Multilayer film, resin composition, and method for manufacturing same

Abstract

Provided is a multilayer film that can be recycled whatever the type of functional layer may be, that has favorable durability and long-term storability, and that can significantly reduce degradation in post-recycling quality compared to pre-recycling quality.　The multilayer film comprises a base film in which at least a separation layer A composed of a first composition including amino resin and a support layer B composed of a second composition including aromatic polyester resin are laminated, and a functional layer C composed of a third composition for producing a function on a surface of the base film. The separation layer A is provided between the functional layer C and the support layer B. The separation layer A and the support layer B constitute the base film. For the functional layer C, a release layer, a hard coat layer, an adhesive layer, a decorative layer, a light shielding layer, or an ultraviolet shielding layer, for example, may be used.

Description

Laminated film, resin composition, and method for producing same

[0001] The present invention relates to a laminated film having a support layer containing an aromatic polyester resin, a resin composition obtained by material recycling of this laminated film, and a method for producing this resin composition.

[0002] Polyester films made of aromatic polyester resins such as polyethylene terephthalate (hereinafter sometimes referred to as "PET") resin have excellent properties such as mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, and optical properties. Therefore, they are often used as functional films in which various functional layers are laminated on one or both sides of the polyester film. Examples of functional layers include a release layer, a hard coat layer, a pressure-sensitive adhesive layer, a decorative layer, a light-shielding layer, and an ultraviolet-shielding layer. Materials appropriate for the functional layer are laminated onto the polyester film.

[0003] From the perspective of resource circulation, recycling of these functional films is desired. However, if they are remelted as is, the materials that make up the functional layer will be mixed into the molten polyester, causing discoloration of the polyester film and deterioration of quality due to foreign matter contamination. As a result, many used functional polyester films must be discarded or incinerated, which is a major problem from the perspective of resource circulation these days.

[0004] Therefore, Patent Document 1 proposes a technique for decomposing and removing a functional layer by cleaning a laminated film having the functional layer with a cleaning agent. In this technique, an alkalizing agent and a cleaning agent having at least one hydroxyl group are used to decompose and remove the functional layer.

[0005] Furthermore, Patent Document 2 proposes a recycling method in which, after use, a laminate film formed by laminating a readily soluble resin layer and a surface functional layer in this order on a substrate film is washed with a solvent capable of dissolving the resin constituting the readily soluble resin layer, thereby separating and recovering the substrate film or its pulverized product from the laminate film. In addition to water-soluble resins, polyesters such as polylactic acid are also exemplified as water-dispersible resins for the readily soluble resin layer.

[0006] Patent Document 1: WO2021 / 199895 Patent Document 2: JP 2004-169005 A

[0007] However, although Patent Document 1 makes it possible to obtain a polyester film that can be recycled from the functional layer, the polyester film is easily decomposed by cleaning agents, and therefore the quality after recovery is significantly inferior to the quality before recovery.

[0008] In Patent Document 2, when a water-soluble resin is used as the easily soluble resin layer, it is easily affected by the use environment, and problems such as deformation and peeling of the surface functional layer may occur in durability and long-term storage. Furthermore, when a water-dispersible polyester is used as the easily soluble resin layer, even when hot water of less than 100°C is used, it is difficult to disperse in hot water, and separation and recovery of the substrate film tends to be difficult. Furthermore, since the easily soluble resin layer has poor solvent resistance to the surface functional layer coating solution, there are limitations on the solvents that can be used when providing the surface functional layer, and when a laminate film is formed after providing the surface functional layer, problems such as impairing the properties of the functional layer and poor appearance tend to occur.

[0009] The present invention aims to provide a laminate film that can be recycled regardless of type without impairing the properties of the functional layer or the appearance of the resulting laminate film, that has good durability and long-term storage properties, and that can significantly prevent deterioration in quality after recycling compared to before recycling. Another object of the present invention is to provide a resin composition obtained by material recycling of this laminate film, and a method for producing this resin composition.

[0010] As a result of extensive research by the present inventors into sustainable polyester films with excellent recyclability, the present inventors have found that by providing a separation layer A that undergoes decomposition under specific conditions between an aromatic polyester film (support layer B) and a functional layer C, it is possible to recycle the aromatic polyester film regardless of the type of functional layer C while maintaining durability and long-term storage properties, thereby achieving both solvent resistance and recyclability.The present inventors have also found that it is possible to significantly prevent the quality of the recycled film from deteriorating compared to the quality before recycling.

[0011] Specifically, the present inventors discovered that the inclusion of an amino resin in the separation layer A can improve the durability, such as moisture resistance, and solvent resistance, of the separation layer. Furthermore, when the laminate film is treated under specific conditions, for example, with hot water or steam at 100°C or higher, the amino resin decomposes, facilitating removal of the functional layer and allowing the base polyester film to be recycled. In addition, the inventors have invented a method for producing a resin composition in which the functional layer C is removed from the laminate film, the support layer B is extracted, and the resulting material is recycled to obtain a resin composition containing an aromatic polyester resin. Therefore, the laminate film of the present invention has a sustainable configuration that is highly recyclable while maintaining durability and long-term storage stability.

[0012] Specifically, the laminate film of the present invention has the following configuration. [Item 1] A laminate film having a base film including a separation layer A composed of a first composition containing an amino resin and a support layer B composed of a second composition containing an aromatic polyester resin, and a functional layer C composed of a third composition that imparts a function to the surface of the base film, wherein the separation layer A is provided between the functional layer C and the support layer B. [Item 2] The laminate film of Item 1, wherein the amino resin is a melamine-based compound or a urea resin. [Item 3] The laminate film of Item 1 or 2, wherein the amino resin is a melamine-based compound and the amino resin is contained in an amount of 5% or more by mass of the entire separation layer A. [Item 4] The laminate film of any one of Items 1 to 3, wherein the first composition is a water-soluble resin or a water-dispersible resin. [Item 5] The laminate film of any one of Items 1 to 4, wherein the first composition comprises at least one resin selected from the group consisting of polyester-based resins, polyurethane-based resins, polyamide-based resins, polyacrylic resins, and polyvinyl alcohol-based resins. [Item 6] The laminate film according to any one of Items 1 to 5, wherein the first composition contains an aliphatic polyester. [Item 7] The laminate film according to Item 6, wherein the aliphatic polyester is polylactic acid, the aromatic polyester resin is polyethylene terephthalate resin, and the third composition contains a resin that is incompatible with polyethylene terephthalate resin. [Item 8] The laminate film according to any one of Items 1 to 7, wherein heights I1 to I4 of absorbance peaks in an infrared absorption spectrum satisfy the following formula: (I3 / I4) / (I1 / I2)≦0.2 (wherein I1 is the absorbance at 1560 cm on the surface of the laminate film). －１ I indicates the height of the absorbance peak near 1715 cm on the surface of the laminated film. －１ I3 indicates the height of the absorbance peak near 1560 cm on the film surface after treating the laminated film with hot water at 150 °C for 10 minutes. －１ I4 indicates the height of the absorbance peak near 1715 cm on the film surface after treating the laminated film with hot water at 150 °C for 10 minutes. －１[Item 9] The laminate film according to any one of items 1 to 8, wherein the heights I1, I2, I5, and I6 of the absorbance peaks in the infrared absorption spectrum satisfy the following formula: (I5 / I6) / (I1 / I2)≧0.2 (where I1 is the height of the absorbance peak at 1560 cm on the surface of the laminate film). －１ I indicates the height of the absorbance peak near 1715 cm on the surface of the laminated film. －１ I5 indicates the height of the absorbance peak near 1560 cm on the film surface after treating the laminated film with hot water at 90 °C for 2 hours. －１ I6 indicates the height of the absorbance peak near 1715 cm on the film surface after treating the laminated film with hot water at 90 ° C. for 2 hours. －１ (Item 10) The laminate film according to any one of Items 1 to 9, wherein the ratio of the thickness of the separation layer A to the thickness of the laminate film is 10% or less. [Item 11] The laminate film according to any one of Items 1 to 10, wherein the thickness of the separation layer A is 0.01 μm or more. [Item 12] The laminate film according to any one of Items 1 to 11, wherein the third composition contains a silicone release component. [Item 13] The laminate film according to any one of Items 1 to 12, wherein the maximum protrusion height (P) on the surface of the functional layer C is 200 nm or less, and the arithmetic mean roughness (Sa) on the surface of the functional layer C is 5 nm or less. [Item 14] The laminate film according to any one of Items 1 to 13, wherein the laminate film is a release film for producing a ceramic green sheet. [Item 15] A method for treating a laminate film, comprising a step of contacting the laminate film according to any one of Items 1 to 14 with moisture at a temperature of 100° C. or higher. [Item 16] A method for recovering an aromatic polyester resin from a laminate film, comprising a step of recovering the support layer B from the laminate film treated by the method of item 15. [Item 17] A material recycled polyester resin containing the aromatic polyester resin recovered by the method of item 16.

[0013] The present invention provides a laminate film having a functional layer that can be recycled regardless of type without impairing the properties of a wide variety of functional layers, has good durability and long-term storage properties, and can significantly prevent deterioration of quality after recycling compared to the quality before recycling.Furthermore, the present invention provides a resin composition obtained by material recycling this laminate film, and a method for producing this resin composition.

[0014] (Recycling Treatment of Laminated Film) After being used for its intended purpose, the laminated film of the present invention is preferably recycled by contacting it with moisture (hot water or steam) at a temperature of 100°C or higher, preferably above 100°C, depending on the type of functional layer C. Conventionally, water-soluble resins or the like have been used as a separation layer A for removing the functional layer C, and hot water at 90°C or lower under atmospheric pressure has been used in the recycling treatment. When a resin that dissolves in hot water at such temperatures is used, problems with durability and long-term storage may arise, particularly under high temperature and high humidity conditions. Therefore, it is desirable to use a resin that does not dissolve in hot water at 90°C or lower. On the other hand, when such a resin is used, the functional layer cannot be completely removed under conventional hot water recycling conditions, or the removal takes a long time. Therefore, it is desirable to carry out the recycling treatment under conditions different from conventional conditions. Furthermore, it is desirable to significantly prevent the quality of the recovered film from deteriorating compared to the quality before recovery. Details of the recycling treatment in the present invention will be described later.

