces the likelihood of large protrusions forming in layer A due to excessively large particles, thereby reducing the frequency of air inclusion between the laminated polyester film. Consequently, wrinkles that may form when the laminated polyester film is wound can be further reduced.

[0068] Hereinafter, embodiments of the present invention will be described in detail.

[0069] (Laminated polyester film)

[0070] The laminated polyester film of the present invention is a laminated polyester film (hereinafter also referred to as a base film) having a laminated structure having at least a layer A and a layer B (hereinafter also referred to as a surface layer B) on the front and back surfaces. For example, a release film can be obtained by forming a release layer on at least the surface of the layer B of the base film of the present invention.

[0071] Examples of substrate films include films made from polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, or copolymers primarily composed of these resins. Biaxially stretched polyethylene terephthalate films are particularly preferred due to their mechanical properties, heat resistance, transparency, and cost. Layers A and B in the present invention may have different or identical resins as their primary components.

[0072] When a copolymer is used in a substrate film, examples of the dicarboxylic acid component include aliphatic dicarboxylic acids such as adipic acid and sebacic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid; and polyfunctional carboxylic acids such as trimellitic acid and pyromellitic acid. Furthermore, examples of the diol component include fatty acid diols such as ethylene glycol, diethylene glycol, 1,4-butanediol, propylene glycol, and neopentyl glycol; aromatic diols such as terephthalic alcohol; alicyclic diols such as 1,4-cyclohexanedimethanol; and polyethylene glycol having an average molecular weight of 150 to 20,000. The copolymer preferably has a mass ratio of the copolymer components of less than 20% by mass. By having a mass ratio of less than 20% by mass, good film strength, transparency, and heat resistance can be achieved.

[0073] In the present invention, at least one of layer A and layer B preferably contains at least ethylene glycol and terephthalic acid as components, more preferably containing ethylene glycol and terephthalic acid as main components. Furthermore, at least one of ethylene glycol and terephthalic acid may be derived from petroleum or biomass, i.e., from a biomass resource. Of these, at least one is preferably derived from a biomass resource, more preferably from a plant. When a polyester resin derived from petroleum is mixed with a polyester resin derived from a biomass raw material, the biomass content is preferably 5% or greater, more preferably 9% or greater, and even more preferably 9.5% or greater from the perspective of reducing environmental impact. A biomass content within this range can effectively reduce environmental impact.

[0074] The biomass degree is preferably 100%, but may be, for example, 90% or less. In one embodiment, the biomass degree is 9% or more and 30% or less, for example, 9% or more and 20% or less.

[0075] For example, polyethylene terephthalate (PET) theoretically has a biomass content of 20% by using only ethylene glycol as a plant source. However, to achieve a biomass content exceeding this, the terephthalic acid must also be derived from plants, which increases costs. Biomass content is the ratio of plant-derived carbon to total carbon content, as measured according to ASTM D6866.

[0076] The intrinsic viscosity of the resin pellets used for producing the substrate film is preferably in the range of 0.45 dl / g to 0.70 dl / g, more preferably 0.47 dl / g to 0.70 dl / g, and even more preferably 0.50 dl / g to 0.65 dl / g.

[0077] When the intrinsic viscosity is 0.50 dl / g or higher, tear resistance is improved. When the intrinsic viscosity is 0.70 dl / g or lower, the increase in filtration pressure is reduced, stable discharge is possible, and the thickness of the film in the flow direction can be made uniform.

[0078] The description of the intrinsic viscosity of the base film overlaps with the description of the intrinsic viscosity of the resin pellets used in producing the base film and is therefore omitted. Therefore, the description of the intrinsic viscosity of the resin pellets can also be treated as the description of the intrinsic viscosity of the base film.

[0079] The intrinsic viscosity is measured by the following method.

[0080] The film or polyester resin was pulverized and dried, then dissolved in a 60 / 40 (mass ratio) mixed solvent of phenol and tetrachloroethane. The solution was centrifuged to remove inorganic particles. The flow time of the solution at a concentration of 0.4 g / dl at 30°C and the flow time of the solvent alone were measured using an Ubbelohde viscometer. The intrinsic viscosity was calculated from the ratio of these times using the Huggins equation, assuming a Huggins constant of 0.38.

[0081] The thickness of the laminated polyester film (base film) of the present invention is preferably 12 μm or more and 50 μm or less, more preferably 15 μm or more and 38 μm or less, and more preferably 19 μm or more and 33 μm or less. If the thickness of the film is 12 μm or more, there is no concern about deformation due to heat during film production, processing, or forming, which is preferred. On the other hand, if the thickness of the film is 50 μm or less, the amount of film discarded after use does not increase significantly, which is preferred in terms of reducing the environmental load.

[0082] The thickness of each layer is preferably 5.0 μm or more, more preferably 10 μm or more, for example, for the layer B on which the release layer can be laminated. When the thickness of the layer B is less than 5.0 μm, the smoothness of the layer B can be well maintained by being within this range.

[0083] In one embodiment, the static friction coefficient when the surface of the layer A and the surface of the layer B are in contact with each other, which are the front and back surfaces of the film before release processing, is preferably 0.30 or more and 0.60 or less.

[0084] By setting the static friction coefficient within the range of 0.30 to 0.60, film winding before release is improved, and roll misalignment caused by reduced friction between the release-treated surface and the surface of layer A after release can be suppressed. Specifically, by setting the static friction coefficient within the present invention's range, the following effects can be achieved: the pre-release winding characteristics of a large roll can be balanced with the post-release winding misalignment, resulting in stable transportability during ceramic sheet coating and the suppression of shape defects.

[0085] In one embodiment, the laminated polyester film of the present invention may have a laminate structure of three or more layers in addition to layer A and layer B. For example, the base film may have a laminate structure having layer A, layer C (intermediate layer), and layer B in this order.

