Laminated polyester film, method for manufacturing laminated polyester film, and laminate

Abstract

The present invention provides a laminated polyester film that can be peeled off a mating member with light force, and can also be peeled off a mating member with light force after heating. [Solution] A polyester resin base layer has a resin layer on at least one side, the 23°C tape peel strength of the resin layer is 2.0 N / 19 mm or less, and the load is 0.5 N / cm 2 The static friction force between the resin layers in the above case is 10 N / 9 cm 2 The above is a laminated polyester film.

Description

[Technical Field]

[0001] This invention relates to a laminated polyester film, a method for manufacturing the same, and a laminate. [Background technology]

[0002] Laminated films with excellent release properties are materials that can be peeled off at the interface with adjacent mating components. They are used as protective films for adhesive layers in adhesive products and as carrier films in the processing of various industrial products. In recent years, in particular, the demand for laminated films with excellent release properties has been increasing from the perspective of improving the manufacturing speed and quality of various products.

[0003] As a laminated film with excellent release properties, a film containing a silicone compound in the release layer (hereinafter referred to as silicone release film) is the most commonly used due to its industrial productivity and heat resistance (for example, Patent Document 1). However, because silicone release films contain a silicone compound in the release layer, the surface free energy of the release layer is low, which can lead to poor coating of the mating component due to repulsion of the paint used to form the mating component or the inclusion of air bubbles, and may result in the mating component not being formed uniformly.

[0004] On the other hand, for optical and electronic components that require a high degree of precision, a surface protection film having an adhesive layer on a laminated film substrate is attached to prevent surface damage during processing, assembly, inspection, and transportation (Patent Document 2). To protect the adhesive layer of such a surface protection film until it is bonded to the optical component, a release film (separator) that has been treated for mold release is bonded to it. While silicone release films have conventionally been used as separators (Patent Document 3), in recent years it has become known that a release film that does not contain silicone compounds (hereinafter referred to as a non-silicone release film) can be suitably used to prevent the surface of the mating component of the surface protection film from being contaminated with silicone compounds (Patent Document 4).

[0005] To address these challenges, studies are being conducted on using long-chain alkyl group-containing resins, olefin resins, fluorine compounds, and wax-based compounds, particularly long-chain alkyl group-containing resins, as the main materials for non-silicone release films (for example, Patent Documents 5-7). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2010-155459 [Patent Document 2] Japanese Patent Publication No. 2016-017109 [Patent Document 3] Japanese Patent Publication No. 2012-224811 [Patent Document 4] Japanese Patent Publication No. 2019-194337 [Patent Document 5] Japanese Patent Publication No. 2004-351626 [Patent Document 6] Japanese Patent Publication No. 2004-230772 [Patent Document 7] Japanese Patent Publication No. 2015-199329 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, when non-silicone release films described in Patent Documents 5 to 7 are used as separators for surface protection films, etc., the layers provided on the release film by coating, etc. (e.g., adhesive layers) tend to peel more severely compared to when silicone release films are used. In addition, non-silicone release films generally have the problem that the peeling force of the layers provided on the release film by coating, etc. increases significantly with heating. For example, when the present inventors verified the film described in Patent Document 5, they found that when an adhesive tape was bonded to the resin layer and peeled off after heating, the adhesive tape peeled off significantly severely. Furthermore, when a long-chain alkyl group-containing resin and a crosslinking agent are used in combination, as in the film described in Patent Document 6, or when a long-chain alkyl acrylate resin and a melamine resin are used in combination, as in the film described in Patent Document 7, the change in the peeling force of the adhesive tape due to heating is small, but the peeling force of the adhesive tape remains high, making peeling difficult even after heating.

[0008] Therefore, the objective of the present invention is to overcome the above-mentioned drawbacks and provide a laminated polyester film that can be peeled off a mating member with light force, and can also be peeled off a mating member with light force after heating. [Means for solving the problem]

[0009] In view of the above problems, the present inventors conducted diligent studies and found that by using a laminated polyester film having specific physical properties, it is possible to create a separator for surface protective films that is excellent in terms of release properties and control of peeling force by heating, thus completing the present invention. The present invention consists of the following configuration: [I] A polyester resin base layer having a resin layer on at least one side, wherein the 23°C tape peel strength of the resin layer is 2.0 N / 19 mm or less, and the load is 0.5 N / cm 2 The static friction force between the resin layers in the above case is 10 N / 9 cm 2 The above is a laminated polyester film, [II] When the tape peeling force of the resin layer at 23°C is R1 and the tape peeling force of the resin layer after heating at 100°C for 1 hour is R2, the ratio of R1 to R2, R2 / R1, is 2.0 or less, the laminated polyester film according to [I], [III] When analyzing the surface of the resin layer by time-of-flight secondary ion mass spectrometry, the ratio (P / K) of the peak intensity (P) of the fragment of the positive ion derived from dimethylsiloxane to the peak intensity (K) of the fragment of the positive ion detected at the maximum intensity is less than 0.01, the laminated polyester film according to [I] or [II], [IV] The laminated polyester film according to any one of [I] to [III], wherein the resin layer contains a component having a melting point of -50°C or higher and 30°C or lower, [V] The laminated polyester film according to any one of [I] to [IV], wherein the resin layer is formed from a resin composition containing a release agent and at least one compound selected from an oxazoline compound, a melamine compound, and a carbodiimide compound, [VI] The laminated polyester film according to any one of [I] to [V], containing at least one of a biomass raw material and a recycled raw material, [VII] A laminate having an adhesive layer on the surface on the resin layer side of the laminated polyester film according to any one of [I] to [VI], [VIII] A method for producing a laminated polyester film according to any one of [I] to [VI], comprising a coating step of applying a resin composition for forming the resin layer to at least one side of a polyester film, a stretching step of stretching the polyester film coated with the resin composition in at least one axial direction, and a heat treatment step of heating the stretched polyester film to 150°C or higher to form a resin layer, in this order,

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a laminated polyester film that can peel off a mating member with a light force and can also peel off the mating member with a light force even after heating.

Mode for Carrying Out the Invention

[0011] Hereinafter, the laminated polyester film of the present invention will be described in detail. The laminated polyester film of the present invention has a resin layer on at least one side of a polyester resin base material layer, and the tape peel strength of the resin layer at 23 ° C is 2.0 N / 19 mm or less, and the static friction force between the resin layers at a load of 0.5 N / cm 2 is 10 N / 9 cm 2 or more.

[0012] First, the meaning of these physical properties and examples of control methods in the laminated polyester film of the present invention will be described. The laminated polyester film of the present invention has a resin layer on at least one side of a polyester resin base material layer from the viewpoint of reducing deterioration of the quality of a member (hereinafter sometimes referred to as a mating member) bonded to the surface, and the tape peel strength of the resin layer at 23 ° C is 2.0 N / 19 mm or less, preferably 1. / 19 mm or less. When the tape peel strength of the resin layer at 23 ° C exceeds 2.0 N / 19 mm, the mating member may not be peeled off from the resin layer but may be broken during the process of peeling the laminated polyester film from the mating member, deteriorating the quality of the mating member. The lower limit of the tape peel strength of the resin layer at 23 ° C is not particularly limited, but is preferably 0.01 N / 19 mm or more from the viewpoint of suppressing peeling between the mating member and the resin layer in the film conveyance process. The tape peel strength of the resin layer at 23 ° C is a value obtained by the measurement method described later.

[0013] The laminated polyester film of the present invention has a static friction force between the resin layers at a load of 0.5 N / cm 2 of 10 N / 9 cm 2 or more from the viewpoint of ensuring releasability even after passing through a heating process. The lower limit of the static friction force between the resin layers at a load of 0.5 N / cm 2 is more preferably 20 N / 9 cm 2 or more. The upper limit of the static friction force between the resin layers at a load of 0.5 N / cm 2 is preferably 500 N / 9 cm 2 or less, and 400 N / 9 cm2 The following is more preferable: Load 0.5 N / cm 2 By adjusting the static friction force between the resin layers to the aforementioned range, it becomes easy to create a laminated polyester film that excels at controlling the peeling force between the resin layer and the mating component after heating.

