Release film and methods for manufacturing release film.

Abstract

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Description

Release film and method for producing release film

[0001] The present invention relates to a release film and a method for producing the same, and more particularly to a release film used for transfer molding or compression molding and a method for producing the same.

[0002] To encapsulate a semiconductor with a resin, molding techniques such as transfer molding and compression molding are used. In these molding techniques, a release film is often used to easily remove the molded body from the mold after the resin has hardened in the mold. Various proposals have been made regarding release films.

[0003] For example, Patent Document 1 below discloses a release film characterized by including a coating film formed from a composition containing a fluororesin (A) containing a functional group X and a release component (B), and a layer formed from a non-fluorinated polymer. Patent Document 2 below also discloses a release film having at least a release layer (I) with excellent release properties and a plastic support layer (II) supporting the release layer (I), wherein the strength of the plastic support layer (II) at 200% elongation at 170°C is 1 MPa to 50 MPa, and the xylene gas permeability of the release film at 170°C is 5×10 -15 (kmol・m / (s・m 2 A gas barrier release film for semiconductor resin molds is disclosed, characterized in that the gas barrier resistance is 1.0 kPa or less.

[0004] JP 2015-74201 A International Publication No. 2008 / 020543

[0005] As described above, the release film is used to easily remove the molded article from the mold, and is required to be easily peeled off from the molded article after the resin has cured.

[0006] Furthermore, when the release film is exposed to high temperatures in the mold, components contained in the release film may migrate to the surface of the release film, and the migrated components may contaminate the mold or molded body. When such contamination occurs, it becomes necessary to remove the components from the mold or molded body. Furthermore, removing the components is often difficult. Therefore, it is necessary to prevent contamination of the mold or molded body by the components.

[0007] Furthermore, if a release film can be used not only for one molding but also for multiple moldings, molding costs can be reduced. However, in order to repeatedly use a release film for multiple moldings, it is necessary to maintain the performance of the release film throughout the multiple moldings.

[0008] In view of the above, an object of the present invention is to provide a release film that does not contaminate a mold or a molded body. Another object of the present invention is to provide a release film that does not contaminate a mold or a molded body and can be used continuously in multiple molding operations.

[0009] The present inventors have found that a release film having a specific configuration has excellent releasability and low contamination. The present inventors have also found that the release film can be used for multiple moldings.

[0010] That is, the present invention provides a release film including a base layer formed from an easily moldable polyethylene terephthalate resin and surface layers formed from a fluorine-based resin laminated on two surfaces of the base layer. The easily moldable polyethylene terephthalate resin may have a glass transition temperature of 60°C to 95°C. The release film may have a tensile break strength of 40 MPa to 200 MPa when measured at 175°C according to JIS K7127, and a tensile break elongation of 200% to 500% when measured at 175°C according to JIS K7127. The release film may have an oxygen gas permeability of 5,000 to 50,000 cc / m2·24 hr·atm when measured at 175°C according to JIS K7126-1. The tensile break strength of the substrate layer may be 40 MPa to 200 MPa when measured at 175°C according to JIS K7127. The tensile break elongation of the substrate layer may be 200% to 500% when measured at 175°C according to JIS K7127. The fluororesin forming the surface layer laminated on at least one surface of the substrate layer may include an isocyanate-based curing agent. The fluororesin forming the surface layer laminated on at least one surface of the substrate layer may include particles having an average particle size of 1 μm to 10 μm when measured by laser diffraction particle size analysis. The fluororesin forming the surface layer may include a tetrafluoroethylene-based resin. The release film may be used for transfer molding or compression molding. The release film may be used for two or more molding processes.

[0011] The present technology also provides a method for producing a release film, the method including: a coating step of coating a fluororesin composition on two surfaces of a substrate layer formed from an easily formable polyethylene terephthalate resin; and a curing step of curing the fluororesin composition after the coating step.

[0012] The present invention provides a release film that has excellent releasability and low contamination. Furthermore, the release film of the present invention can be repeatedly used for multiple moldings. Note that the effects of the present invention are not necessarily limited to the effects described herein, and may be any of the effects described in this specification.

[0013] FIG. 1 is a diagram showing an example of the structure of the release film of the present invention. FIG. 2 is a diagram showing an example of a method for using the release film of the present invention in transfer molding. FIG. 3 is a diagram showing an example of a method for using the release film of the present invention in compression molding. FIG. 4 is a diagram showing an FT-IR spectrum. FIG. 5 is an electron microscope photograph of the mold side surface of the release film after molding. FIG. 6 is an electron microscope photograph of the mold side surface of the release film after molding. FIG. 7 is a microscope photograph of the surface of the release film after heating. FIG. 8 is a microscope photograph of the surface of the release film after heating.

[0014] Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the embodiments described below are examples of typical embodiments of the present invention, and the present invention is not limited to these embodiments.

[0015] 1. Release film

[0016] The release film of the present invention includes a base layer formed from an easily moldable polyethylene terephthalate resin and surface layers formed from a fluororesin laminated on two sides of the base layer. An example of the structure of the release film of the present invention is shown in FIG. 1. As shown in FIG. 1, the release film 100 of the present invention is composed of a base layer 101 and surface layers 102 and 103 laminated on both sides thereof. The base layer 101 is formed from an easily moldable polyethylene terephthalate resin. The two surface layers 102 and 103 are formed from a fluororesin. The two surface layers 102 and 103 may be formed from the same fluororesin or different fluororesins.

[0017] The release film of the present invention is composed of the base layer and the surface layers formed on both sides of the base layer, and therefore has excellent releasability and is less likely to contaminate the mold and / or molded article during molding. Furthermore, the release film of the present invention can be used for multiple moldings. The effects achieved by the release film of the present invention will be described in more detail below.

[0018] Polyethylene terephthalate resin contains oligomers with low degrees of polymerization that are generated during its production. When molding is performed using a release film containing a layer formed from polyethylene terephthalate resin, the oligomers may migrate to the surface of the release film and contaminate the molded product and / or mold surface. This contamination can occur even when a fluororesin layer is laminated on the surface of the polyethylene terephthalate resin layer. This is thought to be because the oligomers pass through the fluororesin layer. This contamination is particularly likely to occur when a single release film is used for multiple moldings. This is probably because the oligomers migrate from the interior of the polyethylene terephthalate resin to the surface when heat is applied to the polyethylene terephthalate resin during molding. The release film of the present invention has a configuration in which surface layers formed from fluororesins are laminated on both sides of a base layer formed from a readily moldable polyethylene terephthalate resin. Although the readily moldable polyethylene terephthalate resin also contains the oligomers, adopting the above configuration reduces or eliminates contamination of the molded product and / or mold caused by the oligomers. Furthermore, the low contamination properties of the release film of the present invention are maintained through multiple moldings.

