Release film

Abstract

The present invention relates to a release film having a substrate, an antistatic layer, and a release layer in this order, wherein the release layer contains at least one conductive material selected from a conductive polymer, an ionic liquid, a surfactant, a conductive metal oxide, a metal-ion-conductive salt, and a conductive carbon material.

Description

Release film

[0001] This invention relates to a release film.

[0002] Semiconductor packages have a resin encapsulation section that protects the semiconductor elements. Curable resins, such as thermosetting epoxy resins, are widely used to form the resin encapsulation section. As methods for encapsulating semiconductor elements, so-called compression molding and transfer molding methods are known, in which a substrate on which semiconductor elements are mounted is placed in the cavity of a mold, and the cavity is filled with curable resin to form the resin encapsulation section. In these encapsulation methods, so-called Film-Assisted Molding (FAM) methods are usually employed, in which a release film is placed on the cavity surface of the mold to prevent the resin encapsulation section from sticking to the mold.

[0003] In recent years, semiconductor devices have become highly integrated, more complex in structure, and narrower in line width. When such semiconductor devices are sealed using a release film, electrostatic discharge (ESD) damage to the semiconductor device is more likely to occur due to the slight static electricity generated when peeling the release film from the resin encapsulation area. Therefore, efforts are being made to suppress the generation of static electricity by imparting antistatic properties to the release film. Patent Document 1 describes a release film having a first thermoplastic resin layer, an intermediate layer containing a conductive material, and a second thermoplastic resin layer. Patent Document 2 describes a release film for semiconductor molding having a release layer, a conductive layer, and a base layer in that order, wherein the release layer contains metal particles.

[0004] International Publication No. 2015 / 133630, Japanese Patent Publication No. 2024-69134

[0005] However, the release film described in Patent Document 1 had room for improvement in terms of antistatic performance. Furthermore, the release film described in Patent Document 2 may show transfers originating from the release film on the cured resin surface after release, indicating room for improvement in terms of transfer prevention. The object of the present invention is to provide a release film that has excellent antistatic performance to prevent electrostatic discharge damage to semiconductor devices, and also has excellent transfer prevention after release.

[0006] The present invention relates to the following release film: A release film having a base material, an antistatic layer, and a release layer in that order, wherein the release layer contains at least one conductive material selected from conductive polymers, ionic liquids, surfactants, conductive metal oxides, metal ion conductive salts, and conductive carbon materials.

[0007] According to the present invention, it is possible to provide a release film that has excellent antistatic properties and excellent transfer prevention properties after release.

[0008] Figure 1 is a cross-sectional view of a release film according to an embodiment of the present invention.

[0009] The embodiments of the present invention (hereinafter also referred to as "these embodiments") will be described in detail below. However, the present invention is not limited to the following embodiments. In the present invention, the numerical range indicated using "~" includes the numerical values ​​written before and after "~" as the minimum and maximum values, respectively.

[0010] In this specification, "(meth)acrylic polymer" refers to a polymer having units based on (meth)acrylate. The (meth)acrylic polymer may contain one or more (meth)acrylate-based units. The (meth)acrylic polymer may further contain units based on other monomers other than (meth)acrylate-based units. In this specification, "(meth)acrylate" is a general term for acrylate and methacrylate. "(meth)acrylic acid" is a general term for acrylic acid and methacrylic acid.

[0011] In this specification, the arithmetic mean roughness Ra is measured in accordance with JIS B0601:2013 (ISO 4287:1997, Amd. 1:2009). A surface roughness measuring instrument is used for measurement, and the ambient temperature is 23 to 25°C.

[0012] In this specification, the ten-point mean roughness Rz is measured in accordance with JIS B0601:2013 (ISO 4287:1997, Amd. 1:2009). A surface roughness measuring instrument is used for the measurement, and the ambient temperature is 23 to 25°C.