[0086] In this method, Layer C, the intermediate layer, may contain particles. However, the particle size of Layer C must be selected so as not to impair the surface shape of Layer B. For example, if Layer C contains foreign matter exceeding 20 μm, it can cause large protrusions in Layers A and B, so such particles must be removed.

[0087] In this embodiment, particles having a particle size of 1 nm or more and less than 1.0 μm can be present in the surface layer B on which the release layer can be laminated. By making the surface layer B substantially free of particles having a particle size of 1.0 μm or more, such as inorganic particles, it is possible to reduce the risk of the particle shape in the substrate being transferred to the resin sheet and causing problems.

[0088] In one embodiment, by preventing the surface layer B from containing particles having a particle diameter of less than 1.0 μm, it is possible to more effectively suppress the transfer of the particle shape in the base film to the resin sheet and the generation of defects.

[0089] In one embodiment, the base film has a surface layer B substantially free of inorganic particles on at least one surface. This can further effectively prevent the particle shape in the base film from being transferred to the resin sheet and causing problems.

[0090] For example, the surface layer B that contains substantially no particles with a particle size of less than 1.0 μm preferably also contains substantially no particles with a particle size of 1.0 μm or more. The surface roughness SRa of the layer B surface is preferably 0.001 μm to 0.004 μm.

[0091] Here, in the present invention, "substantially free of particles" refers to, for example, inorganic particles smaller than 1.0 μm, a content of 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit when quantifying inorganic elements using fluorescent X-ray analysis. This is because even if particles are not actively added to the film, contaminants from foreign matter, raw resins, or dirt adhering to production lines and equipment during the film manufacturing process may break off and be incorporated into the film. Furthermore, "substantially free of particles larger than 1.0 μm" means that particles larger than 1.0 μm are not actively present.

[0092] The B layer on which the release layer can be laminated is preferably as smooth as possible. The B layer preferably has 5×10 2 Pieces / mm 2By setting the number of protrusions to this value, the required amount of release agent for forming the release layer can be evenly applied, including the protrusions, thereby utilizing the release agent's inherent release properties. Furthermore, by setting the number of protrusions on layer B to this range, protrusions on the surface of the release layer can be reduced, thereby preventing concave transfer to a resin sheet such as a ceramic sheet and suppressing shape defects on the ceramic sheet, etc., which may arise from these concave transfers.

[0093] Examples of the particles contained in the A layer, B layer, and intermediate layer of the substrate film include inorganic particles such as aggregated silica, monodispersed silica, spherical silica, calcium carbonate, kaolin, titanium oxide, and aluminum oxide, but are not limited thereto.

[0094] Furthermore, it is also possible to use recycled raw materials that have been subjected to release coating or green sheet coating. The recycling method includes: well-known material recycling and chemical recycling, and is not particularly limited.

[0095] Layer A contains particles having a particle size distribution with a D50 frequency of 13% or more. The D50 frequency is preferably 15% or more. On the other hand, the D50 frequency is preferably 40% or less, more preferably 30% or less.

[0096] In particles consisting of a particle size distribution with a D50 frequency of 13% or more, the value of (D90-D10) / D50 is preferably 0.40 or less, more preferably 0.25 or less, and further preferably 0.18 or less. The smaller (D90-D10) / D50 is, the sharper the particle size distribution, specifically, the frequency distribution, of the particles can be said to be. On the other hand, the value of (D90-D10) / D50 can be 0.05 or more, or 0.10 or more. Here, D90 refers to the particle size at which the cumulative frequency becomes 90% in the cumulative distribution based on the number of particles. D90 can also be called the 90% particle size. D10 refers to the particle size at which the cumulative frequency becomes 10% in the cumulative distribution based on the number of particles. D10 can also be called the 10% particle size.

[0097] The average particle size (D50) of the particles contained in layer A (i.e., particles composed of a particle size distribution with a D50 frequency of 13% or more) is preferably 0.6 μm to 1.5 μm, more preferably 0.6 μm to 1.3 μm, and even more preferably 0.6 μm to 1.0 μm. It should be noted that layer A may further contain particles other than particles composed of particles with a particle size distribution with a D50 frequency of 13% or more (hereinafter also referred to as second particles). However, layer A preferably does not contain second particles.

[0098] By having the above average particle size (D50), the present invention can suppress winding wrinkles and the occurrence of coarse protrusions. As a result, the present invention can achieve well-balanced suppression of pinholes, good winding / unwinding properties, and suppression of particle shedding.

[0099] The average particle size (D50) (μm) in the present invention is the value obtained by thoroughly dispersing the granular powder in an ethylene glycol slurry by high-speed stirring, measuring the particle size distribution in the resulting slurry, and recording the cumulative 50% value in the distribution (sometimes referred to as D50 in this application). The particle size distribution is measured using a light transmission centrifugal sedimentation particle size analyzer (manufactured by Shimadzu Corporation, trade name "SRA-CP3").

[0100] The amount of particles added to the A layer is preferably 4000 ppm or less, more preferably 3000 ppm or less, and even more preferably 2000 ppm or less.

[0101] The content of particles having an average particle size (D50) of 13% or more in layer A is preferably 4000 ppm or less, more preferably 3000 ppm or less, and even more preferably 2000 ppm or less.

[0102] In order to reduce the amount of particles added while ensuring friction before and after the demolding process, the particle size distribution width of the particles is made sharp. This allows the surface roughness to be optimized with a small amount of particles, and the target static friction coefficient can be achieved.

[0103] The particle size distribution width of particles comprising a particle size distribution with a D50 frequency of 13% or greater is preferably within the range of 0.6 μm to 1.5 μm. Here, "within the range of 0.6 μm to 1.5 μm" means that, in a histogram of the frequency distribution based on number, the D50 frequency of at least one particle size interval within the range of 0.6 μm to 1.5 μm is 13% or greater, the frequency of each particle size interval below 0.6 μm is 0.1% or less, and the frequency of each particle size interval exceeding 1.5 μm is 0.1% or less.

