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

Abstract

To provide a laminated polyester film which has high recyclability and excellent quality stability.SOLUTION: A laminated polyester film has a water-soluble resin layer X containing acryl having a repeating unit represented by chemical formula (1) or chemical formula (2) as a main skeleton, on at least one surface of the polyester film, and satisfies the following (1) and (2). (1) An orientation parameter Rxy of a layer X represented by Expression Rxy=(Ax-Ay) / (Ax+Ay), which is measured by total reflection measurement Fourier transform infrared spectroscopy (FT-IR-ATR), is 0.02 or more and less than 1.00. Ax: absorption intensity in a direction with maximum CH deformation vibration. Ay: absorption intensity in a direction +90° from the maximum direction. (2) A hydrophilicity parameter Wx of a layer X represented by Expression Wx=Aph / Apb, which is measured by total reflection measurement Fourier transform infrared spectroscopy (FT-IR-ATR), is 2 or more and 10 or less. Aph: area of a peak derived from a hydrophilic group at 3,000 cm-1 to 3,600 cm-1. Apb: area of a peak of CH deformation vibration of a CH2 group at 1,446 cm-1.SELECTED DRAWING: None

Description

[Technical Field]

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

[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 also peeling off the release layer made of silicone laminated on the polyester film, making it possible to recycle only the polyester film. Patent Document 2 also discloses a technology in which acrylic is used as a water-soluble release functional layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-050681 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-131484 Summary of the Invention [Problem to be solved by the invention]

[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 undergoes crystallization when placed under certain environments, resulting in the formation of crystallization irregularities, leaving room for improvement in terms of reducing irregularities in surface properties.

[0008] On the other hand, if an amorphous resin, acrylic, is used as a water-soluble release functional layer instead of polyvinyl alcohol in order to suppress whitening due to crystallization and uneven surface properties, the uneven properties caused by the progression of crystallization as described above can be suppressed, but because it is amorphous, the functional resin applied as an overcoat to the release functional layer is likely to penetrate between the molecular chains of the release functional layer resin and act on it, which can cause changes in physical properties over time and impair quality stability.

[0009] Therefore, an object of the present invention is to provide a laminated polyester film with a release functional layer that is excellent in quality stability. [Means for solving the problem]

[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 a water-soluble resin layer X on at least one side of the polyester film, the resin layer X having an acrylic main skeleton having a repeating unit represented by chemical formula (1) or chemical formula (2), and the laminated polyester film satisfies the following (1) and (2): (1) Attenuated Total Reflectance (FT-IR)-Atmospheric Resonance (ATR) Fourier Transform Infrared Spectroscopy (FT-IR-ATR) xy =(Ax -A y ) / (A x +A y ) is the orientation parameter R of layer X. xy is greater than or equal to 0.02 and less than 1.00. A x : Absorption intensity in the direction where the CH bending vibration is maximum A y : Absorption intensity in the direction of maximum CH bending vibration +90° The absorption intensity was 1446 cm , which corresponds to the absorption of the CH bending vibration of the CH group of the acrylic main chain, in the difference spectrum after subtracting the contribution of the polyester film spectrum. -1 This refers to the absorption intensity (Abs., peak height) of the absorption peak at 1506 cm -1 The peak of the ring vibration of the aromatic ring at 1446 cm is used as the reference peak, and the absorption intensity of the reference peak is normalized to 1. -1 Calculate the relative intensity of the absorption peak.

[0011] The direction in which the CH bending vibration is maximum is the direction in which the absorption intensity (relative intensity to the reference peak) is maximum among 12 directions up to 165° in 15° increments, starting from an arbitrarily selected direction in the film plane (0°). (2) Attenuated Total Reflectance (FT-IR-ATR) Fourier Transform Infrared Spectroscopy (FT-IR-ATR) x = A ph / A pb The hydrophilicity parameter W of layer X is expressed as x is greater than or equal to 2 and less than or equal to 10. A ph :3000cm -1 ~3600cm -1 Area of ​​the peak derived from hydrophilic groups A pb :1446cm -1 The area of ​​the CH bending vibration peak of the CH2 group

[0012] [ka]

[0013] R1 represents a hydrogen atom or a methyl group, and R2 represents an arbitrary functional group.

[0014] [ka]

[0015] R3 represents a hydrogen atom or a methyl group, and R4 and R5 represent any functional group. [II] A silicone resin layer Y is further provided on the surface of the layer X opposite to the surface in contact with the polyester film, and the contact angle C of formamide on the surface of the layer Y is i The laminated polyester film according to [I], wherein (°) satisfies the following formula: 90≦C i ≦110 [III] The laminated polyester film according to [II], wherein the surface of the layer Y satisfies the following conditions:

[0016] -5≦C t -C i ≦5 C i : Contact angle of formamide on the surface of layer Y (°) C t : Contact angle (°) of formamide on the surface of Layer Y after moist heat treatment (50°C, 90% RH, 24 hours) [IV] The laminated polyester film according to [II] or [III], wherein the amount of dimethylsiloxane transferred to the layer Y, as determined by the following measurement method, satisfies the following relationship: T t >T i T i : Amount of dimethylsiloxane transferred from untreated film T t : Amount of dimethylsiloxane transferred after moist heat treatment (50°C, 90% RH, 24 hours) (Measurement method) In total reflectance Fourier transform infrared spectroscopy (FT-IR-ATR), an ATR crystal is pressed against the surface of layer Y of the laminated polyester film sample, and after 10 minutes the pressure is released. A spectrum is then collected in this state, and spectral information on the components transferred from layer Y to the surface of the ATR crystal is obtained. Next, from the obtained spectrum, the peak at 1263 cm -1 CH bending vibration peak, 1099 cm -1 Si-O-Si stretching vibration peak, 1022 cm -1 The absorption intensities (Abs., peak heights) of the three absorption peaks of the Si-O-Si stretching vibration peaks are calculated, and the average value is taken as the amount of dimethylsiloxane transferred. [V] A laminated polyester film according to any one of [II] to [IV], which is used for release purposes by providing a release layer on the surface of Layer Y opposite to the surface in contact with Layer X and peeling the release layer from Layer Y. [VI] The laminated polyester film according to [V], which is used in an application in which, after the release layer is peeled from the layer Y, the layer X and the layer Y are further removed. [VII] The laminated polyester film according to [VI], which is used for reusing the laminated polyester film from which the layer X and the layer Y have been removed. [VIII] The laminated polyester film according to [V], wherein the release layer is a ceramic sheet containing barium titanate as a main component. [IX] A multilayer ceramic chip capacitor obtained by laminating the ceramic sheet released from the laminated polyester film according to [I], further comprising a silicone resin layer Y on the surface of the layer X opposite to the surface that contacts 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 that contacts the layer X. [X] A method for producing a polyester film, comprising the steps of: using the laminated polyester film according to [I], which has at least a release layer, a silicone resin layer Y, a 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; producing recycled raw materials from the film from which the release layer, layer Y, and layer X have been removed; and producing a film using the recycled raw materials. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a laminated polyester film having excellent quality stability, in which an acrylic water-soluble resin layer is formed as a release functional layer on a polyester substrate. DETAILED DESCRIPTION OF THE INVENTION

[0018] A preferred embodiment of the present invention will be described in detail below with reference to a specific example.