[0019] In addition, release films are generally replaced with new ones after each molding. This is because if a release film that has been used once for molding is reused for molding, the release film is more likely to tear. Breaking of the release film is fatal to molding, for example, causing an abnormal shape of the molded body or the mold to adhere to the molded body. The release film according to the present invention is resistant to tearing and maintains its releasability and low contamination even when used for multiple moldings. Therefore, the release film according to the present invention can be used for multiple moldings, thereby reducing molding costs.

[0020] The release film of the present invention will be described in more detail below.

[0021] [Base material layer]

[0022] The base layer included in the release film of the present invention is formed from an easily moldable polyethylene terephthalate resin. Easily moldable polyethylene terephthalate resin (also referred to as easily moldable PET resin) is a term used to refer to a PET resin that has superior moldability to ordinary polyethylene terephthalate resins. The fact that the base layer is formed from the easily moldable polyethylene terephthalate resin particularly contributes to the low contamination properties of the release film of the present invention.

[0023] The glass transition temperature of the easily moldable polyethylene terephthalate resin is preferably 60°C to 95°C, and more preferably 65°C to 90°C. The fact that the easily moldable polyethylene terephthalate resin composition has a glass transition temperature within the above range contributes to making the release film of the present invention usable for multiple moldings. Ordinary polyethylene terephthalate generally has a glass transition temperature of 100°C or higher. The glass transition temperature of the easily moldable polyethylene terephthalate resin composition used in the present invention is lower than that of general-purpose polyethylene terephthalate. The glass transition temperature is measured by differential thermal analysis (DTA).

[0024] The easily moldable polyethylene terephthalate resin may be, for example, a copolymerized polyethylene terephthalate resin. The copolymerized polyethylene terephthalate may be obtained by, for example, reacting terephthalic acid, ethylene glycol, and a copolymerization component, or by mixing and melting a copolymerization component polymer with polyethylene terephthalate, followed by a distribution reaction. The copolymerization component may be, for example, an acid component or an alcohol component. Examples of the acid component include aromatic dibasic acids (e.g., isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid), aliphatic dicarboxylic acids (e.g., adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid), and alicyclic dicarboxylic acids (e.g., cyclohexanedicarboxylic acid). Examples of the alcohol component include aliphatic diols (e.g., butanediol, hexanediol, neopentyl glycol, and hexanediol) and alicyclic diols (e.g., cyclohexanedimethanol). The copolymerization component may be one or a combination of two or more of these compounds. The acid component may in particular be isophthalic acid and / or sebacic acid.

[0025] The substrate layer formed from the easily moldable polyethylene terephthalate resin used in the present invention may be a commercially available material. For example, Teflex™ FT, Teflex™ FT3, and Teflex™ FW2 (all manufactured by Teijin Film Solutions Co., Ltd.) may be used as the substrate layer. Alternatively, Emblet CTK-38 (manufactured by Unitika Ltd.) may be used as the substrate layer. The substrate layer formed from the easily moldable polyethylene terephthalate resin may be produced by the method described in, for example, JP-A No. 2-305827, JP-A No. 3-86729, or JP-A No. 3-110124. According to one preferred embodiment of the present invention, the substrate layer may be a easily moldable polyethylene terephthalate resin that has been biaxially stretched so that the plane orientation coefficient is preferably 0.06 to 0.16, more preferably 0.07 to 0.15, as described in any of these publications.

[0026] The tensile breaking strength of the base layer, when measured at 175°C according to JIS K7127, is preferably 40 MPa to 200 MPa, more preferably 40 MPa to 120 MPa, even more preferably 40 MPa to 110 MPa, and particularly preferably 45 MPa to 100 MPa. The tensile breaking elongation of the base layer, when measured at 175°C according to JIS K7127, is preferably 200% to 500%, more preferably 250% to 450%, and even more preferably 300% to 400%. The easily moldable polyethylene terephthalate resin forming the base layer has better elongation than general-purpose PET resins. Therefore, the base layer can have, for example, a tensile breaking strength and / or a tensile breaking elongation within the above-mentioned numerical ranges. Having the tensile breaking strength and / or a tensile breaking elongation of the base layer within the above-mentioned numerical ranges contributes to enabling the release film of the present invention to be used in multiple molding operations.

[0027] The thickness of the base layer may be, for example, 10 μm to 80 μm, preferably 15 μm to 75 μm, and more preferably 20 μm to 70 μm. This thickness contributes to enabling the release film of the present invention to be used in multiple moldings.

[0028] [Surface layer]

[0029] The surface layer constituting the release film of the present invention is formed from a fluororesin. According to a preferred embodiment of the present invention, the fluororesin does not contain chlorine. The absence of chlorine improves the durability and / or antifouling properties of the layer. The fluororesin may be, for example, a cured product of a fluororesin composition containing a reactive functional group-containing fluoropolymer and a curing agent. The fluororesin preferably contains a tetrafluoroethylene resin, and more preferably contains tetrafluoroethylene resin as a main component. In this specification, the tetrafluoroethylene resin refers to a component obtained by a curing reaction between a reactive functional group-containing tetrafluoroethylene polymer and a curing agent, as described below. "The tetrafluoroethylene resin is the main component" means that the fluororesin is composed solely of the tetrafluoroethylene resin, or that the amount of the tetrafluoroethylene resin is the largest among the components contained in the fluororesin. For example, the content of the tetrafluoroethylene resin in the fluororesin may be, for example, 70% by mass or more, preferably 75% by mass or more, more preferably 80% by mass or more, and particularly preferably 85% by mass or more, based on the total mass of the fluororesin. The content may be, for example, 99% by mass or less, particularly 98% by mass or less, and more particularly 97% by mass or less, based on the total mass of the fluororesin.