[0104] Regarding particles composed of a particle size distribution with a D50 frequency of 13% or more, the particle size distribution width of the particles is within the range of 0.6 μm to 1.5 μm, and the D50 frequency is preferably 13% to 40%, more preferably 15% to 30%.

[0105] The present invention is characterized by using particles having a particle size distribution with a D50 frequency of 13% or greater. Examples of such particles include silica particles. This can suppress coarse protrusions in layer A, for example, pinhole formation caused by coarse protrusions on the anti-release surface being transferred to the release surface. Furthermore, it can suppress forming defects caused by deterioration in planarity on the release surface.

[0106] Furthermore, the A layer tends to experience a high load on the particles when the base film is bent, such as during the winding process during film formation or during contact with a feed roller, making the particles more likely to fall off the film. However, the A layer of the present invention significantly reduces particle shedding by optimizing the static friction coefficient and limiting the particle size distribution.

[0107] The surface of the particles is preferably modified with commonly used agents such as polyacrylic acid and silane coupling agents. The heat-resistant temperature of the surface treatment agent, as measured by the 2% weight loss temperature, is preferably 250°C or higher, and more preferably 300°C or higher. By maintaining such a heat-resistant temperature, the surface treatment agent can be prevented from disappearing during the heat history of melt extrusion, resulting in good dispersibility and suppressed particle shedding.

[0108] The drying temperature of the pellets containing particles is preferably 130° C. or higher for 30 hours, more preferably 10 hours or less.

[0109] The melt extrusion temperature is preferably within +70°C, more preferably within +50°C, of the melting peak temperature when the resin is heated at 20°C / min using a differential scanning calorimeter (DSC).

[0110] The void size ratio of the unstretched film formed at a shear rate of 50 to 4000 (1 / sec) in the T-die in the melt extrusion step is 0, and voids are formed in the subsequent stretching step.

[0111] The film can be stretched in the longitudinal direction and then in the transverse direction simultaneously, or can be stretched sequentially. In the case of sequential stretching, the order of stretching can be arbitrary, but the longitudinal and transverse order is preferred for reasons such as equipment size.

[0112] The longitudinal stretching ratio is preferably 2.0 to 5.0 times, more preferably 3.0 to 3.8 times, and the transverse stretching ratio is preferably 3.5 to 5.0 times, more preferably 4.0 to 4.8 times.

[0113] In one embodiment, the stretching ratio in the longitudinal direction is lower than that in the transverse direction. Although the mechanism has not yet been elucidated, stretching under such conditions can stabilize the static friction coefficients of the front and back surfaces of the film.

[0114] The particles can be blended into the substrate film using a combination of known methods. For example, they can be added at any stage during polyester production, but are preferably added during the esterification stage or after the transesterification reaction and before the polycondensation reaction begins. Adding them as a slurry dispersed in ethylene glycol or the like can also accelerate the polycondensation reaction. More preferred methods include blending a slurry of particles dispersed in ethylene glycol or water with the polyester raw material using a vented kneading extruder, or blending dried particles with the polyester raw material using a kneading extruder.

[0115] Without being limited to a particular theory, the use of a kneading extruder with a vent allows the particles to be highly dispersed and the generation of coarse protrusions to be suppressed.

[0116] Alternatively, the number of surface protrusions can be further reduced by obtaining a polyester containing particles in advance and then kneading and extruding the pellets with pellets containing no particles (masterbatch method).

[0117] Furthermore, the base film may contain various additives within the range of the total light transmittance and the number of protrusions defined in the present invention. Examples of the additives include antistatic agents, UV absorbers, and stabilizers.

[0118] An antistatic layer or the like may be provided as needed on the surface opposite to the surface having the release layer, that is, on the surface of the layer A opposite to the release layer side.

[0119] (Release film)

[0120] The release film according to the embodiment of the present invention includes: a laminated polyester film; and a release layer provided on the surface of layer B of the laminated polyester film.

[0121] (Release layer)

[0122] The release layer is not particularly limited and may contain resins such as silicone-based, cyclic olefin-based, acyclic olefin-based, fluorine-based, alkyd-based, acrylic-based, melamine-based, and epoxy-based resins.

[0123] The silicone compound refers to a compound having a silicone structure in the molecule, and examples thereof include curable silicones, silicone graft resins, and modified silicone resins such as alkyl-modified silicones.

[0124] As the reactive curable silicone resin, those of an addition reaction system, those of a condensation reaction system, and those of an ultraviolet or electron beam curing system can be used.

[0125] Examples of addition reaction silicone resins include those obtained by curing polydimethylsiloxane containing vinyl groups introduced into the terminal or side chains with hydrogen siloxane using a platinum catalyst. In this case, a resin that cures within 30 seconds at 120°C is preferred, as it allows for processing at low temperatures.

[0126] As an example, we can cite: Dow Croning Toray Co., Ltd.'s low-temperature addition-curing type (LTC1006L, LTC1056L, LTC300B, LTC303E, LTC310, LTC314, LTC350G, LTC450A, LTC371G, LTC750A, LTC752, LTC755, LTC760A, LTC850, etc.) and thermal UV-curing type (LTC851, BY24-510, BY24-561, BY24-562, etc.); Shin-Etsu Chemical Co., Ltd.'s solvent addition type (KS-774, KS-882, X62-2825, etc.); solvent addition + UV-curing type (X62-5040, X62-5065, X62-5072T, KS5508, etc.); and Dual Cure curing type (X62-2835, X62-2834, X62-1980, etc.), etc.

[0127] Examples of the condensation reaction system silicone resin include those formed by condensing polydimethylsiloxane having an OH group at the terminal and polydimethylsiloxane having an H group at the terminal using an organotin catalyst to form a three-dimensional crosslinked structure.

