Laminated polyethylene terephthalate film, release film, and method for producing laminated polyethylene terephthalate film

Abstract

Provided is a laminated polyethylene terephthalate film that, even when a recycled resin is used therein, can suppress transfer of a surface shape to processed goods. This laminated polyethylene terephthalate film comprises a first coating layer, an intermediate layer, and a second coating layer. The first coating layer has a surface on which a functional layer is to be laminated. The intermediate layer includes at least one element among Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au elements. The total amount of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au elements is 0.1-5000 ppm with respect to the total mass of the intermediate layer. The laminated polyethylene terephthalate film satisfies at least one of requirements (1) and (2).　(1) The three-dimensional center plane average surface roughness of said surface is 1-7.5 nm.　(2) The maximum peak height of said surface is 220 nm or less.

Description

Laminated polyethylene terephthalate film, release film, and method for producing laminated polyethylene terephthalate film

[0001] The present invention relates to a laminated polyethylene terephthalate film, a release film, and a method for producing a laminated polyethylene terephthalate film.

[0002] Films (hereinafter sometimes referred to as process films) that include functional layers having various functions on the surface of a base film such as a synthetic resin are used in fields such as electronic components, optical components, labels, mold release materials, etc. Process films that have been used, do not meet specifications, or have been damaged during distribution are usually discarded (hereinafter sometimes referred to as films to be discarded).

[0003] Patent Document 1 discloses a method for measuring the amount of impurities in used films, a method for recycling used films, and a method for converting the recycled raw materials into films. For example, Patent Document 1 discloses removing a silicone-containing release layer formed on the surface of a substrate film, barium titanate, and an adhesive as residues.

[0004] Japanese Patent Application Laid-Open No. 2021-115862

[0005] For the effective use of resources, it is preferable to recycle films that are scheduled for disposal. In particular, the distribution volume of films having a functional layer and a substrate film (i.e., films with functional layers), such as release films, has been increasing in recent years, and the amount of waste has also been increasing. Therefore, there is a demand for the establishment of a circular recycling system for release films. In other words, there is a demand for release films that are scheduled for disposal to be utilized in the production of release films.

[0006] In addition, recycling yield is an important factor in establishing a circular recycling system.

[0007] The technology of Patent Document 1 varies in recycling yield depending on the amount of impurities contained in the film, and the recycling yield tends to deteriorate as the amount of impurities increases. For example, the technology of Patent Document 1 applies thermal recycling when the amount of impurities in the film is 0.2% by weight or more when the total weight of the film is 100% by weight. In this case, the recycling yield is 0.

[0008] Furthermore, release films are always required to have low surface roughness from the viewpoint of surface transfer onto processed products, and the same applies to recycled films. The processed products are, for example, resin sheets such as ceramic green sheets, multilayer ceramic capacitors made of ceramic green sheets, semiconductor components, or optical films. However, while the technology of Patent Document 1 describes the amount of impurities, it does not describe the film surface roughness, raising concerns that the desired surface roughness may not be achieved.

[0009] Therefore, an object of the present invention is to provide a laminated polyethylene terephthalate film that can suppress the transfer of surface topography to processed products, a method for producing the same, and a release film. A preferred embodiment of the present invention relates to a laminated polyethylene terephthalate film that has an excellent recycling yield and can suppress the transfer of surface topography to processed products, even when using recycled resin recovered from films to be discarded, particularly films with functional layers, such as release films. The recycled resin contains one or more of the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au.

[0010] As a result of intensive research to solve the above-mentioned problems, the inventors have succeeded in controlling the surface roughness within a predetermined range in a recycled film containing impurities of the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au, and have discovered that the above-mentioned problems can be solved, thereby completing the present invention.

[0011] More specifically, in recent years, there has been an increasing need for environmental impact reduction activities, including the SDGs and carbon neutrality. Therefore, the present inventors conducted extensive research into improving the recycling yield of process films, such as release films, and found that, among various factors, controlling the recycling process of the process film is essential to improving the recycling yield of process films. However, simply improving the recycling yield may result in insufficient properties required of the process film. Therefore, when a laminated polyethylene terephthalate film is used as a process film, for example, as a base film for a release film, it is necessary to achieve a good balance between improving the releasability of the processed product and suppressing the transfer of the surface shape of the process film to the processed product. There is also a demand for recycling films containing particles. In light of this situation, the present inventors have developed a laminated polyethylene terephthalate film, a manufacturing method thereof, and a release film that can suppress the transfer of surface shape to processed products, even when using recycled resins containing one or more of the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au.

[0012] The present invention provides the following aspects: [Item 1] A laminated polyethylene terephthalate film comprising a first coating layer containing a polyethylene terephthalate resin, an intermediate layer containing a polyethylene terephthalate resin, and a second coating layer containing a polyester resin, wherein the first coating layer has a surface on which a functional layer is laminated, and the intermediate layer contains one or more of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au, and the total amount of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au is 0.1 ppm or more and 5000 ppm or less with respect to the total mass of the intermediate layer, and the laminated polyethylene terephthalate film satisfies at least one of the following requirements (1) and (2): (1) the three-dimensional center plane average surface roughness (SRa) of the surface is 1 nm or more and 7.5 nm or less, and (2) the maximum peak height (SRp) of the surface is 220 nm or less. [Item 2] A laminated polyethylene terephthalate film comprising a first coating layer containing a polyethylene terephthalate resin, an intermediate layer containing a polyethylene terephthalate resin, and a second coating layer containing a polyester resin, wherein the first coating layer has a surface on which a functional layer is laminated, and the intermediate layer contains one or more of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au, and the total amount of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au is 0.1 ppm or more and 5000 ppm or less relative to the total mass of the laminated polyethylene terephthalate film, and the laminated polyethylene terephthalate film satisfies at least one of the following requirements (1) and (2): (1) the three-dimensional center plane average surface roughness (SRa) of the surface is 1 nm or more and 7.5 nm or less, and (2) the maximum peak height (SRp) of the surface is 220 nm or less. Here, in items 1 and 2, "the total amount of Si element, Ti element, Ba element, Ni element, Cu element, Pt element, Pd element, Ag element, and Au element" means the total amount of these elements in the laminated polyethylene terephthalate film.[Item 3] The laminated polyethylene terephthalate film according to Item 1 or 2, wherein the first coating layer is a layer that does not substantially contain particles, and the thickness of the first coating layer is 7.0 μm or more and 20.0 μm or less. [Item 4] The melt resistivity at 275°C (ρi(10. 8The laminated polyethylene terephthalate film according to any one of Items 1 to 3, having a resistivity (Ω·cm) of 1.00 or less. [Item 5] The intermediate layer contains one or more of Ti, Ni, Cu, Pt, Pd, Ag, and Au, and the total amount of Ti, Ni, Cu, Pt, Pd, Ag, and Au is 10 ppm or more relative to the total mass of the intermediate layer or the laminated polyethylene terephthalate film. [Item 6] The laminated polyethylene terephthalate film according to any one of Items 1 to 5, having a Si content of 2300 ppm or less relative to the total mass of the intermediate layer or the laminated polyethylene terephthalate film. [Item 7] The laminated polyethylene terephthalate film according to any one of Items 1 to 6, having a Ba content of 2300 ppm or less relative to the total mass of the intermediate layer or the laminated polyethylene terephthalate film. [Item 8] The laminated polyethylene terephthalate film according to any one of Items 1 to 7, wherein the intermediate layer contains 5% by mass or more and 100% by mass or less of a resin obtained by material recycling and / or chemical recycling of a film with a functional layer. [Item 9] The laminated polyethylene terephthalate film according to any one of Items 1 to 8, wherein the intrinsic viscosity (IV) of the intermediate layer or the intrinsic viscosity (IV) of the laminated polyethylene terephthalate film is 0.400 dL / g or more and 0.700 dL / g or less. [Item 10] The laminated polyethylene terephthalate film according to any one of Items 1 to 9, wherein the second coating layer contains lubricant particles. [Item 11] A release film comprising: the laminated polyethylene terephthalate film according to any one of Items 1 to 10; and the functional layer provided on the surface of the first coating layer provided on the laminated polyethylene terephthalate film, wherein the functional layer is a release layer. [Item 12] A method for producing the laminated polyethylene terephthalate film according to any one of Items 1 to 10, comprising the following steps: (Step 1) a pulverization step comprising pulverizing a polyethylene terephthalate film having a functional layer to form a pulverized product.(Step 2) a chipping step, which includes chipping the pulverized product to form recycled chips; (Step 3) a step of preparing at least the recycled chips and polyethylene terephthalate chips other than the recycled chips so that the total amount of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au elements is 0.1 ppm or more and 5000 ppm or less relative to the total mass of the intermediate layer or the total mass of the laminated polyethylene terephthalate film; and (Step 4) a recycled film formation step of melt-extruding the recycled chips and the polyethylene terephthalate chips to form a polyethylene terephthalate film that is an intermediate layer.

[0013] The following aspects of the present invention are also preferred. [Item 13] The laminated polyethylene terephthalate film, release film, or method for producing a laminated polyethylene terephthalate film according to any of the above items, wherein the polyester resin of the second coating layer is a polyethylene terephthalate resin. [Item 14] The laminated polyethylene terephthalate film, release film, or method for producing a laminated polyethylene terephthalate film according to any of the above items, wherein the intermediate layer contains Si. [Item 15] The laminated polyethylene terephthalate film, release film, or method for producing a laminated polyethylene terephthalate film according to any of the above items, wherein the intermediate layer contains Ti or Ba. [Item 16] The laminated polyethylene terephthalate film, release film, or method for producing a laminated polyethylene terephthalate film according to any of the above items, wherein the intermediate layer contains one or more of Ni, Cu, Pt, Pd, Ag, and Au, i.e., contains at least one element selected from the group consisting of Ni, Cu, Pt, Pd, Ag, and Au. [Item 17] The laminated polyethylene terephthalate film, release film, or method for producing a laminated polyethylene terephthalate film according to any of the above items, which satisfies both of the requirements (1) and (2). [Item 18] The laminated polyethylene terephthalate film, release film, or method for producing a laminated polyethylene terephthalate film according to any of the above items, wherein the first coating layer does not contain lubricant particles and / or the intermediate layer contains lubricant particles.