[0030] The reactive functional group-containing fluoropolymer contained in the fluororesin composition may be a fluoropolymer that can be cured with the curing agent. The reactive functional group and the curing agent may be appropriately selected by a person skilled in the art. The reactive functional group may be, for example, a hydroxyl group, a carboxyl group, a group represented by -COOCO-, an amino group, or a silyl group, and is preferably a hydroxyl group. These groups allow the reaction to proceed smoothly to obtain the cured product. Of these reactive functional groups, a hydroxyl group is particularly suitable for the reaction to obtain the cured product. That is, the reactive functional group-containing fluoropolymer may preferably be a hydroxyl group-containing fluoropolymer, and more preferably a hydroxyl group-containing tetrafluoroethylene polymer.

[0031] The fluorine-containing unit of the reactive functional group-containing fluorine-based polymer is preferably the fluorine-containing unit based on perfluoroolefin.The fluorine-containing unit based on this perfluoroolefin can more preferably be based on one, two or three selected from tetrafluoroethylene (tetrafluoroethylene, hereinafter referred to as "TFE"), hexafluoropropylene (HFP) and perfluoro(alkyl vinyl ether) (PAVE).Preferably, among the fluorine-containing units based on this perfluoroolefin, the fluorine-containing unit based on TFE is the most abundant.

[0032] The hydroxyl value of the reactive functional group-containing fluoropolymer (particularly the hydroxyl value of the hydroxyl group-containing fluoropolymer) is preferably 10 mgKOH / g to 300 mgKOH / g, more preferably 10 mgKOH / g to 200 mgKOH / g, and even more preferably 10 mgKOH / g to 150 mgKOH / g. When the hydroxyl value of the reactive functional group-containing fluoropolymer is equal to or greater than the lower limit of the above-mentioned range, the curability of the resin composition can be improved. Furthermore, when the hydroxyl value of the reactive functional group-containing fluoropolymer is equal to or less than the upper limit of the above-mentioned range, this can contribute to making the cured product of the resin composition suitable for multiple moldings. The hydroxyl value is obtained by measurement according to JIS K 0070.

[0033] The acid value of the reactive functional group-containing fluoropolymer (particularly the acid value of the hydroxyl group-containing fluoropolymer) is preferably 0.5 mgKOH / g to 100 mgKOH / g, more preferably 0.5 mgKOH / g to 50 mgKOH / g. When the acid value of the reactive functional group-containing fluoropolymer is equal to or greater than the lower limit of the above-mentioned range, the curability of the resin composition can be improved. Furthermore, when the acid value of the reactive functional group-containing fluoropolymer is equal to or less than the upper limit of the above-mentioned range, the cured product of the resin composition can be suitable for multiple moldings.

[0034] The reactive functional group of the reactive functional group-containing fluoropolymer may be introduced into the fluoropolymer by copolymerizing a monomer having the reactive functional group with a fluorine-containing monomer (particularly the perfluoroolefin). That is, the reactive functional group-containing fluoropolymer may contain polymerization units based on the reactive functional group-containing monomer and polymerization units based on the fluorine-containing monomer (particularly the perfluoroolefin).

[0035] When the reactive functional group is a hydroxyl group, the monomer having the reactive functional group may preferably be a hydroxyl group-containing vinyl ether or a hydroxyl group-containing allyl ether. Examples of hydroxyl group-containing vinyl ethers include 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxy-2-methylbutyl vinyl ether, 5-hydroxypentyl vinyl ether, and 6-hydroxyhexyl vinyl ether. Examples of hydroxyl group-containing allyl ethers include 2-hydroxyethyl allyl ether, 4-hydroxybutyl allyl ether, and glycerol monoallyl ether. Alternatively, the monomer having the reactive functional group may be a hydroxyalkyl ester of (meth)acrylic acid, such as 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate. One or a combination of two or more of these compounds may be used as the monomer having the reactive functional group. When the reactive functional group is a hydroxyl group, the monomer having the reactive functional group is more preferably a hydroxyl group-containing vinyl ether, and particularly preferably 4-hydroxybutyl vinyl ether and / or 2-hydroxyethyl vinyl ether, from the viewpoint of the curability of the resin composition.

[0036] When the reactive functional group is a carboxyl group, the monomer having the reactive functional group may preferably be an unsaturated carboxylic acid, an ester of an unsaturated carboxylic acid, or an acid anhydride of an unsaturated carboxylic acid.When the reactive functional group is an amino group, the monomer having the reactive functional group may be, for example, an amino vinyl ether or an allylamine.When the reactive functional group is a silyl group, the monomer having the reactive functional group may preferably be a silicone vinyl monomer.

[0037] The fluorine-containing monomer is preferably a perfluoroolefin. Examples of perfluoroolefins include tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and perfluoro(alkyl vinyl ether) (PAVE). Preferably, the fluorine-containing monomer includes TFE.

[0038] Preferably, the reactive functional group-containing fluoropolymer may contain, in addition to polymerized units based on the reactive functional group-containing monomer and polymerized units based on the fluorine-containing monomer, polymerized units based on a fluorine-free vinyl monomer. The fluorine-free vinyl monomer may be, for example, one or a combination of two or more selected from the group consisting of vinyl carboxylic acid esters, alkyl vinyl ethers, and non-fluorinated olefins. Examples of vinyl carboxylic acid esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caproate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl cyclohexylcarboxylate, vinyl benzoate, and vinyl para-t-butylbenzoate. Examples of alkyl vinyl ethers include methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, and cyclohexyl vinyl ether. Examples of non-fluorinated olefins include ethylene, propylene, n-butene, and isobutene. Furthermore, the reactive functional group-containing fluorine-based polymer may contain, in addition to polymerization units based on the reactive functional group-containing monomer and polymerization units based on the fluorine-containing monomer which is a perfluoroolefin, polymerization units based on a fluorine-based monomer other than a perfluoroolefin, such as vinylidene fluoride (VdF), chlorotrifluoroethylene (CTFE), vinyl fluoride (VF), and fluorovinyl ether.

[0039] The reactive functional group-containing fluoropolymer may be, for example, a TFE / non-fluorinated olefin / hydroxybutyl vinyl ether copolymer, a TFE / carboxylic acid vinyl ester / hydroxybutyl vinyl ether copolymer, or a TFE / alkyl vinyl ether / hydroxybutyl vinyl ether copolymer. More specifically, the reactive functional group-containing fluoropolymer may be a TFE / isobutylene / hydroxybutyl vinyl ether copolymer, a TFE / vinyl versatate / hydroxybutyl vinyl ether copolymer, or a TFE / VdF / hydroxybutyl vinyl ether copolymer. The reactive functional group-containing fluoropolymer is particularly preferably a TFE / isobutylene / hydroxybutyl vinyl ether copolymer or a TFE / vinyl versatate / hydroxybutyl vinyl ether copolymer. Examples of the reactive functional group-containing fluoropolymer that can be used include Zeffle GK series products.

