Release film, release film roll, and adhesive body

Abstract

To provide a release film having both excellent releasability and blocking resistance.SOLUTION: The release film includes a polyester film substrate and a release layer on a first surface side of the polyester film substrate. The release layer is formed of a release agent composition containing a curable silicone resin, a three-membered ring cyclic ether compound, and a four-membered ring cyclic ether compound. The content of the four-membered ring cyclic ether compound contained in the release agent composition is 0.5-20 mass% based on 100 mass% of the solid content. The arithmetic mean height (Sa) of a second surface of the polyester film substrate is 40-100 nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a release film, a release film roll, and an adhesive body. [Background technology]

[0002] Release films, which have a release layer on at least one side of a base film, are used in a variety of fields, including industrial materials, optical materials, electronic component materials, and battery packaging. Polyethylene terephthalate (PET), a typical polyester film, is widely used as the base film for release films because of its excellent transparency, mechanical strength, heat resistance, flexibility, and other properties.

[0003] Release films are widely used to protect adhesive or bonded surfaces. Silicone-based release agents containing siloxane units are commonly used as the material that constitutes the release surface of release films. When producing release films, a release layer is formed by applying a release agent composition containing a silicone-based release agent onto a polyester film substrate.

[0004] For example, Patent Document 1 discloses a release film in which a release agent composition containing a curable silicone resin, a crosslinking agent, a platinum catalyst, and a solvent is applied to a polyester film substrate and then dried to form a release layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2022-139376 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, in the conventional technology, a release agent composition containing a curable silicone resin and a solvent is applied to a polyester film substrate and then dried. However, a solvent-based release agent composition requires a drying process to volatilize the solvent after application, which places a high burden on the environment in terms of energy. In addition, there is a concern that the working environment may be deteriorated due to the volatilization of the solvent in the drying process. For this reason, there is a demand for the establishment of a technology for forming a release layer from a solventless release agent composition.

[0007] The present inventors have investigated a technique for forming a release layer from a solvent-free release agent composition, and have found that when a solvent is not used, the components that can be used as a release component, such as a curable silicone resin, are limited, which can lead to poor coating properties and insufficient curing of the release layer. If the coating properties are poor or the curing properties of the release layer are insufficient, the release layer may be damaged when the release film is stored as a film roll. In such cases, the release properties are not fully exhibited, which is problematic. Furthermore, if the curing properties of the release layer are insufficient, blocking may occur when the release film is wound into a film roll, which is problematic.

[0008] Therefore, in order to solve such problems of the conventional technology, the present inventors have carried out investigations with the aim of providing a release film that has both excellent releasability and blocking resistance. [Means for solving the problem]

[0009] Examples of specific embodiments of the present invention are given below.

[0010] [1] A polyester film substrate; a release layer on the first surface side of the polyester film substrate; the release layer is a layer formed from a release agent composition containing a curable silicone resin, a three-membered ring cyclic ether compound, and a four-membered ring cyclic ether compound; the content of the four-membered ring cyclic ether compound contained in the release agent composition is 0.5 to 20% by mass relative to 100% by mass of the solid content, A release film, wherein the arithmetic mean height (Sa) of the second surface of the polyester film substrate is 40 to 100 nm. [2] The release film according to [1], wherein the maximum height (Sz) of the second surface of the polyester film substrate is 2000 to 10000 nm. [3] The release film according to [1] or [2], wherein the polyester film substrate has a polyester layer on the second surface side thereof containing 0.1 to 2.0 mass % of particles having an average particle size of 1 to 8 μm. [4] The release film according to any one of [1] to [3], wherein the content of the three-membered ring cyclic ether compound contained in the release agent composition is 10 to 70 mass % relative to 100 mass % of the solid content. [5] The release film according to any one of [1] to [4], wherein the release agent composition further contains a photopolymerization initiator. [6] The release film according to any one of [1] to [5], wherein the thickness of the release layer is 150 to 2000 nm. [7] A release film roll obtained by winding up the release film according to any one of [1] to [6]. [8] An adhesive body having an adhesive layer on the release layer of the release film according to any one of [1] to [6]. [Effects of the Invention]

[0011] According to the present invention, a release film having both excellent releasability and blocking resistance can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below. The following description may be based on representative embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, when "X to Y" (X and Y are arbitrary numbers) is used, it means "X or more and Y or less" unless otherwise specified, and also includes "preferably greater than X" or "preferably less than Y." Furthermore, when "X or more" (X is an arbitrary number) or "Y or less" (Y is an arbitrary number), it also includes the meaning "preferably greater than X" or "preferably less than Y." In the following description, the terms "film" and "sheet" are not clearly distinguished from each other, and the term "film" includes the term "sheet," and the term "sheet" includes the term "film."

[0013] (Release film) This embodiment relates to a release film (hereinafter also referred to as "this release film") that includes a polyester film substrate and a release layer on the first surface side of the polyester film substrate, wherein the release layer is formed from a release agent composition containing a curable silicone resin, a three-membered cyclic ether compound, and a four-membered cyclic ether compound, the content of the four-membered cyclic ether compound in the release agent composition being 0.5 to 20 mass% relative to 100 mass% of the solid content, and the arithmetic mean height (Sa) of the second surface of the polyester film substrate is 40 to 100 nm.

[0014] In this embodiment, the release layer is formed from a release agent composition containing specific amounts of a curable silicone resin, a three-membered cyclic ether compound, and a four-membered cyclic ether compound. Furthermore, by setting the arithmetic mean height (Sa) of the second surface of the polyester film substrate within the above range, excellent releasability and blocking resistance can be achieved. In this embodiment, by incorporating a three-membered cyclic ether compound and a four-membered cyclic ether compound into the release layer, the coatability of the release agent composition can be improved, resulting in the formation of a release layer without coating defects. Furthermore, by incorporating a three-membered cyclic ether compound and a four-membered cyclic ether compound into the release layer, the curability of the release layer can be enhanced, resulting in excellent blocking resistance. Generally, increasing the curability of a release layer improves blocking resistance, but on the other hand, there is a tendency for the release layer to deteriorate. In this regard, this embodiment successfully achieves both excellent releasability and blocking resistance by forming the release layer from a release agent composition containing specific amounts of a curable silicone resin, a three-membered cyclic ether compound, and a four-membered cyclic ether compound.

[0015] In this specification, the "first surface of the polyester film substrate" refers to the surface of the polyester film substrate on which a release layer is provided. Meanwhile, the "second surface of the polyester film substrate" refers to the surface of the polyester film substrate on which no release layer is provided. When the release film is wound into a roll, the "second surface of the polyester film substrate" is wound up in a state where it is laminated with a release layer. By setting the arithmetic mean height (Sa) of this surface to the above-mentioned lower limit or higher, adhesion between the release layer of the first release film and the polyester film substrate of the second release film can be suppressed when the release films are laminated together (for example, when the first release film and the second release film are laminated together), thereby improving blocking resistance. Furthermore, by setting the arithmetic mean height (Sa) of the second surface of the polyester film substrate to the above-mentioned upper limit or lower, when the release films are laminated together, the uneven structure can be transferred to the release layer, preventing the smoothness of the release layer from being impaired. Normally, to improve blocking resistance, it is considered preferable to have a smaller arithmetic mean height of the substrate film surface in contact with the release layer, as this reduces adhesion. However, in the present invention, it has been unexpectedly discovered that, in relation to the release layer specific to this application, blocking resistance can be improved by setting the arithmetic mean height (Sa) of the substrate film surface in contact with the release layer to a specific range that is larger than the generally preferred range.

[0016] In the present release film, the arithmetic mean height (Sa) of the second surface of the polyester film substrate is 40 nm or more, more preferably 50 nm or more, even more preferably 60 nm or more, even more preferably 65 nm or more, and particularly preferably 70 nm or more. The arithmetic mean height (Sa) of the second surface of the polyester film substrate is 500 nm or less, more preferably 400 nm or less, even more preferably 300 nm or less, even more preferably 250 nm or less, even more preferably 200 nm or less, even more preferably 150 nm or less, and particularly preferably 100 nm or less. By setting the arithmetic mean height (Sa) of the second surface of the polyester film substrate within the above range, the blocking resistance of the release film can be more effectively improved, and the ease of unwinding can be improved. Furthermore, by setting the arithmetic mean height (Sa) of the second surface of the polyester film substrate to the above upper limit or less, it is possible to prevent the transfer of unevenness to the surface of the release layer when the release film is laminated.

[0017] In the present release film, the maximum height (Sz) of the second side of the polyester film substrate is preferably 2000 nm or more, more preferably 3000 nm or more, and even more preferably 4000 nm or more. Furthermore, the maximum height (Sz) of the second side of the polyester film substrate is preferably 10000 nm or less, more preferably 9000 nm or less, and even more preferably 8000 nm or less. By setting the maximum height (Sz) of the second side of the polyester film substrate within the above range, the blocking resistance of the release film can be more effectively improved, the ease of unwinding can be improved, and when the release film is laminated, the transfer of the uneven shape of the substrate film surface to the release layer surface can be suppressed.

[0018] The arithmetic mean height (Sa) and maximum height (Sz) of the second surface of the polyester film substrate are measured using a surface profile measurement system in accordance with ISO 25178. The measurement is performed at a magnification of 5x, using optical interferometry to measure the second surface of the polyester film substrate, which does not have a release layer of a release film laminated thereon. Then, correction and baseline correction are performed under the following conditions, and the data is read. Compensation: Full Baseline correction: Surface correction (4th order polynomial approximation)

[0019] The arithmetic mean height (Sa) of the first surface of the polyester film substrate is preferably 3 nm or more, more preferably 5 nm or more, even more preferably 8 nm or more, even more preferably 10 nm or more, and particularly preferably 15 nm or more. The arithmetic mean height (Sa) of the first surface of the polyester film substrate is preferably 100 nm or less, more preferably 90 nm or less, even more preferably 80 nm or less, even more preferably 50 nm or less, and particularly preferably 30 nm or less.

