Release film, release film manufacturing method, and circuit board manufacturing method

Abstract

To prevent a resin from oozing from a specific resin layer by forming a film end into a specific structure.SOLUTION: A release film 10 includes a first resin layer 11, and a second resin layer 12 that is provided on at least one surface 11A side of the first resin layer 11 and has a composition different from the first resin layer 11, and has a coating part 14 coating an end face 11E of the first resin layer 11.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a release film, a method for producing the same, and a method for producing a circuit board. [Background technology]

[0002] Conventionally, a heat press process has been commonly used when manufacturing circuit boards such as FPCs (flexible printed circuit boards). In the heat press process, a release film is used to prevent the circuit board from adhering to the heat press plate. The release film is required to have properties such as heat resistance to withstand heat press molding, releasability from the FPC and heat press plate, non-contamination of copper circuits, and ease of disposal.

[0003] In recent years, the line spacing (L / S) of FPCs has become increasingly thinner, and as a result, the quality requirements for release films have also increased, with improved conformability being particularly sought after. To improve conformability, release films may have a multilayer structure, with one of the layers made of a highly flexible material. Specifically, it is common to provide a surface layer and an intermediate layer, with the intermediate layer made of a highly flexible material. It is also known that polyolefin resins such as polyethylene (PE) and ethylene-methyl methacrylate copolymer (EMMA) are used as highly flexible materials for intermediate layers and the like (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-98816 Summary of the Invention [Problem to be solved by the invention]

[0005] However, highly flexible resins such as PE and EMMA have low melting points and can melt or flow during pressing, causing them to seep out from the edges of the film. The exuded resin can adhere to and contaminate secondary materials such as circuit boards, press plates, and even cushioning materials placed inside the press plates.

[0006] Therefore, an object of the present invention is to provide a release film that can prevent exudation from a specific resin layer, such as an intermediate layer, that occurs during hot pressing. Another object of the present invention is to provide a method for producing a circuit board that is less susceptible to contamination. [Means for solving the problem]

[0007] As a result of extensive research, the present inventors have found that the above problems can be solved by forming a specific structure at the film edge in a release film having a multilayer structure, or by manufacturing a circuit board using a release film having a specific structure, and have completed the present invention as described below. That is, the present invention provides the following [1] to

[36] . [1] A first resin layer and a second resin layer provided on at least one surface of the first resin layer and having a composition different from that of the first resin layer, A release film having a covering portion that covers the end face of the first resin layer. [2] The release film according to the above [1], wherein the second resin layer forms the covering portion. [3] The second resin layer is provided on each of both sides of the first resin layer, The release film according to the above [2], wherein each of the second resin layers forms the covering portion. [4] The release film according to [2] or [3] above, wherein the second resin layer provided on the one surface and forming the covering portion is connected to the second resin layer on the other surface side of the first resin layer. [5] The second resin layer is provided on each of both sides of the first resin layer, The release film according to any one of the above [2] to [4], wherein each of the second resin layers has a protruding portion that protrudes outward beyond the end face of the first resin layer. [6] The release film according to the above [5], wherein the length of the protruding portion is greater than the average thickness of the second resin layer. [7] The release film according to [5] or [6] above, wherein the protruding portions are bonded to each other. [8] The release film according to the above [7], wherein the protruding portions have a pressure-bonded portion where they are pressed against each other and bonded together. [9] The release film according to the above [8], wherein the thickness of the pressure-bonded portion is smaller than the sum of the average thicknesses of the second resin layers.

[10] The release film according to the above [1], wherein the covering portion is formed by a covering member.

[11] The release film according to the above

[10] , wherein the covering member is a resin film.

[12] The release film according to the above

[10] , wherein the covering member is a sealant.

[13] The release film according to any one of the above [1] to

[12] , which has a polygonal planar shape and has covering portions on at least two sides thereof.

[14] The release film according to any one of the above [1] to

[13] , wherein the covering portion has an inclined surface.

[15] The release film according to any one of the above [1] to

[14] , further comprising a third resin layer provided between the first resin layer and the second resin layer.

[16] A device comprising: a first resin layer; and a second resin layer provided on at least one surface of the first resin layer and having a composition different from that of the first resin layer; The second resin layer has a protruding portion that protrudes outward beyond the end face of the first resin layer.

[17] The release film according to the above

[16] , wherein the second resin layer is provided on each of both sides of the first resin layer, and each of the second resin layers has a protruding portion.

[18] The release film according to the above

[17] , wherein the protruding length L1 of at least one of the protruding portions of the second resin layer is 5 mm or more.

[19] The protruding portions of the second resin layers have fixing portions fixed to each other, The release film according to the above

[17] or

[18] , which has a space between the fixing part and the first resin layer.

[20] The release film according to any one of the above items

[16] to

[19] , which has a polygonal planar shape and has covering portions on at least two sides thereof.

[21] The release film according to any one of the above items

[16] to

[20] , further comprising a third resin layer provided between the first resin layer and the second resin layer.

[22] A release film comprising a first resin layer and a second resin layer provided on at least one side of the first resin layer and having a composition different from that of the first resin layer, and having a folded portion.

[23] The release film according to the above

[22] , wherein the end face of the first resin layer faces inward relative to the outer edge of the release film.

[24] The release film according to the above

[22] or

[23] , wherein the folded length L2 of the folded portion of the second resin layer is 5 mm or more.

[25] The release film according to any one of the above items

[22] to

[24] , which has a polygonal planar shape and has covering portions on at least two sides thereof.

[26] The release film according to any one of the above items

[22] to

[25] , further comprising a third resin layer provided between the first resin layer and the second resin layer.

[27] A method for producing a release film, comprising a step of forming a covering portion that covers at least a portion of an end surface of a first resin layer of a laminate comprising a first resin layer and a second resin layer.

[28] A step of cutting the laminate, The method for producing a release film according to the above

[27] , wherein the cutting causes at least a part of the end face of the first resin layer to be covered with the second resin layer, thereby forming the covered portion.

[29] The method for producing a release film according to the above

[28] , wherein the cutting is carried out by at least one of push cutting, shear cutting, and melt cutting.

[30] The method for producing a release film according to the above

[27] , in which the covering portion is formed using a covering member.

[31] The second resin layer is provided with a protruding portion that protrudes outward beyond an end surface of the first resin layer, The method for producing a release film according to

[27] above, wherein the protruding portions are fixed to each other.

[32] The method for producing a release film according to the above

[31] , wherein the protruding portions are fixed to each other by at least one of stabilization, adhesive, fusion bonding, and pressure bonding.

[33] A method for producing a release film, comprising a step of folding back an end of a laminate comprising a first resin layer and a second resin layer inward to form a folded portion.

[34] The method for producing a release film according to the above

[33] , wherein the folded portion is fixed by at least one of stabilization, adhesive, fusion bonding, and pressure bonding.

[35] A method for producing a circuit board, comprising producing a circuit board using the release film according to any one of the above items [1] to

[26] .

