JP7574533B2 - Laminated film and its manufacturing method - Google Patents

Description

The present invention relates to a laminated film having a polyester film and a resin layer, and a method for producing the same.

Polyester films have excellent mechanical properties, electrical properties, dimensional stability, transparency, chemical resistance, etc., and are therefore widely used as substrate films in many applications, such as magnetic recording materials and packaging materials. In particular, in recent years, there has been an increasing demand for films with excellent release properties, such as protective films for adhesive layers in adhesive products and carrier films in the processing of various industrial products. As films with excellent release properties, films containing silicone compounds in the resin layer are most commonly used in terms of industrial productivity and heat resistance (see, for example, Patent Document 1). However, when a silicone compound is contained in the resin layer, the surface free energy of the resin layer is reduced, which may result in poor coatability on the adherend.

In addition, when a polyester film having a resin layer is used as a process film for manufacturing a printed wiring board, it is used as a polyester film with an insulating layer, in which an insulating layer is formed on the resin layer of a polyester film having a resin layer. A laminate for a printed wiring board is obtained by laminating (stacking) the polyester film with an insulating layer on a core layer and peeling off the polyester film. When preparing a polyester film with an insulating layer, the insulating layer is generally formed by applying a coating composition containing an insulating resin on the resin layer of the polyester film, and then evaporating the solvent by heating at a relatively low temperature of about 80 to 120 ° C. If the resin layer contains a silicone compound, repelling or pinholes may occur when the coating composition containing an insulating resin is applied on the resin layer of the polyester film, which may be a defect as an insulating layer. In addition, when a polyester film with an insulating layer is laminated on a core layer to prepare a laminate, after lamination on the core layer, a process of curing the insulating layer at a relatively high temperature of about 140 to 180 ° C. with the polyester film still attached, and then peeling off the polyester film may be performed. At this time, at the stage of laminating the polyester film with an insulating layer to the core layer, the insulating layer needs to be in close contact with the polyester film, but after the insulating layer is thermally cured at high temperature, the insulating layer and the polyester film need to be easily peeled off. In other words, it is necessary to control the peeling force between the resin layer and the insulating layer by heating. At this time, if the resin layer contains a silicone compound, it is relatively easy to control the peeling force by heating, but on the other hand, if the resin layer contains a silicone compound, there is a problem that the silicone component of the resin layer is easily transferred to the insulating layer when the polyester film is peeled off.

In response to these issues, studies have been conducted on the use of long-chain alkyl group-containing resins, olefin resins, fluorine compounds, and wax-based compounds, particularly long-chain alkyl group-containing resins, as release agents that do not contain silicone compounds (hereinafter referred to as non-silicone release agents) (see, for example, Patent Documents 2 to 5).

JP 2010-155459 A JP 2004-351626 A JP 2014-151481 A JP 2004-230772 A JP 2015-199329 A

However, compared to a resin layer containing a release agent containing a silicone compound, a resin layer containing a non-silicone release agent has a tendency that a layer provided on the resin layer by coating or the like tends to peel off heavily (become difficult to peel off), and there is also a problem that the peeling force of a layer provided on the resin layer by coating or the like increases significantly when heated. For example, when the present inventors verified the film described in Patent Document 2, it was found that when an adhesive tape was attached to the resin layer and peeled off after heating, the adhesive tape peeled off significantly heavily. In addition, when a long-chain alkyl group-containing resin and a crosslinking agent are used in combination as in the films described in Patent Documents 3 and 4, or when a long-chain alkyl acrylate resin and a melamine resin are used in combination as in Patent Document 5, the peeling force of the adhesive tape hardly changes due to heating, but the peeling force is still high and peeling is difficult even after heating.

The present invention aims to eliminate the above-mentioned drawbacks and provide a laminated film that has excellent coatability of a coating composition that forms a layer that is applied onto a resin layer, and excellent control of the peel force caused by heating of the layer that is applied onto the resin layer.

As a result of intensive research in consideration of the above problems, the inventors of the present invention discovered that by using a laminate film having specific physical properties, it is possible to obtain a laminate film that is excellent in the coatability of a coating composition that forms a layer that is applied to a resin layer, and in the peelability of a layer that is applied to a resin layer, and thus completed the present invention.

The present invention comprises the following configuration.
[I] A laminate film having a polyester film and a resin layer, the resin layer being present on at least one surface layer, the resin layer having a water contact angle of 95° or more and 110° or less, an initial tape peel strength of the laminate film being 0.5 N/50 mm or more and 4.0 N/50 mm or less, and a tape peel strength after heating at 100°C for 30 minutes being 8.0 N/50 mm or more and 14.0 N/50 mm or less.
[II] The laminate film according to [I], in which, 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 a fragment derived from polydimethylsiloxane to the peak intensity (K) of the fragment detected at the maximum intensity is less than 0.01.
[III] The laminate film according to [I] or [II], wherein the elastic modulus P (MPa) measured from the surface side of the resin layer of the laminate film at a penetration depth of 10 nm using an atomic force microscope (AFM) is 200≦P≦2000.
[IV] A laminate film according to any one of [I] to [III], wherein the static friction coefficient μs of the resin layer is 0.10 or more and 0.30 or less.
[V] The laminate film according to any one of [I] to [IV], wherein the resin layer is formed from a coating composition containing a release agent (A) and at least one resin or compound (B) selected from an epoxy resin, a melamine resin, an oxazoline compound, a carbodiimide compound, a polyester resin, an acrylic resin, and a urethane resin.
[VI] The laminate film according to [V], wherein the release agent (A) contains a resin having an alkyl group having 12 or more carbon atoms.
[VII] The laminate film according to [VI], wherein the resin having an alkyl group having 12 or more carbon atoms is a resin having a side chain of an alkyl group having 12 or more carbon atoms on a polymethylene main chain.
[VIII] The laminate film according to any one of [VI] to [VII], wherein the mass ratio of the release agent (A) to the resin or compound (B) in the coating composition is in the range of release agent (A)/resin or compound (B)=10/90 to 70/30.
[IX] The laminate film according to any one of [I] to [VIII], wherein the resin layer has a thickness of 50 nm or more and less than 200 nm.
[X] The laminate film according to any one of [I] to [IX], wherein the surface free energy of the resin layer is 20 mN/m or more and 30 mN/m or less.
[XI] The laminate film according to any one of [I] to [X], which is used in applications in which a layer containing an epoxy resin is provided on the surface of the resin layer, and then the layer containing an epoxy resin is peeled off.
[XII] A method for producing a laminated film according to any one of [I] to [XII], comprising the steps of applying a coating composition containing a release agent (A) to at least one side of a polyester film before completion of crystal orientation, stretching the polyester film in at least one axial direction, and then subjecting the polyester film to a heat treatment to complete the crystal orientation of the polyester film.
It is.

According to the present invention, it is possible to provide a laminate film having excellent peeling properties depending on heating temperature, in that the coating composition forming the layer provided on the resin layer by coating has good coatability and transportability, and the layer provided on the resin layer by coating has high peelability after low-temperature heating and low peelability after high-temperature heating. Furthermore, it is possible to provide a laminate film having excellent coatability and peelability, in that the layer provided on the resin layer does not lift up during transportation.

The laminated film of the present invention is a laminated film having a polyester film and a resin layer, the resin layer being present on at least one surface layer, the water contact angle of the resin layer being 95° or more and 110° or less, the initial tape peeling strength of the laminated film being 0.5 N/50 mm or more and 4.0 N/50 mm or less, and the tape peeling strength after heating at 100°C for 30 minutes being 8.0 N/50 mm or more and 14.0 N/50 mm or less. First, the meaning of these physical properties and examples of control methods will be explained.

In the present invention, the water contact angle is determined by the sessile drop method described in JIS R3257:1999. When a water drop is placed on the surface of the resin layer and equilibrium is reached in that atmosphere, the water contact angle can be determined by the following formula, and generally serves as an index for judging the wettability of the solid surface. In other words, the smaller the water contact angle, the better the wettability of the solid surface, and the larger the value, the worse the wettability.

γS = γLcosθ + γSL
(In the above formula, γS is the surface tension of a solid, γL is the surface tension of a liquid, γSL is the interfacial tension between a solid and liquid, and θ is the contact angle).

The above formula is called "Young's law" and defines the angle between the liquid surface and the solid surface as the "contact angle." Water contact angles can be measured using a wide variety of commercially available devices, but in this invention, the values are those measured using a contact angle meter, DropMaster DM-501, manufactured by Kyowa Interface Science Co., Ltd. The specific numerical range of water contact angles and the measurement method will be described later.

In the present invention, the initial tape peeling force is defined as follows. First, an acrylic polyester adhesive tape (Nitto 31B tape, 19 mm width, manufactured by Nitto Denko Corporation) is applied to the resin layer of the laminated film of the present invention, and a roller of 2 kgf is moved back and forth once from above. The laminated film to which the tape is applied is then left to stand for 24 hours in an environment of 25°C and 65% RH, and the peel load measured when the tape is peeled at a peel angle of 180° and a tensile speed of 300 mm/min using a universal testing machine "Autograph AG-1S" manufactured by Shimadzu Corporation is taken as the initial tape peeling force. A specific method for measuring the initial tape peeling force will be described later.

In the present invention, the tape peeling force after heating at 100°C for 30 minutes is defined as follows. First, an acrylic polyester adhesive tape (Nitto 31B tape, 19 mm width, manufactured by Nitto Denko Corporation) is attached to the resin layer of the laminated film of the present invention, and a roller of 2 kgf is moved back and forth once from above. After that, the laminated film to which the tape is attached is heated in a hot air oven at 100°C for 30 minutes, and then peeled at a peel angle of 180° and a tensile speed of 300 mm/min using a universal testing machine "Autograph AG-1S" manufactured by Shimadzu Corporation. The peeling load when peeled is defined as the tape peeling force after heating at 100°C for 30 minutes. A specific method for measuring the tape peeling force after heating at 100°C for 30 minutes will be described later.

As a result of intensive research, the present inventors have found that the peel strength of a layer provided by coating or the like on the resin layer of the laminate film of the present invention (hereinafter, the layer provided by coating or the like on the resin layer of the laminate film of the present invention may be referred to as the "surface layer") after low-temperature heating (the peel strength between the resin layer of the laminate film of the present invention and the surface layer after low-temperature heating) correlates with the initial tape peel strength (the peel strength between the resin layer of the laminate film of the present invention and the acrylic polyester adhesive tape). However, the magnitude of the peel strength is reversed. The reason for this is believed to be as follows.

First, the peeling force after low-temperature heating of the resin layer and the surface layer, and the initial tape peeling force depend on the strength of the interaction between the resin layer and the surface layer of the laminated film of the present invention, and between the resin layer and the acrylic polyester adhesive tape. In other words, if the interaction is strong, the peeling force will be strong (heavy peeling (difficult to peel)), and if the interaction is weak, the peeling force will be weak (light peeling (easy to peel)). The interaction here is a value determined by the intermolecular forces due to hydrogen bonds and hydrophobic interactions, the surface free energies of each layer and the difference therebetween, and further, when detected as a peeling force, it is affected by the thickness and elastic modulus of the layer depending on the peeling direction. It is thought that the dominant factor in the change in peeling force before and after heating is the change in intermolecular forces due to the change in the molecular structure of the resin layer.