[0019] 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.

[0020] 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 dicarboxylic acid components constituting such polyesters 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.

[0021] 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 PET in which isophthalic acid or naphthalenedicarboxylic acid is copolymerized as part of the dicarboxylic acid component, and PET in which cyclohexanedimethanol, spiroglycol, or diethylene glycol is copolymerized as part of the diol component.

[0022] In the present invention, acrylic refers to a polymer having a repeating unit represented by chemical formula (1) or chemical formula (2). The moiety represented by -COOR2 in chemical formula (1) includes salts such as metal salts of carboxylic acids and ammonium salts of carboxylic acids, and the moiety represented by -CONR4R5 in chemical formula (2) includes quaternary ammonium salts formed by reaction with a quaternizing agent.

[0023] [ka]

[0024] [ka]

[0025] When all repeating units of the acrylic skeleton are taken as 100 mol %, R1 and R3 preferably account for at least 70 mol % or more of hydrogen atoms from the viewpoint of water solubility, and more preferably 80 mol % or more.

[0026] The water-soluble resin layer X of the present invention has an acrylic main skeleton, and when expressed as a main skeleton in this specification, it means that the proportion of this skeleton in the entire skeleton constituting the resin is 80 mol % or more, more preferably 90 mol % or more.

[0027] The water-soluble resin layer X having an acrylic main skeleton can control the water solubility, hydrophilicity, and glass transition temperature of the acrylic by the side chains introduced into R2, R4, R5, etc., and specifically, the control can be achieved by changing the types and ratios of the hydrophilic monomer component and the hydrophobic monomer component used during polymerization.

[0028] 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. Among the above, various organic acid monomers may be their sodium salts, potassium salts, or the like, and among 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 alone or in combination of two or more.

[0029] Examples of hydrophobic monomer components used in acrylic polymerization include various acid esters, which 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-alkyl acrylamides, N-alkyl methacrylamides, N,N-dialkyl acrylamides, N,N-dialkyl methacrylamides, N-isopropyl acrylamide, and 4-acryloylmorpholine. These hydrophobic monomers may be used alone or in combination of two or more.

[0030] 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 crosslinkable vinyl monomers 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 can be used alone or in combination of two or more.

[0031] In the present invention, the resin layer X being water-soluble is defined as follows. 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. 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, the resin layer X is defined as being water-soluble. 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.

[0032] In the present invention, the acrylic preferably contains units derived from the hydrophilic monomer in a proportion of less than 60 mol% of all monomer units to enhance the quality stability of layer X, more preferably less than 50 mol%. Furthermore, nonionic monomers that do not have ionic properties are preferred over anionic monomers such as organic acid monomers or cationic monomers having a tertiary amino group in order to enhance the quality stability of the hydrophilic monomer, with amide monomers such as acrylamide and methacrylamide being particularly preferred. Furthermore, it is particularly preferred that more than half of all the hydrophilic monomers mentioned above are nonionic hydrophilic monomers in order to enhance the quality stability of layer X. That is, in the resin of resin layer X of the present invention, the proportion of nonionic hydrophilic monomers in all monomer units is preferably 15 mol% or more and 60 mol% or less.

[0033] The laminated polyester film of the present invention is characterized in that the absorption intensity of the CH bending vibration of the acrylic main chain in the direction in which the CH bending vibration of the CH group of the acrylic main chain is maximum, as measured by Fourier transform infrared spectroscopy (FT-IR-ATR) for the resin layer X, is A x , the absorption intensity of the CH bending vibration of the acrylic main chain in the direction perpendicular to the direction of the maximum absorption is A y In this case, the orientation parameter R is expressed by the following formula 1.xy is preferably 0.02 or more and less than 1.00. R xy =(A x -A y ) / (A x +A y )...Equation 1 R xy When R is 0.02 or more, the orderliness of the molecular chain arrangement of the acrylic, which is an amorphous resin, is increased, and even if it is exposed to moisture for a long time or is in continuous contact with a topcoat layer of a different component, the quality of the resin layer X can be prevented from changing, resulting in good quality stability. xy In principle, R never exceeds 1.00. xy More preferably, it is 0.08 or more and less than 1.00. The measurement by attenuated total reflectance Fourier transform infrared spectroscopy (FT-IR-ATR) is carried out by the method described in the Examples.

[0034] R xy As a means for achieving a value of 0.02 or more and less than 1.00, an in-line coating method can be used 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.

[0035] Also, R xy In order to bring the value into a more preferable range, the film thickness of the coating material, the stretching speed, the stretching ratio, the hydrophilicity of the water-soluble resin, etc. can be adjusted 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 falls within a certain range.

[0036] The laminated polyester film of the present invention has a 3000 cm reflection wavelength measured by Fourier transform infrared spectroscopy (FT-IR-ATR) for the resin layer X. -1 ~3600cm -1The area of ​​the peak derived from the hydrophilic group is A ph , 1446cm -1 The area of ​​the CH bending vibration peak of the CH2 group is A pb In this case, the hydrophilicity parameter W x is preferably 2 or more and 10 or less.

[0037] W x = A ph / A pb ...Formula 2 W x When W is 2 or more and 10 or less, the quality of the resin layer X can be further prevented from changing even when exposed to moisture for a long period of time or when in continuous contact with an overcoat layer of a different component, resulting in good quality stability. x If W is less than 2, it becomes difficult to control the orientation parameters of the resin layer X by stretching, and the organic solvent may easily penetrate into the resin layer X, which may impair the quality stability. x If W exceeds 10, the hydrophilicity of the resin layer X becomes too high, and if the resin layer X is exposed to moisture for a long time, the quality of the resin layer X may change due to the influence of water molecules that have penetrated into the resin, and the quality stability may be impaired. x is more preferably 3 or more and 9 or less. x As a means for achieving a ratio of 2 or more to 10 or less, there is a method of adjusting the ratio of hydrophilic components among the components constituting the acrylic resin within a specific range.