[36] Preparing a first resin layer and a second resin layer having a different composition from the first resin layer; a lamination step of overlaying a first resin film having dimensions smaller than that of the second resin film on the second resin film, and further overlaying a second resin film having dimensions larger than that of the first resin film, A method for manufacturing a circuit board, wherein pressing is performed after the laminating step. [Effects of the Invention]

[0008] According to the present invention, by providing a specific structure to the film edge, it is possible to prevent resin from seeping out from a specific resin layer such as an intermediate layer, and it is also possible to provide a method for manufacturing a circuit board that does not cause contamination. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view showing an end structure of a release film according to a first embodiment of the present invention. [Figure 2] FIG. 4 is a schematic cross-sectional view showing an end structure of a release film according to a modified example of the first embodiment of the present invention. [Figure 3]1A to 1C are schematic views showing a method for producing a release film according to a first embodiment of the present invention. [Figure 4] FIG. 5 is a schematic cross-sectional view showing the end structure of a release film according to a second embodiment of the present invention. [Figure 5] 5A to 5C are schematic views showing a method for producing a release film according to a second embodiment of the present invention. [Figure 6] FIG. 10 is a schematic cross-sectional view showing the end structure of a release film according to a third embodiment of the present invention. [Figure 7] 5A to 5C are schematic diagrams illustrating a method for producing a release film according to a third embodiment of the present invention. [Figure 8] FIG. 10 is a schematic cross-sectional view showing the end structure of a release film according to a fourth embodiment of the present invention. [Figure 9] FIG. 10 is a schematic view showing a method for producing a release film according to a fourth embodiment of the present invention. [Figure 10] FIG. 10 is a schematic cross-sectional view showing the end structure of a release film according to a fifth embodiment of the present invention. [Figure 11] 10A to 10C are schematic views showing a method for producing a release film according to a fifth embodiment of the present invention. [Figure 12] FIG. 11 is a schematic cross-sectional view showing an end structure of a release film according to a modified example of the fifth embodiment of the present invention. [Figure 13] FIG. 10 is a schematic cross-sectional view showing the end structure of a release film according to a sixth embodiment of the present invention. [Figure 14] FIG. 11 is a schematic cross-sectional view showing the end structure of a release film according to a seventh embodiment of the present invention. [Figure 15] FIG. 13 is a schematic cross-sectional view showing the end structure of a release film according to an eighth embodiment of the present invention. [Figure 16] FIG. 13 is a schematic cross-sectional view showing an end structure according to a modified example of a release film according to an eighth embodiment of the present invention. [Figure 17] FIG. 13 is a schematic cross-sectional view showing the end structure of a release film according to a ninth embodiment of the present invention. [Figure 18]FIG. 4 is a schematic cross-sectional view showing an end structure of a release film according to a modified example of the first embodiment of the present invention. [Figure 19] FIG. 13 is a schematic cross-sectional view showing an end structure of a release film according to a modified example of the ninth embodiment of the present invention. [Figure 20] FIG. 4 is a schematic cross-sectional view showing an end structure of a release film according to a modified example of the first embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. First Embodiment FIG. 1 shows the end structure of a release film 10 according to a first embodiment of the present invention. As shown in FIG. 1, the release film 10 comprises a first resin layer 11 and second resin layers 12 and 13 provided on both sides 11A and 11B of the first resin layer 11, respectively. Each of the sides 11A and 11B constitutes a main surface of the first resin layer 11. The release film 10 is a laminate in which the second resin layer 12, the first resin layer 11, and the second resin layer 13 are integrated together. The release film 10 is a multilayer film in which the second resin layer 12, the first resin layer 11, and the second resin layer 13 are arranged in this order.

[0011] In the release film 10, the first resin layer 11 is an intermediate layer disposed between the second resin layers 12 and 13 and preferably has cushioning properties. That is, the first resin layer 11 preferably has flowable or flexible properties at the temperature at which pressing is performed. The second resin layers 12 and 13 are surface layers that form the outermost surfaces of the release film 10. The second resin layers 12 and 13 preferably have releasability, and as will be described later, for example, preferably have releasability from circuit boards, press plates, cushioning materials, etc. when manufacturing circuit boards. That is, preferably, the second resin layers 12 and 13 can be easily peeled from the object to be pressed after pressing. By providing the release film 10 with the first resin layer 11 in addition to the second resin layers 12 and 13, the release film 10 has good releasability from press plates, circuit boards, etc., while also having good conformability to the irregularities of the circuit board.

[0012] The resin constituting the first resin layer 11 is not particularly limited, but may include polyolefin-based resins. Examples of polyolefin-based resins include polyethylenes such as low-density polyethylene, linear low-density polyethylene, and ultra-high molecular weight polyethylene; polypropylenes such as homopolypropylene and random polypropylene; ethylene-acrylic monomer copolymers such as ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-acrylic acid copolymer; and ethylene-vinyl acetate copolymers. These may be used alone or in combination of two or more. Of these, low-density polyethylene, linear low-density polyethylene, ethylene-methyl methacrylate copolymer, and ethylene-vinyl acetate copolymer are preferred.

[0013] The resin constituting the first layer 11 may be a polyolefin-based resin alone, or may contain a resin other than a polyolefin-based resin, such as polystyrene, polyvinyl chloride, polyamide, polycarbonate, polysulfone, or polyester, as long as the object of the present invention is not impaired. However, the first layer 11 is mainly composed of a polyolefin-based resin, and the polyolefin-based resin may account for, for example, 50% by mass or more, and preferably 70% by mass or more, of the total resin components contained in the first layer 11.

[0014] The second resin layers 12 and 13 have a different composition from the first resin layer 11, and may be made of, for example, a different type of resin. Examples of resins used for the second resin layers 12 and 13 include polyester-based resins, polyolefin-based resins, and polystyrene-based resins. These may be used alone or in combination of two or more types. Of these, polyester-based resins are more preferred. Therefore, it is more preferable that the resin used for the first resin layer 11 is a polyolefin-based resin, and the resin used for the second resin layers 12 and 13 is a polyester-based resin. Furthermore, the resin used in the second resin layers 12 and 13 may be the same type of resin as the resin used in the first resin layer 11, and for example, the resins used in the first resin layer 11 and the second resin layers 12 and 13 may both be polyolefin-based resins. When the same type of resin is used, it is sufficient that at least one of the following characteristics is different: molecular weight, type of constituent monomer, or, in the case of a copolymer, molar ratio of constituent monomers. Furthermore, both the first resin layer 11 and the second resin layers 12 and 13 may contain two or more types of resins, and the blending ratio of each resin may be appropriately changed.

[0015] The polyester resin used in the second resin layer can be obtained, for example, by reacting a divalent acid or an ester-forming derivative thereof as the acid component with a diol component. The acid component is preferably an aromatic dicarboxylic acid or an ester-forming derivative thereof, and the polyester resin is preferably a crystalline aromatic polyester resin which uses an aromatic dicarboxylic acid as the acid component and has crystallinity.

[0016] Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalene dicarboxylic acid, and paraphenylenedicarboxylic acid. Examples of the ester-forming derivatives of aromatic dicarboxylic acids include ester-forming derivatives of the aromatic dicarboxylic acids, such as dimethyl terephthalate, dimethyl isophthalate, dimethyl orthophthalate, dimethyl naphthalene dicarboxylate, and dimethyl paraphenylenedicarboxylate. These may be used alone or in combination of two or more.

[0017] As the diol component, a low molecular weight aliphatic diol may be used, or a low molecular weight aliphatic diol and a high molecular weight diol may be used in combination. Examples of low molecular weight aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, etc. These may be used alone or in combination of two or more. Examples of the high molecular weight diol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, etc. These may be used alone or in combination of two or more.

[0018] Specific examples of crystalline aromatic polyester resins include polyethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, butanediol terephthalate-polytetramethylene glycol copolymer, butanediol terephthalate-polycaprolactone copolymer, etc. These may be used alone or in combination of two or more. Among these, polybutylene terephthalate is preferred because of its particularly excellent non-staining properties and crystallinity. The polyolefin resin used in the second resin layer may be a resin containing poly(4-methyl-1-pentene) as a main component or a resin containing an alicyclic olefin resin as a main component.The polystyrene resin may be a resin containing a polystyrene resin having a syndiotactic structure as a main component.

[0019] The resin used for the second resin layers 12, 13 may be composed only of a resin selected from the above-mentioned polyester-based resins, polyolefin-based resins, and polystyrene-based resins, but may also contain other thermoplastic resins and rubber components in addition to the resin selected from the above-mentioned polyester-based resins, polyolefin-based resins, and polystyrene-based resins, as long as the properties as a release layer are not impaired. Thermoplastic resins other than these are not particularly limited, but examples thereof include polyolefin, modified polyolefin, polystyrene, polyvinyl chloride, polyamide, polycarbonate, polysulfone, polyester, etc. Furthermore, rubber components are not particularly limited, but examples thereof include natural rubber, styrene-butadiene copolymer, polybutadiene, polyisoprene, acrylonitrile-butadiene copolymer, ethylene-propylene copolymer (EPM, EPDM), polychloroprene, butyl rubber, acrylic rubber, silicone rubber, urethane rubber, olefin-based thermoplastic elastomer, styrene-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, ester-based thermoplastic elastomer, amide-based thermoplastic elastomer, etc. These thermoplastic resins and rubber components may be used alone or in combination of two or more. However, the resin selected from the above-mentioned polyester-based resin, polyolefin-based resin, and polystyrene-based resin should be the main component in each of the second resin layers 12 and 13, and should account for, for example, 50% by mass or more, preferably 70% by mass or more, of the total resin components contained in the second resin layer. The second resin layers 12 and 13 may have different compositions, or may have the same composition, which makes it easier to produce the release film 10.