The components that form the layer by the crosslinking reaction that proceeds when heated at low temperatures of about 80 to 120°C are hydrophilic, as typified by epoxy resins. On the other hand, the acrylic polyester adhesive tape used to measure the initial tape peeling force and the tape peeling force after heating described above is hydrophobic. Therefore, when using the acrylic polyester adhesive tape to design the peeling force between the resin layer and the surface layer having hydrophilic properties, the following relationship is obtained. That is, a resin layer that has a small interaction with the hydrophilic surface layer has a large peeling force with the hydrophobic acrylic polyester adhesive tape, and conversely, a resin layer that has a large interaction with the hydrophilic surface layer has a small peeling force with the hydrophobic acrylic polyester adhesive tape. That is, when the initial tape peeling force (peel force with the hydrophobic acrylic polyester adhesive tape) of the resin layer of the laminated film of the present invention is small, the peeling force between the resin layer and the surface layer after low-temperature heating is large, and when the initial tape peeling force of the resin layer of the laminated film of the present invention is large, the peeling force between the resin layer and the surface layer after low-temperature heating is small.

Furthermore, as a result of further intensive research by the present inventors, it was found that the change in the peeling force of the resin layer and surface layer of the laminate film of the present invention after low-temperature heating to the peeling force of the resin layer and surface layer of the laminate film of the present invention after high-temperature heating correlates with the change from the initial tape peeling force to the tape peeling force after heating at 100°C for 30 minutes (the change in the initial tape peeling force of the resin layer of the laminate film of the present invention and the tape peeling force after heating are opposite to the change in the peeling force of the resin layer and surface layer of the laminate film of the present invention after low-temperature heating and after high-temperature heating). When a surface layer is formed on the resin layer of the laminate film by low-temperature heating and then heated at high temperature, it is believed that the coating structure of the resin layer changes as the resin layer itself is simultaneously heated to high temperature. It is believed that the moderate change in the resin layer by high-temperature heating also changes the state of interaction with the surface layer, resulting in a large change in the peeling force after high-temperature heating. In the present invention, "low-temperature heating" refers to heating in the range of 80 to 120°C, and "high-temperature heating" refers to heating in the range of 150 to 180°C.

The laminated film of the present invention has a water contact angle of 95° to 110° for the resin layer, and the initial tape peel strength of the laminated film is controlled to 0.5 N/50 mm to 4.0 N/50 mm, and the tape peel strength after heating at 100°C for 30 minutes is controlled to 8.0 N/50 mm to 14.0 N/50 mm, so that the coating properties of the coating composition that forms the surface layer provided on the surface of the resin layer and the peel properties before and after heating can be compatible.

Methods for controlling the water contact angle, initial tape peeling strength, and tape peeling strength after heating at 100°C for 30 minutes of the resin layer of the laminated film of the present invention include, for example, the components constituting the resin layer, the coating composition, and the manufacturing method described below. The preferred ranges for each will be described below, but the following describes the physical properties that are preferred for achieving the desired function.

The tape peeling force is affected by the interaction between the resin layer and the tape, the thickness of the resin layer, and the elastic modulus of the resin layer. Therefore, by controlling the thickness and elastic modulus of the resin layer and the distribution of the constituent materials, it is possible to control the peeling force and coatability more effectively even when the same materials are used. The elastic modulus distribution can be evaluated, for example, using atomic force microscopy, and the distribution of the constituent materials can be evaluated, for example, using time-of-flight secondary ion mass spectrometry (GCIB-TOF-SIMS).

The specific numerical ranges for the water contact angle, initial tape peeling force, and tape peeling force after heating at 100°C for 30 minutes are described below. The resin layer of the laminated film of the present invention must have a water contact angle of 95° or more and 110° or less. In the laminated film of the present invention, by making the water contact angle of the resin layer 95° or more, it is possible to impart good releasability to the laminated film. If the water contact angle of the resin layer is less than 95°, the releasability will be poor, and for example, when an epoxy resin is applied to the resin layer and cured by low-temperature heating, and then an attempt is made to peel it off, the peeling force of the epoxy resin will become heavy.

In addition, in the laminated film of the present invention, by making the water contact angle of the resin layer 110° or less, the coating composition that forms a surface layer containing a component such as an epoxy resin on the surface of the resin layer can be made to have good applicability, and the surface layer containing a component such as an epoxy resin can be prevented from naturally peeling off from the resin layer. If the water contact angle of the resin layer is greater than 110°, it becomes difficult to apply the coating composition that forms the surface layer containing a component such as an epoxy resin without defects such as repelling or pinholes, and a decrease in quality occurs, such as a part of the surface layer containing a component such as an epoxy resin falling off from the resin layer. More preferably, it is 98° or more and 105° or less.

The laminated film of the present invention must have an initial tape peeling force of 0.5 N/50 mm or more and 4.0 N/50 mm or less, and a tape peeling force after heating at 100°C for 30 minutes of 8.0 N/50 mm or more and 14.0 N/50 mm or less. The initial tape peeling force is more preferably 0.9 N/50 mm or more and 3.5 N/50 mm or less, and even more preferably 1.2 N/50 mm or more and 3.0 N/50 mm or less. The tape peeling force after heating at 100°C for 30 minutes is more preferably 9.0 N/50 mm or more and 13.0 N/50 mm or less, and even more preferably 9.5 N/50 mm or more and 12.0 N/50 mm or less.

An initial tape peeling force of 0.5 N/50 mm or more and 4.0 N/50 mm or less indicates that the interaction between the resin layer and the hydrophobic acrylic polyester adhesive tape is small, that is, the interaction between the resin layer and the surface layer after low-temperature heating is large, so that it is possible to prevent natural peeling of the surface layer during the process of laminating the surface layer. If the initial tape peeling force is less than 0.5 N/50 mm, the interaction between the resin layer and the hydrophobic acrylic polyester adhesive tape is very small, that is, the interaction with the surface layer after low-temperature heating becomes too large, so that there are locally strong adhesion parts during the subsequent peeling after high-temperature heating, and the peeling force becomes unstable, such as vibration occurring during peeling, which is not preferable. Also, if the initial tape peeling force is greater than 4.0 N/50 mm, the interaction with the surface layer after low-temperature heating becomes small, and a decrease in quality occurs, such as part of the surface layer falling off the resin layer during the process of laminating the surface layer.

If the above initial tape peeling force is satisfied and the tape peeling force after heating at 100°C for 30 minutes is 8.0 N/50 mm or more and 14.0 N/50 mm or less, the structural change of the resin layer due to heating is large, and the interaction between the resin layer and the hydrophobic acrylic polyester adhesive tape is large. In other words, conversely, the peeling force between the resin layer and the surface layer after high-temperature heating is small, so that it becomes easy to peel when trying to peel it off. If the above initial tape peeling force is satisfied and the tape peeling force after heating at 100°C for 30 minutes is 8.0 N/50 mm or less, the change in the resin layer due to heating is small, and the peeling force of the surface layer after high-temperature heating remains large, resulting in poor peeling. If the above initial tape peeling force is satisfied and the tape peeling force after heating at 100°C for 30 minutes is 14.0 N/50 mm or more, the peeling force of the surface layer after high-temperature heating is too small, so that the surface layer or a part of the laminate film of the present invention falls off from the resin layer before the surface layer peeling process, resulting in a decrease in quality.

The laminated film of the present invention is preferably used in applications in which a surface layer is provided on the surface of a resin layer, and then the surface layer is peeled off. In this case, if the components of the resin layer are transferred to the surface layer, unnecessary components will adhere to the surface layer, which may have adverse effects such as impairing the properties of the surface layer itself. If the initial tape peeling force and the tape peeling force after heating at 100°C for 30 minutes satisfy the above ranges, the surface layer after high-temperature heating can be easily peeled off, and it is possible to suppress the transfer of resin layer components to the surface layer side when peeling the surface layer.

The laminated film of the present invention is described in detail below.

<Polyester film>
The polyester film serving as the base film in the laminated film of the present invention will be described in detail. Polyester is a general term for polymers in which an ester bond is the main bond in the main chain, and those having 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. as the main component can be preferably used. In the present invention, it is preferable to use polyethylene terephthalate as the polyester film. Furthermore, when heat or shrinkage stress is applied to the polyester film, polyethylene-2,6-naphthalate, which has excellent heat resistance and rigidity, is particularly preferable.

In addition, various additives such as antioxidants, heat stabilizers, weather stabilizers, UV absorbers, organic lubricants, pigments, dyes, organic or inorganic particles, fillers, antistatic agents, nucleating agents, etc. may be added to this polyester to the extent that they do not deteriorate its properties.

The polyester film is preferably biaxially oriented. A biaxially oriented polyester film is generally a film in which an unstretched polyester sheet or film is stretched about 2.5 to 5 times in both the longitudinal direction and the width direction perpendicular to the longitudinal direction, and then heat-treated to complete the crystal orientation, and which shows a biaxially oriented pattern in wide-angle X-ray diffraction. If the polyester film is not biaxially oriented, the thermal stability, particularly the dimensional stability and mechanical strength of the laminated film will be insufficient, and the flatness will be poor, which is not preferable.

The polyester film used in the present invention may be a laminated structure of two or more layers of polyester film itself. The laminated structure may be, for example, a composite film having an inner layer and a surface layer, and the inner layer and the surface layer may be made of chemically different polymers or the same polymer.

The thickness of the polyester film is not particularly limited and is appropriately selected depending on the application and type, but in terms of mechanical strength, handling properties, etc., it is usually preferably 10 to 500 μm, more preferably 23 to 125 μm, and most preferably 38 to 75 μm. The polyester film may be a composite film produced by coextrusion, or may be a film produced by laminating the obtained films together using various methods.

<Resin Layer>
The resin layer in the laminate film of the present invention is a layer present on at least one surface layer of the laminate film, and is preferably present on at least one surface of the polyester film described above. This layer is necessary for easy peeling in the step of peeling the surface layer described below from the laminate film after laminating a surface layer such as an adhesive tape or an epoxy resin on the resin layer of the laminate film of the present invention.

In the resin layer of the laminated film of the present invention, it is preferable that the ratio (P/K) [-] of the peak intensity (P) of the fragment derived from polydimethylsiloxane to the peak intensity (K) of the fragment detected at the maximum intensity in time-of-flight secondary ion mass spectrometry (GCIB-TOF-SIMS) is less than 0.01. The measurement method will be described in detail later, but when the peak intensity ratio is less than 0.01, the resin layer contains few components derived from polydimethylsiloxane, so that when the laminated film of the present invention is used as a process film for manufacturing electronic parts, there is no migration of silicone compounds (particularly polydimethylsiloxane) to the product side, and problems such as poor conductivity, poor insulation, and pinhole defects can be prevented.

The resin layer of the laminated film of the present invention preferably has a thickness of 50 nm or more and less than 400 nm, and particularly preferably 50 nm or more and less than 200 nm. By making the resin layer have a thickness of 50 nm or more and less than 400 nm, it becomes easy to provide a resin layer having uniform coatability and releasability on the polyester film. If the resin layer has a thickness of 400 nm or more, not only will the manufacturing cost increase, but unevenness and streaks will easily occur during the application of the resin layer, and the quality of the laminated film may decrease.

There is no particular limitation on the method for making the initial tape peel strength of the laminated film of the present invention 0.5 N/50 mm or more and 4.0 N/50 mm or less, and the tape peel strength after heating at 100°C for 30 minutes 8.0 N/50 mm or more and 14.0 N/50 mm or less. A typical method is to form the resin layer from a coating composition containing a release agent (A) and at least one resin or compound (B) selected from epoxy resins, melamine resins, oxazoline compounds, carbodiimide compounds, polyester resins, acrylic resins, and urethane resins. Details are described in the section on coating compositions.

In the laminated film of the present invention, the surface free energy of the resin layer is preferably 20 mN/m or more and 30 mN/m or less. By making the surface free energy of the resin layer 20 mN/m or more, the surface layer can be applied onto the resin layer without repelling or pinholes, and spontaneous peeling of the surface layer can be suppressed. In addition, by making the surface free energy of the resin layer 30 mN/m or less, the peeling force of the surface layer can be reduced. More preferably, it is 23 mN/m or more and 28 mN/m or less.