[0040] The curing agent contained in the fluororesin composition may be appropriately selected by a person skilled in the art depending on the type of reactive functional group contained in the reactive functional group-containing fluoropolymer. When the reactive functional group is a hydroxyl group, the curing agent may be preferably one or a combination of two or more selected from an isocyanate-based curing agent, a melamine resin, a silicate compound, and an isocyanate group-containing silane compound. When the reactive functional group is a carboxyl group, the curing agent may be preferably one or a combination of two or more selected from an amino-based curing agent and an epoxy-based curing agent. When the reactive functional group is an amino group, the curing agent may be one or a combination of two or more selected from a carbonyl group-containing curing agent, an epoxy-based curing agent, and an acid anhydride-based curing agent. The content of the curing agent in the fluororesin composition may be, for example, 15 to 50 parts by mass, preferably 20 to 40 parts by mass, and more preferably 23 to 35 parts by mass, per 100 parts by mass of the reactive functional group-containing fluoropolymer. These numerical ranges also apply to the content of the curing agent in the cured product of the fluororesin composition. The content of the curing agent may be measured by pyrolysis gas chromatography / mass spectrometry (Py-GC / MS).

[0041] In one embodiment of the present invention, the reactive functional group contained in the reactive functional group-containing fluoropolymer may be a hydroxyl group, and the curing agent may be an isocyanate-based curing agent. In this embodiment, the isocyanate-based curing agent is preferably a hexamethylene diisocyanate (HDI)-based polyisocyanate. The content of the HDI-based polyisocyanate in the fluororesin composition may be, for example, 15 to 50 parts by mass, preferably 20 to 40 parts by mass, and more preferably 23 to 35 parts by mass, per 100 parts by mass of the reactive functional group-containing fluoropolymer. These numerical ranges also apply to the content of the HDI-based polyisocyanate in a cured product of the fluororesin composition.

[0042] The HDI polyisocyanate may be, for example, one or a combination of two or more selected from isocyanurate polyisocyanates, adduct polyisocyanates, and biuret polyisocyanates. In the present invention, the isocyanate curing agent is preferably an isocyanurate polyisocyanate and / or an adduct polyisocyanate, more preferably a combination of an isocyanurate polyisocyanate and an adduct polyisocyanate. When a combination of an isocyanurate polyisocyanate and an adduct polyisocyanate is used as the curing agent, the mass ratio of the two is, for example, 10:6 to 10:10, preferably 10:7 to 10:9. The total amount of the two may be, for example, 15 to 50 parts by mass, preferably 20 to 40 parts by mass, and more preferably 25 to 35 parts by mass, per 100 parts by mass of the reactive functional group-containing fluoropolymer. The content ratio of these curing agents may be determined by pyrolysis gas chromatography (Py-GC / MS) method.

[0043] The fluororesin forming the surface layer preferably contains particles having an average particle size of 1 μm to 10 μm, more preferably 2 μm to 9 μm, as measured according to a laser diffraction particle size analysis method. The average particle size is a volume-weighted volume average diameter measured according to JIS Z8825. The average particle size can be measured using, for example, a particle size analyzer (SALD-2200, Shimadzu Corporation). By containing such particles, the releasability of the release film can be improved.

[0044] The particles are preferably inorganic or organic particles. Examples of inorganic particles include silicon dioxide (particularly amorphous silicon dioxide), calcium carbonate, magnesium carbonate, calcium phosphate, kaolin, talc, aluminum oxide, titanium oxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and molybdenum sulfide. Examples of organic particles include crosslinked polymer particles and calcium oxalate. In the present invention, the particles are preferably inorganic particles, more preferably silicon dioxide particles, and even more preferably amorphous silicon dioxide. The amorphous silicon dioxide can be sol-gel type silica. Examples of amorphous silicon dioxide include amorphous silicon dioxide from the Cysilia series.

[0045] The content of the particles in the fluororesin composition may be, for example, 10 to 30 parts by mass, preferably 12 to 25 parts by mass, and more preferably 15 to 20 parts by mass, relative to 100 parts by mass of the reactive functional group-containing fluoropolymer. These numerical ranges also apply to the content of the particles in a cured product of the fluororesin composition. The content of the particles may be measured by thermogravimetric analysis (TGA).

[0046] The fluororesin composition may contain a solvent. The type of solvent may be appropriately selected by those skilled in the art. Examples of the solvent include butyl acetate, ethyl acetate, and methyl ethyl ketone (also known as MEK). For example, a mixture of these three solvents may be used as the solvent.

[0047] The fluororesin composition may contain a release promoter. Examples of release promoters include amino-modified methylpolysiloxane, epoxy-modified methylpolysiloxane, carboxy-modified methylpolysiloxane, and carbinol-modified methylpolysiloxane. Preferably, the release promoter is amino-modified methylpolysiloxane. The amount of the release promoter may be, for example, 0.01 to 3 parts by mass, preferably 0.05 to 2 parts by mass, and more preferably 0.1 to 1 part by mass, per 100 parts by mass of the reactive functional group-containing fluoropolymer. These numerical ranges also apply to the content of the release promoter in the cured product of the fluororesin composition.

[0048] The thickness of the surface layer may be, for example, 1 μm to 10 μm, preferably 2 μm to 9 μm, and more preferably 3 μm to 8 μm.

[0049] The fluororesin composition can be produced by mixing and stirring the above-described components by means known to those skilled in the art. For example, a mixer such as a high-speed mixer, a homomixer, or a paint shaker can be used for the mixing and stirring. For example, a dissolver such as an edge turbine-type high-speed dissolver can also be used for the mixing and stirring. A cured product of the fluororesin composition can be obtained by applying the fluororesin composition to the surface of the substrate layer and heating it at, for example, 100°C to 200°C, preferably 120°C to 180°C, for example, 10 seconds to 240 seconds, preferably 30 seconds to 120 seconds. The cured product forms the surface layer. The amount of the fluororesin composition to be applied can be appropriately determined by those skilled in the art depending on the thickness of the surface layer to be formed.

