Release film and manufacturing method for molded products

Abstract

To provide a release film capable of combining good releasability, embeddability, and molded article appearance and suppressing waving.SOLUTION: A release film 10 includes a release layer 1 constituting a release surface 11, and a cushion layer 3 laminated on the release layer 1. The thickness of the release layer 1 is 1-10 μm. The thickness of the cushion layer 3 is 90-120 μm. The cushion layer 3 is composed of a resin composition containing a substance having a melting point measured by differential scanning calorimetry (DSC) of 80°C or lower and a substance having a melting point measured by DSC of 200°C or higher.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a release film and a molded article. [Background technology]

[0002] Release films are generally used when producing molded products or laminates made by bonding different materials. For example, when producing a flexible printed circuit board (hereinafter also referred to as "FPC") by placing a coverlay film (hereinafter also referred to as "CL film") via an adhesive on the circuit surface of a flexible film with exposed circuits (hereinafter also referred to as "circuit-exposed film") and then heat-pressing, a release film is placed between the coverlay film and the heat-press plate.

[0003] To date, release films made of various resins such as polymethylpentene resin have been proposed (Patent Document 1). For example, Patent Document 1 describes a release film that includes a surface coating, an adhesive layer, and a cushion layer, and the surface layer contains poly(4-methyl-1-methylpentene) resin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2006 / 120983 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, circuit boards have become increasingly miniaturized and thinner, and manufacturing methods such as the roll-to-roll (RtoR) method have also become more automated. Therefore, in order to more consistently obtain a good appearance for molded products, new properties are being sought for release films in addition to the various properties that have been required up until now, such as mold releasability and conformability. The present inventors conducted research to obtain a molded product with a better appearance and found that when there is a relatively large opening area where no circuit is arranged on the circuit side of a flexible printed circuit board, "waving" tends to occur in the coverlay film that covers the opening area. They then found that by using a release film with a specific configuration, waviness of the coverlay film can be suppressed even when there is a relatively large opening area, and a molded product with a good appearance can be obtained, thereby completing the present invention. [Means for solving the problem]

[0006] According to the present invention, A release film having a release layer constituting a release surface and a cushion layer laminated on the release layer, The release layer has a thickness of 1 to 10 μm, The thickness of the cushion layer is 90 to 120 μm, The release film is provided, wherein the cushion layer is made of a resin composition containing a substance having a melting point of 80°C or less as measured by differential scanning calorimetry (DSC) and a substance having a melting point of 200°C or more. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a release film that has good releasability, embeddability, and appearance of a molded product, and is also capable of suppressing waviness. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a longitudinal cross-sectional view of the release film according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are denoted by similar reference numerals, and their description will be omitted where appropriate. Furthermore, in this specification, the notation "a to b" in the description of a numerical range means a to b, unless otherwise specified. For example, "1 to 5 mass %" means "1 mass % to 5 mass %."

[0010] <Release film> FIG. 1 is a cross-sectional view of a release film according to this embodiment. 1, the release film 10 has a laminated structure in which a release layer 1, a cushion layer 3, and a release layer 2 are laminated in this order in the thickness direction. The release layer 1 is disposed on one side of the release film 10 and constitutes a release surface 11, and the release layer 2 is disposed on the other side of the release film 10 and constitutes a release surface 21. Although the example in which the release film 10 has release layers on both sides has been described with reference to FIG. 1, the release film is not limited to this.

[0011] In this embodiment, the release film 10 is placed so that the release layer 1 side is in contact with the object to be molded, which has circuits, etc. In other words, the surface that is in contact with the object to be molded is the release surface 11 of the release film 10, and the surface opposite to the surface that is in contact with the object to be molded is the release surface 21 of the release film 10.

[0012] Furthermore, the surface of the object to be molded before the release film 10 is placed is usually made of a material containing a thermosetting resin in a semi-cured state. The release film 10 is used by being placed on the surface of an object to be molded that is formed from a material containing the semi-cured thermosetting resin. Then, with the release film 10 placed on the surface of the object to be molded, a desired molded product can be obtained by performing a heat press.

[0013] In the release film 10 of this embodiment, the release layer 1 has a thickness of 1 to 10 μm, and the cushion layer 3 has a thickness of 90 to 120 μm. The cushion layer 3 is composed of a resin composition containing a substance having a melting point of 80°C or less, as measured by differential scanning calorimetry (DSC), and a substance having a melting point of 200°C or more. This prevents waviness from occurring in the coverlay film covering a relatively large opening, even if no circuit is arranged on the circuit surface of a flexible printed circuit board. As a result, the appearance of molded products obtained using the release film 10 can be improved. While the reason for this is unclear, it is presumed that the cushion layer 3 contains a substance having a melting point of 80°C or less and a substance having a melting point of 200°C or more. During heat pressing, the substance having a melting point of 80°C or less quickly softens, providing conformability and cushioning, while the substance having a melting point of 200°C or more maintains its hardness even during heat pressing, providing good releasability. It is believed that by controlling the thicknesses of the release layer 1 and the cushion layer 3, the balance of properties such as cushioning, elasticity, and embeddability obtained from the entire release film 10 effectively contributes to suppressing waviness.

[0014] Note that "waviness" in coverlay films is different from wrinkles and refers to undulations, undulations, smooth irregularities, etc. that can be observed visually. It also refers to an arithmetic mean height (Sa) of 0.05 μm or more. Sa can be measured in accordance with ISO 25178.