[0128] Examples of UV-curable silicone resins include: those that utilize the same free radical reaction as conventional silicone rubber crosslinking; those that introduce unsaturated groups and undergo photocuring; those that decompose onium salts under ultraviolet light to generate strong acids, which are then used to cleave epoxy groups and crosslink; and those that crosslink via the addition reaction of thiols to vinyl siloxanes. Electron beams can also be used in place of ultraviolet light. Electron beams have greater energy than ultraviolet light, allowing free radical crosslinking reactions to occur even without the use of an initiator, as in UV curing.

[0129] Examples of the resin to be used include UV-curing silicones manufactured by Shin-Etsu Chemical Co., Ltd. (X62-7028A / B, X62-7052, X62-7205, X62-7622, X62-7629, X62-7660, etc.), UV-curing silicones manufactured by Momentive Performance Materials, Inc. (TPR6502, TPR6501, TPR6500, UV9300, UV9315, XS56-A2982, UV9430, etc.), and UV-curing silicones manufactured by Arakawa Chemical Industries, Ltd. (Silcolease UV POLY 200, POLY 215, POLY 201, KF-UV265AM, etc.).

[0130] As the UV-curable silicone resin, polydimethylsiloxane modified with acrylate or glycidoxy groups can also be used. These modified polydimethylsiloxanes can also be mixed with multifunctional acrylate resins, epoxy resins, etc. and used in the presence of an initiator.

[0131] Cyclic olefin resins contain cyclic olefins as polymerization components. Cyclic olefins are polymerizable cyclic olefins having an olefinic double bond in the ring, and can be classified into monocyclic olefins, bicyclic olefins, and polycyclic olefins having three or more rings.

[0132] Examples of the monocyclic olefin include cyclic C4-12 cycloolefins such as cyclobutene, cyclopentene, cycloheptene, and cyclooctene.

[0133] Examples of the bicyclic olefin include 2-norbornene; norbornenes having an alkyl group (C1-4 alkyl group), such as 5-methyl-2-norbornene, 5,5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, and 5-butyl-2-norbornene; norbornenes having an alkenyl group, such as 5-ethylidene-2-norbornene; norbornenes having an alkoxycarbonyl group, such as 5-methoxycarbonyl-2-norbornene and 5-methyl-5-methoxycarbonyl-2-norbornene; norbornenes having a cyano group, such as 5-cyano-2-norbornene; norbornenes having an aromatic group, such as 5-phenyl-2-norbornene and 5-phenyl-5-methyl-2-norbornene; octahydronaphthalene; and octahydronaphthalene having an alkyl group, such as 6-ethyloctahydronaphthalene.

[0134] Examples of the polycyclic olefin include dicyclopentadiene; derivatives such as 2,3-dihydrodicyclopentadiene, methyl octahydrofluorene, dimethyl octahydronaphthalene, dimethyl cyclopentadienyl naphthalene, and methyl octahydrocyclopentadienyl naphthalene; derivatives having substituents such as 6-ethyl-octahydronaphthalene; adducts of cyclopentadiene with tetrahydroindene, trimers and tetramers of cyclopentadiene, and the like.

[0135] Acyclic olefin resins contain acyclic olefins as polymerization components. Examples of acyclic olefins include ethylene, propylene, 1-butene, isobutylene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene.

[0136] Rubber can also be used as a resin for surface treatment, for example, copolymers of butadiene and isoprene.

[0137] Regardless of whether it is a cyclic olefin or a non-cyclic olefin, the olefin-based resin may be used alone or in combination of two or more.

[0138] Cyclic olefin resins and non-cyclic olefin resins may partially have hydroxyl modified or acid modified sites, and these functional groups may be cross-linked with a cross-linking agent. The cross-linking agent may be appropriately selected according to the modified group. Cross-linking agents include aromatic diisocyanates such as toluene diisocyanate, 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylenediisocyanate, polymethylene polyphenyl isocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, lower aliphatic diisocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate, and the hydrides of the aforementioned aromatic diisocyanates, and other isocyanate-based cross-linking agents. In addition, melamine-based cross-linking agents such as methyl etherified melamine resins and butyl etherified melamine resins, epoxy-based cross-linking agents, etc. may also be mentioned.

[0139] There are no particular restrictions on the fluorine-based compound as long as it is a compound having at least one of a perfluoroalkyl group and a perfluoroalkyl ether group. A portion of the fluorine-based compound may be modified with an acid, a hydroxyl group, an acrylate group, or the like. A cross-linking agent may be added to the modified portion for cross-linking. Alternatively, a compound having at least one of a perfluoroalkyl group and a perfluoroalkyl ether group may be added to a UV-curable resin and polymerized. Alternatively, a small amount of a compound having a non-reactive functional group and a perfluoroalkyl group may be added to a binder resin for use.

[0140] Release agents such as polyolefin-based release agents, long-chain alkyl-containing resin-based release agents, fluorine-based release agents, and silicone-based release agents can be used as main resins to form the release layer of a release film, or can be used as additives to a binder resin to form the release layer of a release film.

[0141] There are no particular limitations on the binder resin, and the following resins may be used, for example: UV-curable resins obtained by curing functional groups such as acryl, vinyl, and epoxy groups by UV irradiation; thermoplastic resins such as ester, carbamate, olefin, and acrylic resins; and thermosetting resins such as epoxy and melamine resins.

[0142] (resin sheet)

[0143] In particular, an object to be released can be laminated on the surface of the release layer. For example, a resin sheet can be mentioned as the object to be released.

[0144] In one embodiment, the release film of the present invention is not particularly limited as long as it is a resin sheet, and can also be used in the production of adhesives and optical films. In another embodiment, the release film is for forming a resin sheet and contains an inorganic compound. Examples of the inorganic compound include metal particles, metal oxides, and minerals, such as calcium carbonate, silica particles, aluminum particles, and barium titanate particles.

[0145] Examples of the resin include polyvinyl acetal resin and poly(meth)acrylate resin.