[0014] Load 0.5 N / cm 2 The static friction force between resin layers can be measured using a commercially available friction coefficient meter conforming to the American Society for Testing and Materials (ASTM) standard number D1894-63, and details of the measurement method will be described later. Satisfying the above characteristics means that the laminated polyester film excels at controlling the peeling force between the resin layer and the mating member after heating. Generally, the static friction force between resin layers is used as an indicator of the strength of the tackiness or adhesion between resin layers, but as a result of diligent research by the inventors, the present invention uses the 23°C tape peeling force of the resin layer and a load of 0.5 N / cm². 2 We found that by adjusting the static friction force between resin layers to a specific range, it becomes easy to create a laminated polyester film that excels at controlling the peeling force between the resin layer and the mating component after heating.

[0015] The peel strength of the resin layer at 23°C and the load of 0.5 N / cm 2 To control the static friction force between resin layers within the preferred range described above, it is effective to use release agents and materials, such as those described later, and in particular, to use a copolymer containing long-chain alkyl groups as a release agent. Furthermore, from a process perspective, a method of forming a resin layer on a film uniaxially stretched in the longitudinal direction using an in-line coating method is also effective. Details will be described later. These methods can also be used in combination as appropriate.

[0016] In the laminated polyester film of the present invention, from the viewpoint of ensuring release properties even after the heating process, it is preferable that the ratio R2 / R1 is 2.0 or less, where R1 is the tape peel strength of the resin layer at 23°C and R2 is the tape peel strength of the resin layer after heating at 100°C for 1 hour. R1 and R2 can be measured using a commercially available peel tester, and the details of the measurement method will be described later.

[0017] By setting R2 / R1 to 2.0 or less, the mating material can be peeled off with light force even after heating. From the above viewpoint, R2 / R1 is more preferably 1.5 or less, and even more preferably 1.2 or less. There are no particular limitations on the method for controlling the value of R2 / R1, but typical methods include adjusting the types and contents of the release agent (A), binder resin (B), and reactive compound (C) in the resin composition for forming the resin layer, as described later.

[0018] The laminated polyester film of the present invention preferably has a resin layer on at least one side of the polyester resin substrate layer, from the viewpoint of reducing deterioration of the quality of the mating member, and when the surface of the resin layer is analyzed by secondary ion mass spectrometry, the P / K ratio is less than 0.01, where K is the peak intensity of the positive ion fragment detected at maximum intensity and P is the peak intensity of the positive ion fragment derived from dimethylsiloxane.

[0019] The P / K ratio can be calculated from the peak obtained by time-of-flight secondary ion mass spectrometry, and details of the time-of-flight secondary ion mass spectrometry method will be described later. For a resin layer to satisfy the above characteristics means that it contains few components derived from silicone compounds (e.g., dimethylsiloxane). This characteristic contributes to reducing the degradation of the mating component's quality when used as a release film, for example. More specifically, if the mating component to be bonded to the resin layer is an optical component or an electronic component, the migration of silicone compounds to the mating component is suppressed, reducing problems such as poor conductivity, poor insulation, and pinhole defects. In other words, by reducing the dimethylsiloxane-derived components in the resin layer, it becomes possible to reduce contamination of the mating component's surface by silicone compounds.

[0020] From the above viewpoint, a P / K of less than 0.01 is preferable, and if the laminated polyester film is used in optical components, electronic components, etc., where malfunctions can occur with even trace amounts of silicone compounds, then less than 0.001 is more preferable. Furthermore, from the above viewpoint, the smaller the P / K, the better, and its lower limit is 0. There are no particular limitations on how to make the P / K less than 0.01, but typical methods include adjusting the composition and film thickness of the resin layer, which will be described later. More specifically regarding the composition, one example is to not use (or reduce the amount of) silicone compounds in the resin layer, and to include long-chain alkyl resins, olefin resins, fluorine compounds, wax compounds, etc., preferably long-chain alkyl resins. More specifically regarding methods for adjusting the film thickness, examples include adjusting the concentration of solids contained in the resin composition for resin layer formation, which will be described later, and adjusting the amount of resin composition applied by the depth of the groove of the wire bar used in the bar coating method.

[0021] The laminated polyester film of the present invention has a resin layer on at least one side of the polyester resin substrate layer. Polyester resin is a general term for polymers whose main chain is an ester bond, and preferably uses a polymer whose main component is at least one component selected from ethylene terephthalate, propylene terephthalate, ethylene-2,6-naphthalate, butylene terephthalate, propylene-2,6-naphthalate, ethylene-α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate, etc. Here, the main component is a component that is present in an amount exceeding 50 mol% and not exceeding 100 mol% when the total component of the resin is set to 100 mol%.

[0022] In the laminated polyester film of the present invention, it is preferable to use a polyester film as the polyester resin substrate layer from the viewpoint of heat resistance and smoothness. A polyester film refers to a sheet-like molded article mainly composed of polyester resin, and the main component refers to a component that is included in the total constituent components in an amount exceeding 50% by mass and not exceeding 100% by mass, and the same interpretation can be applied hereinafter. If a sheet-like molded article contains multiple types of polyester resins, the molded article can be considered a polyester film if the total amount exceeds 50% by mass.

[0023] The above polyester resin may contain copolymer units of less than 50 mol%, preferably 30 mol%, in the total constituent units as needed. Furthermore, when heat or shrinkage stress is applied to the laminated polyester film, it is preferable to use polyethylene terephthalate film or polyethylene-2,6-naphthalate film, which have excellent heat resistance and rigidity, as the polyester resin base layer. Here, polyethylene terephthalate film refers to a film in which polyethylene terephthalate (including copolymers) accounts for more than 50% by mass and up to 100% by mass of the total components constituting the film, and the same interpretation applies to polyethylene-2,6-naphthalate film. In cases where multiple resins equivalent to polyethylene terephthalate are included due to differences in copolymerization amounts, the polyethylene terephthalate content shall be calculated by summing all the relevant resin components. This point is also the same for polyethylene-2,6-naphthalate film.

[0024] From the viewpoint of reducing environmental impact, the laminated polyester film of the present invention preferably contains at least one of biomass raw materials and recycled raw materials, and more preferably the polyester resin substrate layer contains at least one of these raw materials. Here, biomass refers to plant-derived organic compounds produced by photosynthesis from carbon dioxide and water. When biomass is burned, it usually turns back into carbon dioxide and water, so biomass can be used as a so-called carbon-neutral renewable energy source. Furthermore, biomass raw materials refer to polyester resin containing biomass-derived constituent units.

[0025] When the proportion of plant-derived carbon to the total carbon is defined as the biomass percentage, for example, in an ethylene terephthalate unit, if only the ethylene glycol component is entirely plant-derived, the biomass percentage is theoretically 20%. To increase the biomass percentage further, the terephthalic acid must also be plant-derived, which would have a greater effect on reducing environmental impact but would increase production costs. For the ethylene glycol and terephthalic acid components, a combination of petroleum-derived and plant-derived components may be used.

[0026] From the viewpoint of achieving an environmental load reduction effect, the lower limit of the biomass content of the polyester constituting the film is preferably 5% or more, more preferably 10% or more, and even more preferably 13% or more. An environmental load reduction effect can be expected when the biomass content is 5% or more. On the other hand, if only the reduction of environmental load is considered, a higher upper limit of biomass content is preferable, with 100% being the upper limit. However, from the viewpoint of balancing production costs and the reduction of environmental load, it is practically preferable to have a biomass content of 20% or less.

