Release film

Abstract

This invention provides a release film made from environmentally friendly, non-fluorine-based materials that also exhibits excellent release properties even in high-temperature environments. [Solution] The release film comprises a release layer containing a silylated polyolefin resin and a polypropylene resin. When the total thickness of the release film is a, the thickness of the release layer is b, and the heat of fusion of the release film is α (J / g), then α × a / b > 40. The loss tangent tanδ of the release film is 0.25 or less at 140°C.

Description

[[Technical Field]]

[0001] The present invention relates to a release film. [[Background Art]]

[0002] Patent Document 1 discloses a release film using a polyolefin resin and a silylated polyolefin resin in a release layer thereof. [[Prior Art Documents]] [[Patent Documents]]

[0003] [[Patent Document 1]] Japanese Unexamined Patent Application Publication No. 2022-149440 [[Summary of the Invention]] [[Problems to be Solved by the Invention]]

[0004] Conventionally, PFAS (per- and polyfluoroalkyl substances, organic fluorine compounds) have often been used as a material for the release layer of release films, for reasons including excellent release properties against various materials. However, in recent years, regulations on PFAS have been promoted in consideration of the environment. In this regard, as disclosed in Patent Document 1, a non-fluorine-based material is sometimes used for the release layer. However, release films may be used in high-temperature environments depending on the application, and it is desirable to ensure stable release properties even in such severe environments. Conventional release films formed of non-fluorine-based materials still have room for improvement from the viewpoint of such heat resistance.

[0005] An object of the present invention is to provide a release film that is formed of an eco-friendly non-fluorine-based material and is excellent in release properties even in high-temperature environments. [[Means for Solving the Problems]]

[0006] Item 1. A release film comprising a release layer containing a silylated polyolefin-based resin and a polypropylene-based resin, Let a be the total thickness of the release film, b be the thickness of the release layer, and α (J / g) be the heat of crystalline fusion of the release film. Then α × a / b > 40. The loss tangent tanδ of the release film is 0.25 or less at 140°C. Release film.

[0007] Section 2. The release film is a single-layer film. The release film described in item 1.

[0008] Item 3. The release layer further comprises an adhesive layer and a base layer laminated in this order on one side of the release layer. The release film described in item 1.

[0009] Item 4. The thickness a is 30 μm or more. A release film as described in any of items 1 to 3.

[0010] Item 5. The content of the silylated polyolefin resin contained in the release layer is 5 wt% or more. A release film as described in any of items 1 to 4. [Effects of the Invention]

[0011] According to the present invention, a release film is provided that is made of an environmentally friendly non-fluorine material and exhibits excellent release properties even in high-temperature environments. [Brief explanation of the drawing]

[0012] [Figure 1] Cross-sectional view of the release film according to the first embodiment. [Figure 2] Cross-sectional view of the release film according to the second embodiment. [Modes for carrying out the invention]

[0013] Hereinafter, release films according to some embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and repeated description thereof will be omitted. The drawings are schematically drawn with appropriate omission or exaggeration of objects for ease of understanding.

[0014] [1. First Embodiment] [1-1. Configuration of Release Film] FIG. 1 shows a cross-sectional view of a release film 1 according to the first embodiment. In this example, the release film 1 has a three-layer structure, and includes a release layer 10, an adhesive layer 20, and a base layer 30 in this order in the thickness direction thereof. The release layer 10 is a surface layer and forms one surface (outermost surface) of the release film 1. The base layer 30 is also a surface layer and forms the other surface (outermost surface) of the release film 1. The adhesive layer 20 is an intermediate layer disposed between the release layer 10 and the base layer 30, and bonds the release layer 10 and the base layer 30. The adhesive layer 20 is laminated on one surface of the release layer 10, and the base layer 30 is laminated on the surface of the adhesive layer 20 opposite to the surface on which the release layer 10 is laminated. That is, the adhesive layer 20 and the base layer 30 are laminated in this order on one surface of the release layer 10.

[0015] The release film 1 is a PFAS-free film, and the entire release film 1 is made of an environmentally friendly non-fluorine-based material. That is, each of the release layer 10, the adhesive layer 20, and the base layer 30 is made of a non-fluorine-based material.