[0050] Of the two surface layers, one surface layer comes into contact with the mold during production of the molded body, and the other surface layer comes into contact with the molded body during production of the molded body. In this specification, the surface layer that comes into contact with the mold is referred to as the mold-side surface layer, and the surface layer that comes into contact with the molded body is referred to as the mold-side surface layer. The composition of the mold-side surface layer and the composition of the mold-side surface layer may be the same or different. The mold-release accelerator is preferably contained in the fluororesin of the molded-body-side surface layer. The mold-release accelerator may be contained in the fluororesin of both the mold-side surface layer and the molded-body-side surface layer.

[0051] In a preferred embodiment of the present technology, the mold-side surface layer is formed from a cured product of a fluororesin composition containing the reactive functional group-containing fluoropolymer, the curing agent, and the particles, and the molded body-side surface layer is formed from a cured product of a fluororesin composition containing the reactive functional group-containing fluoropolymer (particularly a hydroxyl group-containing tetrafluoroethylene polymer), the curing agent, the particles, and the mold release accelerator. More preferably, the mold-side surface layer is formed from a cured product of a fluororesin composition containing a hydroxyl group-containing tetrafluoroethylene polymer, an HDI-based polyisocyanate, and silicon dioxide particles, and the molded body-side surface layer is formed from a cured product of a fluororesin composition containing a hydroxyl group-containing tetrafluoroethylene polymer, an HDI-based polyisocyanate, silicon dioxide particles, and an amino-modified methylpolysiloxane. Having such two surface layers particularly contributes to imparting excellent mold releasability to the release film of the present invention.

[0052] [Features of release film]

[0053] According to a preferred embodiment of the present invention, the tensile breaking strength of the release film of the present invention, when measured at 175°C in accordance with JIS K7127, is 40 MPa to 200 MPa, more preferably 40 MPa to 120 MPa, even more preferably 40 MPa to 110 MPa, and particularly preferably 45 MPa to 100 MPa, and the tensile breaking elongation of the release film, when measured at 175°C in accordance with JIS K7127, can be 200% to 500%, more preferably 250% to 450%, and even more preferably 300% to 400%. The fact that the tensile breaking strength and tensile breaking elongation of the release film of the present invention are within the above numerical ranges contributes to making the release film of the present invention usable in multiple molding operations.

[0054] The gas (O2) permeability of the release film of the present invention is, for example, 5,000 to 50,000 cc / m when measured at 175°C in accordance with JIS K7126-1. 2 24 hr atm, particularly 5000 to 30000 cc / m 2 24 hr atm, more particularly 5000 to 20000 cc / m 2 The release film of the present invention has such low gas permeability. Therefore, by using the release film of the present invention to perform molding, mold contamination by gas generated from the resin is suppressed.

[0055] The thickness of the release film of the present invention can be, for example, 30 μm to 100 μm, preferably 35 μm to 90 μm, and more preferably 40 to 80 μm. When the thickness of the release film of the present invention is within the above numerical range, the release film can easily deform to conform to the shape of the mold.

[0056] [Release film applications]

[0057] The release film of the present invention may be used in, for example, various molding processes, and is particularly suitable for use in transfer molding or compression molding. The release film of the present invention can be used by being disposed between a mold and a resin, for example, in transfer molding or compression molding. The molding temperature in the molding process in which the release film of the present invention is used can be, for example, 100°C to 250°C, and preferably 120°C to 200°C.

[0058] An example of a method for using the release film of the present invention in transfer molding will be described with reference to FIG. 2. As shown in FIG. 2(A), the release film 100 of the present invention is placed between an upper mold 201 and a lower mold 203 on which a semiconductor element mounting substrate 202 is placed. Next, as shown in FIG. 2(B), with the release film 100 attached to the inner surface of the mold 201, the upper mold 201 is brought into contact with the substrate 202 and the lower mold 203. Next, as shown in FIG. 2(C), a resin 204 is introduced between the upper mold 201 and the substrate 202, and then the resin 204 is cured. After curing, the upper mold 201 is released from the substrate 202 as shown in FIG. 2(D). The release film of the present invention has excellent releasability, allowing the cured resin 204 to be smoothly released from the upper mold 201 in the step of FIG. 2(D). If the release film does not have good releasability, the release film 250 may stick to the hardened resin 204, as shown in FIG. 2(E), for example.

[0059] An example of a method for using the release film of the present invention in compression molding will be described with reference to FIG. 3. As shown in FIG. 3(A), the release film 100 of the present invention is placed between a lower mold 301 and an upper mold 303 to which a substrate 302 on which a semiconductor element is mounted is attached. Next, as shown in FIG. 3(B), with the release film 100 attached to the inner surface of the lower mold 301, a resin 304 is placed in the recess of the lower mold 301. As shown in FIG. 3(C), the upper mold 303 is moved to contact the lower mold 301. The resin 304 then hardens. After hardening, the upper mold 303 is released from the lower mold 301 as shown in FIG. 3(D). The release film of the present invention has excellent releasability, which allows the cured resin 304 to be smoothly released from the lower mold 301 in the step of FIG. 3(D).

[0060] The release film of the present invention may be used for molding various resins, for example, for molding epoxy resins or silicone resins. The type of resin for forming a molded product may be appropriately selected by those skilled in the art.

[0061] The release film of the present invention can be used for molding, for example, two or more times, preferably four or more times, more preferably five or more times, more preferably six or more times, and even more preferably eight or more times. The release film of the present invention can be used for molding, for example, two to twenty times, preferably four to fifteen times, more preferably five to fifteen times, more preferably six to fifteen times, and even more preferably eight to twelve times. The release film of the present invention maintains its performance and is resistant to tearing through multiple mold releases. Therefore, the release film of the present invention can be used for multiple moldings. This reduces molding costs.

[0062] [Method for Producing a Release Film] The present invention provides a method for producing the release film described above. This method includes a coating step of coating two surfaces of a substrate layer formed from a readily moldable polyethylene terephthalate resin with a fluororesin composition, and a curing step of curing the fluororesin composition after the coating step. The above description applies to the substrate layer and fluororesin composition used in the coating step, so further explanation is omitted. The coating step may be performed appropriately by those skilled in the art to achieve a desired layer thickness. For example, the fluororesin composition may be applied to the two surfaces of the substrate layer by a gravure roll method, a reverse roll method, an offset gravure method, a kiss coat method, a reverse kiss coat method, a wire bar coating method, a spray coat method, or an impregnation method. Apparatuses for applying the composition by these methods may be appropriately selected by those skilled in the art. The curing step includes heating the fluororesin composition, for example, at 100°C to 200°C, preferably 120°C to 180°C, for example, for 10 seconds to 240 seconds, preferably 30 seconds to 120 seconds. The fluorine-based resin composition is cured by the heating.