[0020] The maximum height (Sz) of the first surface of the polyester film substrate is preferably 5000 nm or less, more preferably 4000 nm or less, and even more preferably 3000 nm or less. In this embodiment, by setting the arithmetic mean height (Sa) and maximum height (Sz) of the first surface of the polyester film substrate within the above ranges, the smoothness of the laminated release layer can be increased, and the releasability can be more effectively improved. Furthermore, by setting the arithmetic mean height (Sa) and maximum height (Sz) of the first surface of the polyester film substrate within the above ranges, it is possible to prevent the unevenness originating from the surface of the substrate film of the release film from being transferred to the surface of the adhesive layer when the release film is attached to a highly smooth adhesive layer.

[0021] In the present release film, another layer may be interposed between the polyester film substrate and the release layer, or the two may be directly laminated without any other layer interposed therebetween.

[0022] <Polyester film substrate> The polyester film of the polyester film substrate may be a single-layer structure or a laminated structure of two or more layers. When the polyester film has a laminated structure, it may be a two-layer structure, a three-layer structure, or a four-layer structure or more. In this case, the constituent materials of each layer may be the same or different. For example, by changing the materials of the surface layer and the intermediate layer, it is possible to form a two-type three-layer structure (A / B / A) or a three-type three-layer structure (A / B / C). In this embodiment, the polyester film substrate is preferably a polyester film having a multilayer structure of two or more layers, more preferably a polyester film having a three-layer structure, and particularly preferably a polyester film having a three-type three-layer structure (A / B / C).

[0023] A release layer is disposed on the first surface of the polyester film substrate, and the arithmetic mean height (Sa) of the surface not provided with the release layer (the second surface of the polyester film substrate) is 40 nm or more, more preferably 50 nm or more, even more preferably 60 nm or more, even more preferably 65 nm or more, and particularly preferably 70 nm or more. The arithmetic mean height (Sa) of the second surface of the polyester film substrate is 500 nm or less, more preferably 400 nm or less, even more preferably 300 nm or less, even more preferably 250 nm or less, even more preferably 200 nm or less, even more preferably 150 nm or less, and particularly preferably 100 nm or less.

[0024] The maximum height (Sz) of the second surface of the polyester film substrate is preferably 2000 nm or more, more preferably 3000 nm or more, and even more preferably 4000 nm or more, and is preferably 10000 nm or less, more preferably 9000 nm or less, and even more preferably 8000 nm or less.

[0025] The arithmetic mean height (Sa) of the first surface of the polyester film substrate is preferably 3 nm or more, more preferably 5 nm or more, even more preferably 8 nm or more, even more preferably 10 nm or more, and particularly preferably 15 nm or more. The arithmetic mean height (Sa) of the first surface of the polyester film substrate is preferably 100 nm or less, more preferably 90 nm or less, even more preferably 80 nm or less, even more preferably 50 nm or less, and particularly preferably 30 nm or less.

[0026] The maximum height (Sz) of the first surface of the polyester film substrate is preferably 5000 nm or less, more preferably 4000 nm or less, and even more preferably 3000 nm or less. In this embodiment, by setting the arithmetic mean height (Sa) and maximum height (Sz) of the first surface of the polyester film substrate within the above ranges, the smoothness of the release layer can be increased, and the releasability can be more effectively improved. Furthermore, by setting the arithmetic mean height (Sa) and maximum height (Sz) of the first surface of the polyester film substrate within the above ranges, it is possible to prevent the unevenness originating from the surface of the substrate film of the release film from being transferred to the surface of the adhesive layer when the release film is attached to a highly smooth adhesive layer.

[0027] The surface roughness of each side of the polyester film substrate can be controlled within the above range by adjusting the type and particle size of the particles added, as described below. For example, if the polyester film is laminated, the smoothness of the first side can be increased by adding particles with a small particle size, reducing the amount of particles added, or not adding any particles at all to the layer on the first side. On the other hand, a surface with a certain degree of roughness can be formed by adding particles with a large particle size or increasing the amount of particles added to the layer on the second side.

[0028] The surface roughness of each side of the polyester film substrate can be controlled by subjecting the polyester film to various surface treatments. For example, the second side may be subjected to a friction treatment or a textured finish to impart a predetermined roughness.

[0029] The polyester film may be a non-stretched film (sheet) or a stretched film, but is preferably a stretched film, and more preferably a biaxially stretched film.

[0030] A polyester film contains polyester as a main component resin. In this specification, the term "main component resin" refers to the resin that has the largest mass proportion among the resins constituting the polyester film, and is a resin that accounts for 50 mass % or more, 75 mass % or more, 90 mass % or more, or 100 mass % of the resins constituting the polyester film.

[0031] The polyester may be a homopolyester or a copolymer polyester. In the case of a homopolyester, it is preferably one obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of aromatic dicarboxylic acids include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of aliphatic glycols include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. A typical example of a polyester is polyethylene terephthalate.

[0032] Examples of copolymer polyesters include those obtained by polycondensation of a dicarboxylic acid component and a glycol component. Examples of dicarboxylic acid components include one or more of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acids (e.g., p-oxybenzoic acid). Examples of glycol components include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexanedimethanol, and neopentyl glycol. The copolymer polyester may contain a third component in addition to the dicarboxylic acid component and the glycol component, but the content of the third component is preferably 30 mol% or less based on the total of the carboxylic acid component and the glycol component.

[0033] The intrinsic viscosity (IV) of the polyester is preferably 0.5 dL / g or more, more preferably 0.52 dL / g or more, and even more preferably 0.54 dL / g or more. The intrinsic viscosity (IV) of the polyester is, for example, preferably 1 dL / g or less, more preferably 0.8 dL / g or less. By controlling the intrinsic viscosity of the polyester within the above range, the production efficiency of the polyester film can be more effectively improved.

[0034] The polyester polymerization catalyst is not particularly limited, and a conventionally known compound can be used, for example, an antimony compound, a titanium compound, a germanium compound, a manganese compound, an aluminum compound, a magnesium compound, a calcium compound, etc. Among these, an antimony compound has the advantage of being inexpensive and having high catalytic activity.

[0035] In order to suppress the amount of precipitation of oligomer components, the polyester film may be produced using a polyester having a low content of oligomer components as the raw material. As a method for producing a polyester having a low content of oligomer components, various known methods can be used, such as a method in which solid-state polymerization is carried out after the polyester is produced.

[0036] The amount of oligomer component precipitation may be suppressed by forming the polyester film into a three-layer or more layer structure and using a polyester raw material with a low oligomer component content as the outermost layer of the polyester film. The polyester may also be obtained by esterification or transesterification, followed by melt polycondensation under reduced pressure at a higher reaction temperature.

[0037] The polyester film may contain a biomass-derived polyester. For example, when the polyester film has a multi-layer structure, it may have a layer containing a biomass-derived polyester as a main component and a layer containing a fossil fuel-derived polyester as a main component.

[0038] The polyester film may also contain recycled materials, such as edges of polyester films that were not used in the polyester film production line, recycled polyesters derived from PET bottles, and recycled polyesters derived from packaging materials.

[0039] The polyester film may contain an ultraviolet absorber to improve the weather resistance of the film and prevent deterioration of the adherend (e.g., liquid crystal), etc. The ultraviolet absorber is a compound that absorbs ultraviolet light and is not particularly limited as long as it can withstand the heat applied during the polyester film production process.

[0040] The ultraviolet absorber includes organic ultraviolet absorbers and inorganic ultraviolet absorbers, and organic ultraviolet absorbers are preferred from the viewpoint of transparency.The organic ultraviolet absorbers are not particularly limited, but examples thereof include cyclic iminoesters, benzotriazoles, and benzophenones.From the viewpoint of durability, cyclic iminoesters and benzotriazoles are more preferred.In addition, two or more types of ultraviolet absorbers can be used in combination.

[0041] Particles can also be blended into polyester films for the primary purposes of imparting lubricity and preventing scratches during each process. When particles are blended, the type of particles to be blended is not particularly limited as long as they are capable of imparting lubricity. Specific examples include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenolic resin, epoxy resin, and benzoguanamine resin. Furthermore, precipitated particles obtained by precipitating and finely dispersing a portion of a metal compound such as a catalyst during the polyester production process can also be used.

[0042] The shape of the particles to be used is not particularly limited, and may be, for example, spherical, blocky, rod-like, flat, etc. Furthermore, there are no particular limitations on the hardness, specific gravity, color, etc. of the particles.

[0043] Two or more types of these particles may be used in combination as needed. For example, when the polyester film has a two-type three-layer structure, the types of particles contained in the surface layer and the intermediate layer may be different. Furthermore, when the polyester film has a two-layer structure or a three-type three-layer structure, the types of particles contained in the first surface layer and the second surface layer may be different.

[0044] When the polyester film has a laminated structure of three or more layers, it is also preferable to contain particles only in the surface layer. In this embodiment, from the viewpoint of providing easy slippage, it is preferable that at least one surface layer contains particles, and further from the viewpoint of improving releasability and blocking resistance, it is more preferable that particles are contained in both the surface layer (first surface layer) arranged on the side where the release layer is provided and the surface layer (second surface layer) arranged on the side where the release layer is not provided. For example, the average particle size of the particles incorporated into the first surface layer is preferably 5 μm or less, more preferably 4.5 μm or less, even more preferably 4 μm or less, even more preferably 3.5 μm or less, and particularly preferably 3 μm or less. Furthermore, the average particle size of the particles incorporated into the first surface layer is preferably 0.1 μm or more. By setting the average particle size of the particles incorporated into the first surface layer within the above range, it is possible to impart an appropriate surface roughness to the film, ensuring good slipperiness and smoothness.