[0015] (Layer structure of laminated film) The present invention is a laminated film having a base film in which at least a separation layer A composed of a first composition containing an amino resin and a support layer B composed of a second composition containing an aromatic polyester resin are laminated, and a functional layer C composed of a third composition that imparts a function to the surface of the base film, and the separation layer A is provided between the functional layer C and the support layer B. The separation layer A and the support layer B constitute the base film. The support layer B may be a single layer or a multilayer consisting of two or more layers. The support layer B can have any structure.

[0016] The functional layer C will be described in detail later, but examples thereof include a release layer, a hard coat layer, an adhesive layer, a decorative layer, a light-shielding layer, and an ultraviolet-shielding layer.

[0017] The layer structure of the laminated film of the present invention may be C / A / B, C / A / B / A, C / A / B / A / C, etc.

[0018] Furthermore, the laminate film of the present invention may also have an intermediate layer D between the separation layer A and the functional layer C, as long as it does not inhibit the functions of the separation layer A, the support layer B, and the functional layer C. In this case, the separation layer A, the intermediate layer D, and the support layer B constitute a base film. In this case, the layer structure of the laminate film of the present invention can be, for example, C / D / A / B, C / A / D / B, or C / D / A / D / B on one side of the support layer B. The other side of the support layer B may have the same layer structure, such as C / D / A / B / A / D / C, or a different layer structure, such as C / D / A / B / A, or a structure in which the support layer B is the surface. Note that the separation layers A, functional layers C, and intermediate layers D on both sides of the support layer B may have the same or different compositions, but preferably have the same composition. The intermediate layer D may be an easy-adhesion layer to improve adhesion.

[0019] In the above layer structure, it is important that the separation layer A is provided between the support layer B and the functional layer C. By decomposing the separation layer A under specific conditions, the support layer B and the functional layer C can be completely separated, and the support layer B can be recovered without impurities. The recovered support layer B contains only aromatic-containing polyester, and a highly pure resin composition can be obtained by material recycling. The resin composition is, for example, in pellet form and contains an aromatic polyester resin polyethylene terephthalate resin. Therefore, the laminate film of the present invention has a layer structure that is excellent in recyclability.

[0020] The separation layer A can be formed by coating the support layer B, for example.

[0021] For example, when forming the separation layer A by coating, the thickness of the separation layer A is preferably 0.01 μm or more. It is more preferably 0.1 μm or more, even more preferably 0.2 μm or more, even more preferably 0.4 μm or more, and particularly preferably 0.7 μm or more. When the thickness is 0.01 μm or more, the functional layer C can be sufficiently removed by hot water treatment. Due to limitations in the coating process, the substantial upper limit is 30 μm. That is, the thickness of the separation layer A is preferably 30 μm or less.

[0022] The ratio of the thickness of the separation layer A to the thickness of the laminate film is preferably 10% or less. The ratio of the thickness of the separation layer A to the laminate film may be 9% or less, or 8% or less. When the upper limit of the thickness ratio of the separation layer A is within the above range, the separation layer A can be decomposed under specific conditions. Furthermore, the ratio of the thickness of the separation layer A to the laminate film is preferably 0.01% or more, and may be 0.1% or more, 0.5% or more, or 1% or more. When the lower limit of the thickness ratio of the separation layer A is within the above range, it becomes easier to remove the functional layer C laminated on the separation layer A.

[0023] Next, the ratio of the thickness of the support layer B to the thickness of the laminate film is preferably 50% or more, more preferably 80% or more, and even more preferably 90% or more. The higher the ratio of the thickness of the support layer B, the more recyclable resin can be obtained, and the higher the recyclability of the laminate film as a whole.

[0024] The thickness ratio of the intermediate layer D to the thickness of the laminated film is not particularly limited, but is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less. When the intermediate layer D is provided in contact with the support layer B, the thickness is preferably 0.2 μm or less, more preferably 0.15 μm or less. The lower limit of the intermediate layer D is not particularly limited, but is preferably 0.01 μm or more.

[0025] (Support layer B) The support layer B is composed of a second composition containing an aromatic polyester resin. From the viewpoint of exhibiting the excellent properties of the aromatic polyester resin, the aromatic polyester resin is contained in 100% by mass of the resin constituting the second composition at preferably 90% by mass or more, more preferably 98% by mass or more, and most preferably 100% by mass.

[0026] The aromatic-containing polyester resin is not particularly limited and can be any commonly used one. However, a crystalline linear saturated polyester composed of an aromatic dibasic acid component and a diol component is preferred. For example, polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, or a copolymer primarily composed of these resin components is more preferred, with polyethylene terephthalate (PET) or polyethylene-2,6-naphthalate (PEN) being particularly preferred. Polyethylene terephthalate or polyethylene-2,6-naphthalate may contain copolymerization components in an amount of 5 mol% or less, more preferably 3 mol% or less, and even more preferably 2 mol% or less, based on 100 mol% of all dicarboxylic acid components and all glycol components. Preferred copolymerization components that may be contained include an isophthalic acid component, a terephthalic acid component (in the case of PEN), a 2,6-naphthalate component (in the case of PET), diethylene glycol, neopentyl glycol, etc.

[0027] The intrinsic viscosity of the aromatic polyester resin is preferably in the range of 0.45 dL / g to 1.10 dL / g. When the intrinsic viscosity is 0.45 dL / g or more, tearing of the aromatic polyester resin film can be prevented. When the intrinsic viscosity is 1.10 dL / g or less, the increase in filtration pressure is small, facilitating high-precision filtration.

[0028] The support layer B may have a multilayer structure of two or more layers, and a multilayer structure produced by coextrusion is also a preferred embodiment. Examples of multilayer structures include a two-layer structure (B1 / B2), a two-type three-layer structure (B2 / B1 / B2), and a three-type three-layer structure (B2 / B1 / B3), and a four-layer structure or more is also possible. In the case of a multilayer structure, it is preferable that the polyester resins constituting each layer are the same. In this case, "the same type" means that the difference in composition between the polyester resins constituting each layer is 5 mol% or less, more preferably 3 mol% or less, and even more preferably 2 mol% or less.

[0029] The difference in the composition of the polyester resin is the value obtained by subtracting the amount (mol%) of overlapping components from the total of all dicarboxylic acid components and all glycol components, 200 mol%, when all dicarboxylic acid components and all glycol components are taken as 100 mol%. For example, the difference between T / / E / D=100 / / 97 / 3 and T / / E / D=100 / / 99 / 1 is the difference between the overlapping T=100 mol%, E=97 mol% and The difference between T / / E / D = 100 / / 97 / 3 and T / / E / N = 100 / / 99 / 1 is 3 mol % excluding the overlapping T = 100 mol % and E = 97 mol %, and the difference between T / / E / D = 100 / / 97 / 3 and T / I / / E / D = 98 / 2 / / 98 / 2 is 3 mol % excluding the overlapping T = 98 mol %, E = 97 mol %, and D = 2 mol %. In the above, T is a terephthalic acid component, I is an isophthalic acid component, E is an ethylene glycol component, D is a diethylene glycol component, and N is a neopentyl glycol component.

[0030] The support layer B may contain antioxidants, heat stabilizers, matting agents, pigments, UV absorbers, fluorescent brighteners, plasticizers, lubricant particles, or other additives, as long as the object of the present invention is not impaired. When the support layer B has the above-mentioned multi-layer structure, these additives may be different in each layer. For example, only the B1 layer may contain a UV absorber, and only the B2 layer may contain lubricant particles.

[0031] (Separation Layer A) Conventionally, aliphatic polyesters such as polylactic acid or polyvinyl alcohol have been used for the separation layer A. However, when polylactic acid is used, problems such as poor solvent resistance, limited coating solvents for the functional layer, poor appearance of the functional layer, and inability to fully obtain the properties of the functional layer tend to occur. Furthermore, when polyvinyl alcohol is used, although solvent resistance is satisfactory, its high solubility in water means that the quality stability of the laminated film during long-term storage is poor.

[0032] The separation layer A is composed of a first composition containing an amino resin and is hydrolyzable by steam or hot water. Examples of amino resins include urea resins, melamine resins, benzoguanamine resins, aniline resins, and sulfonamide resins. The amino resins include not only those that are three-dimensionally crosslinked and cured, but also those that use a precursor used as a crosslinking agent (e.g., a melamine-based compound such as methylol melamine or a benzoguanamine-based compound) as a crosslinking agent.

[0033] From the viewpoint of hydrolysis property, the amino resin is preferably contained in an amount of 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, even more preferably 30% by mass or more, particularly preferably 40% by mass or more, most preferably 50% by mass or more, and may be contained in an amount of 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, based on 100% by mass of the resin constituting the first composition. When used as a crosslinking agent, the above content may be the amount added.

[0034] Although common melamine compounds can be used without any particular limitation, those obtained by condensing melamine with formaldehyde and having one or more triazine rings and one or more methylol groups and / or alkoxymethyl groups per molecule are preferred. Specifically, compounds obtained by etherifying a methylol melamine derivative obtained by condensing melamine with formaldehyde through a dehydration condensation reaction with a lower alcohol such as methyl alcohol, ethyl alcohol, isopropyl alcohol, or butyl alcohol are preferred. Examples of methylolated melamine derivatives include monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, and hexamethylol melamine. One or more compounds may be used. Precursors of other amino resins, such as benzoguanamine compounds, may also be used in combination.

[0035] The first composition may contain a resin other than the amino resin, and specific examples thereof include polyester-based resins, polyurethane-based resins, polyamide-based resins, polyacrylic-based resins, polyvinyl alcohol-based resins, etc. These resins other than the amino resins are preferably water-soluble resins or water-dispersible resins.

[0036] Among these, polyester resins or polyurethane resins are preferred in terms of ease of decomposition in water at 100°C or higher. Examples of polyester resins include aliphatic polyesters and aromatic polyesters. Examples of aliphatic polyester resins include polyglycolic acid, poly-L-lactic acid, poly-D-lactic acid, poly(β-hydroxybutyric acid), poly(ε-caprolactone), polyethylene succinate, polybutylene succinate, and poly(butylene succinate-butylene adipate). When the aliphatic polyester resin is polylactic acid, it is more preferred because it can suppress deterioration of the laminated film due to the storage environment and also achieve recyclability. The aliphatic polyester resin may be copolymerized.