<Elasticity measurement using atomic force microscope (AFM)>
In addition, the resin layer of the present invention has a preferred numerical range for the elastic modulus measured by AFM. Specifically, the elastic modulus P (MPa) measured at a penetration depth of 10 nm is preferably 200 to 2000, and particularly preferably 500 to 1500 MPa. If the elastic modulus measured by AFM is too small, the surface layer may easily penetrate into the resin layer, and the peeling force may become too large. On the other hand, if the elastic modulus measured by AFM is too large, the laminated film becomes hard, and as a result, it tends to be easily peeled off.

Here, the elastic modulus measurement by atomic force microscope is a compression test using a probe of an extremely small part, and since it is the degree of deformation due to the pressing force, the elastic modulus of the surface layer and its spatial distribution can be measured using a cantilever with a known spring constant. Details will be described in the Examples section, but using the atomic force microscope shown below, the probe at the tip of the cantilever is brought into contact with the resin layer, and the force curve can be measured at a pressing depth of 10 nm. At this time, information on the depth direction of the coating film can be obtained depending on the pressing depth, but generally, the material present at a depth of about 5 to 10 times the pressing depth setting value affects the measurement. Therefore, at a pressing depth of 10 nm, the characteristics of the surface layer are dominant over the influence of the base material. In addition, the spatial resolution in the planar direction depends on the scanning range and number of scanning lines of the atomic force microscope, but under practical measurement conditions, the lower limit is approximately 50 nm. Details and measurement methods will be described later.

<Static friction coefficient of resin layer>
In the laminated film of the present invention, there is a preferred range of values for the static friction coefficient of the resin layer. Specifically, the static friction coefficient μs when the surfaces of the resin layers are overlapped is preferably 0.10 to 0.30, more preferably 0.15 to 0.30, and particularly preferably 0.20 to 0.30. If the static friction coefficient μs is small, when the laminated film of the present invention is used in a roll or sheet form, it is likely to slip, which may adversely affect the accuracy of the subsequent processing. On the other hand, if the static friction coefficient μs is small but large, it is likely to wrinkle, especially when the film is wound into a roll, which may impair the quality of the film. The method for measuring the static friction coefficient μs will be described later.

The method for controlling the static friction coefficient μs of the surface of the resin layer of the laminated film of the present invention is not particularly limited, but examples include imparting a protruding shape to the surface of the resin layer. Normally, a smooth surface without protruding shapes has a large static friction coefficient μs, while a non-smooth surface with protruding shapes has a small static friction coefficient μs. This is because in the case of a smooth surface without protruding shapes, the surfaces come into contact with each other over the entire surface, making the contact area large and making it difficult to slip, whereas in the case of a non-smooth surface with protruding shapes, the surfaces come into contact with each other only at the points of the protrusions, making the contact area small and making it easy to slip.

However, as the inventors of the present invention have furthered their studies, it has been found that in the case of a laminated film having a resin layer that is necessary for easy peeling in the step of peeling the surface layer, but has a small amount of components derived from polydimethylsiloxane, which is a preferred embodiment of the present invention, slippage is likely to occur when the contact area is increased, and there are cases where workability is problematic, such as the occurrence of winding slippage during roll formation. The cause of such a phenomenon is unclear, but in a resin layer having the above characteristics, the molecular arrangement state of the material contributes to the expression of "peeling property" and "low surface energy", and since an arrangement shape is efficiently formed on a smooth surface, it is considered that the surface is effective not only for the properties of peeling property and low surface energy, but also for slippage. Furthermore, as a result of intensive studies by the inventors of the present invention, it has been found that designing protrusions of an appropriate frequency and height on the surface of the resin layer of the laminated film of the present invention is important for improving transportability. It is presumed that this is because the molecular arrangement state of the material is partially disturbed during the formation of the protrusions, making the surface uneven and partially inhibiting slippage. In order to control slippage, the average number of protrusions having a protrusion height of 25 nm or more is preferably 0.1 or ^more and 2.0 or ^less /μm2, more preferably 0.2 or ^more and 1.0 or ^less /μm2, and particularly preferably 0.3 or ^more and 0.6 or ^less /μm2.

The method for imparting a protruding shape to the resin layer surface of the laminated film of the present invention is not particularly limited, but may be, for example, a method in which a raw material containing a particulate material is used in the polyester film production process, a method in which a particulate polyester is used, or a method in which the polyester film surface is scraped off by a method such as high-voltage discharge or plasma. From the viewpoint of forming the above-mentioned resin layer uniformly, a method in which a particulate material is added to a coating composition that forms the resin layer is particularly preferred. The preferred coating composition for forming the resin layer will be described later.

<Laminated film>
The laminated film of the present invention preferably has a 180° C. heat shrinkage rate determined by the measurement method described below of 0% or more and 2.0% or less.

When the laminated film of the present invention is used as an interlayer insulating material film, a hydrophilic resin such as an epoxy resin is applied onto the resin layer of the laminated film of the present invention, and then the product is processed by low-temperature heating (approximately 80 to 120°C). On the other hand, when incorporating a surface layer into electronic components, etc., the laminate (interlayer insulating material film) in which the surface layer is laminated onto the resin layer of the laminated film of the present invention is used after being heated at high temperature (approximately 150 to 180°C) in the mounting process.

In this case, if the heat shrinkage rate is within the above range, it is possible to suppress spontaneous peeling due to the difference in heat shrinkage rate between the laminate film of the present invention and the hydrophilic resin such as epoxy resin that constitutes the surface layer, both in the interlayer insulating material film after low-temperature heating and in the state after high-temperature heating. More preferably, it is 0.5% or more and 1.5% or less, and most preferably, 0.7% or more and 1.3% or less. A negative heat shrinkage rate means that the film expands.

The method for making the heat shrinkage rate of the laminated film of the present invention fall within the above range is not particularly limited, but examples include a method of off-annealing the polyester film after biaxial stretching, and a method of performing a relaxation treatment in the width direction and/or length direction during the heat treatment process.

<Surface layer>
The laminated film of the present invention is preferably used for forming a surface layer on a resin layer. Here, the surface layer refers to a layered molded body containing resin, metal, ceramic, etc., formed on the surface of the laminated film having the resin layer. The method for forming the surface layer is not particularly limited, but it can be formed on the surface of the resin layer by, for example, coating, vapor deposition, lamination, etc. When a coating liquid containing a solvent component is used to form the surface layer, or when the surface layer is a cured layer formed by reacting reactive active sites, the surface layer may be described as both an undried state and an uncured state.

The laminated film of the present invention has the characteristic of excellent peeling properties depending on the heating temperature, that is, the layer provided on the resin layer has high peeling property after low-temperature heating and low peeling property after high-temperature heating. Therefore, the laminated film of the present invention is preferably used for applications in which a surface layer is provided on the surface of the resin layer, and then the surface layer is peeled off after heating at 80 to 120 ° C. and further heating at 150 to 180 ° C. In particular, it is preferably used for an interlayer insulating material film formed through a process of applying a coating composition containing an epoxy resin or the like on the resin layer of the laminated film of the present invention. In the manufacturing process of the interlayer insulating material film, an epoxy resin or the like is applied on the resin layer of the laminated film of the present invention, and then the product is processed by low-temperature heating, so that after low-temperature heating, the laminated film of the present invention and the surface layer need to be in a heavy peeling state (difficult to peel). On the other hand, since only the surface layer is incorporated into electronic components, etc., in the mounting process, a laminate (interlayer insulating material film) in which a low-temperature heated surface layer is laminated on the resin layer of the laminate film of the present invention is heated at high temperature, and then only the laminate film of the present invention is peeled off. Therefore, after high-temperature heating, the laminate film of the present invention and the surface layer need to be easily peeled off (in a state where they can be easily peeled off). Therefore, the laminate film of the present invention is preferably used in applications in which a layer (surface layer) containing a hydrophilic resin such as an epoxy resin is provided on the surface of the resin layer, and then the layer (surface layer) containing a hydrophilic resin such as an epoxy resin is peeled off.

<Paint composition>
A preferred coating composition for forming the resin layer of the laminated film of the present invention will now be described.

The resin layer of the laminated film of the present invention is preferably formed from a coating composition containing a release agent (A) and at least one resin or compound (B) selected from epoxy resins, melamine resins, oxazoline compounds, carbodiimide compounds, polyester resins, acrylic resins, and urethane resins. This configuration makes it easy to obtain good peelability from the surface layer by forming a resin layer having a water contact angle of 95° to 110°, an initial tape peel strength of 0.5 N/50 mm to 4.0 N/50 mm, and a tape peel strength of 8.0 N/50 mm to 14.0 N/50 mm after heating at 100°C for 30 minutes.

<Release Agent (A)>
The release agent (A) in the present invention refers to a compound that imparts releasability (i.e., the property of reducing the surface free energy of the resin or reducing the static friction coefficient μs of the resin) to the surface of the coating layer by being contained in the coating composition. Examples of the release agent (A) that can be used in the present invention include long-chain alkyl group-containing resins, olefin resins, fluorine compounds, wax-based compounds, etc. Among them, long-chain alkyl group-containing resins are preferred in that they can impart good releasability.

A commercially available long-chain alkyl group-containing compound may be used. Specifically, the "Ashio Resin" (registered trademark) series, which is a long-chain alkyl compound manufactured by Asio Sangyo Co., Ltd., the "Peiroil" series, which is a long-chain alkyl compound manufactured by Ipposha Yushi Kogyo Co., Ltd., and the "Rezem" series, which is an aqueous dispersion of a long-chain alkyl compound manufactured by Chukyo Yushi Co., Ltd., may be used. The release agent (A) preferably has an alkyl group having 12 or more carbon atoms, and more preferably has an alkyl group having 16 or more carbon atoms. By making the carbon number of the alkyl group 12 or more, the hydrophobicity is increased, and sufficient release performance as the release agent (A) can be expressed. If the carbon number of the alkyl group is less than 12, the release performance may be insufficient. There is no particular limit to the upper limit of the carbon number of the alkyl group, but it is preferable that it is 25 or less because it is easy to manufacture.

The resin having an alkyl group with 12 or more carbon atoms is more preferably a resin having a side chain of an alkyl group with 12 or more carbon atoms on a polymethylene main chain. By using a polymethylene main chain, the number of hydrophilic groups in the entire resin is reduced, and the release effect of the release agent (A) can be improved.

The presence or absence of an alkyl group having 12 carbon atoms can also be evaluated from the laminate film, for example, by using the intensity of a signal corresponding to an alkyl group obtained by TOF-SIMS (TOF-SIMS: time-of-flight secondary ion mass spectrometry). At this time, by combining the cutting method using ion sputtering, it is possible to perform continuous measurements in the depth direction, and the distribution state of the alkyl group-containing compound can also be evaluated.

<Resin or Compound (B)>
Examples of the resin or compound (B) that can be used in the present invention include epoxy resins, melamine resins, oxazoline compounds, carbodiimide compounds, polyester resins, acrylic resins, urethane resins, etc. Among these, melamine resins and acrylic resins are preferred because they are easy to control the interaction due to the hydroxyl groups and the resin layer is easily changed by high-temperature heating.