[0027] Furthermore, a known method for analyzing the presence or absence of biomass raw materials is, for example, the carbon isotope analysis described on the website of the Japan Bioplastics Association (http: / / www.jbpaweb.net / bp / ). 14 One possible method is to use C).

[0028] Recycled raw materials are raw materials obtained by recovering and reusing polyester resin that has been processed into chemical products once or multiple times. Examples of chemical products used to obtain recycled raw materials for the laminated polyester film of the present invention include uncoated portions at both ends in the width direction that are cut and removed during the manufacturing process of the laminated polyester film of the present invention, recovered products of other polyester films, and polyester resin products that have been distributed in forms other than film, such as PET bottles.

[0029] When the laminated polyester film of the present invention contains recycled materials, it is preferable that the content of recycled materials be 90% by mass or less of 100% by mass of polyester resin in the laminated polyester film. By limiting the use of recycled materials to 90% by mass or less, the amount of highly crystalline polyester that has been converted into a chemical product is reduced, thereby reducing the decrease in thermal properties, transparency, and discoloration of the resulting laminated polyester film. The recycled materials may be used in either the polyester resin substrate or the resin layer, but from the viewpoint of reducing the impact on the mating member, it is preferable to use them in the polyester resin substrate rather than the resin layer that is bonded to the mating member.

[0030] The polyester resin substrate layer of the above-mentioned laminated polyester film is preferably a biaxially oriented polyester film from the viewpoint of thermal stability and mechanical strength. A biaxially oriented polyester film is a polyester film that exhibits a pattern oriented in two orthogonal directions by wide-angle X-ray diffraction. Generally, a biaxially oriented polyester film is obtained by stretching an unstretched polyester sheet in two orthogonal directions. More specifically, for example, an unstretched polyester sheet is stretched by approximately 2.5 to 5.0 times in the longitudinal and width directions, and then heat-treated to complete the crystal orientation. By using a biaxially oriented polyester film as the polyester resin substrate, the thermal stability, especially the dimensional stability and mechanical strength of the laminated polyester film, is improved, as is its flatness. Here, the longitudinal direction refers to the direction in which the film travels during the manufacturing process (in the case of a film roll, this corresponds to the winding direction of the film), and the width direction refers to the direction perpendicular to the longitudinal direction within the film plane.

[0031] Furthermore, the polyester resin substrate layer may contain various additives, such as antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents, nucleating agents, etc., to an extent that does not impair its properties.

[0032] The thickness of the polyester resin substrate layer is not particularly limited and can be appropriately selected depending on the application and type. However, from the viewpoint of achieving sufficient mechanical strength and improving handling properties, it is usually preferably 5 to 500 μm, more preferably 10 to 250 μm, and particularly preferably 15 to 150 μm. Furthermore, the polyester resin substrate may be a single-layer film or a composite film produced by co-extrusion.

[0033] The resin layer in the laminated polyester film of the present invention is located on at least one side of the aforementioned polyester resin substrate layer. The resin layer is necessary for easy peeling in the process of peeling the laminated polyester film from the laminate after laminating mating components such as molten resin, adhesive layer, and surface coating layer on it.

[0034] In the laminated polyester film of the present invention, the resin layer preferably has a film thickness of 20 nm to 400 nm, and more preferably 30 nm to 200 nm, from the viewpoint of quality and release properties. By setting the film thickness of the resin layer to 20 nm to 400 nm, it becomes easy to provide a resin layer with uniform release properties on the polyester film that will become the polyester resin substrate layer. By setting the film thickness of the resin layer to 400 nm or less, it is possible to suppress the increase in manufacturing costs and reduce unevenness and streaks that occur when applying the resin composition for resin layer formation to the polyester film, thereby maintaining good quality in the resulting laminated polyester film.

[0035] The following describes the resin composition for forming the resin layer of the laminated polyester film of the present invention. Preferably, the resin layer of the laminated polyester film of the present invention is formed from a resin composition containing a release agent (A) and at least one reactive compound (C) selected from oxazoline compounds, melamine compounds, and galbodiimide compounds. With this configuration, and by further adjusting the type and amount of each component to a suitable range, a load of 0.5 N / cm can be achieved. 2By adjusting the static friction force between the resin layers to a suitable range, it becomes easier not only to provide the resin layer with good release properties from the mating member, but also to provide excellent control over the peeling force due to heating (i.e., to impart the characteristic of being able to peel off the mating member with light force even after heating).

[0036] Also, a load of 0.5 N / cm 2 From the viewpoint of adjusting the static friction force between resin layers to a desirable range, it is preferable that the resin layer contains a component (resin composition) having a melting point of -50°C or higher and 30°C or lower. With such a configuration, it becomes easy to create a resin layer that can be peeled off the mating member with light force even after heating. There are no particular limitations on the method of controlling the melting point of the resin composition, but typical methods include adjusting the type and content of the release agent (A) in the resin composition for forming the resin layer, as described below.

[0037] In the laminated polyester film of the present invention, the release agent (A) refers to a compound that can impart release properties (i.e., properties that reduce the surface free energy of the resin and facilitate separation from the mating member) to the surface of the resin layer. Examples of release agents (A) that can be used in the laminated polyester film of the present invention include long-chain alkyl group-containing resins, olefin resins, fluorine compounds, and wax-based compounds. Among these, long-chain alkyl group-containing resins are preferred because they can impart good release properties to the laminated polyester film. When using a long-chain alkyl group-containing resin as the release agent (A), it is preferable to include a hydrophilic functional group in addition to the long-chain alkyl group, from the viewpoint of ensuring solubility in aqueous solvents, as described later. Also, a load of 0.5 N / cm 2 From the viewpoint of adjusting the static frictional force between resin layers to a desirable range, it is preferable that the release agent (A) has a melting point between -50°C and 30°C.

[0038] In other words, a particularly preferred release agent (A) of the present invention is a copolymer resin having a long-chain alkyl group and a hydrophilic functional group. Examples of hydrophilic functional groups include hydroxyl groups, carboxyl groups, amino groups, amide groups, glycidyl groups, isocyanate groups, vinyl groups, acrylic groups, and methacrylic groups.

[0039] Commercially available resins containing long-chain alkyl groups may be used. Specifically, the "Ashiorezin" (registered trademark) series of long-chain alkyl compounds manufactured by Ashio Sangyo Co., Ltd., the "Piroyl" series of long-chain alkyl compounds manufactured by Ipposha Yushi Kogyo Co., Ltd., and the "Rezem" series of aqueous dispersions of long-chain alkyl compounds manufactured by Chukyo Yushi Co., Ltd. can be used.

[0040] Another preferred embodiment of the release agent (A) is a copolymer having an alkyl group polymerized in an aqueous solvent (more preferably a copolymer of a vinyl compound having an alkyl group with 6 or more carbon atoms), from the viewpoint of ensuring solubility in aqueous solvents, as described later. Polymerization in an aqueous solvent can be carried out by known methods, such as solution polymerization, bulk polymerization, precipitation polymerization, suspension polymerization, and emulsion polymerization, but emulsion polymerization and suspension polymerization are preferred from the viewpoint of ensuring solubility of the release agent (A) in aqueous solvents, as described later. Even with such an embodiment, the load is 0.5 N / cm. 2 This makes it easier to set the static friction force between the resin layers within a suitable range, and improves the release effect of the release agent (A) even after heating.

[0041] Furthermore, the presence or absence of alkyl groups with 6 or more carbon atoms in the resin layer can be evaluated from the release film, for example, by using the intensity of the signal corresponding to the alkyl group obtained by TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry). In this case, by using the ion sputtering method in combination, it is possible to perform continuous measurements in the depth direction (thickness direction), and the distribution state of alkyl group-containing compounds can also be evaluated.