[0063] The present invention will be described in more detail below with reference to examples. Note that the examples described below are representative examples of the present invention, and the scope of the present invention is not limited to these examples.

[0064] Example 1

[0065] A film made of easily moldable polyethylene terephthalate resin (Teflex FT, manufactured by Teijin Limited, thickness 50 μm, glass transition temperature 90° C.) was prepared as a substrate layer. Next, two types of fluororesin compositions (hereinafter referred to as the first fluororesin composition and the second fluororesin composition) to be applied to the film were prepared. The first fluorine-based resin composition was prepared by mixing and stirring 100 parts by mass of a hydroxyl group-containing tetrafluoroethylene-based resin composition (Zeffle GK570, Daikin Industries, Ltd., of which 65% by mass is the hydroxyl group-containing tetrafluoroethylene-based resin), 11.47 parts by mass of amorphous silicon dioxide (Cysilia 380, Fuji Silysia Chemical Ltd.), 10 parts by mass of an isocyanurate-type polyisocyanate (curing agent, Sumidur N3300, Sumitomo Bayer Urethane Co., Ltd.), 7.79 parts by mass of an adduct-type polyisocyanate (curing agent, Duranate AE700-100), 6.18 parts by mass of butyl acetate, 44.62 parts by mass of ethyl acetate, and 89.25 parts by mass of MEK. The average particle size (volume average diameter) of the amorphous silicon dioxide was 8.8 μm when measured according to a laser diffraction particle size analysis method using a particle size analyzer (SALD-2200, Shimadzu Corporation). The second fluororesin composition was the same as the first fluororesin composition, except that 0.31 parts by mass of amino-modified methylpolysiloxane (mold release promoter, Shin-Etsu Chemical Co., Ltd.) was further added to the first fluororesin composition.

[0066] The first fluororesin composition was applied to one side of the film, and the second fluororesin composition was applied to the other side of the film. These applications were carried out using a kiss-reverse type application device. After the applications, these compositions were cured by heating at 150°C for 60 seconds, thereby obtaining a release film in which fluororesin layers were laminated on both sides of a moldable PET resin film (hereinafter referred to as "the release film of Example 1").

[0067] The thickness of the release film of Example 1 was 70±5 μm. The thickness of the base layer in the release film of Example 1 was 50 μm±10%. Of the two surface layers of the release film of Example 1, the surface layer formed from the cured product of the first fluororesin composition had a thickness of 5.5±0.5 μm. The surface layer formed from the cured product of the second fluororesin composition had a thickness of 5.5±0.5 μm.

[0068] The cured product of the first fluorine-based resin composition contained 17.65 parts by mass of the amorphous silicon dioxide, 15.39 parts by mass of the isocyanurate polyisocyanate, and 11.98 parts by mass of the adduct polyisocyanate, relative to 100 parts by mass of the hydroxyl group-containing tetrafluoroethylene resin.

[0069] The cured product of the second fluorine-based resin composition contained 17.65 parts by mass of the amorphous silicon dioxide, 15.39 parts by mass of the isocyanurate-type polyisocyanate, 11.98 parts by mass of the adduct-type polyisocyanate, and 0.48 parts by mass of amino-modified methylpolysiloxane, relative to 100 parts by mass of the hydroxyl group-containing tetrafluoroethylene-based resin.

[0070] The tensile breaking strength of the release film of Example 1 was measured at 175°C in accordance with JIS K7127 and was found to be 50 MPa. In addition, the tensile breaking elongation of the release film was measured at 175°C in accordance with JIS K7127 and was found to be 350%.

[0071] Example 2

[0072] A film made of easily moldable polyethylene terephthalate resin (Emblett CTK-38, Unitika Ltd., thickness 38 μm, glass transition temperature 65° C.) was prepared as a substrate layer. The first fluororesin composition described in Example 1 was applied to one side of the film, and the second fluororesin composition described in Example 1 was applied to the other side of the film. After the application, these compositions were cured by heating at 150° C. for 60 seconds, thereby obtaining a release film in which fluororesin layers were laminated on both sides of an easily moldable PET resin film (hereinafter referred to as the "release film of Example 2").

[0073] The thickness of the release film of Example 2 was 60±5 μm. The thickness of the base layer in the release film of Example 2 was 38 μm±10%. Of the two surface layers of the release film of Example 2, the surface layer formed from the cured product of the first fluororesin composition had a thickness of 5.5±0.5 μm. The surface layer formed from the cured product of the second fluororesin composition had a thickness of 5.5±0.5 μm.

[0074] The cured product of the first fluorine-based resin composition contained 17.65 parts by mass of the amorphous silicon dioxide, 15.39 parts by mass of the isocyanurate polyisocyanate, and 11.98 parts by mass of the adduct polyisocyanate, relative to 100 parts by mass of the hydroxyl group-containing tetrafluoroethylene resin.

[0075] The cured product of the second fluorine-based resin composition contained 17.65 parts by mass of the amorphous silicon dioxide, 15.39 parts by mass of the isocyanurate-type polyisocyanate, 11.98 parts by mass of the adduct-type polyisocyanate, and 0.48 parts by mass of amino-modified methylpolysiloxane, relative to 100 parts by mass of the hydroxyl group-containing tetrafluoroethylene-based resin.

[0076] The tensile breaking strength of the release film of Example 2 was measured at 175°C in accordance with JIS K7127 and was found to be 90 MPa. In addition, the tensile breaking elongation of the release film was measured at 175°C in accordance with JIS K7127 and was found to be 350%.

[0077] Example 3

[0078] A film made of easily moldable polyethylene terephthalate resin (Teflex FT3, Teijin Limited, thickness 25 μm, glass transition temperature 70° C.) was prepared as a substrate layer. The first fluororesin composition described in Example 1 was applied to one side of the film, and the second fluororesin composition described in Example 1 was applied to the other side of the film. After the application, these compositions were cured by heating at 150° C. for 60 seconds, thereby obtaining a release film in which fluororesin layers were laminated on both sides of an easily moldable PET resin film (hereinafter referred to as the "release film of Example 3").

