Laminated polyester film, laminated ceramic chip capacitor, and polyester film production method

Abstract

The present invention addresses the problem of providing a laminated polyester film that achieves both durability, such as crack resistance and solvent resistance, during use as a process film and removability which enables easy removal with an aqueous cleaning solution after use, and that can be suitably used for process conveyance applications, such as a process release film. Provided as a solution is a laminated polyester film that has, on at least one surface of a polyester film, a water soluble resin layer X which has, as the main skeleton, an acrylic having a monomer unit represented by chemical formula (1) or chemical formula (2), wherein when the glass transition temperature of the polyester film is represented as Tg1 and the glass transition temperature of the resin layer X is represented as Tg2, Tg2-Tg1 is 20-100°C.

Description

Multilayer polyester film, multilayer ceramic chip capacitor, and method for manufacturing polyester film

[0001] The present invention relates to a laminated polyester film that is used for various applications, primarily in process applications.

[0002] In recent years, the increase in plastic waste has become an environmental problem, and efforts to reuse plastics have become more active. Plastics are used in a variety of forms, and one method of reusing these plastics is material recycling. In material recycling, plastic waste is generally separated by resin type, and each resin is remelted and molded into a new form for use.

[0003] In order to facilitate the process of separating resins, resin composites are known that function as composites of multiple types of resins while in use as a product, and then allow the individual composite resin components to be separated after use.

[0004] In the case of the resin composite, for example, a part of the constituent resins is a water-soluble resin, and a base material, a water-soluble resin, and other functional resins are laminated in this order. After use, the resin composite is immersed in water to dissolve and remove the water-soluble resin, thereby separating the base material and the functional resin, and the resins can be recovered separately.

[0005] For example, Patent Document 1 discloses a technology in which a water-soluble resin layer (polyvinyl alcohol) is provided as a release functional layer between a substrate (polyester film) and a functional resin (a release layer made of silicone), and the release functional layer is removed by washing the laminated film with water after use, thereby peeling off the release layer made of silicone laminated on the polyester film and allowing only the polyester film to be recycled.

[0006] Japanese Patent Application Laid-Open No. 2004-050681

[0007] However, when a polyvinyl alcohol layer is provided as a release functional layer, although polyvinyl alcohol is a resin with excellent water solubility, it is a crystalline resin and therefore crystallization progresses when placed under certain environments, which can cause whitening of the film's appearance or unevenness in the surface properties due to uneven crystallization. The unevenness in the surface properties can be a problem in ensuring quality stability, and the whitening can hinder identification analysis that takes advantage of the film's translucency during the recycling process, so improvements in these areas were needed.

[0008] On the other hand, when attempting to use an amorphous resin, acrylic, instead of polyvinyl alcohol in order to suppress whitening due to crystallization, it was found that it may be difficult to achieve both durability during use as a process film and removability that allows the peelable functional layer to be easily removed with an aqueous cleaning solution after use.

[0009] Therefore, the object of the present invention is to provide a laminated polyester film that combines durability while being used as a process film with removability that allows the release functional layer to be easily removed with an aqueous cleaning solution after use.

[0010] In order to solve the above problems, a preferred embodiment of the present invention has the following configuration: [I] A laminated polyester film having, on at least one surface of a polyester film, a water-soluble resin layer X having an acrylic as a main skeleton containing a monomer unit represented by chemical formula (1) or (2), wherein, when the glass transition temperature of the polyester film is Tg1 and the glass transition temperature of the resin layer X is Tg2, Tg2-Tg1 is 20°C or higher and 100°C or lower.

[0011]

[0012] R １ is a hydrogen atom or a methyl group, R ２ represents any functional group.

[0013]

[0014] R ３ is a hydrogen atom or a methyl group, R ４ and R ５represents any functional group. [II] A laminated polyester film having, on at least one side of the polyester film, a water-soluble resin layer X having an acrylic main skeleton containing a monomer unit represented by chemical formula (1) or chemical formula (2), wherein the orientation parameter Rxy of the resin layer X represented by the following formula is 0.02 or more and less than 1.00. Rxy=(Ax-Ay) / (Ax+Ay), where Ax is the CH of the acrylic main chain measured by infrared spectroscopy. ２ CH of the acrylic main chain in the direction in which the bending vibration is maximum ２ Absorption intensity of bending vibration Ay: CH of the acrylic main chain in a direction perpendicular to the direction of the maximum ２ Bending vibration absorption strength

[0015]

[0016] R １ is a hydrogen atom or a methyl group, R ２ represents any functional group.

[0017]

[0018] R ３ is a hydrogen atom or a methyl group, R ４ and R ５ [III] The laminated polyester film according to [I] or [II], wherein the hydrophilic parameter Wx of the resin layer X represented by the following formula is 5 or more and 15 or less:

[0019] Wx = Aph / Apb Aph: 3000 cm measured by infrared spectroscopy －１ ~3600cm －１ Apb: Area of ​​the peak derived from the hydrophilic group at 1446 cm measured by infrared spectroscopy －１ Nearby CH ２[IV] The laminated polyester film according to any one of [I] to [III], wherein the weight-average molecular weight Mw of the extract obtained by extracting the resin layer X with a 0.5 mol / L acetate buffer solution and calculating the polyethylene oxide equivalent by gel permeation chromatography (hereinafter, GPC) method is 20,000 or more and 500,000 or less. [V] The laminated polyester film according to any one of [I] to [IV], further comprising a layer Y on the surface of the resin layer X opposite to the surface that contacts the polyester film, the layer Y having an ethanol contact angle Ey (°) that satisfies the following formula: |Ey(1) - Ey(20)| ≦ 5.0 Ey(1): contact angle 1 second after ethanol contacts layer Y Ey(20): contact angle 20 seconds after ethanol contacts layer Y [VI] The laminated polyester film according to [V], wherein a release layer is provided on the surface of layer Y opposite to the surface that contacts layer X, and the release layer is used for release applications in which the release layer is peeled from layer Y. [VII] The laminated polyester film according to [VI], which is used in an application in which the layer X and the layer Y are further removed after the release layer is peeled from the layer Y. [VIII] The laminated polyester film according to any one of [V] to [VII], which is used in an application in which the laminated polyester film from which the layer X and the layer Y have been removed is reused. [IX] The laminated polyester film according to [VI] or [VII], wherein the release layer is a ceramic sheet containing barium titanate as a main component. [X] A multilayer ceramic chip capacitor obtained by laminating the ceramic sheet released from the laminated polyester film according to any one of [I] to [IV], which further has a silicone resin layer Y on the surface of the layer X opposite to the surface that contacts the polyester film, and which has a ceramic sheet containing barium titanate as a main component on the surface of the layer Y opposite to the surface that contacts the layer X. [XI] A method for producing a polyester film, comprising the steps of: using a laminated polyester film according to any one of [I] to [IV], which has at least a release layer, a silicone resin layer Y, the layer X, and a polyester film in this order; peeling the release layer from the layer Y; removing the layer Y and the layer X from the film from which the release layer has been peeled; producing recycled raw materials from the film from which the release layer, the layer Y, and the layer X have been removed; and producing a film using the recycled raw materials.

[0020] According to the present invention, it is possible to provide a laminated polyester film in which an acrylic water-soluble resin layer is formed on a polyester substrate, which has both durability while being used as a process film and removability that allows the release functional layer to be easily removed with an aqueous cleaning solution after use.

[0021] FIG. 1 is a schematic diagram of a removal device for removing a functional layer.

[0022] A preferred embodiment of the present invention will be described in detail below with reference to a specific example.

[0023] A preferred embodiment of the laminated polyester film of the present invention has a water-soluble resin layer X having an acrylic main skeleton on at least one surface of the polyester film. Herein, the resin layer X may be simply referred to as layer X.