[0042] In the laminated polyester film of the present invention, a binder resin (B) may be used in the resin layer to reduce film breakage of the resin layer. The resin used as the binder resin is not particularly limited, but from an economic standpoint, it is preferable to include polyester resin, acrylic resin, and urethane resin.

[0043] The polyester resin used as the binder resin (B) in the laminated polyester film of the present invention is preferably one having ester bonds in the main chain or side chain, and obtained by polycondensation of a dicarboxylic acid and a diol. Aromatic, aliphatic, and alicyclic dicarboxylic acids can be used as the dicarboxylic acid used as the raw material for the polyester resin. Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 2,5-dimethylterephthalic acid, 1,4-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2-bisphenoxyethane-p-p'-dicarboxylic acid, and phenylindanedicarboxylic acid. Examples of aliphatic and alicyclic dicarboxylic acids include succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedionic acid, dimer acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and their ester-forming derivatives. These can be used individually or in combination.

[0044] The diol components used as raw materials for the polyester resin include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl- 1,6-Hexanediol, 1,2-Cyclohexanedimethanol, 1,3-Cyclohexanedimethanol, 1,4-Cyclohexanedimethanol, 2,2,4,4-Tetramethyl-1,3-Cyclobutanediol, 4,4'-Thiodiphenol, Bisphenol A, 4,4'-Methylenediphenol, 4,4'-(2-Norbornylidene)diphenol, 4,4'-Dihydroxybiphenol, o-, m-, and p-Dihydroxybenzene, 4,4'-Isopropylidenephenol, 4,4'-Isopropylidenebinediol, Cyclopentane-1,2-Diol, Cyclohexane-1,2'-Diol, Cyclohexane-1,2-Diol, Cyclohexane-1,4-Diol, etc. can be used. These can be used individually or in combination of multiple types.

[0045] Furthermore, as the binder resin (B), it is also possible to use modified polyester copolymers, such as block copolymers or graft copolymers modified with acrylic, urethane, epoxy, etc.

[0046] The acrylic resin that can be used as the binder resin (B) is not particularly limited, but examples of monomer components constituting the acrylic resin include alkyl acrylates, alkyl methacrylates (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, lauryl, stearyl, cyclohexyl, phenyl, benzyl, and phenylethyl groups), hydroxyl group-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, and 2-hydroxypropyl methacrylate, acrylamide, and methacrylamide. Monomers containing amide groups such as N-methylacrylamide, N-methylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N,N-dimethylolacrylamide, N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, and N-phenylacrylamide; monomers containing amino groups such as N,N-diethylaminoethyl acrylate and N,N-diethylaminoethyl methacrylate; monomers containing epoxy groups such as glycidyl acrylate and glycidyl methacrylate; and monomers containing carboxyl groups or their salts, such as acrylic acid, methacrylic acid, and their salts (lithium salts, sodium salts, potassium salts, etc.). These monomers may be polymerized individually or copolymerized in combination with other monomers.

[0047] The urethane resin used as the binder resin (B) is not particularly limited, but it is preferably a resin obtained by reacting a polyhydroxy compound and a polyisocyanate compound by known urethane resin polymerization methods such as emulsion polymerization and suspension polymerization.

[0048] Examples of polyhydroxy compounds include polyethylene glycol, polypropylene glycol, polyethylene-propylene glycol, polytetramethylene glycol, hexamethylene glycol, tetramethylene glycol, 1,5-pentanediol, diethylene glycol, triethylene glycol, polycaptolactone, polyhexamethylene adipate, polyhexamethylene sebacate, polytetramethylene adipate, polytetramethylene sebacate, trimethylolpropane, trimethylolethane, pentaerythritol, polycarbonate diol, and glycerin.

[0049] Examples of polyisocyanate compounds that can be used include hexamethylene diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate, adducts of tolylene diisocyanate and trimethylenepropane, and adducts of hexamethylene diisocyanate and trimethylolethane.

[0050] The reactive compound (C) that forms the resin layer in the laminated polyester film of the present invention is a load of 0.5 N / cm, which is a parameter that facilitates the control of peeling force by heating. 2 From the viewpoint of adjusting the static frictional force between resin layers, it is preferable to contain at least one compound selected from melamine compounds, oxazoline compounds, and carbodiimide compounds, and among these, melamine compounds are particularly preferred because they facilitate the formation of crosslinks with the release agent (A) and the binder resin (B).

[0051] Examples of melamine compounds that can be used as reactive compound (C) include melamine, methylolated melamine derivatives obtained by condensing melamine with formaldehyde, compounds obtained by reacting methylolated melamine with a lower alcohol to partially or completely etherify it, and mixtures thereof. Furthermore, the melamine compound may be a monomer or a condensate consisting of two or more polymers, or a mixture thereof.

[0052] Lower alcohols that can be used for etherification include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, and isobutanol. Functional groups include imino groups, methylol groups, or alkoxymethyl groups such as methoxymethyl groups and butoxymethyl groups, which are present in one molecule. Examples include imino-type methylated melamine resins, methylol-type melamine resins, methylol-type methylated melamine resins, and fully alkyl-type methylated melamine resins. Among these, methylolated melamine resins are particularly preferred.

[0053] The oxazoline compound that can be suitably used as the reactive compound (C) is one which has an oxazoline group as a functional group in the compound, and is preferably an oxazoline group-containing copolymer obtained by copolymerizing at least one monomer containing an oxazoline group with at least one other monomer.

[0054] Examples of monomers containing an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. One or more of these can be used as a mixture. Among these, 2-isopropenyl-2-oxazoline is preferred because it is readily available industrially.

[0055] In oxazoline compounds, at least one other monomer used with a monomer containing an oxazoline group is a monomer copolymerizable with the oxazoline group-containing monomer, such as acrylic acid esters or methacrylic acid esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, and 2-ethylhexyl methacrylate; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, and maleic acid; acrylonitrile; and methacrylonitrile. Any unsaturated nitriles, unsaturated amides such as acrylamide, methacrylamide, N-methylolacrylamide, and N-methylolmethacrylamide, vinyl esters such as vinyl acetate and vinyl propionate, vinyl ethers such as methyl vinyl ether and ethyl vinyl ether, olefins such as ethylene and propylene, halogen-containing α,β-unsaturated monomers such as vinyl chloride, vinylidene chloride, and vinyl fluoride, and α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene can be used, and one or more of these can be used as mixtures.

[0056] As for the oxazoline compound, commercially available products can be used, and examples of those that can be suitably used include "Epocross" (registered trademark) WS-300, WS-500, and WS-700 manufactured by Nippon Shokubai Co., Ltd.

[0057] A carbodiimide compound that can be suitably used as the reactive compound (C) is a compound that has at least one carbodiimide group or a cyanamide group in a tautomer relationship therewith as a functional group within its molecule. Specific examples of such carbodiimide compounds include dicyclohexylmethanecarbodiimide, dicyclohexylcarbodiimide, tetramethylxylylenecarbodiimide, and urea-modified carbodiimide, and these may be used individually or in combination as long as they satisfy the scope of the present invention.

[0058] The resin composition for forming the resin layer may contain a solvent or dispersion medium (hereinafter abbreviated as "solvent"). That is, various components may be dissolved or dispersed in a solvent to form a resin composition, which may then be applied to a polyester film that will become the polyester resin substrate layer. When this method is used, a laminated polyester film with a resin layer can be obtained by drying the solvent after application and then heating the film.

[0059] In the laminated polyester film of the present invention, it is preferable to use an aqueous solvent as the solvent for the resin composition for forming the resin layer. Here, an aqueous solvent refers to water, or a mixture of water and water-soluble organic solvents such as methanol, ethanol, isopropyl alcohol, butanol, ketones such as acetone and methyl ethyl ketone, and glycols such as ethylene glycol, diethylene glycol, and propylene glycol in any ratio. Using an aqueous solvent not only suppresses the rapid evaporation of the solvent during the heating process, thereby forming a uniform resin layer, but is also superior in terms of environmental impact.