[0079] The thickness of the release film of Example 3 was 49±5 μm. The thickness of the base layer in the release film of Example 3 was 25 μm±10%. Of the two surface layers of the release film of Example 3, the surface layer formed from the cured product of the first fluororesin composition had a thickness of 5.5±0.5 μm. The surface layer formed from the cured product of the second fluororesin composition had a thickness of 5.5±0.5 μm.

[0080] The cured product of the first fluorine-based resin composition contained 17.65 parts by mass of the amorphous silicon dioxide, 15.39 parts by mass of the isocyanurate polyisocyanate, and 11.98 parts by mass of the adduct polyisocyanate, relative to 100 parts by mass of the hydroxyl group-containing tetrafluoroethylene resin.

[0081] The cured product of the second fluorine-based resin composition contained 17.65 parts by mass of the amorphous silicon dioxide, 15.39 parts by mass of the isocyanurate-type polyisocyanate, 11.98 parts by mass of the adduct-type polyisocyanate, and 0.48 parts by mass of amino-modified methylpolysiloxane, relative to 100 parts by mass of the hydroxyl group-containing tetrafluoroethylene-based resin.

[0082] The tensile breaking strength of the release film of Example 3 was measured at 175°C in accordance with JIS K7127 and was found to be 40 MPa. In addition, the tensile breaking elongation of the release film was measured at 175°C in accordance with JIS K7127 and was found to be 550%.

[0083] (Comparative Example 1)

[0084] A film formed from a conventional polyethylene terephthalate resin (Tetoron G2CW, Teijin Limited, thickness 38 μm, glass transition temperature 100° C.) was prepared as a substrate layer. The first fluororesin composition described in Example 1 was applied to one side of the film, and the second fluororesin composition described in Example 1 was applied to the other side of the film. After the application, these compositions were cured by heating at 150° C. for 60 seconds, thereby obtaining a release film in which fluororesin layers were laminated on both sides of a moldable PET resin film (hereinafter referred to as the "release film of Comparative Example 1").

[0085] The thickness of the release film of Comparative Example 1 was 60±5 μm. The thickness of the base layer in the release film of Comparative Example 1 was 38 μm±10%. Of the two surface layers of the release film of Comparative Example 1, the surface layer formed from the cured product of the first fluororesin composition had a thickness of 5.5±0.5 μm. The surface layer formed from the cured product of the second fluororesin composition had a thickness of 5.5±0.5 μm.

[0086] The cured product of the first fluorine-based resin composition contained 17.65 parts by mass of the amorphous silicon dioxide, 15.39 parts by mass of the isocyanurate polyisocyanate, and 11.98 parts by mass of the adduct polyisocyanate, relative to 100 parts by mass of the hydroxyl group-containing tetrafluoroethylene resin.

[0087] The cured product of the second fluorine-based resin composition contained 17.65 parts by mass of the amorphous silicon dioxide, 15.39 parts by mass of the isocyanurate-type polyisocyanate, 11.98 parts by mass of the adduct-type polyisocyanate, and 0.48 parts by mass of amino-modified methylpolysiloxane, relative to 100 parts by mass of the hydroxyl group-containing tetrafluoroethylene-based resin.

[0088] The tensile breaking strength of the release film of Comparative Example 1 was measured at 175°C in accordance with JIS K7127 and was found to be 140 MPa. The tensile breaking elongation of the release film was also measured at 175°C in accordance with JIS K7127 and was found to be 350%.

[0089] (Mold contamination due to release film)

[0090] Using the release film of Comparative Example 1, an epoxy resin was transferred into a mold. The transfer molding was carried out as shown in FIG. 2 . The transfer molding was carried out so that the layer formed from the cured product of the first fluororesin composition was in contact with the mold and the layer formed from the cured product of the second fluororesin composition was in contact with the epoxy resin. Next, the same transfer molding was carried out again using the same release film. The same transfer molding was carried out two more times using the same release film, for a total of four transfer moldings using one release film.

[0091] After four molding cycles, a white substance was observed adhering to the mold. The white substance was analyzed using a Fourier transform infrared spectrometer (IRT-5000 Microscopic FT-IR, JASCO Corporation). As a result, the FT-IR spectrum shown in Figure 4 was obtained. The FT-IR spectrum revealed that the white substance was an oligomer (mainly a cyclic trimer) of ethylene terephthalate. In other words, it was found that the oligomer contained in the base layer formed from the PET resin passed through the surface layer formed from the cured product of the fluororesin composition and contaminated the mold. It was also found that the cured product was insufficient to prevent the oligomer from migrating to the mold and molded product.

[0092] Furthermore, of the four molding cycles, the mold-side surface of the release film after the first, second, and third molding cycles was observed using a scanning electron microscope (JSM-IT100 SEM, JEOL Ltd.). The results of the observation are shown in FIG. 5. FIG. 5 is an electron microscope photograph of a 1.2 mm × 0.8 mm area of ​​the release film. As shown in the left side of FIG. 5, oligomers precipitated in three locations after the first molding cycle. As shown in the center of FIG. 5, oligomers precipitated in five locations after the second molding cycle, and as shown in the right side of FIG. 5, oligomers precipitated in 10 locations after the third molding cycle. Therefore, it was found that as the number of molding cycles increased, more cyclic trimers migrated to the mold and molded product.

[0093] Using the release film of Example 1, epoxy resin transfer molding was performed four times, as in Comparative Example 1. The mold-side surface of the release film after the fourth molding was observed with a scanning electron microscope (JSM-IT100 SEM, JEOL Ltd.). The observation results are shown in FIG. 6. FIG. 6 is an electron microscope photograph of a 1.2 mm x 0.8 mm area of ​​the release film. As shown in FIG. 6, no precipitation of oligomers was observed even after the fourth molding. Therefore, by using a film formed from an easily moldable PET resin as the base layer, it is possible to prevent the oligomers from migrating to the mold and molded product.

[0094] For the release films of Examples 2 and 3, molding by transfer molding of an epoxy resin was performed four times, as in the case of Comparative Example 1. As a result, for both the release films of Examples 2 and 3, as with the release film of Example 1, no precipitation of oligomers was confirmed.