[0037] Furthermore, in the case of aromatic polyesters (polyesters containing an aromatic dicarboxylic acid component as a constituent), it is preferable that an aliphatic dicarboxylic acid component such as succinic acid, glutaric acid, adipic acid, or sebacic acid is copolymerized as the dicarboxylic acid component, and the aliphatic dicarboxylic acid preferably accounts for 10 mol % or more, more preferably 20 mol % or more, even more preferably 30 mol % or more, and preferably 40 mol % or more, assuming that the total dicarboxylic acid components are 100 mol %. Note that when the aliphatic dicarboxylic acid component is contained in an amount of 50 mol % or more, it can be regarded as an aliphatic polyester resin.

[0038] Examples of polyurethane-based resins include those using polyester, polyether, polycarbonate, etc. as polyols, but those using the above polyester-based resins as polyols are preferred.

[0039] By using a polyester resin or a polyurethane resin, it is possible to achieve both suitable durability and decomposition characteristics in a wide orientation range in combination with the melamine resin, and both may be used in combination.

[0040] When a resin with low hydrolysis property such as a polyamide resin, a polyacrylic resin, or a polyvinyl alcohol resin is used, the content of the melamine resin is preferably selected from the above ranges of 20% by mass or more.

[0041] Depending on the purpose of use, the separation layer A may contain one or more of various additives such as inert particles such as inorganic particles, heat-resistant polymer particles, crosslinked polymer particles, fluorescent brighteners, ultraviolet inhibitors, infrared absorbing dyes, heat stabilizers, surfactants, antioxidants, etc. As the antioxidant, aromatic amine-based, phenol-based, etc. antioxidants can be used, and as the stabilizer, phosphorus-based, sulfur-based, amine-based, etc. stabilizers can be used.

[0042] The separation layer A may contain antioxidants, heat stabilizers, matting agents, pigments, ultraviolet absorbers, fluorescent brighteners, plasticizers, antistatic agents, or other additives, as long as the purpose of the present invention is not impaired.

[0043] The laminate film of the present disclosure has recyclability in that the support layer B can be recovered by decomposing the separation layer A under specific conditions, and one index of recyclability is the amount of residue of the separation layer A. In order to evaluate the amount of residue of the separation layer A of the laminate film, the value of the formula (I3 / I4) / (I1 / I2) is preferably 0.2 or less, more preferably 0.1 or less, even more preferably 0.05 or less, and particularly preferably 0.03 or less, based on the heights I1 to I4 of the absorbance peaks in the infrared absorption spectrum (where I1 is the absorbance at 1560 cm on the surface of the laminate film). －１ I indicates the height of the absorbance peak near 1715 cm on the surface of the laminated film. －１ I3 indicates the height of the absorbance peak near 1560 cm on the film surface after the laminated film was treated with hot water at 150 ° C. for 10 minutes. －１ I4 indicates the height of the absorbance peak near 1715 cm on the film surface after the laminated film was treated with hot water at 150 ° C. for 10 minutes. －１ (I3 / I4) / (I1 / I2) indicates the height of the absorbance peak near 1715 cm. From the viewpoint of recyclability, if the value of the formula (I3 / I4) / (I1 / I2) is 0.2 or less, it can be removed and recycled with hot water. The infrared absorption spectrum can be measured by irradiating infrared light onto the surface of the laminate film on which separation layer A is laminated. For films after 150°C hot water treatment, it can be measured by irradiating infrared light onto the surface of the laminate film on which separation layer A was laminated. That is, the absorbance peak heights I1 and I2 are the peak heights at each wavenumber of the infrared absorption spectrum obtained by irradiating infrared light onto the surface of the laminate film on which separation layer A was laminated, and the absorbance peak heights I3 and I4 are the peak heights at each wavenumber of the infrared absorption spectrum obtained by irradiating infrared light onto the surface of the laminate film on which separation layer A was laminated. 1715 cm －１ The absorbance peak near 1560 cm is a PET-derived peak. －１ Since the absorbance peaks in the vicinity are peaks derived from melamine, the amount of residue in the separation layer A can be evaluated by measuring the infrared absorption spectrum and finding the ratio of the respective absorbance peaks.

[0044] In evaluating the low-temperature stability of the laminated film, the value of the (I5 / I6) / (I1 / I2) formula is preferably 0.2 or more, more preferably 0.4 or more, and even more preferably 0.5 or more, based on the heights I1, I2, I5, and I6 of the absorbance peaks in the infrared absorption spectrum (where I1 is the absorbance at 1560 cm －１ I indicates the height of the absorbance peak near 1715 cm on the surface of the laminated film. －１ I5 indicates the height of the absorbance peak near 1560 cm on the film surface after the laminated film was treated with hot water at 90 ° C. for 2 hours. －１ I6 indicates the height of the absorbance peak near 1715 cm on the film surface after the laminated film was treated with hot water at 90 ° C. for 2 hours. －１ (I5 / I6) / (I1 / I2) indicates the height of the absorbance peak around 1715 cm. If the value of the formula (I5 / I6) / (I1 / I2) is 0.2 or more, the long-term stability under the storage environment will be better. The infrared absorption spectrum can be measured by irradiating the surface of the laminate film on which the separation layer A is laminated with infrared light. That is, the absorbance peak heights I1, I2, I5, and I6 are the peak heights at each wavenumber of the infrared absorption spectrum obtained by irradiating the surface of the laminate film on which the separation layer A is laminated with infrared light. 1715 cm －１ The absorbance peak near 1560 cm is a PET-derived peak. －１ Since the absorbance peaks in the vicinity are peaks derived from melamine, the low-temperature stability of the separation layer A can be evaluated by measuring the infrared absorption spectrum and determining the ratio of the respective absorbance peaks.

[0045] From the viewpoint of being able to form a thinner and more uniform separation layer A, the separation layer A is preferably formed by coating on the support layer B. When the separation layer A is uniform and thinner, the support layer B tends to peel off spontaneously when the laminated film is brought into contact with moisture at a temperature of 100°C or higher, resulting in better recyclability.

[0046] When forming separation layer A by coating, in order to increase the weight loss rate after treatment with hot water at 150°C for 10 minutes, the polyester resin may be a dispersion type in which polyester resin particles are dispersed in a solvent, or a type that is soluble in an organic solvent.

[0047] When a dispersion type is used, the average particle size of the polyester resin is preferably 0.01 to 20 μm, more preferably 0.1 to 10 μm, from the viewpoint of the formability and decomposability of the coating film.

[0048] (Intermediate Layer D) The composition of the intermediate layer D, which may be optionally provided, is not particularly limited. From the viewpoint of adhesion, the intermediate layer D is preferably made of an aromatic polyester or an aliphatic polyester resin, and more preferably made of polyethylene terephthalate or an aliphatic polyester resin. Furthermore, as the resin for the intermediate layer D, an olefin-based, ester-based, urethane-based, or acrylic copolymer can also be suitably used, and a blend resin of the above resins may also be used.

[0049] Furthermore, when the intermediate layer D is provided in contact with the support layer B, particularly when it is an easy-adhesion layer, the intermediate layer D preferably contains a copolymer polyester resin or a polyurethane resin, and preferably contains a copolymer polyester resin and a polyurethane resin, and the total amount of the copolymer polyester resin and the polyurethane resin among the resin components used in the intermediate layer D is preferably 50 mass % or more, more preferably 70 mass % or more. By adopting the above, foreign matter is less likely to be generated even if components of the intermediate layer are mixed in during material recycling.

[0050] The intermediate layer D may contain additives such as antioxidants, heat stabilizers, matting agents, pigments, ultraviolet absorbers, fluorescent brighteners, plasticizers, antistatic agents, lubricant particles, and other additives, as long as the object of the present invention is not impaired.

[0051] (Method for manufacturing base film) The support layer B of the base film used in the present invention is preferably a uniaxially or biaxially oriented film, more preferably a biaxially oriented film, from the viewpoints of mechanical strength, chemical resistance, heat resistance, etc. The stretching method is not particularly limited, and a sequential biaxial stretching method or a simultaneous biaxial stretching method is appropriately used.

[0052] When producing an oriented film, it is desirable to produce it through a melting process in which polyester chips, the raw resin, are melted in an extruder, a film-forming process in which the molten resin is extruded from the extruder to form an unstretched film, a stretching process in which the unstretched film is stretched in at least one direction, and a heat-setting process in which the stretched film is heat-treated.

[0053] In the melting step, the resin is introduced into a single-screw or twin-screw extruder, melted at a temperature above the melting point, preferably below 300°C, and then extruded into a sheet through a slit die and cooled and solidified on a casting roll to produce an unstretched film. When the support layer B has a multilayer structure, the respective resins are introduced into two or more extruders to extrude the raw materials for each layer, and the layers are merged using a multilayer feed block (e.g., a merging block having a rectangular merging section), extruded into a sheet through a slit die, and cooled and solidified on a casting roll to produce a multilayer unstretched film. Alternatively, a multi-manifold die may be used instead of the multilayer feed block.

[0054] The unstretched film is then stretched and oriented. The following describes the most commonly used sequential biaxial stretching method, specifically, a method in which the unstretched film is stretched longitudinally and then transversely in the width direction. First, in the longitudinal stretching step, the film is heated and stretched 1.1 to 6 times, preferably 2.5 to 4.5 times, between two or more rolls with different peripheral speeds. The heating method used here may be a method using a heated roll or a method using a non-contact heating medium, or a combination of these. In this case, the film temperature is preferably in the range of (Tg - 10°C) to (Tg + 50°C). The uniaxially stretched film is then introduced into a tenter and stretched 1.1 to 6 times, preferably 2.5 to 4.5 times, in the width direction at a temperature of (Tg - 10°C) to (Tm - 10°C).

[0055] Furthermore, after the stretching is completed, in order to reduce the thermal shrinkage of the film, it is preferable to carry out a heat setting treatment within 30 seconds, preferably within 10 seconds, in the heat setting step, and to carry out a longitudinal relaxation treatment and a transverse relaxation treatment of 0.5 to 10%.