[0020] Furthermore, additives may be appropriately blended into the resins constituting the first resin layer 11 and the second resin layers 12 and 13. Examples of additives include fibers, inorganic fillers, flame retardants, ultraviolet absorbers, antistatic agents, inorganic substances, and salts of higher fatty acids.

[0021] To ensure its cushioning properties, the first resin layer 11 preferably has a lower elastic modulus in a high-temperature environment than the second resin layers 12 and 13. Specifically, the storage elastic modulus of the first resin layer 11 is preferably lower than each of the second resin layers 12 and 13. The storage elastic modulus is the storage elastic modulus at 180°C measured under the following conditions using a dynamic viscoelasticity measuring device (for example, DVA-200 manufactured by IT Measurement & Control Co., Ltd.). Measurement mode: Tensile Heating rate: 5℃ / min Data capture interval: 1℃ / min Measurement frequency 1Hz Distortion 0.1% Static / dynamic ratio 2 Minimum load 1cN Specifically, the storage modulus of the first resin layer 11 is 1.0×10 6 ~1.5×10 7 Pa is preferred. The storage modulus of the second resin layers 12 and 13 is, for example, 1.5×10 7 Pa, preferably 1.5 × 10 7 ~5.0×10 8 It is Pa.

[0022] The flow starting temperature of the first resin layer 11 is preferably lower than that of the second resin layers 12 and 13. The flow starting temperature means the temperature at which, when a sample of each layer alone (e.g., 25 mm × 25 mm) is placed on a hot plate or the like and heated from room temperature at about 10°C / min, the sample area increases by 10% or more due to flow. The flow initiation temperature of the first resin layer can be selected or adjusted depending on the heat press temperature, and is, for example, 80 to 200°C, but may be within a range of 80 to 120°C, 120 to 160°C, or 160 to 200°C. Similarly, the flow initiation temperature of the second resin layer can be selected or adjusted depending on the heat press temperature, and is, for example, 160 to 280°C, but may be within a range of 160 to 200°C, 200 to 240°C, or 240 to 280°C. The flow initiation temperature of the first resin layer is preferably at least 20°C lower than the temperature at which the heat pressing is performed, more preferably at least 30°C lower, even more preferably at least 40°C lower, and particularly preferably at least 50°C lower. The flow initiation temperature of the second resin layer is preferably 20°C or more higher than the temperature at which the heat pressing is performed, more preferably 30°C or more higher, even more preferably 40°C or more higher, and particularly preferably 50°C or more higher. The difference between the flow initiation temperature of the first resin layer and the flow initiation temperature of the second resin layer is preferably 40° C. or more, more preferably 60° C. or more, and even more preferably 80° C. or more.

[0023] From the viewpoint of ensuring appropriate cushioning properties and conformability to uneven surfaces, the thickness of the first resin layer 11 is preferably greater than the thickness of each of the second resin layers 12 and 13. The thickness of the first resin layer 11 is, for example, 5 to 200 μm, preferably 10 to 150 μm, and more preferably 20 to 100 μm. The thickness of each of the second resin layers 12 and 13 is preferably 1 to 100 μm, more preferably 5 to 50 μm, and even more preferably 10 to 20 μm. By making the thickness 1 μm or more, it is possible to prevent the release film from being torn during transportation or press molding. Furthermore, by making the thickness 100 μm or less, it is possible to prevent a decrease in the ability to follow irregularities during press molding. The thickness of each resin layer is an average thickness, and it is advisable to use, for example, the average thickness measured at 10 points other than the end of the release film.

[0024] 1, in this embodiment, one resin layer 12 of the pair of second resin layers 12, 13 forms a covering portion 14 that covers the end face 11E. In the embodiment shown in FIG. 1, the second resin layer 12 covers the first resin layer 11 from one surface 11A to the end face 11E. By providing the covering portion 14, the release film 10 can prevent the resin that constitutes the first resin layer 11 from seeping out from the end face 11E even when heated and pressurized during press processing, etc. In this specification, "coating" means that the end face or surface is covered, and does not necessarily have to be in contact with the object to be coated. Also, it does not necessarily have to be in close contact with the object to be coated, and there may be a space between the coating portion and the end face or surface.

[0025] 1, the second resin layer 12 preferably covers the entire end face 11E of the first resin layer 10 in cross section and is connected to the second resin layer 13 disposed on the other face 11B of the first resin layer 11. By connecting the pair of second resin layers 12, 13 to each other in this manner, it is possible to more effectively prevent the resin from seeping out from the end face. However, as shown in FIG. 2, the second resin layer 12 does not need to cover the entire end face 11E in cross section, and the second resin layers 12 and 13 do not need to be connected to each other. Furthermore, although the second resin layers 12 and 13 are in direct contact with each other in the configuration shown in FIG. 1, they do not necessarily have to be in direct contact with each other, and the second resin layers 12 and 13 may be connected via a member other than the first resin layer, such as a third resin layer described later. In this embodiment, as will be described later, end face 11E can be covered by plastically deforming second resin layer 12 so as to extend it. Therefore, the thickness of second resin layer 12 on end face 11E (i.e., the thickness of covering portion 14) may be thinner than the average thickness of second resin layer 12 on one surface 11A.

[0026] In the first embodiment, as shown in FIG. 1, the end of the first resin layer 11 may have an end surface 11E that is inclined with respect to the one surface 11A. When the end surface 11E is inclined with respect to the one surface 11A, the thickness of the first resin layer 11 decreases toward the tip 11F. That is, the thickness of the end of the first resin layer 11 may be smaller than the average thickness of the first resin layer described above. In other words, the tip 11F of the first resin layer 11 may have a tapered shape. The end surface 11E may be an inclined surface that is inclined at an obtuse angle with respect to the one surface 11A. Note that the end surface 11E does not need to be flat and may include a curved surface or the like as appropriate. Similarly, the covering portion 14 may have an inclined surface.

[0027] The release film according to the present embodiment may be in the form of a sheet or may be wound into a roll. Sheet-shaped release films are used, for example, when pressing sheet-shaped circuit boards or the like using a batch press or a quick press, as described below. Sheet-shaped release films are, for example, polygonal in plan view (polygonal in plan view), typically quadrilateral such as a rectangle or a square, but may also be circular. Furthermore, it is preferable that each end of the release film constituting each side (i.e., four sides in the case of a quadrilateral) is constituted by an end surface 11E having a covering portion 14 as described above. Sheet-shaped release films are generally pressed in their entirety by a press plate that is slightly larger than the release film. Therefore, by providing a covering portion 14 at each end constituting each side, it is possible to effectively prevent the first resin layer 11 from seeping out.

[0028] In addition, in the sheet-like release film, the entire end face of the first resin layer 11 does not necessarily need to be covered, and may be partially covered, but it is preferable that at least a certain percentage is covered. Specifically, when the entire outer edge of the release film is observed from a direction perpendicular to the thickness direction, if the area of the first resin layer covering the covered portion is "A1" and the area of the portion where the first resin layer is exposed is "B1", the coverage rate calculated by the following formula may be, for example, 30% or more, preferably 50% or more, more preferably 70% or more, and most preferably 100%. Coverage ratio = A1 / (A1+B1)×100

[0029] Similarly, in a sheet-like release film, not all of the ends constituting each side are necessarily configured with end faces 11E having the covering portion 14, and only the ends constituting some of the sides may be configured with end faces 11E having the covering portion 14. When the planar shape of the release film is polygonal, it is preferable that the covering portion 14 is provided on at least two sides. For example, in a quadrangle, it is preferable that the ends constituting opposing sides are configured with end faces 11E having the covering portion 14. Even with such a configuration, for example, when used in a manner in which the entire release film is not pressed, the seepage of the resin constituting the first resin layer 11 is effectively prevented.