[0016] The release layer 10 contains a silylated polyolefin resin and a polypropylene resin, which are non-fluorine-based materials. Since polypropylene resins have a relatively high melting point, they can impart heat resistance to the release layer 10. A preferred example of the polypropylene resin contained in the release layer 10 is homopolypropylene.

[0017] From the viewpoint of ensuring releasability, the content of the silylated polyolefin resin contained in the release layer 10 is preferably 5 wt% or more, more preferably 7 wt% or more, still more preferably 9 wt% or more, and even more preferably 10 wt% or more. On the other hand, the content of the silylated polyolefin resin contained in the release layer 10 is preferably 25 wt% or less. The content of the polypropylene-based resin contained in the release layer 10 is preferably 75 wt% or more. The content of the polypropylene-based resin contained in the release layer 10 is preferably 95 wt% or less, more preferably 93 wt% or less, still more preferably 91 wt% or less, and even more preferably 90 wt% or less.

[0018] The release layer 10 may contain materials other than the silylated polyolefin-based resin and the polypropylene-based resin. However, the total content of the silylated polyolefin-based resin and the polypropylene-based resin contained in the release layer 10 is preferably 80 wt% or more, more preferably 85 wt% or more, still more preferably 90 wt% or more, even more preferably 95 wt% or more, and may be 100 wt%. For example, the release layer 10 may contain additives. Examples of additives include fillers, and in addition, ultraviolet absorbers, anti-blocking agents, heat stabilizers, antioxidants, light stabilizers, lubricants, antistatic agents, flame retardants, antibacterial agents, fluorescent brighteners and the like are also included. Examples of fillers include silica, polymethyl methacrylate (PMMA), talc, mica and the like. The content of the additives contained in the release layer 10 is preferably 10 wt% or less, more preferably 5 wt% or less, and still more preferably 3 wt% or less.

[0019] From the viewpoint of ensuring release properties, the water contact angle of the outermost surface of the release layer 10 is preferably 80° or more, more preferably 85° or more, even more preferably 90° or more, even more preferably 95° or more, and even more preferably 100° or more. From the viewpoint of ensuring release properties, the hexadecane contact angle of the outermost surface of the release layer 10 is preferably 15° or more, more preferably 16° or more, and even more preferably 17° or more.

[0020] The base layer 30 mainly consists of a non-fluorine-based resin material (typically a thermoplastic resin). In this specification, "main component" means the component that accounts for the largest weight relative to the total weight. The main component of the base layer 30 is preferably a polyamide resin. From the viewpoint of maintaining the strength of the release film 1, the polyamide resin content in the base layer 30 is preferably 50 wt% or more, more preferably 55 wt% or more, even more preferably 60 wt% or more, even more preferably 65 wt% or more, and may be 100 wt% (excluding additives described later).

[0021] The base layer 30 preferably further contains a resin compatible with the polyamide resin (hereinafter referred to as a polyamide-compatible resin) in addition to the polyamide resin. The polyamide-compatible resin contained in the base layer 30 is typically a non-fluorine-based resin material (typically a thermoplastic resin). The content of the polyamide-compatible resin contained in the base layer 30 is preferably 50 wt% or less, more preferably 45 wt% or less, even more preferably 40 wt% or less, and even more preferably 35 wt% or less.

[0022] Generally, polyamide resins tend to have high strength but low elongation (difficulty in stretching). Therefore, from the viewpoint of ensuring appropriate elongation by the release film 1, the content of polyamide resin in the base layer 30 is preferably 85 wt% or less, more preferably 80 wt% or less, and even more preferably 75 wt% or less. Furthermore, the content of polyamide-compatible resin in the base layer 30 is preferably 15 wt% or more, more preferably 20 wt% or more, and even more preferably 25 wt% or more.

[0023] The base layer 30 may contain additives in addition to the polyamide resin (and, if any, a polyamide-compatible resin). Examples of additives include ultraviolet absorbers, antiblocking agents, heat stabilizers, antioxidants, light stabilizers, lubricants, antistatic agents, flame retardants, antibacterial agents, and fluorescent whitening agents. The total content of the polyamide resin and polyamide-compatible resin in the base layer 30 is preferably 80 wt% or more, more preferably 85 wt% or more, even more preferably 90 wt% or more, even more preferably 95 wt% or more, and may be 100 wt%.