[0014] The present invention provides a laminated polyethylene terephthalate film capable of suppressing the transfer of a surface shape to a processed product, a method for producing the same, and a release film. The present invention provides a laminated polyethylene terephthalate film capable of suppressing the transfer of a surface shape to a processed product, even when using a recycled resin containing one or more of the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au.

[0015] The present invention will be described in detail below. A laminated polyethylene terephthalate film according to an embodiment of the present invention (hereinafter, sometimes simply referred to as the "laminated polyethylene terephthalate film of the present invention") includes a first coating layer (hereinafter, sometimes referred to as the "first coating layer A") containing a polyethylene terephthalate resin, an intermediate layer (hereinafter, sometimes referred to as the "intermediate layer C") containing a polyethylene terephthalate resin, and a second coating layer (hereinafter, sometimes referred to as the "second coating layer B") containing a polyester resin. The first coating layer has a surface on which a functional layer is laminated. The intermediate layer contains one or more of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au. The total amount of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au is 0.1 ppm or more and 5000 ppm or less relative to the total mass of the intermediate layer or the total mass of the laminated polyethylene terephthalate film.

[0016] The laminated polyethylene terephthalate film satisfies at least one of the following requirements (1) and (2). Here, it is preferable that the laminated polyethylene terephthalate film satisfies both of the following requirements (1) and (2). (1) The three-dimensional center plane average surface roughness (SRa) of the surface is 1 nm or more and 7.5 nm or less. (2) The maximum peak height (SRp) of the surface is 220 nm or less.

[0017] Because the intermediate layer of a laminated polyethylene terephthalate film contains one or more of the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au, it can be manufactured using recycled resin. Therefore, the present invention can contribute to reducing environmental impact. This is explained below. When the intermediate layer of a laminated polyethylene terephthalate film is manufactured using a resin recycled from a silicone-based release film, i.e., a film with a silicone-based release layer, the laminated polyethylene terephthalate film may contain Si elements derived from the silicone-based release layer. Furthermore, when the intermediate layer of a laminated polyethylene terephthalate film is manufactured using a resin recycled from a release film used in the manufacture of a multilayer ceramic capacitor containing barium titanate, the laminated polyethylene terephthalate film may contain Ti and Ba elements derived from the barium titanate remaining in the release film. Similarly, when the intermediate layer of a laminated polyethylene terephthalate film is manufactured using a resin recycled from a release film used in the manufacture of a multilayer ceramic capacitor, the laminated polyethylene terephthalate film may contain electrode components of the multilayer ceramic capacitor remaining in the release film. This is thought to be because, during the production of a multilayer ceramic capacitor, electrodes are printed on a ceramic green sheet formed on a release film and then wound up, causing electrode components to adhere to the release film during this winding process. The electrode components include one or more of Ni, Cu, Pt, Pd, Ag, and Au. Thus, when an intermediate layer of a laminated polyethylene terephthalate film is produced using recycled resin, the laminated polyethylene terephthalate film may contain one or more of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au. The laminated polyethylene terephthalate film of the present invention is permitted to contain a certain amount of these elements. Therefore, the laminated polyethylene terephthalate film of the present invention is permitted to be produced using recycled resin containing these elements.Therefore, the laminated polyethylene terephthalate film of the present invention can contribute to reducing environmental impact. Although the laminated polyethylene terephthalate film of the present invention is preferably produced using recycled resin, it may also be produced without using recycled resin. Furthermore, since the upper limit for the total amount of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au is 5000 ppm, recycled resins that can be used to produce laminated polyethylene terephthalate films may contain certain amounts of these elements. In other words, recycled resins that can be used to produce laminated polyethylene terephthalate films are permitted to contain certain amounts of these elements. Therefore, the recycling yield (see Patent Document 1), specifically, the recycling yield of recycled resins that can be used to produce laminated polyethylene terephthalate films, can be improved. Furthermore, since the three-dimensional center plane average surface roughness (SRa) of the first coating layer A is 7.5 nm or less, or the maximum peak height (SRp) is 220 nm or less, the formation of excessive irregularities on the surface of a processed product (hereinafter sometimes referred to as a "molded product") manufactured using the laminated polyethylene terephthalate film can be avoided. For example, when a ceramic green sheet is manufactured using a release film containing a laminated polyethylene terephthalate film and a release layer, the formation of excessive irregularities on the surface of the ceramic green sheet can be avoided. In other words, the transfer of the surface shape to the ceramic green sheet can be suppressed.

[0018] In one embodiment, the intermediate layer of the laminated polyethylene terephthalate film of the present invention can contain 5% by mass or more and 100% by mass or less of a resin recycled from a film with a functional layer. Here, the "film with a functional layer" includes a substrate film and a functional layer. When the functional layer is a release layer, the film with a functional layer may be referred to as a "release film." In this specification, material recycling and / or chemical recycling may also be simply referred to as recycling.

[0019] The following mainly describes a laminated polyethylene terephthalate film for use in release films (typically as a base film for release films), but the laminated polyethylene terephthalate film is not limited to release film applications. The following mainly describes a laminated polyethylene terephthalate film as a biaxially stretched laminated polyethylene terephthalate film, i.e., a biaxially oriented laminated polyethylene terephthalate film, but the laminated polyethylene terephthalate film is not limited to biaxially oriented laminated polyethylene terephthalate films. The following mainly describes the elemental content (e.g., the total amount of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au, or the content of each element) based on the total mass of the intermediate layer or the laminated polyethylene terephthalate film. The elemental content may be within the preferred range described below, both relative to the total mass of the intermediate layer and the total mass of the laminated polyethylene terephthalate film. Although the following description will mainly focus on a configuration in which the second coating layer of the laminated polyethylene terephthalate film contains a polyethylene terephthalate resin, the second coating layer is not limited to a configuration containing a polyethylene terephthalate resin. Resins for the second coating layer include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polycyclohexanedimethanol terephthalate, among others, without any particular restrictions. Among these, polyethylene terephthalate, i.e., polyethylene terephthalate resin, is preferred.

[0020] The resin for each layer of the laminated polyethylene terephthalate film may be a single material or a mixed material such as a polymer alloy.

[0021] In one embodiment, the laminated polyethylene terephthalate film of the present invention contains a resin recycled from a film with a functional layer. The film with a functional layer may be a used film with a functional layer. The film with a functional layer may be a release film, for example, a used release film. A used release film refers to a release film obtained after, for example, forming and laminating an object to be released on a release layer and then peeling the object from the release layer. In addition, used release films may include release films that have not been used and stored for a long time after production, release films that have not been used because they do not satisfy the required properties, and release films that do not achieve their original purpose, such as cut edges.

[0022] In one embodiment, the recycled functional layer-equipped film, i.e., the functional layer-equipped film used as a raw material for recycled resin, is a release film used to mold a resin sheet containing an inorganic compound. Examples of inorganic compounds include metal particles, metal oxides, and minerals, such as calcium carbonate, silica particles, aluminum particles, and barium titanate particles. Examples of resins contained in the resin sheet include polyvinyl acetal resin and poly(meth)acrylic ester resin. For example, the functional layer-equipped film is used in the manufacture of resin sheets that require high smoothness, such as semiconductor components, ceramic green sheets, and optical films. By recycling laminated films used for such applications, various physical properties, such as surface roughness, can be more effectively achieved. Furthermore, functional layer-equipped films (e.g., release films) used for such applications preferably contain particles to maintain smoothness and exhibit windability. For example, the functional layer can contain resins such as silicone-based, cyclic olefin-based, acyclic olefin-based, fluorine-based, alkyd-based, acrylic, melamine-based, and epoxy-based resins, as described below.

[0023] The film with a functional layer to be recycled is a film in which a functional layer is provided on at least one surface of a base film containing a thermoplastic resin. The base film is preferably a polyester film, and may be, for example, the laminated polyethylene terephthalate film of the present invention. This allows the laminated polyethylene terephthalate film or release film of the present invention to be recycled and reused multiple times, making it suitable for the efficient use of resources required in a recycling-oriented society.

[0024] In the present invention, components other than the polyester component can also be recycled as long as they do not deviate from the scope of the present invention. There are no particular limitations on the materials, etc., as long as they are within the scope of the present invention.

[0025] Particularly preferably, resin recycled from a functional layer-attached film in which a functional layer is laminated directly on a substrate film can be used. By using a functional layer-attached film in which a functional layer is laminated directly on a substrate film, a functional layer-attached film with fewer impurities can be recycled, which makes it possible to further reduce the surface roughness of the laminated polyethylene terephthalate film and also reduce haze. Examples of the material of the substrate film of the functional layer-attached film to be recycled include polyethylene terephthalate. Examples of polyethylene terephthalate include homopolyethylene terephthalate and copolymer polyethylene terephthalate.

[0026] The laminated polyethylene terephthalate film of the present invention preferably contains particles. For example, it can contain one or more types of inorganic or organic particles. The particles can function as a lubricant. Examples of particles include inorganic particles such as titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, and calcium fluoride, as well as organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based particles. Two or more types of particles may be contained. Examples of inorganic particles include alumina-silica composite oxide particles and hydroxyapatite particles. Examples of organic particles, particularly heat-resistant organic particles, include crosslinked polyacrylic particles, crosslinked polystyrene particles, and benzoguanamine-based particles.