[0038] From the viewpoint of quality stability, it is more preferable that the hydrophilicity parameter is 7 or less and / or the orientation parameter is 0.08 or more.

[0039] 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 is preferably 10,000 or more and 1,000,000 or less. The weight-average molecular weight Mw is calculated as polyethylene oxide equivalent by gel permeation chromatography (hereinafter, GPC). By setting the Mw within the above range, the quality stability and water solubility of the layer X can be improved. The Mw is more preferably 50,000 or more and 700,000 or less. A method for achieving an Mw of 10,000 or more and 1,000,000 or less includes, for example, measuring the viscosity of the polymerization solution during resin polymerization and stopping the polymerization reaction by adding a polymerization terminator, diluting the polymerization solution, or adjusting the amount of monomer added when a predetermined viscosity is reached, thereby adjusting the Mw within the target range.

[0040] The laminated polyester film of the present invention further comprises a silicone resin layer Y on the surface of the layer X opposite to the surface in contact with the polyester film, and the contact angle C of formamide on the surface of the layer Y is i It is preferable that (°) satisfies the following formula 3. 90≦C i ≦110...Equation 3 C i By making the contact angle between 90° and 110°, it is possible to prevent layer Y from being affected by layer X and causing quality changes over time, and the quality stability of the laminated film made up of layer X and layer Y is improved. Among the reagents used to measure surface free energy, formamide has a balance between the dispersion component and polar component of the surface free energy similar to that of water-soluble acrylic resin, so the influence of layer X can be sensitively detected by the value of the contact angle. Specifically, the stronger the influence of layer X is, the higher the C i The value of C tends to be small. i The fact that the value of is strongly affected by layer X means that the inherent performance of layer Y is difficult to demonstrate, and depending on the usage environment, the quality stability of the laminated film made up of layer X and layer Y may become unstable. Note that layer Y is a silicone resin, so C i The upper limit of the angle is practically 110° due to the influence of the surface tension of the silicone resin. iis more preferably 97° or more and 103° or less. Methods for making layer Y satisfy formula 3 include reducing the proportion of highly hydrophilic skeletons in the material constituting layer X, or forming layer X by an in-line coating method, which simultaneously stretches and forms a film on a polyester film. When forming layer Y on layer X, a coating material containing an organic solvent is applied, and it is believed that the organic solvent penetrates into layer X, causing layer Y to be affected by the underlying layer X. Therefore, controlling the hydrophilicity of layer X or forming layer X by an in-line coating method can suppress the penetration of the organic solvent into layer X, making layer Y less susceptible to the influence of layer X, which is believed to improve the quality stability of the laminated film formed by combining layers X and Y.

[0041] The laminated polyester film of the present invention has a contact angle of formamide on the surface of the layer Y of C i (°), 50°C, 90% RH, 24 hours of wet heat treatment, and then the contact angle of formamide on the surface of the layer Y measured. t (°), it is preferable that the following formula 4 is satisfied.

[0042] -5≦C t -C i ≦5...Equation 4 C t -C i By making the angle between -5° and 5°, it is possible to prevent layer Y from being affected by layer X and causing quality changes over time, and the quality stability of the laminated film formed by adding layer X and layer Y becomes good.

[0043] Among the reagents used to measure surface free energy, formamide has a balance between the dispersion component and the polar component of the surface free energy similar to that of water-soluble acrylic resin, so the influence of layer X can be sensitively detected by the value of the contact angle. Specifically, the greater the change in layer X due to the moist heat treatment, the greater the C t -C i tends to fluctuate significantly in either positive or negative directions. t -C iis -5° or more and 5° or less means that the fluctuation range is within 5° in either the positive or negative direction, and indicates that the change in the quality of layer X is small, that is, the quality stability of the laminated film formed by adding layer X and layer Y is good.

[0044] C t -C i is more preferably -2° or more and 2° or less. Methods for making layer Y satisfy formula 4 include reducing the proportion of highly hydrophilic skeletons in the material constituting layer X, or forming layer X by an in-line coating method in which a polyester film is stretched and film-formed at the same time. When forming layer Y on layer X, a coating material containing an organic solvent is applied, and it is believed that the organic solvent penetrates into layer X, thereby affecting the properties of layer Y. Therefore, by controlling the hydrophilicity of layer X or forming layer X by an in-line coating method, the penetration of the organic solvent into layer X is suppressed, making layer Y less susceptible to the influence of layer X, and it is believed that the quality stability of the laminated film formed by combining layer X and layer Y is improved.

[0045] The laminated polyester film of the present invention has a dimethylsiloxane transfer amount on the surface of the layer Y measured by FT-IR. i After 24 hours of moist heat treatment at 50°C and 90% RH, the amount of dimethylsiloxane transferred was measured. t In this case, it is preferable that the following formula 5 is satisfied. T t >T i ...Formula 5 By having layer Y satisfy formula 5, it is possible to prevent the release effect of the silicone resin layer of layer Y from changing over time due to the influence of layer X, and the quality stability of the laminated film formed by adding layers X and Y together becomes good.

[0046] Here, T t >T i"The amount of dimethylsiloxane transferred after the moist heat treatment is greater than the amount transferred before the treatment," which means that the amount of dimethylsiloxane present near the surface of Layer Y and available for transfer increases during the treatment process. Dimethylsiloxane is a low-molecular-weight silicone resin, and when contained in Layer Y, which is made of silicone resin, it plays an important role in imparting properties such as water repellency that are unique to silicone. Therefore, we believe that an increase in the amount of dimethylsiloxane present on the outermost surface of Layer Y enhances the properties of Layer Y as a silicone resin and contributes to increasing the quality stability of the laminated film formed by adding Layers X and Y together.

[0047] One way to satisfy formula 5 is to decrease the proportion of highly hydrophilic skeletons or increase the proportion of highly flexible skeletons in the material that makes up layer X. Dimethylsiloxane is a low-molecular-weight silicone resin, and it is thought that a certain amount is present in layer Y and reversibly diffuses into and out of layer Y. However, if the material that makes up layer X is highly hydrophilic or if layer X is rigid, it is thought that dimethylsiloxane that diffuses into layer X is more likely to be captured within layer X, and the amount of dimethylsiloxane that diffuses to the surface of layer Y is relatively reduced.