[0146] Even in the embodiment of the present invention having a highly smooth release layer and containing these inorganic compounds in the resin sheet, defects that may be caused by the inorganic compounds, such as breakage of the resin sheet and difficulty in peeling the resin sheet from the release layer, can be suppressed.

[0147] The resin component forming the resin sheet can be appropriately selected depending on the intended use.

[0148] In one embodiment, the resin sheet containing an inorganic compound is, for example, a ceramic green sheet or a dielectric coating sheet for a thin film capacitor. For example, the ceramic green sheet may contain barium titanate as the inorganic compound. In one embodiment, the resin sheet has a thickness of 0.2 μm to 1.0 μm.

[0149] Example

[0150] The present invention will be described based on the following examples, but the present invention is not limited thereto. The methods for measuring the characteristic values and evaluating the effects in the present invention are as follows.

[0151] (1) Surface roughness SRa

[0152] The surface morphology was measured using a high-precision micro-profile measuring instrument (three-dimensional surface roughness meter) using a stylus method in accordance with JIS-B0601 (1994) under the following conditions.

[0153] Measuring device: 3D micro-profile measuring instrument (Model ET4000A) manufactured by Kosaka Laboratory Co., Ltd.

[0154] Analysis equipment: Three-dimensional surface roughness analysis system (model TDA-31)

[0155] Stylus: Tip diameter 2μm, diamond

[0156] Needle pressure: 300μN

[0157] Measurement direction: Measure once in the film length direction and once in the film width direction and average the results.

[0158] X measuring length: 1250 μm

[0159] X conveying speed: 0.1mm / s (measurement speed)

[0160] Y measurement length: 300 μm

[0161] Y conveying pitch: 2μm (measurement interval)

[0162] Y line number: 151 (measurement number)

[0163] Z magnification: 20,000 times

[0164] Low range cutoff: 0.25mm (fluctuation cutoff value)

[0165] High range cutoff: R+Wmm (roughness cutoff value)

[0166] (R+W means no cutoff.)

[0167] Filter type: Gaussian space type

[0168] (2) Static friction coefficient

[0169] When the front and back surfaces of the film were stacked in contact, the static friction coefficient (μs) of the contacting surfaces was measured using a TENSILON universal testing machine (Shimadzu Corporation, AG-X plus) under the following conditions in accordance with JIS K-7125.

[0170] Load: 3.5kg

[0171] Test speed: 200mm / min

[0172] (3) Wrinkles of large rolls

[0173] Rolls with a length of at least 20,000 m and a width of at least 5 m (jumbo rolls) were slit into rolls with a length of 8,000 m and a width of 1,000 to 1,900 mm (sample rolls). The number of wrinkles on the surface of the sample (specifically, convex wrinkles formed by the incorporation of air) was counted, and the number of wrinkles per jumbo roll was calculated. The number of wrinkles per jumbo roll was evaluated using the following benchmark values. It should be noted that the length and width of the jumbo rolls were common to all examples.

[0174] 0: 0 to 10 or less

[0175] △: 11 to 20 or less

[0176] ×: 21 or more

[0177] (4) Winding misalignment after demolding

[0178] Rolls with a length of at least 20,000 m and a width of at least 5 m (large rolls) were slit into rolls with a length of 8,000 m and a width of 1,000 to 1,900 mm (sample rolls). The amount of winding misalignment during winding of these sample rolls after forming a release layer was evaluated. Winding misalignment refers to the misalignment in the width direction of the sample roll during winding. The excess length from the film end surface was measured with a ruler, and the excess length was used as the winding misalignment.

[0179] ○: No misalignment

[0180] △: within 3mm

[0181] ×: 4mm or more

[0182] (5) Pinhole evaluation

[0183] A solvent (toluene), ceramic raw material (BaTiO3, manufactured by Fuji-TITAN), binder, plasticizer, etc. were mixed to form a paste, and then dispersed in a ball mill to obtain a ceramic slurry. The ceramic slurry was applied to the surface of the release layer of the release film using a doctor blade method so that the thickness of the ceramic slurry was 1 μm when dried. The ceramic slurry was then dried in an oven at an ambient temperature of 100°C for 5 minutes to obtain a ceramic sheet. 2 Light was irradiated from the opposite side of the sheet within an area of , and the occurrence of pinholes was observed and evaluated based on the following criteria.

[0184] In addition, the mold release layer is laminated on layer B. The main component contained in the mold release layer is as described in Example 1 mentioned later.

[0185] ×: There are many pinholes.

[0186] △: There are almost no pinholes.

[0187] ○: No pinhole.

[0188] (6) Calculation method of average particle size (D50)

[0189] The silica powder was dispersed in water, and the average particle size (D50) was calculated using a light transmission type particle size distribution analyzer (SA-CP3 manufactured by Shimadzu Corporation).

[0190] (7) Determination of intrinsic viscosity

[0191] The film or polyester resin was pulverized and dried, then dissolved in a 60 / 40 (mass ratio) mixed solvent of phenol and tetrachloroethane. The solution was centrifuged to remove inorganic particles. The flow time of the solution at a concentration of 0.4 g / dl at 30°C and the flow time of the solvent alone were measured using an Ubbelohde viscometer. The intrinsic viscosity was calculated from the ratio of these times using the Huggins equation, assuming a Huggins constant of 0.38.

[0192] [Production Example of Polyester Resin a (Not Containing Particles)]

[0193] A continuous esterification reactor consisting of a three-stage complete mixing tank equipped with a stirrer, partial condenser, raw material inlet, and product outlet was used as the esterification reactor. TPA was fed continuously to the first esterification reactor of the esterification reactor at a rate of 2 tons / hour, EG was fed to 1 mol of TPA at a rate of 2 mol, and antimony trioxide was fed to an amount that would achieve 160 ppm of Sb atoms relative to the produced PET. The slurries were then reacted at 255°C under normal pressure for an average residence time of 4 hours.