[0024] The polyester referred to in the present invention comprises a dicarboxylic acid component and a diol component. The term "component" refers to the smallest unit obtainable by hydrolysis of a polyester. Examples of the dicarboxylic acid component constituting such a polyester include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, and 4,4'-diphenyletherdicarboxylic acid, as well as ester derivatives thereof.

[0025] Examples of diol components constituting such polyesters include aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol, alicyclic diols such as cyclohexanedimethanol and spiroglycol, and diols in which multiple units of the above-mentioned diols are linked together. Among these, from the viewpoints of mechanical properties and transparency, polyesters that are preferably used are polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN), and polyesters in which isophthalic acid or naphthalenedicarboxylic acid is copolymerized with a portion of the dicarboxylic acid component of PET, and polyesters in which cyclohexanedimethanol, spiroglycol, or diethylene glycol is copolymerized with a portion of the diol component of PET.

[0026] The term "acrylic" as used herein refers to a polymer having a monomer unit represented by chemical formula (1) or chemical formula (2). ２ The part represented by -CONR in chemical formula (2) also includes salts such as metal salts of carboxylic acids and ammonium salts of carboxylic acids. ４ R ５ The portion represented by includes those which have been converted into quaternary ammonium salts by reaction with a quaternizing agent.

[0027]

[0028]

[0029] R １ and R ３ When all the monomer units of the acrylic skeleton are taken as 100 mol %, from the viewpoint of water solubility, it is preferable that hydrogen atoms account for at least 70 mol %, and more preferably 80 mol % or more.

[0030] The water-soluble resin layer X of the present invention has an acrylic main skeleton. In this specification, the term "main skeleton" means that the proportion of the main skeleton in the entire skeleton constituting the resin is 80 mol % or more, more preferably 90 mol % or more.

[0031] The water-soluble resin layer X having an acrylic main skeleton is２ or R ４ , R ５ The water solubility, hydrophilicity, and glass transition temperature of acrylic can be controlled by the side chains introduced into the polymers, etc., and specifically, this can be controlled by changing the types and ratios of hydrophilic and hydrophobic monomer components used during polymerization.

[0032] Examples of hydrophilic monomer components used in acrylic polymerization include amide monomers such as acrylamide and methacrylamide, monocarboxylic acid monomers such as acrylic acid, methacrylic acid, and crotonic acid, dicarboxylic acid monomers such as maleic acid, fumaric acid, itaconic acid, and muconic acid, organic sulfonic acid monomers such as vinyl sulfonic acid, styrene sulfonic acid, and 2-acrylamido-2-methylpropanesulfonic acid, and vinyl monomers having a tertiary amino group such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, diethylaminopropyl (meth)acrylamide, allylamine, diallylamine, and triallylamine. Of the above, various organic acid monomers may be their sodium salts, potassium salts, etc., and the above vinyl monomers having a tertiary amino group may be their salts with inorganic or organic acids such as hydrochloric acid, sulfuric acid, and acetic acid, or may be quaternary ammonium salts obtained by reaction with a quaternizing agent such as methyl chloride, benzyl chloride, dimethyl sulfate, or epichlorohydrin. These hydrophilic monomers may be used either alone or in combination of two or more.

[0033] Examples of hydrophobic monomer components used in acrylic polymerization include various acid esters that are derivatives of the various organic acids described above, and examples of the skeleton of the ester moiety include an alkyl group (having 1 to 8 carbon atoms), a methoxyethyl group, and an ethoxyethyl group. Various N-substituted acrylamides and N-substituted methacrylamides are also acceptable, including, for example, N-alkylacrylamides, N-alkylmethacrylamides, N,N-dialkylacrylamides, N,N-dialkylmethacrylamides, N-isopropylacrylamide, and 4-acryloylmorpholine. Any of these hydrophobic monomers may be used alone, or two or more may be used.

[0034] The acrylic may be polymerized using a crosslinkable vinyl monomer as another monomer component, provided that the crosslinkable vinyl monomer does not impair water solubility. Representative examples of the crosslinkable vinyl monomer include the following. Examples of bifunctional vinyl monomers include di(meth)acrylates such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and triethylene glycol di(meth)acrylate; bis(meth)acrylamides such as methylene bis(meth)acrylamide, ethylene bis(meth)acrylamide, and hexamethylene bis(meth)acrylamide; divinyl esters such as divinyl adipate and divinyl sebacate; allyl methacrylate, epoxy acrylates, urethane acrylates, N-methylolacrylamide, diallylamine, diallyldimethylammonium, diallyl phthalate, diallyl chlorendate, and divinylbenzene. Examples of trifunctional monomers include 1,3,5-triacryloylhexahydro-S-triazine, triallyl isocyanurate, triallylamine, triallyl trimellitate, N,N-diallylacrylamide, etc., and examples of tetrafunctional vinyl monomers include tetramethylolmethane tetraacrylate, tetraallyl pyromellitate, N,N,N',N'-tetraallyl-1,4-diaminobutane, tetraallylamine salt, tetraallyloxyethane, etc. These may be used alone or in combination of two or more.

[0035] In the present invention, the resin layer X being water-soluble is defined as satisfying at least one of the following conditions (A) and (B).

[0036] Regarding condition (A), first, the laminated polyester film of the present invention is embedded in resin on both sides, and then cross-sectioned using an ultrathin slice preparation device to prepare a thin film slice approximately 200 nm thick. The thin film slice is then picked up and fixed flat on the observation stage of an electron microscope. Next, the thin film slice, along with the observation stage, is immersed in water at 50°C for 10 minutes, and then thoroughly dried after immersion. The dried thin film slice is observed under an electron microscope, and if the portion corresponding to the resin layer X is recessed and missing, condition (A) is considered to be satisfied. Note that when preparing the thin film slice, cutting the cross section at an angle can increase the area occupied by layer X in the cross-sectional thin film slice, making it easier to confirm the presence or absence of missing parts by electron microscope observation.

[0037] Regarding condition (B), when the resin layer X is physically peeled off from the surface of the laminated polyester film of the present invention, collected, and immersed in water at 50°C for 10 minutes, the mass loss due to immersion is 15% by mass or more. When measuring the mass before and after immersion, the sample is dried under vacuum until the moisture content is 50 ppm or less, and then the measurement is performed. After immersion, the water and the peeled material are separated by filtration using filter paper (Advantec No. 5C) with a retention particle size of 1 μm. The peeled material is collected in a manner such that the majority of the collected material is composed of the resin layer X. For example, if a different layer is present on the side of the resin layer X opposite the surface that contacts the polyester film, the layer is preferably removed in advance by etching or other techniques to expose the resin layer X on the outermost surface, and then the resin layer X is gradually physically peeled off.

[0038] From the viewpoint of durability, the resin layer X preferably satisfies at least the condition (A), and more preferably satisfies both the conditions (A) and (B). From the viewpoint of removability, the resin layer X preferably satisfies at least the condition (B).

[0039] In the present invention, the ratio of the hydrophilic monomer to all the acrylic monomers is preferably 30 mol % or more, more preferably 40 mol % or more, and even more preferably 50 mol % or more, in order to enhance the water solubility of the resin layer X. Furthermore, as the hydrophilic monomer, a nonionic monomer having no ionicity is preferable to an anionic monomer such as an organic acid monomer or a cationic monomer having a tertiary amino group, from the viewpoint of achieving both durability and water solubility, and amide monomers such as acrylamide and methacrylamide are particularly preferred.

[0040] The laminated polyester film of the present invention is characterized in that the CH of the acrylic main chain of the resin layer X is measured by infrared spectroscopy. ２ CH of the acrylic main chain in the direction in which the bending vibration is maximum ２ The bending vibration absorption intensity is Ax, and the CH of the acrylic main chain in the direction perpendicular to the direction of the maximum. ２ When the absorption intensity of bending vibration is Ay, the orientation parameter Rxy represented by the following formula 1 is preferably 0.02 or more and less than 1.00. Rxy=(Ax-Ay) / (Ax+Ay) Formula 1 When Rxy is 0.02 or more, the orderliness of the arrangement of the molecular chains of the acrylic, which is an amorphous resin, is increased, and even when a solvent is applied or exposed to a solvent during processing or use, the permeation of the solvent into the resin layer X can be suppressed, resulting in good durability. In principle, Rxy does not exceed 1.00. Rxy is more preferably 0.08 or more and less than 1.00.