[0056] The heat setting temperature is not particularly limited, but is preferably 200°C or higher because the transparency of the laminated film is improved and dimensional stability is obtained. It is more preferably 220°C or higher, and even more preferably 240°C or higher. The upper limit of the heat setting temperature is the melting point of the aromatic-containing polyester used in the support layer B.

[0057] When the intermediate layer D is provided in contact with the support layer B, the support layer B may be co-extruded during production, but the intermediate layer D is preferably laminated by coating. Coating may be performed after production of the support layer B (offline coating), but is preferably performed during the production process of the support layer B (in-line coating). In-line coating is preferably performed after production of the unstretched film and before introduction into the tenter, and is preferably performed between longitudinal stretching and introduction into the tenter. Drying after coating in in-line coating may be performed by heating in the tenter, or may be performed in a separate drying zone.

[0058] As a method for laminating the separation layer A, a method of laminating by coating can be preferably used. As the coating method, any known coating method can be applied, and conventionally known methods such as roll coating methods such as gravure coating and reverse coating, bar coating methods such as wire bars, die coating, spray coating, and air knife coating can be used. In addition, offline coating, which is a method of coating the separation layer A after producing the support layer B, may be used, or in-line coating, which is performed before or during the stretching process of the support layer B, can also be used.

[0059] When forming separation layer A on support layer B by coating, a solution or dispersion of the resin that constitutes separation layer A is prepared to an appropriate concentration, and this is applied to support layer B as a coating agent, and then the solvent or dispersion medium is dried, thereby forming separation layer A on support layer B.

[0060] The solvent may be any solvent that dissolves the amino resin and other resins used in combination, and is preferably one that takes into consideration the balance with the solubility of the aromatic polyester resin, such as a toluene / methyl ethyl ketone mixed solvent. Furthermore, the dispersion medium is preferably water from the viewpoint of ease of handling, and may contain a solvent with high affinity for water, such as an alcohol-based solvent.

[0061] When an intermediate layer D is provided on a support layer B and a separation layer A is further provided thereon, the intermediate layer D may be provided in-line and the separation layer A may be provided offline, or both may be provided in-line. When a separation layer A is provided on a support layer B and an intermediate layer D is further provided thereon, the separation layer A may be provided in-line and the intermediate layer D may be provided offline, or both may be provided in-line.

[0062] (Characteristics of the Base Film) Since the functional layer C is thin and has little effect on the physical properties, the physical properties of the base film are almost the same as those of the laminate film.

[0063] The thickness of the base film is preferably 2 to 500 μm, more preferably 5 to 250 μm, and even more preferably 11 to 100 μm. When the thickness is 2 μm or more, the film has a minimum rigidity and is easy to handle. When the thickness is more than 500 μm, the transportability of the base film when transported by multiple rolls and the handleability of the produced base film are reduced, making handling difficult.

[0064] The base film has high thermal dimensional stability even during post-processing at high temperatures. The heat shrinkage rate of the base film of the present invention when heated at 150°C for 30 minutes is 20.0% or less in both the longitudinal and transverse directions, more preferably 15.0% or less, even more preferably 5.0% or less, and particularly preferably 1.5% or less. When the heat shrinkage rate is 15.0% or less, high dimensional stability can be obtained even during high-temperature heat treatment processing at 150°C or higher, which can significantly contribute to improving productivity. Although a low heat shrinkage rate is preferable, from the standpoint of production, a lower limit of about 0.5% is considered.

[0065] The base film preferably has a breaking strength of 75 MPa or more in both the MD and TD directions. The breaking strength has a preferred lower limit of 100 MPa, a more preferred lower limit of 125 MPa, an even more preferred lower limit of 150 MPa, and an even more preferred lower limit of 175 MPa. A breaking strength of 75 MPa or more is preferable because it provides sufficient mechanical strength to the laminated film and can prevent problems such as elongation and slippage during the processing of the laminated film. Considering manufacturing considerations, the upper limit is considered to be 400 MPa.

[0066] The base film preferably has a breaking elongation of 50% or more in both the MD and TD directions. A breaking elongation of 50% or more is preferable because the mechanical elongation of the film is sufficient, and the occurrence of defects such as cracking and tearing during the film processing process can be significantly suppressed. 70% or more is more preferable, and 90% or more is even more preferable. In consideration of manufacturing, the upper limit is 300%. The upper limit is more preferably 150%.

[0067] The base film preferably has a peel strength of 20 mN / 15 mm or more, more preferably 100 mN / 15 mm or more. A peel strength of 20 mN / 15 mm or more is preferable because the layers of the base film do not easily peel off from each other and the laminate structure can be maintained. The higher the peel strength, the better, but from a manufacturing standpoint, the upper limit is 1000 mN / 15 mm.

[0068] The base film preferably has a tensile modulus of 2 GPa or more, more preferably 3 GPa or more, and even more preferably 3.5 GPa or more. A tensile modulus of 2 GPa or more is preferable in terms of flatness and handling. From the viewpoint of production, the upper limit is 10 GPa.

[0069] (Functional Layer C) Examples of the functional layer C include a release layer, a hard coat layer, a pressure-sensitive adhesive layer, a decorative layer, a light-shielding layer, and an ultraviolet-shielding layer. The functional layer C is composed of a third composition that imparts at least one of these functions to the surface of the base film. Therefore, for the pressure-sensitive adhesive layer, the decorative layer, the light-shielding layer, and the ultraviolet-shielding layer, a third composition is appropriately selected according to their functions. Therefore, the material of the third composition is not particularly limited. However, the current situation in which many used functional polyester films must be discarded or incinerated is that most functional layers C are made of resins and metals that are incompatible with the aromatic-containing polyester of the support layer B. Therefore, from the perspective of improving the recyclability of the laminate film, it is preferable to use a resin incompatible with the aromatic-containing polyester for the functional layer C. An example of an incompatible resin is a silicone resin. When the third composition contains a silicone resin, the third composition contains Si.

[0070] (Physical Properties of Laminate Film) The thickness of the laminate film of the present invention is preferably 2 to 500 μm, more preferably 5 to 250 μm, and even more preferably 11 to 100 μm. When the thickness is 2 μm or more, the film has a minimum rigidity and is easy to handle. When the thickness exceeds 500 μm, the transportability of the laminate film when transporting the laminate film with multiple rolls and the handleability of the produced laminate film are reduced, making handling difficult.

[0071] The laminated film of the present invention has high thermal dimensional stability even during post-processing at high temperatures. The heat shrinkage of the laminated film of the present invention when heated at 150°C for 30 minutes is 20.0% or less in both the longitudinal and transverse directions, more preferably 15.0% or less, even more preferably 5.0% or less, and particularly preferably 1.5% or less. When the heat shrinkage is 15.0% or less, high dimensional stability can be obtained even during high-temperature heat treatment processing at 150°C or higher, which can significantly contribute to improving productivity. A low heat shrinkage is preferable, but from a manufacturing standpoint, a lower limit of about 0.5% is considered.

[0072] The laminated film of the present invention preferably has a breaking strength of 75 MPa or more in both the MD and TD directions. The breaking strength has a preferred lower limit of 100 MPa, a more preferred lower limit of 125 MPa, an even more preferred lower limit of 150 MPa, and an even more preferred lower limit of 175 MPa. A breaking strength of 75 MPa or more is preferable because it provides sufficient mechanical strength to the laminated film and can prevent problems such as elongation and slippage during the processing of the laminated film. In consideration of manufacturing, the upper limit is considered to be 400 MPa.

[0073] The laminated film of the present invention preferably has a breaking elongation of 50% or more in both the MD and TD directions. A breaking elongation of 50% or more is preferable because the mechanical elongation of the film is sufficient, and the occurrence of defects such as cracking and tearing during the film processing step can be significantly suppressed. 70% or more is more preferable, and 90% or more is even more preferable. In consideration of manufacturing, the upper limit is 300%. The upper limit is more preferably 150%.

[0074] The laminated film of the present invention preferably has a tensile modulus of 2 GPa or more, more preferably 3 GPa or more, and even more preferably 3.5 GPa or more. A tensile modulus of 2 GPa or more is preferred in terms of flatness and handling. From the viewpoint of production, the upper limit is 10 GPa.

[0075] The surface of the laminated film of the present invention is preferably smooth, and when used as a release film for producing ceramic green sheets, which is a suitable application, it is preferably transparent. The haze is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less. The lower limit of the haze is the better, but it may be 0.1% or more, or even 0.3% or more. In order to reduce the haze, it is better not to make the film surface too uneven. However, from the viewpoint of handling ease against a rotating roll, it is preferable to form a certain amount of unevenness to provide a certain degree of slipperiness.

[0076] The total light transmittance of the laminated film is preferably 75% or more. In order to improve the accuracy of detecting internal foreign matter that could be a defect in the film, high transparency is preferable. Therefore, the total light transmittance of the film of the present invention is preferably 75% or more, more preferably 80% or more, even more preferably 85% or more, and particularly preferably 88% or more. In order to improve the accuracy of detecting internal foreign matter that could be a defect in the film, the higher the total light transmittance, the better, but it is technically difficult to achieve a total light transmittance of 100%. From a manufacturing standpoint, the total light transmittance is preferably less than 100%.

[0077] (Release Film for Producing Ceramic Green Sheet) The laminated film of the present invention can be used as a release film for producing a ceramic green sheet by providing a release layer as the functional layer C.

[0078] (Release layer) When a release layer is provided as functional layer C in the present invention, there are no particular limitations on the resin that constitutes it, and silicone resins, fluororesins, alkyd resins, various waxes, aliphatic olefins, etc. can be used, and each resin can be used alone or in combination of two or more types.

[0079] For example, the silicone resin used in the release layer of the present invention refers to a resin having a silicone structure within the molecule. Examples include curable silicones, silicone graft resins, and modified silicone resins such as alkyl-modified silicones. However, from the viewpoint of migration, it is preferable to use a reactive curable silicone resin. Examples of reactive curable silicone resins that can be used include addition reaction-based resins, condensation reaction-based resins, and ultraviolet or electron beam curable resins. More preferred are low-temperature curable addition reaction-based resins that can be processed at low temperatures, and ultraviolet or electron beam curable resins. The use of these resins allows low-temperature processing when coating polyester films. Therefore, heat damage to the polyester film during processing is reduced, resulting in a polyester film with high flatness. This also reduces defects such as pinholes when producing thin sheets such as ceramic green sheets.