[0048] Taking advantage of the above-mentioned properties, the laminated polyester film of the present invention can be suitably used for release applications in which a release layer is provided on the surface of layer Y opposite the surface that contacts layer X, and the release layer is peeled off from layer Y. Furthermore, since layer X and layer Y can be removed from the laminated polyester film of the present invention using water, it is possible to remove the release material and then remove layer X and layer Y to extract a high-purity polyester film. Furthermore, it is preferable to remove layer X and layer Y from the laminated polyester film of the present invention, and then extract and reuse the high-purity polyester film. It is more preferable to remove layer X and layer Y and then extract and reuse only the polyester film. Examples of recycling methods include a method in which layer X and layer Y are again provided on the extracted polyester film and used as a release film, and a method in which the polyester film is remelted and remolded into a polyester film. The method of remelting and remolding into a polyester film is preferred because it is not limited to certain reuse applications and can be used for various applications, significantly contributing to reducing environmental impact.

[0049] When a silicone compound, particularly a compound containing a dimethylsiloxane bond, is used as Layer Y of the laminated polyester film of the present invention, the component containing the dimethylsiloxane bond is likely to become a foreign substance when mixed with the polyester film and remelted, which may accelerate deterioration of the polyester or make it impossible to extrude the film after melting. Therefore, it is preferable to remove Layer Y in order to remelt and reuse the film of the present invention.

[0050] When the laminated polyester film of the present invention having Layer X or Layer Y is used as a release film, the release layer can be an organic adhesive primarily composed of acrylic or an inorganic sheet primarily composed of a metal or metal oxide. Ceramic dielectrics, such as barium titanate, among metal oxides, are particularly essential for the production of multilayer ceramic capacitors (MLCCs), and the amount of process release films used in the production of ceramic dielectric sheets is increasing. Under these circumstances, using the laminated polyester film of the present invention having Layer X or Layer Y as a release film in the process of producing ceramic dielectric sheets can suppress in-plane quality variations in the ceramic dielectric sheets due to the unstable quality of the release film, improving yield when peeling the ceramic dielectric sheets from the release film and improving in-plane quality uniformity at the lamination interface when stacking the peeled sheets to produce MLCCs, thereby contributing to improved productivity.

[0051] Furthermore, after using the release film, the layer X and the layer Y can be removed from the laminated polyester film of the present invention to obtain a polyester film with high purity, which can be reused, thereby contributing to reducing the environmental load.

[0052] A preferred embodiment of the method for producing a laminated polyester film of the present invention will be described below using a specific example.

[0053] The laminated polyester film of the present invention is produced using an in-line coating method in which an aqueous coating material that is the basis for 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.

[0054] First, the raw material for the polyester film is placed in a single-screw or twin-screw extruder, heated and melted, and then extruded through a die (T-die) with a straight lip. The raw material is preferably dried to a moisture content of 50 mass 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, static electricity is preferably applied to adhere the sheet to the casting drum in order to obtain a uniform film.

[0055] Next, this unstretched sheet is heated to a temperature above Tg°C and below Tg + 40°C (Tg°C) using roll heating, or if necessary, infrared heating, and stretched in the longitudinal direction (hereinafter referred to as 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 because this effectively and uniformly applies stress to the film, making it easier to impart orientation to the film. The MD stretching ratio is preferably 2.5 times to 5.0 times. Setting the MD stretching ratio to 2.5 times or more, more preferably 3.0 times or more, can suppress stretching unevenness in the subsequent TD stretching. Setting the MD stretching ratio to 5.0 times or less, more preferably 4.5 times or less, can prevent the film from breaking during film formation.

[0056] Next, the aqueous coating material that will be the basis of layer X is adjusted to the desired solid content concentration and then applied to the obtained uniaxially stretched film by bar coating.

[0057] Next, the film is stretched in a direction perpendicular to the MD (hereinafter referred to as TD stretching). A preferred TD stretching method is a tenter method, in which the film is held at both widthwise ends with clips and stretched while being transported through a heat treatment device. The preheating and stretching temperatures for TD stretching are preferably Tg+10°C or higher and Tg+50°C or lower, where Tg (°C) is the glass transition temperature of the unstretched sheet. The TD stretching ratio is preferably 3.0 times or higher and 5.5 times or lower. A ratio of 3.0 times or higher, more preferably 3.6 times or higher, can further enhance the molecular chain order of the acrylic resin applied to the surface. Furthermore, a ratio of 5.5 times or lower, more preferably 5.0 times or lower, can prevent the film from breaking during film formation. The stretching speed for TD stretching is preferably 5% / sec or higher and 150% / sec or lower, more preferably 20% / sec or higher and 100% / sec or lower, to enhance the molecular chain order of the acrylic resin.

[0058] Although the detailed description has been given here of the case where stretching is performed by a sequential biaxial stretching method in which stretching in the MD direction and stretching in the TD direction are performed separately, a simultaneous biaxial stretching method in which stretching in the MD direction and stretching in the TD direction are performed simultaneously may also be used as long as the effects of the present invention are not impaired.

[0059] 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 or layer X and increase the uniformity of order, it is also preferable to carry out a relaxation treatment at a relaxation rate of 1.0% to 5.0% in the TD direction for 0.2 to 10 seconds during the heat treatment.

[0060] Thereafter, the film is gradually cooled uniformly, cooled to room temperature, and wound up on a roll to obtain a laminated polyester film having layer X provided on the surface of the polyester film.

[0061] The thickness of layer X is preferably 10 nm or more and 500 nm or less. By making it 10 nm or more, layer X can fully exhibit its function as a water-soluble resin, and the removability when removing layer X and layer Y can be improved. In addition, by making it 500 nm or less, it is possible to prevent cleavage from occurring inside layer X due to blocking or the like, which can reduce handleability, and this is preferable. From the same viewpoint, a thickness of 50 nm or more and 300 nm or less is more preferable.

[0062] Next, a method for providing layer Y will be described. Layer Y may be provided simultaneously with layer X, or separately. When providing them simultaneously, examples include a method of separately coating the two layers using a die or the like, or a method of coating using a coating material in which the components of layer X and layer Y are premixed. To improve the lamination accuracy of layer X and layer Y, it is preferable to provide layer X and layer Y separately. A coating solution containing the components of layer Y dissolved in the layer X-containing laminated polyester film obtained by the above-described method can be applied using a common coating method such as gravure coating, Mayer bar coating, air knife coating, or doctor knife coating. The thickness of layer Y is preferably 10 nm or more and 1000 nm or less. By setting the thickness to 10 nm or more, layer Y is less susceptible to the influence of layer X, allowing the function of layer Y to be more fully exhibited. Setting the thickness to 1000 nm or less is preferable because it facilitates the effect of the present invention of controlling the surface properties of layer Y by the properties of layer X. From the same viewpoint, a thickness of 30 nm or more and 500 nm or less is more preferable, and a thickness of 50 nm or more and 500 nm or less is even more preferable.