[0015] [Loop Stiffness] In an embodiment, the release film 10 preferably has a loop stiffness value in the MD direction measured under conditions of 23°C, 50% RH, a width of 10 mm, a circumference of 120 mm, and a pushing distance of 20 mm of 45 to 90 mN, more preferably 50 to 80 mN, and even more preferably 55 to 75 mN. By setting the loop stiffness value to the above lower limit or more, good hardness and rigidity can be obtained throughout the release film 10, and as a result, waviness can be effectively suppressed. On the other hand, by setting the loop stiffness value to the above upper limit or less, good embeddability can be easily obtained while maintaining good mold releasability.

[0016] [Elastic modulus, etc.] In this embodiment, the release film 10 preferably has a storage modulus at 150°C measured with a dynamic viscoelasticity measuring device (tensile mode, frequency 1 Hz, temperature rise rate 5°C / min) of 30 MPa or more and 70 MPa or less, and more preferably 40 MPa or more and 60 MPa or less. By setting the storage modulus at 150°C to the above lower limit or more, even when hot pressing is performed using the release film 10, good hardness and rigidity can be obtained throughout the release film 10, thereby improving the releasability. In addition, waviness can be effectively suppressed. On the other hand, by setting the storage modulus at 150° C. to the above upper limit or less, good releasability can be maintained when hot pressing is performed using the release film 10, while embedding properties can be easily obtained.

[0017] In this embodiment, the release film 10 preferably has a loss modulus at 150°C measured with a dynamic viscoelasticity measuring device (tensile mode, frequency 1 Hz, temperature rise rate 5°C / min) of 4 MPa or more and 20 MPa or less, more preferably 5 MPa or more and 15 MPa or less. By setting the loss modulus at 150°C to the above lower limit or more, good viscosity is obtained throughout the release film even when hot pressing is performed using the release film 10, so that embedding properties can be obtained while retaining releasability. In addition, waviness can be effectively suppressed. On the other hand, by making the loss modulus at 150°C equal to or less than the upper limit, good embedding properties during hot pressing can be maintained while mold releasability can be easily obtained.

[0018] In this embodiment, the release film 10 preferably has a tan δ of 0.05 or more and 0.3 or less, more preferably 0.1 or more and 0.2 or less, at 150°C, measured with a dynamic viscoelasticity measuring device (tensile mode, frequency 1 Hz, temperature rise rate 5°C / min). In addition, waviness can be effectively suppressed. By setting the tan δ at 150°C to the above lower limit or more, even when hot pressing is performed using the release film 10, appropriate viscoelasticity can be obtained throughout the release film, thereby improving the balance between releasability and embeddability. In addition, waviness can be effectively suppressed.

[0019] The loop stiffness, storage modulus, and loss modulus of the release film 10 of this embodiment can be adjusted by known methods, for example, by controlling the overall thickness of the release film 10, the thicknesses of the release layer 1 and the cushion layer 3, the combination of materials constituting the release layer 1 and the cushion layer 3, etc.

[0020] Thickness The overall thickness of the release film 10 is preferably 50 μm or more and 250 μm or less, more preferably 80 μm or more and 200 μm or less, and even more preferably 100 μm or more and 160 μm or less, which makes it possible to apply a press pressure to the release film 10 evenly and without unevenness when producing a molded product.

[0021] Each layer will be described in detail below.

[0022] Release layer 1 (first release layer) The release layer 1 is a layer that forms the surface (release surface 11) that comes into contact with the object to be molded when hot pressing is performed using the release film .

[0023] The release layer 1 is formed using a thermoplastic resin composition. Examples of thermoplastic resins include polyalkylene terephthalate resins such as polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), polytrimethylene terephthalate resin (PTT), and polyhexamethylene terephthalate resin (PHT), poly-4-methyl-1-pentene resin (TPX (registered trademark): hereinafter also referred to as polymethylpentene resin), syndiotactic polystyrene resin (SPS), polypropylene resin (PP), and copolymer resins copolymerized with other components. These may be used alone or in combination of two or more. Among these, from the viewpoint of improving the releasability of the release layer 1, it is preferable to use one or more selected from the group consisting of polymethylpentene resin, polybutylene terephthalate resin, syndiotactic polystyrene resin, and polypropylene resin. From the viewpoint of maintaining rigidity and obtaining good releasability even when the thickness of the release layer 1 is reduced, polymethylpentene resin or polybutylene terephthalate resin is more preferable.

[0024] The thermoplastic resin composition of the release layer 1 may contain, in addition to the above-mentioned thermoplastic resin, additives such as antioxidants, slip agents, antiblocking agents, antistatic agents, colorants such as dyes and pigments, stabilizers, impact resistance agents such as fluororesins and silicone rubber, and inorganic fillers such as titanium oxide, calcium carbonate, and talc.

[0025] In this embodiment, the release layer 1 may contain particles, which provides releasability and appropriate strength, and also prevents wrinkles and bubbles from forming in the release film 10, resulting in a good appearance. The average particle size d50 of the particles is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 8 μm or more, while the average particle size d50 of the particles is preferably 35 μm or less, more preferably 25 μm or less, and even more preferably 18 μm or less. By setting the average particle size d50 of the particles to the above lower limit or more, it is possible to improve the rigidity of the release film 10 and also improve the releasability from a surface-roughened FPC. On the other hand, by setting the average particle size d50 of the particles to the above upper limit or less, it is possible to achieve a good balance between releasability and conformability, and to produce a molded product with a good finished appearance.