[0045] On the other hand, the average particle size of the particles incorporated into the second surface layer is preferably 1 μm or more, more preferably 2 μm or more, even more preferably 2.5 μm or more, and particularly preferably 3 μm or more. Furthermore, the average particle size of the particles incorporated into the second surface layer is preferably 8 μm or less, more preferably 7 μm or less, and even more preferably 5 μm or less. By setting the average particle size of the particles incorporated into the second surface layer within the above range, it becomes easier to adjust the arithmetic mean height (Sa) and maximum height (Sz) of the surface of the polyester film substrate on the side where the release layer is not provided to within the desired range.

[0046] In this embodiment, different types of particles may be blended in the first surface layer and the second surface layer. In this embodiment, it is preferable to blend organic particles in the second surface layer because they have good compatibility with polyester resin and good dispersibility in polyester resin even when the particle content is increased. For example, inorganic particles may be blended in the first surface layer, and organic particles may be blended in the second surface layer.

[0047] The average particle size of particles can be determined by measuring the diameters of 10 or more particles using a scanning electron microscope (SEM) and taking the average value. In this case, for non-spherical particles, the average value of the longest and shortest diameters can be measured as the diameter of each particle.

[0048] The particle content in the polyester film substrate is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less, relative to the total mass of the polyester film substrate, and is preferably 0.0003% by mass or more, more preferably 0.001% by mass or more, and even more preferably 0.01% by mass or more.

[0049] When the polyester film has a two-layer or three-layer structure, the particle content of the second surface layer is preferably 0.03% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.3% by mass or more, and even more preferably 0.4% by mass or more, based on the total mass of the surface layer. The particle content in the second surface layer is preferably 2% by mass or less, more preferably 1.5% by mass or less, and even more preferably 1.0% by mass or less. The particle content of the first surface layer is preferably lower than that of the second surface layer, and is preferably 0.8% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.2% by mass or less, based on the total mass of the surface layer. The particle content of the first surface layer is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.02% by mass or more.

[0050] In order to obtain a polyester film substrate having the above-mentioned arithmetic mean height (Sa) in the present release film, for example, the particle content in the polyester film substrate can be increased to 0.03 mass % or more, for example, 0.03 mass % to 2 mass %, and when the polyester film substrate has a multi-layer structure of two or more layers, it is preferable that the second outer polyester layer contains 0.1 mass % to 2 mass %, more preferably 0.3 mass % to 1.5 mass %, and particularly preferably 0.4 mass % to 1.0 mass % of particles having an average particle size of 1 μm to 8 μm, more preferably 2 μm to 7 μm, and particularly preferably 2.5 μm to 5 μm.

[0051] The method of adding particles to the polyester film substrate is not particularly limited, and any conventionally known method can be used. For example, the particles can be added at any stage of producing the polyester constituting each layer, but it is preferable to add them after the completion of the esterification or transesterification reaction. Alternatively, the particles can be melt-kneaded into the polyester using an extruder or the like.

[0052] In addition to the above-mentioned particles, conventionally known antioxidants, heat stabilizers, lubricants, dyes, pigments, etc. may be added to the polyester film substrate as needed.

[0053] The thickness of the polyester film substrate is not particularly limited as long as it is within a range that allows it to be formed into a film, but from the viewpoints of mechanical strength, handling properties, productivity, etc., it is preferably in the range of 5 to 300 μm, more preferably 10 to 125 μm.

[0054] <Method of manufacturing polyester film substrate> Next, a specific example of the production of a polyester film substrate will be described, but the invention is not limited to the following production example.

[0055] The method for producing a polyester film substrate preferably includes a step of extruding dried polyester raw material pellets from a die using an extruder to form a molten sheet, and then cooling and solidifying the sheet with a cooling roll to obtain an unstretched sheet. In this case, it is preferable to increase the adhesion between the sheet and a rotating cooling drum to improve the flatness of the sheet, and an electrostatic application adhesion method and / or a liquid application adhesion method are preferably used. Particles, UV absorbers, and other additives may be appropriately blended into the pellets.

[0056] Next, the resulting unstretched sheet is stretched in one direction using a roll or tenter-type stretching machine. The stretching temperature is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.5 to 7 times, preferably 3 to 6 times. Next, the sheet is stretched in a direction perpendicular to the first-stage stretching direction, usually at 70 to 170°C, and at a stretching ratio of usually 2.5 to 7 times, preferably 3 to 6 times. Subsequently, the sheet is heat-treated at a temperature of 180 to 270°C under tension or relaxation of 30% or less to obtain a biaxially oriented film. The above stretching can also be performed in one direction in two or more stages. In this case, it is preferable to perform the stretching so that the final stretching ratios in both directions are each within the above range.

[0057] A simultaneous biaxial stretching method can also be used to produce polyester films. In this method, an unstretched sheet is simultaneously stretched and oriented in both the machine direction and the width direction under temperature control, typically at 70 to 120°C, and preferably at 80 to 110°C. The area stretch ratio is typically 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times. Subsequently, the sheet is heat-treated at a temperature of 170 to 270°C under tension or relaxation of 30% or less to obtain a stretched and oriented film. Regarding the simultaneous biaxial stretching apparatus used in the above-described stretching method, any conventionally known stretching method, such as a screw method, a pantograph method, or a linear drive method, can be used.

[0058] In this embodiment, an intermediate layer may be provided between the polyester film substrate and the release layer, and the intermediate layer may be, for example, a functional layer such as a resin layer. When forming such an intermediate layer, a so-called coating-stretching method (in-line coating) can be used, in which a composition for forming an intermediate layer is applied during the stretching process of the polyester film. When the intermediate layer is provided on the polyester film by the coating-stretching method, the intermediate layer is formed during the manufacturing process of the polyester film substrate, thereby improving production efficiency. Furthermore, coating can be performed simultaneously with stretching, and the thickness of the resin layer can be reduced depending on the stretching ratio.

[0059] The "polyester film" constituting the present release film does not only mean a film formed in advance, but also means a polyester layer constituting the release film. In other words, the "polyester film" is synonymous with the "polyester layer." Therefore, the present release film can be formed not only by laminating a release layer on the surface of a polyester film, but also by co-extrusion molding a polyester layer and a release layer.

[0060] <Release layer> The release layer of the present release film is a layer formed by curing a release agent composition (referred to as "the present release agent composition") containing a curable silicone resin, a three-membered ring cyclic ether compound, and a four-membered ring cyclic ether compound, and is disposed on one side of the above-mentioned polyester film substrate. It can also be said that the release layer is a release layer containing a cured product formed by curing the present release agent composition.

[0061] The thickness of the release layer (thickness after curing) is preferably 100 nm or more, more preferably 150 nm or more, even more preferably 200 nm or more, and particularly preferably 300 nm or more. The thickness of the release layer is preferably 2000 nm or less, more preferably 1500 nm or less, and even more preferably 1200 nm or less. By making the thickness of the release layer equal to or greater than the above-mentioned lower limit, the releasability of the release film can be more effectively improved. By making the thickness of the release layer equal to or less than the above-mentioned upper limit, the blocking resistance of the release film can be more effectively improved.

[0062] <Release Agent Composition> The release agent composition contains a curable silicone resin, a three-membered cyclic ether compound, and a four-membered cyclic ether compound. In this embodiment, by using a curable silicone resin, a three-membered cyclic ether compound, and a four-membered cyclic ether compound in combination, even when a solvent-free release agent composition is formed, the coatability of the release agent composition can be improved, and a release layer with excellent release properties can be formed. Furthermore, in this embodiment, by using a three-membered cyclic ether compound and a four-membered cyclic ether compound in combination and using a specific amount of the four-membered cyclic ether compound, the polymerization reaction of the release agent composition can be promoted, and a release layer with excellent curability can be formed. This can improve the release properties and blocking resistance of the release film.

[0063] The release agent composition is preferably an ultraviolet-curable release agent composition. The release layer can be formed by applying the release agent composition to the surface of a polyester film substrate and curing it by ultraviolet irradiation. The ultraviolet-curable release agent composition can form a release layer that exhibits excellent release properties and thermal stability.

[0064] The viscosity of the release agent composition is preferably 10 mPa·s or more, more preferably 15 mPa·s or more, and even more preferably 20 mPa·s or more. The viscosity of the release agent composition is preferably 40 mPa·s or less, more preferably 35 mPa·s or less, and even more preferably 30 mPa·s or less. When the viscosity of the release agent composition is equal to or greater than the lower limit, the release agent composition tends to have excellent release properties, suppress cissing when applied, and provide a release layer with a good appearance. When the viscosity of the release agent composition is equal to or less than the upper limit, the release agent composition tends to have excellent coatability and provide a smooth release layer surface. The viscosity of the release agent composition at 25°C is measured using an E-type viscometer ("TVE-22L" manufactured by Toki Sangyo Co., Ltd.).

[0065] <Curing silicone resin> The release agent composition of the present invention contains a curable silicone resin as a release agent component, and preferably contains an ultraviolet-curable silicone resin that can be cured (crosslinked) by ultraviolet irradiation. Such curable silicone resins may be used alone or in combination of two or more. The ultraviolet-curable silicone resin is preferably a modified silicone polymer (modified polysiloxane component) in which one or more cationic polymerization reactive functional groups (or cationic polymerization reaction sites) are introduced into the polysiloxane component of the main chain. One or more of such modified silicone polymers may be used in combination.

[0066] Examples of the cationic polymerization reactive functional group possessed by the modified silicone-based polymer include an epoxy group (particularly, an alicyclic epoxy group). It is preferable that at least two cationic polymerization reactive functional groups are introduced into one molecule of the modified silicone-based polymer. The cationic polymerization reactive functional group may be directly bonded to a silicon atom in the main chain or side chain of the modified silicone-based polymer, or may be bonded via a divalent group (e.g., a divalent organic group such as an alkylene group or an alkyleneoxy group).