[0013] <Release Film> The release film according to this embodiment comprises a substrate, an antistatic layer, and a release layer in that order, wherein the release layer contains at least one conductive material selected from conductive polymers, ionic liquids, surfactants, conductive metal oxides, metal ion conductive salts, and conductive carbon materials. By having a conductive material in the release layer, the surface of the release film on the release layer side, i.e., the surface in contact with the curable resin, can be made less resistive. As a result, the antistatic performance can be effectively enhanced while maintaining the release properties of the release film. This is presumed to be because the resistance component of the surface layer is dominant in the resistance contribution of surface resistance, so the antistatic performance of the entire release film can be enhanced by making the release layer less resistive rather than making the antistatic layer itself less resistive. Furthermore, by having a specific conductive material in the release layer, a release film with excellent transfer prevention after release can be obtained.

[0014] An example of the structure of the release film according to this embodiment will be described using the drawings. Figure 1 is a schematic cross-sectional view showing an example of the release film according to this embodiment.

[0015] The release film 10 shown in Figure 1 has a base material 1, an antistatic layer 2, and a release layer 3 in that order. In the release film 10 of Figure 1, the antistatic layer 2 is laminated on the first surface 1A of the base material.

[0016] (Base Material) The material (composition) constituting the base material is not particularly limited, and known materials such as resins used for release films can be applied. As for the resin used in the base material, it is preferable to include a resin with release properties in order to ensure excellent release of the release film from the mold after sealing. A resin with release properties means a resin in which a layer consisting solely of that resin has release properties. Examples of resins with release properties include fluororesins, polymethylpentene, syndiotactic polystyrene, polycycloolefin, silicone rubber, polyester elastomer, polyethylene terephthalate, polybutylene terephthalate, and unoriented nylon. From the viewpoint of release from the mold, heat resistance at the mold temperature during sealing (e.g., 180°C), strength to withstand the flow and pressure of the curable resin, and elongation at high temperatures, fluororesins, polymethylpentene, syndiotactic polystyrene, polycycloolefin, polyethylene terephthalate, and polybutylene terephthalate are preferred, and fluororesins are particularly preferred in terms of excellent release properties. In other words, it is preferable for the base material to include a fluororesin. These resins may be used individually or in combination of two or more types.

[0017] The substrate may consist of a single layer or a laminate of multiple layers. When the substrate is a laminate, a combination of a fluororesin layer and other resin layers is preferred in terms of excellent release properties. For example, a two-layer structure of another resin layer / fluororesin layer, or a three-layer structure of fluororesin layer / other resin layer / fluororesin layer is preferred. When the substrate is a laminate, it is preferable that each layer is laminated via an adhesive layer.

[0018] As the polymethylpentene, a homopolymer or copolymer of 4-methyl-1-pentene is preferred. The 4-methyl-1-pentene copolymer may be a copolymer of 4-methyl-1-pentene and other olefins having 2 to 20 carbon atoms (hereinafter referred to as "olefins having 2 to 20 carbon atoms"). Examples of olefins having 2 to 20 carbon atoms include ethylene, propylene, 1-butene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, and 1-eicosene. These olefins may be used individually or in combination of two or more. In the copolymer of 4-methyl-1-pentene and an olefin having 2 to 20 carbon atoms, it is preferable that the proportion of units based on 4-methyl-1-pentene is 96 to 99% by mass, and the proportion of units based on other olefins having 2 to 20 carbon atoms is 1 to 4% by mass.

[0019] Examples of syndiotactic polystyrene resins include polystyrene, poly(p-methylstyrene), poly(m-methylstyrene), poly(p-t-butylstyrene), poly(p-chlorostyrene), poly(m-chlorostyrene), poly(p-fluorostyrene), hydrogenated polystyrene, and copolymers containing these structural units, all of which have a syndiotactic structure, with syndiotactic polystyrene or syndiotactic poly(p-methylstyrene) being preferred.