[0041] An example of a means for achieving Rxy of 0.02 or more and less than 1.00 is an in-line coating method in which an aqueous coating material that is the basis of the resin layer X is applied to the surface of a polyester film, and the polyester film is stretched while simultaneously volatilizing the water content of the aqueous coating material to form a film as the resin layer X. The coating method is not particularly limited, but examples that can be used include reverse coating, spray coating, bar coating, gravure coating, die coating, air knife coating, and doctor knife coating.

[0042] In addition, in order to set the Rxy value within a more preferred range, it is preferable to adjust the film thickness of the coating material, the stretching speed, the hydrophilicity of the water-soluble resin, etc. so that the relationship between the rate at which water evaporates from the coating material applied in the in-line coating method and the rate at which the polyester film is stretched is within a certain range.

[0043] The laminated polyester film of the present invention has a 3000 cm －１ ~3600cm －１ The area of ​​the hydrophilic group-derived peak A is measured by infrared spectroscopy at 1446 cm －１ Nearby CH ２ When the area of ​​the deformation vibration peak is Apb, the hydrophilicity parameter Wx represented by the following formula 2 is preferably 5 or more and 15 or less.

[0044] Wx = Aph / Apb ...Equation 2 When Wx is 5 or more and 15 or less, cracks or breaks in the resin layer X can be suppressed when the laminated polyester film is bent at an acute angle during processing. Furthermore, for the purpose of recycling, moisture is added to the resin layer X, and the removability is improved when the resin layer X is peeled off from the polyester film by a physical method. If Wx is less than 5, the resin layer X loses rigidity due to hydrophilicity, and the removability may be reduced. If Wx exceeds 15, the resin layer X becomes too rigid, and cracks or breaks may occur in the resin layer X when the laminated polyester film is bent at an acute angle during processing. Wx is more preferably 8 or more, and more preferably 10 or more. Furthermore, Wx is preferably 13 or less. One way to achieve Wx of 5 or more and 15 or less is to adjust the ratio of hydrophilic components among the constituent components of the acrylic resin within a specific range.

[0045] In the laminated polyester film of the present invention, the resin layer X is extracted with a 0.5 mol / L acetate buffer solution, and the weight-average molecular weight Mw of the extract, calculated in terms of polyethylene oxide by gel permeation chromatography (hereinafter, GPC), is preferably 20,000 or more and 500,000 or less. By setting the Mw within this range, the toughness of the resin layer X is increased, improving film-forming properties, and the removability of the resin layer X when peeled from the polyester film after adding moisture is improved. The Mw is more preferably 100,000 or more and 500,000 or less. Examples of means for achieving an Mw of 20,000 or more and 500,000 or less include a method of adjusting the Mw to within a target range by measuring the viscosity of the polymerization solution during polymerization of the resin of the resin layer X and stopping the polymerization reaction when a predetermined viscosity is reached by adding a polymerization terminator, diluting the polymerization solution, or adjusting the amount of monomer added.

[0046] The laminated polyester film of the present invention preferably further comprises a layer Y on the surface of the resin layer X opposite to the surface in contact with the polyester film, the layer Y having a contact angle Ey (°) of ethanol that satisfies the following formula 3:

[0047] |Ey(1)-Ey(20)|≦5.0 ...Equation 3 In Equation 3, Ey(1) is the contact angle 1 second after a droplet of ethanol contacts layer Y, and Ey(20) is the contact angle 20 seconds after a droplet of ethanol contacts layer Y. |Ey(1)-Ey(20)| represents the absolute value of the difference between the two contact angles. When layer Y satisfies the range of Equation 3, the durability of the laminated film formed by combining layers X and Y is improved when a coating material containing a highly polar organic solvent is applied to layer Y to form an additional topcoat layer. |Ey(1)-Ey(20)| is more preferably 3.0 or less. Examples of means for making layer Y satisfy Equation 3 include selecting a material with low water solubility as the material for layer Y, and forming resin layer X using an in-line coating method in which a polyester film is stretched and a film is formed simultaneously. When a coating material containing a highly polar organic solvent is applied on top of layer Y to form a further topcoat layer, the organic solvent in the topcoat layer passes through layer Y and reaches layer X, and it is believed that the durability of layer X against the solvent affects the entire laminate film formed by adding layers X and Y together. Therefore, it is believed that forming resin layer X by an in-line coating method will increase the durability of layer X against organic solvents, and also improve the durability of the laminate film formed by adding layers X and Y together.

[0048] Next, another preferred embodiment of the laminated polyester film of the present invention will be described. The laminated polyester film of the present invention preferably has, on at least one side of the polyester film, a water-soluble resin layer X having an acrylic main skeleton containing a monomer unit represented by chemical formula (1) or (2). Furthermore, in the laminated polyester film of the present invention, the value of Tg2-Tg1, where Tg1 (°C) is the glass transition temperature of the polyester film and Tg2 (°C) is the glass transition temperature of the resin layer X, is preferably 20°C or higher and 100°C or lower. By setting the value of Tg2-Tg1 to 20°C or higher and 100°C or lower, even when a solvent is applied or exposed to a solvent during processing or use, a decrease in interfacial adhesion due to differences in molecular chain order between the resin layer X and the polyester film can be suppressed, resulting in good durability. Furthermore, for the purpose of recycling, the resin layer X can be easily removed by adding moisture to the resin layer X and physically peeling it off from the polyester film. The value of Tg2-Tg1 is more preferably 50°C or higher and 90°C or lower. In particular, durability can be improved by having a Tg2-Tg1 value of 100°C or less. For example, if the Tg2-Tg1 value exceeds 100°C, the order of the resin layer X becomes too high, and the hardness of the resin layer X becomes too high compared to the polyester film, which may lead to cracking and reduced interfacial adhesion. Furthermore, if the Tg2-Tg1 value is 100°C or less, the hardness of the resin layer X becomes too high compared to the polyester film, which may lead to incomplete removal when peeling the resin layer X from the polyester film by physical means, making it difficult for physical forces to be transmitted to the resin layer X. Furthermore, if the Tg2-Tg1 value is 20°C or more, removability can be improved when adding moisture to the resin layer X and peeling the resin layer X from the polyester film by physical means. This embodiment can prevent the hardness of the resin layer X from becoming too low, which may lead to physical forces being viscously dissipated and difficult for the physical forces to be transmitted to the resin layer X when peeling the resin layer X from the polyester film, making it difficult for the physical forces to be transmitted to the resin layer X, resulting in incomplete removal.

[0049] One method for adjusting the Tg2-Tg1 value to 20°C or more and 100°C or less is to adjust the orderliness by self-organization of the hydrophilic components by adjusting the ratio of the hydrophilic components among the constituent components that make up the acrylic resin within a specific range.

[0050] The laminated polyester film of the present invention is preferably used for release applications in which a release layer is provided on the surface of Layer Y opposite to the surface in contact with Layer X, and the release layer is peeled off from Layer Y.

[0051] The release layer may be, for example, a ceramic sheet containing barium titanate as a main component. In this case, the ceramic sheet peeled off from layer Y is preferably laminated and used to manufacture a multilayer ceramic chip capacitor.

[0052] The laminated polyester film of the present invention is preferably used in applications in which the layer X and the layer Y are further removed after the release layer is peeled from the layer Y. The laminated polyester film from which the layer X and the layer Y have been removed is preferably used in applications in which it can be reused.