[0027] As the particles, it is more preferable to use silica particles and / or calcium carbonate particles from the viewpoints of transparency and cost. As the silica particles, porous colloidal silica is preferable. When calcium carbonate particles are used, light calcium carbonate that has been surface-treated with a polyacrylic acid-based polymer compound is preferable from the viewpoint of preventing the lubricant particles from falling off. The particle content is preferably 100 to 10,000 ppm, more preferably 300 to 8,000 ppm, based on the total mass of the laminated polyethylene terephthalate film. 500 ppm or more is also preferable. A content of 100 ppm or more is preferable because it provides good handleability. A content of 10,000 ppm or less can further prevent excessive unevenness from being formed on the surface of the processed product (for example, a ceramic green sheet).

[0028] In one embodiment, the raw material for the laminated polyethylene terephthalate film of the present invention may be a resin composition, such as a polyester resin composition, obtained by recycling at least the substrate film of a functional layer-equipped film. The average particle diameter of the particles contained in the polyester resin composition is preferably 0.2 μm or more and 5.0 μm or less, and more preferably 0.4 μm or more and 5.0 μm or less. When the average particle diameter is 0.2 μm or more, air can be uniformly released when the film is wound into a roll, both in production and use, resulting in a good wound appearance and good flatness, making it suitable for the production of ultra-thin ceramic green sheets (hereinafter referred to as "good handleability"). When the average particle diameter is 5.0 μm or less, surface irregularities are reduced, further preventing excessive irregularities from forming on the surface of the processed product (e.g., ceramic green sheet). The average particle diameter of the particles may be 4.0 μm or less, 3.0 μm or less, 2.0 μm or less, 1.5 μm or less, or 1.0 μm or less. The particles may function as a lubricant. The average particle size of the particles can be measured by the method described in the Examples. The shape of the particles is not particularly limited, and spherical particles or irregular, non-spherical particles can be used as long as the object of the present invention is met. The particle size of irregular particles can be calculated as the equivalent circle diameter. The equivalent circle diameter is calculated by dividing the area of ​​the observed particle by pi (π), calculating the square root, and then multiplying it by two.

[0029] The second coating layer B preferably contains lubricant particles. The length of the longest side of the lubricant particles is preferably, for example, 0.5 μm or more and 5.0 μm or less. As may have been mentioned previously, the lubricant particles may be, for example, calcium carbonate particles CaCO ３Alternatively, it is preferable that the lubricant particles are at least one type of particles selected from silica particles SiO2. From the viewpoint of the film's slipperiness and ease of air escape, the content of the lubricant particles in the second coating layer B is preferably 100 ppm or more and 10,000 ppm or less, more preferably 300 ppm or more and 8,000 ppm or less, relative to the total mass of the second coating layer. When the content is 100 ppm or more, handling is favorable, which is preferable. When the content is 10,000 ppm or less, excessive unevenness on the surface of the processed product (for example, a ceramic green sheet) due to the protrusion of the surface of the second coating layer can be further prevented. Here, calcium carbonate particles CaCO ３ The content of calcium carbonate particles CaCO ３ The content can be calculated.

[0030] The laminated polyethylene terephthalate film of the present invention may be a biaxially stretched laminated polyethylene terephthalate film. The intrinsic viscosity (IV) of the laminated polyethylene terephthalate film of the present invention is preferably 0.400 dl / g or more and 0.700 dl / g or less, more preferably 0.500 dl / g or more and 0.700 dl / g or less, and for example, 0.510 dl / g or more and 0.650 dl / g or more and 0.510 dl / g or more and 0.620 dl / g or less is even more preferable. It is particularly preferably 0.510 dl / g or more and 0.580 dl / g or less. The preferred range of the intrinsic viscosity of the intermediate layer C is omitted here, as it overlaps with the description of the laminated polyethylene terephthalate film. An intrinsic viscosity of 0.500 dl / g or more is preferable because breakage is less likely to occur during the stretching process. Furthermore, biaxial stretching is possible without impairing film formability. Furthermore, when the viscosity is 0.700 dl / g or less, the cutting property is good when cutting to a predetermined product width, and dimensional defects do not occur, which is preferable. In addition, the filter filtration pressure can be suppressed, so there is no problem with operability. It is preferable to thoroughly vacuum dry the raw material.

[0031] The laminated polyethylene terephthalate film of the present invention desirably exhibits the above-mentioned intrinsic viscosity even in an embodiment in which the film is obtained by forming recycled chips into a film. In one embodiment, the film contains 5% by mass or more and 100% by mass or less of a resin recycled from a functional layer-equipped film containing one or more types of inorganic particles or organic particles. The intrinsic viscosity (IV) of the laminated polyethylene terephthalate film of the present invention is preferably 0.50 dl / g or more and 0.70 dl / g or less, more preferably 0.51 dl / g or more and 0.58 dl / g or less.

[0032] The thickness of the laminated polyethylene terephthalate film is preferably 12 to 100 μm, more preferably 12 to 85 μm, and even more preferably 15 to 80 μm. A film thickness of 12 μm or more is preferable because there is no risk of deformation due to heat during film production or use as a process film. On the other hand, a laminated polyethylene terephthalate film having a thickness of 100 μm or less is preferable from the viewpoint of reducing the environmental impact by not excessively increasing the amount of film discarded after use, and is also preferable from an economic viewpoint because it reduces the amount of material per area of ​​the release film used. In one embodiment, the thickness ratio of the first coating layer A is 30% to 50% of the total layer. That is, the thickness of the first coating layer A is preferably 30% to 50% of the total thickness of the laminated polyethylene terephthalate film (100%). The laminated polyethylene terephthalate film of the present invention has a first coating layer A, an intermediate layer C, and a second coating layer B. The intermediate layer C may be disposed between the first coating layer A and the second coating layer B. The intermediate layer C may have a multi-layer structure. The intermediate layer C contains one or more of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au. At least one of the first coating layer A and the second coating layer B may also contain one or more of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au. All layers may contain one or more of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au. In one embodiment, the layer structure in the thickness direction may be an A / C / B layer structure. In one embodiment, the thickness of the intermediate layer C may be 30% to 50% of the 100% thickness of the laminated polyethylene terephthalate film.

[0033] Next, the thickness of the first coating layer A is preferably 7.0 μm or more and 20.0 μm or less. Here, the longest side length of particles derived from electrode components, such as Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au particles, is often, for example, 0.1 μm or more and 5.0 μm or less. The lower limit of the thickness of the first coating layer A is more preferably 8.6 μm, and even more preferably 9.0 μm. The upper limit of the thickness of the first coating layer A is more preferably 17.0 μm, and even more preferably 15.0 μm. When the thickness of the first coating layer A is 7.0 μm or more, these particles on the surface of the intermediate layer C can be prevented from penetrating the first coating layer A and becoming exposed from the surface of the first coating layer A, and the protrusion of the surface of the first coating layer A due to these particles on the surface of the intermediate layer C can be significantly suppressed. On the other hand, when the thickness of the first coating layer A is 0.5 μm or more, the first coating layer A can prevent these particles contained in the intermediate layer C from falling off. Taking this into consideration, the thickness of the first coating layer A is preferably 7.0 μm or more.

[0034] It is preferable that the first coating layer A does not substantially contain particles having a particle size of 1.0 μm or more, for example, inorganic particles having a particle size of 1.0 μm or more. It is more preferable that the first coating layer A does not contain particles having an average particle size of 1.0 μm or more.

[0035] In this embodiment, particles having a particle size of less than 1.0 μm and equal to or greater than 1 nm may be present in the first coating layer A. Since the first coating layer A does not substantially contain particles having a particle size of 1.0 μm or greater, such as inorganic particles, it is possible to reduce the possibility of defects occurring due to the particle shape in the laminated polyethylene terephthalate film being transferred to the resin sheet (for example, a ceramic green sheet).

[0036] In one embodiment, the first coating layer A does not contain particles with a particle size of less than 1.0 μm, thereby more effectively preventing defects caused by the transfer of particle shapes in the laminated polyethylene terephthalate film to the resin sheet. In other words, it is preferable that the first coating layer A not only does not substantially contain particles with a particle size of 1.0 μm or more, but also does not substantially contain particles with a particle size of less than 1.0 μm and 1 nm or more. It is more preferable that the first coating layer A does not contain particles with a particle size of 1.0 μm or more, or particles with a particle size of less than 1.0 μm and 1 nm or more.

[0037] In the present invention, "substantially free of particles" means, for example, in the case of inorganic particles less than 1.0 μm in size, that the content of inorganic elements quantified is 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit. This is because even if particles are not actively added to the film, contaminants from foreign substances or dirt adhering to the raw resin or the production line or equipment during the film manufacturing process may detach and be mixed into the film. Furthermore, "substantially free of particles with a particle size of 1.0 μm or more" means that particles with a particle size of 1.0 μm or more are not actively contained. Inorganic elements can be quantified, for example, by fluorescent X-ray analysis or ICP atomic emission spectroscopy. ICP stands for inductively coupled plasma.

[0038] In one embodiment, it is preferable that the first coating layer A does not contain particles such as lubricants and does not use recycled raw materials, as this can more effectively reduce surface roughness.

[0039] The surface of the first coating layer A is the surface on which the functional layer is laminated. The three-dimensional center plane average surface roughness (SRa) of this surface is preferably 1 nm or more and 7.5 nm or less, more preferably 1 nm or more and 7 nm or less. Furthermore, the maximum peak height (SRp) of this surface is preferably 220 nm or less, more preferably 200 nm or less. From the viewpoint of manufacturing costs, the maximum peak height (SRp) is preferably 5 nm or more, more preferably 10 nm or more. By having such three-dimensional center plane average surface roughness and maximum peak height, the present invention can suppress surface irregularities and inhibit the transfer of irregularities to processed products. Preferably, the average surface roughness (SRa) of the first coating layer A is 1.5 nm or more and 6.5 nm or less, for example, 2.0 nm or more and 6.0 nm or less. By having the average surface roughness (SRa) of the first coating layer A within the above range, high smoothness can be achieved for the functional layer laminated on the first coating layer A, such as a release layer. For example, by controlling the amounts of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au present in the intermediate layer C, the three-dimensional center plane average surface roughness (SRa) and maximum peak height (SRp) of the first coating layer A can be set within the range of the present invention. Meanwhile, the three-dimensional center plane average surface roughness (SRa) of the second coating layer B may be 20 nm or more and 40 nm or less. The second coating layer B may also exhibit a maximum peak height (SRp) within the above range. That is, the maximum peak height (SRp) of the second coating layer B may be, for example, 220 nm or less. In one embodiment, at least one of the three-dimensional center plane average surface roughness (SRa) and maximum peak height (SRp) exhibits a different numerical range between the first coating layer A and the second coating layer B. Thus, the three-dimensional center plane average surface roughness (SRa) of the first coating layer A may differ from that of the second coating layer B. The maximum peak height (SRp) of the first coating layer A may be different from that of the second coating layer B. When the SRa of the first coating layer A is 1 nm or more, air can be uniformly released when the film is wound into a roll, resulting in a good roll shape and flatness, making the film suitable for producing ultra-thin ceramic green sheets.When the SRa of the first coating layer A is 7.5 nm or less, the surface irregularities can be suppressed and the transfer of the irregularities to the molded product can be prevented.