[0024] Examples of polyamide resins included in the base layer 30 include aliphatic polyamides, aromatic polyamides, amorphous polyamides, and polyamide elastomers. Examples of aliphatic polyamides include aliphatic nylon or its copolymers. A preferred example of a polyamide resin included in the base layer 30 is nylon 6.

[0025] Preferred examples of the polyamide-compatible resin included in the base layer 30 include adhesive resins, ethylene vinyl alcohol copolymer resins (EVOH), or both. Preferred examples of adhesive resins include acid-modified thermoplastic resins. Preferred examples of acid-modified thermoplastic resins include acid-modified polyolefin resins. Preferred examples of acid-modified polyolefin resins include acid-modified polypropylene resins, acid-modified linear low-density polyethylene (LLDPE), or both. When the polyamide-compatible resins exemplified herein are used in the base layer 30, the elongation of the release film 1 can be more effectively improved. The polyamide-compatible resin included in the base layer 30 may also be a polyamide resin.

[0026] The adhesive layer 20 mainly contains a non-fluorine-based resin material (typically a thermoplastic resin). From the viewpoint of improving adhesion to the base layer 30, it is preferable that the adhesive layer 20 contains common components with the resin used in the base layer 30. In particular, it is preferable that the adhesive layer 20 contains a resin common with the polyamide-compatible resin contained in the base layer 30. For example, if the base layer 30 contains an adhesive resin or EVOH, or both, as the polyamide-compatible resin, it is preferable that the adhesive layer 20 similarly contains an adhesive resin or EVOH, or both. The adhesive resin contained in the adhesive layer 20 is the same as that contained in the base layer 30, and a preferred example is an acid-modified thermoplastic resin, a particularly preferred example is an acid-modified polyolefin resin, and more specifically, an acid-modified polypropylene resin or acid-modified LLDPE, or both. Since the release layer 10 contains a polypropylene resin, it is preferable that the adhesive layer 20 contains an acid-modified polypropylene resin from the viewpoint of improving adhesion to the release layer 10. Furthermore, in this case, the heat resistance of the adhesive layer 20 may also be improved. The adhesive layer 20 may contain, in place of or in addition to, a polyamide-based resin common to the polyamide-based resin contained as a main component in the base layer 30, instead of a resin common to the polyamide-compatible resin contained in the base layer 30. The adhesive layer 20 is preferably mainly composed of a polyamide-based or polyolefin-based thermoplastic resin. Other examples of preferred resins to be included in the adhesive layer 20 include various elastomers, etc.

[0027] The overall thickness a of the release film 1 is preferably 30 μm or more, more preferably 35 μm or more, even more preferably 40 μm or more, and even more preferably 45 μm or more. Furthermore, the thickness a is preferably 250 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, and even more preferably 100 μm or less.

[0028] The thickness b of the release layer 10 is preferably 0.1 μm or more, more preferably 1 μm or more, and even more preferably 3 μm or more.

[0029] The thickness c of the adhesive layer 20 is preferably 0.1 μm or more, more preferably 1 μm or more, and even more preferably 3 μm or more.

[0030] The thickness d of the base layer 30 is preferably 10 μm or more, more preferably 15 μm or more, even more preferably 20 μm or more, and even more preferably 25 μm or more.

[0031] When the heat of fusion of the release film 1 is α (J / g), it is preferable that α × a / b > 40 (hereinafter referred to as condition 1) is satisfied. The heat of fusion α here is calculated based on the endothermic peak that appears near the melting point of the polypropylene resin in the DSC curve created using a differential scanning calorimeter. Therefore, the component that mainly contributes to the value of α is the polypropylene resin contained in the release layer 10. The a / b multiplied by α is a coefficient for converting α, which is the heat of fusion of the entire release film 1, to the heat of fusion of the release layer 10 when it has the same thickness as the entire release film 1.

[0032] The fulfillment of condition 1 means that the polypropylene resin contained in the release film 1 has a high degree of crystallinity. Therefore, when condition 1 is met, the release film 1 becomes stiffer, and the release film 1 can maintain sufficient strength and / or hardness. Furthermore, even in a high-temperature environment of approximately 130°C, for example, since this is lower than the melting point of the polypropylene resin (approximately 160°C), the release film 1 can maintain sufficient strength and / or hardness.

[0033] The loss tangent tanδ of the release film 1 is preferably 0.25 or less at 140°C (hereinafter referred to as condition 2). The satisfaction of condition 2 means that the release film 1 has a certain degree of elasticity even in a high-temperature environment of 140°C.