[0053] A preferred embodiment of the method for producing a laminated polyester film of the present invention will be described below using a specific example.

[0054] The laminated polyester film of the present invention is produced using an in-line coating method in which an aqueous coating material that forms the resin layer X is applied to the surface of a polyester film before stretching, and the polyester film is stretched while simultaneously volatilizing the water content of the aqueous coating material to form the resin layer X.

[0055] First, the raw material for the polyester film is introduced into a single-screw or twin-screw extruder, heated and melted, and then extruded through a die (T-die) with a linear lip. The raw material is preferably dried to a moisture content of 50 ppm or less. The extruded molten resin is cooled and solidified on a casting drum with a surface temperature of 20°C to 60°C, forming an unstretched sheet. At this time, it is preferable to apply static electricity to make the sheet adhere to the casting drum in order to obtain a uniform film.

[0056] Next, this unstretched sheet is heated using roll heating, and if necessary, infrared heating, etc., to a temperature above Tg and below Tg + 40°C relative to the glass transition temperature Tg of the unstretched sheet, and stretched in the longitudinal direction (hereinafter referred to as MD) (MD stretching) to obtain a uniaxially stretched film. MD stretching is preferably performed using the difference in peripheral speed between two or more rolls. Furthermore, stretching in multiple sections while fixing the film with nip rolls to prevent slippage is preferred, as this efficiently and uniformly applies stress to the film and makes it easier to impart orientation to the film. The MD stretching ratio is preferably 2.5 times or more and 5.0 times or less. By setting the ratio to 2.5 times or more, more preferably 3.0 times or more, uneven stretching in the subsequent TD stretching can be suppressed. Furthermore, by setting the ratio to 5.0 times or less, more preferably 4.5 times or less, breakage of the film during film formation can be prevented.

[0057] Next, an aqueous coating material that will be the base of the resin layer X is adjusted to a desired solid content concentration and then applied to the obtained uniaxially stretched film by bar coating.

[0058] Next, the film is stretched in a direction perpendicular to the MD (hereinafter referred to as TD) (TD stretching). As a TD stretching method, a tenter method is preferably used, in which both ends of the film in the width direction are gripped with clips and stretched while being transported through a heat treatment device. At this time, the preheating and stretching temperature for TD stretching is preferably Tg + 10°C or higher and Tg + 50°C or lower, relative to the glass transition temperature Tg of the unstretched sheet. The TD stretching ratio is preferably 3.0 times or higher and 5.5 times or lower. By setting the ratio to 3.0 times or higher, more preferably 3.5 times or higher, the molecular chain order of the acrylic resin applied to the surface can be further improved. Furthermore, by setting the ratio to 5.5 times or lower, more preferably 5.0 times or lower, the film can be prevented from breaking during film formation. The stretching speed in the TD stretching is preferably 5% / sec or more and 150% / sec or less, more preferably 20% / sec or more and 100% / sec or less, in order to enhance the orderliness of the molecular chains of the acrylic resin.

[0059] Although the detailed description has been given here of an example in which sequential biaxial stretching is performed by separately stretching in the MD and TD directions, a simultaneous biaxial stretching method in which stretching in the MD and TD directions is performed simultaneously may also be used as long as the effects of the present invention are not impaired.

[0060] After TD stretching, the film is subsequently heat-treated. The heat treatment is preferably carried out for 0.2 to 30 seconds at a temperature of at least Tm-60°C and not more than Tm-10°C, where Tm is the melting point of the unstretched sheet. Furthermore, in order to relieve tension in the molecular chains of the polyester film and the resin layer X and increase the uniformity of the order, it is also preferable to carry out a relaxation treatment in the TD direction at a relaxation rate of 1.0% to 5.0% for 0.2 to 10 seconds during the heat treatment.

[0061] Thereafter, the film is gradually cooled uniformly, cooled to room temperature, and wound up on a roll to obtain a laminated polyester film having a resin layer X provided on the surface of the polyester film.

[0062] Next, a preferred use of the laminated polyester film of the present invention will be described. The laminated polyester film of the present invention is preferably used by providing a functional layer on the resin layer X present on at least one of the outermost layers. Furthermore, the laminated polyester film of the present invention is preferably used by providing a functional layer on the resin layer X, removing the resin layer X and the functional layer, and recovering the polyester film for recycling. When resin layers X are present on the outermost layers on both sides of the polyester film, the functional layer may be laminated on both resin layers X, or on only one of them. While another layer may be present between the resin layer X and the functional layer, direct contact between the resin layer X and the functional layer is preferred because it improves the adhesion between the functional layer and the resin layer X and the coatability of the functional layer.

[0063] Examples of the functional layer include a release layer with excellent releasability, a hard coat layer with excellent scratch resistance, and an adhesive layer.

[0064] When a release layer is provided as a functional layer, the release layer can be an alkyd resin-based release agent, a polyolefin-based release agent, a long-chain alkyl group-containing resin-based release agent, a fluorine-based release agent, a silicone-based release agent, or a mixed or copolymer resin-based release agent of an organic and silicone-based material. A film provided with a release layer as a functional layer can be suitably used as a release film for processing. The material to be released from the release film in which a release layer is provided on the laminated polyester film of the present invention is not particularly limited, but a ceramic green sheet, i.e., a dielectric, can be exemplified.

[0065] When a hard coat layer is provided as a functional layer, the hard coat layer can be made of an acrylic resin, a polycarbonate resin, a vinyl chloride resin, a polyester resin, a urethane resin, an actinic ray curable resin, etc. The actinic ray curable resin referred to here is a resin obtained by polymerizing a polyfunctional (meth)acrylic compound monomer with actinic rays, i.e., electromagnetic waves such as ultraviolet rays, electron beams, and radiation that polymerize acrylic vinyl groups.

[0066] When an adhesive layer is provided as a functional layer, the adhesive layer can be made of an acrylic resin, a rubber resin, a vinyl alkyl ether resin, a silicone resin, a polyester resin, a polyamide resin, a urethane resin, a fluorine resin, an epoxy resin, or the like.

[0067] A method for providing a functional layer will be described. The functional layer is provided on the resin layer X of the laminated polyester film of the present invention by coating or lamination. When providing the functional layer by coating, a functional layer-forming coating agent is applied, dried, and cured as necessary. The functional layer-forming coating agent is a dispersion in which the resin components constituting the functional layer are dispersed in a solvent. The coating method is not particularly limited, but examples include reverse coating, spray coating, bar coating, gravure coating, die coating, air knife coating, and doctor knife coating. Among these, die coating is preferred because it can be widely adapted depending on the viscosity of the functional layer-forming coating agent. The drying method is not particularly limited, but examples include hot air blowing and infrared irradiation. The curing treatment refers to a heating treatment or actinic radiation irradiation treatment, the former being performed to cure a thermosetting resin and the latter to cure an actinic radiation-curable resin. When providing the functional layer by lamination, methods such as extrusion lamination and dry lamination can be used.

[0068] Next, a method for removing the resin layer X and the functional layer will be described. By configuring the resin layer X as described above and washing it with an aqueous cleaning solution, it is possible to extract only the polyester film from which the resin layer X and the functional layer have been removed from a used laminated polyester film. The term "used" here refers to a state in which the laminated polyester film of the present invention, which has a functional layer provided as needed in various applications, has exhibited the required functions and is no longer required to exhibit those functions. For example, in the application of a process release film, a state can be exemplified in which a product is placed on the release layer of the laminated polyester film of the present invention, which has a release layer provided as a functional layer, and the product is subjected to the required processing and then peeled off.