[0040] The first coating layer A preferably has a maximum peak height (SRp) of 220 nm or less. In one embodiment, the first coating layer A more preferably has a maximum peak height (SRp) of 200 nm or less, and even more preferably has a maximum peak height (SRp) of 180 nm or less. By having a maximum peak height (SRp) of 220 nm or less, surface irregularities are reduced, and transfer to a processed product can be suppressed.

[0041] The intermediate layer C is a layer in which the first coating layer A is laminated on one side and the second coating layer B is laminated on the other side. The intermediate layer C contains one or more of the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au. Furthermore, particles may be added as appropriate to control the surface shape. In other words, the intermediate layer C may contain added particles.

[0042] The laminated polyethylene terephthalate film can be produced using raw materials recycled from, for example, a film with a functional layer. For example, the intermediate layer C can be produced using raw materials recycled from a film with a functional layer. The intermediate layer C can contain one or more of the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au. The total amount of these elements can be 0.1 ppm or more relative to the total mass of the intermediate layer C or the total mass of the laminated polyethylene terephthalate film.

[0043] The laminated polyethylene terephthalate film preferably contains one or more of the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au, and the total amount of these elements is preferably 0.1 ppm to 5000 ppm relative to the total mass of the intermediate layer C or the total mass of the laminated polyethylene terephthalate film. Having the total content of these elements within the above ranges improves the handleability of the laminated polyethylene terephthalate film, and also reduces the unevenness of the film surface, thereby preventing the transfer of unevenness to processed products. Conventional recycled films tend to actively remove the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au. In contrast, in the present invention, the total amount of these elements is a predetermined amount, thereby maintaining the handleability of the laminated polyethylene terephthalate film, and further reducing the unevenness of the film surface, thereby further preventing the transfer of unevenness to molded products. In one embodiment, the film surface irregularities can be suppressed to the order of several nanometers to several tens of nanometers, thereby imparting good processability and releasability to the release film even when used to mold extremely thin ceramic green sheets. Furthermore, the laminated polyethylene terephthalate film of the present invention exhibits mechanical properties, such as tensile strength and modulus of elasticity, comparable to or superior to those of films formed from virgin materials containing no recycled resin. Thus, by ensuring that the total amount of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au is a predetermined amount, the laminated polyethylene terephthalate film can exhibit high recyclability while improving various physical properties. The total amount of these elements may be, for example, 0.5 ppm or more, 1.0 ppm or more, or 10 ppm or more relative to the total mass of the intermediate layer C or the total mass of the laminated polyethylene terephthalate film. The total amount of these elements may be, for example, 3000 ppm or less, or 1000 ppm or less.

[0044] When the first coating layer A is substantially free of particles containing one or more of the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au, the first coating layer A not only has high surface smoothness but also exhibits high adhesion to the functional layer.

[0045] The total amount of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au elements in the intermediate layer C is preferably 80 parts by mass or more, more preferably 90 parts by mass or more, more preferably 95 parts by mass or more, even more preferably 98 parts by mass or more, and even more preferably 100 parts by mass, per 100 parts by mass of the total amount of these elements in the laminated polyethylene terephthalate film.

[0046] In one embodiment, the Si element content in the intermediate layer C or the laminated polyethylene terephthalate film is preferably 0.1 ppm or more and 2300 ppm or less. The Si element content may be, for example, 2000 ppm or less, 1500 ppm or less, 1000 ppm or less, or 500 ppm or less. The Si element content may be 0.3 ppm or more. When the Si element content is within the above range, for example, the handleability of the laminated polyethylene terephthalate film is improved, and furthermore, unevenness on the film surface can be further suppressed, thereby further preventing the transfer of unevenness to the molded product. In addition, heat resistance is also improved.

[0047] In conventional technology, when a film with a functional layer, specifically a release film, is recycled, it is necessary to almost completely remove the silicone component present on the surface of the base film.

[0048] The content of Ba in the intermediate layer C or the laminated polyethylene terephthalate film is preferably 0.1 ppm or more and 2300 ppm or less, for example, 1700 ppm or less, or 1000 ppm or less. The preferred contents of Ti, Ni, Cu, Pt, Pd, Ag, and Au in the intermediate layer C or the laminated polyethylene terephthalate film are similar to those of Ba. That is, each content is preferably 0.1 ppm or more and 2300 ppm or less, for example, 1700 ppm or less, or 1000 ppm or less. In another embodiment, the upper limit may be 500 ppm or less. Conventional recycled films involve completely separating the ceramic green sheet component residue, release layer component, electrode member, and substrate film, and using only the high-purity polyester resin. On the other hand, in the present invention, the total amount of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au elements must be within the range of the present invention, and the residue of the ceramic green sheet components, the release layer components, and the base film can be recycled and reused within the range of the composition of the present invention. Therefore, in the present invention, for example, the material recycling process of the resin obtained by material recycling a film with a functional layer, specifically a release film, can be simplified and shortened compared to conventional methods, and more efficient recycling with reduced waste can be promoted.

[0049] The intermediate layer C preferably contains one or more of Ti, Ni, Cu, Pt, Pd, Ag, and Au. This reduces the melt resistivity of the laminated polyethylene terephthalate film at 275°C, thereby improving electrostatic adhesion. The total amount of Ti, Ni, Cu, Pt, Pd, Ag, and Au is preferably 10 ppm or more, more preferably 50 ppm or more, and even more preferably 100 ppm or more, based on the total mass of the intermediate layer C or the total mass of the laminated polyethylene terephthalate film. This total amount may be 5,000 ppm or less, 2,000 ppm or less, or 200 ppm or less.

[0050] The intermediate layer C preferably contains one or more of Ni, Cu, Pt, Pd, Ag, and Au. This reduces the melt resistivity of the laminated polyethylene terephthalate film at 275°C, thereby improving electrostatic adhesion. The total amount of Ni, Cu, Pt, Pd, Ag, and Au may be 1 ppm or more, 5 ppm or more, 10 ppm or more, or 20 ppm or more relative to the total mass of the intermediate layer C or the laminated polyethylene terephthalate film. This total amount may be 200 ppm or less, 150 ppm or less, 100 ppm or less, or 80 ppm or less.

[0051] The intermediate layer C preferably contains one or more of Ni, Cu, Pt, Pd, Ag, and Au, and Ti, which can further reduce the melt resistivity of the laminated polyethylene terephthalate film at 275°C and thus further improve the electrostatic adhesion.

[0052] The intermediate layer C preferably contains at least one of Ni, Cu, Pt, Pd, Ag, and Au elements, as well as Ti, Ba, and Si elements.

[0053] In one embodiment, the melt resistivity (ρi(10 8 The melt resistivity (Ω·cm) is preferably 1.00 or less, more preferably 0.20 or less. When the melt resistivity is 1.00 or less, the laminated polyethylene terephthalate film of the present invention can have excellent electrostatic adhesion. That is, when the melt resistivity is 1.00 or less, the laminated polyethylene terephthalate film of the present invention can have excellent film-forming properties and a high yield.

[0054] In one embodiment, the laminated polyethylene terephthalate film of the present invention contains a material-recycled resin (also referred to as a material-recycled raw material) in an amount of 5% by mass to 100% by mass, based on 100% by mass of the laminated polyethylene terephthalate film. For example, the material-recycled raw material may be contained in an amount of 8% by mass to 47% by mass, e.g., 10% by mass to 45% by mass. By containing 5% by mass to 100% by mass, the amount of petroleum-derived raw materials used can be reduced, making the film environmentally friendly. The material-recycled raw material may be a resin obtained by material recycling a film with a functional layer, specifically a release film. Alternatively, the material may be a resin obtained by material recycling a release film that has been used and is to be discarded. For example, when the first coating layer A has a two-layer structure, the material-recycled raw material contained in the first coating layer A can be appropriately blended so that the total amount of the material-recycled raw material in the two layers is 5% by mass to 100% by mass. Similarly, for example, when the intermediate layer C has a multi-layer structure, the recycled material contained in the intermediate layer C can be appropriately blended so that the total in each layer forming the intermediate layer C is 5% by mass or more and 100% by mass or less.

[0055] In one embodiment, the second coating layer B of the laminated polyethylene terephthalate film contains calcium carbonate particles CaCO ３ Alternatively, silica particles SiO2 are included. These particles have a longest side length of 0.5 μm or more and 5.0 μm or less.