[0067] Among these, the ultraviolet-curable silicone resin is preferably a modified silicone polymer having at least one epoxy group selected from the group consisting of a γ-glycidyloxypropyl group, a β(3,4-epoxycyclohexyl)ethyl group, and a β(4-methyl-3,4-epoxycyclohexyl)propyl group.

[0068] Furthermore, as a modified silicone-based polymer into which a cationic polymerization reactive functional group has been introduced, a modified silicone-based polymer having at least two epoxy groups in the molecule can be suitably used. The modified silicone-based polymer having at least two epoxy groups in the molecule is not particularly limited. For example, a modified silicone-based polymer having at least two epoxy group-containing groups (particularly groups containing alicyclic epoxy groups), such as γ-glycidyloxypropyl groups, β(3,4-epoxycyclohexyl)ethyl groups, and β(4-methyl-3,4-epoxycyclohexyl)propyl groups, introduced into one molecule of the polysiloxane component of the main chain can be mentioned.

[0069] The epoxy group-containing group may be, for example, a monomer component such as "HOSi(R 1 )(R 2 )OH" (R 1 is an epoxy group-containing group, R 2 is a hydrogen atom or a hydrocarbon group) can be introduced into the molecule.

[0070] The modified silicone polymer may have either a linear or branched chain structure, or may be a mixture of these.

[0071] Specific examples of commercially available products include: X-62-7622, ​​X-62-7629, X-62-7655, and X-62-7660 manufactured by Shin-Etsu Chemical Co., Ltd.; XS56-C2244, TPR6501S, TPR6500, UV9300, UV9315, and XS56-A2982 manufactured by Momentive Specialty Chemicals; and UVPOLY200, UVPOLY201, and UVPOLY215 manufactured by Arakawa Chemical Industry Co., Ltd.

[0072] The number average molecular weight (Mn) of the curable silicone resin is preferably 1000 or more, more preferably 1500 or more, even more preferably 2000 or more, and particularly preferably 2500 or more. The number average molecular weight (Mn) of the curable silicone resin is preferably 8000 or less, more preferably 7000 or less, even more preferably 6000 or less, and particularly preferably 5000 or less. By setting the number average molecular weight (Mn) of the curable silicone resin to the above-mentioned lower limit or more, when an adhesive layer is laminated on the present release film, the amount of low-molecular-weight silicone resin that elutes and migrates into the adhesive layer can be reduced. Furthermore, by setting the number average molecular weight (Mn) of the curable silicone resin to the above-mentioned lower limit or more, the present release layer can be applied thickly, thereby improving the releasability. On the other hand, by setting the number average molecular weight (Mn) of the curable silicone resin to the above-mentioned upper limit or less, an increase in viscosity of the present release agent composition can be suppressed, and a decrease in flowability can be prevented.

[0073] From the same viewpoint as the number average molecular weight, the mass average molecular weight (Mw) of the curable silicone resin is preferably 5000 or more, more preferably 8000 or more, and even more preferably 10000 or more. The mass average molecular weight (Mw) of the curable silicone resin is preferably 70000 or less, more preferably 60000 or less, and even more preferably 50000 or less.

[0074] In the curable silicone resin, the ratio of the mass average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn) is preferably 1.5 or more, and more preferably 2.0 or more. Furthermore, Mw / Mn is preferably 7.0 or less, more preferably 6.0 or less, and even more preferably 5.0 or less. By keeping Mw / Mn within the above range, it is expected that the crosslinking reaction will proceed efficiently.

[0075] The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were determined by gel permeation chromatography (GPC) using polystyrene as a standard. Specifically, a chromatogram was measured using a GPC measurement system, and the number-average molecular weight (Mn) and weight-average molecular weight (Mw) were determined based on a calibration curve using standard polystyrene. For the measurement, 4 mg of the sample to be measured was dissolved in 4 mL of THF to prepare the measurement solution, and 100 μL of the measurement solution was injected into the GPC measurement system. Tetrahydrofuran (THF) was used as the eluent. The analysis was performed using a Tosoh Corporation "Ecosec 8320" column, a Tosoh Corporation "TSKgelguardcolumn HXL-L" guard column, and four Tosoh Corporation "TSKgelGMHXL" columns connected together. The oven temperature was 40°C, and the THF flow rate was 1.0 mL / min. RI was used for detection.

[0076] The curable silicone resin may be a combination of two or more curable silicone resins, and in this case, it is preferable that the average molecular weight of the two or more curable silicone resins is within the above range. Note that the average here refers to a weighted average weighted by the mass of each resin. Furthermore, when a base resin and a silicone crosslinking agent are used as the curable silicone resin, it is preferable that the number average molecular weight, mass average molecular weight, and Mw / Mn of the base resin are within the above range.

[0077] The viscosity of the curable silicone resin is preferably 1 mPa·s or more, more preferably 5 mPa·s or more, and even more preferably 10 mPa·s or more. The viscosity of the curable silicone resin is preferably 400 mPa·s or less, more preferably 300 mPa·s or less, and even more preferably 200 mPa·s or less. If the viscosity of the curable silicone resin is equal to or greater than the lower limit, the coating liquid has an appropriate viscosity, which suppresses cissing and provides a good coating appearance. If the viscosity of the curable silicone resin is equal to or less than the upper limit, the fluidity of the release agent composition can be maintained, and the release layer surface can be smoothed when the release agent composition is applied. The viscosity of the curable silicone resin at 25°C is measured using an E-type viscometer ("TVE-22L" manufactured by Toki Sangyo Co., Ltd.).

[0078] The curable silicone resin is preferably a solventless curable silicone. Here, "solventless curable silicone" refers to a silicone having a viscosity that allows it to be applied without diluting it with a solvent, and is a silicone resin having a relatively low molecular weight and consisting of short polysiloxane chains.

[0079] Specific examples of commercially available curable silicone resins used in this embodiment include X-62-7622, ​​X-62-7629, X-62-7655, and X-62-7660 manufactured by Shin-Etsu Chemical Co., Ltd.; XS56-C2244, TPR6501S, TPR6500, UV9300, UV9315, and XS56-A2982 manufactured by Momentive Specialty Chemicals; and UVPOLY200, UVPOLY201, and UVPOLY215 manufactured by Arakawa Chemical Industry Co., Ltd.

[0080] The content of the curable silicone resin is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, based on 100% by mass of the solid content of the release agent composition. The content of the curable silicone resin is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less, based on 100% by mass of the solid content of the release agent composition.

[0081] <Three-membered cyclic ether compounds> An example of a three-membered ring cyclic ether compound is a compound containing an epoxy group. Examples of three-membered ring cyclic ether compounds include aliphatic epoxy compounds, aromatic ring-containing epoxy compounds, and alicyclic epoxy compounds. The three-membered ring cyclic ether compound may be a monofunctional epoxy compound having one epoxy group in its structure, or a polyfunctional epoxy compound having two or more epoxy groups. These compounds may be used alone or in combination of two or more.

[0082] Examples of the aliphatic epoxy compounds include monofunctional aliphatic epoxy compounds such as alkyl glycidyl ether, alkoxy glycidyl ether, and allyl glycidyl ether; bifunctional aliphatic epoxy compounds such as neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether; trifunctional aliphatic epoxy compounds such as glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, triglycidyl isocyanurate and its derivatives, and pentaerythritol triglycidyl ether; and pentaerythritol tetraglycidyl ether. tetrafunctional aliphatic epoxy compounds such as glycidyl ether, diglycerol tetraglycidyl ether, and ditrimethylolpropane tetraglycidyl ether; pentafunctional aliphatic epoxy compounds such as polyglycerol pentaglycidyl ether, pentaerythritol pentaglycidyl ether, and dipentaerythritol pentaglycidyl ether; hexafunctional aliphatic epoxy compounds such as sorbitol hexaglycidyl ether and dipentaerythritol hexaglycidyl ether; and other polyfunctional aliphatic epoxy compounds such as trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, and sorbitol polyglycidyl ether.

[0083] Examples of aromatic epoxy compounds include monofunctional aromatic epoxy compounds such as phenol glycidyl ether and EO (ethylene oxide)-modified phenol glycidyl ether; bifunctional aromatic epoxy compounds such as diglycidyl terephthalate, diglycidyl-o-phthalate, diglycidyl resorcinol ether, bisphenol A diglycidyl compounds, bisphenol F diglycidyl compounds, and biphenyl diglycidyl compounds; and other polyfunctional aromatic epoxy compounds such as phenol novolac epoxy compounds and cresol novolac epoxy compounds.

[0084] Examples of the alicyclic epoxy compounds include bifunctional alicyclic epoxy compounds such as hydrogenated bisphenol A diglycidyl compounds, hydrogenated bisphenol F diglycidyl compounds, and hydrogenated biphenyl diglycidyl compounds.

[0085] Among the three-membered ring cyclic ether compounds, it is preferable to use an aliphatic epoxy compound, and it is preferable to use a monofunctional epoxy compound, from the viewpoint of low viscosity. That is, it is preferable that the three-membered ring cyclic ether compound is a monofunctional aliphatic epoxy compound. It is preferable to use an alkyl monoglycidyl ether as the monofunctional aliphatic epoxy compound, and specifically it is preferable to use 2-ethylhexyl glycidyl ether.

[0086] The viscosity of the three-membered cyclic ether compound at 25°C is preferably 100 mPa·s or less, more preferably 50 mPa·s or less, even more preferably 30 mPa·s or less, and particularly preferably 20 mPa·s or less. The lower limit of the viscosity of the three-membered cyclic ether compound at 25°C is not particularly limited, but for example, it is preferably 1 mPa·s or more, more preferably 3 mPa·s or more. By adjusting the viscosity of the three-membered cyclic ether compound at 25°C to be within the above range, the coatability of the release agent composition can be improved, making it easier to obtain a release layer with excellent release properties. When two or more three-membered cyclic ether compounds are used, the viscosity of the three-membered cyclic ether compounds used when uniformly mixed should be within the above range. The viscosity of the three-membered cyclic ether compound at 25°C can be measured using an E-type viscometer.