Examples of epoxy resins that can be used as the resin or compound (B) include sorbitol polyglycidyl ether-based crosslinking agents, polyglycerol polyglycidyl ether-based crosslinking agents, diglycerol polyglycidyl ether-based crosslinking agents, and polyethylene glycol diglycidyl ether-based crosslinking agents. As the epoxy resin, commercially available products may be used, for example, epoxy compounds "Denacol" (registered trademark) EX-611, EX-614, EX-614B, EX-512, EX-521, EX-421, EX-313, EX-810, EX-830, EX-850, etc. manufactured by Nagase Chemtec Corporation, diepoxy/polyepoxy compounds (SR-EG, SR-8EG, SR-GLG, etc.) manufactured by Sakamoto Yakuhin Kogyo Co., Ltd., epoxy crosslinking agent "EPICLON" (registered trademark) EM-85-75W or CR-5L manufactured by Dainippon Ink Mfg. Co., Ltd., etc. can be suitably used, among which water-soluble ones are preferably used.

Examples of melamine resins that can be used as the resin or compound (B) include melamine, methylolated melamine derivatives obtained by condensing melamine with formaldehyde, compounds partially or completely etherified by reacting methylolated melamine with a lower alcohol, and mixtures of these. The melamine resin may be a condensate of a monomer or a dimer or higher polymer, or a mixture of these. Examples of lower alcohols that can be used for etherification include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, and isobutanol. Examples of functional groups include imino groups, methylol groups, or alkoxymethyl groups such as methoxymethyl groups and butoxymethyl groups in one molecule, such as imino group-type methylated melamine resins, methylol group-type methylated melamine resins, methylol group-type methylated melamine resins, and fully alkylated methylated melamine resins. Among these, methylolated melamine resins are the most preferably used.

The oxazoline compound that can be used as the resin or compound (B) 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 and at least one other monomer.

As monomers containing an oxazoline group, 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 can be used, and one or a mixture of two or more of these can also be used. Among these, 2-isopropenyl-2-oxazoline is suitable because it is easily available industrially.

In an oxazoline compound, at least one other monomer used for a monomer containing an oxazoline group is a monomer that is copolymerizable with the monomer containing an oxazoline group, and examples of such monomers include 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. unsaturated nitriles, unsaturated amides such as acrylamide, methacrylamide, N-methylol acrylamide, and N-methylol methacrylamide, 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, and mixtures of two or more of these can be used.

The carbodiimide compound that can be used as the resin or compound (B) is a compound that has one or more carbodiimide groups or cyanamide groups that are in a tautomeric relationship with the functional group in the molecule. Specific examples of such carbodiimide compounds include dicyclohexylmethane carbodiimide, dicyclohexyl carbodiimide, tetramethylxylylene carbodiimide, and urea-modified carbodiimide, and these can be used alone or in a mixture of two or more kinds.

The polyester resin that can be used as the resin or compound (B) has an ester bond in the main chain or side chain, and is preferably obtained by polycondensation of a dicarboxylic acid and a diol.

Dicarboxylic acids that can be used as raw materials for the polyester resin include aromatic, aliphatic, and alicyclic dicarboxylic acids. Examples of aromatic dicarboxylic acids that can be used 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 that can be used include succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, dimer acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and ester-forming derivatives thereof.

The diol components that are the 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'-isopropylidenebindiol, cyclopentane-1,2-diol, cyclohexane-1,2'-diol, cyclohexane-1,2-diol, cyclohexane-1,4-diol, and the like can be used.

In addition, modified polyester copolymers, such as block copolymers and graft copolymers modified with acrylic, urethane, epoxy, etc., can also be used as the polyester resin.

The acrylic resin that can be used as the resin or compound (B) is not particularly limited, but is preferably composed of an alkyl methacrylate and/or an alkyl acrylate.

As the alkyl methacrylate and/or alkyl acrylate, it is preferable to use methacrylic acid, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, acrylic acid, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, maleic acid, itaconic acid, acrylamide, N-methylol acrylamide, diacetone acrylamide, etc. These can be used alone or in combination of two or more.

The urethane resin that can be used as the resin or compound (B) is preferably a resin obtained by reacting a polyhydroxy compound with a polyisocyanate compound by a known urethane resin polymerization method such as emulsion polymerization or suspension polymerization.

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, polycaprolactone, polyhexamethylene adipate, polyhexamethylene sebacate, polytetramethylene adipate, polytetramethylene sebacate, trimethylolpropane, trimethylolethane, pentaerythritol, polycarbonate diol, and glycerin.

Examples of polyisocyanate compounds that can be used include hexamethylene diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate, an adduct of tolylene diisocyanate and trimethylenepropane, and an adduct of hexamethylene diisocyanate and trimethylolethane.

Furthermore, the resin layer of the laminated film of the present invention may contain an isocyanate compound as the resin or compound (B). Examples of the isocyanate compound include tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, metaxylylene diisocyanate, hexamethylene-1,6-diisocyanate, 1,6-diisocyanatehexane, an adduct of tolylene diisocyanate and hexanetriol, an adduct of tolylene diisocyanate and trimethylolpropane, polyol-modified diphenylmethane-4,4'-diisocyanate, carbodiimide-modified diphenylmethane-4,4'-diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, 3,3'-bitrylene-4,4' diisocyanate, 3,3'dimethyldiphenylmethane-4,4'-diisocyanate, and metaphenylene diisocyanate.

Furthermore, since isocyanate groups react easily with water, blocked isocyanate compounds in which the isocyanate groups are masked with a blocking agent or the like are preferably used in terms of the pot life of the coating material. In this case, when heat is applied in the drying process after the coating composition is applied to the polyester film, the blocking agent dissociates, exposing the isocyanate groups, and the crosslinking reaction proceeds.

In the coating composition constituting the resin layer of the laminated film of the present invention, the mass ratio of the release agent (A) to the resin or compound (B) is preferably in the range of 10/90 to 70/30. More preferably, it is in the range of 15/85 to 65/35. By setting it in this range, the amount of the release agent (A) in the resin layer is sufficient, and the initial tape peeling force and the peeling force from the surface layer after low-temperature heating can be improved. At the same time, the resin or compound (B), which is easily changed by heating, is also in a sufficient amount, and the peeling characteristics before and after heating can be improved.

<Particle Component (C)>
The coating composition forming the resin layer of the laminated film of the present invention may contain a particulate component (C) in addition to the release agent (A) and the resin or compound (B). As described above, the resin layer of the laminated film of the present invention has high slippage when the film surface is smooth, unlike conventional films. In the laminated film of the present invention, when the slippage is so high that the winding property is deteriorated, the coating composition can include the particulate component (C) to impart a protruding shape to the resin layer surface, improving transportability.

As the particle component (C) used in the present invention, fine particles of oxides of elements located on and to the left of the diagonal line connecting boron (B), silicon (Si), arsenic (As), tellurium (Te), and astatine (At) can be suitably used.

Examples of such particulate components ₍ C) include _SiO2 , TiO2, _{ZrO2 ,} ZnO, _CeO2 , _SnO2 , _Sb2O5 , indium-doped tin oxide ( _ITO ) _, phosphorus-doped tin oxide ( _PTO ), _Y2O3 , _La2O3 , and _Al2O3 .

These particle components (C) may be used alone or in combination of two or more. From the viewpoints of dispersion stability and refractive index, _SiO2 , _TiO2 , and _ZrO2 are particularly preferred.

Here, the number average particle diameter of the particle component (C) will be explained. Here, the number average particle diameter refers to the particle diameter determined by a transmission electron microscope (TEM). The magnification is 500,000 times, and the number average particle diameter is obtained by measuring the outer diameters of 10 particles present on the screen for a total of 100 particles in 10 fields of view. Here, the outer diameter refers to the maximum diameter of the particle (i.e., the long diameter of the particle, which indicates the longest diameter among the particles), and in the case of particles having a cavity inside, it also refers to the maximum diameter of the particle.

The particle component (C) used in the resin layer of the laminated film of the present invention preferably has a number average particle diameter of 3 nm or more and 500 nm or less. More preferably, it is 80 nm or more and 400 nm or less, and even more preferably, it is 100 nm or more and 300 nm or less. If the number average particle diameter of the particle component (C) is too small, the van der Waals forces between the particles become very large, and the particles tend to aggregate easily. On the other hand, if the number average particle diameter of the particle component (C) is too large, the particles tend to fall off from the resin layer.

The method for producing the particulate component (C) is not particularly limited, but examples thereof include a method of surface-treating the particulate component (C) with an acrylic resin, and specifically, the following methods (i) to (iv) are exemplified. In the present invention, the surface treatment refers to a treatment in which an acrylic resin is adsorbed and attached to the whole or part of the surface of the particulate component (C).
(i) A method in which a mixture of the particle component (C) and the acrylic resin is mixed in advance, is added to a solvent, and then the mixture is dispersed.
(ii) A method in which the particle component (C) and the acrylic resin are added in that order to a solvent and dispersed therein.
(iii) A method in which the particle component (C) and an acrylic resin are previously dispersed in a solvent, and the resulting dispersion is mixed.
(iv) A method in which the particle component (C) is dispersed in a solvent, and then an acrylic resin is added to the resulting dispersion.

Any of these methods can achieve the desired effect.

As dispersion equipment, a dissolver, a high-speed mixer, a homomixer, a meader, a ball mill, a roll mill, a sand mill, a paint shaker, an SC mill, an annular mill, a pin mill, etc. can be used.

The dispersion method involves using the above device to rotate the rotating shaft at a peripheral speed of 5 to 15 m/s. The rotation time is 5 to 10 hours.

In addition, it is more preferable to use dispersion beads such as glass beads during dispersion in order to improve dispersibility. The bead diameter is preferably 0.05 to 0.5 mm, more preferably 0.08 to 0.5 mm, and particularly preferably 0.08 to 0.2 mm.

Methods for mixing and stirring include shaking the container by hand, using a magnetic stirrer or stirring blade, irradiating with ultrasound, or dispersing with vibration.

The content of the particulate component (C) in the resin layer is preferably 0.5% by mass or more and 10% by mass or less, based on the entire resin layer. More preferably, it is 1% by mass or more and 7% by mass or less, and even more preferably, it is 2% by mass or more and 5% by mass or less. By setting the content of the particulate component (C) to 0.5% by mass or more and 10% by mass or less, based on the entire resin layer, it is possible to impart a surface shape without impairing the film-forming properties of the resin layer. As a result, it is possible to fully express the desired transportability.

<Production Method>
In the laminated film of the present invention, the method of providing a resin layer on at least one surface layer of the polyester film can be either an in-line coating method or an off-coating method. The in-line coating method is a method of coating within the process of manufacturing the polyester film. In particular, it is preferable to manufacture the polyester film by a manufacturing method in which a coating composition containing a release agent (A) is applied to at least one surface layer of the polyester film before the crystal orientation is completed, and then the polyester film is stretched at least in one axial direction and then heat-treated to complete the crystal orientation of the polyester film. The off-coating method is a method of forming the polyester film by applying the above-mentioned coating composition to at least one surface layer of the polyester film after the manufacturing is completed, followed by drying and curing. When the resin layer is cured, a heat treatment is performed, but the in-line coating method is preferred because the flatness of the film may be impaired if a high-temperature heat treatment is performed in the off-coating method.

<Coating method>
The resin composition can be applied to the polyester film by any known coating method, such as a wire bar coating method, a reverse coating method, a gravure coating method, a die coating method, a blade coating method, a dip coating method, an air knife coating method, a curtain coating method, and a roller coating method.

<Method of forming resin layer>
In the present invention, it is preferable to form a resin layer by applying a coating composition to at least one side of a polyester film and then drying the coating composition. In the present invention, when a solvent is contained in the coating composition, it is preferable to use an aqueous solvent as the solvent. By using an aqueous solvent, it is possible to suppress rapid evaporation of the solvent in the drying process, and not only to form a uniform resin layer, but also to be excellent in terms of environmental load.

Here, the aqueous solvent refers to water or a mixture of water and water-soluble organic solvents, such as alcohols (e.g., methanol, ethanol, isopropyl alcohol, butanol, etc.), ketones (e.g., acetone, methyl ethyl ketone, etc.), and glycols (e.g., ethylene glycol, diethylene glycol, propylene glycol, etc.), in any ratio.