[0020] The fluororesin content in the total resin contained in the base material is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, particularly preferably 99% by mass or more, and may be 100% by mass. As the fluororesin, fluoroolefin polymers are preferred from the viewpoint of excellent release properties and heat resistance. Fluoroolefin polymers are polymers having units based on fluoroolefins. Fluoroolefin polymers may further have other units besides those based on fluoroolefins.

[0021] Examples of fluoroolefins include tetrafluoroethylene (hereinafter also referred to as "TFE"), vinyl fluoride, vinylidene fluoride, trifluoroethylene, hexafluoropropylene, and chlorotrifluoroethylene. Fluoroolefins may be used individually or in combination of two or more. Examples of fluoroolefin polymers include ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer (PFA), and tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (THV). Fluoroolefin polymers may be used individually or in combination of two or more. ETFE is particularly preferred as a fluoroolefin polymer due to its high elongation at high temperatures. ETFE is a copolymer having TFE units and ethylene units (hereinafter also referred to as "E units"). That is, ETFE is preferred as the fluororesin contained in the substrate.

[0022] ETFE may have units based on a third monomer in addition to TFE units and E units. The third monomer may be used alone or in combination of two or more types. Examples of the third monomer include monomers having fluorine atoms and monomers not having fluorine atoms.

[0023] Examples of monomers containing a fluorine atom include the following monomers (a1) to (a5). Monomer (a1): Fluoroolefins having 2 or 3 carbon atoms. Monomer (a2): X(CF ２ ) ｎ CY = CH ２ Fluoroalkylethylenes represented by (wherein X and Y are independently a hydrogen atom or a fluorine atom, and n is an integer from 2 to 8). Monomer (a3): Fluorovinyl ethers. Monomer (a4): Functional group-containing fluorovinyl ethers. Monomer (a5): Fluorine-containing monomers having an aliphatic ring structure.

[0024] As the monomer (a1), fluoroethylenes (trifluoroethylene, vinylidene fluoride, vinyl fluoride, chlorotrifluoroethylene, etc.), fluoropropylenes (hexafluoropropylene (hereinafter also referred to as "HFP"), 2 - hydroperfluoropropylene, etc.) and the like can be mentioned.

[0025] As the monomer (a2), monomers with n being 2 to 6 are preferable, and monomers with n being 2 to 4 are particularly preferable. In addition, a monomer in which X is a fluorine atom and Y is a hydrogen atom, that is, (perfluoroalkyl) ethylene is particularly preferable. Specific examples of the monomer (a2) include the following compounds. CF ３ CF ２ CH=CH ２ , CF ３ CF ２ CF ２ CF ２ CH=CH ２ ((perfluorobutyl) ethylene. Hereinafter, also referred to as "PFBE"). CF ３ CF ２ CF ２ CF ２ CF=CH ２ , CF ２ HCF ２ CF ２ CF=CH ２ , CF ２ HCF ２ CF ２ CF ２ CF=CH ２ etc.

[0026] Specific examples of the monomer (a3) include the following compounds. Among the following, monomers that are dienes are monomers that can undergo cyclopolymerization. CF ２ =CFOCF ３ , CF ２ =CFOCF ２ CF ３ , CF ２ =CFO(CF ２ ) ２ CF ３ (perfluoro(propyl vinyl ether). Hereinafter, also referred to as "PPVE"). CF ２ =CFOCF ２CF (CF ３ ) O (CF ２ ) ２ CF ３ CF ２ = CFO (CF ２ ) ３ O(CF) ２ ) ２ CF ３ CF ２ = CFO (CF ２ CF (CF ３ )O) ２ (CF ２ ) ２ CF ３ CF ２ = CFOCF ２ CF (CF ３ ) O (CF ２ ) ２ CF ３ CF ２ = CFOCF ２ CF = CF ２ CF ２ = CFO (CF ２ ) ２ CF = CF ２ etc.

[0027] Specific examples of monomers (a4) include the following compounds: CF ２ = CFO (CF ２ ) ３ CO ２ CH ３ CF ２ = CFOCF ２ CF (CF ３ ) O (CF ２ ) ３ CO ２ CH ３ CF ２ = CFOCF ２ CF (CF ３ ) O (CF ２ ) ２ SO ２ F etc.