[0034] When conditions 1 and 2 are met, the release film 1 is given excellent release properties even in high-temperature environments (more specifically, even when exposed to a high-temperature environment of 130°C for 2 hours). This can be understood from the experimental results related to the examples described later.

[0035] The breaking strength of the release film 1 in terms of Machine Direction (MD) at room temperature is preferably 6 MPa or higher, and more preferably 30 MPa or higher. The breaking strength of the release film 1 in terms of Machine Direction (MD) at 150°C is preferably 2 MPa or higher, and more preferably 12 MPa or higher. The elongation at break of the release film 1 in terms of Machine Direction (MD) at room temperature is preferably 40% or higher, and more preferably 350% or higher. The elongation at break of the release film 1 in terms of Machine Direction (MD) at 150°C is preferably 400% or higher.

[0036] The release film 1 is manufactured, for example, by feeding the raw materials for the release layer 10, the adhesive layer 20, and the base layer 30 into an extruder and co-extruding them. Alternatively, the release film 1 can be constructed as a multilayer structure by forming each layer as a single layer and then laminating them.

[0037] The applications of the release film 1 are not particularly limited, but for example, the release film 1 can be used as a process film for semiconductor manufacturing processes including flexible printed circuit boards, or for thermosetting resin processing processes.

[0038] [1-2. Features] In the first embodiment, conditions 1 and 2 are met. As a result, the release film 1 is given excellent release properties even in high-temperature environments (more specifically, even when exposed to a high-temperature environment of 130°C for 2 hours). Furthermore, since the release film 1 is made of a non-fluorine-based material, it is also environmentally friendly.

[0039] [2. Second Embodiment] [2-1. Composition of the release film] Figure 2 shows a cross-sectional view of the release film 101 according to the second embodiment. As is clear from comparing Figure 1 and Figure 2, the release film 101 according to the second embodiment is a film obtained by omitting the adhesive layer 20 and the base layer 30 from the release film 1 according to the first embodiment, and is a single-layer film containing only the release layer 10. The structure of the release layer 10 included in the release film 101 according to the second embodiment is the same as in the first embodiment, except for the thickness b. Therefore, the release film 101 is also a PFAS-free film, and the entire film is made of environmentally friendly non-fluorine-based materials.

[0040] The thickness b of the release layer 10, i.e., the overall thickness a of the release film 101, is preferably 30 μm or more, more preferably 35 μm or more, even more preferably 40 μm or more, and still more preferably 45 μm or more. Furthermore, the thickness b is preferably 250 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, and still more preferably 100 μm or less.

[0041] In the second embodiment, it is also preferable that condition 1 is satisfied. That is, when the heat of crystalline melting of the release film 101 is α (J / g), it is preferable that α × a / b > 40. In the second embodiment, a / b = 1, so condition 1 means α > 40. In this case, as in the first embodiment, the degree of crystallinity of the polypropylene resin contained in the release layer 10 is high, and the release layer 10 can maintain sufficient strength and / or hardness even in a high-temperature environment of 130°C.

[0042] In the second embodiment, it is also preferable that condition 2 is satisfied. That is, it is preferable that the loss tangent tanδ of the release film 101 is 0.25 or less at 140°C. In this case, similar to the first embodiment, the elasticity of the release film 101 is ensured to a certain extent even in a high-temperature environment of 140°C.

[0043] When conditions 1 and 2 are met, the release film 101 is given excellent release properties even in high-temperature environments (more specifically, even when exposed to a high-temperature environment of 130°C for 2 hours). This can be understood from the experimental results related to the examples described later.

[0044] The breaking strength of the MD of the release film 101 at room temperature is preferably 6 MPa or higher. The breaking strength of the MD of the release film 101 at 150°C is preferably 2 MPa or higher. The breaking elongation of the MD of the release film 101 at room temperature is preferably 40% or higher. The breaking elongation of the MD of the release film 101 at 150°C is preferably 400% or higher, and more preferably 800% or higher.

[0045] The release film 101 is manufactured, for example, by feeding the raw materials for the release layer 10 into an extruder and performing extrusion molding.

[0046] The applications of the release film 101 are not particularly limited. For example, the release film 101 can be used in the same applications as the release film 1 exemplified in the first embodiment.