[0060] In the laminated polyester film of the present invention, the resin composition for forming the resin layer can be prepared by mixing and stirring a release agent (A), binder resin (B), reactive compound (C), and aqueous solvent in any order and in a desired weight ratio, as needed (binder resin (B) is optional). Then, various additives such as lubricants, inorganic particles, organic particles, surfactants, antioxidants, and thermal initiators can be mixed and stirred in any order, as needed, without degrading the properties of the resin layer formed by the resin composition. Methods of mixing and stirring include shaking the container by hand, stirring with a magnetic stirrer or stirring blades, ultrasonic irradiation, vibration dispersion, etc.

[0061] In the resin composition for forming the resin layer in the present invention, there is a preferred content for the release agent (A). Specifically, when the entire resin layer (the sum of the release agent (A), binder resin (B), and reactive compound (C) in the resin composition for forming the resin layer) is considered as 100% by mass, the release agent (A) is preferably 5% by mass or more and 100% by mass or less, more preferably 8% by mass or more and 50% by mass or less, and particularly preferably 8% by mass or more and 35% by mass or less. When the release agent (A) is 5% by mass or more, the release properties of the release layer are at a sufficient level. On the other hand, when the release agent (A) is 100% by mass or less, the release properties are improved, the shedding of the release agent (A) from the laminated polyester film is reduced, and contamination of the mating member by the release agent (A) can be suppressed.

[0062] Furthermore, there is a preferred range for the content of reactive compound (C). Specifically, when the entire resin layer (the sum of the mold release agent (A), binder resin (B), and reactive compound (C) in the resin composition for forming the resin layer) is considered as 100% by mass, the reactive compound (C) is preferably 10% by mass or more, more preferably 45% by mass or more, and particularly preferably 60% by mass or more. When the reactive compound (C) satisfies the above content, the load of the laminated polyester film is 0.5 N / cm. 2 This makes it easier to control the static friction force between resin layers within a desirable range, and also facilitates the control of the peeling force due to heating. On the other hand, the upper limit of the content depends on the blending amounts of the release agent (A) and the binder resin (B), but is 95% by mass or less, preferably 90% by mass or less.

[0063] On the other hand, while the binder resin (B) is an optional component, if it is added, the blending ratio can be adjusted so that the aforementioned release agent (A) and reactive compound (C) have a desirable content.

[0064] The method for manufacturing the laminated polyester film of the present invention will now be described. The method for manufacturing the laminated polyester film of the present invention is characterized by comprising, in this order: a coating step of applying a resin composition for forming a resin layer to at least one surface of a polyester resin substrate sheet; a stretching step of stretching the polyester resin substrate sheet after the resin composition has been applied in at least one axial direction; and a heat treatment step of heating the stretched polyester resin substrate sheet to 150°C or higher to form a resin layer. In other words, the method for manufacturing the laminated polyester film of the present invention employs an in-line coating method in which the resin composition is applied within the polyester film manufacturing process. Although it is also possible to manufacture the laminated polyester film of the present invention using an off-coat method in which the resin composition is applied to the film after it has been formed, using the in-line coating method makes it easier to thin the resin layer more uniformly and to improve the heat resistance and peelability of the laminated polyester film before and after heating. Here, the polyester resin substrate sheet refers to the polyester film that becomes the polyester resin substrate layer when it becomes a laminated polyester film, and the resin composition for forming the resin layer is the composition that forms the resin layer when it becomes a laminated polyester film.

[0065] The present invention relates to a method for producing a laminated polyester film, which includes a coating step of applying a resin composition for forming a resin layer to at least one surface of a polyester resin substrate sheet. In the coating step, the aforementioned preferred resin composition for forming a resin layer is applied, and this resin composition becomes a resin layer upon heating in a subsequent heat treatment step. The resin composition for forming a resin layer used here may include, in addition to the aforementioned release agent (A) and reactive compound (C), various additives such as the aforementioned binder resin (B), crosslinking catalyst, lubricant, inorganic particles, organic particles, surfactant, antioxidant, and thermal initiator. The present invention relates to a method for manufacturing a laminated polyester film, which includes a stretching step in which a polyester resin substrate sheet coated with a resin composition is stretched in at least one axial direction. In this configuration, the resin composition is applied before stretching, so the method for applying the resin composition for resin layer formation is an in-line coating method. In the present invention's method for manufacturing a laminated polyester film, stretching is performed after the coating step, so the resin composition for resin layer formation is applied to a substantially amorphous unstretched (unoriented) polyester film obtained by melt extrusion and rapid cooling (hereinafter sometimes referred to as "film A"), a uniaxially stretched (uniaxially oriented) polyester film that has been stretched in the longitudinal direction (hereinafter sometimes referred to as "film B"), or a biaxially stretched (biaxially oriented) polyester film before heat treatment that has been further stretched in the width direction (these correspond to polyester resin substrate sheets).

[0066] By applying a resin composition for resin layer formation to either film A or film B before crystal orientation is complete, evaporating the solvent, and then stretching film A or B in a uniaxial or biaxial direction, the polyester film formation, application of the resin composition and drying of the solvent, and heat treatment (i.e., formation of the resin layer) can be performed in a continuous process. This not only offers advantages in terms of manufacturing costs, but also allows for high-temperature heat treatment of the resin layer while reducing deformation and thermal shrinkage of the polyester film by completing the crystal orientation of the polyester resin substrate after drying. As a result, the laminated polyester film is less prone to deformation such as shrinkage during subsequent heat treatment processes, and excellent release properties can be obtained, especially for mating components that require high-temperature processing. Furthermore, stretching after application also has the advantage of making it easier to create a more uniformly thin resin layer.

[0067] The present invention provides a method for manufacturing a release film, which includes a heat treatment step in which the stretched polyester resin substrate sheet is heated to 150°C or higher to form a resin layer. There are preferred temperature conditions for the heat treatment applied to the coating layer, from the viewpoint of sufficiently promoting the crosslinking reaction of the resin layer and suppressing the penetration of water-based coating agents. Specifically, the heat treatment temperature is 170°C or higher, preferably 200°C or higher, and more preferably 220°C or higher. The upper limit of the heat treatment temperature is preferably 260°C due to the heat resistance of the polyester resin substrate sheet, and even more preferably 250°C due to the heat resistance of the resin composition for forming the resin layer. A heat treatment temperature of 260°C or lower suppresses deformation of the polyester film and reduces thermal decomposition of the resin composition, making it easier to obtain a release film with a more uniform resin layer.

[0068] In particular, a preferred method for manufacturing the laminated polyester film of the present invention is to apply a resin composition for forming a resin layer to a film (B film) that has been uniaxially stretched in the longitudinal direction, dry the solvent, and then stretch and heat it in the width direction. This method is preferable to a method in which an unstretched film (A film) is biaxially stretched after applying a resin composition for forming a resin layer, because the layer formed by the resin composition for forming the resin layer goes through one less stretching step. As a result, defects and cracks in the resin layer due to stretching are less likely to occur, and a resin layer with excellent transparency and smoothness can be formed.