The method of applying the coating composition to the film is not particularly limited, but as mentioned above, it is preferably an in-line coating method. Specifically, this refers to a method in which coating is performed at any stage from melt extrusion of the polyester resin to biaxial stretching, heat treatment, and winding up. Usually, the coating is applied to any of the following films: an unstretched (unoriented) film (A film) in a substantially amorphous state obtained by melt extrusion and rapid cooling, a uniaxially stretched (uniaxially oriented) film (B film) that has been subsequently stretched in the longitudinal or width direction, or a biaxially stretched (biaxially oriented) film (C film) that has been further stretched in the width direction or longitudinal direction before heat treatment.

In the present invention, it is preferable to adopt a method in which a coating composition is applied to either the above-mentioned film A or film B before the crystal orientation is completed, and then the film is stretched in a uniaxial or biaxial direction and heat-treated at a temperature higher than the boiling point of the solvent to complete the crystal orientation of the film and provide a resin layer. This method has the advantage of being cost-effective, since the film formation and the coating and drying of the coating composition (i.e., the formation of the resin layer) can be carried out simultaneously.

Among these, the method of applying the coating composition to a film (film B) that has been uniaxially stretched in the longitudinal direction, then stretching it in the width direction and heat treating it is superior. This is because, compared to the method of applying the coating composition to an unstretched film and then biaxially stretching it, this method requires one less stretching step after applying the coating composition, making it less likely for defects or cracks to occur in the resin layer due to stretching, and allowing the formation of a resin layer with excellent smoothness. Also, as mentioned above, applying the coating composition to a film before the completion of crystal orientation can impart adhesion between the resin layer and the polyester film.

Therefore, the preferred method for forming the resin layer in the present invention is to apply a coating composition using an aqueous solvent onto a polyester film using an in-line coating method, followed by drying and heat treatment. More preferably, the coating composition is in-line coated onto the B film after uniaxial stretching. In the method for producing the laminated film of the present invention, drying can be performed at a temperature range of 80 to 130°C to complete removal of the solvent from the coating composition. Heat treatment can be performed at a temperature range of 160 to 240°C to complete the crystal orientation of the polyester film and the thermal curing of the coating composition to complete the formation of the resin layer.

Furthermore, it is preferable that the solids concentration of the coating composition is 40% by mass or less. By setting the solids concentration to 40% by mass or less, it is possible to impart good coatability to the coating composition and produce a laminated film having a uniform resin layer.

The solids concentration refers to the ratio of the mass of the paint composition to the mass of the paint composition, excluding the mass of the solvent (i.e., [solids concentration (mass %)] = [(mass of paint composition) - (mass of solvent)] / [mass of paint composition] x 100).

<Method of manufacturing laminated film>
Next, the manufacturing method of the laminated film of the present invention will be described. First, polyethylene terephthalate (hereinafter, abbreviated as PET) pellets are thoroughly vacuum-dried, then fed into an extruder, melt-extruded into a sheet at about 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 with a roll heated to 80 to 120°C to obtain a uniaxially oriented PET film (film B). At this time, a coating composition containing a release agent (A) prepared to a predetermined concentration may be applied to one side of film B, and further, a surface treatment such as a corona discharge treatment may be performed on the coating surface of the PET film before coating. By performing a surface treatment such as a corona discharge treatment, the wettability of the resin composition to the PET film is improved, repelling of the resin composition is prevented, and a uniform coating thickness can be achieved.

After coating, the PET film is held at the ends with clips and transported to a heat treatment zone (preheating zone) at 80-130°C to dry out the solvent in the coating composition. After drying, the film is stretched 1.1-5.0 times in the width direction. It is then transported to a heating zone (heat treatment zone) at 150-250°C and heat treated for 1-30 seconds to complete the crystal orientation and the formation of the resin layer. During this heating process (heat treatment process), a 3-15% relaxation treatment may be performed in the width or length direction as necessary.

<Methods for measuring characteristics and evaluating effects>
The methods for measuring the characteristics and evaluating the effects of the present invention are as follows.

(1) Initial Tape Peel Strength The initial tape peel strength was measured as follows.
First, an acrylic polyester adhesive tape (Nitto 31B tape, 19 mm width, manufactured by Nitto Denko Corporation) was laminated on the resin layer of the laminate film of the present invention, and a 2 kgf roller was run back and forth once on the tape laminate film to prepare a tape laminate film. After that, the tape laminate film was left to stand for 24 hours in an environment of 25°C and 65% RH, and then the peel force (N/19 mm) was measured at a peel angle of 180° and a tensile speed of 300 mm/min using a universal testing machine "Autograph AG-1S" manufactured by Shimadzu Corporation. From the graph of peel force (N/19 mm) vs. test time (sec) obtained by the measurement, the average peel force value in the period from 5 to 10 sec was calculated. This measurement was performed five times, and the average of the three measurements excluding the maximum and minimum values was taken as the peel strength of the laminated film (N/19 mm). This value was converted to N/50 mm to obtain the initial tape peel strength (i.e., [initial tape peel strength (N/50 mm)] = [peel strength (N/19 mm)]/19 x 50).

(2) Tape peeling strength after heating at 100° C. for 30 minutes The tape peeling strength after heating at 100° C. for 30 minutes was measured as follows.
First, an acrylic polyester adhesive tape (Nitto 31B tape, 19 mm width, manufactured by Nitto Denko Corporation) was laminated on the resin layer of the laminated film of the present invention, and a 2 kgf roller was run back and forth once on the laminated film to prepare a tape-laminated laminated film. After that, the tape-laminated laminated film was heated in a hot air oven at 100°C for 30 minutes, and then the peel force (N/19 mm) was measured at a peel angle of 180° and a tensile speed of 300 mm/min using a universal testing machine "Autograph AG-1S" manufactured by Shimadzu Corporation. From the graph of peel force (N/19 mm) vs. test time (sec) obtained by the measurement, the average peel force value in the period from 5 to 10 sec was calculated. This measurement was performed five times, and the average of the three measurements excluding the maximum and minimum values was taken as the peel strength of the laminated film (N/19 mm). This value was converted to N/50 mm and used as the tape peel strength after heating at 100°C for 30 minutes (i.e., [tape peel strength after heating at 100°C for 30 minutes (N/50 mm)] = [peel strength (N/19 mm)]/19 x 50).

(3) Method for calculating water contact angle and surface free energy First, the laminated film is left for 24 hours in an atmosphere of room temperature 23°C and relative humidity 65%. Then, in the same atmosphere, the contact angles of four types of solutions, pure water, ethylene glycol, formamide, and diiodomethane, on the surface side of the resin layer of the laminated film are measured at five points for each solution using a contact angle meter DropMaster DM-501 manufactured by Kyowa Interface Science Co., Ltd. The average value of the three measured values excluding the maximum and minimum values of the five measured values is taken as the contact angle of each solution.

Next, using the contact angles of the four types of solutions obtained, the surface free energy of the present invention, which ^is the dispersion force, polar force, hydrogen bonding force, and the sum of the dispersion force and polar ^force , is calculated by the geometric mean method based on the formula proposed by Hata ^et _al ., which is an extension of the Fowkes formula (extended Fowkes formula) by separating the surface free energy of a solid ( _γ ) into three components: a dispersion force component ( _γ S d ), a polar force component (γ S p ), and a hydrogen bonding force component (γ S h ).

A specific calculation method is shown below. The meaning of each symbol is explained below. When _{γ S} ^L is the tension at the interface between a solid and a liquid, the following formula (1) is established.

_γS ^L : surface free energy of the resin layer and the known ^solution listed in Table 1 _γS : surface free energy of the resin layer _γL : surface ^free energy of the known solution listed in Table 1 _γSd : dispersion force component of the surface free energy of the resin layer _γSp : polar force component of the surface free energy of the resin layer _γSh : hydrogen bonding force component of the surface free energy of the resin ^layer _γLd : dispersion force component of the surface free energy of the known solution listed in Table 1 _γLp ^: polar force component of the ^surface free energy of the known solution listed in Table 1 _γLh : hydrogen bonding ^{force component of the surface free energy of the known solution listed in Table 1 γS L} ₌ ^γS _{+ γL} - 2 ⁽ _γSd・_{γLd )} ^1/2 - ^2(γSp _・ ^γLp ₎ ^1/2 - ² ( ^γSh・_γLh ) ^1/2 ... Formula (1).

In addition, the state when a droplet is in contact with a smooth solid surface at a contact angle (θ) is expressed by the following equation (Young's equation).

^γ _S = γ _SL + γ _L cosθ... Formula (2).

Combining these formulas (1) and (2), the following formula is obtained.
(γ _S ^d・γ _L ^d ) ^1/2 + (γ _S ^p・γ _L ^p ) ^1/2 + (γ _S ^h・γ _L ^h ) ^1/2 = γ _L (1+cosθ)/2 ... Formula (3).

In practice, the contact angles (θ) of four types of solutions, namely water, ethylene glycol, formamide, and diiodomethane, and the components of the surface tensions of known solutions (γ _L ^d , γ _L ^p , γ _L ^h ) listed in Table 1 are substituted into Equation (3) to solve four simultaneous equations. As a result, the surface free energy (γ), dispersion force component (γ _S ^d ), polar force component (γ _S ^p ), and hydrogen bonding force component (γ _S ^h ) of the solid are calculated.

(4) Method for Analyzing the Composition of the Resin Layer Surface The composition of the resin layer surface of the laminated 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 ⁺⁺ (25 keV)
Secondary ion polarity: Negative
Mass range: m/z 0-1000
Measurement range: 200 x 200 ^μm2
The peak intensity of the fragment detected at the maximum intensity was defined as K, and the peak intensity of the fragment derived from polydimethylsiloxane (SiCH ₃ ⁺ fragment ion (M/Z=43)) was defined as P, and the ratio P/K was calculated. When P/K<0.01, it was determined that the resin layer did not substantially contain a silicone compound.

(5) Resin layer thickness The laminated film was dyed with _RuO4 and/or _OsO4 . Next, the laminated film was frozen and cut in the film thickness direction to obtain 10 ultrathin slice samples for observing the cross section of the resin layer. The cross section of each sample was observed at 10,000 to 1,000,000 magnifications with a TEM (transmission electron microscope: H7100FA type manufactured by Hitachi, Ltd.) to obtain a cross-sectional photograph. The measured values of the resin layer thickness of the 10 samples were averaged to obtain the resin layer thickness of the laminated film.

(6) Initial Epoxy Resin Peel Strength For the initial epoxy resin peel strength, an epoxy resin mixed in the following composition was applied to the resin layer of the laminated film of the present invention using an applicator so that the final thickness was 40 μm, and then dried in a hot air oven at 100°C for 5 minutes to form an epoxy resin laminated sheet. An acrylic polyester adhesive tape (Nitto 31B tape, 19 mm width, manufactured by Nitto Denko Corporation) was attached as a support to the epoxy resin of the epoxy resin laminated sheet, and the peel strength (N/19 mm) was measured at a peel angle of 180° and a tensile speed of 300 mm/min using a universal testing machine "Autograph AG-1S" manufactured by Shimadzu Corporation. The average peel strength at 5 to 10 seconds was calculated from the graph of peel strength (N/19 mm) vs. test time (sec) obtained by the measurement. This measurement was performed five times, and the average of the three measurements excluding the maximum and minimum values was taken as the peel strength of the laminated film (N/19 mm). This value was converted to N/50 mm to obtain the initial epoxy resin peel strength (i.e., [initial epoxy resin peel strength (N/50 mm)]=[peel strength (N/19 mm)]/19×50).
The following evaluation was performed: ◯ was good, and Δ was no problem in practical use.
○: Initial epoxy resin peel strength 8.5 N/50 mm or more △: Initial epoxy resin peel strength 2.0 N/50 mm or more and less than 8.5 N/50 mm
×: Initial epoxy resin peel strength is less than 2.0 N/50 mm.