[0047] [2-2. Features] In the second embodiment, conditions 1 and 2 are also satisfied. As a result, the release film 101 is given excellent release properties even in high-temperature environments (more specifically, even when exposed to a high-temperature environment of 130°C for 2 hours). Furthermore, since the release film 101 is made of a non-fluorine-based material, it is also environmentally friendly.

[0048] [3. Variant] Although several embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications are possible without departing from its spirit. For example, the following modifications are possible.

[0049] The release film 1,101 according to the first and second embodiments had a three-layer structure or a single-layer structure, but is not limited to these examples. For example, in the release film 1 according to the first embodiment, a five-layer structure may be formed by laminating a further release layer via a further adhesive layer on the side of the base layer 30 opposite to the side where the adhesive layer 20 and release layer 10 are laminated. The further adhesive layer and release layer can be configured in the same way as the adhesive layer 20 and release layer 10 according to the first embodiment.

[0050] The overall thickness a of the 5-layer release film 1 is preferably 30 μm or more, more preferably 35 μm or more, even more preferably 40 μm or more, and even more preferably 45 μm or more, similar to the case of the 3-layer structure. Furthermore, the overall thickness a of the 5-layer release film 1 is preferably 250 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, and even more preferably 100 μm or less, similar to the case of the 3-layer structure. [Examples]

[0051] The following describes embodiments of the present invention. However, the present invention is not limited to the embodiments described below.

[0052] Release films for Examples 1-8 and Comparative Examples 1-4 were prepared. Examples 1-4 and Comparative Examples 1-4 were single-layer release films containing only a release layer, while Examples 5-8 were three-layer release films containing a release layer, adhesive layer, and base layer in that order. These release films were manufactured by feeding the raw materials for each layer shown in Tables 1-3 into an extruder in the weight ratios shown in Tables 1-3 and extruding from a die or co-extruding from a multilayer die. The thickness of each layer was as shown in Tables 1-3. Note that the silylated polyolefins 1-3, which are the raw materials for the release layer shown in Tables 1-3, are actually masterbatches of 30 wt% silylated polyolefin resin and 70 wt% polypropylene resin or polyethylene resin, as will be described later. Therefore, Tables 1-3 separately show the actual blending (weight ratio) of polypropylene resin and silylated polyolefin resin contained in the release layer.

[0053] [Table 1]

[0054] [Table 2]

[0055] [Table 3]

[0056] Polypropylene 1-5, polyethylene, LLDPE, silylated polyolefin 1-3, acid-modified olefin 1,2, and polyamide resins with the following properties were used.

[0057] <Polypropylene 1> Homopolypropylene, MFR: 3.0g / 10min (Test method JIS K7210), Tensile yield strength: 35MPa (Test method K7161), Tensile fracture nominal strain: >200% (Test method K7161), Load deflection temperature (0.45MPa): 106℃ (Test method K7191)

[0058] <Polypropylene 2> Homopolypropylene, MFR: 3.0g / 10min (Test method JIS K7210), Tensile yield strength: 32MPa (Test method K7161), Tensile fracture nominal strain: 170% (Test method K7161), Temperature of deflection under load (0.45MPa): 90℃ (Test method K7191)

[0059] <Polypropylene 3> Homopolypropylene, MFR: 7.0g / 10min (Test method JIS K7210), Tensile yield strength: 36MPa (Test method K7161), Tensile fracture nominal strain: 110% (Test method K7161), Temperature of deflection under load (0.45MPa): 103℃ (Test method K7191)

[0060] <Polypropylene 4> Homopolypropylene, MFR: 2.3g / 10min (Test method JIS K6921-2), Density: 0.9g / cm³ 3 (Test method JIS K6921-2), Tensile yield stress: 33 MPa (Test method K6921-2), Tensile fracture nominal strain: >300% (Test method K6921-2), Temperature of deflection under load (0.45 MPa): 100°C (Test method K6921-2)

[0061] <Polypropylene 5> Homopolypropylene, MFR: 4.5g / 10min, Tensile yield strength: 21MPa (Test method K7161 / 62), Tensile fracture nominal strain: >400% (Test method K7161), Load deflection temperature (0.45MPa): 61℃ (Test method K7191)