[0030] On the other hand, it is preferable that both side edges of the roll-shaped release film are configured by end faces 11E having the covering portions 14. The roll-shaped release film is pressed while being transported, for example, by a roll-to-roll method, and at that time, exudation occurs from both side edges, so by providing the covering portions 14 at both side edges, exudation can be effectively prevented.

[0031] Furthermore, in the case of a roll-shaped release film, both side edges do not necessarily need to be completely covered with the covering portion, and may be partially covered with the covering portion, but it is preferable that at least a certain percentage is covered. Specifically, when both side edges of the release film are observed parallel to the TD direction, if the area of the first resin layer covered by the covering portion is "A2" and the area of the part where the first resin layer is exposed is "B2", the coverage rate calculated by the following formula may be, for example, 30% or more, preferably 50% or more, more preferably 70% or more, and most preferably 100%. Coverage ratio=A2 / (A2+B2)×100

[0032] However, roll-shaped release film may be cut out and used in sheet form. In such a case, after cutting, an appropriate covering portion may be provided on the ends other than the both end portions by any of the methods described below.

[0033] Next, an example of a method for producing a release film according to this embodiment will be described with reference to Figure 3. In the release film according to this embodiment, first, a laminate 16 consisting of a second resin layer 12, a first resin layer 11, and a second resin layer 13 is prepared. The method for producing the laminate 16 is not particularly limited, and examples include coextrusion methods such as a water-cooled or air-cooled coextrusion inflation method and a coextrusion T-die method, a method in which films for constituting each resin layer are produced and then the films are laminated by dry lamination, hot press molding, or the like, an extrusion lamination method, a solvent casting method, and the like.

[0034] Next, the laminate 16 is cut to obtain the release film 10. During the cutting, the second resin layer 12 is deformed to form the covering portion 14. Here, the cutting of the laminate 16 in this embodiment is preferably performed by a cutter blade 17 as shown in FIG. 3. The cutter blade 17 may have an inclined surface 17A at the tip, and for example, a Thomson blade may be used. In FIG. 3, the cutter blade 17 has inclined surfaces 17A on both sides of the tip, but the inclined surface 17A may be provided on only one side. When the laminate 16 supported by the base 18 is cut with a cutter blade from the surface on the side of the second resin layer 12, as shown in Fig. 3, the end surface 11E of the first resin layer 11 formed by the cut becomes an inclined surface that follows the shape of the inclined surface 17A, and the second resin layer 12 is stretched to cover the end surface 11E of the first resin layer 11A, thereby forming the covering portion 14. Note that the laminate can also be wound up after the covering portion 14 is formed to form a roll of release film. According to the above method, a release film having a covering portion at the end can be produced by a simple process, and therefore a release film with little exudation can be easily produced.

[0035] <Second embodiment> FIG. 4 shows the end structure of a release film according to a second embodiment. The second embodiment differs from the first embodiment in the structure of the end of the release film. Specifically, in the first embodiment, the end surface is covered by one of the pair of second resin layers, but in this embodiment, the end surface is covered by both of the pair of second resin layers. In other words, the pair of second resin layers forms a covering portion. In the following, the release film according to the second embodiment will be described in terms of differences from the first embodiment, and the points that will not be described are the same as those in the first embodiment.

[0036] In the second embodiment, the release film 20 has a first resin layer 21 and second resin layers 22 and 23 provided on both surfaces 21A and 21B of the first resin layer 21, respectively. A covering portion 24 is provided on an end surface 21E of the first resin layer 21. In the embodiment shown in FIG. 4, the end surface 21E has an inclined surface 21G and an inclined surface 21H. Here, in this embodiment, the covering portion 24 is formed by both the second resin layers 22 and 23. That is, each of the second resin layers 22 and 23 covers the end surface of the first resin layer 21. In the embodiment shown in FIG. 4, the second resin layer 22 covers the first resin layer 21 from one surface 21A to the end surface 21E. Similarly, the second resin layer 23 covers the first resin layer 21 from the other surface 21B to the end surface 21E. The first and second resin layers 22 and 23 are preferably connected to each other on the end surface 21E. In this embodiment, the release film 20 is provided with the covering portion 24, which prevents the resin constituting the first resin layer 21 from seeping out from the end surface 21E even when heated and pressurized during hot press processing, etc.

[0037] The pair of second resin layers 22, 23 are disposed so as to be connected to each other on end face 21E, and end face 21E is entirely covered with covering portion 24 in cross section as shown in FIG. Also in this embodiment, as will be described later, end face 21E can be covered by plastically deforming second resin layers 22 and 23 so as to extend them. Therefore, the thickness of each of second resin layers 22 and 23 on end face 21E may be thinner than the average thickness of each of second resin layers 22 and 23 on one surface 21A and the other surface 21B.

[0038] In the second embodiment, the end of the first resin layer 11 also has a tapered shape, but the tip 21F is located at a position between both surfaces 21A and 21B in the thickness direction of the release film 30, and the tip 21F is preferably connected at an obtuse angle to each of the surfaces 21A and 21B via the inclined surfaces 21G and 21H that constitute the end surface 21E. Note that the inclined surfaces 21G and 21H do not need to be flat, and may include curved surfaces as appropriate.

[0039] Next, an example of a method for producing a release film according to this embodiment will be described. In the release film according to this embodiment, a laminate 26 consisting of a second resin layer 22, a first resin layer 21, and a second resin layer 23 is first prepared. The laminate 26 is then cut to obtain the release film 20, and the second resin layers 22 and 23 form the covering portion 24 described above. Cutting of the laminate 20 according to this embodiment is preferably performed by press cutting using a shear blade 27, as shown in FIG. 5 . The shear blade 27 generally comprises an upper blade 27A and a lower blade 27B. The upper blade 27A and the lower blade 27B are brought close to each other in the thickness direction, and the laminate 26 is cut by applying a shear force. This cutting process results in a tapered end surface 21E of the first resin layer 21, and the second resin layers 22 and 23 are deformed so as to extend along the shape of the end surface 21E, thereby forming a covering portion 24 that covers the end surface 21E, as shown in FIG. 4 .

[0040] <Third embodiment> When the end faces of the first resin layer are covered with a pair of second resin layers as described above, the configuration is not limited to that of the second embodiment described above, and may have various shapes, for example, a configuration like the release film 30 according to the third embodiment shown in Fig. 6. Note that, as with the second embodiment, the release film according to the third embodiment below will be described in terms of differences from the second embodiment, and the points where description will be omitted are the same as those in the second embodiment.

[0041] In the release film 30 according to the third embodiment, as shown in FIG. 6, the second resin layers 32 and 33 protrude outward from the end surface 31E. That is, the second resin layers 32 and 33 have protruding portions 32F and 33F, respectively. The protruding portions of the second resin layers make it more difficult for the first resin layer 31 to seep out of the release film. The lengths of the protruding portions 32F and 33F are preferably greater than the average thickness of the second resin layers 32 and 33, each having the protruding portions 32F and 33F. Furthermore, the protruding portions 32F and 33F are preferably bonded to each other. The adhesion of the protruding portions can more effectively prevent seepage. Examples of bonding methods include thermal fusion, chemical welding, and bonding with an adhesive. In the embodiment shown in FIG. 6, the end surface 31E has inclined surfaces 31G and 31H.