[0069] A method for removing the resin layer X and the functional layer will be described using, as an example, a release film for processing in which a release layer is provided as the functional layer. For example, a method may be used in which an aqueous cleaning solution containing water as a main component is applied to the surface of the functional layer side of a used release film containing the laminated polyester film of the present invention, and then a removal member for removing the resin layer X and the functional layer is brought into contact with the surface, and the film is moved in its longitudinal direction relative to the removal member, thereby physically removing them. The temperature of the applied aqueous cleaning solution is preferably Tg°C or higher but not higher than Tg + 100°C, relative to the glass transition temperature Tg of the polyester film in the laminated film in an unstretched state, in order to enhance removability, and more preferably Tg + 10°C or higher but not higher than Tg + 80°C.

[0070] The method for applying the aqueous cleaning liquid to the surface of the used release film may be any method, for example, the cleaning liquid may be applied in the form of droplets using a spray nozzle, or may be applied in a high-pressure or high-temperature state using a high-pressure washer or steam generator. The amount of the cleaning liquid applied is preferably adjusted appropriately depending on the properties and thickness of the resin layer X and functional layer to be removed, but it is preferable to apply the cleaning liquid in an amount sufficient to cover at least a surface area of ​​1 m. ２ The removability is enhanced by setting the volume to 3 ml or more per unit area. Any solvent capable of dissolving the water-soluble resin layer X can be used as the cleaning solution, but water is preferred for reducing environmental impact. The cleaning ability may also be enhanced by adding a surfactant to water as the main component or adjusting the pH to alkaline.

[0071] Examples of the removal member include, but are not limited to, a scraper, fabric, metal plate, rotating brush roll, and water-absorbing roll wrapped with absorbent nonwoven fabric. Any form may be used as long as it can directly contact the film and physically remove the resin layer X and functional layer to be removed. The removal member is preferably pressed directly into contact with the surface of the film bearing the functional layer. Removal is enhanced by moving the film in the longitudinal direction relative to the removal member while keeping the film bent or curved by the removal member. The film in the bent or curved state is preferably adjusted to apply a tension in the longitudinal direction in the range of 10 to 1000 N / m. This allows the film to be pressed firmly against the removal member, thereby enhancing removability. The corners of a scraper or metal plate are more preferred because they allow for localized, stronger pressure against the film surface.

[0072] As described above, the laminated polyester film of the present invention can be used as a release film or other functional laminated film by providing a functional layer on the resin layer X on at least one side of the polyester film. The resin layer X and the functional layer can then be washed and removed, allowing the polyester film to be easily separated into its constituent components. The separated film can be reused as is, or remelted and chipped, and reused as recycled polyester raw material. The recycled raw material can also be used to produce a polyester film again. In particular, the laminated polyester film can be advantageously used in applications in which a release layer is provided on the resin layer X of the laminated polyester film, an object to be released is then provided on the release layer, the object is first peeled off, and then the release layer and resin layer X are removed. Furthermore, because the transparency of the resin layer X remains high even after various processes, the film can also be advantageously used in discriminative analyses (e.g., quantification of residues) that utilize the film's translucency during recycling.

[0073] Next, a preferred embodiment of a method for using a film from which layers X and Y have been removed as recycled raw material will be described. The film from which layers X and Y have been removed using the above-described method is preferably introduced into a crusher with a rotating blade, crushed, then introduced into an extruder, melted, extruded into strands, and cut into pellets to obtain recycled raw material. The melting temperature is preferably 250°C or higher and 300°C or lower to maintain the intrinsic viscosity of the recycled raw material within a preferred range. The extruder may have either a single-screw or twin-screw screw. However, because the film from which layers X and Y have been removed may contain particles or residues from the removal of layers X and Y, twin-screw extruders are preferred from the perspective of uniformly kneading the contained components. Furthermore, filtration through a filter is also preferred during melt extrusion to ensure the amount of components other than polyester is within an appropriate range. The resulting recycled raw material can be reused as raw material for producing the above-mentioned polyester film.

[0074] A preferred embodiment of the laminated polyester film of the present invention is, as described above, a polyester film in which Layer X is provided on at least one side thereof, Layer Y is then provided, and the film is used as a release film for processing, particularly for the production of MLCC, and Layers X and Y are then removed by washing to obtain a polyester film of high purity. The polyester film obtained can be reused as is, or can be remelted and chipped, and used as a recycled raw material for film production and reused as a film.

[0075] [Method of evaluating characteristics] A. Identification of the main skeleton of layer X The components of layer X were dissolved in a solvent, then concentrated and dried. １ The main skeleton of layer X is identified by analyzing with H-NMR and attenuated total reflectance infrared spectroscopy (FT-IR-ATR), and if necessary, qualitative and quantitative analysis is performed using standard substances with known concentrations and components.

[0076] B. Identification of the resin type of layer Y When the components of layer Y were analyzed by total reflectance Fourier transform infrared spectroscopy (FT-IR-ATR), －１ , 1010 cm －１, 785 cm －１ There are three absorption peaks in the vicinity, and the absorption intensities (Abs. peak heights) are all 2920 cm －１ If the absorption intensity is five times or more as high as that of the nearby absorption peak, the layer Y is determined to be made of silicone resin.

[0077] C. Orientation parameter Rxy The orientation parameter Rxy is measured on the surface of the resin layer X side of the laminated polyester film by infrared spectroscopy (FT-IR, ATR method). The sample used was previously conditioned in an atmosphere of room temperature 23°C and relative humidity 65%, and the measurement was performed using a jig that can change the measurement direction while the ATR crystal and the sample were pressed together, with an arbitrarily selected direction as the starting point (0°) and 12 directions up to 165° in 15° increments. The obtained spectrum is divided by the spectrum of polyester film "Lumirror" (registered trademark) #50T60 manufactured by Toray Industries, Inc., which was measured in the same way, to obtain a difference spectrum. Next, in the difference spectrum, the CH of the acrylic main chain is measured. ２ 1446 cm corresponding to the absorption of bending vibration of the group －１ The absorption intensities of the absorption peaks in the vicinity are calculated for each of the 12 directions. －１ The peak of the ring vibration of the aromatic ring in the vicinity is used.

[0078] Next, among the 12 directions, the direction in which the absorption intensity is maximum is 1446 cm －１ The absorption intensity of the absorption peak in the vicinity of Ax is 1446 cm in the direction perpendicular to the direction of the maximum. －１ The absorption intensity of the absorption peak near the center is defined as Ay, and the orientation parameter Rxy is calculated by the following formula: Rxy = (Ax - Ay) / (Ax + Ay) The equipment and conditions used for the measurement are as follows: Equipment: 670-IR (FT-IR manufactured by Varian) Light source: Globar Detector: MCT (Hg-Cd-Te) Resolution: 4 cm －１ Number of integrations: 256 Measurement method: Attenuated total reflection method Accessory: Single reflection type ATR measurement accessory (The Seagull ＴＭ ) ATR crystal: Germanium Incident angle: 0 to 165° measured in 15° increments Polarization: s (vertical polarization).