[0062] <Polyethylene> MFR: 5.0 g / 10 min (Test method JIS K7210), Density: 0.9 g / cm³ 3 (Test method JIS K7112), Tensile breaking strength: 14 MPa (Test method JIS K7113), Tensile elongation at break: 550% (Test method K7113), Vicat softening temperature: 90°C (Test method JIS K7206)

[0063] <lldpe> MFR: 2.0g / 10min (Test method JIS K7210), Density: 0.9g / cm³ 3 (Test method JIS K7112), Tensile breaking strength: 18 MPa (Test method JIS K7161 K7162), Tensile fracture nominal strain: 430% (Test method K7161 K7162), Vicat softening temperature: 102°C (Test method JIS K7206)

[0064] <Silylated Polyolefin 1> Exfora PP2000, manufactured by Mitsui Chemicals Fine Co., Ltd., contains 30% by weight of silylated polyolefin (olefin-silicone copolymer) and 70% by weight of homopolypropylene, density: 917 kg / m³, MFR: 20 g / 10 min, melting point: 125°C and 160°C.

[0065] <Silylated Polyolefin 2> Exfora PE3027, manufactured by Mitsui Chemicals Fine Co., Ltd., contains 30% by weight of silylated polyolefin (olefin-silicone copolymer) and 70% by weight of low-density polyethylene. Density: 932 kg / m³, MFR: 30 g / 10 min, melting point: 114°C and 122°C.

[0066] <Silylated Polyolefin 3> Exfora LL1513, manufactured by Mitsui Chemicals Fine Co., Ltd., contains 30% by weight of silylated polyolefin (olefin-silicone copolymer) and 70% by weight of metallocene-based linear low-density polyethylene. Density: 921 kg / m³, MFR: 15 g / 10 min, melting point: 102°C and 121°C.

[0067] <Acid-modified olefin 1> Acid-modified polypropylene, MFR: 7.7 g / 10 min (Test method ASTM D1238), Density: 0.90 g / cm³ 3 (Test method ASTM D1505), Breaking strength: 23 MPa (Test method ASTM D638), Elongation at break: 440% (Test method ASTM D638), Melting point: 140°C (Test method ASTM D3418)

[0068] <Acid-modified olefin 2> Acid-denatured LLDPE, MFR: 2.3 g / 10 min (Test method ASTM D1238), Density: 0.91 g / cm³ 3 (Test method ASTM D1505), Breaking strength: 25 MPa (Test method ASTM D638), Breaking elongation: 500% or more (Test method ASTM D638), Melting point: 120°C (Test method ASTM D3418)

[0069] <Polyamide resin> Nylon 6, relative viscosity: 3.37 (test method JIS K6810), density: 1.14 g / cm³ 3 (Test method DIN 53479), Breaking strength: 100 MPa (Test method ISO 527-3), Elongation at break: 410% (Test method ISO 527-3), Melting point: 220°C (Test method ISO T1357)

[0070] For each release film in Examples 1-8 and Comparative Examples 1-4, the heat of fusion α, loss tangent tanδ at 140°C, contact angle between water and hexadecane, and breaking strength and elongation at room temperature and 150°C were measured. The measurement method is as follows. In addition, the release properties were evaluated using the evaluation method described later. The measurement and evaluation results are shown in Tables 1-3. In the tables, the heat of fusion is shown as α × a / b.

[0071] <Heat of melting crystals> A 6 mg sample was taken from each release film. A differential scanning calorimeter (DSC60, Shimadzu Corporation) was used to create a DSC curve for each sample, and the heat of fusion α (J / g) was calculated based on the endothermic peak that appeared near the melting point of the polypropylene resin in the DSC curve. The measurement temperature was raised from 30°C to 200°C (for single-layer structures) or 250°C (for three-layer structures), then cooled to 50°C, and then raised again to 200°C (for single-layer structures) or 250°C (for three-layer structures). The heating and cooling rates were set to 10°C / min.

[0072] <Loss tangent> A strip-shaped sample piece measuring 40 mm in length (MD) x 10 mm in width (CD) was cut from each release film. For each sample piece, the storage modulus and loss modulus were measured in tensile deformation mode using a viscoelasticity analyzer (DMA7100, Hitachi High-Tech Science Corporation), and the loss tangent tanδ, which is the ratio of these modulosities at 140°C, was calculated. The measurement temperature was increased from 30°C to 150°C at a heating rate of 2°C / min. The frequency was set to 1 Hz.