[0063] Next, a method for removing Layer X and Layer Y will be described. By configuring Layer X as described above and washing with an aqueous cleaning solution, it is possible to extract only the polyester film from which Layer X and Layer Y 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.

[0064] Next, a specific method for removing Layer X and Layer Y will be described using, as an example, a process release film provided with Layer Y made of a silicone resin. For example, an aqueous cleaning solution containing water as a main component may be applied to the surface of Layer Y side of a used release film containing the laminated polyester film of the present invention, and then a removal member for removing Layers X and Y may be brought into contact with the surface, and the film may be moved in its longitudinal direction relative to the removal member, thereby physically removing the layers. The temperature of the applied aqueous cleaning solution is preferably at least Tg°C but not more than Tg + 100°C, where Tg (°C) is the glass transition temperature of the polyester film in the laminated film in an unstretched state, in order to enhance removability, and more preferably at least Tg + 10°C but not more than Tg + 80°C.

[0065] 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 cleaning liquid applied is preferably adjusted appropriately depending on the properties and thickness of the layer X and layer Y 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. 2It has been confirmed that the removal ability is enhanced by using 3 ml or more per unit area. Any solvent that can dissolve layer X can be used as the cleaning solution, but to reduce the environmental impact, it is preferable to use water. The cleaning ability can also be enhanced by adding a surfactant to water as the main component or adjusting the pH to alkaline.

[0066] Examples of the removal member include, but are not limited to, a scraper, fabric, metal plate, rotating brush roll, and absorbent roll wrapped with absorbent nonwoven fabric. Any form may be used as long as it can directly contact the film and physically remove the target layers X and Y. The removal member is preferably pressed directly into contact with the functional layer-bearing surface of the film. Removal efficiency can be 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 within a 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 can locally press more strongly against the film surface.

[0067] As described above, the laminated polyester film of the present invention can be used as a release film or the like by providing layer Y on layer X on at least one side of the polyester film, and then washing and removing layer X and layer Y to easily separate the polyester film alone. The separated film can be reused as is, or remelted and chipped, and reused as recycled polyester raw material. In particular, the laminated polyester film can be suitably used in applications in which a release layer Y made of a silicone resin is provided on layer X of the laminated polyester film, an object to be released is further provided on the release layer, the object to be released is first peeled off, and then layer Y and layer X are removed.

[0068] Next, a preferred embodiment of a method for using a film from which layers X and Y have been removed as a 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, introduced into an extruder, melted, extruded into strands, and cut into pellets to obtain the 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, a twin-screw extruder is 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 a raw material for producing the polyester film described above.

[0069] A preferred embodiment of the laminated polyester film of the present invention is, as described above, to provide layer X on at least one side of a polyester film, and then provide layer Y to use the film as a release film for processing, particularly for MLCC production, and then remove layer X and layer Y by washing to obtain a high-purity polyester film. The resulting polyester film 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.

[0070] [Characteristics evaluation method] A. Identification of the main skeleton of layer X The components of layer X are dissolved in a solvent and then concentrated to dryness. 1 The main skeleton of layer X is identified by analyzing using 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.

[0071] B. Identification of resin type in layer Y When the components of layer Y were analyzed by attenuated total reflectance Fourier transform infrared spectroscopy (FT-IR-ATR), -1 , 1010cm -1 , 785cm -1 The absorption intensity of each of these three peaks is 2920 cm -1 If the absorption intensity of the absorption peak is 5 times or more higher than that of the absorption peak of the layer Y, the layer Y is determined to be made of silicone resin.

[0072] C. Orientation parameter R xy The resin layer X side of the laminated polyester film is measured using Fourier transform infrared spectroscopy (FT-IR-ATR) with total reflection. The sample is pre-conditioned in an atmosphere at room temperature of 23°C and a relative humidity of 65%. Measurements are performed using a tool that allows the measurement direction to be changed while the ATR crystal and the sample are pressed together. Starting from an arbitrarily selected direction (0°), measurements are performed in 12 directions up to 165° in 15° increments. The obtained spectrum is divided by the spectrum of a similarly measured polyester film "Lumirror" (registered trademark) #50T60 manufactured by Toray Industries, Inc. to obtain a difference spectrum. Next, in the difference spectrum, the absorption at 1446 cm, which corresponds to the CH bending vibration of the CH2 group in the acrylic main chain, is measured. -1 The absorption intensity (Abs., peak height) of the absorption peak is calculated for each of the 12 directions. The absorption intensity is calculated as a relative intensity to the reference peak, specifically, 1506 cm -1 The peak of the ring vibration of the aromatic ring at 1446 cm is used as the reference peak, and the absorption intensity of the reference peak is normalized to 1. -1 Calculate the relative intensity of the absorption peak.

[0073] Next, among the 12 directions, the absorption intensity (relative intensity to the reference peak) is maximized at 1446 cm -1 The absorption intensity of the absorption peak of x , 1446 cm in the direction perpendicular to the maximum direction -1 The absorption intensity of the absorption peak is defined as Ay, and the orientation parameter R is calculated by the following formula. xy Ask for. R xy =(Ax -A y ) / (A x +A y ) The apparatus and conditions used for the measurement are as follows: Equipment: 670-IR (Varian FT-IR) Light source: Globar Detector: MCT (Hg-Cd-Te) Resolution: 4cm -1 Number of times accumulated: 256 Measurement method: Attenuated total reflection method Attachment: Single reflection ATR measurement attachment (The Seagull TM ) ATR crystal: Germanium Incident angle: Measured in 15° increments from 0 to 165° Polarization: S (vertical polarization).

[0074] D. Hydrophilicity parameter W x After measuring the surface of the laminated polyester film on the resin layer X side by Fourier transform infrared spectroscopy (FT-IR-ATR) attenuated total reflection, the spectrum of a 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 peak at 3000 cm -1 ~3600cm -1 The area of ​​the peak derived from the hydrophilic group was calculated as A ph Height: 1446cm -1 Calculate the area of ​​the CH bending vibration peak of the CH2 group pb Then, the hydrophilicity parameter W is calculated using the following formula: x When performing FT-IR-ATR measurements, the operator wears new nitrile gloves for each measurement, and the ATR crystal is cleaned with acetone before each measurement. W x = A ph / A pb The apparatus and conditions used for the measurement are as follows: Equipment: 670-IR (Varian FT-IR) Light source: Globar Detector: MCT (Hg-Cd-Te) Resolution: 4cm -1 Number of times accumulated: 256 Measurement method: Attenuated total reflection method Attachment: Single reflection ATR measurement attachment (The Seagull TM ) ATR crystal: Germanium Incident angle: 60° Polarization: None

[0075] E. 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 in the stepwise changing portion of the glass transition by the method described in "9.3 How to determine the glass transition temperature (1) Midpoint glass transition temperature Tmg" of JIS K-7121 (1987).