[0080] Examples of silicone resins that use addition reactions include those that are cured by reacting polydimethylsiloxane, which has vinyl groups introduced into the terminals or side chains, with hydrogen siloxane using a platinum catalyst. In this case, it is more preferable to use a resin that can be cured within 30 seconds at 120°C, as this allows for processing at low temperatures. Examples include low-temperature addition cure types (LTC1006L, LTC1056L, LTC300B, LTC303E, LTC310, LTC314, LTC350G, LTC450A, LTC371G, LTC750A, LTC755, LTC760A, etc.) and thermal UV cure types (LTC851, BY24-510, BY24-561, BY24-562, etc.) manufactured by Dow-Toray Industries, and solvent addition + UV cure types (X62-5040, X62-5065, X62-5072T, KS5508, etc.) and dual cure cure types (X62-2835, X62-2834, X62-1980, etc.) manufactured by Shin-Etsu Chemical Co., Ltd.

[0081] An example of a condensation reaction silicone resin is one in which a three-dimensional crosslinked structure is formed by condensing a polydimethylsiloxane having an OH group at its terminal with a polydimethylsiloxane having an H group at its terminal using an organotin catalyst.

[0082] Examples of UV-curable silicone resins include, for example, the most basic type that utilizes the same radical reaction as normal silicone rubber crosslinking, those that introduce unsaturated groups to cause photocuring, those that use UV light to decompose onium salts to generate strong acids that then cleave epoxy groups to cause crosslinking, and those that crosslink via an addition reaction of thiol to vinyl siloxane. Also, electron beams can be used instead of UV light. Electron beams have stronger energy than UV light, making it possible to carry out a radical-based crosslinking reaction without using an initiator as in UV curing. Examples of resins that can be used include UV-curable silicones manufactured by Shin-Etsu Chemical Co., Ltd. (X62-7028A / B, X62-7052, X62-7205, X62-7622, ​​X62-7629, X62-7660, etc.), UV-curable silicones manufactured by Momentive Performance Materials (TPR6502, TPR6501, TPR6500, UV9300, UV9315, XS56-A2982, UV9430, etc.), and UV-curable silicones manufactured by Arakawa Chemical Industries, Ltd. (SilicoLease UV POLY200, POLY215, POLY201, KF-UV265AM, etc.).

[0083] The UV-curable silicone resin may be an acrylate-modified or glycidoxy-modified polydimethylsiloxane, etc. Good release properties can also be achieved by mixing such modified polydimethylsiloxane with a polyfunctional acrylate resin or epoxy resin, etc., and using the mixture in the presence of an initiator.

[0084] Other suitable resins include stearyl-modified, lauryl-modified, and other long-chain alkyl group-containing alkyd and acrylic resins, as well as alkyd-based resins, acrylic resins, and olefin-based resins obtained by reactions such as methylated melamine. When molding sheets for use in electronic components, etc., release agents that do not contain silicone are also preferred.

[0085] Examples of the aminoalkyd resins and aminoacrylic resins obtained by the reaction of methylated melamine include the Tesfine series manufactured by Showa Denko Materials Co., Ltd.

[0086] When the above resins are used in the release layer, they may be used alone or in a mixture of two or more. When two or more types are mixed, two or more types of silicone-based resins may be used, and it is also preferable to mix a plurality of different resin types, such as a binder resin and a silicone-based resin.

[0087] In particular, when molding a thin film sheet such as a ceramic green sheet, it is preferable that the release layer does not deform when peeled off, so it is preferable that the release layer is crosslinked and cured. Therefore, it is also preferable that the release layer contains a binder component, a crosslinking agent, etc. in addition to the silicone-based release agent.

[0088] The binder component contained in the release layer is not particularly limited, but is preferably a crosslinkable component that is crosslinked to increase the crosslink density of the release layer and improve the durability and solvent resistance of the release layer. Therefore, the binder component is preferably formed by reacting a resin having a reactive functional group with a crosslinking agent. It is also preferable that either the reactive functional group or the crosslinking agent is self-crosslinked. However, the present invention does not exclude an embodiment in which the binder component is formed solely from a resin having a reactive functional group or a crosslinking agent.

[0089] The resin having a reactive functional group is not particularly limited, but suitable examples include polyester resins, polyacrylic resins, polyurethane resins, polyolefin resins, etc. These resins preferably have at least one reactive functional group selected from the group consisting of a carboxyl group, a hydroxyl group, an epoxy group, an amino group, etc.

[0090] It is also preferable that the release layer contains a crosslinking agent. The crosslinking agent is not particularly limited, but melamine-based, isocyanate-based, carbodiimide-based, oxazoline-based, epoxy-based, etc. can be used, and one type or two or more types can be used in combination. Particularly preferred is a crosslinking agent that reacts with the reactive functional group introduced into the binder component.

[0091] The release layer may contain particles having a particle size of 1 μm or less, but from the viewpoint of preventing pinholes, it is preferable that the release layer does not substantially contain particles or other particles that form protrusions.

[0092] In order to adjust the release force, additives such as a light release additive or a heavy release additive, or additives such as an adhesion improver or an antistatic agent may be added to the release layer. In order to improve adhesion to the substrate, it is also preferable to subject the surface of the separation layer A or intermediate layer D to pretreatment such as anchor coating, corona treatment, plasma treatment, or atmospheric pressure plasma treatment before providing the release coating layer.

[0093] The thickness of the release layer may be set depending on the intended use and is not particularly limited, but is preferably in the range of 0.005 to 2.0 μm after curing. A release layer thickness of 0.005 μm or more is preferable because release performance is maintained. Furthermore, a release layer thickness of 2.0 μm or less is preferable because the curing time is not too long and there is no risk of uneven thickness of the sheet due to a decrease in the flatness of the release film. Furthermore, because the curing time is not too long, there is no risk of the resin constituting the release layer agglomerating, and there is no risk of protrusions being formed, which is preferable because pinhole defects in the sheet are unlikely to occur. That is, when the functional layer C is a release layer, the thickness of the functional layer C is preferably 0.005 to 2.0 μm.

[0094] The outer surface of the film on which the release layer is formed (the release layer surface of the entire coating film that is not in contact with the polyester film) is desirably flat so as to prevent defects from occurring in the sheet to be coated and molded thereon. The release layer, i.e., the surface of the functional layer C, preferably has an arithmetic mean roughness (Sa) of 5 nm or less and a maximum protrusion height (P) of 200 nm or less. More preferably, the arithmetic mean roughness is 5 nm or less and the maximum protrusion height (P) is 100 nm or less, and even more preferably, the arithmetic mean roughness is 5 nm or less and the maximum protrusion height (P) is 30 nm or less. If the arithmetic roughness is 5 nm or less and the maximum protrusion height (P) is 200 nm or less, defects such as pinholes do not occur during sheet formation, and the yield is good, which is preferable. The smaller the arithmetic mean roughness (Sa), the more preferable it is, but it may be 0.1 nm or more, or 0.3 nm or more. The smaller the maximum protrusion height (P), the more preferable it is, but it may be 1 nm or more, or 3 nm or more. The surface roughness of the functional layer C in the laminated film can be measured, for example, using a non-contact surface shape measurement system (VertScan R550H-M100, manufactured by Ryoka Systems Co., Ltd.) under the following conditions. The arithmetic mean roughness (Sa) can be calculated by, for example, taking the average value of five measurements, and the maximum protrusion height (P) can be calculated by measuring seven times and using the maximum value of the five measurements excluding the maximum and minimum values. (Measurement conditions) Measurement mode: WAVE mode Objective lens: 10x, 0.5x Tube lens Measurement area: 936 μm x 702 μm (Analysis conditions) Surface correction: 4th order correction Interpolation process: Full interpolation

[0095] The lower limit of the surface free energy of the release layer provided on the release film is 8 mJ / m ２ More preferably, it is 10 mJ / m or more. ２ or more, and 12 mJ / m ２ More preferably, it is 8 mJ / m or more. ２ If the thickness is more than this, repelling or the like is less likely to occur when the sheet dissolving solution is applied, which is preferable.

[0096] The upper limit of the surface free energy of the release layer provided on the release film is 45 mJ / m ２ It is preferably 40 mJ / m or less. More preferably, it is 40 mJ / m ２less than 35 mJ / m ２ More preferably, it is 45 mJ / m ２ If it is less than this, the releasability of the molded sheet is good, which is preferable.

[0097] The method for forming the release layer is not particularly limited, and a method is used in which a coating liquid in which a release resin is dissolved or dispersed is spread on one side of a base film by coating or the like, the solvent is removed by drying, and then the resulting film is dried by heating, heat-curing, or ultraviolet curing. At this time, the drying temperature during solvent drying and heat-curing is preferably 180°C or less, more preferably 150°C or less, and most preferably 120°C or less. The heating time is preferably 30 seconds or less, more preferably 20 seconds or less. At 180°C or less, the flatness of the film is maintained and there is little risk of uneven thickness of the sheet, which is preferable. At 120°C or less, the film can be processed without impairing the flatness of the film, and there is a further reduction in the risk of uneven thickness of the sheet, which is particularly preferable.

[0098] The surface tension of the coating liquid when applying the release layer is not particularly limited, but is preferably 30 mN / m or less. By adjusting the surface tension to the above range, the wettability after application can be improved and the unevenness of the coating surface after drying can be reduced.

[0099] Although there are no particular limitations on the coating liquid used to coat the release layer, it is preferable to add a solvent with a boiling point of 90° C. or higher. Adding a solvent with a boiling point of 90° C. or higher can prevent bumping during drying, level the coating film, and improve the smoothness of the coating film surface after drying. The amount of solvent added is preferably about 10 to 80% by mass of the total coating liquid.

[0100] As a method for applying the coating liquid, any known coating method can be applied, and conventionally known methods such as roll coating methods such as gravure coating and reverse coating, bar coating methods such as wire bar coating, die coating, spray coating, and air knife coating can be used.