(7) Epoxy resin peel strength after heating The epoxy resin peel strength after heating was measured as follows. The epoxy resin laminate sheet described in the section "(6) Initial epoxy resin peel strength" was further subjected to a heat treatment at 150°C for 30 minutes in a hot air oven to form a heated epoxy resin laminate sheet. An acrylic polyester adhesive tape (Nitto 31B tape, 19 mm width, manufactured by Nitto Denko Corporation) was attached as a support to the epoxy resin of the heated epoxy resin laminate sheet, and the peel strength (N/19 mm) was measured at a peel angle of 180° and a tensile speed of 300 mm/min using a universal testing machine "Autograph AG-1S" manufactured by Shimadzu Corporation. From the graph of peel strength (N/19 mm) vs. test time (sec) obtained by the measurement, the average peel strength over 5 to 10 sec was calculated. This measurement was performed five times, and the average of the three measurements excluding the maximum and minimum values was taken as the peel strength of the laminated film (N/19 mm). This value was converted to N/50 mm and used as the peel strength of the epoxy resin after heating (i.e., [epoxy resin peel strength after heating (N/50 mm)] = [peel strength (N/19 mm)]/19 x 50).

(8) Evaluation of epoxy resin peelability after heating From the peel strengths calculated in the sections "(6) Initial epoxy resin peel strength" and "(7) Epoxy resin peel strength after heating", the difference in epoxy resin peel strength before and after heating (Δ peel strength) was calculated using the following formula, and the following evaluations were made. A score of ◯ or higher was considered good, and Δ was considered to be at a level that did not pose any practical problems.
[Δ peel force (N/50 mm)] = initial epoxy resin peel force - epoxy resin peel force after heating. ○: Δ peel force is 7.0 N/50 mm or more and 10.0 N/50 mm or less. △: Δ peel force is 1.0 N/50 mm or more and less than 7.0 N/50 mm. ×: Δ peel force is less than 1.0 N/50 mm, or Δ peel force is 10.0 N/50 mm or more.

(9) Epoxy resin coatability Epoxy resin having the composition shown in the section "(6) Initial epoxy resin peel strength" was applied to the resin layer of the laminated film of the present invention with an applicator to three different final thicknesses (40 μm, 10 μm, 1 μm), and then dried in a hot air oven at 100°C for 5 minutes to form an epoxy resin laminated film. The epoxy resin laminated film was visually evaluated for the presence or absence of cissing. Slurry coatability of ◯ or above was considered to be good, and △ was considered to be at a level that was not problematic in practical use. In general, the thinner the epoxy resin coating thickness, the more likely cissing is to occur.

◎: No repelling observed at any coating thickness.

○: No repelling was observed at coating thicknesses of 40 μm and 10 μm, but repelling was observed at 1 μm.

△: No repelling was observed at a coating thickness of 40 μm, but repelling was observed at 10 μm and 1 μm.

×: Repelling is observed at all application thicknesses.

(10) Measurement of elastic modulus by atomic force microscope (AFM) The elastic modulus of the surface of the resin layer was measured using an AFM (Dimension Icon manufactured by Burker Corporation) in PeakForceQNM mode. From the obtained force curve, an analysis based on the JKR contact theory was performed using the attached analysis software "NanoScopeAnalysis V1.40" to obtain the elastic modulus distribution.

Specifically, the laminated film was fixed to the sample stage using double-sided tape so that the measurement surface was on the upper surface. Next, the cantilever's warpage sensitivity, spring constant, and tip curvature were configured according to the PeakForceQNM mode manual, and then measurements were performed under the following conditions, and the data of the DMT Modulus channel obtained was adopted as the elastic modulus of the resin layer. Note that the spring constant and tip curvature vary depending on the individual cantilever, but a cantilever that satisfies the conditions of a spring constant of 0.3 (N/m) or more and 0.5 (N/m) or less and a tip curvature radius of 15 (nm) or less was adopted and used for the measurement as a range that does not affect the measurement. The measurement conditions are shown below.
Measurement equipment: Atomic force microscope (AFM) manufactured by Burker Corporation
Measurement mode: PeakForceQNM (force curve method)
Cantilever: Bruker AXS SCANASYST-AIR
(Material: Si, spring constant K: 0.4 (N/m), tip curvature radius R: 2 (nm))
Measurement atmosphere: 23°C, in air Measurement range: 5 (μm) Square resolution: 512 x 512
Cantilever movement speed: 10 (μm/s)
Maximum pressing load: 10 (nN).

Then, the obtained DMT Modulus channel data was analyzed using the analysis software "NanoScopeAnalysis V1.40", and the Image Raw Mean value in the Results tab obtained by processing it with Roughness was used as the elastic modulus of the resin layer.

(11) Measurement of static friction coefficient μs The static friction coefficient μs was measured using a static friction coefficient measuring instrument (manufactured by HEIDON). During the measurement, a sample cut to 200 mm x 100 mm from the laminated film was placed on the rising plate side of the measuring instrument. Next, a sample cut to 75 mm x 35 mm from the laminated film was placed on the flat indenter side of the measuring instrument. At this time, the static friction coefficient μs was measured by making the resin layer surfaces of the laminated film contact each other.

(12) Measurement of the average number of protrusions The average number of protrusions with a protrusion height of 25 nm or more was measured using an AFM (Dimension Icon manufactured by Bulker Corporation) in Scan Asyst mode. Protrusions of a specific height were extracted from the obtained surface roughness image using the attached analysis software "NanoScope Analysis V1.40".

Specifically, the laminated film was fixed to a sample stage using double-sided tape so that the measurement surface was on top. Then, the surface shape of the sample was measured according to the manual for the ScanAsyst mode. The measurement conditions are shown below.
Measurement equipment: Atomic force microscope (AFM) manufactured by Burker Corporation
Measurement mode: PeakForceQNM (force curve method)
Cantilever: Bruker AXS SCANASYST-AIR
(Material: Si, spring constant K: 0.4 (N/m), tip curvature radius R: 2 (nm))
Measurement atmosphere: 23°C, in air Measurement range: 10 (μm) Square resolution: 512 x 512
Cantilever movement speed: 20 (μm/s)
The data of the HeightSensor channel obtained was then analyzed using the analysis software "NanoScopeAnalysis V1.40". First, smoothing was performed using Flatten under the condition of Flatten Order: 3rd. Then, the protrusions were extracted using Bearing Analysis. Specifically, the threshold value (Threshold) of the BearingArea was set so that the Bearing Depth was 25 nm, and domains with a protrusion height of 25 nm or more were selected. The number of selected regions was then counted, and the number per 1 μm ² was obtained. The same measurement was repeated five times, and the average value was obtained as the average number of protrusions (pieces/μm ² ) with a protrusion height of 25 nm or more.

(13) Evaluation of the slipperiness of the laminated film The laminated film was cut to 5 cm x 10 cm and fixed with tape in the center of a 10 cm x 10 cm glass plate so that the resin layer surface of the laminated film was facing up. Next, the same laminated film was cut to 5 cm x 5 cm and superimposed on the laminated film on the glass plate so that the resin layer surfaces of the laminated film were in contact with each other. A weight of 2 kg was then placed on top of it. Next, one end of the glass plate was gradually lifted, and the angle at which the film began to slide was evaluated. The following five-level classification was carried out, and a grade of 3 or more was judged to be acceptable for transportability.
1: Starts to slip between 0 and 5 degrees, or does not slip at all even when it exceeds 45 degrees.
2: Starts sliding between 30 degrees and 45 degrees.
3: The slide begins between 5 degrees and 10 degrees.
4: The slide begins between 10 degrees and 15 degrees.
5: The slide begins between 15 degrees and 30 degrees.

(14) Thermal shrinkage of laminated film A laminated film was cut into a width of 10 mm and a length of 150 mm, with the width direction of the film being the length direction, and two lines were drawn on the surface of the film so that the measurement length was 100 mm. The distance between the two lines was measured at 23° C. and designated as L0. The laminated film was left in an oven at 180° C. for 15 minutes under a load of 3.0 g, and then the distance between the two lines was measured again at 23° C. and designated as L1. The thermal shrinkage was calculated from the following formula.

Heat shrinkage rate (%) = {(L0 - L1) / L0} x 100
The film was cut lengthwise across the width of the film, and measurements were taken at three locations, and the average value was calculated.

(15) Floating Inhibition Property For the floating inhibition property, an epoxy resin mixed in the following composition was applied to the resin layer of the laminated film of the present invention using an applicator so as to give a final thickness of 40 μm, and then dried in a hot air oven at 100° C. for 5 minutes to form an epoxy resin laminated sheet. A 10 cm square sheet of the epoxy resin laminated sheet was left in an atmosphere of 60° C. and 90% RH for 100 hours, then taken out into an atmosphere of 23° C. and 50% RH, and the state of the epoxy resin laminated sheet was visually observed after 1 hour to evaluate the floating inhibition property.
<Criteria for evaluating anti-floating properties>
⊚: No floating, peeling or air bubbles were observed.
Good: Floating, peeling or air bubbles are present at the edges.
△: Floating, peeling or air bubbles occurred in the center.
×: Lifting, peeling or bubbles are observed over the entire surface.
The following evaluation was performed: ◯ was good, and Δ was no problem in practical use.

In the above evaluation, if the longitudinal and width directions of the film are unknown, the direction with the maximum refractive index in the film is considered to be the width direction, and the direction perpendicular to the width direction is considered to be the longitudinal direction.

(16) Evaluation method of resin layer thickness A sample was prepared for the laminated film by the _OsO4 staining ultrathin section method. The cross section of the obtained sample was observed using a transmission electron microscope (TEM) to measure the thickness of the resin layer on the laminated film. The thickness of the resin layer was read from an image taken at a magnification of 200,000 times by TEM. The thickness of the resin layer was measured at 20 points, and the average value was taken as the thickness (nm) of the resin layer.
Measurement equipment: Transmission electron microscope (Hitachi, Ltd., H-7100FA type).

(17) Transfer suppression property during epoxy resin peeling The transfer suppression property during epoxy resin peeling was evaluated by the reduction rate of the film thickness of the resin layer of the laminated film. The initial film thickness of the resin layer of the laminated film was defined as d0 (nm), and the film thickness of the resin layer of the laminated film after the evaluation of "(7) Epoxy resin peel strength after heating" was defined as d1 (nm), and the reduction rate was calculated by the following formula.

Reduction rate of resin layer thickness (%)={(d0−d1)/d0}×100
The compounds were classified into the following four stages, and 1 and 2 were judged to pass the transcriptional inhibition test.
1: The reduction rate of the film thickness is 10% or less.
2: The rate of decrease in film thickness is more than 10% and 20% or less.
3: The rate of reduction in film thickness is more than 20% and 50% or less.
4: The reduction rate of the film thickness exceeds 50%.

The laminated 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. However, the following Examples 1 to 32, 35, 36, and 40 to 44 are reference examples.