[0028] Specific examples of monomers (a5) include perfluoro(2,2-dimethyl-1,3-dioxol), 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxol, and perfluoro(2-methylene-4-methyl-1,3-dioxolane).

[0029] Examples of monomers that do not contain a fluorine atom include the following monomers (b1) to (b4): Monomer (b1): Olefins, Monomer (b2): Vinyl esters, Monomer (b3): ​​Vinyl ethers, Monomer (b4): Unsaturated acid anhydrides. Specific examples of monomer (b1) include propylene and isobutene. Specific examples of monomer (b2) include vinyl acetate. Specific examples of monomer (b3) include ethyl vinyl ether, butyl vinyl ether, cyclohexyl vinyl ether, and hydroxybutyl vinyl ether.

[0030] Specific examples of monomers (b4) include maleic anhydride, itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic acid anhydride.

[0031] As the third monomer, monomer (a2), HFP, PPVE, and vinyl acetate are preferred due to their ease of adjusting the degree of crystallinity and their excellent tensile strength and elongation at high temperatures (especially around 180°C). ３ CF ２ CH=CH ２ PFBE is more preferred, and PFBE is even more preferred. In other words, as ETFE, a copolymer having TFE units, E units, and PFBE-based units (hereinafter also referred to as "PFBE units") is particularly preferred.

[0032] In ETFE, the molar ratio of TFE units to E units (TFE units / E units) is preferably 80 / 20 to 40 / 60, more preferably 70 / 30 to 45 / 55, and particularly preferably 65 / 35 to 50 / 50. When the TFE units / E units are within the above range, ETFE exhibits excellent heat resistance and mechanical strength. The proportion of units based on the third monomer in ETFE is preferably 0.01 to 20 mol%, more preferably 0.10 to 15 mol%, and particularly preferably 0.20 to 10 mol%, relative to the total amount of all units constituting ETFE (100 mol%). When the proportion of units based on the third monomer is within the above range, ETFE exhibits excellent heat resistance and mechanical strength.

[0033] When the units based on the third monomer include PFBE units, the proportion of PFBE units is preferably 0.5 to 4.0 mol%, more preferably 0.7 to 3.6 mol%, and particularly preferably 1.0 to 3.6 mol%, relative to the total amount of all units constituting ETFE (100 mol%). When the proportion of PFBE units is within the above range, the tensile strength and elongation at high temperatures (especially around 180°C) are improved.

[0034] The melting point of ETFE is preferably 190°C or higher, more preferably 200°C or higher, even more preferably 210°C or higher, and particularly preferably 220°C or higher. The upper limit of the melting point of ETFE is not particularly limited, but for example, it is 270°C. When the melting point of ETFE is within this range, the release film tends to have excellent tensile strength and elongation at high temperatures (especially around 180°C). "Melting point" refers to the temperature corresponding to the maximum value of the melting peak measured by differential scanning calorimetry (DSC). The melt flow rate (MFR) of ETFE is preferably 2 to 40 g / 10 min, more preferably 3 to 30 g / 10 min, and particularly preferably 5 to 20 g / 10 min. When the MFR of ETFE is within this range, the elongation of the release film at high temperatures increases, and it tends to have excellent conformability to the mold. The MFR of ETFE is a value measured in accordance with ASTM D3159 at a load of 49 N and 297°C.

[0035] The base material may further contain other components besides the resin. Examples of other components include lubricants, antioxidants, antistatic agents, plasticizers, and mold release agents. In terms of minimizing mold contamination, the content of other components in the base material is preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass, and particularly preferably 0% by mass (not included).