[0095] The presence or absence of oligomer precipitation was also tested when only the release film of Example 1 or Comparative Example 1 was heated. To confirm this, the release film of Example 1 or Comparative Example 1 was sandwiched between SUS (Steel Use Stainless) plates and heated on a hot plate at 175°C for 30 minutes. The surfaces of the release films of Example 1 and Comparative Example 1 after heating were observed under a microscope. A micrograph of Comparative Example 1 is shown in Figure 7. The left side of Figure 7 is a photograph at a magnification of 100x, and the right side of Figure 7 is a photograph at a magnification of 1000x. As can be seen from these photographs, it was confirmed that oligomers were precipitated after heating. A micrograph of Example 1 is shown in Figure 8. The left side of Figure 8 is a photograph at a magnification of 100x, and the right side of Figure 8 is a photograph at a magnification of 1000x. As can be seen from these photographs, no oligomer precipitation was confirmed after heating of the release film of Example 1.

[0096] Furthermore, from the results regarding oligomer precipitation and the glass transition temperatures of the base material layers contained in the release films of Examples 1 to 3 and Comparative Example 1, it is also considered that the glass transition temperature of the PET resin of the base material layer is within a specific numerical range (for example, 60°C to 95°C), which makes it possible to prevent oligomer precipitation.

[0097] The epoxy resin molded body was smoothly released from the release film in all four moldings using the release films of Examples 1 to 3. This demonstrates that the release films of Examples 1 to 3 have excellent releasability and that this releasability is maintained throughout multiple moldings.

[0098] (Release film multi-shot suitability)

[0099] As described above in "Mold Contamination by Release Films," the release films of Examples 1 to 3 could be used continuously for at least four moldings.

[0100] Furthermore, when the molding described above in "Mold Contamination by Release Film" was performed several times, the release films of Examples 1 and 2 broke on the 10th molding and the 10th molding, respectively. The release film of Example 3 broke on the 5th molding. Therefore, the release films of Examples 1 and 2 can be used for a greater number of moldings than the release film of Example 3. In other words, the release films of Examples 1 and 2 have better multi-shot suitability than the release film of Example 3.

[0101] As described above, the tensile breaking strength and tensile breaking elongation of the release film of Example 1 were 50 MPa and 350%, respectively. As described above, the tensile breaking strength and tensile breaking elongation of the release film of Example 2 were 90 MPa and 350%, respectively. On the other hand, as described above, the tensile breaking strength and tensile breaking elongation of the release film of Example 3 were 40 MPa and 550%, respectively.

[0102] From the above results of multi-shot suitability and tensile breaking strength and tensile breaking elongation, it can be seen that by adjusting the tensile breaking strength and tensile breaking elongation of the release film, it can be used for more molding operations.

[0103] As described above, the tensile strength and elongation at break of the release film of Comparative Example 1 were 140 MPa and 350%, respectively. When molding was further performed multiple times using the release film of Comparative Example 1, tearing occurred in the 10th molding.

[0104] Two commercially available release films were also prepared. The tensile strength and elongation at break of the first release film were measured using the above-mentioned methods and were found to be 7 MPa and 550%, respectively. The tensile strength and elongation at break of the second release film were measured using the above-mentioned methods and were found to be 26 MPa and 130%, respectively. These two release films were used to attempt multiple moldings as described above. As a result, the first release film broke on the third molding run. The second release film broke on the second molding run.

[0105] The results of the multi-shot suitability for the release films of Examples 1 to 3 and Comparative Example 1 and the above-mentioned commercially available release films (hereinafter referred to as commercially available release films 1 and 2) and the tensile breaking strength and tensile breaking elongation of these films show that if the tensile breaking strength and tensile breaking elongation of the release film are within a specific numerical range (for example, 40 MPa to 200 MPa and 200% to 500%), the film can be used for a greater number of molding operations.

[0106] To facilitate a comparison of the above results for the release films of Examples 1 to 3 and Comparative Example 1 and the commercially available release films 1 and 2, these results are summarized in Table 1 below. The evaluation criteria for multi-shot suitability in Table 1 are as follows: AA: Did not break even after being used for five or more moldings. A: Did not break even after being used for three or more moldings. B: Broke during the third molding. C: Broke during the second molding.

[0107]

[0108] (gas permeability)

[0109] The oxygen gas permeability of the release film of Example 1 was measured at 175°C in accordance with JIS K7126-1. The measurement result was 10,000 cc / m2 The oxygen gas permeability was measured in the same manner for commercially available release films 1 and 2. As a result, the oxygen gas permeabilities of commercially available release films 1 and 2 were 142,000 and 130,000 cc / m, respectively. 2 24 hr·atm. Therefore, it is clear that the release film of Example 1 is also excellent in oxygen gas permeability.

[0110] 100 Release film 101 Base layer 102 Surface layer 103 Surface layer

Claims

------08 / 04 / 2019------(OCR)1. Backing film consisting of: a base layer made of easily moldable polyethylene terephthalate resin; and a double-sided coating layer on the base layer formed with fluororesin.

2. Backing film under claim 1, in which the easily moldable polyethylene terephthalate resin has a glass transition temperature of 60°C to 95°C.

3. Backing film under claim 1 or 2, in which the backing film has a tensile strength under the condition The tensile strength at break of 40 MPa to 200 MPa as specified at 175°C according to JISK7127, and the backing film has a tensile strength at break of 200% to 500% as specified at 175°C according to JISK71274. The backing film under any one of claims 1 to 3, where the backing film has an oxygen permeability of 5,000 to 50,000 cc / m²-24 hours-atmosphere as specified at 175°C according to JISK7126-15.Backing film under any of Requisitions 1 to 4, where the base layer has a tensile strength at break of 40 MPa to 200 MPa as specified at 175°C according to JISK 71276. Backing film under any of Requisitions 1 to 5, where the base layer has a tensile elongation at break of 200% to 500% as specified at 175°C according to JISK 71277. Backing film under any of Requisitions 1 to 6, where fluororesin forms at least one superficial layer of the base layer containing the substance.

8. Backing film under any of the claims 1 to 7, in which the fluororesin forming the superficial layer of a base layer composed of particles with an average particle size of 1 µm to 10 µm determined by particle size analysis by optical diffraction; 9. Backing film under any of the claims 1 to 8, in which the fluororesin forming the superficial layer is composed of tetrafluoroethylene resin; 10. Backing film under any of the claims 1 to 9, for use in injection molding or compression molding; 11.Backing film under any one of claims 1 to 10, for use in two or more molding cycles.

12. Method of manufacturing the backing film, which includes: the application step of applying the fluororesin component to two faces of a base layer made of easily moldable polyethylene terephthalate resin; and after the application step, the curing step to cure the fluororesin component.