[0026] From the viewpoint of improving the rigidity of the release film 10, the particles are preferably inorganic particles. Examples of inorganic particles include particles made of one or more of the following: silica (e.g., crystalline silica, amorphous silica, and fused silica), aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, zinc oxide, alumina, aluminum nitride, aluminum borate whisker, boron nitride, antimony oxide, E-glass, D-glass, S-glass, and zeolite. One type of inorganic particle may be used alone, or different types of particles may be used in combination. The inorganic particles may be surface-treated with a silane coupling agent or the like to improve adhesion to resins, or core-shell particles may be used, in which inorganic particles are treated with an organic coating to improve dispersibility. From the viewpoint of improving the rigidity of the release film, silica such as crystalline silica, amorphous silica, and fused silica is preferred, and spherical fused silica is more preferred.

[0027] The content of particles in the total amount of the release layer 1 is preferably 0.1% by mass to 30% by mass, more preferably 1% by mass to 20% by mass, and even more preferably 5% by mass to 15% by mass. By making the particle content of the release layer 1 equal to or greater than the above-mentioned lower limit, it becomes easier to obtain good release properties. On the other hand, by making the particle content of the release layer 1 equal to or less than the above-mentioned upper limit, it is possible to ensure appropriate strength of the release film 10, maintain good release properties, and reduce costs.

[0028] The thickness of the release layer 1 is 1 to 10 μm, and from the viewpoint of obtaining a suitable strength, it is preferably 2 μm or more, more preferably 3 μm or more, and particularly preferably 4 μm or more. On the other hand, from the viewpoint of ensuring releasability and improving embeddability in a molded product, the thickness of the release layer 1 is preferably 9 μm or less, more preferably 8 μm or less. Furthermore, by making the thickness of the release layer 1 equal to or greater than the above-mentioned lower limit, good releasability can be easily obtained, while by making the thickness of the release layer 1 equal to or less than the above-mentioned upper limit, good embedding and conformability can be easily obtained, and costs can be reduced. In addition, the waviness suppression effect can be stably obtained.

[0029] The thickness (μm) of the release layer 1 is 15% or less, preferably 12% or less, and more preferably 10% or less, of the total thickness (μm) of the release film 10. This facilitates heat transfer to the cushion layer 3 described below, facilitates rapid conformability by the cushion layer 3, and highly suppresses adhesive outflow. In addition, the waviness suppression effect is stably achieved. Meanwhile, the thickness (μm) of the release layer 1 is preferably 4% or more, more preferably 5% or more, of the total thickness of the release film 10. This allows the release film 10 to maintain good releasability.

[0030] ·Release layer 2 The release layer 2 is a layer that forms the surface (release surface 21) that comes into contact with the press hot plate when hot pressing is performed using the release film 10.

[0031] The release layer 2 is formed using a thermoplastic resin composition. The thermoplastic resin used in release layer 2 can be the same as that described above for release layer 1. The thermoplastic resins used in release layer 1 and release layer 2 may be the same or different. Furthermore, release layer 2 may be formed using the same material as release layer 1, or a different material.

[0032] In this embodiment, the release layer 2 may contain particles. The average particle size d50 of the particles is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 8 μm or more. On the other hand, the average particle size d50 of the particles is preferably 35 μm or less, more preferably 25 μm or less, and even more preferably 18 μm or less. By setting the average particle size d50 of the particles to the above lower limit or more, it is possible to improve the rigidity of the release film 10 and also improve the releasability from the hot plate during hot pressing. On the other hand, by setting the average particle size d50 of the particles to the above upper limit or less, it is possible to achieve a good balance between releasability and conformability, and to produce a molded product with a good finished appearance.

[0033] The content of particles in the total amount of the release layer 2 is preferably 0.1% by mass to 30% by mass, more preferably 1% by mass to 20% by mass, and even more preferably 5% by mass to 15% by mass. By setting the particle content of the release layer 2 to above the above lower limit, it becomes easier to obtain good release properties from the hot plate during heat pressing. On the other hand, by setting the particle content of the release layer 2 to below the above upper limit, it is possible to reduce costs while maintaining good release properties.

[0034] The particles contained in release layer 2 can be the same as the particles contained in release layer 1. The particles contained in release layer 1 and the particles contained in release layer 2 may be made of the same material or have the same particle size, or may be made of different materials or have different particle sizes.

[0035] From the viewpoint of obtaining a suitable strength, the thickness of the release layer 2 is preferably 10 μm or more, more preferably 15 μm or more. On the other hand, from the viewpoint of improving embeddability in a molded product, the thickness of the release layer 2 is preferably 60 μm or less, more preferably 50 μm or less.

[0036] Cushion layer 3 The cushion layer 3 is interposed between the release layer 1 and the release layer 2. The cushion layer 3 imparts good conformability and also provides the entire release film 10 with appropriate stiffness.

[0037] The cushion layer 3 is made of a resin composition containing a substance (a) having a melting point of 80°C or lower as measured by differential scanning calorimetry (DSC), and a substance (b) having a melting point of 200°C or higher. The resin composition constituting the cushion layer 3 may contain substances other than the above substances (a) and (b). In the release film 10 of this embodiment, the melting point of the substance contained in the cushion layer 3 can be measured, for example, by peeling the cushion layer 3 from the release film 10 and taking out only the cushion layer 3.