[0036] Of the two surfaces of the substrate, the surface on which the antistatic layer is laminated is referred to as the first surface of the substrate, and the other surface is referred to as the second surface of the substrate. The first surface of the substrate may be a mirror surface or a matte surface with an uneven shape. The shape of the first surface of the substrate affects the shape of the surface (first surface) on the release layer side of the release film. The surface on the release layer side of the release film is transferred to the surface of the semiconductor package when the semiconductor element is sealed using the release film to obtain a semiconductor package. Therefore, the shape of the first surface should be selected according to the shape of the semiconductor package to be obtained, but a matte surface with an uneven shape is preferable because it is easier to print information such as the part number and QR code (registered trademark) on the semiconductor package using laser marking.

[0037] When the first surface of the substrate is mirror-finished, it means that the arithmetic mean roughness Ra of the surface on the first surface of the substrate is 0.15 μm or less. The lower limit of the arithmetic mean roughness Ra is not particularly limited, but it is preferably 0.02 μm or more from the viewpoint of adhesion with the antistatic layer. Furthermore, when the first surface of the substrate is mirror-finished, it means that the ten-point mean roughness Rz of the surface on the first surface of the substrate is 0.6 μm or less. The lower limit of the ten-point mean roughness Rz is not particularly limited, but it is preferably 0.1 μm or more from the viewpoint of adhesion with the antistatic layer.

[0038] When the first surface of the substrate is a matte surface with an uneven shape, the arithmetic mean roughness Ra is preferably 4.0 μm or less, more preferably 3.0 μm or less, even more preferably 2.5 μm or less, and particularly preferably 2.0 μm or less, from the viewpoint of the visibility of laser marking on the semiconductor package obtained using the release film. The arithmetic mean roughness Ra is preferably greater than 0.15 μm, more preferably 0.2 μm or more, even more preferably 0.8 μm or more, and particularly preferably 1.5 μm or more, from the viewpoint of adhesion with the antistatic layer. Furthermore, when the first surface of the substrate is a matte surface with an uneven shape, the ten-point average roughness Rz is preferably 20 μm or less, more preferably 15 μm or less, even more preferably 12.5 μm or less, and particularly preferably 9.0 μm or less, from the viewpoint of the visibility of laser marking on the semiconductor package obtained using the release film. The ten-point average roughness Rz is preferably greater than 0.6 μm, more preferably 1.0 μm or more from the viewpoint of adhesion with the antistatic layer, even more preferably 4.0 μm or more, and particularly preferably 7.0 μm or more.

[0039] The second surface of the substrate may be a matte surface with an uneven shape or a mirror surface, but it is preferable to have a matte surface with an uneven shape from the viewpoint of mold conformability and suppression of wrinkle formation when adsorbed to a mold. From the viewpoint of mold conformability and suppression of wrinkle formation when adsorbed to a mold, the arithmetic mean roughness Ra of the second surface of the substrate is preferably 4.0 μm or less, more preferably 3.0 μm or less, and even more preferably 2.5 μm or less. The lower limit of the arithmetic mean roughness Ra is not particularly limited, but it is preferably 0.2 μm or more from the viewpoint of excellent slipperiness to the mold and suppression of wrinkle formation when used as a release film.

[0040] The second surface of the substrate has a ten-point average roughness Rz of 20 μm or less, more preferably 15 μm or less, and even more preferably 12.5 μm or less, from the viewpoint of mold conformability and suppression of wrinkle formation when adsorbed to the mold. The lower limit of the ten-point average roughness Rz is not particularly limited, but when used as a release film, it is preferably 1.0 μm or more from the viewpoint of excellent slipperiness to the mold and suppression of wrinkle formation.

[0041] The arithmetic mean roughness Ra and ten-point mean roughness Rz of the substrate surface may be measured after removing the release layer and antistatic layer from the release film, respectively. The release layer and antistatic layer can be removed by impregnating the release film with a solvent and rubbing the surface with a melamine sponge. The type of solvent and impregnation time should be selected according to the materials of the antistatic layer and release layer of the release film, but one example is impregnation with ethyl acetate for 4 hours.