[0087] The weight average molecular weight of the three-membered ring cyclic ether compound is preferably 40 or more, more preferably 50 or more, and even more preferably 60 or more. The weight average molecular weight of the three-membered ring cyclic ether compound is preferably 700 or less, more preferably 600 or less, and even more preferably 500 or less. By setting the weight average molecular weight of the three-membered ring cyclic ether compound within the above range, the coatability of the present release agent composition can be improved, and a release layer with excellent release properties can be more easily obtained.

[0088] The three-membered ring cyclic ether compound may be appropriately synthesized, or a commercially available product may be used. Specific examples of commercially available products include Denacol EX-121, Denacol EX-171, Denacol EX-192, Denalex R-45EPT, and Denacol EX-221 (all manufactured by Nagase Chemtec Corporation), EPICLON 703, EPICLON 705, EPICLON 707, EPICLON 720, EPICLON 725, and EPICLON 726 (all manufactured by Dainippon Ink and Chemicals, Inc.).

[0089] The content of the three-membered ring cyclic ether compound is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, based on 100% by mass of the solid content of the release agent composition. Furthermore, the content of the three-membered ring cyclic ether compound is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less, based on 100% by mass of the solid content of the release agent composition. By setting the content of the three-membered ring cyclic ether compound to be equal to or greater than the above-mentioned lower limit, the coatability of the release agent composition can be improved, making it easier to obtain a release layer with excellent release properties. Furthermore, by setting the content of the three-membered ring cyclic ether compound to be equal to or less than the above-mentioned upper limit, the curability of the release layer can be improved, and blocking resistance can be more effectively improved.

[0090] <Four-membered cyclic ether compounds> An example of a four-membered ring cyclic ether compound is a compound containing an oxetanyl group. The four-membered ring cyclic ether compound may be a monofunctional oxetane compound having one oxetanyl group in its structure, or a polyfunctional oxetane compound having two or more oxetanyl groups. These compounds may be used alone or in combination of two or more.

[0091] Examples of monofunctional oxetane compounds include 3-ethyl-3-hydroxymethyloxetane, 2-ethylhexyloxetane, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, 3-ethyl-3-(dodecyloxymethyl)oxetane, 3-ethyl-3-(octadecyloxymethyl)oxetane, phenoxymethyloxetane, 3-ethyl-3-(phenoxymethyl)oxetane, 3,3-bis(methoxymethyl)oxetane, 3,3-bis(phenoxymethyl)oxetane, 3-ethyl-3-{[3-(triethoxysilyl)propoxy]methyl}oxetane, and oxetanylsilsesquioxane.

[0092] Examples of polyfunctional oxetane compounds include xylylene bisoxetane, 1-butoxy-2,2-bis[(3-ethyloxetan-3-yl)methoxymethyl]butane, 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane, 1,1,1-tris[(3-ethyloxetan-3-yl)methoxymethyl]propane, 1,4-bis{[(3-ethyloxetan-3-yl)methoxy]methyl}benzene, Examples include 1,3-bis[(3-ethyloxetan-3-yl)methoxy]benzene, 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl, an ester of (2-ethyl-2-oxetanyl)ethanol and terephthalic acid, an ether of (2-ethyl-2-oxetanyl)ethanol and phenol novolac resin, and an ester of (2-ethyl-2-oxetanyl)ethanol and a polycarboxylic acid compound.

[0093] Among the four-membered ring cyclic ether compounds, it is preferable to use a polyfunctional oxetane compound, such as 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane, in order to more effectively enhance the curability of the release layer.

[0094] The viscosity of the 4-membered cyclic ether compound at 25°C is preferably 60 mPa·s or less, more preferably 50 mPa·s or less, even more preferably 40 mPa·s or less, and particularly preferably 30 mPa·s or less. The lower limit of the viscosity of the 4-membered cyclic ether compound at 25°C is not particularly limited, but for example, it is preferably 2 mPa·s or more, more preferably 5 mPa·s or more. By setting the viscosity of the 4-membered cyclic ether compound at 25°C within the above range, the coatability of the release agent composition can be improved, making it easier to obtain a release layer with excellent release properties. When two or more 4-membered cyclic ether compounds are used, it is sufficient that the viscosity of each compound is within the above range. The viscosity of the 4-membered cyclic ether compound at 25°C can be measured using an E-type viscometer.

[0095] The weight average molecular weight of the 4-membered ring cyclic ether compound is preferably 80 or more, more preferably 100 or more, and even more preferably 150 or more. The weight average molecular weight of the 4-membered ring cyclic ether compound is preferably 700 or less, more preferably 600 or less, and even more preferably 500 or less. By setting the weight average molecular weight of the 4-membered ring cyclic ether compound within the above range, the coatability of the release agent composition can be improved, and a release layer with excellent releasability can be more easily obtained.

[0096] The four-membered ring cyclic ether compound may be synthesized appropriately, or a commercially available product may be used. Specific examples of commercially available products include ARONOXETANE OXT-101, ARONOXETANE OXT-212, ARONOXETANE OXT-121, and ARONOXETANE OXT-221 (all manufactured by Toagosei Co., Ltd.), ETERNACOLL (registered trademark) HBOX, OXBP, and OXIPA (all manufactured by Ube Industries, Ltd.), OXE-10 ((3-ethyloxetan-3-yl)methyl acrylate), OXE-30 ((3-ethyloxetan-3-yl)methyl methacrylate), and MEDOL-10 ((3-ethyloxetan-3-yl)methyl acrylate) (all manufactured by Osaka Organic Chemical Industry Co., Ltd.).

[0097] The content of the 4-membered ring cyclic ether compound is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more, based on 100% by mass of the solid content of the release agent composition. Furthermore, the content of the 4-membered ring cyclic ether compound is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less, based on 100% by mass of the solid content of the release agent composition. By setting the content of the 4-membered ring cyclic ether compound to be equal to or greater than the above-mentioned lower limit, the curability of the release layer can be more effectively improved, making it easier to obtain a release layer with excellent durability. Furthermore, by setting the content of the 4-membered ring cyclic ether compound to be equal to or less than the above-mentioned upper limit, blocking resistance can be improved without reducing releasability.

[0098] <Other ingredients> The present release agent composition may contain components other than the curable silicone resin, the three-membered ring cyclic ether compound, and the four-membered ring cyclic ether compound, and may contain, as necessary, a photopolymerization initiator, a catalyst, a reaction control agent, a crosslinking agent, other additives, etc. Furthermore, the present release agent composition may also contain auxiliaries such as a reaction adjuster, an adhesion enhancer, etc.

[0099] <Photopolymerization initiator> The release agent composition preferably contains a photopolymerization initiator. As the photopolymerization initiator, an onium salt-based photopolymerization initiator is suitable. However, the photopolymerization initiator may be used alone or in combination of two or more kinds.

[0100] Examples of the onium salt photopolymerization initiator include the onium salt photoinitiators described in JP-A Nos. 6-32873, 2000-281965, 11-228702, and JP-B No. 8-26120.

[0101] Among these, diaryliodonium salts can be given as onium salt-based photopolymerization initiators. Diaryliodonium salts include those represented by the formula: YI + X - (Y represents an aryl group which may have a substituent. X - is a non-nucleophilic and non-basic anion. - Examples of non-nucleophilic and non-basic anions include SbF6 - , SbCl6 - , BF4 - , [B(C6H5)4] - , [B(C6H5) 4 ] - , [B(C6H4CF3) 4 ] - , [(C6H5)2BF2] - , [C6H5BF3] - , [B(C6H3F2)4] - , AsF6 - , PF6 - , HSO4 - , ClO4 - Examples include:

[0102] Examples of the onium salt-based photopolymerization initiator include triarylsulfonium salts, triarylselenonium salts, tetraarylphosphonium salts, and aryldiazonium salts. Specific examples of the triarylsulfonium salts, triarylselenonium salts, tetraarylphosphonium salts, and aryldiazonium salts are listed below. + X - ","Y3S + X - ","Y4P + X - ","YN2 + X - " (Y, X - is the same as above).

[0103] The content of the photopolymerization initiator is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the curable components contained in the release agent composition, i.e., the total amount of the curable silicone resin, the 3-membered ring cyclic ether compound, and the 4-membered ring cyclic ether compound. Furthermore, the content of the photopolymerization initiator is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less, relative to 100 parts by mass of the curable components contained in the release agent composition. By setting the content of the photopolymerization initiator within the above range, it is possible to enhance the curability of the release layer while maintaining easy releasability, and to more effectively enhance blocking resistance.

[0104] The release agent composition is preferably a solvent-free release agent composition, and preferably does not substantially contain a solvent. In this specification, the term "substantially does not contain a solvent" means that the content of the solvent contained in the release agent composition is 0.1% by mass or less, and preferably the content of the solvent is 0% by mass.

[0105] <Method of manufacturing the release layer> The release layer may be provided by in-line coating, which treats the film surface during the film-forming process of the polyester film substrate, or by off-line coating, which applies the release layer to a polyester film substrate once produced outside the system. Off-line coating is more preferred.

[0106] As a method for providing a release layer on a polyester film substrate, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, etc. can be used.

[0107] The polyester film substrate may be previously subjected to a surface treatment such as a corona treatment or a plasma treatment.

[0108] As the energy source for curing by irradiation with active energy rays, known devices and energy sources can be used, such as a fusion (H) lamp, a metal halide lamp, a high-pressure mercury lamp (ozone-generating type or ozone-less type), and a UV-LED.