[0042] In the production of the release film 30 according to this embodiment, a laminate 36 including a second resin layer 32, a first resin layer 31, and a second resin layer 33 is first prepared. Next, the laminate 36 is cut to obtain the release film 30, and the covering portion 34 is formed by this cutting. Here, as shown in FIG. 7, the cutting of the laminate 30 according to this embodiment is preferably performed by melt cutting using a heated blade 37. The second resin layers 32 and 33 are stretched while being melted, thereby covering the end surface 31E and forming the covering portion 34. Furthermore, when melt cut, the second resin layers 32 and 33 are fused to each other on the end surface 31E. Furthermore, because the end of the first resin layer 31 is melted and stretched, the tip shape becomes more elongated. Not only the first resin layer 31 but also the second resin layers 32 and 33 are cut while being melted, and are therefore easily stretched, and the stretched second resin layers 32 and 33 can cover the end surface 31E of the first resin layer 31. The heating blade 37 should be heated to a temperature at least sufficient to melt the second resin layers 32 and 33, for example, to a temperature about 30° C. higher than the melting point of the resin used, preferably 5 to 20° C. higher. The heating blade 37 is a cutting blade, and specifically, a cutting blade having an inclined surface 37A at the tip is shown, but it may be something other than a cutting blade.

[0043] In the above first to third embodiments, a configuration has been shown in which a covering portion is formed on the end surface of the first resin layer by push cutting, shear cutting, or melt cutting, but the covering portion may also be formed by a cutting method other than these. In the shear cutting and melt cutting methods shown in the second and third embodiments, the covering portion is formed by a pair of second resin layers provided on both sides of the first resin layer. However, even when forming the covering portion by these cutting methods, the covering portion may be formed by only one of the second resin layers, as in the first embodiment, by appropriately selecting the type of resin constituting the second resin layer or the cutting conditions. Furthermore, in the second and third embodiments, the second resin layers 22, 23 (or 32, 33) are shown connected to each other on the end face 21E (or 31E), but as in the modified example of the first embodiment (see FIG. 2), they may not be connected to each other, and there may be a portion of the end face that is not covered by the covering portion. Also, the second resin layers 22, 23 (or 32, 33) do not have to be in direct contact with each other, and may be connected via a member other than the first resin layer, such as a third resin layer described below. Also, there may be a space between the covering portion and the end face.

[0044] Furthermore, the end faces 11E, 21E, and 31E of the first to third embodiments do not necessarily have to have a tapered shape. For example, in the second embodiment, the two inclined surfaces 21G and 21H constituting the end face 21E are connected to the one surface 21A and the other surface 21B at an obtuse angle, but these inclined surfaces 21G and 21H may be connected to the one surface 21A and the other surface 21B at an acute angle. That is, the end face 21E of the first resin layer 21 may have an inwardly recessed shape, and accordingly, the covering portion 24 may also have an inwardly recessed shape. An end face of this type can be formed, for example, by pressing a shear blade against the end face of the first resin layer when cutting the release film. Furthermore, forming the end face of the first resin layer into a concave shape is also applicable when the covering portion is formed by only one of the second resin layers 12, as in the first embodiment, and in that case too, the concave shape can be formed by pressing the cutting blade against the end face of the first resin layer when cutting the release film.

[0045] Furthermore, although the end faces 11E, 21E, and 31E in the first to third embodiments have been shown to have inclined surfaces, they do not necessarily have to have inclined surfaces, and may instead be formed, for example, by vertical surfaces parallel to the thickness direction. Furthermore, they may also be a combination of vertical surfaces and inclined surfaces, or may have other shapes.

[0046] <Fourth embodiment> In the first to third embodiments described above, the covering portion is formed by cutting when producing the release film, but the covering portion may be formed by a method other than cutting. A specific example thereof will be described as the fourth embodiment with reference to Fig. 8. Hereinafter, the release film according to the fourth embodiment will be described in terms of differences from the second embodiment, and the points that will not be described are the same as those in the second embodiment.

[0047] In this embodiment, the release film 40 also includes a first resin layer 41 and second resin layers 42 and 43 provided on both surfaces 41A and 41B of the first resin layer 41. In this embodiment, similar to the third embodiment, the second resin layers 42 and 43 have protruding portions 42F and 43F, respectively. The release film 40 has a pressure-bonded portion 48 formed by pressing and bonding the protruding portions 42F and 43F together. The thickness of the pressure-bonded portion 48 is reduced by compression deformation, and is therefore smaller (thinner) than the sum of the average thicknesses of the second resin layers 42 and 43.

[0048] In the present embodiment, the release film 40 is provided with the covering portion 44, which prevents the resin constituting the first resin layer 41 from seeping out from the end surface 41E even when heated and pressurized during hot press processing, etc. Furthermore, since the second resin layers 42 and 43 are bonded to each other, seepage can be prevented more reliably.

[0049] Next, an example of a method for producing the release film 40 of this embodiment will be described with reference to Fig. 9. In this embodiment, as in the above-described embodiments, as shown in Fig. 9, a laminate 46 is prepared in which a second resin layer 43, a first resin layer 41, and a second resin layer 42 are laminated in this order. In this case, in the laminate 46, the first resin layer 41 is provided intermittently, and between the second resin layers 42 and 43, there is provided a region 46A where the first resin layer 41 is not provided. That is, in the laminate 46, it is preferable that a plurality of first resin layers 41 are arranged along the surface direction. Next, in the region 46A where the first resin layer 41 is not provided, the first and second resin layers 42, 43 are pressed together so as to come into contact with each other, and are then heated or the like to be pressure-bonded, thereby forming the pressure-bonded portion 48, which also forms the covering portion 44. Furthermore, through the above steps, the protruding portions 42F, 43F are provided, and the protruding portions 42F, 43F are fixed to each other. Thereafter, the laminate 46 may be cut along the pressure-bonded portions 48, etc., as necessary, to obtain a plurality of release films 40. Note that the cutting lines are shown by dotted lines in Fig. 9 .

[0050] <Fifth embodiment> In the above-described fourth embodiment, the first resin layer is not provided in the pressure-bonding portion, but the first resin layer may be provided in the pressure-bonding portion. A specific example thereof will be described as the fifth embodiment with reference to FIG. 10. In the following description, the differences between the release film according to the fifth embodiment and the fourth embodiment will be described, and the points that will not be described are the same as those in the fourth embodiment.

[0051] In this embodiment, the release film 50 also includes a first resin layer 51 and second resin layers 52 and 53 provided on both surfaces 51A and 51B of the first resin layer 51. In this embodiment, the first resin layer 51 has a protruding portion 51F, similar to the second resin layers 52 and 53. The protruding portions 51F, 52F, and 53F have a pressure-bonded portion 58 that is pressed against and bonded to each other. The pressure-bonded portion 58 forms a part of the covering portion 54. The thickness of the pressure-bonded portion 58 is reduced by compression deformation, and is therefore thinner than the sum of the average thicknesses of the second resin layers 52 and 53 and the first resin layer 51.

[0052] With the above configuration, the end surface 51E of the first resin layer 51 is covered with the covering portion 54. Therefore, in this embodiment as well, the resin constituting the first resin layer 51 is prevented from seeping out from the end surface 51E of the first resin layer 51.

[0053] Next, an example of a method for producing the release film 50 of this embodiment will be described with reference to FIG. 11 . In this embodiment, as shown in FIG. 11 , a laminate 56 is prepared in which a second resin layer 53, a first resin layer 51, and a second resin layer 52 are laminated in this order, as in the first embodiment described above. Next, the laminate 56 is partially compressed and deformed by a pressure-bonding means 57 such as a heated embossing roller, so that the first resin layer 51 and the second resin layers 52 and 53 are partially pressure-bonded to form a pressure-bonded portion 58. Thereafter, the laminate 56 is preferably cut along the pressure-bonded portion 58 or the like to obtain the release film 50. Note that the cutting line used when producing the release film shown in FIG. 10 is indicated by a dotted line. Note that the cutting position when producing the release film 50 does not have to be on the pressure-bonded portion 58, and may be the position indicated by the dashed-dotted line in FIG. 11 . A cross-sectional view of the release film 50 obtained in this case is shown in FIG. 12 . This embodiment also makes it possible to prevent the first resin layer 51 from bleeding out. Furthermore, in this manufacturing method, it is not necessary to align the cutting position with the pressure-bonding portion 58, which makes manufacturing even easier. For example, when embossing and pressure-bonding are performed while the laminate 56 is being transported in a roll-to-roll manner, it is also possible to perform cutting in parallel with the embossing.