[0101] (Ceramic Green Sheet and Ceramic Capacitor) Generally, a multilayer ceramic capacitor has a rectangular parallelepiped ceramic body. First internal electrodes and second internal electrodes are alternately provided inside the ceramic body along the thickness direction. The first internal electrodes are exposed at a first end face of the ceramic body. A first external electrode is provided on the first end face. The first internal electrode is electrically connected to the first external electrode at the first end face. The second internal electrode is exposed at a second end face of the ceramic body. A second external electrode is provided on the second end face. The second internal electrode is electrically connected to the second external electrode at the second end face.

[0102] A release film for producing ceramic green sheets is used to produce such multilayer ceramic capacitors. For example, it can be produced as follows. First, using the release film of the present invention as a carrier film, a ceramic slurry for forming a ceramic body is applied and dried. A conductive layer for forming a first or second internal electrode is printed on the applied and dried ceramic green sheet. A mother laminate is obtained by appropriately stacking and pressing ceramic green sheets, ceramic green sheets on which a conductive layer for forming a first internal electrode is printed, and ceramic green sheets on which a conductive layer for forming a second internal electrode is printed. The mother laminate is divided into multiple pieces to produce green ceramic bodies. The green ceramic bodies are fired to obtain ceramic bodies. Then, first and second external electrodes are formed to complete the multilayer ceramic capacitor.

[0103] (Hard Coat Layer) The laminate film of the present invention can be used as a surface protection film for protecting the surface of a display or the like by providing a hard coat layer as the functional layer C. The resin that forms the hard coat layer can be any resin, including acrylic, siloxane, inorganic hybrid, urethane acrylate, polyester acrylate, and epoxy, without any particular limitation. Two or more materials can be mixed and used, or particles of inorganic filler or organic filler can be added.

[0104] (Film Thickness of Hard Coat Layer) The film thickness of the hard coat layer is preferably 1 to 50 μm. A thickness of 1 μm or more is preferable because it cures sufficiently and the pencil hardness is high. Furthermore, by making the thickness 50 μm or less, curling due to cure shrinkage of the hard coat can be suppressed, and the handling properties of the film can be improved.

[0105] (Coating Method) The hard coat layer can be coated by any method, including a Mayer bar, gravure coater, die coater, knife coater, etc., without any particular limitation, and can be appropriately selected depending on the viscosity and film thickness.

[0106] (Curing Conditions) The hard coat layer can be cured by energy rays such as ultraviolet rays and electron beams, or by heat, and curing methods using ultraviolet rays or electron beams are preferred in order to reduce damage to the film.

[0107] (Pencil hardness) The pencil hardness of the hard coat layer is preferably 3H or more, more preferably 4H or more. If the pencil hardness is 3H or more, the hard coat layer is not easily scratched and does not reduce visibility. Generally, the pencil hardness of the hard coat layer is preferably high, but it may be 9H or less, 8H or less, or even 6H or less, and can be used without any practical problems.

[0108] (Characteristics of the Hard Coat Layer) The hard coat layer can be used to protect displays and the like by increasing the pencil hardness of the surface as described above, and a high transmittance is preferable for such optical applications. The total light transmittance of the hard coat film is preferably 87% or more, and more preferably 88% or more. A transmittance of 87% or more provides sufficient visibility. The total light transmittance of the hard coat film is generally preferable as it is higher, but from the standpoint of stable production, it is preferably 99% or less, and may be 97% or less. Furthermore, the haze of the hard coat film is generally preferably low, and preferably 3% or less. The haze of the hard coat film is more preferably 2% or less, and most preferably 1% or less. A haze of 3% or less can improve the visibility of the image. The lower the haze, the better, but from the standpoint of stable production, it is preferably 0.1% or more, and may be 0.3% or more.

[0109] The hard coat layer may further have other functions added thereto. For example, a hard coat layer having the above-mentioned functions, such as an antiglare layer having a certain pencil hardness, an antiglare antireflection layer, an antireflection layer, a low reflection layer, or an antistatic layer, is also preferably used in the present invention.

[0110] (Recycling Treatment) In the present invention, it is assumed that the above-described laminate film is subjected to a recycling treatment in which it is brought into contact with moisture at a temperature of 100° C. or higher. That is, after the laminate film of the present invention has been used for its intended purpose depending on the type of functional layer C, etc., it is recycled by being brought into contact with moisture at a temperature of 100° C. or higher. Specifically, the laminate film can be heat-treated using hot water and / or water vapor at a temperature of 100° C. or higher.

[0111] The liquid used in the recycling process may contain, in addition to water, other components that do not deteriorate the quality after recovery, but from the viewpoint of maintaining the quality after recovery, a liquid that does not contain acids, alkalis, organic solvents, etc. is preferred, and hot water is particularly preferred. Furthermore, while the steam may also contain other components that do not deteriorate the quality after recovery, from the same viewpoint, it is preferred that it does not contain any components other than water.

[0112] The amino resin used in the separation layer A is hydrolyzable. Therefore, the laminated film is brought into contact with moisture at a temperature of 100°C or higher to remove the functional layer C and the separation layer A, and then the support layer B is taken out and recycled as material, thereby obtaining a resin composition containing an aromatic polyester resin. This makes it possible to carry out the method for producing the resin composition of the present invention. Furthermore, the resin composition of the present invention is a resin composition containing an aromatic polyester resin obtained by such material recycling.

[0113] The temperature of the water vapor in the recycling process is preferably 100°C or higher and lower than the melting point of PET, 250°C. The upper limit of the water vapor temperature is preferably 240°C, more preferably 200°C, and particularly preferably 160°C. The lower limit of the water vapor temperature is preferably higher than 100°C, more preferably 105°C, and particularly preferably 110°C. The upper limit of the humidity RH is preferably 100%, more preferably 90%, and particularly preferably 80%. The lower limit of the humidity RH is preferably 50%, more preferably 60%, and particularly preferably 70%. The upper limit of the water vapor pressure is preferably 0.50 MPa, more preferably 0.30 MPa, and particularly preferably 0.20 MPa. The lower limit of the water vapor pressure is preferably 0.02 MPa, more preferably 0.1 MPa, and particularly preferably 0.15 MPa.

[0114] The temperature of the hot water in the recycling process is preferably 100°C or higher and lower than the melting point of PET, 250°C. The upper limit of the hot water temperature is preferably 240°C, more preferably 200°C, and particularly preferably 160°C. The lower limit of the hot water temperature is preferably above 100°C, more preferably 105°C, and particularly preferably 110°C. The upper limit of the hot water pressure is not particularly limited, but is preferably 22 MPa, which is the critical pressure. The lower limit of the hot water pressure is preferably 0.1 MPa, and more preferably 0.2 MPa. By setting the pressure to exceed atmospheric pressure, liquid hot water can be obtained. In the present invention, it is preferable to use hot water in the recycling process from the viewpoint of increasing the efficiency of contact with high-temperature water and efficiently hydrolyzing the separation layer A.

[0115] The time for the recycling treatment depends on the treatment temperature, but is preferably 0.1 to 300 minutes, more preferably 1 to 60 minutes, and even more preferably 2 to 30 minutes.

[0116] Although the recycling treatment can be carried out by batch processing on the laminated film in a rolled state, it is preferable to carry out the recycling treatment when the laminated film is unwound and not overlapped (in a film state) because moisture is less likely to diffuse inside. When carrying out the recycling treatment (hydrolysis) on the laminated film in a film state, in addition to a method of continuously processing while unwound using a long body, it can also be carried out by batch processing or continuous processing using a sheet body, small cut pieces, powder body, slurry body, flakes, etc.

[0117] After the recycling process, the separation layer A is hydrolyzed and removed or becomes brittle. In some cases, the remaining layers (functional layer C, intermediate layer D, etc.) provided on the separation layer A are also decomposed and removed, but even if they are not decomposed, the separation layer A is removed or becomes brittle, so they can be easily removed.

[0118] When continuous treatment is performed while unwinding a long sheet, a step of continuously peeling the support layer B from the remaining layer after the hot water treatment may be provided. If the remaining layer is in the form of a film, it can be peeled off by winding it separately from the winding of the support layer B. If the remaining layer cannot be wound into a film, it can be scraped off with a brush, scraper, or the like. Furthermore, in the case of sheets, a method of applying or strengthening physical force, such as by increasing stirring or using ultrasound, may be used in combination.

[0119] From the viewpoint of efficient continuous processing, it is preferable to crush the used laminate film into flakes using a crusher, and then treat the crushed film with hot water or the like while continuously supplying it. Specifically, in an apparatus equipped with a stirring tank that can be heated under pressure, the laminate film crushed into flakes is continuously supplied to the stirring tank, and after treatment with hot water or the like, the support layer B can be recovered by methods such as gravity separation and filtering. For example, the support layer B can be continuously recovered by scooping the flakes with a filter such as a wire mesh on a belt conveyor system and heating and drying them in an oven or the like.

[0120] The size of the flakes is preferably such that the longest part is 10 cm or less, more preferably 5 cm or less. A crusher or a shredder may be used as the pulverizer.

[0121] The resin composition containing the aromatic polyester resin obtained by material recycling as described above may be used as flakes used in the recycling process, or may be further pulverized into flakes or powder. It may also be formed into pellets for use. The pellets may be spherical, oval, cylindrical, prism-shaped, bale-shaped, or flattened bale-shaped, and from the standpoint of handleability, the weight is preferably 5 to 200 mg, more preferably 10 to 100 mg. The laminate film of the present invention is recycled by the method of the present invention, and the resulting recycled resin composition contains a high-purity aromatic polyester resin, such as polyethylene terephthalate resin, with little foreign matter. Therefore, the laminate film of the present invention has a sustainable structure with excellent recyclability.

[0122] This application claims the benefit of priority based on Japanese Patent Application No. 2024-123539, filed on July 30, 2024. The entire contents of the specification of Japanese Patent Application No. 2024-123539, filed on July 30, 2024, are incorporated herein by reference.

[0123] Next, the effects of the present invention will be explained using examples and comparative examples. First, the evaluation methods for the property values ​​used in the present invention are shown below. [Evaluation method] (1) Thickness The thickness of the laminated film was measured using a TH-104 manufactured by Tester Sangyo Co., Ltd. For Examples 1 to 5, the thickness of each layer of the laminated film was estimated from the coating amount.