[0069] On the other hand, a case in which an offline coating method is used instead of the manufacturing method of the laminated polyester film of the present invention will be described. The offline coating method is a method in which a resin composition for forming a resin layer is applied to the film after the above-mentioned A film has been stretched uniaxially or biaxially and heat-treated to complete the crystal orientation of the polyester film, or to the A film itself, in a process separate from the film manufacturing process. In other words, it is a coating method in which stretching is not performed after application. In the manufacturing of the laminated polyester film of the present invention, it is preferable to use the in-line coating method for the various advantages described above, but even when forming the resin layer by the offline coating method, the processing temperature is 170°C or higher, and preferably 200°C or higher. By setting the processing temperature to 170°C or higher, the thin resin layer hardens sufficiently, resulting in good adhesion between the resin layer and the polyester resin substrate layer, as well as improved release properties before and after heating. The upper limit of the processing temperature is preferably 260°C due to the heat resistance of the polyester resin substrate sheet. By setting the processing temperature to 260°C or lower, deformation of the polyester resin substrate sheet is suppressed, making it easier to obtain a more uniform laminated polyester film.

[0070] Here, for both in-line and offline coating methods, any known coating method can be used to apply the resin composition for forming a resin layer on the polyester resin substrate sheet, such as bar coating, reverse coating, gravure coating, die coating, or blade coating.

[0071] Next, the method for manufacturing the laminated polyester film of the present invention will be explained in more detail using the in-line coating method with polyethylene terephthalate (PET) film as the polyester film as an example, but the method for manufacturing the laminated polyester film of the present invention is not limited to this.

[0072] First, PET pellets are thoroughly vacuum-dried, then fed into an extruder, melt-extruded into a sheet at 260°C to 280°C, and cooled and solidified to produce an unstretched (unoriented) PET film (Film A). This film is stretched 2.5 to 5.0 times in the longitudinal direction on a roll heated to 80 to 120°C to obtain a uniaxially oriented PET film (Film B). The aforementioned resin composition for forming the resin layer, prepared to a predetermined concentration, is applied to one side of Film B.

[0073] At this time, a surface treatment such as corona discharge treatment may be performed on the coated surface of film B before applying the resin composition for resin layer formation. By performing a surface treatment such as corona discharge treatment, the wettability of the resin composition for resin layer formation to film B is improved, thereby reducing repulsion and enabling the formation of a resin layer with a more uniform coating thickness on the surface of film B. After application, both ends in the width direction of film B are gripped with clips and guided to a heat treatment zone (preheating zone) at 80 to 130°C to dry the solvent of the resin composition for resin layer formation. After drying, film B is stretched 1.1 to 5.0 times in the width direction and then guided to a heat treatment zone (heat setting zone) at 150 to 260°C, preferably 170 to 260°C, for 1 to 30 seconds to complete crystal orientation.

[0074] In this heat treatment process (thermal setting process), a relaxation treatment of 3-15% in the width direction or longitudinal direction may be applied as needed. The resulting laminated polyester film is a laminated polyester film with excellent applicability, adhesion, and transparency for water-based coatings.

[0075] In addition, the laminated polyester film of the present invention may have an intermediate layer between the resin layer and the polyester resin substrate layer. However, if an intermediate layer is provided, the film may be scratched during winding of the film with the intermediate layer laminated, or during subsequent processes up to the application of the resin layer of the present invention. For this reason, in the present invention, it is preferable that the resin layer and the resin substrate layer are directly laminated.

[0076] There are no limitations on the composition of the polyester resin substrate layers that constitute the laminated polyester film of the present invention. For example, a single-layer configuration consisting only of layer A, a laminated configuration of layer A / layer B (i.e., a two-layer laminated configuration of two types), a laminated configuration of layer A / layer B / layer A (i.e., a three-layer laminated configuration of two types), or a laminated configuration of layer A / layer B / layer C (i.e., a three-layer laminated configuration of three types). In this context, layers A, B, and C all mainly consist of polyester resin, but their compositions are different from each other.

[0077] The method for forming the laminated resin substrate layers constituting the laminated polyester film of the present invention is not particularly limited. Examples include lamination by co-extrusion, lamination by bonding, and combinations thereof. However, from the viewpoint of transparency and manufacturing stability, co-extrusion is preferred. When forming a laminated structure, different resin compositions may be used for the purpose of imparting different functions to each layer. For example, in the case of a laminated structure of layer A / layer B / layer A, i.e., a two-type three-layer laminated structure, from the viewpoint of transparency, layer B may be made of homopolyethylene terephthalate, and particles may be added to layer A to impart slipperiness.

[0078] The laminate of the present invention preferably has an adhesive layer on the resin layer side of the laminated polyester film. Various tackifiers can be used as the adhesive layer. For example, acrylic resins, terpene resins, phenolic resins, terpene-phenolic resins, silicone resins, coumarone resins, rosin compounds (rosin or rosin esters, hydrogenated rosin esters), petroleum resins, xylene resins, or styrene resins can be used. There are no particular limitations, but acrylic adhesives are preferably used from an economic standpoint.

[0079] The method for applying the adhesive layer onto the polyester film is not particularly limited, but from an economic standpoint, a wet coating method is preferred. Any known coating method can be used for the wet coating method, such as the bar coating method, reverse coating method, gravure coating method, die coating method, or blade coating method. [Examples]

[0080] The laminated polyester film of the present invention will be described in detail below based on specific examples, but the present invention is not limited to these examples.

[0081] <Methods for measuring characteristics and evaluating effects> The method for measuring the properties and evaluating the effects in this invention is as follows.

[0082] (1) Method for analyzing the composition of the resin layer surface The surface composition of the resin layer of a laminated polyester film was analyzed using GCIB-TOF-SIMS (GCIB: gas cluster ion beam, TOF-SIMS: time-of-flight secondary ion mass spectrometry). The measurement conditions were as follows. <Sputtering conditions> Ion source: Argon gas cluster ion beam <Detection conditions> Primary ion: Bi3 ++ (25keV) Secondary ion polarity: positive Mass range: m / z 0~1000 Measurement range: 400 × 400 μm 2 K is defined as the peak intensity of the positive ion fragment detected at maximum intensity during measurement, and (SiCH3) is defined as the positive ion fragment derived from polydimethylsiloxane. + The peak intensity of the fragment ion (M / Z=43) was denoted as P, and its ratio P / K was calculated. If P / K < 0.01, it was determined that the resin layer substantially did not contain any silicone compounds.

[0083] (2) Method for measuring the melting point of resin layer components A solid sample of the resin composition for forming the resin layer, prepared in the examples described below, was placed in an aluminum cup at 10 g and dried in a hot air oven at 80°C for 24 hours. 3 mg of the prepared solid sample was measured using a differential scanning calorimeter (DSCvesta, manufactured by Rigaku Corporation). The temperature was increased from -100°C to 100°C at a rate of 10°C / min in a nitrogen atmosphere, and the peak temperature of the curve obtained during this heating was measured. The average of three such measurements was taken as the melting point of the resin layer component. While the baseline of the DSC chart may shift due to glass transition, in this invention, only the temperature of the peak in the DSC chart was used as the melting point. If no peak was measured in the DSC chart, it was determined that the resin layer component did not contain any components with a melting point.

[0084] (3) Tape peel strength at 23℃ The tape peel strength at 23°C was measured as follows. First, an acrylic polyester single-sided adhesive tape (Nitto Denko Corporation, No. 31B tape, 19 mm wide) was bonded onto the resin layer of a laminated polyester film, and a 2 kgf roller was passed over it once to create a tape-bonded laminated polyester film. The tape-bonded laminated polyester film was then left to stand for 24 hours in an environment of 23°C and 65% RH. The side of the laminated polyester film opposite to the side to which the single-sided adhesive tape was bonded was fixed to the moving stage of a peel analysis device "VPA-2" manufactured by Kyowa Interface Science Co., Ltd. using an acrylic polyester double-sided adhesive tape (Nitto Denko Corporation, No. 532 tape, 0.08 mm thick). One end of the single-sided adhesive tape was gripped by the load cell of the peel analysis device, and the peel strength (N / 19 mm) was measured at a peel angle of 180° and a tensile speed of 300 mm / min. From the graph of peel force (N / 19mm) - travel distance (mm) obtained from the measurements, the average peel force between 10 and 40mm was calculated. This measurement was performed five times, and the average of the three measurements, excluding the maximum and minimum values, was used as the 23°C tape peel force of the laminated polyester film.