[0056] The functional layer of a recycled functional layer-attached film (i.e., a functional layer-attached film used as a raw material for recycled resin) is not particularly limited and may contain resins such as silicone-based, cyclic olefin-based, acyclic olefin-based, fluorine-based, alkyd-based, acrylic-based, melamine-based, and epoxy-based resins. Preferably, the functional layer contains a silicone-based, acrylic-based, or melamine-based resin. By including these resins in the functional layer, the adhesion between the first coating layer A and the second coating layer B in the laminated polyethylene terephthalate film can be improved. In one embodiment, the adhesion between the intermediate layer C and the first coating layer A and the second coating layer B can be improved, resulting in a release laminated polyethylene terephthalate film with high smoothness. Examples of functional layers include an easy-adhesion layer, an antistatic layer, a release layer, and an adhesive layer. Of these, a release layer is preferred, and a silicone release layer is more preferred. In particular, when the functional layer is used as a release layer, residues of the processed product may be present on the surface of the release layer. For this reason, when producing the laminated polyethylene terephthalate film of the present invention, a removal step may be performed, including removing adhesions from the functional layer-attached film (details will be described later). Furthermore, release layers are also required to have high adhesion to the object to be released. For example, release layers for pressure-sensitive adhesives, optical films, and ceramic green sheets can be used in the manufacturing process of the object to be released and the manufacturing process of the device using the same, and therefore must exhibit high adhesion between these processes. Furthermore, the release layer may be a release layer that has been exposed to high temperature (e.g., 60°C or higher) and / or high humidity (e.g., 70% or higher) conditions, or a release layer that has been subjected to high stretching conditions. The removal step, including removing adhesions from the functional layer-attached film subjected to these conditions, can increase the purity of the recycled resin and provide, for example, the required optical properties, mechanical strength, etc.

[0057] The silicone-based compound is a compound having a silicone structure in the molecule, and examples thereof include cured silicone, silicone graft resin, and modified silicone resin such as alkyl-modified silicone resin.

[0058] As an example, the present invention provides a method for producing a laminated polyethylene terephthalate film. The production method includes the following steps: (Step 1) a pulverization step, which includes pulverizing a film with a functional layer to form a pulverized product; (Step 2) a chipping step, which includes chipping the pulverized product to form recycled chips; (Step 3) a step of preparing at least recycled chips and polyethylene terephthalate chips other than the recycled chips, such that the total amount of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au is 0.1 ppm or more and 5000 ppm or less relative to the total mass of the intermediate layer C or the laminated polyethylene terephthalate film; and (Step 4) a recycled film formation step, which includes melt-extruding the recycled chips and the polyethylene terephthalate chips to form a polyethylene terephthalate film serving as an intermediate layer. Here, the recycled film formation step may be a step of melt-extruding a molding material for forming an intermediate layer, which includes recycled chips and polyethylene terephthalate chips, to obtain a laminated polyethylene terephthalate film. In the present invention, by including steps 1 to 4, a laminated polyethylene terephthalate film can be obtained without impairing physical properties, even if the step of removing deposits from the surface of the functional layer-equipped film is not included. The method for producing a laminated polyethylene terephthalate film may further include a step of removing deposits from the functional layer-equipped film (hereinafter, sometimes referred to as "step 0"). The method for producing a laminated polyethylene terephthalate film preferably includes step 0. An example of a method for producing a laminated polyethylene terephthalate film will be described in detail below.

[0059] (Step 0: Step of Removing Adherents from Functional Layer-Equipped Film) A functional layer-equipped film to be recycled (i.e., a functional layer-equipped film as a raw material for recycled resin) has a functional layer provided on at least one surface of a substrate film. That is, a functional layer-equipped film includes a substrate film and a functional layer provided on at least one surface of the substrate film. After use of a functional layer-equipped film, adhering matter may remain on the surface of the functional layer-equipped film, for example, the surface of the functional layer or the surface of the substrate film. Furthermore, with regard to functional layer-equipped films, used functional layer-equipped films, functional layer-equipped films that do not meet specifications, functional layer-equipped films that have been damaged during distribution, etc. are usually discarded. It is desirable to perform a step of removing adhering matter from such films to be discarded (i.e., functional layer-equipped films to be discarded) as long as it does not impair the final physical properties of the film. Furthermore, depending on the condition of the adhering matter, the step of removing the adhering matter may be omitted.

[0060] The method for removing deposits from the film with functional layers is not particularly limited. For example, there are methods for removing deposits by attaching an adhesive roll and peeling off the adhesive roll, removing deposits by suction with a vacuum, scraping off deposits with a blade, removing deposits with high-pressure water or high-pressure air, removing deposits by spraying with sand or dry ice, immersing the film with functional layers in a cleaning layer and removing deposits by adsorbing them with microbubbles or the like, floating and removing deposits by micro-vibrations such as ultrasonic waves, and removing deposits by using supercritical CO ２ Examples of such methods include a method of dissolving and removing the deposits by a method using a solvent such as a fluorine-containing solvent. These methods may also be combined. These methods are not particularly limited, but from the standpoint of efficiency, a method that allows roll-to-roll processing is preferred. In this step, some of the functional layer may be removed together with the deposits, or the functional layer may remain on the substrate film without being removed.

[0061] (Step 1: Pulverizing the Film) In step 1, the film with functional layers is pulverized to form a pulverized product. Examples of methods for pulverizing the film with functional layers include pulverizing the film with functional layers itself, and separating the film with functional layers into the functional layer and the base film and then pulverizing them separately or together. Among these, the method of pulverizing the film with functional layers itself is preferred. In the method of separating the film with functional layers into the functional layer and the base film and then pulverizing them separately, the pulverized product of the functional layer and the pulverized product of the base film may or may not be mixed to obtain a pulverized product for producing recycled chips. If not mixed, the pulverized product for producing recycled chips may be a pulverized product of the base film or a pulverized product of the functional layer. The film with functional layers can be pulverized using a pulverizer such as a single-axis pulverizer, a biaxial pulverizer, a triaxial pulverizer, or a cutter mill. Examples of the shape of the pulverized product include flakes, powder, lumps, and strips. Among these, flakes are preferred.

[0062] As described above, the pulverization process can be performed without removing any attachments from the surface of the functional layer-equipped film. Therefore, for example, attachments such as adhesive, ceramic green sheets, and impurities may be present on the surface of the functional layer. Furthermore, some of these attachments may be removed before the pulverization process. By partially removing the attachments, it becomes easier to control the content of the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au. In other words, the manufacturing method according to an embodiment of the present invention does not require complete removal of attachments such as adhesive, ceramic green sheets, and impurities present on the surface of the functional layer, as in conventional recycling techniques. The manufacturing method according to an embodiment of the present invention does not require removal of the functional layer itself; instead, some of the attachments may be removed to control the content of the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au. The manufacturing method according to an embodiment of the present invention can directly subject the functional layer and the substrate film, even if such attachments are present, to the pulverization process. Therefore, compared to conventional recycling techniques, the number of steps and time required for producing resin pellets and forming them into a film can be significantly reduced. Furthermore, the amount of waste can be reduced.

[0063] (Step 2: Manufacturing Recycled Chips) The method for manufacturing recycled chips preferably involves granulating the pulverized product by melt extrusion. Examples of granulation devices include single-screw extruders, twin-screw extruders, and multi-screw extruders. Twin-screw or multi-screw extruders are preferred, as they combine control of mixing intensity and suppress resin degradation. To remove coarse foreign matter, the pulverized product may be passed through a filter between molten state and extrusion. As described above, the intermediate layer C contains one or more of the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au. Furthermore, the total amount of these elements is 0.1 ppm or more and 5000 ppm or less relative to the total mass of the intermediate layer C or the total mass of the laminated polyethylene terephthalate film. It should be noted that the manufacturing method according to an embodiment of the present invention does not require complete removal of the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au. The recycled chips are preferably in the form of pellets.

[0064] (Step 3: Preparing Recycled Chips and Polyethylene Terephthalate Chips) In step 3, it is preferable to prepare at least recycled chips and polyethylene terephthalate chips so that the total amount of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au elements is 0.1 ppm or more and 5000 ppm or less relative to the total mass of the intermediate layer C or the total mass of the laminated polyethylene terephthalate film. The polyethylene terephthalate chips are preferably in the form of pellets. Examples of polyethylene terephthalate in the polyethylene terephthalate chips include homopolyethylene terephthalate and copolymerized polyethylene terephthalate. Of these, homopolyethylene terephthalate is preferred. The description of the polyethylene terephthalate in the polyethylene terephthalate chips will be omitted as it overlaps with the description of the polyethylene terephthalate in the functional layer-attached film to be recycled. The polyethylene terephthalate chips may contain particles. The description of the particles in the polyethylene terephthalate chips will be omitted as it overlaps with the description of the particles in the laminated polyethylene terephthalate film. The polyethylene terephthalate chips may contain additives. Examples of the additives include an antioxidant, a light stabilizer, an ultraviolet absorber, and a crystallizing agent. In step 3, additional polyethylene terephthalate chips may be further prepared.

[0065] In step 3, it is preferable to mix at least recycled chips and polyethylene terephthalate chips, thereby obtaining mixed chips containing recycled chips and polyethylene terephthalate chips.

[0066] (Step 4: Step of Producing a Film) In step 4, a molding material for forming the intermediate layer C is melt-extruded to obtain a laminated polyethylene terephthalate film. The molding material for forming the intermediate layer C contains recycled chips and polyethylene terephthalate chips. In step 4, it is preferable to melt-extrude a mixed chip containing recycled chips and polyethylene terephthalate chips as the molding material for forming the intermediate layer C to obtain a laminated polyethylene terephthalate film.

[0067] The film-forming method is not limited, but specifically, recycled chips and polyethylene terephthalate chips are thoroughly vacuum-dried and mixed, and then the mixed chips are fed into an extruder as a molding material for forming the intermediate layer C, melt-extruded into a sheet at approximately 255 to 280°C, and cooled and solidified to form an unstretched polyethylene terephthalate sheet. The resulting unstretched polyethylene terephthalate sheet is stretched 3.0 to 6.0 times in the longitudinal direction using rolls heated to 75 to 140°C to obtain a uniaxially oriented polyethylene terephthalate film. The end of the uniaxially oriented polyethylene terephthalate film is then gripped with clips and introduced into a hot air zone heated to 75 to 140°C, where it is dried and then stretched 3.0 to 6.0 times in the width direction. Subsequently, the film is introduced into a heat-setting zone at 180 to 260°C, where it can be heat-treated for 1 to 60 seconds. During this heat-treatment process, if necessary, a relaxation treatment of 0 to 10% may be performed in the width or longitudinal direction. In order to remove large foreign objects, the recycled chips may be passed through a filter between the time they are melted and the time they are extruded. The finer the mesh of the filter, the more small the foreign objects that can be removed.