[0194] Next, the reaction product in the first esterification reactor was continuously withdrawn from the system and supplied to the second esterification reactor. EG, distilled off from the first esterification reactor, was then supplied to the second esterification reactor at 8% by mass relative to the produced polymer (produced PET). Furthermore, an EG solution containing 65 ppm of magnesium atoms relative to the produced PET and an EG solution containing 20 ppm of TMPA relative to the produced PET were added, and the reaction was conducted at 260°C under normal pressure for an average residence time of 1.5 hours. Next, the reaction product in the second esterification reactor was continuously withdrawn from the system and supplied to the third esterification reactor, and an EG solution containing 20 ppm of TMPA relative to the produced PET were further added, and the reaction was conducted at 260°C under normal pressure for an average residence time of 0.5 hours. The esterification reaction product produced in the third esterification reactor was continuously supplied to a three-stage continuous polycondensation reactor for polycondensation. Furthermore, filtration was performed using a stainless steel sintered filter medium (nominal filtration accuracy, 90% cutoff for 5 μm particles) to obtain pellets of polyethylene terephthalate resin a (hereinafter also referred to as polyester resin a) containing substantially no particles.

[0195] [Production Example of Polyester Resin b (Containing Silica)]

[0196] Polyester resin a pellets were dissolved in extruder 1 (i.e., the first extruder) at 285°C. Powdered spherical silica particles (manufactured by Nippon Shokubai Co., Ltd.) with an average particle size (D50) of 1.0 μm were fed from the side feeder of extruder 1 to obtain polyester resin b pellets containing silica particles at a concentration of 5%. The average particle size (D50) was measured using a light transmission particle size distribution analyzer (SA-CP3 manufactured by Shimadzu Corporation).

[0197] [Production Example of Polyester Resin c (Containing Silica)]

[0198] Powder of spherical silica particles (manufactured by Nippon Shokubai Co., Ltd.) having an average particle size (D50) of 0.6 μm was added by the same method as for polyester resin b to obtain pellets of polyester resin c containing silica particles at a concentration of 5%.

[0199] [Production Example of Polyester Resin d (Containing Silica)]

[0200] Powder of spherical silica particles (manufactured by Nippon Shokubai Co., Ltd.) having an average particle size (D50) of 1.5 μm was added by the same method as for polyester resin b to obtain pellets of polyester resin d containing silica particles at a concentration of 5%.

[0201] [Production Example of Polyester Resin e (Containing Silica)]

[0202] Powder of spherical silica particles (manufactured by Nippon Shokubai Co., Ltd.) having an average particle size (D50) of 0.3 μm was added by the same method as for polyester resin b to obtain pellets of polyester resin e containing silica particles at a concentration of 5%.

[0203] [Production Example of Polyester Resin f (Containing Calcium Carbonate)]

[0204] The esterification reactor was heated to 200°C and a slurry containing 86.4 parts by mass of terephthalic acid and 64.4 parts by mass of ethylene glycol was added. While stirring the slurry, 0.03 parts by mass of antimony trioxide, 0.088 parts by mass of magnesium acetate tetrahydrate, and 0.16 parts by mass of triethylamine were added as catalysts. The temperature was then increased under pressure and the reaction mixture was heated to 3.5 kgf / cm2. 2 , 240 ° C, a pressurized esterification reaction is carried out. Afterwards, the esterification reaction kettle is returned to normal pressure and 0.040 parts by mass of trimethyl phosphate is added. Furthermore, the temperature is raised to 260 ° C, trimethyl phosphate is added, and after a predetermined time (for example, 15 minutes), calcium carbonate particles (made by Maruo Calcium Co., Ltd.) with an average particle size (D50) of 0.9 μm are added to ethylene glycol. The average particle size (D50) is a value measured using a light transmission type particle size distribution measuring device (made by Shimadzu Corporation, SA-CP3). Further, filtration is carried out using a viscose rayon filter with a 95% cutoff particle size of 30 μm, and an ethylene glycol slurry of calcium carbonate particles is added in a manner that becomes 20,000 ppm relative to the generated polyester. After a predetermined time (for example, 15 minutes), the obtained esterification reaction product is transferred to a polycondensation reactor and a polycondensation reaction is carried out under reduced pressure at 280 ° C. After the polycondensation reaction, the mixture was filtered through a 28 μm 95% cutoff filter (manufactured by Nippon Seisen Co., Ltd.) to obtain pellets of a polyester resin f having an intrinsic viscosity of 0.62 dl / g and containing calcium carbonate particles.

[0205] [Production Example of Polyester Resin g (Containing Silica)]

[0206] Silica particles (manufactured by FUJI SILYSIACHEMICAL LTD.) with an average particle size (D50) of 2.3 μm were added to ethylene glycol, and further filtered through a viscose rayon filter with a 95% cutoff particle size of 30 μm to obtain an ethylene glycol slurry of silica particles. Polyethylene terephthalate containing silica particles was obtained by the following method. The esterification reactor was heated, and when it reached 200°C, a slurry containing 86.4 parts by mass of terephthalic acid and 64.4 parts by mass of ethylene glycol was added, and 0.03 parts by mass of antimony trioxide, 0.088 parts by mass of magnesium acetate tetrahydrate, and 0.16 parts by mass of triethylamine as catalysts were added while stirring. Then, the pressure was increased and the temperature was raised to 3.5 kgf / cm 2 , 240 ° C, a pressurized esterification reaction was carried out. After that, the pressure in the esterification reactor was restored to normal pressure, and 0.040 parts by mass of trimethyl phosphate was added. Furthermore, the temperature was raised to 260 ° C, and after adding trimethyl phosphate for 15 minutes, the ethylene glycol slurry of the above-mentioned silica particles was added in such a way that it became 10000 ppm relative to the generated polyester. After 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reactor, and a polycondensation reaction was carried out under reduced pressure at 280 ° C. After the polycondensation reaction was completed, it was filtered through a 95% cut-off particle size of 28 μm naisol filter (manufactured by Nippon Seisen Co., Ltd.) to obtain a polyester resin g having an intrinsic viscosity of 0.63 dl / g and containing silica particles.