[0038] An example of the substance (a) having a melting point of 80°C or less is an ethylene-based copolymer. This allows the release film 10 to quickly conform to the circuit-exposed film and be pressure-bonded when hot-pressed using the release film 10. As a result, the release film 10 is pressure-bonded to the circuit-exposed film before the adhesive placed between the release film 10 and the circuit-exposed film flows and spreads due to hot-pressing, thereby preventing the adhesive from flowing out. This improves embeddability. In addition, the waviness suppression effect can be stably obtained.

[0039] Examples of the ethylene copolymer include one or more selected from ethylene-vinyl acetate copolymer (EVA), ethylene-vinyl alcohol copolymer (EVOH), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), ethylene-acrylate copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), ethylene cycloolefin copolymer (COC), and ionomer resin (ION). These may be used alone or in combination.

[0040] Examples of the substance (b) having a melting point of 200°C or higher include engineering plastic resins such as polymethylpentene resin, polybutylene terephthalate resin, and polyphenylene sulfide (PPS), each having a melting point of 200°C or higher. This allows the release film 10 to maintain a suitable rigidity when hot pressing is performed, effectively suppressing waviness. Furthermore, the release film 10 as a whole can maintain good releasability.

[0041] In the resin composition constituting the cushion layer 3 of this embodiment, the content of substance (a) is preferably 40% by mass or more and 80% by mass or less, and more preferably 50% by mass or more and 70% by mass or less, relative to the total amount of the cushion layer 3. By setting the content of substance (a) to the above lower limit or more, it is possible to prevent the adhesive from flowing out, even when hot pressing is performed using release film 10. On the other hand, by setting the content of substance (a) to the above upper limit or less, it is possible to prevent the cushion layer 3 itself from flowing out during hot pressing, and it is possible to maintain an appropriate strength. The content of the substance (b) relative to the total amount of the cushion layer 3 is preferably 10% by mass or more and 30% by mass or less, and more preferably 15% by mass or more and 25% by mass or less. By setting the content of substance (b) to the above lower limit or more, it is possible to effectively suppress waviness while maintaining releasability, while by setting the content of substance (b) to the above upper limit or less, it is possible to suppress waviness while improving conformability.

[0042] The cushion layer 3 of this embodiment may contain a material other than the above-mentioned materials (a) and (b). Examples include α-olefin polymers such as polyethylene and polypropylene; α-olefin copolymers having propylene, butene, pentene, hexene, methylpentene, etc. as polymer components; and engineering plastic resins, etc., with a melting point of 80°C or lower or 200°C or higher. These materials may be used alone or in combination of two or more. Among these, it is preferable that the cushion layer 3 contains an α-olefin polymer such as polypropylene, from the viewpoint of imparting appropriate strength and elasticity to the cushion layer 3 and achieving the effect of suppressing waviness.

[0043] Specific examples of resin compositions that constitute the cushion layer 3 include a mixture of ethylene and ethylene-methyl methacrylate copolymer (EMMA), a mixture of polypropylene (PP) and ethylene-methyl methacrylate copolymer (EMMA), a mixture of polybutylene terephthalate (PBT), polypropylene (PP) and ethylene-methyl methacrylate copolymer (EMMA), a mixture of polypropylene (PP), ethylene-methyl acrylate copolymer (EMA) and polymethylpentene resin, and a mixture of polypropylene (PP), ethylene-methacrylic acid copolymer (EMAA) and polymethylpentene resin. Among these, from the viewpoint of imparting appropriate strength and elasticity to the cushion layer 3 and maintaining good releasability, a resin composition containing at least polypropylene, poly-4-methyl-1-pentene resin, or polybutylene terephthalate (PBT) is preferred.

[0044] The resin composition of the cushion layer 3 may further contain a rubber component. Examples of the rubber component include thermoplastic elastomer materials such as styrene-based thermoplastic elastomers such as styrene-butadiene copolymer and styrene-isoprene copolymer, olefin-based thermoplastic elastomers, amide-based elastomers, and polyester-based elastomers, as well as rubber materials such as natural rubber, isoprene rubber, chloroprene rubber, and silicone rubber.

[0045] The resin composition of the cushion layer 3 may contain additives such as antioxidants, slip agents, antiblocking agents, antistatic agents, colorants such as dyes and pigments, stabilizers, impact resistance agents such as fluororesins and silicone rubber, and inorganic fillers such as titanium oxide, calcium carbonate, and talc.

[0046] The thickness (μm) of the cushion layer 3 is preferably 9 to 120 times, and more preferably 10 to 50 times, the thickness (μm) of the release layer 1. By setting the thickness of the cushion layer 3 to be equal to or greater than the above lower limit, the release film 10 can quickly obtain good cushioning properties, can suppress the adhesive from flowing out, and improves conformability. In addition, waviness can be easily suppressed. On the other hand, by setting the thickness of the cushion layer 3 to be equal to or less than the above upper limit, good releasability can be maintained, and the cushion layer 3 itself can be prevented from flowing out due to hot pressing. In addition, waviness can be stably suppressed.