[0109] The amount of ultraviolet light irradiation is not particularly limited, but is preferably 10 to 3000 (mJ / cm) in terms of cumulative light dose. 2 ), preferably 50 to 2000 (mJ / cm 2 ), more preferably 100 to 1000 (mJ / cm 2 ) range is good.

[0110] <Arbitrary layer> The present release film may have "another layer" between the polyester film substrate and the release layer. Examples of the "other layer" include a resin layer and an antistatic layer. Examples of the resin layer include layers having various functions such as an easy-adhesion layer, an antiblocking layer, and an oligomer sealing layer.

[0111] For example, the laminated film including the coating layer may have the following layer structure. (1) Polyester film substrate / resin layer / release layer (2) Polyester film base / antistatic layer / release layer (3) Resin layer / Polyester film substrate / Release layer (4) Resin layer / polyester film substrate / resin layer / release layer (5) Resin layer / Polyester film substrate / Antistatic layer / Release layer (6) Antistatic layer / polyester film substrate / release layer (7) Antistatic layer / polyester film substrate / resin layer / release layer (8) Antistatic layer / polyester film substrate / antistatic layer / release layer (9) Antistatic layer / resin layer / polyester film substrate / release layer (10) Antistatic layer / resin layer / polyester film substrate / resin layer / release layer (11) Antistatic layer / resin layer / polyester film substrate / antistatic layer / release layer

[0112] The resin layer preferably contains a polymer and a crosslinking agent. Examples of the polymer include polyurethane, polyester, and acrylic resin. Among these, the polymer is preferably polyurethane, and more preferably polyester polyurethane. The polymer preferably has carboxylic acid residues, at least a portion of which is hydrolyzed using amine or ammonia. The glass transition temperature (Tg) of the polymer is preferably 0°C or higher, and more preferably 40°C or higher. Examples of crosslinking agents contained in the resin layer include melamine-based, epoxy-based, and oxazoline-based resins.

[0113] The resin layer preferably contains a water-dispersible polyolefin resin and a crosslinking agent. Examples of the polyolefin resin include compounds having the following compounds (1) to (5) as a basic skeleton. (1) Waxes, resins, and rubbers made of homopolymers or copolymers of α-olefin-based unsaturated hydrocarbons such as ethylene, propylene, 1-butene, and 4-methyl-1-pentene. Examples include polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymers, ethylene-1-butene copolymers, and propylene-1-butene copolymers. (2) Rubber-like copolymers of two or more of the above α-olefins with conjugated or non-conjugated dienes, such as ethylene-propylene-butadiene copolymer, ethylene-propylene-dicyclopentadiene copolymer, ethylene-propylene-ethylidenenorbornene copolymer, ethylene-propylene-1,5-hexadiene copolymer, and isobutene-isoprene copolymer. (3) Copolymers of the above α-olefins with conjugated or non-conjugated dienes, such as ethylene-butadiene copolymers and ethylene-ethylidenenorbornene copolymers. (4) Copolymers of the above α-olefins (especially ethylene) with vinyl acetate and their completely or partially saponified products. (5) Graft polymers in which the above-mentioned conjugated or non-conjugated dienes or vinyl acetate etc. are grafted onto the above-mentioned α-olefin homopolymers or copolymers, and their completely or partially saponified products. Examples of the crosslinking agent include melamine-based, epoxy-based, amide-based, and acrylamide-based compounds, polyisocyanates, blocked polyisocyanates, carbodiimide compounds, etc. Examples of the melamine-based crosslinking agent include alkylol- or alkoxyalkylol-based melamine compounds such as methoxymethylated melamine and butoxymethylated melamine, and compounds in which melamine is partially co-condensed with urea or the like can also be used.

[0114] The antistatic layer contains an antistatic agent. Examples of antistatic agents include aliphatic conjugated polymers such as polyacetylene; aromatic conjugated polymers such as poly(p-phenylene) and polyfluorene; heterocyclic conjugated polymers such as polypyrrole, polyfuran, polythiophene, and alkylenedioxypolythiophene; mixed conjugated polymers such as polythienylenevinylene and poly(p-phenylenevinylene); heteroatom-containing conjugated polymers such as polyaniline and polythiazyl; conductive carbons such as carbon black and Ketjen black; tin oxide ultrafine particles such as tin oxide, antimony-doped tin oxide, and tin oxide-doped indium; compounds having an ammonium group such as quaternary ammonium salts; ionic liquids; thiophene-based compounds; boron-based compounds; sulfonates; lithium salts; and siloxane-based compounds. The antistatic layer can be formed by applying these antistatic agents alone or as a liquid composition mixed with a binder resin, a crosslinking agent, etc. to the surface of a substrate. Quaternary ammonium salt compounds are particularly preferred from the viewpoint of availability. Heterocyclic conjugated polymers are also preferred from the viewpoint of high antistatic properties. One or more types of antistatic agents may be used.

[0115] As the antistatic agent of a quaternary ammonium salt compound, a quaternary ammonium base-containing polymer having a component containing a quaternary ammonium base in the main chain or side chain of the molecule is preferred. Specific examples of the quaternary ammonium base-containing polymer include acrylic resins, urethane resins, polyvinyl resins, and polyamine resins. Examples of the monomer having a quaternary ammonium base that constitutes the quaternary ammonium base-containing polymer include polymerizable monomers having a group such as a pyrrolidium ring, a quaternized alkylamine, a quaternized hydroxyalkylamine, a quaternized N-alkylaminoacrylamide, vinylbenzyltrimethylammonium salt, 2-hydroxy3-methacryloxypropyltrimethylammonium salt, and acryloyloxyethyldimethylammonium methylsulfonate. These monomers may be used alone or in combination.

[0116] Examples of anions that can serve as counter ions of the quaternary ammonium base include ions of halogen, alkyl sulfate, alkyl sulfonate, nitric acid, sulfuric acid, phosphate, acetate, sulfamate, etc. Among these, alkyl sulfate, alkyl sulfonate, and nitrate ions are preferred from the viewpoint of heat resistance.

[0117] The quaternary ammonium salt group-containing polymer may be copolymerized with other monomers as needed, such as (meth)acrylic acid esters, (meth)acrylic acid amides, vinyl esters such as vinyl acetate and vinyl butyrate, unsaturated carboxylic acids and ester compounds thereof such as maleic acid, fumaric acid, and oleic acid, and unsaturated hydrocarbon compounds such as styrene, isoprene, and butadiene.

[0118] Furthermore, the molecular weight of the quaternary ammonium salt group-containing polymer is preferably a predetermined amount or more. This can prevent the polymer from falling off the antistatic layer and also improve heat resistance stability. From this perspective, the number-average molecular weight of the quaternary ammonium salt group-containing polymer is usually 1,000 or more, preferably 2,000 or more, and more preferably 5,000 or more. Furthermore, the upper limit of the number-average molecular weight is preferably set to 500,000 or less, and preferably 200,000 or less. This can prevent problems such as excessively high viscosity of the coating solution.

[0119] The blending amount of the quaternary ammonium salt group-containing polymer in the antistatic layer is preferably in the range of 20 to 70% by mass, more preferably in the range of 40 to 70% by mass, based on the total mass of the antistatic layer.

[0120] In order to improve the antistatic properties of the antistatic layer, a heterocyclic conjugated polymer is preferred, and polythiophene or a derivative thereof is more preferred. Examples of polythiophene derivatives include compounds in which functional groups are bonded to the 3rd and 4th positions of the thiophene ring, and compounds represented by the following formula (I), in which oxygen atoms are bonded to the 3rd and 4th carbon atoms, are preferred because they facilitate the conversion of the coating liquid to a water-based solution.

[0121] [ka]

[0122] In the above formula (I), R1 and R2 each independently represent a hydrogen atom, an aliphatic chain hydrocarbon group having 1 to 12 carbon atoms, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group, and R1 and R2 may be linked to form a ring. Specific examples of groups other than hydrogen atoms represented by R1 and R2 include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a cyclohexyl group, and a phenyl group. Furthermore, examples of antistatic agents in which R1 and R2 are linked to form a ring include polythiophene derivatives represented by the following formula (II):

[0123] [ka]

[0124] In the above formula (II), n is an integer of 1 to 4. For example, in the above formula (II), compounds where n = 1 (methylene group), n = 2 (ethylene group), or n = 3 (propylene group) are preferred. Among these, a compound where n = 2 (ethylene group), i.e., poly-3,4-ethylenedioxythiophene, is particularly preferred.

[0125] The antistatic layer more preferably contains the above-mentioned composition comprising a polythiophene and a polyanion, or the above-mentioned composition comprising a polythiophene derivative and a polyanion.

[0126] Polyanions refer to "acidic polymers in a free acid state," and are preferably polymeric carboxylic acids or polymeric sulfonic acids. Specific examples of polymeric carboxylic acids include polyacrylic acid, polymethacrylic acid, and polymaleic acid. Specific examples of polymeric sulfonic acids include polystyrene sulfonic acid and polyvinyl sulfonic acid. Among these, polystyrene sulfonic acid is most preferred in terms of conductivity. The free acid may be partially neutralized and take the form of a salt. By using these polyanions during polymerization of polythiophene or polythiophene derivatives, it is believed that the polythiophene-based compound, which is inherently insoluble in water, can be easily dispersed or made aqueous, and its acid function also functions as a doping agent for the polythiophene-based compound.

[0127] Furthermore, the polymeric carboxylic acid or polymeric sulfonic acid can also be used in the form of a copolymer with other copolymerizable monomers, such as acrylic acid esters, methacrylic acid esters, or styrene.

[0128] The molecular weight of the polymeric carboxylic acid or polymeric sulfonic acid used as the polyanion is not particularly limited, but from the viewpoint of the stability and conductivity of the antistatic coating solution used to form the antistatic layer, the weight-average molecular weight is preferably 1,000 to 1,000,000, and more preferably 5,000 to 150,000. Alkali salts such as lithium salts and sodium salts, or ammonium salts may be included as long as they do not impair the properties of the present invention. Even in the case of neutralized salts, it is known that polystyrene sulfonic acid and ammonium salts, which function as very strong acids, shift the equilibrium toward the acidic side as the equilibrium reaction progresses after neutralization, which is thought to result in their function as dopants.