[0207] [Production Example of Polyester Resin h]

[0208] To a mixture of terephthalic acid purified from a petroleum-derived raw material and ethylene glycol purified from a plant-derived raw material, magnesium acetate tetrahydrate was added so that the polyester contained 70 ppm of magnesium atoms, and an esterification reaction was carried out at 255°C under normal pressure. Subsequently, antimony trioxide was added so that the polyester contained 280 ppm of Sb atoms and trimethyl phosphate was added so that the polyester contained 40 ppm of phosphorus atoms, and the reaction was further continued at 260°C.

[0209] The reaction product was then transferred to a polycondensation reaction vessel, where the reaction system was gradually depressurized while heating and polycondensation was carried out at 280°C under a reduced pressure of 133 Pa (1 mmHg) according to a conventional method to produce pellets having an intrinsic viscosity (IV) of 0.62. Subsequently, a powder of true spherical silica particles (manufactured by Nippon Shokubai Co., Ltd.) having an average particle size (D50) of 1.0 μm as measured using a light transmission particle size distribution analyzer (SA-CP3 manufactured by Shimadzu Corporation) was fed from the side feeder of extruder 1 to produce pellets of polyester resin h containing silica particles at a concentration of 5%.

[0210] The biomass content of the polyester resin h was measured according to ASTM D6866 and found to be 17%.

[0211] (Example 1)

[0212] (Manufacturing of polyester film)

[0213] First, to form layer A, polyester resin b containing silica particles having an average particle size (D50) of 1.0 μm was diluted with particle-free polyester resin a to achieve the particle concentrations listed in Table 1. The diluted resin was then dried under reduced pressure (3 Torr) at 180°C for 8 hours and then supplied to extruder 1 to be dissolved at 285°C.

[0214] Next, in order to form the layer B, the pellets of the polyester resin a were supplied to the extruder 2 (ie, the second extruder) and dissolved at 285°C.

[0215] Next, to form layer C (intermediate layer), a resin to which 55% of polyester resin a and 45% of self-recycled resin were added was supplied to extruder 3 (i.e., the third extruder) and dissolved at 285°C. The self-recycled resin refers to polyester resin pellets obtained by recycling the laminated film of Example 1 produced previously.

[0216] The polymer containing the three resins above was filtered separately using a stainless steel sintered filter medium (nominal filtration accuracy 10 μm, 95% particle cutoff). The polymer was then stacked in a three-layer confluence block and extruded from a nozzle into a sheet. The three-layer confluence block had a rectangular stacking section. The film was then wound onto a casting drum at a surface temperature of 30°C using an electrostatic casting method and cooled to solidify, forming an unstretched film.

[0217] The unstretched film was stretched to 3.3 times in the longitudinal direction at 85°C, then stretched 4.0 times in the width direction using a tenter, and heat treated at 230°C for 5 seconds to obtain a laminated film in which layer A, layer C, and layer B were laminated in this order. The laminated film had layer A containing silica particles and layer B containing substantially no particles on the front and back sides. The thickness of the laminated film was 25 μm. With respect to the thickness of the laminated film of 100%, the ratio of layer A was 16%, the ratio of layer B was 42%, and the ratio of layer C (intermediate layer) was 42%. In addition, the silica particle content in layer A was 1000 ppm.

[0218] Next, an ultraviolet cation-curing silicone resin (manufactured by Toshiba Silicon Co., Ltd., UV9315) was dispersed in a solvent (n-hexane) in such a manner that the resin solid content concentration became 2% by mass. Then, 1 part by mass of bis(alkylphenyl)iodonium hexafluoroantimonate was added to 100 parts by mass of the silicone resin as a curing catalyst. Thus, a coating liquid containing the silicone resin was prepared. The coating liquid containing the silicone resin was applied to the surface of the B layer of the laminated film using a wire rod. After drying at 100°C for 30 seconds, the film was irradiated with ultraviolet light (300mj / cm 2 ), a release film was obtained (the coating amount of the silicone release layer after drying was 0.10 g / m 2 ).

[0219] The evaluation results are shown in Tables 1 and 2.

[0220] (Example 2)

[0221] A release film was obtained in the same manner as in Example 1 except that the silica concentration in the layer A was changed to 4000 ppm.

[0222] (Example 3)

[0223] A release film was obtained in the same manner as in Example 1 except that the silica-containing polyester resin formulated in the A layer was changed to a polyester resin c containing silica having an average particle size (D50) of 0.6 μm.

[0224] (Example 4)

[0225] A release film was obtained in the same manner as in Example 1 except that the silica-containing polyester resin prepared in the A layer was changed to a silica-containing polyester resin d having an average particle size (D50) of 1.5 μm.

[0226] (Example 5)

[0227] In the particle-free layer B, the polyester resin containing silica was changed to a polyester resin e containing silica having an average particle size (D50) of 0.3 μm, and the formulation was changed so that the silica particle concentration in the layer B became 50 ppm. A release film was obtained in the same manner as in Example 1.

[0228] (Example 6)

[0229] A release film was obtained in the same manner as in Example 1 except that the thickness of the laminated film was changed to 31 μm.

[0230] (Example 7)

[0231] A release film was obtained in the same manner as in Example 1 except that the thickness of the laminated film was changed to 22 μm.

[0232] (Example 8)

[0233] A release film was obtained in the same manner as in Example 1 except that the polyester resin a used in the raw material formulation of the particle-containing layer A and layer C (intermediate layer) was replaced entirely with the polyester resin h. The biomass content of the release film was measured according to ASTM D6866 and found to be 9.5%.