[0047] The thickness of the cushion layer 3 is not less than 90 μm and not more than 120 μm. By setting the thickness of the cushion layer 3 to be equal to or greater than the above lower limit, the cushioning properties of the release film 10 can be quickly obtained, the adhesive can be prevented from flowing out, and the conformability can be improved. In addition, waviness can be easily suppressed. On the other hand, by setting the thickness of the cushion layer 3 to be equal to or less than the above upper limit, the releasability can be maintained good. In addition, waviness can be stably suppressed.

[0048] Examples of methods for forming the cushion layer 3 include known methods such as air-cooled or water-cooled inflation extrusion using the above-mentioned resin composition, and T-die extrusion.

[0049] <Method of manufacturing the release film 10> The release film 10 can be produced using known methods such as coextrusion, extrusion lamination, dry lamination, and inflation. The release film 10 may be produced by separately producing the release layer 1, the cushion layer 3, and the release layer 2 and then bonding them together using a laminator or the like. However, it is preferable to form the film by an air-cooled or water-cooled coextrusion inflation method or a coextrusion T-die method. Of these, the coextrusion T-die method is particularly preferable because it provides excellent control over the thickness of each layer. The release layer 1, the cushion layer 3, and the release layer 2 may be bonded together directly or via an adhesive layer.

[0050] <Molded product manufacturing method> Next, a method for manufacturing the molded product of this embodiment will be described. The method for manufacturing a molded product of this embodiment uses the release film 10, A step (step 1) of placing a release film 10 on an object so that the release surface 11 of the release film 19 faces the object; and a step (step 2) of performing a heat press on the object on which the release film 10 is placed, In step 1 of placing the release film 10, the surface of the object on which the release film 10 is to be placed is made of a material containing a thermosetting resin.

[0051] Furthermore, after step 1 of placing release film 10, a step (step 3) of placing a material on the release surface of the second release layer of release film 10 (the release surface of release layer 2) may be further included.

[0052] In this embodiment, step 1 can be performed using a known method. For example, a molded product can be produced by transporting the release film 10 using a roll-to-roll method. In the roll-to-roll method, the release film 10 is unwound from a roll and transported between an object and a heat press plate, and the object is heat-pressed and bonded to form a molded product. The film is then peeled off and rewound onto the roll. In this case, the angle at which the release film 10 is peeled off from the molded product tends to be low. Therefore, a greater force is applied to the release film 10, and therefore higher releasability is required. In contrast, in this embodiment, the release film 10 is used, which exhibits higher releasability. Even when using the roll-to-roll method, the balance between releasability and embeddability can be improved, and waviness can be suppressed, resulting in a molded product with a good appearance.

[0053] In this embodiment, the hot pressing temperature in step 2 can be a known method, and is, for example, 160°C to 200°C.

[0054] An example of using the method for manufacturing a molded product of this embodiment when manufacturing a flexible printed circuit board will be described. In this case, the release film 10 is used by being interposed between the coverlay and the press when the coverlay film is heated and pressed to adhere to the circuit formed on the flexible film in order to protect the circuit. Specifically, the release film 10 is used, for example, in a coverlay press lamination process, which is one of the manufacturing processes for flexible printed wiring boards. More specifically, the release film 10 is arranged to wrap the coverlay film so that the coverlay film is tightly attached to the uneven portions of the circuit pattern when the coverlay film is bonded to the circuit-exposed film, and is heated and pressed together with the circuit-exposed film and the coverlay film by a press. At this time, in order to improve cushioning properties, materials such as paper, rubber, a fluororesin sheet, glass paper, or a combination of these may be inserted between the release film 10 and the press, and then heated and pressed.

[0055] The release film 10 of this embodiment may also be used in the following manner to produce the above-mentioned molded article. First, the release surface 11 of the release layer 1 of the release film 10 according to the present embodiment is placed on the surface of an object formed of a material containing a thermosetting resin. Next, paper, rubber, a fluororesin sheet, glass paper, or a combination of these materials is placed on the release surface 21 of the release layer 2 of the release film 10. Thereafter, the object on which the release film 10 is placed is subjected to a press process in a mold. Here, the thermosetting resin may be in a semi-cured state or a cured state, but if it is in a semi-cured state, the effect of the release film 10 becomes even more pronounced. In particular, when the thermosetting resin is a resin composition containing an epoxy resin, it is preferable that the epoxy resin is in an intermediate stage of the curing reaction, i.e., in a B-stage state.

[0056] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations can also be adopted.