[0129] If necessary, the coating layer may contain an antifoaming agent, a coatability improver, a thickener, an organic lubricant, a bactericide, inorganic particles, organic particles, an antistatic agent, an antioxidant, an ultraviolet absorber, a foaming agent, or a dye.

[0130] To form a coating layer, a coating agent (applicant) is applied to the surface of the polyester film. For example, a coating device such as a reverse roll coater, gravure coater, rod coater, or air doctor coater can be used for the application. Furthermore, the polyester film may be subjected to a chemical treatment or discharge treatment to modify the film surface before application.

[0131] The thickness of the coating layer (thickness after drying) is preferably 0.01 μm or more, more preferably 0.02 μm or more, and is preferably 1 μm or less.

[0132] The coating layer is preferably formed during the stretching process of the polyester film, and is preferably formed by so-called in-line coating. When a coating layer is provided on a polyester film by in-line coating, coating can be performed simultaneously with stretching, and the thickness of the coating layer can be changed by the stretching ratio, so that a film suitable as a polyester film can be produced. When the coating layer is formed by in-line coating, for example, in sequential biaxial stretching, it is preferable to perform the coating treatment after the completion of longitudinal stretching and before transverse stretching.

[0133] (Release film properties) <Normal peel strength> For example, Nitto Denko Corporation's "No. 31B" acrylic adhesive tape is applied to the release layer surface of this release film by pressing it with a rubber roller (2 kg) (twice back and forth), then cut into a size of 50 mm x 300 mm, and left at room temperature for 1 hour. After measuring the peel strength (normal peel strength), the normal peel strength is preferably 75 mN / cm or less, more preferably 70 mN / cm or less. Furthermore, the normal peel strength is usually preferably 1 mN / cm or more, more preferably 5 mN / cm or more, and even more preferably 10 mN / cm or more.

[0134] This release film was wound up to 100 m to prepare a release film roll, which was then stored for one week under conditions of 23°C and a relative humidity of 50%. After that, the release film was unwound, and no sticking occurred between the polyester film substrate and the release layer when unwound.

[0135] When 100 m of this release film is wound up to prepare a release film roll and the peel force of the release film measured immediately thereafter is defined as P, and when 100 m of this release film is wound up to prepare a release film roll and the peel force of the release film measured after storing it for one week is defined as Q, the increase in peel force calculated by the following formula is preferably 10 mN / cm or less, more preferably 5 or less, and even more preferably 3 or less. The lower limit of the increase in peel force is 0%. Increase in peel force (mN / cm) = QP

[0136] <Residual adhesion rate> It is preferable that the release film has little migration of the release component from the release layer when it is bonded to the adhesive layer, and an indicator of this is the residual adhesion rate (%). The residual adhesion rate (%) is an indicator of the degree to which the release agent migrates to the evaluation film when the evaluation film is placed on the release layer surface of the release film and pressed. With a release film with high migration, a lot of silicone adheres to the overlapping evaluation film, which reduces the peel force of the adhesive tape bonded to the evaluation film and also reduces the residual adhesion rate (%). Therefore, it is preferable that the release film has a high residual adhesion rate (%); specifically, 90% or more is preferable, 92% or more is even more preferable, and 94% or more is particularly preferable. The residual adhesion rate (%) is calculated using the following method. First, adhesive tape "No. 31B" (manufactured by Nitto Denko Corporation) is pressed back and forth onto the surface of the release layer with a 2 kg rubber roller, and after one hour at room temperature, the pressed release film is peeled off, and adhesive tape "No. 31B" is used to measure the adhesive strength F in accordance with the method of JIS-C-2107 (adhesion strength to stainless steel plate, 180° peel method).The residual adhesion rate is then determined as the percentage of F relative to the adhesive strength F0 when adhesive tape "No. 31B" is directly adhered to and peeled off from the stainless steel plate.

[0137] Since the release film has the above-mentioned release layer, it can exhibit excellent releasability and can therefore be suitably used as a protective layer for an adhesive layer. The adhesive layer to be protected can be an adhesive layer formed from a general-purpose adhesive, and examples of the adhesive can include known adhesives such as polyester-based adhesives, acrylic-based adhesives, urethane-based adhesives, silicone-based adhesives, and rubber-based adhesives.

[0138] (Release film roll) This embodiment relates to a release film roll (hereinafter also referred to as "this roll") formed by winding the release film described above.

[0139] This roll is formed by winding a release film around a core such as a paper tube, metal tube, or plastic tube. The diameter of the core is not particularly limited, but is preferably 10 mm or more, more preferably 20 mm or more, and even more preferably 30 mm or more. The upper limit of the core diameter is not particularly limited, but is preferably, for example, 500 mm or less.

[0140] The width of the roll is preferably 0.2 m or more, more preferably 0.3 m or more, and even more preferably 1 m or more. The upper limit of the width of the roll is not particularly limited, but is preferably, for example, 3 m or less.

[0141] Furthermore, the length of the release film wound onto this roll is preferably 1000 m or more, more preferably 2000 m or more, even more preferably 4000 m or more, and particularly preferably 6000 m or more. There are no particular limitations on the upper limit of the length of the release film wound onto this roll, but for example, it is preferably 65000 m or less, more preferably 40000 m or less, and even more preferably 20000 m or less. The longer the wound length of the release film constituting this roll, the more likely blocking occurs, but since this release film exhibits excellent blocking resistance, it is possible to suppress the occurrence of blocking even when the wound length is long.

[0142] (adhesive body) The present embodiment relates to an adhesive body (hereinafter also referred to as "the present adhesive body") having an adhesive layer on the release layer of the above-mentioned release film. Examples of the form of the adhesive body include an adhesive tape, an adhesive sheet, an adhesive film, etc.

[0143] Examples of the adhesive used in the adhesive layer of the present adhesive body include known adhesives such as polyester-based adhesives, acrylic-based adhesives, urethane-based adhesives, silicone-based adhesives, and rubber-based adhesives.

[0144] Acrylic pressure-sensitive adhesives can be prepared by using an acrylic polymer as the main component, which is obtained by a conventional polymerization method such as solution polymerization, emulsion polymerization, or UV polymerization, and by adding various additives such as a crosslinking agent, a tackifier, a softener, an antioxidant, or a filler, as needed.

[0145] As the acrylic polymer, for example, a copolymer of a monomer mixture containing an alkyl (meth)acrylate such as butyl (meth)acrylate or 2-ethylhexyl (meth)acrylate as the main component, and optionally containing other monomers as copolymerizable modifying monomers, such as a hydroxy group-containing monomer such as 2-hydroxyethyl (meth)acrylate, a carboxy group-containing monomer such as (meth)acrylic acid, a styrene-based monomer such as styrene, or a vinyl ester such as vinyl acetate, can be used.

[0146] Further, examples of polyester-based adhesives include adhesives whose main component is a polyester-based polymer in which an aliphatic carbonate diol (for example, a carbonate diol obtained by reacting a diol component such as butanediol with a carbonate compound such as ethylene carbonate) is an essential polyol component.

[0147] The adhesive layer of the adhesive body can be formed, for example, by applying a solution containing an adhesive onto the release layer of a release film and drying it. The thickness of the adhesive layer can be appropriately selected taking into consideration adhesive properties, etc., and is usually 3 to 100 μm, preferably 5 to 90 μm, and more preferably 10 to 80 μm. [Example]

[0148] The features of the present invention will be explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0149] <Measurement and evaluation methods> (1) Thickness To suppress reflection from the backside, black tape (Nichiban Co., Ltd.'s "Vinyl Tape VT-50") was applied to the backside of the release film beforehand. Measurements were performed using a spectrophotometer (JASCO Corporation's UV-Visible Spectrophotometer "V-670") to measure absolute reflectance over a wavelength range of 300 to 800 nm under the following conditions: synchronous mode, 5° incident angle, N polarization, fast response, 1.0 nm data acquisition interval, 10 nm bandwidth, and 1000 m / min scan speed. The film thickness of the release layer was determined by comparing the data obtained from this measurement with data calculated assuming a silicone refractive index of 1.43.

[0150] (2) Arithmetic mean height (Sa) · Maximum height (Sz) The arithmetic mean height (Sa) and maximum height (Sz) were measured in accordance with ISO 25178 using a surface profile measurement system (Hitachi High-Tech Science Corporation's "VertScan" (registered trademark) R5500). The measurement was performed at a magnification of 5x, and the surface of the polyester film substrate (exposed surface of the substrate film) on which the release layer of the release film was not laminated was measured using optical interferometry. Furthermore, correction and baseline correction were performed under the following conditions, and the data was read. Compensation: Full Baseline correction: Surface correction (4th order polynomial approximation)

[0151] (3) Elastic modulus of the release layer The modulus of elasticity of the release layer was measured at a point where the indentation depth was 50 nm at room temperature (25° C.) using a nanoindenter (TI950 TriboIndenter) manufactured by Hysitron.

[0152] (4) Normal peel strength of release film Nitto Denko Corporation's "No. 31B" acrylic adhesive tape was applied to the release layer surface of the release film by pressing it with a rubber roller (2 kg) (twice back and forth), then cut into a size of 50 mm x 300 mm and left at room temperature for 1 hour, after which the peel strength was measured. To measure the peel strength, an Intesco Corporation "Intesco Model 2001" was used, and the release film was peeled at 180° at a pulling speed of 0.3 (m / min).