[0124] (2) Breaking strength and breaking elongation: Measurements were made in accordance with JIS C 2318. A sample was cut into a strip shape with a length of 120 mm and a width of 10 mm in the MD and TD directions of the laminated film using a single-edged razor. The strip sample was then stretched using an Autograph AG-IS manufactured by Shimadzu Corporation, and the breaking strength (MPa) and breaking elongation (%) in each direction were determined from the obtained load-strain curve.

[0125] (3) Elastic modulus: Measured in accordance with JIS K 7127. A sample was cut into a strip shape with a length of 150 mm and a width of 15 mm in the MD and TD directions of the laminated film using a single-edged razor. The strip sample was then pulled using an Autograph AGS-X manufactured by Shimadzu Corporation, and the elastic modulus was determined from the obtained load-strain curve.

[0126] (4) Heat Shrinkage: Measured in accordance with JIS C 2318. The laminated film was cut into a width of 10 mm and a length of 190 mm, with the lengthwise direction being the measurement direction. Marks were made at 150 mm intervals, and the spacing (A) between the marks was measured. The laminated film was then placed in an oven in an atmosphere of 150°C and heat-treated at 150±3°C for 30 minutes under no load, after which the spacing (B) between the marks was measured. The heat shrinkage was then calculated using the following formula: Heat shrinkage (%) = (A - B) / A × 100. (5) Haze: The haze (%) of the laminated film was measured in accordance with JIS K 7136 using a haze meter (NDH70002, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0127] (6) Total Light Transmittance The total light transmittance (%) of the laminated film was measured in accordance with JIS K 7136 using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., model NDH70002).

[0128] (Evaluation of Laminated Film as Release Film) (7) Surface Free Energy Droplets of water (droplet volume 1.8 μL), diiodomethane (droplet volume 0.9 μL), and ethylene glycol (droplet volume 0.9 μL) were prepared on the release surface of the release film using a contact angle meter (Kyowa Interface Science Co., Ltd.: Fully Automatic Contact Angle Meter DM-701) under conditions of 25°C and 50% RH, and the contact angles were measured. The contact angles were measured 10 seconds after each liquid was dropped onto the release film. The contact angle data for water, diiodomethane, and ethylene glycol obtained by the above method were calculated using the Kitazaki-Hata theory to determine the dispersion component γsd, polar component γsp, and hydrogen bond component γsh of the surface free energy of the release film, and the sum of these components was used to determine the surface free energy γs. This calculation was performed using the calculation software in the contact angle meter software (FAMAS).

[0129] (8) Peel Force When Peeling Ceramic Green Sheet: A composition consisting of the following materials was stirred and mixed and dispersed for 60 minutes using a bead mill with 0.5 mm diameter glass beads as a dispersion medium to obtain a ceramic slurry: toluene 38.3 parts by weight, ethanol 38.3 parts by weight, barium titanate (HPBT-1 manufactured by Fuji Titanium Co., Ltd.) 64.8 parts by weight, polyvinyl butyral (S-LEC (registered trademark) BM-S manufactured by Sekisui Chemical Co., Ltd.) 6.5 parts by weight, DOP (dioctyl phthalate) 3.3 parts by weight. The release surface of the obtained release film sample was then coated with an applicator to a dried slurry thickness of 10 μm, and dried at 90°C for 1 minute to form a ceramic green sheet on the release film. The obtained release film with the ceramic green sheet was then de-ionized using a static eliminator (Keyence Corporation, SJ-F020) and then peeled off at a width of 30 mm at a peel angle of 90° and a peel speed of 10 m / min. The stress applied during peeling was measured and taken as the peeling force.

[0130] (9) Surface roughness of the functional layer C in the laminate film: This value was measured under the following conditions using a non-contact surface profile measurement system (VertScan R550H-M100, manufactured by Ryoka Systems Co., Ltd.). The arithmetic mean roughness (Sa) was calculated by averaging five measurements, and the maximum protrusion height (P) was calculated by measuring seven times and excluding the maximum and minimum values, and the maximum value of the five measurements was used.

[0131] (Measurement conditions) Measurement mode: WAVE mode Objective lens: 10x, 0.5x Tube lens Measurement area: 936 μm x 702 μm (Analysis conditions) Surface correction: 4th order correction Interpolation processing: Full interpolation

[0132] (10) 150°C Hot Water Treatment The laminated film obtained in the examples was cut into pieces of 3 mm or less square, and 10 g of the laminated film cut into approximately 3 mm x 3 mm pieces and 300 mL of pure water were placed in an MMJ-500 manufactured by O-M Labotec Co., Ltd. Using a metal filter with a mesh size of 0.5 mm, the cut sample was held in water and heated to 150°C. The pressure at that time was 0.4 MPa. After heat treatment at 150°C for 10 minutes, the sample was cooled to room temperature and collected.

[0133] After the hot water treatment, the film was taken out and washed with running water at room temperature for about 5 minutes to remove any foreign matter or residues such as decomposition products present on the film, and the following evaluations were carried out.

[0134] (11) 90°C Hot Water Treatment The laminated film obtained in the example was cut into a size of 30 mm x 100 mm to prepare a measurement sample. Next, a Thermal Robo TR-4 (manufactured by AS ONE Corporation) was filled with water to prepare 90°C hot water. A 500 mL metal tray was immersed in the hot water, and approximately 300 mL of hot water was poured into the tray. Furthermore, the measurement sample was placed in the tray with clips attached to both ends so that the entire sample was immersed in the hot water, and treated for 2 hours while maintaining the temperature at 90°C. The measurement sample was then removed from the hot water, lightly rinsed in pure water at room temperature, and lightly wiped dry with a Kimtowel.

[0135] (12) Infrared absorption spectrum measurement (melamine amount ratio and separation layer A residue amount) Measurement was carried out under the following conditions using an FT-IR device (Agilent Technologies Cary 660 FTIR). The measurement was carried out on the surface of the laminated film on which the separation layer A and functional layer C were provided. Conditions: Single reflection ATR (total reflection measurement method) Attachment: Thunderdome Internal reflection element: Ge Incident angle: 45° Number of accumulations: 32 1715 cm －１ The peak near 1560 cm is a PET-derived peak. －１ The peak at 1715 cm was determined as a peak derived from melamine, and the peak top height was calculated. －１ The height of the absorbance peak near 1560 cm －１The ratio of the height of the absorbance peaks around 1560 cm on the surface of the laminate film was calculated. The amount of residual separation layer was evaluated by calculating the formula (I3 / I4) / (I1 / I2) from the heights of the absorbance peaks I1 to I4 in the infrared absorption spectrum (where I1 is the ratio of the height of the absorbance peaks around 1560 cm on the surface of the laminate film). －１ I indicates the height of the absorbance peak near 1715 cm on the surface of the laminated film. －１ I3 indicates the height of the absorbance peak near 1560 cm on the film surface after the laminated film was treated with hot water at 150 ° C. for 10 minutes. －１ I4 indicates the height of the absorbance peak near 1715 cm on the film surface after the laminated film was treated with hot water at 150 ° C. for 10 minutes. －１ (The heights of the absorbance peaks around 150° C. are shown.) I1 / I2 is the melamine amount ratio before the hot water treatment, and I3 / I4 is the melamine amount ratio after the 150° C. hot water treatment.

[0136] (13) Evaluation of low-temperature stability (melamine amount ratio and separation layer A residue amount after 90°C hot water treatment) For the evaluation of low-temperature stability, the melamine amount ratio was calculated from the absorbance peak heights I1, I2, I5, and I6 in the infrared absorption spectrum using the formula (I5 / I6) / (I1 / I2) (where I1 is the melamine amount ratio at 1560 cm on the surface of the laminated film). －１ I indicates the height of the absorbance peak near 1715 cm on the surface of the laminated film. －１ I5 indicates the height of the absorbance peak near 1560 cm on the film surface after the laminated film was treated with hot water at 90 ° C. for 2 hours. －１ I6 indicates the height of the absorbance peak near 1715 cm on the film surface after the laminated film was treated with hot water at 90 ° C. for 2 hours. －１ (The height of the absorbance peak near the 90°C temperature is shown.) I5 / I6 is the melamine amount ratio after the 90°C hot water treatment.

[0137] (14) Evaluation of Release Layer Residue Amount The sample treated with hot water at 150 ° C was measured using a fluorescent X-ray analyzer (XL3t-950S manufactured by Thermo Fisher Scientific). Measurement was performed in Cu / Zn mode in mineral mode (FP method), with the measurement field of view being a 3 mm diameter spot. The amount of Si element (ppm by mass) in the obtained sample was evaluated as the amount of release layer residue. Note that the amount of Si element before hot water treatment was 80,000 ppm, and the amount of Si element in the film composed only of support layer B was detected as 20,000 ppm as background.

[0138] (Example 1) (1) Production of Polyethylene Terephthalate Resin 1 (PET Resin 1) The temperature of an esterification reactor was raised, and when it reached 200°C, a slurry consisting of 86.4 parts by mass of terephthalic acid and 64.4 parts by mass of ethylene glycol was charged, and 0.017 parts by mass of antimony trioxide and 0.16 parts by mass of triethylamine were added as catalysts while stirring. Next, the temperature was raised under pressure to a gauge pressure of 3.5 kgf / cm. ２ A pressurized esterification reaction was carried out under conditions of 240°C and 240°C. Thereafter, the pressure inside the esterification reactor was returned to atmospheric pressure, and 0.071 part by mass of magnesium acetate tetrahydrate was added, followed by 0.014 part by mass of trimethyl phosphate. The temperature was then raised to 260°C over 15 minutes, and 0.012 part by mass of trimethyl phosphate was added, followed by 0.0036 part by mass of sodium acetate. After 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reactor, and the temperature was gradually raised from 260°C to 280°C under reduced pressure, and a polycondensation reaction was carried out at 285°C.

[0139] After the polycondensation reaction was completed, the resin was filtered through a Naslon (registered trademark) filter with a 95% cutoff diameter of 5 μm, extruded from a nozzle in the form of a strand, cooled and solidified using cooling water that had been previously filtered (pore diameter: 1 μm or less), and cut into pellets. The resulting PET resin 1 had a melting point of 257° C., an intrinsic viscosity of 0.616 dl / g, and was substantially free of inert particles and internally precipitated particles.