[0234] (Comparative Example 1)

[0235] A release film was obtained in the same manner as in Example 1 except that the concentration of the silica particles prepared in the A layer was changed to 5000 ppm.

[0236] (Comparative Example 2)

[0237] A release film was obtained in the same manner as in Example 1 except that the polyester resin a formulated in the A layer was changed to a polyester resin e containing silica particles having an average particle size (D50) of 0.3 μm.

[0238] (Comparative Example 3)

[0239] A release film was obtained in the same manner as in Example 1 except that the polyester resin a formulated in the A layer was changed to a polyester resin f containing calcium carbonate particles having an average particle size (D50) of 0.9 μm and the particle concentration was changed to 5000 ppm.

[0240] (Comparative Example 4)

[0241] A release film was obtained in the same manner as in Example 1 except that the polyester resin a formulated in the A layer was changed to a polyester resin f containing calcium carbonate particles having an average particle size (D50) of 0.9 μm and the particle concentration was changed to 1000 ppm.

[0242] (Comparative Example 5)

[0243] A release film was obtained in the same manner as in Example 1 except that the polyester resin a formulated in the A layer was changed to the polyester resin g containing silica particles having an average particle size (D50) of 2.3 μm.

[0244] [Table 1]

[0245]

[0246] [Table 2]

[0247]

[0248] The intrinsic viscosity of each of the laminated films produced in Examples 1 to 8 was within the range of 0.50 dl / g to 0.65 dl / g.

[0249] In Comparative Example 1, the winding misalignment amount was 4 mm or more. In other words, excessive winding misalignment occurred. This is believed to be because the static friction coefficient (μs) was 0.27, that is, the static friction coefficient (μs) was too small.

[0250] In Comparative Example 1, pinholes, though few in number, were generated in the ceramic green sheet. This is considered to be because the particle content in the A layer was 5000 ppm, that is, the particle content in the A layer was too high.

[0251] In Comparative Example 2, more than 21 wrinkles were generated per jumbo roll. This is believed to be because the static friction coefficient (μs) was 0.76, i.e., the static friction coefficient (μs) was too high. As a result, the laminated film could not effectively slide around the air trapped between the laminated films, and thus the air trapped between the laminated films could not be effectively removed or dispersed.

[0252] In Comparative Example 4, more than 21 wrinkles occurred per jumbo roll. This is believed to be because the D50 frequency of the particles in layer A was 12%, meaning that the particle size distribution of the particles in layer A was not sharply defined. This resulted in the formation of large protrusions in layer A, which facilitated the trapping of air between the laminated films. Furthermore, it is believed that the static friction coefficient (μs) was 0.4, preventing the complete removal or dispersion of air trapped between the laminated films.

[0253] In Comparative Example 3, winding misalignment occurred although the amount of winding misalignment was within 3 mm. This is considered to be because the static friction coefficient (μs) was 0.27, that is, the static friction coefficient (μs) was too small.

[0254] In Comparative Example 3, pinholes were present in the ceramic green sheet, although they were few in number. This is considered to be because the particle content in the A layer was 5000 ppm, that is, the particle content in the A layer was too high.

[0255] In Comparative Example 3, although the D50 frequency of the particles in layer A was 12% (i.e., the particle size distribution of the particles in layer A was not sharp), wrinkles were present. This is believed to be because the static friction coefficient (μs) was 0.27, allowing the laminated film to easily slide around the air trapped between the laminated films, thus completely escaping or dispersing the air trapped between the laminated films.

[0256] In Comparative Example 5, a large number of pinholes were generated in the ceramic green sheet. This is considered to be because the surface roughness SRa of the B layer was 0.04 μm or less, that is, the surface roughness SRa of the B layer was too large.

[0257] In Comparative Example 5, more than 21 wrinkles were observed per jumbo roll. This is believed to be due to the excessively high D50 of the particles in layer A, with a D50 frequency of 7.7% (i.e., the particle size distribution of the particles in layer A was not sharply defined). This resulted in the formation of large protrusions in layer A, which facilitated the trapping of air between the laminated films. Furthermore, the static friction coefficient (μs) of 0.38 presumably prevented the complete removal or dispersion of air trapped between the laminated films.

[0258] On the other hand, Examples 1 to 7 had few or no wrinkles per jumbo roll (specifically, 0 to 10 wrinkles), no winding misalignment, and no pinholes in the ceramic green sheets.

[0259] Industrial applicability

[0260] The present invention provides a laminated polyester film that ensures the winding properties of a large roll before the demolding process and can suppress the winding displacement after the demolding process.

Claims

1. A laminated polyester film for a release film for forming a resin sheet, characterized in that It is a laminated polyester film having an A layer and a B layer on the front and back sides, Layer A contains particles having a particle size distribution in which the frequency of the average particle diameter (D50) is 13% or more. The B layer has a surface for setting a release layer. The static friction coefficient (μs) when the surface of the B layer and the surface of the A layer are in contact with each other is 0.3 or more and 0.6 or less.

2. The laminated polyester film according to claim 1, wherein The intrinsic viscosity is 0.50 dl / g or more and 0.65 dl / g or less.

3. The laminated polyester film according to claim 1, wherein The particles in the A layer are silica particles, and the average particle size (D50) of the silica particles is 0.6 μm or more and 1.5 μm or less. The laminated polyester film according to claim 1 , which has a thickness of 12 μm to 50 μm.

5. The laminated polyester film according to claim 1, wherein At least one of the A layer and the B layer contains at least ethylene glycol and terephthalic acid as constituent components. At least one of the ethylene glycol and the terephthalic acid is derived from a biomass resource.

6. The laminated polyester film according to claim 1, wherein The surface roughness SRa of the B layer is 0.004 μm or less.

7. The laminated polyester film according to claim 1, wherein The B layer contains substantially no particles.

8. A release film for forming a resin sheet, comprising: The laminated polyester film according to claim 1; and A release layer provided on the surface of layer B of a laminated polyester film.

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