[0079] D. Hydrophilicity parameter Wx After measuring the surface of the resin layer X side of the laminated polyester film by infrared spectroscopy (FT-IR, ATR method), the spectrum of the polyester film "Lumirror" (registered trademark) #50T60 manufactured by Toray Industries, Inc., measured in the same manner, is divided to obtain a difference spectrum. The sample is used after being conditioned in an atmosphere at room temperature of 23°C and a relative humidity of 65%. Next, in the difference spectrum, the 3000 cm －１ ~3600cm －１ The area of ​​the peak derived from the hydrophilic group was calculated as Aph, and the area of ​​the peak derived from the hydrophilic group at 1446 cm －１ Nearby CH ２ The area of ​​the deformation vibration peak is calculated and designated as Apb, and the hydrophilicity parameter Wx is then calculated using the following formula: Wx = Aph / Apb The apparatus and conditions used for the measurement are as follows: Apparatus: 670-IR (FT-IR manufactured by Varian) Light source: Globar Detector: MCT (Hg-Cd-Te) Resolution: 4 cm －１ Number of integrations: 256 Measurement method: Attenuated total reflection method Accessory: Single reflection type ATR measurement accessory (The Seagull ＴＭ ) ATR crystal: germanium Incident angle: 60° Polarization: none

[0080] E. Contact Angle 100 parts by weight of a silicone release agent manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KS-847T", and 3 parts by weight of a platinum catalyst manufactured by Shin-Etsu Chemical Co., Ltd., trade name "CAT-PL-50T" were dissolved in a mixture of toluene and MEK (methyl ethyl ketone) as a solvent (toluene:MEK mass ratio 1:1) to a solids content of 1.8% by weight. The mixture was applied to the surface of the resin layer X of the laminated polyester film opposite the surface that contacts the polyester film using a bar coater, and dried in an oven at 150 ° C. for 20 seconds to form a release layer with a film thickness of 100 nm. Next, the contact angle was measured using a contact angle meter DM500 manufactured by Kyowa Interface Science Co., Ltd. and the attached analysis software FAMAS in the following manner. The laminated polyester film was conditioned in an atmosphere at room temperature of 23 ° C. and relative humidity of 65%. Then, under the same atmosphere, ethanol is dropped onto the surface of Layer Y of the laminated polyester film, and the contact angle is measured for 20 seconds, starting from the time when the droplet makes contact with the sample surface as 0 seconds. Five measurements are taken at different locations, and the average values ​​of the five contact angles after 1 second and 20 seconds are calculated. The average value of the contact angle after 1 second is designated Ey(1), and the average value of the contact angle after 20 seconds is designated Ey(20).

[0081] F. Glass Transition Temperature The glass transition temperature (°C) is measured in accordance with JIS K-7121 (1987) using a differential scanning calorimeter "Robot DSC-RDC220" manufactured by Seiko Instruments Inc. The glass transition temperature is calculated at the stepwise change portion of the glass transition according to the method described in "9.3 Method for Determining Glass Transition Temperature (1) Midpoint Glass Transition Temperature Tmg" of JIS K-7121 (1987). The glass transition temperature of the resin layer X is measured by physically peeling the resin layer X from the surface of the laminated polyester film, collecting it, dissolving it in water, filtering off any water-insoluble foreign matter, and then vacuum-drying it until the moisture content is 50 ppm or less.

[0082] G. Weight-average molecular weight Measurement was performed using a GPC "GPC-8020" manufactured by Tosoh Corporation under the following conditions: Column: One guard column PWXL and two GMPWXL manufactured by Tosoh Corporation (temperature 40°C) Eluent: 0.5 mol / l acetate buffer (pH = 4.7) Measurement temperature: 40°C Detector: differential refractometer Calibration standard reagent: polyethylene oxide.

[0083] For the resin layer X, the film was immersed in a 0.5 mol / l acetate buffer solution, heated to a temperature of 70° C., and extracted with stirring, and the weight average molecular weight of the extract was determined.

[0084] H. Crack Resistance A bending test is performed using an MIT folding endurance tester manufactured by Mize Testing Instruments Co., Ltd. Specifically, a laminated polyester film is sampled into a strip shape with a width of 15 mm, and a bending test is performed 100 times under the following conditions: load: 9.8 N, speed: 175 times / min, radius of curvature (R): 0.38 mm, gap: 0.25 mm, bending angle: 135° to the left and right. After the bending test, the surface of the resin layer X side of the laminated polyester film at the bent portion is observed at a magnification (1000x) using a microscope (VHX-5000) manufactured by Keyence Corporation, and the crack resistance is evaluated according to the following criteria: A: No wrinkles or cracks were observed within a 200 μm square field of view. B: One or more but less than five wrinkles or cracks were observed within a 200 μm square field of view. C: Five or more wrinkles or cracks were observed within a 200 μm square field of view, or cracks occurred during stretching, making film formation impossible.

[0085] I. Solvent Resistance The surface of the resin layer X side of the laminated polyester film was rubbed using a Gakushin-type testing machine (compliant with JIS L 0849 (2013)) manufactured by Daiei Scientific Instruments Co., Ltd. A cotton cloth (No. 3 gold cloth) impregnated with ethanol was used as the rubber for the rub treatment, and the surface was rubbed back and forth 30 times with a load of 1 kg. Next, the contact angle of ethanol was measured for the rubbed area and the nearby unabraded area using the same method as in E above. Specifically, the contact angle was measured using a contact angle meter DM500 manufactured by Kyowa Interface Science Co., Ltd. and the accompanying analysis software FAMAS in the following manner. The laminated polyester film was conditioned in an atmosphere at room temperature of 23°C and a relative humidity of 65%. Then, in the same atmosphere, ethanol was dropped onto the surface of the measurement area, and the contact angle was measured for 20 seconds, with the time when the droplet contacted the sample surface being set to 0 seconds. The measurement was performed five times using different samples, and the average of the five contact angles after 20 seconds was calculated. The above average value was calculated for both the abraded area and a nearby unabraded area, and the absolute value of the difference between the two average values ​​obtained was defined as the difference in contact angle, and solvent resistance was evaluated according to the following criteria: A: The difference in contact angle between the abraded area and the unabraded area is less than 1°; B: The difference in contact angle between the abraded area and the unabraded area is 1° or more but less than 3°; C: The difference in contact angle between the abraded area and the unabraded area is 3° or more.

[0086] J. Removability 100 parts by mass of Shin-Etsu Chemical Co., Ltd.'s product name "KS-847T" and 3 parts by mass of a platinum catalyst, Shin-Etsu Chemical Co., Ltd.'s product name "CAT-PL-50T," were dissolved in a mixed solution of toluene and MEK as a solvent (toluene:MEK mass ratio 1:1) to a solids content of 1.8% by mass. This was then applied to the side of the resin layer X of the laminated polyester film opposite the side that contacts the polyester film using a bar coater, and dried in an oven at 150°C for 20 seconds to form a release layer with a film thickness of 100 nm. The laminated polyester film on which the release layer was formed was prepared in the form of a roll with a width of 50 mm.

[0087] Next, the prepared roll is set in the removal device 101 shown in Figure 1 from the upstream side of the conveying mechanism, and is conveyed at a conveying speed of 50 m / min by the driving devices 5 and 6 while applying a tension of 20 N / m in the longitudinal direction. In the removal mechanism 11, steam 8 heated to 80°C is sprayed from the spray nozzle 7 onto the surface of the release layer to form a film with a surface area of ​​1 m. ２ After one second, a stainless steel plate-shaped scraper 10 is pressed against the surface perpendicular to the longitudinal direction of the film to carry out a removal treatment.

[0088] After the removal treatment, the film is pretreated by ashing and alkali fusion, and then the silicone (Si) element content is quantified by inductively coupled plasma atomic emission spectroscopy (ICP-AES), and the removability is evaluated according to the following criteria: A: Si element content less than 50 ppm B: Si element content 50 ppm or more but less than 100 ppm C: Si element content 100 ppm or more

[0089] K. Overall Evaluation Based on the evaluation results of H. Cracking Resistance, I. Solvent Resistance, and J. Removability, an overall evaluation is made according to the following criteria: A: Cracking resistance, solvent resistance, and removability are all rated A B: One of the cracking resistance, solvent resistance, and removability ratings is B, and the remaining two are A C: Two or more Bs are given in the cracking resistance, solvent resistance, and removability ratings, and no C is given D: One of the cracking resistance, solvent resistance, and removability ratings is C.