[0068] In step 4, the molding material for forming the intermediate layer C (i.e., a mixed chip containing recycled chips and polyethylene terephthalate chips), the molding material for forming the first coating layer A (e.g., polyethylene terephthalate chips), and the molding material for forming the second coating layer B (e.g., a mixed chip containing polyethylene terephthalate chips or recycled chips and particle-containing polyethylene terephthalate chips) are co-extruded, and the unstretched laminated polyethylene terephthalate sheet is biaxially stretched and heat-set as necessary to obtain a biaxially oriented laminated polyethylene terephthalate film. The description of the polyethylene terephthalate chips for forming the first coating layer A and the polyethylene terephthalate chips for forming the second coating layer B will be omitted as they overlap with the description of the polyethylene terephthalate chips for forming the intermediate layer C. Note that the molding material for forming the first coating layer A preferably does not contain recycled chips. The description of the recycled chips for forming the second coating layer B will be omitted as they overlap with the description of the recycled chips for forming the intermediate layer C. Note that the molding material for forming the second coating layer B may or may not contain recycled chips.

[0069] As a result, a laminated polyethylene terephthalate film containing a resin obtained by material recycling of a film with a functional layer can be obtained.

[0070] (Resin Sheet) In one embodiment, the laminated polyethylene terephthalate film of the present invention can be used as a substrate film in a release film for molding a resin sheet. The resin sheet is not particularly limited, and may be used in the production of adhesives and optical films. In one embodiment, the release film for molding a resin sheet contains an inorganic compound. Examples of inorganic compounds include metal particles, metal oxides, and minerals, such as calcium carbonate, silica particles, aluminum particles, and barium titanate particles. Examples of resins include polyvinyl acetal resin and poly(meth)acrylic acid ester resin. The laminated polyethylene terephthalate film of the present invention is suitable for laminating a highly smooth release layer. Even in an embodiment in which the resin sheet contains these inorganic compounds, defects attributable to inorganic compounds, such as breakage of the resin sheet and difficulty in peeling the resin sheet from the release layer, can be suppressed. The resin components forming the resin sheet can be appropriately selected depending on the application. In one embodiment, the resin sheet containing an inorganic compound is a ceramic green sheet. For example, the ceramic green sheet may contain barium titanate as the inorganic compound. In one embodiment, the resin sheet has a thickness of 0.2 μm or more and 1.0 μm or less.

[0071] (Release Film) In one embodiment, the release film of the present invention comprises a laminated polyethylene terephthalate film and a release layer. The release layer is provided on the surface of the first coating layer A of the laminated polyethylene terephthalate film. That is, the release film comprises a laminated polyethylene terephthalate film and a release layer laminated on the first coating layer A of the laminated polyethylene terephthalate film.

[0072] The description of the release layer of the release film will be omitted because it overlaps with the description of the release layer of the above-mentioned functional layer-attached film (i.e., the recycled functional layer-attached film). Therefore, the description of the release layer of the above-mentioned functional layer-attached film can also be used as a description of the release layer of the release film according to the present invention. The release layer may be provided on the surface of the coating layer by a so-called in-line coating method in which the release layer is applied during the film formation of the laminated polyethylene terephthalate film, or may be provided on the surface of the coating layer after the laminated polyethylene terephthalate film is produced.

[0073] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. The property values ​​used in the present invention were evaluated using the following methods.

[0074] (1) Intrinsic Viscosity (IV) A film (specifically, a laminated polyethylene terephthalate film) or a polyester resin (specifically, recycled PET1-8, PET11, or MB12) was pulverized and dried, and then dissolved in a mixed solvent of phenol / tetrachloroethane = 60 / 40 (mass ratio). The solution was centrifuged to remove inorganic particles, and then an Ubbelohde viscometer was used to measure the flow time of a solution with a concentration of 0.4 (g / dl) at 30°C and the flow time of the solvent alone. The intrinsic viscosity was calculated from the ratio of these times using the Huggins equation, assuming a Huggins constant of 0.38.

[0075] (2) Si and Ti analysis As a pretreatment, approximately 1 g of sample (specifically, laminated polyethylene terephthalate film, recycled PET1-8, PET11, MB12) was taken, and 15 ml of nitric acid, 3 ml of ultrapure water, and 0.1 ml of hydrofluoric acid were added to the sample, and the sample was dissolved in acid using a microwave sample decomposition device (UltraWAVE manufactured by Milestone Corporation). After that, the amount of Si and Ti elements was measured using an ICP optical emission spectrometer (SPECTRO BLUE TI manufactured by SPECTRO Corporation).

[0076] (3) Analysis of Ba, Ni, Cu, Pd, Ag, Au, and Pt As a pretreatment, approximately 0.5 g of sample (specifically, laminated polyethylene terephthalate film, recycled PET1-8, PET11, and MB12) was taken, carbonized, and incinerated. The residue was dissolved in 1.2 N hydrochloric acid to prepare the measurement sample. The amounts of Ba, Ni, Cu, Pd, Ag, Au, and Pt were then measured using an ICP optical emission spectrometer (SPECTRO BLUE TI, manufactured by SPECTRO).

[0077] (4) Ca analysis As a pretreatment, approximately 0.5 g of sample (specifically, laminated polyethylene terephthalate film, recycled PET1-8, PET11, MB12) was collected, carbonized, and incinerated. The residue was dissolved in 1.2 N hydrochloric acid to prepare a measurement sample. Then, the amount of Ca element was measured using an ICP optical emission analyzer (SPECTRO BLUE TI manufactured by SPECTRO). By measuring the content of Ca element, the amount of calcium carbonate particles, CaCO ３ The content was calculated.

[0078] (5) Surface Roughness (SRa, SRp) The surface of the outermost layer (specifically, the first coating layer A) of the laminated polyethylene terephthalate film was measured using a stylus-type three-dimensional roughness meter (SE-3AK, manufactured by Kosaka Laboratory Co., Ltd.). Under conditions of a needle radius of 2 μm and a load of 30 mg, measurements were taken in the longitudinal direction of the laminated polyethylene terephthalate film with a cutoff value of 0.25 mm and a measurement length of 1 mm at a needle feed rate of 0.1 mm / sec. The measurement was divided into 500 points at a 2 μm pitch, and the height of each point was captured into a three-dimensional roughness analyzer (SPA-11). A similar operation was performed continuously 150 times at 2 μm intervals in the width direction of the laminated polyethylene terephthalate film, i.e., over a width of 0.3 mm of the laminated polyethylene terephthalate film, and the data was captured into the analyzer. Next, the center surface average roughness (SRa) and center line peak height (SRp) were determined using the analyzer.

[0079] (6) Average particle size The surface-roughening agent was observed with a scanning electron microscope (S-51O type, manufactured by Hitachi, Ltd.), and the magnification was appropriately changed depending on the particle size, and the photographs were enlarged and copied. Next, the periphery of each of at least 200 randomly selected particles was traced, and the circle-equivalent diameter of the particles was measured from these traced images using an image analyzer, and the average of these was taken as the average particle size.

[0080] (7) Evaluation of MLCC processability After forming a silicone-based release layer as a functional layer on the target laminated polyethylene terephthalate film, ceramic green sheets were produced and the defect rate due to the laminated polyethylene terephthalate film was evaluated. Specifically, the defect rate was evaluated using the following procedure.

[0081] (Preparation of Release Film) A coating film (wet amount) of 5 g / m2 was applied to the surface of the first coating layer A of the laminated polyethylene terephthalate film. ２ The coating solution described below was applied by reverse gravure so that the film thickness was 100°C, and then 0.5 seconds after application, the film was dried at 100°C for 2 seconds (hereinafter, sometimes referred to as "initial drying"). Without any gap after the initial drying (i.e., continuously from the initial drying), the film was heated at 130°C for 7 seconds, and then 8 seconds after this heating was completed, the film was wound into a roll. In this way, 100 sheets of release film were produced for each example.

[0082] (Coating Liquid Used to Prepare Release Film) The composition of the coating liquid used to prepare the release film is as follows. The solids content of the coating liquid was 1.0% by mass, the surface tension was 27 mN / m, and the viscosity was 5 mPa·s. This coating liquid was used after passing through a filter capable of removing 99% or more of foreign matter of 0.5 μm or larger. Methyl ethyl ketone: 57.93 parts by mass Toluene: 40.00 parts by mass Resin solution R (a long-chain alkyl group-containing acrylic polyol solution with a solids content of 40% by mass. The preparation method will be described later.) 1.75 parts by mass Crosslinking agent (hexamethoxymethylolmelamine, solids content 100% by mass) 0.25 parts by mass Silicone-based release agent (polyether-modified polydimethylsiloxane, TSF4446, solids content 100% by mass, manufactured by Momentive) 0.05 parts by mass Acid catalyst (paratoluenesulfonic acid) 0.02 parts by mass

[0083] (Preparation of Resin Solution R) Stearyl (meth)acrylate, hydroxyethyl (meth)acrylate, and methyl (meth)acrylate were mixed in a ratio of 20 mol% to 40 mol%. The mixture was then diluted with toluene to a solids concentration of 40% by mass. 0.5 mol% azobisisobutyronitrile was added under a nitrogen stream to copolymerize the mixture. This resulted in a resin solution R (i.e., a long-chain alkyl group-containing acrylic polyol solution) with a solids content of 40% by mass. The resulting polymer had a weight-average molecular weight of 30,000. (Preparation of Ceramic Green Sheets) The following materials were mixed and stirred, then dispersed for 60 minutes using a bead mill with 0.5 mm diameter zirconia beads as the dispersoid. This resulted in a ceramic slurry. Toluene 43.75 parts by mass Ethanol 43.75 parts by mass Barium titanate (HPBT-1 manufactured by Fuji Titanium Co., Ltd.) 10.86 parts by mass Polyvinyl butyral (S-LEC BM-S manufactured by Sekisui Chemical Co., Ltd.) 1.09 parts by mass DOP (dioctyl phthalate) 0.55 parts by mass The ceramic slurry was applied to the release layer of a release film with an applicator so that the thickness of the ceramic green sheet was 1.0 μm, and then dried at 90 ° C. for 2 minutes. In this way, a ceramic green sheet was produced on the release film. Note that 100 ceramic green sheets were produced in each example.