[0085] (4) Tape peel strength after heating at 100°C for 1 hour The tape peel strength after heating at 100°C for 1 hour was measured as follows. First, a tape-laminated laminated polyester film was prepared as described in "(3) Tape Peel Strength at 23°C". Then, the tape-laminated laminated polyester film was left to stand for 24 hours in an environment of 23°C and 65%RH. After standing for 24 hours, it was heated in a hot air oven at 100°C for 1 hour, and the peel strength was measured using the peel analysis device "VPA-2" manufactured by Kyowa Interface Science Co., Ltd. in the same manner as in "(3) Tape Peel Strength at 23°C". This measurement was performed 5 times, and the average of the 3 measurements, excluding the maximum and minimum values, was taken as the tape peel strength of the laminated polyester film after heating at 100°C for 1 hour.

[0086] (5) Load 0.5 N / cm 2 Static friction force between resin layers in First, a laminated polyester film that has been left standing for 24 hours at 23°C and 65%RH is cut to a width of 1 cm. The resin-layer side of the cut laminated polyester film is placed on the resin-layer side of another laminated polyester film that has also been left standing for 24 hours at 23°C and 65%RH, so that the two laminated polyester films are in contact by 1 cm x 1 cm, and the two are mounted on a friction coefficient measuring instrument manufactured by Techno-Needs Co., Ltd. in accordance with ASTM standard D1894-63. A 2 kgf roller is passed back and forth once over the two mounted laminated polyester films to remove the air between them. A load of 0.5 N / cm is applied to the two laminated polyester films. 2 A weight was placed so as to be positioned, and the lower of the two laminated polyester films was pulled horizontally at a moving speed of 120 mm / min and a moving distance of 10 mm. The horizontal stress on the upper film was measured during this process. The maximum stress was read from the stress (N)-movement distance (mm) graph obtained from the measurement. This measurement was performed five times, and the average of the three measurements (excluding the maximum and minimum values) was multiplied by 9 to obtain a value of 0.5 N / cm². 2 Static friction force between resin layers in (N / 9cm) 2 )

[0087] (6) Evaluation of initial adhesive layer peel strength As an adhesive, a silicone-based adhesive (Shin-Etsu Chemical Co., Ltd., KR-3700) was diluted with toluene to a solid content of 50%, and 2.0 parts by mass of a hardening agent (Shin-Etsu Chemical Co., Ltd., CAT-PL-50T) was mixed with 100 parts by mass of the solid content of the adhesive. This coating was applied to Toray Industries, Inc.'s PET film "Lumirror" (registered trademark) U40 (base material thickness 50 μm, width 50 mm) using an applicator to a final thickness of 40 μm. Subsequently, it was dried in a hot air oven at 80°C for 1 minute to form an adhesive laminate sheet. The laminated polyester film of the present invention was laminated onto the adhesive layer of the adhesive laminate sheet as a release film, and a 2 kgf roller was passed over it once to prepare a test piece. The peel force was measured using the same procedure as in "(3) 23°C Tape Peel Force," except that the adhesive laminate sheet was gripped in the load cell of the peel analysis device. The results obtained were evaluated according to the following criteria. ◎ indicates particularly good, ○ indicates good, and △ indicates a level that is practically acceptable. ◎: Initial adhesive layer peeling force less than 2.0N / 50mm ○: Initial adhesive layer peeling force 2.0N / 50mm or more, less than 3.0N / 50mm △: Initial adhesive layer peeling force 3.0N / 50mm or more, less than 6.0N / 50mm ×: Initial adhesive layer peeling force of 6.0 N / 50 mm or more.

[0088] (7) Evaluation of adhesive layer peel strength after heating The test specimens described in section (6) "Initial adhesive layer peeling force" were further subjected to heat treatment in a hot air oven at 150°C for 30 minutes, and the peeling force was measured in the same manner as in section (6) "Evaluation of initial adhesive layer peeling force".

[0089] (8) Evaluation of adhesive layer peelability after heating From the peeling forces calculated in sections (6) Initial adhesive layer peeling force and (7) Adhesive layer peeling force after heating, the difference in adhesive layer peeling force before and after heating (Δ peeling force) was calculated using the following formula and evaluated according to the following criteria. ◎ indicates particularly good, ○ indicates good, and △ indicates a level that is acceptable for practical use. [ΔPeeling force] = Peeling force of the adhesive layer after heating / Peeling force of the initial adhesive layer ◎: Δ Peeling force less than 1.5 ○: Δ peeling force 1.5 or more and less than 2.0 △: Δ peeling force 2.0 or more and less than 2.5 ×: Δ peeling force of 2.5 or higher.

[0090] (9) Thickness of the resin layer The laminated polyester film is stained with RuO4 and / or OsO4. Next, the laminated polyester film is frozen and cut in the film thickness direction to obtain 10 ultrathin section samples for observation of the resin layer cross-section. Each sample cross-section is observed at 10,000 to 1,000,000x magnification using a TEM (transmission electron microscope: Hitachi H7100FA), and cross-sectional images are obtained. The measured resin layer thickness of these 10 samples is averaged to determine the resin layer thickness of the laminated polyester film.

[0091] [Ingredients used in the examples and comparative examples] The following components were used in the examples and comparative examples.

[0092] <Release agent (A)> • Release agent (A-1): Long-chain alkyl group-containing resin (1) In a four-necked flask equipped with a stirrer, thermometer, condenser, and dropping funnel, 10 parts by mass of 2-methacryloyloxyethyl isocyanate, 50 parts by mass of tetrahydrofuran, and 0.1 parts by mass of methoquinone were added and heated to 40°C with stirring. After replacing the air in the flask with nitrogen gas, 5 parts by mass of n-butylamine were added over 1 hour using the dropping funnel. The reaction was then continued at 40°C for 2 hours, after which the tetrahydrofuran was removed by distillation under reduced pressure at 60°C to obtain monomer α.

[0093] 2000 parts by mass of pure water, 20 parts by mass of sodium dodecylbenzenesulfonate as an emulsifier, and 2 parts by mass of potassium persulfate as a polymerization initiator were added to a four-necked flask and heated to 70°C with stirring. After replacing the air in the flask with nitrogen gas, 60 parts by mass of monomer α and 140 parts by mass of stearyl methacrylate were added in small amounts over approximately 2 hours using a dropping funnel. The temperature was then raised to 80°C and polymerization was continued for 5 hours, after which it was cooled to room temperature to terminate polymerization. The polymer was salted out, filtered, washed with water, and then dried and ground to obtain a long-chain alkyl group-containing resin (a vinyl copolymer having an alkyl group with 18 carbon atoms (long-chain alkyl group-containing resin (1))). This was diluted with water to a concentration of 20% by mass.

[0094] • Release agent (A-2): Long-chain alkyl group-containing resin (2) Release agent (A-2) was obtained in the same manner as release agent (A-1), except that the amounts of monomer α and stearyl methacrylate used were changed to 160 parts by mass and 40 parts by mass, respectively.

[0095] • Release agent (A-3): Long-chain alkyl group-containing resin (3) Release agent (A-3) was obtained in the same manner as release agent (A-1), except that the amounts of monomer α and stearyl methacrylate used were changed to 40 parts by mass and 160 parts by mass, respectively.

[0096] • Release agent (A-4): Long-chain alkyl group-containing resin (4) Release agent (A-4) was obtained in the same manner as release agent (A-1), except that the amounts of monomer α and stearyl methacrylate used were changed to 10 parts by mass and 190 parts by mass, respectively.