Example 1
Release agent (A): Long-chain alkyl group-containing resin (a-1)
200 parts of xylene and 600 parts of octadecyl isocyanate were added to a four-neck flask and heated under stirring. From the point when xylene started to reflux, 100 parts of polyvinyl alcohol with an average degree of polymerization of 500 and a degree of saponification of 88 mol% were added in small portions at 10-minute intervals over about 2 hours. After the addition of polyvinyl alcohol was completed, the mixture was refluxed for another 2 hours to terminate the reaction. The reaction mixture was cooled to about 80°C and then added to methanol, whereupon the reaction product precipitated as a white precipitate. The precipitate was filtered off, 140 parts of xylene was added, heated to completely dissolve the reaction product, and then methanol was added again to precipitate the reaction product. This operation was repeated several times, and the precipitate was washed with methanol and dried and pulverized to obtain a long-chain alkyl group-containing resin (a-1: polymethylene as the main chain and having an alkyl group with 18 carbon atoms on the side chain). This was diluted with water to adjust to 20% by mass.

Resin or compound (B): Acrylic resin (b-1)
Methyl methacrylate (α), hydroxyethyl methacrylate (β), and urethane acrylate oligomer (Art Resin (registered trademark) UN-3320HA, number of acryloyl groups: 6) (γ) were charged in a stainless steel reaction vessel in a mass ratio of (α)/(β)/(γ)=94/1/5, and 2 parts by mass of sodium dodecylbenzenesulfonate was added as an emulsifier to a total of 100 parts by mass of (α) to (γ) and stirred to prepare mixed solution 1. Next, a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer, and a dropping funnel was prepared. 60 parts by weight of the above mixed solution 1, 200 parts by weight of isopropyl alcohol, and 5 parts by weight of potassium persulfate as a polymerization initiator were charged in a reaction apparatus and heated to 60° C. to prepare mixed solution 2. Mixed solution 2 was kept heated at 60° C. for 20 minutes. Next, mixed solution 3 consisting of 40 parts by weight of mixed solution 1, 50 parts by weight of isopropyl alcohol, and 5 parts by weight of potassium persulfate was prepared. Then, mixed solution 3 was dropped into mixed solution 2 over 2 hours using a dropping funnel to prepare mixed solution 4. Then, mixed solution 4 was heated to 60 ° C. and held for 2 hours. The obtained mixed solution 4 was cooled to 50 ° C. or less and then transferred to a container equipped with a stirrer and a pressure reducing device. 60 parts by weight of 25% ammonia water and 900 parts by weight of pure water were added thereto, and isopropyl alcohol and unreacted monomers were recovered under reduced pressure while heating to 60 ° C., and an acrylic resin (b-1) dispersed in pure water was obtained.

Coating composition:
The release agent (A) and the resin or compound (B) were mixed so that the solid content mass ratio was (A)/(B) = 15/85. Furthermore, in order to improve the coatability onto polyester film, a fluorine-based surfactant ("Pluscoat" RY-2, manufactured by GOO Chemical Industry Co., Ltd.) was added in an amount of 0.1 part by mass per 100 parts by mass of the total mixed coating composition.

・Polyester film:
PET pellets (intrinsic viscosity 0.64 dl/g) 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) were thoroughly vacuum-dried, fed to an extruder, melted at 280° C., extruded from a T-shaped die into a sheet, and wrapped around a mirror-finished casting drum with a surface temperature of 25° C. by an electrostatic casting method, where it was cooled and solidified. This unstretched film was heated to 90° C. and stretched 3.1 times in the longitudinal direction to produce a uniaxially stretched film (film B).

・Laminated film After subjecting the uniaxially stretched film to a corona discharge treatment in air, the coating composition shown in Table 1 was applied to a coating thickness of about 6 μm using a wire bar coater. Then, both ends in the width direction of the uniaxially stretched film to which the coating composition was applied were held with clips and introduced into a preheating zone. The atmospheric temperature in the preheating zone was set to 90 to 100 ° C, and the solvent of the coating composition was dried. Then, the film was continuously stretched 3.6 times in the width direction in a 100 ° C stretching zone, and then heat-treated for 20 seconds in a 240 ° C heat treatment zone to form a resin layer, and further subjected to a 5% relaxation treatment in the width direction at the same temperature to obtain a laminated film in which the crystal orientation of the polyester film was completed. In the obtained laminated film, the thickness of the PET film was 50 μm and the thickness of the resin layer was 70 nm.

The properties of the obtained laminated film are shown in Tables 2 and 3. The epoxy resin had good coatability, the initial epoxy resin peel strength was heavy, and the epoxy resin peel strength after heating was light, and the peel strength due to heating was also good.

Example 2
A laminated film was obtained in the same manner as in Example 1, except that the following melamine resin (b-2) was used as the resin or compound (B) and the ratio of the coating composition was changed as shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Both the coating property of the epoxy resin and the peeling property by heating were good.

Resin or compound (B): Melamine resin (b-2: methylol melamine)
"Nicalac" (registered trademark) MW-035 (solid content concentration 70% by mass, solvent: water) manufactured by Sanwa Chemical Co., Ltd. was used.

(Examples 3 to 7)
A laminated film was obtained in the same manner as in Example 1, except that the mass ratio of the release agent (A) and the resin or compound (B) was changed to the mass ratio shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the peeling properties by heating were inferior but within a good range, and the coatability of the epoxy resin was also good.

(Examples 8 to 12)
A laminated film was obtained in the same manner as in Example 2, except that the mass ratio of the release agent (A) and the resin or compound (B) was changed to the mass ratio shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 2, the peeling properties by heating were inferior but within a good range, and the coatability of the epoxy resin was also good.

Example 13
A laminated film was obtained in the same manner as in Example 1, except that the following oxazoline compound (b-3) was used as the resin and compound (B). The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the peeling properties by heating were inferior but within a good range, and the coating properties of the epoxy resin were also good. Oxazoline compound (b-3): "Epocross" (registered trademark) WS-500 (solid content concentration 40 mass%, solvent: water), manufactured by Nippon Shokubai Co., Ltd.
(Example 14)
A laminated film was obtained in the same manner as in Example 1, except that the following carbodiimide compound (b-4) was used as the resin and compound (B). The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the peeling properties by heating were inferior but within a good range, and the coatability of the epoxy resin was also good.
Carbodiimide compound (b-4): "Carbodilite" (registered trademark) V-04 (solid content concentration 40 mass%, solvent: water), manufactured by Nisshinbo Chemical Co., Ltd.
(Example 15)
A laminated film was obtained in the same manner as in Example 1, except that the following epoxy resin (b-5) was used as the resin and compound (B). The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the peeling properties by heating were inferior but within a good range, and the coatability of the epoxy resin was also good.
Epoxy resin (b-5): "Denacol" (registered trademark) EX-512 (solid content concentration 50% by mass, solvent: water) manufactured by Nagase Chemtec Corporation was used.

(Example 16)
A laminated film was obtained in the same manner as in Example 1, except that the following polyester resin (b-6) was used as the resin and compound (B). The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the peeling properties by heating were inferior but within a good range, and the coatability of the epoxy resin was also good.
Polyester resin (b-6): A water dispersion of a polyester resin having the following copolymer composition was prepared.
<Copolymerization component>
(Dicarboxylic acid component)
Dimethyl 2,6-naphthalenedicarboxylate: 88 mol%
Sodium dimethyl 5-sulfoisophthalate: 12 mol%
(Diol component)
Compound in which 2 moles of ethylene oxide are added to 1 mole of bisphenol S: 86 mole %
1,3-propanediol: 14 mol%
(Example 17)
A laminated film was obtained in the same manner as in Example 1, except that the following urethane resin (b-7) was used as the resin and compound (B). The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the peeling properties by heating were inferior but within a good range, and the coatability of the epoxy resin was also good.
Urethane resin (b-7): "HYDRAN" (registered trademark) AP-40 (solid content concentration 40% by mass) manufactured by DIC Corporation was used.

(Example 18)
A laminated film was obtained in the same manner as in Example 1, except that the following acrylic resin (b-8) was used as the resin and compound (B). The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the peeling properties by heating were inferior but within a good range, and the coatability of the epoxy resin was also good.

Resin or compound (B): Acrylic resin (b-8)
Methyl methacrylate (α), hydroxyethyl methacrylate (β), and urethane acrylate oligomer (Art Resin (registered trademark) UN-3320HA, number of acryloyl groups: 6) (γ) were charged in a stainless steel reaction vessel in a mass ratio of (α)/(β)/(γ)=90/5/5, and 2 parts by mass of sodium dodecylbenzenesulfonate was added as an emulsifier to a total of 100 parts by mass of (α) to (γ) and stirred to prepare mixed solution 1. Next, a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer, and a dropping funnel was prepared. 60 parts by weight of the above mixed solution 1, 200 parts by weight of isopropyl alcohol, and 5 parts by weight of potassium persulfate as a polymerization initiator were charged in a reaction apparatus and heated to 60° C. to prepare mixed solution 2. Mixed solution 2 was kept heated at 60° C. for 20 minutes. Next, mixed solution 3 consisting of 40 parts by weight of mixed solution 1, 50 parts by weight of isopropyl alcohol, and 5 parts by weight of potassium persulfate was prepared. Then, mixed solution 3 was dropped into mixed solution 2 over 2 hours using a dropping funnel to prepare mixed solution 4. Then, mixed solution 4 was heated to 60 ° C. and held for 2 hours. The obtained mixed solution 4 was cooled to 50 ° C. or less and then transferred to a container equipped with a stirrer and a pressure reducing device. 60 parts by weight of 25% ammonia water and 900 parts by weight of pure water were added thereto, and isopropyl alcohol and unreacted monomers were recovered under reduced pressure while heating to 60 ° C., and an acrylic resin (b-8) dispersed in pure water was obtained.

(Example 19)
A laminated film was obtained in the same manner as in Example 1, except that an acrylic resin (b-1) and a melamine resin (b-2) were used as the resin and compound (B) and the ratio of the coating composition was changed as shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the peeling properties by heating were inferior but within a good range, and the coatability of the epoxy resin was also good.

(Example 20)
A laminated film was obtained in the same manner as in Example 1, except that an acrylic resin (b-1) and an oxazoline compound (b-3) were used as the resin and compound (B) and the ratio of the coating composition was changed as shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the peeling properties by heating were inferior but within a good range, and the coatability of the epoxy resin was also good.

(Example 21)
A laminated film was obtained in the same manner as in Example 1, except that the following olefin resin (a-2) was used as the release agent (A). The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the peeling properties by heating were inferior but still within a good range, and the coatability of the epoxy resin was also good.
Olefin resin (a-2): "CHEMIPEARL" (registered trademark) XEP800H, manufactured by Mitsui Chemicals, Inc.

(Examples 22 to 23)
A laminated film was obtained in the same manner as in Example 1, except that the thickness of the resin layer was changed as shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the peeling properties by heating were inferior but within a good range, and the coatability of the epoxy resin was also good.

(Examples 24 to 25)
A laminated film was obtained in the same manner as in Example 2, except that the thickness of the resin layer was changed as shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 2, the peeling properties by heating were inferior but within a good range, and the coatability of the epoxy resin was also good.

(Example 26)
A laminated film was obtained in the same manner as in Example 1, except that the following silicone resin (a-3) was used as the release agent (A) and the melamine resin (b-2) was used as the resin and compound (B). The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, both the coating property of the epoxy resin and the peeling property by heating were inferior, but were within a good range.
Silicone resin (a-3):
A coating agent containing a silicone component manufactured by Shin-Etsu Chemical Co., Ltd., model number X-62-7655, a coating agent containing a silicone component manufactured by Shin-Etsu Chemical Co., Ltd., model number X-62-7622, and a catalyst manufactured by Shin-Etsu Chemical Co., Ltd., model number CAT-7605 were mixed in a mass ratio of 95:5:1.

(Example 27)
A laminated film was obtained in the same manner as in Example 24, except that the mass ratio of the release agent (A) and the resin or compound (B) was changed to the mass ratio shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 25, both the coating property of the epoxy resin and the peeling property by heating were inferior, but were within a good range.