[0057] In this embodiment, the release film 10 has been described as having a laminated structure in which the release layer 1, the cushion layer 3, and the release layer 2 are laminated in this order in the thickness direction, but is not limited to this. For example, the release film may have a structure of four or more layers, such as four or five layers, including an adhesive layer, a gas barrier layer, etc. In this case, the adhesive layer and the gas barrier layer are not particularly limited, and known layers can be used. Below, examples of reference forms are given. 1. A release film having a release layer constituting a release surface and a cushion layer laminated on the release layer, The release layer has a thickness of 1 to 10 μm, The thickness of the cushion layer is 90 to 120 μm, A release film, wherein the cushion layer is composed of a resin composition containing a substance having a melting point of 80°C or less as measured by differential scanning calorimetry (DSC) and a substance having a melting point of 200°C or more. 2. The release film according to 1., A release film having a loop stiffness value in the MD direction of 45 to 90 mN measured under the conditions of 23°C, 50% RH, width 10 mm, circumference 120 mm, and push-in distance 20 mm. 3. The release film according to 1. or 2., The release film has a storage modulus of 30 MPa or more and 70 MPa or less at 150°C measured with a dynamic viscoelasticity measuring device (tensile mode, frequency 1 Hz, temperature rise rate 5°C / min). 4. A release film according to any one of 1. to 3., The release film has a loss modulus of 4 MPa or more and 20 MPa or less at 150°C measured with a dynamic viscoelasticity measuring device (tensile mode, frequency 1 Hz, temperature rise rate 5°C / min). 5. A release film according to any one of 1. to 4., The release film has a tan δ of 0.05 or more and 0.3 or less at 150° C. as measured with a dynamic viscoelasticity measuring device (tensile mode, frequency 1 Hz, temperature rise rate 5° C. / min). 6. The release film according to any one of 1. to 5., The release layer is a release film containing one or more resins selected from polyester resin, poly(4-methyl-1-pentene) resin, polyamide resin, and polypropylene resin. 7. A release film according to any one of 1. to 6., The cushion layer is a release film containing one or more materials selected from an ethylene copolymer, an α-olefin polymer, an α-olefin copolymer, an engineering plastic resin, and a polymethylpentene resin. 8. A release film according to any one of 1. to 7., The release film has a thickness of 50 to 250 μm. 9. The release film according to any one of 1. to 8., A release film used in the roll-to-roll method. 10. A step of placing the release film according to any one of 1. to 9. on the object so that the one release surface of the release film faces the object; A step of performing a heat press on the object on which the release film is placed; Including, A method for manufacturing a molded product, wherein in the step of placing the release film, the surface of the object on which the release film is placed is formed from a material containing a thermosetting resin. 11. A method for producing a molded product according to 10., comprising: The method for manufacturing a molded product further comprises, after the step of placing the release film, a step of placing a material on the release surface of the second release layer of the release film. 12. A method for producing a molded product according to 10. or 11., The method for manufacturing a molded article, wherein the molded article is a flexible circuit board. [Example]

[0058] EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these.

[0059] <Material> The following materials were used for the release film. (Release layer) TPX-1: Polymethylpentene resin "DX231" (softening temperature 179°C), manufactured by Mitsui Chemicals TPX-2: Polymethylpentene resin "RT31" (softening temperature 167°C), manufactured by Mitsui Chemicals PBT: Polybutylene terephthalate "1100-630S", manufactured by Chang Chun Petrochemical Co., Ltd. Fused silica: spherical, average particle size d50 is 11.7 μm, "SC10-32F", manufactured by Nippon Steel & Sumikin Materials Co., Ltd. (Cushion layer) Modified polyethylene resin: Ethylene-methyl acrylate copolymer (EMA) resin, "EB140F", manufactured by Japan Polyethylene Co., Ltd., melting point 73°C Low-density polyethylene (LDPE): "R500" manufactured by Ube Maruzen Polyethylene Co., Ltd., melting point 110°C Polypropylene resin: "E111G", manufactured by Prime Polymer, melting point 160°C TPX-1: Polymethylpentene resin "DX231", manufactured by Mitsui Chemicals TPX-2: Polymethylpentene resin "RT31", manufactured by Mitsui Chemicals

[0060] Example 1 As the thermoplastic resin composition for forming the first release layer, 90 parts by weight of TPX (registered trademark) and 10 parts by weight of fused silica were used. For the cushion layer, a resin composition containing 60 parts by weight of modified polyethylene resin, 20 parts by weight of polypropylene resin, and 20 parts by weight of TPX-2 was used. The thermoplastic resin composition used to form the second release layer (sub-release layer) was the same as that used to form the first release layer. Using each material, a first release layer, a cushion layer, and a second release layer were laminated in that order in the thickness direction using the extrusion T-die method, and each layer was molded to have the thickness (μm) shown in Table 1 to obtain a release film.

[0061] <Example 2> A release film was obtained in the same manner as in Example 1, except that PBT was used instead of TPX-1 for the release layer and cushion layer.

[0062] Example 3 A release film was obtained in the same manner as in Example 1, except that the layer thickness (μm) was changed to that shown in Table 1.

[0063] Example 4 A release film was obtained in the same manner as in Example 1, except that the layer thickness (μm) was changed to that shown in Table 1.

[0064] <Comparative Example 1> A release film was obtained in the same manner as in Example 1, except that the layer thickness (μm) was changed to that shown in Table 1.

[0065] <Comparative Example 2> A release film was obtained in the same manner as in Example 1, except that the layer thickness (μm) was changed to that shown in Table 1.

[0066] <Comparative Example 3> A release film was obtained in the same manner as in Example 1, except that the modified polyethylene resin "EB140F" for the cushion layer was changed to low-density polyethylene "R500."

[0067] <Comparative Example 4> A release film was obtained in the same manner as in Example 1, except that the layer thickness (μm) was changed to that shown in Table 1.

[0068] <Comparative Example 5> A release film was obtained in the same manner as in Example 1, except that the TPX-2 was changed to the polypropylene resin "E111G" for the cushion layer.

[0069] <Comparative Example 6> TPX-2 was used instead of TPX-1 for the release layer. For the cushion layer, a resin composition containing 60 parts by weight of modified polyethylene resin "EB140F," 10 parts by weight of polypropylene resin "E111G," and 30 parts by weight of TPX-2 was used. A release film was obtained in the same manner as in Example 1, except that the layer thickness (μm) was changed to that shown in Table 1.