[0076] F. Formation of Layer Y Coating material I was gravure coated on the surface of layer X of the obtained laminated polyester film opposite the surface in contact with the polyester film so that the thickness after drying was 90 nm, and then dried to obtain a laminated polyester film provided with layer Y having a thickness of 90 nm. The laminated polyester film provided with layer X and layer Y was heat-treated in a hot air oven at 40°C for 20 hours and then used for evaluation.

[0077] G. Formamide contact angle The contact angle of the surface of layer Y of the laminated polyester film sample is measured using a contact angle meter DM500 manufactured by Kyowa Interface Science Co., Ltd. and the accompanying analysis software FAMAS according to the following method. The laminated polyester film is conditioned in an atmosphere at room temperature of 23°C and humidity of 65% RH. Then, in the same atmosphere, formamide is dropped onto the surface of layer Y of the laminated polyester film, and the contact angle is measured over 10 seconds, with the time when the droplet contacts the sample surface being set as 0 seconds. Measurements are made 10 times at different locations, and the average of the 10 contact angle measurements after 10 seconds is calculated and used as the contact angle of formamide.

[0078] H. Dimethylsiloxane transcription amount In total reflectance Fourier transform infrared spectroscopy (FT-IR-ATR), an ATR crystal is pressed against the surface of layer Y of the laminated polyester film sample, and after 10 minutes the pressure is released. A spectrum is then collected in this state, and spectral information on the components transferred from layer Y to the surface of the ATR crystal is obtained. Next, from the obtained spectrum, the peak at 1263 cm -1 CH bending vibration peak, 1099 cm -1 Si-O-Si stretching vibration peak, 1022 cm -1 The absorption intensities (Abs., peak heights) of the three absorption peaks of the Si-O-Si stretching vibration peaks are calculated, and their average value is defined as the amount of dimethylsiloxane transferred. Note that all three absorption peaks are derived from the dimethylsiloxane skeleton, and are detected with roughly the same intensity. The larger the average value, the greater the amount of dimethylsiloxane component transferred from layer Y to the surface of the ATR crystal. The apparatus and conditions used for the measurement are as follows: Equipment: 670-IR (Varian FT-IR) Light source: Globar Detector: DLaTGS (deuterated L-alanine doped triglycine sulfate) Resolution: 4cm -1 Number of times accumulated: 256 Measurement method: Attenuated total reflection method Attachment: Single reflection ATR measurement attachment (The Seagull TM) ATR crystal: Germanium Incident angle: 60° Polarization: None

[0079] I. Moist heat treatment The sample is placed in a thermo-hygrostat (manufactured by Espec Corp.) adjusted to 50°C and 90% RH, and subjected to 24-hour moist heat treatment. The formamide contact angle (item G) above, the amount of dimethylsiloxane transferred (item H) above, and the quality stability (item K) described below are similarly evaluated for the moist heat treated sample, and the evaluation results are compared with those of the untreated sample.

[0080] J. Weight average molecular weight Measurement is carried out using a GPC "GPC-8020" manufactured by Tosoh Corporation under the following conditions. Column: Guard column PWXL (1 column) and GMPWXL (2 columns) manufactured by Tosoh Corporation (temperature: 40°C) Eluent: 0.5 mol / l acetate buffer (pH = 4.7) Measurement temperature: 40℃ Detector: differential refractometer Calibration standards: polyethylene oxide.

[0081] K. Quality stability A laminated polyester film having layers X and Y is coated with coating material J (described below) as a release material using a die coating method so that the thickness after drying is 1.0 μm. 15 seconds after coating, the film is dried for 2 minutes in an oven at a temperature of 100°C and an air speed of 5 m / s. The resulting laminated polyester film with the release material (ceramic sheet) laminated thereon is cut into a 40 mm wide x 80 mm long specimen. Using a peel tester VPA-H200 manufactured by Kyowa Interface Science Co., Ltd., the release material is peeled from layer Y at a peel angle of 90° and a peel speed of 300 mm / min, and the peel strength is measured. The peel strength is converted to a 50 mm width to obtain the untreated peel strength P. i Let's say.

[0082] Next, before applying a release material to the laminated polyester film having Layer X and Layer Y, the wet heat treatment (50°C, 90% RH, 24 hours) of the above item I was carried out, and then the release material was applied in the same manner as above to prepare a test piece, and the peel strength was measured in the same manner. t The rate of change in peel strength (%) is calculated using the formula below, and the quality stability is judged according to the following criteria. Peel strength change rate (%) = {(P t -P i ) / P i}×100 A: Peel strength change rate is less than 5% B: Peel strength change rate is 5% or more and less than 20% C: Peel strength change rate is 20% or more but less than 50% D: Peel strength change rate is 50% or more.

[0083] L. MLCC quality 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 (4). (1) An electrode forming sheet on which an internal electrode for forming a capacitance is formed is formed by screen printing Ni paste on the laminated polyester film with the ceramic sheet prepared in the above item K. (2) A predetermined number of electrode-forming sheets are stacked, and then ceramic sheets (external layer sheets) without electrodes are stacked on both the top and bottom sides of the stack, and these are then pressed together to form a laminate in which one end of each internal electrode is drawn out to the end face on alternate sides. Here, when stacking the electrode-forming sheets and external layer sheets, these sheets are peeled off from the laminated polyester film as they are stacked. (3) 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. (4) A conductive paste containing Ag as a conductive component is applied to both ends of the formed ceramic element and baked to form external electrodes that are electrically connected to the internal electrodes.

[0084] A total of 100 multilayer ceramic capacitors (MLCCs) were prepared, and a current test was conducted to calculate the short circuit occurrence rate, and the quality of the MLCCs was evaluated according to the following criteria. Note that short circuits in MLCCs are thought to occur when the sintering of the ceramics does not proceed uniformly. A: Short circuit occurrence rate is less than 5% B: Short circuit occurrence rate is 5% or more but less than 10% C: The short circuit rate is 10% or more.

[0085] M. Reusability The laminated polyester film having Layer X and Layer Y after peeling off the ceramic sheet in the above item L was cut into a 5 cm square, immersed in 80°C water for 10 seconds, and then scraped in one direction five times on the surfaces of Layer X and Layer Y with a scraper (a plastic multi-spatula manufactured by Inoue Tools) while applying a load of 1 kg while still in the water, and then wiped off the water to obtain a polyester film from which Layer X and Layer Y had been removed.