[0073] <Method for measuring contact angle> The contact angle (°) was measured using a contact angle meter (KRUSS Drop Shape Analysis DSA1) with the measurement condition set to tangential method 1, for both cases where water and hexadecane were used as the reagent.

[0074] <Method for measuring fracture strength> The breaking strength (tensile breaking strength) was measured at room temperature and 150°C using a method compliant with JIS-K-6732. The sample size used for measuring the breaking strength (MPa) was 10 mm in width (TD; Transversal Direction) and 110 mm or more in length (MD) along the measurement direction (the length of the gauge mark on the sample was 40 mm ± 0 - 2). The thickness of the sample was measured at five equally spaced points along the length, and the average thickness was calculated based on the thicknesses of the five measured points. The specific measurements were performed using an Autograph (Shimadzu Precision Universal Tester Autograph AG-X 500N). The tensile speed was 200 mm / min, the chart speed was 200 mm / min, and the gripping distance was 40 mm. The strength at which the sample broke was defined as the breaking strength.

[0075] <Method for measuring elongation at break> The tensile elongation at break (MD) of the sample was measured at room temperature and 150°C using a method compliant with JIS-K-6732. The sample size used for measuring the % elongation at break was 10 mm in width (TD) and 110 mm or more in length (MD) along the measurement direction (the length of the gauge mark on the sample was 40 mm ± 0 - 2). The thickness of the sample was measured at five equally spaced points along the length, and the average thickness was calculated based on the thicknesses of the five measured points. The specific measurements were performed using an Autograph (Shimadzu Precision Universal Tester Autograph AG-X 500N). The tensile speed was 200 mm / min, the chart speed was 200 mm / min, and the gripping distance was 40 mm. The elongation at break of the sample was defined as the elongation at break.

[0076] <Method for evaluating mold release properties> A CFRP (carbon fiber reinforced plastic) prepreg sheet, made by weaving a bundle of 3000 carbon fiber filaments in a twill weave, was prepared. Samples were then sandwiched between the release films described in Examples 1-8 and Comparative Examples 1-4, and the samples were heat-cured in an autoclave under pressure at a temperature of 130°C for 2 hours. After cooling, the release films were manually peeled off the samples, and the release properties were evaluated sensorily. The evaluation was based on a three-point scale: ○ for good (peels off easily), △ for average, and × for damage.

[0077] <Consideration> Examples 1-8 all satisfied α×a / b>40 (Condition 1) and tanδ≦0.25 at 140°C (Condition 2), confirming that the release properties were good (○). On the other hand, Comparative Example 3 did not satisfy Condition 2, resulting in a release property of moderate (△). Comparative Example 4 did not satisfy Condition 1, resulting in a release property of moderate (△). In Comparative Examples 1 and 2, the resin mixed with the silylated polyolefin resin in the release layer was a polyethylene resin, not a polypropylene resin. Therefore, in Comparative Examples 1 and 2, the melting point of the release film was low, and the heat of fusion α, based on the endothermic peak that appears near the melting point of the polypropylene resin, could not be measured. Also, in Comparative Examples 1 and 2, the release film melted at 140°C, and tanδ at 140°C could not be measured. Therefore, in Comparative Examples 1 and 2, the release properties were poor (×). Based on the above, it was confirmed that satisfying conditions 1 and 2 results in good release properties in high-temperature environments (more specifically, when exposed to a high-temperature environment of 130°C for 2 hours). [Explanation of symbols]

[0078] 1,101 Release film 10 Release layer 20 Adhesive layer 30 Base Layer< / lldpe>

Claims

1. A release film comprising a release layer containing a silylated polyolefin resin and a polypropylene resin, Let a be the total thickness of the release film, b be the thickness of the release layer, and α (J / g) be the heat of crystalline fusion of the release film. Then α × a / b > 40. The loss tangent tanδ of the release film is 0.25 or less at 140°C. Release film.

2. The aforementioned release film is a single-layer film. The release film according to claim 1.

3. The release layer further comprises an adhesive layer and a base layer laminated in this order on one side of the release layer. The release film according to claim 1.

4. The thickness a is 30 μm or more. The release film according to any one of claims 1 to 3.

5. The content of the silylated polyolefin resin in the release layer is 5 wt% or more. The release film according to any one of claims 1 to 3.

Images