[0084] (Determination of Pass / Fail) After peeling the ceramic green sheet from the release film, the arithmetic mean roughness Ra and maximum protrusion height Rp of the peeled surface of the ceramic green sheet (i.e., the surface of both sides of the ceramic green sheet that was in contact with the release film) were measured, and the pass / fail was determined according to the following criteria. Ra and Rp were measured using a scanning white light interference microscope "Vertscan VS1530" manufactured by Hitachi High-Technologies Corporation. Good: Ra less than 8 nm and Rp less than 50 nm. Poor: Ra 8 nm or more or Rp 50 nm or more. (Calculation of Defective Rate) The defective rate for each example was calculated using the following formula: Defective rate (%) = (number of ceramic green sheets determined to be defective / 100 sheets) x 100. The defective rate for each example is shown in Table 3 according to the following classification. Good: Defective rate 3% or less. Fair: Defective rate more than 3% but 5% or less. X: Defective rate more than 5%.

[0085] (8) Melt Resistivity A sheet of the target laminated polyethylene terephthalate film before stretching was taken, and two electrodes (stainless steel wires with a diameter of 0.6 mm) were placed on both ends of the film. The film was sandwiched between two quartz plates with a width of 2 cm to form a uniform layer of molten polyester composition with a width of 2 cm and a thickness of 0.6 mm. A direct current voltage of 120 V was applied under a temperature condition of 275°C, and the current (io) was measured. This was then substituted into the following equation to obtain the melt resistivity value ρi(10 8 The resistance (Ω cm) was calculated. ρi (Ω cm) = (A / L) × (V / io) [A: electrode area, L: distance between electrodes (cm), V: voltage (V)] A (cm ２ ) = [width of molten polyester composition layer] x [thickness] = 2 (cm) x 0.06 (cm), and V = 120 (V). L is a value measured without including the diameter of the electrode, and is 1.3 cm. Evaluation was performed using the following criteria. Electrostatic adhesion S: melt specific resistance value of 0.20 or less Electrostatic adhesion A: melt specific resistance value greater than 0.20 and less than 1.00 Electrostatic adhesion B: melt specific resistance value greater than 1.00

[0086] (Preparation of Recycled PET1) A used PET film having a silicone-based release layer on one side and containing 600 ppm of calcium carbonate with a particle size of 0.9 μm was used. This film was placed in a single-screw grinder and pulverized using a 4 mm aperture screen at a rate of 1000 kg / hour to obtain a pulverized film. The resulting pulverized film was fed into a twin-screw extruder to obtain Recycled PET1. The intrinsic viscosity of Recycled PET1 was 0.56 dl / g and the Si concentration was 200 ppm. The evaluation results and various conditions are shown in Table 1.

[0087] (Preparation of Recycled PET2) A used PET film having a silicone-based release layer on one side and containing 600 ppm of calcium carbonate with a particle size of 0.9 μm was prepared. This PET film was the same PET film used in the production of ceramic green sheets. The silicone-based release layer was removed from this PET film by sandblasting. (Although it may go without saying, it should be noted that removing the silicone-based release layer also removes impurities that had adhered to the silicone-based release layer.) The film from which the silicone-based release layer had been removed was placed in a single-screw grinder and pulverized using a 4 mm aperture screen at a rate of 100 kg / h to obtain a pulverized film. The resulting pulverized film was fed into a twin-screw extruder to obtain Recycled PET2. The intrinsic viscosity of Recycled PET2 was 0.56 dl / g and the Si concentration was 5 ppm. The evaluation results and various conditions are shown in Table 1.

[0088] (Preparation of Recycled PETs 3, 4, 5, 6, 7, and 8) A used PET film having a silicone-based release layer on one side and containing 600 ppm of calcium carbonate with a particle size of 0.9 μm was used. This PET film (i.e., a PET film having a silicone-based release layer) was used in the manufacture of a multilayer ceramic capacitor. In the manufacture of the multilayer ceramic capacitor, a ceramic green sheet was formed on the silicone-based release layer of this PET film (i.e., a PET film having a silicone-based release layer), electrodes were printed on the ceramic green sheet, and the PET film was wound into a roll. In the manufacture of the multilayer ceramic capacitor, the PET film was unwound and the ceramic green sheet was peeled off from the PET film. This film was placed in a single-screw mill and pulverized using a 4 mm aperture screen at a rate of 100 kg / h to obtain pulverized film products. The resulting pulverized products were fed into a twin-screw extruder to obtain Recycled PETs 3, 4, 5, 6, 7, and 8. The evaluation results and various conditions are shown in Table 1.

[0089] The PET films used to prepare Recycled PET 1 to 3 (specifically, ET films having a silicone-based release layer) were the same product before use. The PET film used to prepare Recycled PET 4 (specifically, ET films having a silicone-based release layer) was the same product before use as the PET film used to prepare Recycled PET 5 (specifically, ET films having a silicone-based release layer). The PET film used to prepare Recycled PET 6 (specifically, ET films having a silicone-based release layer) was the same product before use as the PET film used to prepare Recycled PET 7 (specifically, ET films having a silicone-based release layer).

[0090] (Preparation of Polyethylene Terephthalate Pellets (PET11)) A continuous esterification reactor consisting of a three-stage complete mixing vessel equipped with a stirrer, a partial condenser, a raw material inlet, and a product outlet was used. The TPA rate was 2 ton / hr, EG was 2 moles per mole of TPA, and antimony trioxide was added in an amount such that the Sb atom concentration in the resulting PET was 160 ppm. These slurries were continuously fed to the first esterification reactor of the esterification reactor and reacted at 255°C under atmospheric pressure for an average residence time of 4 hours. The reaction product in the first esterification reactor was then continuously removed from the system and fed to a second esterification reactor. EG distilled off from the first esterification reactor was fed to the second esterification reactor in an amount of 8% by mass relative to the resulting polymer (the resulting PET). Further, an EG solution containing magnesium acetate in an amount to give 65 ppm of Mg atoms relative to the produced PET and an EG solution containing TMPA in an amount to give 20 ppm of P atoms relative to the produced PET were added, and the reaction was carried out at atmospheric pressure for an average residence time of 1.5 hours at 260°C. The reaction product in the second esterification reactor was then continuously removed from the system and fed to a third esterification reactor. An EG solution containing TMPA in an amount to give 20 ppm of P atoms relative to the produced PET was then added, and the reaction was carried out at atmospheric pressure for an average residence time of 0.5 hours at 260°C. The esterification reaction product produced in the third esterification reactor was continuously fed to a three-stage continuous polycondensation reactor for polycondensation, and then filtered through a stainless steel sintered filter medium (nominal filtration accuracy: 90% cutoff for 5 μm particles). This resulted in the production of polyethylene terephthalate pellets, PET11, with an intrinsic viscosity of 0.62 dl / g. The evaluation results and various conditions are shown in Table 1.

[0091] (Preparation of polyethylene terephthalate calcium carbonate masterbatch (MB12)) The above-mentioned PET11 and calcium carbonate particles having an average particle size of 0.9 μm were melted and kneaded in a twin-screw extruder to prepare a masterbatch with a calcium carbonate particle concentration of 20,000 ppm. The evaluation results and various conditions are shown in Table 1.

[0092] Example 1: After drying, each of the above PETs was melted at 290°C in a melt extruder. The molten PET was subjected to two-stage filtration: a filter made of sintered stainless steel fibers with a 95% cut diameter of 15 μm, and a filter made of sintered stainless steel particles with a 95% cut diameter of 15 μm. The molten PETs were then merged in a feed block and laminated to form a layer B (non-release side layer) containing 75% PET11 and 25% MB12, a layer A (release side layer) containing PET11, and a layer C containing 60% PET11 and 40% recycled PET1. The resulting extrusions were then cast into a sheet at a speed of 45 m / min, electrostatically bonded to a casting drum at 30°C, and cooled. This resulted in an unstretched polyethylene terephthalate sheet with an intrinsic viscosity of 0.56 dl / g. The layer ratio (i.e., thickness ratio) was adjusted so that the layer A / layer C / layer B = 40% / 40% / 20% based on the calculation of the output rate of each extruder.

[0093] The electrostatic contact conditions at this time were as follows: electrode material was tungsten, cylindrical (wire) with a diameter of 0.2 mm and a length of 0.5 m, current was controlled at a constant value of 5 mA, electrode tension was 5 kg, and electrode renewal speed was 5 m / hour.

[0094] Next, this unstretched polyethylene terephthalate sheet was heated with an infrared heater and then stretched 3.5 times in the machine direction at a roll temperature of 80°C using the speed difference between the rolls. Thereafter, it was introduced into a tenter and stretched 4.2 times in the transverse direction at 140°C. It was then heat-treated at 210°C in a heat-setting zone. It was then subjected to a 2.3% relaxation treatment in the transverse direction at 170°C to obtain a mill roll (5.0 m wide) of laminated polyethylene terephthalate film having a thickness of 25 μm.