[0086] The polyester film obtained by the above method from which Layer X and Layer Y have been removed is prepared in a total weight of 27 g, dried at 140°C for 30 minutes, and then pulverized into pieces of 5 mm square or less. 27 g of the resulting material is placed in a batch-type small melt-kneading machine, Labo Plastomill (manufactured by Toyo Seiki Seisakusho, 4C150), and melt-kneaded under the following conditions to obtain torque data. The torque value after 5 minutes is designated as T s (N·m). Screw: Roller mixer R30 Set temperature: 280℃ Nitrogen flow rate: 10mL / min Screw rotation speed: 150 rpm Mixing time: 5 minutes The standard polyester film obtained in Reference Example 1 below is dried in the same manner as above, and then melt-kneaded. The torque value after 5 minutes is defined as T0 (N·m). Reusability is evaluated according to the following criteria. A:T s / T0 is less than 1.05 B:T s / T0 is 1.05 or higher. [Example]

[0087] The present invention will be described below with reference to examples, but the present invention is not necessarily limited to these examples.

[0088] [Polymerization of PET (Polyester A)] Polymerization of terephthalic acid and ethylene glycol was carried out in the usual 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.

[0089] [Monomer 1] Acrylamide (Wako First Grade, molecular weight 71.08) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used.

[0090] [Monomer 2] 2-acrylamido-2-methylpropanesulfonic acid (Wako special grade, molecular weight 207.25) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used.

[0091] [Monomer 3] 4-acryloylmorpholine (Wako First Grade, molecular weight 141.17) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used.

[0092] [Monomer 4] 2-Methoxyethyl acrylate (Wako First Grade, molecular weight 130.14) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used.

[0093] [Coating material A] A four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube was charged with 15 parts by weight of monomer 1, 41 parts by weight of monomer 3, 44 parts by weight of monomer 4, and 270 parts by weight of ion-exchanged water, and oxygen was removed from the reaction system 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 bisulfite were added as polymerization initiators under stirring. The temperature was raised to 85°C, and the viscosity of the reaction solution (25°C, solids concentration 20% by weight equivalent) reached 130 mPa·s. The polymerization was terminated when the solution was cooled and further diluted with ion-exchanged water to obtain a polymer aqueous solution with a pH of 5.5, a solids content of 20.0% by weight, and a viscosity of 130 mPa·s. The resulting polymer aqueous solution was diluted with ion-exchanged water to a solids concentration of 2.6% by weight to obtain coating material A. The weight-average molecular weight (Mw) of the resin contained in the coating material was 200,000, and the glass transition temperature was 90°C.

[0094] [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 into the flask were changed to 34 parts by mass of Monomer 1, 41 parts by mass of Monomer 3, 25 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 140°C.

[0095] [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 into the flask were changed to 6 parts by mass of monomer 1, 22 parts by mass of monomer 3, 72 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 70°C.

[0096] [Coating material D] Coating material D 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 12 parts by mass of monomer 1, 35 parts by mass of monomer 3, 53 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.

[0097] [Coating material E] Coating E, with a solids concentration of 2.6% by mass, was obtained in the same manner as Coating A, except that polymerization was terminated when the viscosity of the reaction solution (25°C, solids concentration 20% by mass) reached 30 mPa·s. The weight-average molecular weight Mw of the resin contained in the coating was 30,000, and the glass transition temperature was 90°C.

[0098] [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 5 parts by mass of monomer 1, 22 parts by mass of monomer 2, 35 parts by mass of monomer 3, 37 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 85°C.

[0099] [Coating material G] Coating material G, 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 61 parts by mass of Monomer 1, 24 parts by mass of Monomer 3, 15 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 H] Coating material G, 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 61 parts by mass of Monomer 1, 24 parts by mass of Monomer 3, 15 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.

[0101] [Coating material I] Coating material I was prepared by dissolving 100 parts by mass of a silicone release agent manufactured by Shin-Etsu Chemical Co., Ltd. (product name "KS-847T") and 3 parts by mass of a platinum catalyst manufactured by Shin-Etsu Chemical Co., Ltd. (product name "CAT-PL-50T") 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 mass.

[0102] [Coating material J] Glass beads with a number average particle size of 2 mm were added to 100 parts by mass of barium titanate (manufactured by Fuji Titanium Kogyo Co., Ltd., product name HPBT-1), 10 parts by mass of polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., product name BL-1), 5 parts by mass of dibutyl phthalate, and 60 parts by mass of toluene-ethanol (mass ratio 30:30), and the mixture was mixed and dispersed in a jet mill for 24 hours. The mixture was then filtered to produce a dielectric paste, which resulted in coating material J.

[0103] Example 1 Polyester A was dried under high vacuum 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. The sheet was then preheated with a group of heated rolls, stretched 3.6 times in the longitudinal direction (MD) at a temperature of 90°C, and cooled with a group of rolls at a temperature of 25°C to obtain a uniaxially stretched film.

[0104] Coating material A was applied to the obtained uniaxially stretched film. At that time, the coating thickness was adjusted so that the film thickness after passing through the heat treatment zone described below would be 90 nm. Next, both ends of the coated uniaxially stretched film in the width direction were held with clips and introduced into the preheating zone. The ambient temperature in the preheating zone was 90°C to 100°C, and then the film was continuously stretched 3.4 times in the width direction (TD direction) perpendicular to the longitudinal direction at a stretching rate of 60% / sec in the 105°C stretching zone, and then heat-treated for 10 seconds in the 230°C heat treatment zone to obtain a laminated polyester film having a resin layer X. The thickness of the obtained laminated polyester film was 31 μm. The properties of the obtained laminated polyester film are shown in the table.

[0105] 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 the table.

[0106] 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 B and the stretching ratio in the TD direction was changed to 3.9 times. The properties of the obtained laminated polyester film are shown in the table.

[0107] 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. The properties of the obtained laminated polyester film are shown in the table.

[0108] Example 5 Except for changing the stretching ratio in the TD direction to 3.9 times, a laminated polyester film was obtained in the same manner as in Example 1. The properties of the obtained laminated polyester film are shown in the table.

[0109] 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 and the stretching ratio in the TD direction was changed to 3.9 times. The properties of the obtained laminated polyester film are shown in the table.

[0110] Example 7 A laminated polyester film was obtained in the same manner as in Example 1, except that the stretching ratio in the TD direction was changed to 3.9 times and the stretching speed in the TD direction was changed to 15% / sec. The properties of the obtained laminated polyester film are shown in the table.