[0097] • Release agent (A-5): Long-chain alkyl group-containing resin (5) "P-ROIL" (registered trademark) 406 (copolymer having a long-chain alkyl group), manufactured by Lion Specialty Chemicals Co., Ltd. • Release agent (A-6): Silicone-containing resin "Cymac" (registered trademark) US-480, manufactured by Toagosei Co., Ltd. (silicone graft copolymer with an acrylic backbone, containing hydroxyl and carboxyl groups).

[0098] <Binder resin (B)> • Binder resin (B-1): Acrylic resin We used "Nicazol" (registered trademark) RX7013, manufactured by Nippon Carbide Industries, Ltd. • Binder resin (B-2): Polyester resin We used "Pluscoat" (registered trademark) Z-730, manufactured by Go-O Chemical Industry Co., Ltd. • Binder resin (B-3): Urethane resin We used DIC Corporation's "Hydran" (registered trademark) AP-40.

[0099] <Reactive compound (C)> • Reactive compound (C-1): Melamine compound (methylolated melamine) We used "Nikalac" (registered trademark) MW-035, manufactured by Sanwa Chemical Co., Ltd.

[0100] • Reactive compound (C-2): Oxazoline compound We used "Epocross" (registered trademark) WS-500, manufactured by Nippon Shokubai Co., Ltd.

[0101] • Reactive compounds (C-3): Carbodiimide compounds A carbodiimide aqueous crosslinking agent (Nisshinbo Chemical Co., Ltd. "Carbodilite" (registered trademark) V-04) was used.

[0102] (Example 1) • Resin compositions for forming resin layers: A release agent (A-1) and a reactive compound (C-1) were mixed in a solid content mass ratio of (A-1) / (C-1) = 10 / 90. Then, water was added to adjust the solid content concentration according to the coating method and target thickness described later, and a resin composition was obtained. Furthermore, in order to improve the coatability on polyester film, an acetylene-based surfactant ("Orphine" (registered trademark) E1010, manufactured by Nisshin Chemical Industry Co., Ltd.) was added in an amount of 0.1 parts by mass per 100 parts by mass of the entire mixed resin composition.

[0103] • Polyester film: PET pellets containing two types of particles (4% by mass of silica particles with a primary particle size of 0.3 μm and 2% by mass of calcium carbonate particles with a primary particle size of 0.8 μm) (intrinsic viscosity 0.64 dl / g) were thoroughly vacuum dried, then supplied to an extruder and melted at 280°C. The pellets were extruded into a sheet through a T-shaped die and then cooled and solidified using an electrostatic casting method on a mirror-finish casting drum with a surface temperature of 25°C to obtain an unstretched film (film A). This unstretched film was heated to 90°C and stretched 3.1 times in the longitudinal direction to obtain a uniaxially oriented film (film B).

[0104] • Laminated polyester film After subjecting a uniaxially oriented film to corona discharge treatment in air, the resin composition prepared by the method described in the section on resin compositions for resin layer formation was applied to a coating thickness of approximately 6 μm using a wire bar coat. Subsequently, both ends of the uniaxially oriented film coated with the resin composition were gripped with clips in the width direction and guided to a tenter, where the solvent of the resin composition was dried in a preheating zone at an ambient temperature of 90-100°C. Subsequently, the film was continuously stretched 3.6 times in the width direction in a stretching zone at 100°C, followed by heat treatment for 20 seconds in a heat treatment zone at 230°C to form a resin layer, and then a 5% relaxation treatment in the width direction was performed at the same temperature to complete the crystal orientation of the polyester film. After that, the film was cut parallel to the longitudinal direction with a slitter to cut and remove both ends in the width direction (uncoated portions) that were gripped by the clips, and the laminated polyester film was wound into a roll. The properties of the obtained laminated polyester film are shown in Tables 2 and 3.

[0105] (Examples 2-18, 22, Comparative Examples 1, 2, 3) A laminated polyester film was obtained in the same manner as in Example 1, except that the composition of the resin composition was changed as shown in Table 1. The properties of the obtained laminated polyester film are shown in Tables 2 and 3.

[0106] (Examples 19, 20) Laminated polyester films were obtained in the same manner as in Example 2, except that PET pellets containing recycled materials in the proportions shown in Table 2 (Example 19) and biomass materials (Example 20) were used as raw materials for the polyester film. The properties of the obtained laminated polyester films are shown in Tables 2 and 3. The recycled materials referred to here are the uncoated portions removed during the film-forming process of the polyester films in Examples 1 to 18, which were shredded and used in the film-forming process of the polyester films after being kneaded with virgin materials. On the other hand, the biomass material used was PET with a biomass content of 15% and in which some of the ethylene glycol units are plant-derived.

[0107] (Examples 21, 23) A laminated polyester film was obtained using the resin composition of Example 10 by the following method. Toray Industries, Inc.'s PET film "Lumirror" (registered trademark) T60 (substrate thickness 50 μm) was used as the polyester resin substrate. The resin composition was applied to the polyester resin substrate using a wire bar. Next, to prevent deformation due to heat, a SUS plate film of the same shape as the film was placed on top, and after gripping all four sides without gaps with double clips, drying and curing were carried out in a hot air oven at 200°C for 2 minutes to obtain a laminated polyester film. The properties of the obtained laminated polyester film are shown in Tables 2 and 3.

[0108] (Comparative Example 4) A laminated polyester film was obtained in the same manner as in Example 21, except that the composition of the resin composition and the drying temperature in the hot air oven were as shown in Table 1. The properties of the obtained laminated polyester film are shown in Tables 2 and 3.

[0109] In Example 21 and Comparative Example 4, the heat treatment temperature refers to the drying temperature in the hot air oven.

[0110] [Table 1]

[0111] [Table 2]

[0112] [Table 3] [Industrial applicability]

[0113] The laminated polyester film of the present invention has release properties from adhesives such as acrylic resins and adhesives, and stable release properties even after heating, making it suitable for use as a release film for surface protection films, particularly for preventing surface scratches during processing, assembly, inspection, and transportation of optical and electronic components.

Claims

1. The polyester resin base layer has a resin layer on at least one side, the 23°C tape peel strength of the resin layer is 2.0 N / 19 mm or less, and the load is 0.5 N / cm. ２ The static friction force between the resin layers in the above case is 10 N / 9 cm. ２ The above is a laminated polyester film.

2. The laminated polyester film according to claim 1, wherein when the tape peeling force of the resin layer at 23°C is R1 and the tape peeling force of the resin layer after heating at 100°C for 1 hour is R2, the ratio of R1 to R2, R2 / R1, is 2.0 or less.

3. The laminated polyester film according to claim 1 or 2, wherein, when the surface of the resin layer is analyzed by time-of-flight secondary ion mass spectrometry, the ratio (P / K) of the peak intensity (P) of the positive ion fragment derived from dimethylsiloxane to the peak intensity (K) of the positive ion fragment detected at maximum intensity is less than 0.

01.

4. The laminated polyester film according to claim 1 or 2, wherein the resin layer contains a component having a melting point of -50°C or higher and 30°C or lower.

5. The laminated polyester film according to claim 1 or 2, wherein the resin layer is formed from a resin composition containing a release agent and at least one compound selected from oxazoline compounds, melamine compounds, and carbodiimide compounds.

6. A laminated polyester film according to claim 1 or 2, comprising at least one of biomass raw materials and recycled raw materials.

7. A laminate having an adhesive layer on the resin layer side of the laminated polyester film according to claim 1 or 2.

8. A method for manufacturing a laminated polyester film according to claim 1 or 2, comprising, in this order: a coating step of applying the resin composition for forming the resin layer to at least one side of a polyester film; a stretching step of stretching the polyester film after the resin composition has been applied in at least one axial direction; and a heat treatment step of heating the stretched polyester film to 150°C or higher to form a resin layer.

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