[0153] (5) Residual adhesion rate (without heat) Adhesive tape "No. 31B" (manufactured by Nitto Denko Corporation) was pressed back and forth onto the surface of the release layer with a 2 kg rubber roller, and after one hour at room temperature, the pressed release film was peeled off and adhesive tape "No. 31B" was used to measure the adhesive strength F according to the method of JIS-C-2107 (adhesion strength to stainless steel plate, 180° peeling method). The percentage of F relative to the adhesive strength F0 when adhesive tape "No. 31B" was directly adhered to and peeled off the stainless steel plate was taken as the residual adhesion rate.

[0154] (6) Blocking resistance [Film sticking] The prepared release film was wound up to a length of 100 m to prepare a release film roll, which was then stored for one week under conditions of 23°C and a relative humidity of 50%. Thereafter, the release film was unwound, and the adhesion of the release film when unwound was visually confirmed. <Evaluation criteria> (Film sticking) ◯: There was absolutely no adhesion between the base film and the release layer ×: Sticking to the release layer occurred over the entire surface of the base film [Changes in peelability] The increase in peel force when unwinding the film from the film roll immediately after production and after one week of storage was calculated using the following formula and evaluated according to the following criteria: 100 m of this release film was wound up to produce a release film roll, and the peel force of the release film measured immediately thereafter was designated P, and 100 m of this release film was wound up to produce a release film roll, and the peel force of the release film measured after one week of storage was designated Q. Increase in peel force (mN / cm) = QP <Evaluation criteria> (Peeling change) ○: Increase in peel force is less than 10.0 mN / cm ×: Increase in peel strength is 10.0 mN / cm or more

[0155] (7) Hardening of the release layer ○: No change △: Cracks in the release layer were partially present ×: Cracks were present on the entire surface of the release layer

[0156] <Raw materials> (1) Raw material for polyester film substrate (i) Polyester P1 Polyethylene terephthalate homopolymer chips (intrinsic viscosity: 0.66 dl / g) (ii) Polyester P2 Polyethylene terephthalate homopolymer chips containing 1000 ppm of amorphous silica with an average particle size of 2 μm (intrinsic viscosity: 0.62 dl / g)

[0157] (2) Raw materials for the release layer (i) Curable silicone resin UV cationic silicone release agent: X-62-7622 (Shin-Etsu Chemical Co., Ltd.) (ii) Three-membered cyclic ether compounds 2-Ethylhexyl glycidyl ether: Denacol EX-121 (Nagase ChemTech Corporation) (iii) 4-membered cyclic ether compounds 3-Ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane: Aronoxetane OXT-221 (Toagosei Co., Ltd.) (iv) Photopolymerization initiator Cat-7608 (Shin-Etsu Chemical Co., Ltd.)

[0158] Example 1 (1) Preparation of polyester film substrate <Method for producing polyester (1)> Starting materials were 100 parts by mass of dimethyl terephthalate and 55 parts by mass of ethylene glycol. 0.04 parts by mass of magnesium acetate tetrahydrate was added to the reactor as a catalyst. The reaction was initiated at 150°C and gradually increased to 230°C after 3 hours as methanol was distilled off. After 4 hours, the transesterification reaction was essentially complete. 0.02 parts by mass of ethyl acid phosphate was added to the reaction mixture, followed by 0.04 parts by mass of antimony trioxide. The polycondensation reaction was carried out for 4 hours. During this time, the temperature was gradually increased from 230°C to 280°C. Meanwhile, the pressure was gradually reduced from atmospheric pressure to a final value of 0.3 mmHg. Due to changes in the stirring power of the reactor, the reaction was terminated at a point corresponding to an intrinsic viscosity of 0.59 dL / g. The polymer was discharged under nitrogen pressure, yielding polyester (1) with an intrinsic viscosity of 0.59 dL / g.

[0159] <Method for producing polyester (2)> Starting materials were 100 parts by mass of dimethyl terephthalate and 45 parts by mass of ethylene glycol. 0.06 parts by mass of magnesium acetate tetrahydrate was added to the reactor as a catalyst. The reaction was initiated at 150°C and gradually increased to 230°C after 3 hours as methanol was distilled off. After 4 hours, the transesterification reaction was essentially complete. 0.03 parts by mass of ethyl acid phosphate was added to the reaction mixture, followed by 0.3 parts by mass of silica particles with an average particle size of 2.7 μm dispersed in ethylene glycol and 0.03 parts by mass of antimony trioxide. The polycondensation reaction was carried out for 4 hours. During this time, the temperature was gradually increased from 230°C to 280°C. Meanwhile, the pressure was gradually reduced from atmospheric pressure to a final value of 0.3 mmHg. Due to changes in the stirring power of the reactor, the reaction was terminated at a point corresponding to an intrinsic viscosity of 0.59 dL / g. The polymer was discharged under nitrogen pressure, yielding polyester (2) with an intrinsic viscosity of 0.59 dL / g.

[0160] <Method for producing polyester (3)> Polyester (3) having an intrinsic viscosity of 0.60 was obtained in the same manner as polyester (2), except that 10 parts by mass of organic particles (styrene-divinylbenzene: styrene-based resin) having an average particle size of 4.5 μm were added instead of the silica particles in polyester (2).

[0161] An 80 / 20 mass ratio blend of polyester (1) and polyester (2) was used as the raw material for Layer A, polyester (1) alone was used as the raw material for Layer B, and a 94 / 6 mass ratio blend of polyester (1) and polyester (3) was used as the raw material for Layer C. These raw materials were fed into an extruder. Each raw material was heated and melted at 285°C and co-extruded to form a three-type, three-layer (A / B / C) structure with a thickness ratio of A / B / C = 5 / 90 / 5. The resulting film was cooled and solidified while in close contact with a mirror-finished cooling drum with a surface temperature of 40-50°C to produce an unstretched polyethylene terephthalate film. This film was stretched 3.0 times in the longitudinal direction while passing through a group of heated rolls at 85°C to produce a uniaxially oriented film. The film was then introduced into a tenter stretching machine, stretched 4.1 times in the width direction at 100°C, and further heat-treated at 235°C, followed by a 2% relaxation treatment in the width direction to obtain a biaxially oriented polyester film with a thickness of 50 μm.

[0162] (2) Formation of a release layer The release agent composition (hereinafter sometimes abbreviated as "release agent") was prepared by mixing the curable silicone resin, the three-membered ring cyclic ether compound, the four-membered ring cyclic ether compound, and the photopolymerization initiator in a ratio of 50 / 45 / 5 / 1 (parts by mass), to obtain a release agent composition (viscosity: 23 mPa s). The release agent composition was applied to the polyester film substrate obtained above using a gravure roll, and the accumulated light dose was 200 mJ / cm. 2 Thus, a release film having a release layer with a thickness of 1000 nm was obtained.

[0163] (Comparative Example 1) A release film was obtained in the same manner as in Example 1, except that the polyester film substrate in Example 1 was changed to one prepared by the following method, and the composition of the release agent composition was changed as follows. <Preparation of polyester film substrate> Polyester P1 was used as the raw material for the intermediate layer, and polyester P2 was used as the raw material for the surface layer. Each raw material was melt-extruded using a separate melt extruder. The resulting amorphous sheet, consisting of a three-layer laminate of two types of materials (surface layer / intermediate layer / surface layer), was co-extruded onto a cooled casting drum and cooled and solidified to obtain an unoriented sheet. The sheet was then stretched 3.4 times in the machine direction (longitudinal direction) at 90°C. It was then preheated to 120°C in a tenter, stretched 4.1 times in the transverse direction, and heat-treated at 230°C for 3 seconds to obtain a polyester film as the substrate. The resulting polyester film had a thickness of 38 μm, with a surface layer / intermediate layer / surface layer thickness configuration of 3 μm / 32 μm / 3 μm. <Formation of release layer> A release agent composition (hereinafter sometimes abbreviated as "release agent") was obtained by mixing the curable silicone resin / three-membered ring cyclic ether compound / photopolymerization initiator so that the composition was 50 / 50 / 1 (parts by mass). The release agent composition was applied to the polyester film substrate obtained above using a gravure roll, and an accumulated light dose of 200 mJ / cm was applied. 2 The resulting film was irradiated with ultraviolet light so as to obtain a release film having a release layer with a thickness of 700 nm.

[0164] (Comparative Example 2) A release film was obtained in the same manner as in Example 1, except that the polyester film substrate in Example 1 was changed to the modified polyester film substrate produced in Comparative Example 1.

[0165] [Table 1]

[0166] The release films of the examples, which had a release layer formed from a specific solventless release agent composition and a polyester film substrate with a surface roughness within a specific range, exhibited both excellent releasability and blocking resistance.

Claims

1. A polyester film substrate; a release layer on the first surface side of the polyester film substrate, the release layer is a layer formed from a release agent composition containing a curable silicone resin, a three-membered ring cyclic ether compound, and a four-membered ring cyclic ether compound; the content of the four-membered ring cyclic ether compound contained in the release agent composition is 0.5 to 20% by mass relative to 100% by mass of the solid content, The release film, wherein the arithmetic mean height (Sa) of the second surface of the polyester film substrate is 40 to 100 nm.

2. The release film according to claim 1, wherein the second surface of the polyester film substrate has a maximum height (Sz) of 2,000 to 10,000 nm.

3. 2. The release film according to claim 1, wherein the polyester film substrate has a polyester layer on the second surface side thereof containing 0.1 to 2.0 mass % of particles having an average particle size of 1 to 8 μm.

4. 2. The release film according to claim 1, wherein the content of the three-membered ring cyclic ether compound contained in the release agent composition is 10 to 70% by mass relative to 100% by mass of the solid content.

5. The release film of claim 1 , wherein the release agent composition further comprises a photopolymerization initiator.

6. 2. The release film according to claim 1, wherein the release layer has a thickness of 150 to 2000 nm.

7. A release film roll obtained by winding up the release film according to any one of claims 1 to 6.

8. An adhesive body having an adhesive layer on the release layer of the release film according to any one of claims 1 to 6.

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