[0111] 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 E. The properties of the obtained laminated polyester film are shown in the table.

[0112] Example 9 A laminated polyester film was obtained in the same manner as in Example 1, except that the thickness of the layer Y formed during evaluation was changed to 20 nm. The properties of the obtained laminated polyester film are shown in the table.

[0113] Example 10 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 and the stretching ratio in the TD direction was changed to 3.9 times. The properties of the obtained laminated polyester film are shown in the table.

[0114] (Comparative Example 1) A laminated polyester film was obtained in the same manner as in Example 1, except that the stretching ratio in the TD direction was changed to 2.5 times. The properties of the obtained laminated polyester film are shown in Table 1. The film had poor quality stability.

[0115] (Comparative 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 G. The properties of the obtained laminated polyester film are shown in Table 1. The film had poor quality stability.

[0116] (Comparative Example 3) An attempt was made to produce a laminated polyester film in the same manner as in Example 1, except that the coating material was changed to coating material H. However, Layer X was unable to follow the stretching in the TD direction, and coating cracks occurred during stretching, making it impossible to form Layer X.

[0117] (Reference example 1) A polyester film (standard polyester film) having a thickness of 31 μm was obtained in the same manner as in Example 1, except that no coating material was applied to the uniaxially stretched film.

[0118] [Table 1]

[0119] [Table 2] [Industrial Applicability]

[0120] The laminated polyester film of the present invention has excellent quality stability. By providing the laminated polyester film of the present invention with a layer Y made of a silicone resin, it can be suitably used as a release film in the manufacturing process of a multilayer ceramic capacitor (MLCC) using a dielectric paste as the release material. Furthermore, since the polyester film can be easily recovered from the release film after use in the MLCC manufacturing process, the polyester film can be easily reused as a raw material for melt film formation.

Claims

1. A laminated polyester film having a water-soluble resin layer X on at least one surface of a polyester film, the resin layer X having an acrylic as a main skeleton and a repeating unit represented by chemical formula (1) or chemical formula (2), and the laminated polyester film satisfies the following (1) and (2): (1) The formula R ｘｙ = (A ｘ -A ｙ ) / (A ｘ +A ｙ ) the orientation parameter R of the layer X ｘｙ is equal to or greater than 0.02 and less than 1.

00. A ｘ : Absorption intensity in the direction where CH bending vibration is maximum A ｙ : Absorption intensity in the direction of maximum CH bending vibration + 90° The absorption intensity was determined by subtracting the contribution of the polyester film spectrum from the CH of the acrylic main chain. ２ 1446 cm corresponding to the absorption of CH bending vibration of the group －１ The absorption intensity (Abs., peak height) of the absorption peak at 1506 cm －１ The peak of the ring vibration of the aromatic ring at 1446 cm was used as the reference peak, and the absorption intensity of the reference peak was normalized to 1. －１ Calculate the relative intensity of the absorption peak. The direction in which the CH bending vibration is maximum is the direction in which the absorption intensity (relative intensity to the reference peak) is maximum among 12 directions from an arbitrarily selected direction in the film plane as the starting point (0°) to 165° in 15° increments. (2) The formula W measured by attenuated total reflectance Fourier transform infrared spectroscopy (FT-IR-ATR) ｘ = A ｐｈ / A ｐｂ The hydrophilicity parameter W of layer X is expressed as ｘ is 2 or more and 10 or less. A ｐｈ : 3000 cm －１ ~3600cm －１ Area of ​​the peak derived from hydrophilic groups A ｐｂ : 1446 cm －１ CH ２ Area of ​​CH bending vibration peak of group 【Chemical 1】 R １ is a hydrogen atom or a methyl group, R ２ represents any functional group. 【Chemistry 2】 R ３ is a hydrogen atom or a methyl group, R ４ and R ５ represents any functional group.

2. The layer X further has a silicone resin layer Y on the surface opposite to the surface in contact with the polyester film, and the contact angle C of formamide on the surface of the layer Y is ｉ 2. The laminated polyester film according to claim 1, wherein (°) satisfies the following formula: 90≦C ｉ ≦110

3. 3. The laminated polyester film according to claim 2, wherein the surface of the layer Y satisfies the following conditions: -5≦C ｔ -C ｉ ≦5 C ｉ : Contact angle of formamide on the surface of layer Y (°) C ｔ : Contact angle (°) of formamide on the surface of Layer Y after wet heat treatment (50°C, 90% RH, 24 hours)

4. 4. The laminated polyester film according to claim 3, wherein the amount of dimethylsiloxane transferred to the layer Y, which is determined by the following measurement method, satisfies the following relationship: T ｔ >T ｉ T ｉ : Amount of dimethylsiloxane transferred from untreated film T ｔ : Amount of dimethylsiloxane transferred after moist heat treatment (50°C, 90% RH, 24 hours) (Measurement method) In total reflection Fourier transform infrared spectroscopy (FT-IR-ATR), an ATR crystal is pressed onto the surface of layer Y of a laminated polyester film sample, and after 10 minutes the pressure is released. A spectrum is then collected in this state, thereby obtaining spectral information on the components transferred from layer Y to the surface of the ATR crystal. Next, from the obtained spectrum, the peak at 1263 cm －１ CH bending vibration peak, 1099 cm －１ Si—O—Si stretching vibration peak, 1022 cm －１ The absorption intensities (Abs., peak heights) of the three absorption peaks of the Si—O—Si stretching vibration peaks are calculated, and the average value thereof is taken as the amount of dimethylsiloxane transferred.

5. 3. The laminated polyester film according to claim 2, 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 release purposes by peeling the release layer from layer Y.

6. 6. The laminated polyester film according to claim 5, which is used in an application in which, after the release layer is peeled from the layer Y, the layer X and the layer Y are further removed.

7. 7. The laminated polyester film according to claim 6, which is used for recycling the laminated polyester film from which the layer X and the layer Y have been removed.

8. 6. The laminated polyester film according to claim 5, wherein the release layer is a ceramic sheet containing barium titanate as a main component.

9. 2. A multilayer ceramic chip capacitor obtained by laminating the ceramic sheets released from the laminated polyester film according to claim 1, further comprising a silicone resin layer Y on the surface of the layer X opposite to the surface that contacts 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 that contacts the layer X.

10. A method for producing a polyester film, comprising the steps of: using the laminated polyester film according to claim 1, 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 layers Y and X from the film from which the release layer has been peeled; producing recycled raw materials from the film from which the release layer, layer Y, and layer X have been removed; and producing a film using the recycled raw materials.

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