[0140] (2) Production of base film PET resin 1 was used as the raw material for support layer B. It was dried under reduced pressure (1 Torr) at 135°C for 6 hours and then fed to an extruder. The raw material fed to the extruder was melt-extruded into a sheet from a die at 280°C. A filter medium made of sintered stainless steel with a filtration particle size of 10 μm (initial filtration efficiency: 95%) was used for the filter.

[0141] The extruded resin was cast onto a cooling drum having a surface temperature of 30° C., and adhered to the surface of the cooling drum using an electrostatic application method, followed by cooling and solidification to form an unstretched film having a thickness of 300 μm.

[0142] The obtained unstretched sheet was heated to a film temperature of 75° C. using a group of heated rolls, and then stretched 3.4 times in the longitudinal direction using a group of rolls with different peripheral speeds.

[0143] The uniaxially stretched film was then gripped with clips and stretched transversely at a temperature of 100°C and a stretch ratio of 4.2. The film was then heat-treated at 240°C for 15 seconds and then relaxed at 210°C to a 3% relaxation ratio to obtain a base film having a thickness of 30 μm.

[0144] (3) Formation of Separation Layer A: PLA1 resin (D-body ratio 14% and Mw 50,000) was used as the aliphatic polyester resin, and a melamine-based compound (full-ether type methylated melamine, manufactured by Sanwa Chemical Co., Ltd., product name: Nikalac MW-30M, weight average degree of polymerization 1.3, main component: hexamethoxymethylmelamine) was used as the amino resin. The PLA1 resin and melamine-based resin were dissolved in a toluene / methyl ethyl ketone (5:5) solution to a concentration of 8% by mass and 2% by mass, respectively, and p-toluenesulfonic acid (manufactured by Hitachi Chemical Co., Ltd., product name: Dryer 900) was added as a catalyst in an amount of 2% by mass relative to the total amount of resin components to form a coating agent.

[0145] Next, the coating material was applied onto the surface of the base film by gravure coating and dried at 150° C. for 15 seconds.

[0146] (4) Formation of Functional Layer C 100 parts by mass of a UV-curable silicone resin (UV9300 manufactured by Momentive, solid content concentration 100% by mass) and 1 part by mass of the curing catalyst bis(alkylphenyl)iodonium hexafluoroantimonate were diluted with a toluene / methyl ethyl ketone / heptane (=3:5:2) solution to prepare a release agent solution with a solid content of 2% by mass. The release agent solution was applied using a reverse gravure coater so that the thickness after drying was 0.1 μm, and then dried with hot air at 90° C. for 30 seconds. Immediately after that, the solution was irradiated with ultraviolet light (300 mJ / cm ) using an electrodeless lamp (H bulb manufactured by Fusion Corporation). ２ ) was performed to form a functional layer C on the surface of the separation layer A, thereby obtaining a laminated film that is a release film. The functional layer C is located on the separation layer A of the base film, and the separation layer A is provided between the functional layer C and the support layer B.

[0147] The physical properties of the obtained laminate film are shown in Table 2. The laminate film of Example 1 had good solvent resistance. Therefore, it was able to fully demonstrate its performance regardless of the type of functional layer. Furthermore, after the laminate film of Example 1 was subjected to hot water treatment, the amount of separation layer residue measured using the ATR method was 0.04, and the amount of release layer residue measured using fluorescent X-ray measurement was 20,000 ppm. Therefore, it was possible to material recycle the high-purity recovered PET resin, which contained almost no components of the separation layer or release layer.

[0148] (Examples 2 to 5) In Examples 2 to 5, laminate films were obtained in the same manner as in Example 1, except for changing the conditions as shown in Table 1. The laminate films of Examples 2 to 5 had good solvent resistance. Therefore, they were able to fully demonstrate their performance regardless of the type of functional layer. Furthermore, after the laminate films of Examples 2 to 5 were subjected to hot water treatment at 150°C, the amount of separation layer residue measured using the ATR method and the amount of release layer residue measured using fluorescent X-ray measurement were as shown in Table 2. Therefore, it was possible to material recycle high-purity recovered PET resin that contained almost no components of the separation layer or release layer.

[0149]

[0150]

[0151] (Production of film using recovered resin and evaluation of properties) The laminated film obtained in Example 1 was left to stand for 4 hours under water vapor at 121°C, 100% RH, and 0.2 MPa using an EHS-221 manufactured by Espec Corporation. After treatment, the decomposed separation layer A and functional layer C were washed away with hot water to obtain only the PET film. Here, the separation layer A and functional layer C were easily peeled from the support layer B.

[0152] The obtained support layer B (PET film) was recycled to produce a resin composition containing polyethylene terephthalate resin. Specifically, the removed PET film was cut and re-pelletized by melt extrusion at 280°C to obtain recycled PET pellets. The obtained PET pellets were again re-pelletized by melt extrusion at 280°C, and the re-melt-processed pelletized resin composition (hereinafter referred to as recycled PET resin 1) was used as the recycled raw material.

[0153] A laminated film was obtained in the same manner as in Example 1, except that recycled PET resin 1 was used as the PET raw material. The physical properties of the obtained laminated film are shown in Table 3. The film had the same physical properties as when PET resin 1 was used.

[0154] Laminated films were obtained in the same manner using the resins recycled in Examples 2 to 5. As shown in Table 3, the physical properties of the obtained films were equivalent to those of the films before recycling.

[0155]

[0156] As described above, the laminated films of Examples 1 to 5 can be recycled regardless of the type of a wide variety of functional layers, and deterioration of the quality after recycling compared to the quality before recycling can be significantly suppressed.

[0157] (Comparative Examples 1 and 2) In Comparative Example 1, a laminate film was obtained in the same manner as in Example 1, except that the conditions were changed as shown in Table 1. In Comparative Example 2, a laminate film was obtained in the same manner as in Comparative Example 1, except that the resin used in the separation layer was PLA2 (D-body ratio 1% and Mw 190,000). Comparative Examples 1 and 2 did not contain an amino resin. In Comparative Example 1, due to poor solvent resistance, the separation layer dissolved when the release layer was applied, causing the surface to become rough, and it was not possible to obtain a laminate film that could withstand evaluation. In Comparative Example 2, a PLA2 resin with high crystallinity and improved solvent resistance was used, but due to insufficient solvent resistance, it was also not possible to obtain a film laminated with a release layer.

[0158] As described above, the laminate film of the present invention can be recycled regardless of the type of a wide variety of functional layers, and deterioration of the quality after recycling compared to the quality before recycling can be significantly suppressed. The laminate film of the present invention is suitably used, for example, as a release film for producing ceramic green sheets.

Claims

1. A laminated film having a base film including a separation layer A composed of a first composition containing an amino resin and a support layer B composed of a second composition containing an aromatic polyester resin, and a functional layer C composed of a third composition that imparts a function to the surface of the base film, wherein the separation layer A is disposed between the functional layer C and the support layer B.

2. The laminated film according to claim 1, wherein the amino resin is a melamine compound or a urea resin.

3. The laminated film according to claim 1, wherein the amino resin is a melamine-based compound and the content of the amino resin in the separation layer A is 5% or more by mass.

4. The laminated film according to claim 1, wherein the first composition is a water-soluble resin or a water-dispersible resin.

5. The laminate film according to claim 1, wherein the first composition contains at least one resin selected from the group consisting of polyester resins, polyurethane resins, polyamide resins, polyacrylic resins, and polyvinyl alcohol resins.

6. The laminate film of claim 1, wherein the first composition comprises an aliphatic polyester.

7. The laminate film according to claim 6, wherein said aliphatic polyester is polylactic acid, said aromatic polyester resin is polyethylene terephthalate resin, and said third composition contains a resin incompatible with polyethylene terephthalate resin.

8. The laminated film according to claim 1, wherein the heights I1 to I4 of the absorbance peaks in the infrared absorption spectrum satisfy the following formula: (I3 / I4) / (I1 / I2)≦0.2 (where I1 is the absorbance peak height at 1560 cm on the surface of the laminated film). －１ I indicates the height of the absorbance peak near 1715 cm on the surface of the laminated film. －１ I3 indicates the height of the absorbance peak near 1560 cm on the film surface after treating the laminated film with hot water at 150 °C for 10 minutes. －１ I4 indicates the height of the absorbance peak near 1715 cm on the film surface after treating the laminated film with hot water at 150 °C for 10 minutes. －１ (Indicates the height of the absorbance peak near the 9. The laminated film according to claim 1, wherein the heights of absorbance peaks I1, I2, I5, and I6 in the infrared absorption spectrum satisfy the following formula: (I5 / I6) / (I1 / I2) ≥ 0.2 (where I1 is the absorbance peak height at 1560 cm on the surface of the laminated film). －１ I indicates the height of the absorbance peak near 1715 cm on the surface of the laminated film. －１ I5 indicates the height of the absorbance peak near 1560 cm on the film surface after treating the laminated film with hot water at 90 °C for 2 hours. －１ I6 indicates the height of the absorbance peak near 1715 cm on the film surface after treating the laminated film with hot water at 90 ° C. for 2 hours. －１ (Indicates the height of the absorbance peak near the 10. The laminated film according to claim 1, wherein the ratio of the thickness of said separation layer A to the thickness of said laminated film is 10% or less.

11. The laminated film according to claim 1, wherein the thickness of said separation layer A is 0.01 μm or more.

12. The laminate film of claim 1, wherein the third composition contains a silicone release component.

13. A laminated film according to claim 1, wherein the maximum protrusion height (P) of the surface of the functional layer C is 200 nm or less, and the arithmetic mean roughness (Sa) of the surface of the functional layer C is 5 nm or less.

14. The laminated film according to claim 1, which is a release film for producing ceramic green sheets.

15. A method for treating a laminated film, comprising the step of contacting the laminated film according to any one of claims 1 to 14 with moisture at a temperature of 100°C or higher.

16. A method for recovering aromatic polyester resin from a laminated film, comprising the step of recovering said support layer B from the laminated film treated by the method of claim 15.

17. A material recycled polyester resin containing an aromatic polyester resin recovered by the method of claim 16.

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