[0090] L. MLCC Fabrication A multilayer ceramic capacitor (MLCC) with Ni as the internal electrode and Ag as the external electrode is fabricated through the following steps (1) to (5). (1) A release agent, coating material J (described below), is applied to a laminated polyester film having layers X and Y by die coating to a dry thickness of 1.0 μm. 15 seconds after application, the coating is dried for 2 minutes in an oven at 100°C and an air velocity of 5 m / s. (2) Ni paste is screen-printed onto the resulting ceramic sheet-attached laminated polyester film to form an electrode-forming sheet with internal electrodes for capacitance formation. (3) A predetermined number of electrode-forming sheets are stacked, and ceramic sheets (external layer sheets) without electrodes are stacked on both the top and bottom surfaces of the electrode-forming sheets. These sheets are then crimped together to form a laminate in which one end of each internal electrode is alternately extended to the end face on different sides. Here, when stacking the electrode-forming sheets and external layer sheets, these sheets are peeled from the laminated polyester film as they are stacked. (4) The laminated body is cut into green elements of a predetermined size using a dicer, and the green elements are then debindered and fired to form ceramic elements. Debindering is performed by heat-treating the green elements in a nitrogen atmosphere. Firing is performed by heating the green elements to a predetermined temperature in a weakly reducing atmosphere. (5) A conductive paste containing Ag as a conductive component is applied to both ends of the formed ceramic element, and the resulting paste is baked to form external electrodes that are electrically connected to the internal electrodes.

[0091] The present invention will be described below with reference to examples, but the present invention is not necessarily limited to these examples.

[0092] [Polymerization of PET (Polyester A)] Terephthalic acid and ethylene glycol were polymerized in a conventional manner using antimony trioxide as a catalyst to obtain melt-polymerized PET. The resulting PET (Polyester A) had a glass transition temperature of 75°C, a melting point of 255°C, an intrinsic viscosity of 0.62, and a terminal carboxyl group content of 20 equivalents / ton.

[0093] [Monomer 1] Acrylamide (Wako First Grade, molecular weight 71.08) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used.

[0094] [Monomer 2] Acrylic acid (Wako special grade, molecular weight 72.06) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used.

[0095] [Monomer 3] 4-acryloylmorpholine (Wako First Grade, molecular weight 141.17) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used.

[0096] [Monomer 4] 2-Methoxyethyl acrylate (Wako First Grade, molecular weight 130.14) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used.

[0097] [Monomer 5] 2-[2-(2-methoxyethoxy)ethoxy]ethyl acrylate (molecular weight 218.25) manufactured by Tokyo Chemical Industry Co., Ltd. was used.

[0098] [Coating material A] A four-neck flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen gas inlet tube was charged with 26 parts by weight of monomer 1, 39 parts by weight of monomer 3, 36 parts by weight of monomer 4, and 270 parts by weight of ion-exchanged water, and the oxygen in the reaction system was removed through nitrogen gas.Next, the system was heated to 40 ° C, and 0.25 parts by weight of ammonium persulfate and 0.15 parts by weight of sodium hydrogen sulfite were added as a polymerization initiator under stirring, and the temperature was raised to 85 ° C, and the viscosity of the reaction solution (25 ° C, solid content concentration 20% by weight equivalent) reached 150 mPa s, and the polymerization was terminated and cooled, and further diluted with ion-exchanged water to obtain a polymer aqueous solution with a pH of 5.5, a solid content of 20.0% by weight, and a viscosity of 150 mPa s.The obtained polymer aqueous solution was diluted with ion-exchanged water to a solid content concentration of 2.6% by weight, and a coating material A was obtained. The weight average molecular weight Mw of the resin contained in the coating material was 200,000, and the glass transition temperature was 120°C.

[0099] [Coating Material B] Coating material B with a solids concentration of 2.6% by mass was obtained in the same manner as coating material A, except that the raw materials charged in the flask were changed to 49 parts by mass of monomer 1, 45 parts by mass of monomer 3, 7 parts by mass of monomer 4, and 270 parts by mass of ion-exchanged water. The weight-average molecular weight Mw of the resin contained in the coating material was 200,000, and the glass transition temperature was 170 ° C.

[0100] [Coating Material C] Coating Material C with a solids concentration of 2.6% by mass was obtained in the same manner as Coating Material A, except that the raw materials charged in the flask were changed to 39 parts by mass of Monomer 1, 42 parts by mass of Monomer 3, 19 parts by mass of Monomer 4, and 270 parts by mass of ion-exchanged water. The weight-average molecular weight Mw of the resin contained in the coating material was 200,000, and the glass transition temperature was 145 ° C.

[0101] Coating Material D: Coating Material D was prepared in the same manner as Coating Material A, except that the polymerization was terminated when the viscosity of the reaction solution (25°C, solids concentration 20% by weight) reached 10 mPa·s. The weight-average molecular weight Mw of the resin contained in the coating material was 20,000, and the glass transition temperature was 120°C.

[0102] [Coating Material E] Coating Material D with a solids concentration of 2.6% by mass was obtained in the same manner as Coating Material A, except that in the preparation of Coating Material B, polymerization was terminated when the viscosity of the reaction solution (25°C, solids concentration 20% by mass equivalent) reached 500 mPa s. The weight-average molecular weight Mw of the resin contained in the coating material was 700,000 and the glass transition temperature was 170°C.

[0103] [Coating Material F] Coating material F with a solids concentration of 2.6% by mass was obtained in the same manner as coating material A, except that the raw materials charged into the flask were changed to 26 parts by mass of monomer 2, 38 parts by mass of monomer 3, 35 parts by mass of monomer 4, and 270 parts by mass of ion-exchanged water. The weight-average molecular weight Mw of the resin contained in the coating material was 200,000, and the glass transition temperature was 110 ° C.

[0104] [Coating Material G] The raw materials charged into the flask were changed to 49 parts by weight of Monomer 1, 45 parts by weight of Monomer 3, 7 parts by weight of Monomer 5, and 270 parts of ion-exchanged water, and the polymerization was terminated when the viscosity of the reaction solution (25 ° C, solid content concentration 20 mass %) reached 500 mPa s. Except for this, coating material G with a solid content concentration of 2.6 mass % was obtained in the same manner as coating material A. The weight average molecular weight Mw of the resin contained in the coating material was 700,000, and the glass transition temperature was 160 ° C.

[0105] [Coating Material H] Coating Material H with a solids concentration of 2.6% by mass was obtained in the same manner as Coating Material A, except that the raw materials charged into the flask were changed to 6 parts by mass of Monomer 1, 33 parts by mass of Monomer 3, 61 parts by mass of Monomer 4, and 270 parts by mass of ion-exchanged water. The weight-average molecular weight Mw of the resin contained in the coating material was 200,000, and the glass transition temperature was 80 ° C.

[0106] [Coating Material I] Coating material I with a solids concentration of 2.6% by mass was obtained in the same manner as coating material A, except that the raw materials charged in the flask were changed to 67 parts by mass of monomer 1, 33 parts by mass of monomer 3, and 270 parts of ion-exchanged water. The weight-average molecular weight Mw of the resin contained in the coating material was 200,000, and the glass transition temperature was 185 ° C.

[0107] [Coating material J] 100 parts by mass of barium titanate (manufactured by Fuji Titanium Industry Co., Ltd., trade name HPBT-1), 10 parts by mass of polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., trade name BL-1), 5 parts by mass of dibutyl phthalate, and 60 parts by mass of toluene-ethanol (mass ratio 30:30) were mixed and dispersed in a jet mill for 24 hours, and then filtered to prepare a paste-like dielectric paste, and coating material J was obtained.

[0108] (Example 1) Polyester A was vacuum dried at 160°C for 3 hours, then charged into an extruder, melted at 280°C, and extruded through a die onto a casting drum with a surface temperature of 25°C to produce an unstretched sheet. Subsequently, the sheet was preheated with a group of heated rolls, stretched 3.5 times in the longitudinal direction (MD direction) at a temperature of 90°C, and then cooled with a group of rolls with a temperature of 25°C to obtain a uniaxially stretched film.