[0054] In the fourth and fifth embodiments (see FIGS. 8 to 12), the end faces 41E, 51E of the first resin layers 41, 51 are preferably deformed, for example, during pressure bonding, to have inclined faces 41G, 41H, 51G, 51H. However, end faces 41E, 51E do not necessarily have to have inclined faces 41G, 41H, 51G, 51H, and may be formed, for example, by vertical faces (faces parallel to the thickness direction). In cases where they are formed by vertical faces, there may be a space between the end faces and the covering portion formed by pressing the second resin layer. However, even if there is a space, it is possible to appropriately prevent the resin constituting the first resin layer from seeping out.

[0055] Furthermore, in the above-described fourth embodiment (see FIG. 9), the second and third resin layers 42, 43 are bonded to each other by pressure bonding, but they may be configured in a manner other than pressure bonding, and may be bonded by fusion bonding or using an adhesive or the like. Similarly, in the above-mentioned fifth embodiment (see FIG. 11), the first resin layer 51 and the second and third resin layers 52, 53 are bonded to each other by pressure bonding, but they may also be bonded in a manner other than pressure bonding, for example, by fusion bonding.

[0056] Sixth Embodiment In the first to fifth embodiments described above, the covering portion covering the end face of the first resin layer is formed by the second resin layer, but the covering portion may be formed by a covering member that is a member other than the second resin layer. Such a configuration will be described below as release films 60 and 70 according to sixth and seventh embodiments. In the following, first, the differences between the release film according to the sixth embodiment and the first embodiment will be explained with reference to FIG. 13, but the points that will not be explained are the same as those in the first embodiment. Furthermore, the term "another member" means a member separate from the second resin layer when the laminate constituting the release film is composed of first and second resin layers, but when other resin layers other than the first and second resin layers constituting the laminate, such as a third resin layer described below, are provided, the member is also separate from the other resin layers. However, the member separate from the other resin layers, such as the third resin layer, may have the same resin composition as the other resin layers.

[0057] In the sixth embodiment, the release film 60 also includes a first resin layer 61 and second resin layers 62 and 63 provided on both surfaces 61A and 61B of the first resin layer 61. In this embodiment, a covering portion 64 covering an end surface 61E of the first resin layer 61 is formed of a covering member. The covering member may be, for example, a resin film. The covering portion 64 may have any configuration as long as it covers the end surface 61E. For example, it may cover the entire area from the outer surface of the second resin layer 62 to the end surface of the first resin layer and the outer surface of the second resin layer 63. The covering portion 64 may be bonded to the outer surfaces of the second resin layers 62 and 63 with an adhesive, or by fusion bonding, pressure bonding, or the like. The covering portion 64 may be formed using a plurality of covering members. In the sixth embodiment, the release film 60 is also provided with the covering portion 64, so that the resin that constitutes the first resin layer 61 can be effectively prevented from seeping out.

[0058] The resin film constituting the covering portion 64 may be a known resin film, but it is preferable to use a resin film that has a higher flow initiation temperature than the first resin layer 61 and also has a higher storage modulus. Specifically, the resin constituting the resin film may be appropriately selected from those usable for the second resin layer as described above, such as polyester resins, polyolefin resins, polystyrene resins, etc. These resins may also be used by appropriately adding thermoplastic resins or rubber components. Details of these resins are as described above for the second resin layer. The thickness of the resin film is not particularly limited, but is, for example, 1 to 250 μm, and preferably 5 to 150 μm.

[0059] When producing the release film 60 according to this embodiment, as in the above-described embodiments, first, a laminate including the first resin layer 61 and the second resin layers 62 and 63 is prepared, and a covering member (for example, a resin film) is also prepared. Then, the covering member (resin film) is attached to the end of the laminate, thereby obtaining the release film 60.

[0060] Seventh Embodiment Next, a release film 70 according to a seventh embodiment of the present invention will be described. 14 shows the end structure of a release film 70 according to a seventh embodiment. In this embodiment, the release film 70 also includes a first resin layer 71 and second resin layers 72 and 73 provided on both surfaces 71A and 71B of the first resin layer 71. In this embodiment, a covering portion 74 that covers the end surface 71E of the first resin layer 71 is formed from a covering member, and in this case, the covering member is a sealant. By including the covering portion 74 formed from a covering member (sealant), the release film 70 can effectively prevent the resin that constitutes the first resin layer 71 from seeping out.

[0061] 14, the covering portion 74 made of the sealant may be laminated not only on the first resin layer 71 but also on the end faces 72E, 73E of the second resin layers 72, 73. By laminating the sealant layer also on the end faces 72E, 73 of the second resin layers 72, 73, it is possible to more reliably prevent the resin constituting the first resin layer 71 from seeping out from the end face 71E.

[0062] As in the above embodiments, the release film 70 can be manufactured by first preparing a laminate having a first resin layer 71 and second resin layers 72 and 73, and then applying a sealant to the end of the laminate to form the covering portion 75.

[0063] The sealant constituting the covering portion 74 is not particularly limited, but may be an epoxy resin, a urethane resin, a silicone resin, a phenolic resin, a polyimide resin, etc. The thickness of the covering portion 74 is, for example, 1 to 1000 μm, and preferably 10 to 500 μm.

[0064] The covering portion made of the covering member exemplified and described in the sixth and seventh embodiments is not limited to a resin film or a sealant, as long as it can cover the end face of the first resin layer. In the sixth and seventh embodiments, the covering portion covers not only the end face of the first resin layer but also the end face of the second resin layer. However, as long as it covers the end face of the first resin layer, it is not necessary to cover the end face of the second resin layer. For example, the covering portion 74 formed from the sealant layer shown in the seventh embodiment may cover only the end face of the first resin layer.

[0065] Eighth Embodiment In the above first to seventh embodiments, a configuration has been shown in which the end face of the first resin layer is covered by a covering portion, but the end face of the first resin layer does not necessarily have to be covered by a covering portion, and the release film of the eighth embodiment has a configuration in which the end of the second resin layer is positioned so as to protrude outward beyond the end face of the first resin layer. Hereinafter, the release film 80 according to the eighth embodiment will be described in terms of differences from the first embodiment with reference to Fig. 15. Note that the points that will not be described are the same as those in the first embodiment.

[0066] A release film 80 according to the eighth embodiment includes a first resin layer 81 and second resin layers 82 and 83 provided on both surfaces 81A and 81B of the first resin layer 81. In this embodiment, both end portions of the second resin layers 82 and 83 are arranged to protrude outward beyond an end surface 81E of the first resin layer 81, thereby forming protruding portions 82E and 83E. According to this embodiment, when the release film 80 is used in a heat press, even if the resin constituting the first resin layer 81 flows due to the heat press, the flowed resin remains between the protruding portions 82E, 83E, thereby preventing it from seeping out beyond the outer edge of the release film 80.

[0067] Here, the overhang length L1 of the second resin layers 82, 83 need only be long enough to ensure that even if the resin of the first resin layer 81 flows during heat pressing, it remains between the overhanging portions 82E, 83E and is appropriately prevented from seeping out from the outer edge of the release film 80. The overhang length L1 is not particularly limited, but is, for example, 5 to 50 mm, and preferably 10 to 30 mm. The overhang length of the second resin layer 82 and the overhang length of the second resin layer 83 may be different.

[0068] The release film 80 according to this embodiment can be manufactured by preparing a resin film for forming the first resin layer 81 and second and third resin films for forming the second resin layers 82, 83, and laminating them by bonding them together using heat and pressure or the like. In this case, it is sufficient to prepare the second and third resin films that are one size larger than the first resin film. As described above, the release film according to this embodiment can be manufactured simply by heat and pressure bonding the resin films, which simplifies the manufacturing method.