[0070] The release films and molded articles obtained in the examples and comparative examples were subjected to the following measurements and evaluations. The results are shown in Table 1.

[0071] <Measurement> Measurement of melting point by differential scanning calorimetry (DSC): The temperature of the maximum endothermic peak in the DSC curve obtained using a DSC (differential scanning calorimeter, DSC6220 manufactured by SII Corporation) was taken as the melting point.

[0072] Average particle size d50 of particles (fused silica): Using a laser diffraction particle size analyzer (Malvern, Mastersizer 2000), particles were dispersed in water as the solvent and the particle size was measured. From the results, the particle size value at which the cumulative frequency was 50% was calculated as the average particle size d50. The unit is μm.

[0073] Storage modulus, loss modulus, Tanδ: A release film molded to a width of 4 mm and a length of 20 mm in the MD direction was measured using a dynamic viscoelasticity measuring device in tensile mode at a frequency of 1 Hz and a heating rate of 5°C / min, and the storage modulus (MPa), loss modulus (MPa), and Tan δ at 150°C were determined.

[0074] Loop Stiffness: Using a loop stiffness tester (manufactured by Toyo Seiki Co., Ltd.), the stiffness strength was measured over time under the conditions of test piece size: width 10 mm × 180 mm or width 15 mm × 180 mm (flow direction during film formation of the release film), loop length: 120 mm, and push-in amount: 20 mm, and the maximum value during that period was taken as the "value measured by the loop stiffness test" (mN / cm).

[0075] <Evaluation> Embeddability (adhesive seepage): First, a 1 mm square opening was created in a coverlay (CEAM0515) manufactured by Arisawa Manufacturing Co., Ltd. Next, a test specimen was prepared by temporarily attaching the coverlay with the opening to the surface of a copper-clad laminate for flexible wiring boards so that the adhesive-coated side was in contact with the surface. Next, the release film and the test specimen were overlapped so that the first release surface of the first release layer of the release film faced the coverlay-containing side of the test specimen. Then, a heat press treatment was performed under vacuum conditions of 150°C, 2 MPa, vacuuming for 20 seconds, and 2 minutes to obtain a molded product. The molded product thus obtained was observed for the shape of the adhesive coated on the surface of the cover tape oozing out from the outer edge of the opening (adhesive oozing shape) into the opening formed in the coverlay, and the embeddability was evaluated based on the following criteria. ⊚: The difference in unevenness of the adhesive seeping out shape was less than 40 μm. ◯: The difference in unevenness of the adhesive seeping shape was 40 μm or more and less than 70 μm. △: The difference in unevenness of the adhesive seeping shape was 70 μm or more and less than 100 μm. ×: The difference in unevenness of the adhesive seeping out shape was 100 μm or more.

[0076] Releasability (releasability of the release surface 11 of the first release layer): A test specimen was prepared by temporarily attaching a coverlay having an opening to the surface of an insulating substrate (FPC) on which electrical wiring with an L / S of 100 / 100 μm was formed, so that the adhesive-coated surface was in contact with the surface. Next, the release film and the test specimen were overlapped so that the first release surface of the first release layer of the release film faced the coverlay-containing surface of the test specimen. After that, a heat press treatment was performed under vacuum conditions at 150°C, 2 MPa, and vacuuming for 20 seconds and 2 minutes to obtain a molded product. Using a tensile tester (Force gauge AD-4932A-50N manufactured by A&D Corporation), the peel force between the release surface and the sample was measured in a 180° direction at a speed of approximately 1000 mm / min. The measurement was carried out immediately after pressing, and the releasability was evaluated based on the following criteria. The evaluation results are shown in Table 1. ◎: 0.5N or less ○: Over 0.5N and less than 1.0N ×: 1.0N or more

[0077] Waviness evaluation A three-layer flexible copper-clad laminate (FCCL) was prepared, with 15 mm x 15 mm etched areas (copper-free areas) formed in a grid pattern at 13 mm intervals, consisting of 12.5 μm thick polyimide and 18 μm thick copper foil. A test specimen was prepared by temporarily attaching the FCCL to a coverlay (CEAM0515) manufactured by Arisawa Seisakusho, which was made of a polyimide film and an epoxy resin adhesive layer. Next, the test piece was set at a predetermined position in a roll-to-roll press machine so that the coverlay film side was facing up. Next, while the release film was being transported at 300 mm / s using a roll-to-roll method, the release film was hot-pressed onto the test piece under conditions of 150°C, 140 seconds, and 11 MPa, and then the test piece and the release film were peeled off while being transported at 200 mm / s. Thereafter, the surface roughness Sa (μm) of the coverlay film attached to the punched portion of the copper foil was measured visually and with a Vertscan VS1000 (manufactured by Hitachi High-Tech Corporation), and evaluated according to the following criteria. The surface roughness was measured in accordance with ISO25178. ·standard ◯: No waviness. Sa value is less than 0.04 μm. △: Slight waviness is observed. Sa value is 0.04 μm or more and less than 0.05 μm. ×: Significant waviness is observed. Sa value is 0.05 μm or more.