(Example 28)
A laminated film was obtained in the same manner as in Example 1, except that the following long-chain alkyl group-containing resin (a-4) was used as the release agent (A). The properties of the obtained laminated film are shown in Tables 2 and 3. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the peeling properties by heating were inferior but within a good range, and the coatability of the epoxy resin was also good.
Long-chain alkyl group-containing resin (a-4)
A long-chain alkyl group-containing resin (a-4: having a polymethylene main chain and an alkyl group having 12 carbon atoms on the side chain) was obtained by synthesizing the long-chain alkyl group-containing resin (a-4) in the same manner as in the long-chain alkyl group-containing resin (a-1), except that dodecyl isocyanate was used instead of octadecyl isocyanate.

(Example 29)
A laminated film was obtained in the same manner as in Example 1, except that the following long-chain alkyl group-containing resin (a-5) was used as the release agent (A). The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the water contact angle of the resin layer was small and the slurry peeling force was large, but both the coating property and peeling property of the ceramic slurry were good.
Long-chain alkyl group-containing resin (a-5)
A long-chain alkyl group-containing resin (a-5: having a polymethylene main chain and an alkyl group having 8 carbon atoms in the side chain) was obtained by synthesizing the long-chain alkyl group-containing resin (a-5) in the same manner as the long-chain alkyl group-containing resin (a-1), except that octyl isocyanate was used instead of octadecyl isocyanate.

(Example 30)
A laminated film was obtained in the same manner as in Example 1, except that the resin or compound (B) was not used. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the peeling properties by heating were inferior but within a good range, and the coatability of the epoxy resin was also good.

(Example 31)
First, in the method for producing the polyester film of Example 1, except that the coating composition was not applied at the stage of the uniaxially stretched film (B film), a polyester film with completed crystal orientation was obtained in the same manner as in Example 1. Next, the coating composition shown in Table 1 was applied to the polyester film with a coating thickness of about 2 μm using a bar coater. Thereafter, the film was dried in a 100° C. oven for 20 seconds, and then heat-treated in a 240° C. oven for 20 seconds to form a resin layer, thereby obtaining a laminated film. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the peeling properties due to heating were inferior but within a good range, and the coating properties of the epoxy resin were also good.

(Example 32)
First, in the method for producing the polyester film of Example 2, a polyester film with completed crystal orientation was obtained in the same manner as in Example 2, except that the coating composition was not applied at the stage of the uniaxially stretched film (B film). Next, the coating composition shown in Table 1 was applied to the polyester film with a coating thickness of about 2 μm using a bar coater. Thereafter, the film was dried in a 100° C. oven for 20 seconds, and then heat-treated in a 240° C. oven for 20 seconds to form a resin layer, thereby obtaining a laminated film. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 2, both the coating property of the epoxy resin and the peeling property by heating were inferior, but were within a good range.

(Example 33)
A laminated film was obtained in the same manner as in Example 1, except that (C-1) was used as the particles (C) and the mass ratio of the coating composition was changed to the mass ratio shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Both the coating property of the epoxy resin and the peeling property by heating were good.
Particles (C-1): "Spherica" (registered trademark) 140 (silica particles, particle diameter 140 nm) manufactured by Catalysts and Chemicals Co., Ltd.
(Example 34)
A laminated film was obtained in the same manner as in Example 1, except that (C-1) was used as the particles (C) and the mass ratio of the coating composition was changed to the mass ratio shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Both the coating property of the epoxy resin and the peeling property by heating were good.

(Example 35)
A laminated film was obtained in the same manner as in Example 1, except that (C-1) was used as the particles (C) and the mass ratio of the coating composition was changed to the mass ratio shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Both the coating property of the epoxy resin and the peeling property by heating were good.

(Example 36)
A laminated film was obtained in the same manner as in Example 1, except that (C-2) was used as the particles (C) and the mass ratio of the coating composition was changed to the mass ratio shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Both the coating property of the epoxy resin and the peeling property by heating were good.
Particles (C-2): "Sea Hoster" (registered trademark) KEW-30 (silica particles, particle diameter 500 nm) manufactured by Nippon Shokubai Co., Ltd.
(Example 37)
A laminated film was obtained in the same manner as in Example 1, except that (C-2) was used as the particles (C) and the mass ratio of the coating composition was changed to the mass ratio shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Both the coating property of the epoxy resin and the peeling property by heating were good.

(Example 38)
A laminated film was obtained in the same manner as in Example 1, except that (C-3) was used as the particles (C) and the mass ratio of the coating composition was changed to the mass ratio shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Both the coating property of the epoxy resin and the peeling property by heating were good.
Particles (C-3): "NanoTek" manufactured by CI Kasei Co., Ltd. ( _TiO2 slurry, number average particle diameter 36 nm)
(Example 39)
A laminated film was obtained in the same manner as in Example 1, except that (C-4) was used as the particles (C) and the mass ratio of the coating composition was changed to the mass ratio shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Both the coating property of the epoxy resin and the peeling property by heating were good.
Particles (C-4): "Nanouse" (registered trademark) ZR (zirconia particles, number average particle diameter 90 nm) manufactured by Nissan Chemical Industries, Ltd.
(Example 40)
A laminated film was obtained in the same manner as in Example 1, except that (C-5) was used as the particles (C) and the mass ratio of the coating composition was changed to the mass ratio shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Both the coating property of the epoxy resin and the peeling property by heating were good.
Particles (C-5): "SZR-CW" manufactured by Sakai Chemical Industry Co., Ltd. (zirconium oxide particles, number average particle diameter 20 nm)
(Example 41)
A laminated film was obtained in the same manner as in Example 1, except that the relaxation treatment in the width direction was changed to 2%. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared with Example 1, the heat shrinkage rate was larger at 1.0%, and the lift-suppressing property was further improved.

(Example 42)
A laminated film was obtained in the same manner as in Example 1, except that the relaxation treatment in the width direction was changed to 1%. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared with Example 1, the heat shrinkage rate was larger at 1.3%, and the lift-suppressing property was further improved.

(Example 43)
Except for not carrying out the relaxation treatment in the width direction, a laminated film was obtained in the same manner as in Example 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the heat shrinkage rate was large at 4.3%, and the lift-suppressing property was slightly inferior.

(Example 44)
A laminated film was obtained in the same manner as in Example 1, except that the relaxation treatment in the width direction was changed to 6%. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared to Example 1, the heat shrinkage rate was small at 0.3%, and the lift-suppressing property was slightly inferior.

(Comparative Examples 1 to 2)
A laminate film was obtained in the same manner as in Example 1, except that the thickness of the resin layer was changed as shown in Table 1. The properties of the obtained laminate film are shown in Tables 2 and 3. Compared with Example 1, the peeling properties due to heating were poor.

(Comparative Examples 3 to 4)
A laminated film was obtained in the same manner as in Example 1, except that the mass ratio of the release agent (A) and the resin or compound (B) was changed to the mass ratio shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared with Example 1, the initial epoxy resin peelability was too small and poor, and the peelability by heating was also poor.

(Comparative Example 5)
A laminated film was obtained in the same manner as in Example 27, except that the following long-chain alkyl acrylate compound (a-6) was used as the release agent (A). The properties of the obtained laminated film are shown in Tables 2 and 3. Compared with Example 27, the initial epoxy resin peelability was too high and poor, and the peelability by heating was also poor.
Long-chain alkyl acrylate compound (a-6):
In a temperature-controllable reactor equipped with a stirrer, a thermometer, and a condenser, 500 parts by mass of toluene, 80 parts by mass of stearyl methacrylate (alkyl chain carbon number 18), 15 parts by mass of methacrylic acid, 5 parts by mass of 2-hydroxyethyl methacrylate, and 1 part of azobisisobutyronitrile were placed in a dropping vessel, and a polymerization reaction was carried out by dropping the mixture over 4 hours at a reaction temperature of 85° C. Thereafter, the mixture was aged at the same temperature for 2 hours to complete the reaction, and the resulting compound was dissolved in water containing 5% by mass of isopropyl alcohol and 5% by mass of n-butyl cellosolve to obtain a solution containing a long-chain alkyl acrylate compound (a-6).

(Comparative Example 6)
A laminated film was obtained in the same manner as in Example 1, except that the following long-chain alkyl acrylate compound (a-6) was used as the release agent (A). The properties of the obtained laminated film are shown in Tables 2 and 3. Compared with Example 1, the initial epoxy resin peelability was too high and poor, and the peelability by heating was also poor.

(Comparative Example 7)
A laminated film was obtained in the same manner as in Example 1, except that the release agent (A) was not used. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared with Example 1, the water contact angle was smaller than 95°, and the peeling properties by heating were poor.

(Comparative Example 8)
A laminated film was obtained in the same manner as in Example 24, except that the mass ratio of the release agent (A) and the resin or compound (B) was changed to the mass ratio shown in Table 1. The properties of the obtained laminated film are shown in Tables 2 and 3. Compared with Example 24, the water contact angle was larger than 110°, the coating property of the epoxy resin was poor, and the peeling property by heating was also poor.

The laminated film of the present invention has excellent coatability of a surface layer represented by an epoxy resin and excellent peelability at a heating temperature, and can be suitably used as a process film for the production process of laminated ceramic electronic components, particularly interlayer insulating materials.

Claims (9)

A laminated film having a polyester film and a resin layer, the resin layer being present on at least one surface layer, the resin layer having a water contact angle of 95° or more and 110° or less, the initial tape peel strength of the laminated film being 0.5 N/50 mm or more and 4.0 N/50 mm or less, and the tape peel strength after heating at 100° C. for 30 minutes being 8.0 N/50 mm or more and 14.0 N/50 mm or less, the resin layer being a release agent (A) and at least one resin or compound selected from an epoxy resin, a melamine resin, an oxazoline compound, a carbodiimide compound, a polyester resin, an acrylic resin, and a urethane resin ( the resin layer has a static friction coefficient μs of 0.23 or more and 0.30 or less, and the content of particulate components in the resin layer is 3% by mass or more and 7% by mass or less with respect to the entire resin layer; and the laminated film is used for the purpose of providing a layer containing a hydrophilic resin on the surface of the resin layer and then peeling off the layer containing a hydrophilic resin. The laminate film according to claim 1, 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 fragment derived from polydimethylsiloxane to the peak intensity (K) of the fragment detected at maximum intensity is less than 0.01. The laminated film according to claim 1 or 2, wherein the elastic modulus P (MPa) measured from the surface side of the resin layer of the laminated film with an atomic force microscope (AFM) at an indentation depth of 10 nm is 200≦P≦2000. The laminated film according to any one of claims 1 to 3, wherein the resin layer has an average number of protrusions having a height of 25 nm or more of 0.1 pieces/μm2 ^{or more} and 2.0 pieces/μm2 or ^less . The laminate film according to any one of claims 1 to 4, wherein the resin having an alkyl group having 12 to 25 carbon atoms is a resin having a side chain of an alkyl group having 12 to 25 carbon atoms on a polymethylene main chain. 6. The laminate film according to claim 1, wherein the resin layer has a thickness of 50 nm or more and less than 200 nm. 7. The laminate film according to claim 1, wherein the resin layer has a surface free energy of 20 mN/m or more and 30 mN/m or less. The laminate film according to any one of claims 1 to 7 , which is used for applications in which a surface layer is provided on the surface of the resin layer, the surface layer is heated at 80 to 120 ° C, and then further heated at 150 to 180 ° C, and the surface layer is peeled off. A method for producing a laminated film according to any one of claims 1 to 8, comprising the steps of applying a coating composition containing a release agent ( A) to at least one side of a polyester film before completion of crystal orientation, stretching the polyester film in at least one axial direction, and then subjecting the polyester film to a heat treatment to complete the crystal orientation of the polyester film.