[0069] In the present embodiment, when the release film 80 is in the form of a sheet, for example, it is typically quadrilateral such as a rectangle or square, and it is preferable that the end portions of the release film constituting each side (i.e., four sides) are provided with the protruding portions 82E, 83E as described above. However, similar to the covering portions shown in the first to seventh embodiments, it is not necessarily necessary to provide protruding portions on all of the end portions constituting each side of the release film 80. When the planar shape of the release film is polygonal, it is preferable that protruding portions are provided on at least two or more sides. Furthermore, when the release film 80 is in a roll form, it is preferable that protrusions 82E and 83E are provided on both side edges, similar to the covering portion described above.

[0070] The protruding portions 82E, 83E at each end of the release film 80 according to this embodiment may be fixed to each other by fixing means (not shown), such as a staple, an adhesive, fusion bonding, pressure bonding, etc. When the protruding portions 82E, 83E are fixed to each other, the first resin layer 81 is sandwiched from above and below by the second resin layers 82, 83, which makes the laminated structure more stable. Furthermore, by fixing the protruding portions 82E, 83E to each other, it is preferable that the protruding portions 82E, 83E form a covering portion 84 that covers the end face 81E, as shown in Fig. 16. In this case, it is preferable that at least a portion of the covering portion 84 is disposed with a space 88 interposed between it and the end face 81E, as shown in Fig. 16, but the space 88 does not have to be present. In this case, the release film 80 has a space between the first resin layer 81 and a fixing portion where the protruding portions 82E, 83E of the second resin layer are fixed to each other.

[0071] Furthermore, in the case of a rectangular or other sheet-like release film, for example, it is advisable to fix each end portion constituting each side (four sides in the case of a rectangular shape) by the fixing means, but it is not necessary to fix each end portion constituting all sides. Even if each end portion constituting all sides is not fixed, for example, by fixing each end portion constituting two opposing sides by the fixing means, the first resin layer 81 will be properly sandwiched between the second resin layers 82 and 83 by this fixation.

[0072] Furthermore, when the first resin layer 81 is sandwiched between the second resin layers 82 and 83 by the fixing means as described above, it is not necessary to bond the second resin layers 82 and 83 to both surfaces 81A and 81B of the first resin layer 81. Therefore, in manufacturing the release film 80, it is not necessary to bond the resin films together by pressure bonding or the like. In other words, the release film 80 can be manufactured by overlapping three resin films and fixing the protruding portions with the fixing means, which simplifies the manufacturing method and allows easy manufacturing without introducing large-scale manufacturing equipment. Furthermore, in this embodiment, both end portions of the second resin layers 82 and 83 are arranged to protrude outward beyond the end surface 81E of the first resin layer 81, forming protruding portions 82E and 83E, but the lengths of the protruding portions do not have to be the same. That is, the protruding portion 82E may be longer than the protruding portion 83E, or the protruding portion 82E may be shorter than the protruding portion 83E.

[0073] <Ninth embodiment> 17 shows the end structure of a release film according to the ninth embodiment. Hereinafter, the differences between the release film 90 according to the ninth embodiment and the first embodiment will be described, and the points that will not be described are the same as those in the first embodiment. A release film 90 according to the ninth embodiment includes a first resin layer 91 and second resin layers 92 and 93 provided on both sides 91A and 91B of the first resin layer 91. In this embodiment, the release film 90 has a folded portion 98. That is, the release film 90 has a structure in which the end portion is folded back toward the inside of the release film. Therefore, an end surface 91E of the first resin layer 91 is located inside an outer edge 90E of the release film 90. Furthermore, the end surface 91E of the first resin layer 91 faces inward with respect to the outer edge 90E of the release film 90. In addition, at the folded portion 98, one second resin layer 92 is disposed on the outer periphery side, and the other second resin layer 93 is disposed on the inner periphery side. According to this embodiment, even if the resin constituting the first resin layer 91 flows during heat pressing, the resin does not immediately flow outward from the outer edge 90E of the release film 90, thereby preventing the resin from seeping out from the outer edge of the release film 90.

[0074] 17, the outer surfaces of the second resin layers 93 of the release film 90 abut against each other at the folded-back portion 98, and these may be fixed by a fixing means such as adhesion with an adhesive, fusion bonding, pressure bonding, stabilization, etc. By fixing the outer surfaces of the second resin layers 93 to each other, the release film 90 can be easily held in a state in which the end portion is folded back. The release film 90 may be formed, for example, by folding back an end of a laminate composed of a first resin layer 91 and second resin layers 92 and 93. In this embodiment, the folded-back portion has a gently curved shape, but may also be flattened. The thickness of the folded-back portion may be smaller than the average thickness of the release film.

[0075] In this embodiment, the folded length L2 (i.e., the length from the outer edge 90E of the release film 90 to the end surface 91E of the first resin layer 91) should be long enough so that even if the resin constituting the first resin layer 91 flows out from the end surface 91E of the resin layer 91 during heat pressing, it remains inside the outer edge 90E of the release film 90. The length L2 is not particularly limited, but is, for example, 1 to 50 mm, and preferably 5 to 30 mm.

[0076] Furthermore, when the release film 90 in this embodiment is in the form of a sheet, for example, it is typically a quadrangle such as a rectangle or a square, and each of the end portions of the release film constituting each side (i.e., four sides) preferably has a folded portion. However, it is not necessary that all of the end portions constituting each side of the release film 90 have a folded portion. For example, when the planar shape of the release film is polygonal, it is preferable that at least two sides have a folded portion. Furthermore, when the release film 90 is in the form of a roll, it is preferable that both side end portions have a folded portion, similar to the covering portion described above.

[0077] <Other variations> In the release films according to the first to ninth embodiments described above, the second resin layer is provided on each of both surfaces of the first resin layer. However, the second resin layer may be provided on only one surface of the first resin layer. A specific example is shown in FIG. 18. FIG. 18 shows a modification of the first embodiment, in which the release film 10 includes a first resin layer 11 and a second resin layer 12 provided only on one surface 11A of the first resin layer 11. In this modification, the covering portion 14 is formed by the second resin layer 12, as in the first embodiment. The configuration of the covering portion 14 is as described in the first embodiment, but the second resin layer 13 is not provided on the other surface 11B. Therefore, the covering portion 14 formed by the second resin layer 12 does not come into contact with the resin layer (second resin layer) provided on the other surface 11B.

[0078] Similarly, in the second and third embodiments, the second resin layer may be provided on only one side of the first resin layer, in which case the covering portion may be formed by only one of the second resin layers. Similarly, in the sixth to ninth embodiments, one of the pair of second resin layers may be omitted. 19 shows a modified example of the ninth embodiment in which a second resin layer is provided on only one surface of the first resin layer. In this modified example, the second resin layer 92 is arranged on the outer periphery of the folded portion. In the release film 90 according to the ninth embodiment (see FIG. 17), the outer surfaces of the second resin layers abut against each other, but in this modified example (see FIG. 19), it is sufficient that the other surfaces 91B of the first resin layers 91 abut against each other, and the other surfaces 91B may be fixed to each other by a fixing means such as adhesive bonding, fusion bonding, pressure bonding, or stabilization. In the first to third embodiments and the sixth to ninth embodiments, the method for producing a release film when the second resin layer 13 is provided on only one side is the same as that described in each embodiment, except that one of the second resin layers is omitted in the prepared laminate.

[0079] In each embodiment, a third resin layer may be provided between the first and second resin layers. The third resin layer preferably functions as an adhesive layer that bonds the first and second resin layers. As an example of a structure in which third resin layers 19A and 19B are provided, a modified example of the first embodiment is shown in FIG. 20. While FIG. 20 shows an example in which one second resin layer 12 is connected to the other second resin layer 13 via the third resin layer 19B, even when a third resin layer is provided, the second resin layers 12 and 13 may be in direct contact with each other. Of course, the second resin layers 12 and 13 do not necessarily have to be connected to each other, and a portion of the end surface 11E may not be covered by the covering portion 14. In the first to sixth embodiments, the third resin layer may form a covering portion together with the second resin layer as shown in FIG. 20, or may not form a covering portion.