[0095] This mill roll was transferred to a slitter and treated with a static eliminator (Kasuga Electric Co., Ltd., high-density static elimination processing system) and a web cleaner (Shinko Co., Ltd., ultrasonic cleaner system). The mill roll was then cut to a width of 1,400 mm, and a core material with resin-impregnated paper having an inner diameter of 6 inches, a wall thickness of 12 mm, a moisture content of 8%, a surface roughness (SRa = 4.3 nm, SRp = 41.4 nm), and a flattening compressive strength of 200 kg / 100 mm was wound up to a length of 8,000 m at a maximum speed of 400 m / min using a contact roll with a rubber hardness of 60 degrees, under a contact surface pressure of 200 kg / m and a tension of 15 MPa. As a result, a biaxially stretched polyethylene terephthalate film roll was obtained. A laminated polyethylene terephthalate film was cut out from the biaxially stretched polyethylene terephthalate film roll and various evaluations were performed. This laminated polyethylene terephthalate film was a film in which Layer A (first coating layer), Layer C (intermediate layer), and Layer B (second coating layer) were laminated in this order. The evaluation results are shown in Tables 2 and 3.

[0096] The dust level in the atmosphere during the film manufacturing process was Class 1000.

[0097] (Examples 2 and 3) The raw material composition of layer C was changed from Example 1, and the film thickness of the biaxially oriented polyethylene terephthalate film roll was also changed to obtain the biaxially oriented polyethylene terephthalate film roll shown in Table 2. Laminated polyethylene terephthalate films were cut out from the biaxially oriented polyethylene terephthalate film roll, and various evaluations were performed. The evaluation results are shown in Tables 2 and 3.

[0098] (Examples 4, 5, 6, 7, 8, 9, 10, and 11) The raw material of Layer C in Example 1 was changed from recycled PET1 to the raw materials and blending amounts shown in Table 2, and the film thickness of the biaxially oriented polyethylene terephthalate film roll was also changed to obtain the biaxially oriented polyethylene terephthalate film rolls shown in Table 2. Laminated polyethylene terephthalate films were cut out from the biaxially oriented polyethylene terephthalate film rolls and subjected to various evaluations. The evaluation results are shown in Tables 2 and 3.

[0099] (Example 12) The layer ratio (i.e., thickness ratio) of Example 1 was changed as shown in Table 2 to obtain a biaxially oriented polyethylene terephthalate film roll shown in Table 2. A laminated polyethylene terephthalate film was cut out from the biaxially oriented polyethylene terephthalate film roll and subjected to various evaluations. The evaluation results are shown in Tables 2 and 3.

[0100] Comparative Example 1 The raw materials used in Example 1 were changed as shown in Table 2, and the film thickness of the biaxially oriented polyethylene terephthalate film roll was also changed to obtain the biaxially oriented polyethylene terephthalate film roll shown in Table 2. A laminated polyethylene terephthalate film was cut out from the biaxially oriented polyethylene terephthalate film roll and subjected to various evaluations. The evaluation results are shown in Tables 2 and 3.

[0101] Comparative Example 2 The layer structure of Example 1 was changed to two layers (A / B), and the film thickness of the biaxially oriented polyethylene terephthalate film roll was also changed to obtain the biaxially oriented polyethylene terephthalate film roll shown in Table 2. A laminated polyethylene terephthalate film was cut out from the biaxially oriented polyethylene terephthalate film roll and subjected to various evaluations. The evaluation results are shown in Tables 2 and 3.

[0102] Reference Example 3 The layer ratio (i.e., thickness ratio) of Example 1 was changed as shown in Table 2, and the film thickness of the biaxially oriented polyethylene terephthalate film roll was also changed, to obtain the biaxially oriented polyethylene terephthalate film roll shown in Table 2. A laminated polyethylene terephthalate film was cut out from the biaxially oriented polyethylene terephthalate film roll and subjected to various evaluations. The evaluation results are shown in Tables 2 and 3. Note that in Reference Example 3, the three-dimensional center plane average surface roughness (SRa) of the surface was 1 nm or more and 7.5 nm or less, but the maximum peak height (SRp) of the surface was 220 nm or more. Reference Example 3 may be referred to as Example 13.

[0103] Comparative Example 4 The layer ratio (i.e., thickness ratio) of Example 1 was changed as shown in Table 2, and the film thickness of the biaxially oriented polyethylene terephthalate film roll was also changed to obtain the biaxially oriented polyethylene terephthalate film roll shown in Table 2. A laminated polyethylene terephthalate film was cut out from the biaxially oriented polyethylene terephthalate film roll and subjected to various evaluations. The evaluation results are shown in Tables 2 and 3.

[0104] Comparative Example 5 The layer ratio (i.e., thickness ratio) of Example 11 was changed as shown in Table 2, and the film thickness of the biaxially oriented polyethylene terephthalate film roll was also changed to obtain the biaxially oriented polyethylene terephthalate film roll shown in Table 2. A laminated polyethylene terephthalate film was cut out from the biaxially oriented polyethylene terephthalate film roll and subjected to various evaluations. The evaluation results are shown in Tables 2 and 3.

[0105] Ceramic green sheets were produced using the biaxially oriented polyethylene terephthalate films of Examples 1 to 12, and the defect rate due to the biaxially oriented polyethylene terephthalate films was evaluated. The defect rate was suppressed to 3% or less, resulting in good ceramic green sheets. Furthermore, the use of recycled film enabled the production of environmentally friendly products (specifically, biaxially oriented polyethylene terephthalate films and release films). The laminated polyethylene terephthalate film of the Examples exhibited performance equivalent to that of the laminated polyethylene terephthalate film of Comparative Example 2 (i.e., a laminated polyethylene terephthalate film without recycled PETs 1 to 8). In Comparative Examples 1, 4, and 5, the three-dimensional center plane average surface roughness (SRa) and maximum peak height (SRp) of the first coating layer A were outside the ranges of the present invention, and the MLCC processability (i.e., the moldability of the ceramic green sheet) was insufficient. Comparative Example 2 did not contain any Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, or Au elements, and was outside the scope of the present invention. Comparative Example 2 did not use recycled PET 1-8 and therefore did not contribute to reducing the environmental impact. Furthermore, Examples 5-11 had superior electrostatic adhesion compared to Examples 1-4 and 12. That is, Examples 5-11 had superior film-forming properties and higher yields compared to Examples 1-4 and 12. Therefore, Examples 5-11 could reduce product costs compared to Examples 1-4 and 12.

[0106]

[0107] The calcium carbonate concentration in Table 2 is the concentration of calcium carbonate in the laminated polyethylene terephthalate film when the mass of the B layer (second coating layer) is taken as 100 mass %.

[0108] The concentration of each element in Table 3, that is, the content of each element, is the content of each element in the laminated polyethylene terephthalate film when the mass of Layer C (intermediate layer) is taken as 100 mass %.

[0109] The laminated polyethylene terephthalate film of the present invention can suppress the transfer of the surface shape to a processed product even when produced using a recycled resin containing one or more of the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au. Therefore, the present invention has industrial applicability.

Claims

1. A laminated polyethylene terephthalate film comprising a first coating layer containing a polyethylene terephthalate resin, an intermediate layer containing a polyethylene terephthalate resin, and a second coating layer containing a polyester resin, wherein the first coating layer has a surface for laminating a functional layer, the intermediate layer contains one or more of the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au, and the total amount of the elements Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au is 0.1 ppm or more and 5000 ppm or less with respect to the total mass of the intermediate layer, and the laminated polyethylene terephthalate film satisfies at least one of the following requirements (1) and (2): (1) The three-dimensional center plane average surface roughness (SRa) of the surface is 1 nm or more and 7.5 nm or less, and (2) The maximum peak height (SRp) of the surface is 220 nm or less.

2. The laminated polyethylene terephthalate film according to claim 1, wherein the first coating layer is a layer that is substantially free of particles and the thickness of the first coating layer is 7.0 μm or more and 20.0 μm or less.

3. Melting resistivity at 275℃ (ρi(10 8 2. The laminated polyethylene terephthalate film according to claim 1, having a compressive strength (Ω·cm) of 1.00 or less.

4. The laminated polyethylene terephthalate film according to claim 1, wherein the intermediate layer contains one or more of Ti, Ni, Cu, Pt, Pd, Ag, and Au, and the total amount of Ti, Ni, Cu, Pt, Pd, Ag, and Au is 10 ppm or more relative to the total mass of the intermediate layer.

5. The laminated polyethylene terephthalate film as described in claim 1, wherein the content of silicon element is 2,300 ppm or less based on the total mass of the intermediate layer.

6. The laminated polyethylene terephthalate film as described in claim 1, wherein the content of Ba element is 2,300 ppm or less based on the total mass of the intermediate layer.

7. The laminated polyethylene terephthalate film according to claim 1, wherein the intermediate layer contains 5% by mass or more and 100% by mass or less of a resin obtained by material recycling and / or chemical recycling of a film with a functional layer.

8. The laminated polyethylene terephthalate film according to claim 1, wherein the intrinsic viscosity (IV) of the laminated polyethylene terephthalate film is 0.400 dl / g or more and 0.700 dl / g or less.

9. The laminated polyethylene terephthalate film of claim 1, wherein the second coating layer comprises lubricant particles.

10. A release film comprising: a laminated polyethylene terephthalate film according to any one of claims 1 to 9; and a functional layer provided on the surface of the first coating layer provided on the laminated polyethylene terephthalate film, wherein the functional layer is a release layer.

11. A method for producing the laminated polyethylene terephthalate film according to any one of claims 1 to 9, comprising the following steps: (Step 1) a pulverization step, comprising pulverizing a polyethylene terephthalate film having a functional layer to form a pulverized product; (Step 2) a chipping step, comprising chipping the pulverized product to form recycled chips; (Step 3) a step of preparing at least the recycled chips and polyethylene terephthalate chips different from the recycled chips such that the total content of Si, Ti, Ba, Ni, Cu, Pt, Pd, Ag, and Au elements is 0.1 ppm or more and 5000 ppm or less with respect to the total mass of the laminated polyethylene terephthalate film; and (Step 4) a recycled film formation step of melt-extruding the recycled chips and the polyethylene terephthalate chips to form the polyethylene terephthalate film which is the intermediate layer.

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