[0078] Appearance wrinkles: A test specimen was prepared by temporarily attaching a coverlay with an opening to the surface of an insulating substrate (FPC) with 100 / 100 μm L / S electrical wiring, so that the adhesive-coated side was in contact with the surface. A release film was then applied to the test specimen using a roll-to-roll press under conditions of 150°C, 11 MPa, and 120 seconds. Immediately after applying pressure, the test specimen and the release film were peeled off while transporting at 200 mm / s. The surface of the test specimen was measured in accordance with "7.5.7.2 Wrinkles" of the JPCA standard. ◎: Wrinkle occurrence rate less than 1.0% ○: Wrinkle occurrence rate 1.0% or more, less than 2.0% ×: Wrinkle occurrence rate 2.0% or more

[0079] [Table 1] [Explanation of symbols]

[0080] 10 Release film 1 First release layer 2 Second release layer 3 Cushion layer 11 Release surface 21 Release surface

Claims

1. A release film having a release layer that forms a release surface and a cushion layer laminated on the release layer, The thickness of the release layer is 1 to 10 μm, The thickness of the cushion layer is 90 to 120 μm, the cushion layer is made of a resin composition containing a substance having a melting point of 80°C or less as measured by differential scanning calorimetry (DSC) and a substance having a melting point of 200°C or more; A release film having a loop stiffness value in the MD direction of 45 to 90 mN measured under the conditions of 23°C, 50% RH, width 10 mm, circumference 120 mm, and push-in distance 20 mm.

2. A release film having a release layer constituting a release surface and a cushion layer laminated on the release layer, The thickness of the release layer is 1 to 10 μm, The thickness of the cushion layer is 90 to 120 μm, the cushion layer is made of a resin composition containing a substance having a melting point of 80°C or less as measured by differential scanning calorimetry (DSC) and a substance having a melting point of 200°C or more; The release film has a storage modulus at 150°C measured with a dynamic viscoelasticity measuring device (tensile mode, frequency 1 Hz, temperature rise rate 5°C / min) of 30 MPa or more and 70 MPa or less.

3. A release film having a release layer constituting a release surface and a cushion layer laminated on the release layer, The thickness of the release layer is 1 to 10 μm, The thickness of the cushion layer is 90 to 120 μm, the cushion layer is made of a resin composition containing a substance having a melting point of 80°C or less as measured by differential scanning calorimetry (DSC) and a substance having a melting point of 200°C or more; The release film has a loss modulus of 4 MPa or more and 20 MPa or less at 150°C measured with a dynamic viscoelasticity measuring device (tensile mode, frequency 1 Hz, temperature rise rate 5°C / min).

4. A release film having a release layer constituting a release surface and a cushion layer laminated on the release layer, The thickness of the release layer is 1 to 10 μm, The thickness of the cushion layer is 90 to 120 μm, the cushion layer is made of a resin composition containing a substance having a melting point of 80°C or less as measured by differential scanning calorimetry (DSC) and a substance having a melting point of 200°C or more; The release film has a tan δ of 0.05 or more and 0.3 or less at 150° C. as measured with a dynamic viscoelasticity measuring device (tensile mode, frequency 1 Hz, temperature rise rate 5° C. / min).

5. A release film according to any one of claims 2 to 4, A release film having a loop stiffness value in the MD direction of 45 to 90 mN measured under the conditions of 23°C, 50% RH, width 10 mm, circumference 120 mm, and push-in distance 20 mm.

6. A release film according to any one of claims 1, 3 and 4, The release film has a storage modulus at 150°C measured with a dynamic viscoelasticity measuring device (tensile mode, frequency 1 Hz, temperature rise rate 5°C / min) of 30 MPa or more and 70 MPa or less.

7. A release film according to any one of claims 1, 2 and 4, The release film has a loss modulus of 4 MPa or more and 20 MPa or less at 150°C measured with a dynamic viscoelasticity measuring device (tensile mode, frequency 1 Hz, temperature rise rate 5°C / min).

8. A release film according to any one of claims 1 to 3, The release film has a tan δ of 0.05 or more and 0.3 or less at 150° C. as measured with a dynamic viscoelasticity measuring device (tensile mode, frequency 1 Hz, temperature rise rate 5° C. / min).

9. The release film according to any one of claims 1 to 8, The release layer comprises one or more resins selected from the group consisting of polyester resin, poly(4-methyl-1-pentene) resin, and polypropylene resin.

10. The release film according to any one of claims 1 to 9, The cushion layer is a release film containing one or more materials selected from the group consisting of ethylene copolymers, α-olefin polymers, α-olefin copolymers, engineering plastic resins, and polymethylpentene resins.

11. The release film according to any one of claims 1 to 10, The release film has a thickness of 50 to 250 μm.

12. The release film according to any one of claims 1 to 11, A release film used in the roll-to-roll method.

13. a step of placing the release film on an object so that the release surface of the release film according to any one of claims 1 to 12 faces the object; A step of performing a heat press on the object on which the release film is placed; Including, A method for manufacturing a molded product, wherein in the step of placing the release film, the surface of the object on which the release film is placed is formed from a material containing a thermosetting resin.

14. A method for producing a molded product according to claim 13, comprising: The release film further has a second release layer that forms a release surface on the surface opposite to the release surface, The method for manufacturing a molded product further comprises, after the step of placing the release film, a step of placing a material on the release surface of the second release layer of the release film.

15. A method for producing a molded product according to claim 13 or 14, The method for manufacturing a molded article, wherein the molded article is a flexible circuit board.

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