[0080] The resin constituting the third resin layer may be any resin as long as it can perform its function. For example, it may contain the resin constituting the main component of the first resin layer and the resin constituting the main component of the second resin layer in contact with the third resin layer. Therefore, the third resin layer preferably contains a polyolefin resin other than a polymethylpentene resin and at least one selected from polyester resins and polymethylpentene resins. The third resin layer may also contain a thermoplastic resin or rubber component other than these. Details of these resins, thermoplastic resins, and rubber components are as described for the first and second resin layers. The thickness of each of the third resin layers is, for example, 5 to 50 μm, and preferably 10 to 30 μm.

[0081] Here, when second resin layers are provided on both surfaces of the first resin layer, the third resin layer may be provided only between the first resin layer and one of the second resin layers, but it is preferable that the third resin layer be provided between the first resin layer and each of the second resin layers as shown in Fig. 20. In this way, by providing the third resin layer, the release film can bond the second resin layer to the first resin layer with high adhesive strength.

[0082] The release film of the present invention has the above-mentioned features, so that the resin constituting the first resin layer is less likely to seep out of the release film when heated and pressed. 2 When pressed under a pressure of 1.5 mm or less, the exudation amount of the first resin layer is preferably 1.5 mm or less, and more preferably 1.3 mm or less. By keeping the exudation amount at or below the upper limit, contamination of, for example, circuit boards, press plates, and secondary materials such as cushioning materials can be effectively prevented. The amount of exudation is the exudation length of the resin constituting the first resin layer, based on the outer edge of the release film when hot-pressed under the above-mentioned pressing conditions, and the maximum exudation length is used.

[0083] <How to use release film> The release film of the present invention can be suitably used, for example, when producing a circuit board such as an FPC. The circuit board can be produced by preparing a core substrate, a coverlay film, and a release film, and integrating the core substrate and the coverlay film by heat pressing using the release film. The method for producing the circuit board will be described in detail below.

[0084] The core substrate includes a base material made of polyimide resin, polyester resin, liquid crystal polymer, etc., and a circuit portion formed on the base material using a conductive material such as copper. The circuit portion may be provided on one side or both sides of the base material. The coverlay film includes a base film and an adhesive layer provided on one side of the base film. Examples of the base film include polyimide resin film, polyester resin film, and liquid crystal polymer. The adhesive layer is made of an epoxy adhesive, an acrylic adhesive, or the like. The release film can be appropriately selected from the release films of the present invention described above. As described below, a pair of release films is prepared, and they may have the same configuration or different configurations. Furthermore, it is sufficient to use the release film of the present invention described above for only one of the release films, but it is preferable to use the release films of the present invention described above for both release films.

[0085] In this manufacturing method, the core substrate, coverlay film, and release film are preferably superimposed on one another. The coverlay film is preferably superimposed on the core substrate so that the surface on which the adhesive layer is provided faces the core substrate. The coverlay film is preferably superimposed on the surface of the core substrate on which the circuit section is provided. Therefore, when the circuit section is provided on both sides of the substrate, the coverlay film is preferably superimposed on both sides of the substrate. When the circuit section is provided on one side of the substrate, the coverlay film is preferably superimposed on one side of the substrate. The release films may be overlaid on both sides of the core substrate, and when a coverlay film is overlaid on the core substrate, the release films may be overlaid on the outer side of the coverlay film. Therefore, specifically, it is advisable to stack the layers in the order of release film / coverlay film / core substrate / release film, or release film / coverlay film / core substrate / coverlay film / release film.

[0086] Next, the laminate of the superposed core substrate, cover lay film, and release film is heat-pressed using a press plate, so that the cover lay film is bonded to one or both sides of the core substrate by the adhesive layer, thereby obtaining a circuit board. The release film may be peeled off from the obtained circuit board. It is preferable to use a pair of press plates to sandwich the laminate between them and heat press, and a cushioning material or the like may be appropriately provided between the release film and the press plates. Examples of the cushioning material include glass cloth, paper, PVC film, polyester film, and polyolefin film.

[0087] In the release film of the present invention, even when heated and pressed by the heat press as described above, the resin constituting the first resin layer is unlikely to seep out of the release film, and therefore contamination of the circuit part, cushioning material, press plate, etc. caused by the release film can be prevented during the heat press.

[0088] As described above, the release film may have the second resin layer formed on only one side thereof. In such a case, the side on which the second resin layer is formed may face either the core substrate side or the press plate side, but it is preferable that the side face faces the core substrate side to prevent contamination of the circuit section.

[0089] The circuit board may be manufactured by a batch press or a quick press, or by a roll-to-roll method. When a batch press or a quick press is used, the core substrate, the coverlay film, and the release film may all be prepared in the form of sheets, which may then be stacked and pressed to manufacture the circuit board. In the case of roll-to-roll production, the core substrate, cover lay film, and release film, each of which is wound into a roll, are unwound into a sheet, and then superimposed on each other, followed by heat pressing using a press plate between the rolls to integrate the core substrate and the cover lay film, thereby producing a circuit board. After the circuit board is obtained, the release film may be peeled off while the circuit board is being transported between the rolls.

[0090] As a modification of the eighth embodiment, an example of a method for manufacturing a circuit board will be described. In the eighth embodiment, the release film is an integrated film including a first resin layer and second resin layers 82 and 83 provided on both sides of the first resin layer. Alternatively, these resin layers may be prepared as separate resin films, and during pressing, the second resin layer (one of the second resin films), the first resin layer (the first resin film), and the second resin layer (the other of the second resin films) may be laminated in this order. In this case, by making the dimensions of the second resin film larger than those of the first resin film and providing a protruding portion on the second resin film, it is possible to prevent the resin constituting the first resin film from seeping out and contaminating the surroundings. That is, the method for manufacturing a circuit board described here includes a lamination step of laminating a first resin film smaller in dimensions than the second resin film on the second resin film, and then laminating a second resin film larger in dimensions than the first resin film. By performing pressing after such a lamination step, a circuit board can be manufactured. Each resin film used in the method for manufacturing a circuit board shown here can have the same configuration as each resin layer provided in the release film according to the eighth embodiment.

[0091] The method of using the release film described above is just one example, and the release film may be used in other ways. For example, the release film may be used as a release film when manufacturing items other than circuit boards by hot pressing using a press plate. [Explanation of symbols]

[0092] 10, 20, 30, 40, 50, 60, 70, 80, 90 Release film 11, 21, 31, 41, 51, 61, 71, 81, 91 First resin layer 11E, 21E, 31E, 41E, 51E, 61E, 71E, 81E, 91E End surface of first resin layer 12, 13, 22, 23, 32, 33, 42, 43, 52, 53, 62, 63, 72, 73, 82, 83, 92, 93 Second resin layer 14, 24, 34, 44, 54, 64, 74 Covering 16, 26, 36, 46, 56 laminates 17 Push-cutting blade 27 Shear blade 37 Heating blade 48, 58 crimping part 57 Crimping means 82E, 83E protruding part

Claims

1. a first resin layer; and a second resin layer provided on at least one surface of the first resin layer and having a composition different from that of the first resin layer; The second resin layer has a protruding portion that protrudes outward beyond an end surface of the first resin layer.

2. The release film according to claim 1 , wherein the second resin layer is provided on each of both sides of the first resin layer, and each of the second resin layers has a protruding portion.

3. 3. The release film according to claim 2, wherein the protruding length L1 of at least one of the protruding portions of the second resin layer is 5 mm or more.

4. the protruding portions of the second resin layers have fixing portions at which the protruding portions are fixed to each other, The release film according to claim 2 or 3, wherein a space is formed between the fixing portion and the first resin layer.

5. 5. The release film according to claim 1, wherein the planar shape is a polygon, and the covering portion is provided on at least two sides thereof.

6. A method for producing a circuit board, comprising producing a circuit board using the release film according to any one of claims 1 to 5.

7. preparing a first resin layer and a second resin layer having a composition different from that of the first resin layer; a lamination step of overlaying a first resin film having dimensions smaller than that of the second resin film on the second resin film, and further overlaying a second resin film having dimensions larger than that of the first resin film, A method for manufacturing a circuit board, wherein pressing is performed after the laminating step.

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