[0109] The resulting uniaxially stretched film was coated with coating material A to a coating thickness of approximately 10 μm. Subsequently, both ends of the coated uniaxially stretched film in the width direction were gripped with clips and introduced into the preheating zone. The ambient temperature of the preheating zone was 90 ° C to 100 ° C, and the film was continuously stretched 3.6 times in the width direction (TD direction) perpendicular to the longitudinal direction in a 105 ° C stretching zone at a stretching rate of 60% / sec, followed by heat treatment for 10 seconds in a 230 ° C heat treatment zone to obtain a laminated polyester film having a resin layer X. The thickness of the resulting laminated polyester film was 30 μm, and the thickness of the resin layer X was 100 nm. The properties of the resulting laminated polyester film are shown in Table 1. It had excellent crack resistance, solvent resistance, and removability.

[0110] (Example 2) A laminated polyester film was obtained in the same manner as in Example 1, except that the coating material was changed to coating material B. The properties of the obtained laminated polyester film are shown in Table 1. The film had excellent solvent resistance and removability, and good crack resistance.

[0111] (Example 3) A laminated polyester film was obtained in the same manner as in Example 1, except that the coating material was changed to coating material C. The properties of the obtained laminated polyester film are shown in Table 1. The crack resistance, solvent resistance, and removability were all excellent.

[0112] (Example 4) A laminated polyester film was obtained in the same manner as in Example 1, except that the coating material was changed to coating material C and the stretching ratio in the TD direction was changed to 3.0 times. The properties of the obtained laminated polyester film are shown in Table 1. The film had excellent crack resistance and removability, and good solvent resistance.

[0113] (Example 5) A laminated polyester film was obtained in the same manner as in Example 1, except that the coating material was changed to coating material C and the stretching speed in the TD direction was changed to 10% / sec. The properties of the obtained laminated polyester film are shown in Table 1. The film had excellent crack resistance and removability, and good solvent resistance.

[0114] (Example 6) A laminated polyester film was obtained in the same manner as in Example 1, except that the coating material was changed to coating material D. The properties of the obtained laminated polyester film are shown in Table 1. The crack resistance, solvent resistance, and removability were good.

[0115] (Example 7) A laminated polyester film was obtained in the same manner as in Example 1, except that the coating material was changed to Coating Material E. The properties of the obtained laminated polyester film are shown in Table 1. The film had excellent solvent resistance, and good crack resistance and removability.

[0116] (Example 8) A laminated polyester film was obtained in the same manner as in Example 1, except that the coating material was changed to coating material F. The properties of the obtained laminated polyester film are shown in Table 1. The film had excellent solvent resistance and removability, and good crack resistance.

[0117] (Example 9) A laminated polyester film was obtained in the same manner as in Example 1, except that the coating material was changed to coating material G. The properties of the obtained laminated polyester film are shown in Table 1. The film had excellent crack resistance and solvent resistance, and was easily removable.

[0118] Furthermore, for each example, an MLCC could be produced in the same manner as in the production of an L. MLCC.

[0119] (Comparative Example 1) A laminated polyester film was obtained in the same manner as in Example 1, except that the coating material was changed to coating material H. The properties of the obtained laminated polyester film are shown in Table 1. The crack resistance was excellent, but the solvent resistance and removability were poor.

[0120] (Comparative Example 2) An attempt was made to obtain a laminated polyester film in the same manner as in Example 1, except that the coating material was changed to coating material I. However, the resin layer X could not follow the stretching in the TD direction, and coating cracks occurred during stretching, making it impossible to form the resin layer X.

[0121]

[0122] The laminated polyester film of the present invention is a laminated polyester film having an acrylic water-soluble resin layer formed on a polyester substrate, and has both durability during use as a process film and removability that allows easy removal with an aqueous cleaning solution after use, so that the polyester film alone can be recovered and easily reused after use. In particular, when a release layer is applied as a functional layer, the film can be suitably used as a release film in the manufacturing process of multilayer ceramic capacitors (MLCCs) using a dielectric as the release target.

[0123] REFERENCE SIGNS LIST 1 Laminated polyester film having layer Y (film before removal treatment) 2 Film after removal treatment 3 Unwinding device 4 Winding device 5, 6 Driving device 7 Spray nozzle 8 Steam 10 Plate-shaped scraper a Film conveying direction 11 Removing mechanism 101 Removing device

Claims

1. A laminated polyester film having a water-soluble resin layer X on at least one side of a polyester film, the resin layer X having an acrylic main skeleton having a monomer unit represented by chemical formula (1) or (2), wherein, when the glass transition temperature of the polyester film is Tg1 and the glass transition temperature of the resin layer X is Tg2, Tg2-Tg1 is 20°C or higher and 100°C or lower. R １ is a hydrogen atom or a methyl group, R ２ represents any functional group. R ３ is a hydrogen atom or a methyl group, R ４ and R ５ represents any functional group.

2. A laminated polyester film having a water-soluble resin layer X on at least one side of a polyester film, the resin layer X having an acrylic main skeleton having a monomer unit represented by chemical formula (1) or (2), the orientation parameter Rxy of the resin layer X represented by the following formula being 0.02 or more and less than 1.

00. Rxy=(Ax-Ay) / (Ax+Ay) Ax: CH of the acrylic main chain measured by infrared spectroscopy ２ CH of the acrylic main chain in the direction in which the bending vibration is maximum ２ Absorption intensity of bending vibration Ay: CH of the acrylic main chain in a direction perpendicular to the direction of maximum ２ Bending vibration absorption strength R １ is a hydrogen atom or a methyl group, R ２ represents any functional group. R ３ is a hydrogen atom or a methyl group, R ４ and R ５ represents any functional group.

3. The laminated polyester film according to claim 1 or 2, wherein the hydrophilic parameter Wx of the resin layer X, represented by the following formula, is 5 or more and 15 or less. Wx = Aph / Apb Aph: 3000 cm measured by infrared spectroscopy －１ ~3600cm －１ Apb: Area of ​​the hydrophilic group-derived peak at 1446 cm measured by infrared spectroscopy －１ Nearby CH ２ Bending vibration peak area 4. The laminated polyester film according to claim 1 or 2, wherein the resin layer X is extracted with a 0.5 mol / l acetate buffer solution, and the weight average molecular weight Mw of the extract calculated in terms of polyethylene oxide by gel permeation chromatography (hereinafter, GPC) is 20,000 or more and 500,000 or less.

5. The laminated polyester film according to claim 1 or 2, further comprising a layer Y on the opposite side of the resin layer X from the side in contact with the polyester film, the layer Y having an ethanol contact angle Ey (°) that satisfies the following formula: |Ey(1)-Ey(20)|≦5.0 Ey(1): contact angle 1 second after ethanol comes into contact with layer Y Ey(20): contact angle 20 seconds after ethanol comes into contact with layer Y 6. The laminated polyester film according to claim 5, wherein a release layer is provided on the surface of layer Y opposite to the surface in contact with layer X, and the film is used for releasing the release layer from layer Y.

7. The laminated polyester film according to claim 6, which is used in an application in which, after the release layer is peeled off from the layer Y, the layers X and Y are further removed.

8. The laminated polyester film according to claim 7, which is used for reusing the laminated polyester film from which the layer X and the layer Y have been removed.

9. The laminated polyester film according to claim 6, wherein the release layer is a ceramic sheet containing barium titanate as a main component.

10. A multilayer ceramic chip capacitor obtained by laminating the ceramic sheets released from the laminated polyester film according to claim 1 or 2, further comprising a silicone resin layer Y on the surface of the layer X opposite to the surface in contact with the polyester film, and a ceramic sheet containing barium titanate as a main component on the surface of the layer Y opposite to the surface in contact with the layer X.

11. A method for producing a polyester film, comprising the steps of: using a laminated polyester film according to claim 1 or 2 having at least a release layer, a silicone resin layer Y, the layer X, and a polyester film in this order; peeling the release layer from the layer Y; removing layers Y and X from the film from which the release layer has been peeled off; producing recycled raw material from the film from which the release layer, layers Y, and layers X have been removed; and producing a film using the recycled raw material.

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