[0042] The average thickness of the substrate is preferably 35 to 250 μm, and more preferably 35 to 110 μm. A substrate thickness of 35 μm or more is preferable because the release film tends to have excellent release properties. A substrate thickness of 250 μm or less is preferable because the release film is easily deformable and has excellent mold conformability. A substrate thickness of 250 μm or less is preferable because the release film is easy to handle (for example, roll-to-roll handling) and wrinkles are less likely to occur when the release film is positioned to cover the mold cavity while being stretched.

[0043] The average thickness of the substrate is determined by observing the cross-section of the release film using a focused ion beam scanning electron microscope (FIB-SEM). In FIB-SEM, the boundaries between layers can be determined from the difference in contrast between layers, and the thickness of each layer can be measured. Such measurements are performed at 30 randomly selected locations, or at least 30 locations between concave and convex areas if surface irregularities are observed, and the average thickness of each layer can be determined by averaging the measurement results.

[0044] (Antistatic layer) The antistatic layer is not particularly limited in material as long as it has an antistatic function. The antistatic layer preferably contains an antistatic agent. Examples of antistatic agents include conductive polymers, ionic liquids, surfactants, conductive metal oxides, metal ion conductive salts, and conductive carbon materials. Specific examples and preferred embodiments of conductive polymers, ionic liquids, surfactants, conductive metal oxides, metal ion conductive salts, and conductive carbon materials are the same as the specific examples and preferred embodiments of conductive materials included in the release layer described later, except that the antistatic agent is preferably a conductive polymer.

[0045] The antistatic agent is preferably a conductive polymer, from the viewpoint of excellent dispersibility in the antistatic layer and excellent antistatic performance of the release film. Examples of conductive polymers include polyaniline polymers, polyacetylene polymers, poly-p-phenylene polymers, polypyrrole polymers, polythiophene polymers, and polyvinylcarbazole polymers. Polythiophene polymers are more preferably used, from the viewpoint of excellent dispersibility in the antistatic layer and excellent antistatic performance of the release film.

[0046] The antistatic layer preferably contains a resin binder. If the antistatic layer contains both a resin binder and an antistatic agent, it is preferable that the antistatic agent is dispersed in the resin binder. The resin binder is preferably one that has heat resistance to withstand the heat (e.g., 180°C) during the sealing process, and examples include acrylic resin, silicone resin, urethane resin, polyester resin, polyamide resin, vinyl acetate resin, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, chlorotrifluoroethylene-vinyl alcohol copolymer, tetrafluoroethylene-vinyl alcohol copolymer, and the like.

[0047] The resin binder may be crosslinked. When the resin binder is crosslinked, it has superior heat resistance compared to when it is not crosslinked.

[0048] In this embodiment, from the viewpoint of coating strength and durability, the resin binder is preferably a reaction-cured product of a carboxyl group-containing (meth)acrylic polymer and at least one selected from the group consisting of a bifunctional or more aziridine compound (hereinafter also referred to as a "polyfunctional aziridine compound") and a bifunctional or more epoxy compound (hereinafter also referred to as a "polyfunctional epoxy compound"). In this case, the carboxyl group-containing (meth)acrylic polymer reacts with at least one selected from the group consisting of a polyfunctional aziridine compound and a polyfunctional epoxy compound to crosslink and become a reaction-cured product. The antistatic layer may be a reaction-cured product of a carboxyl group-containing (meth)acrylic polymer, at least one selected from the group consisting of a polyfunctional aziridine compound and a polyfunctional epoxy compound, and other components.

[0049] The ratio of units based on carboxyl group-containing (meth)acrylic monomers to the total carboxyl group-containing (meth)acrylic polymer is not particularly limited, but is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more.

[0050] The carboxyl groups in a carboxyl group-containing (meth)acrylic polymer are crosslinking functional groups that react with aziridine groups in a polyfunctional aziridine compound or epoxy groups in a polyfunctional epoxy compound. The acid value of the carboxyl group-containing (meth)acrylic polymer is preferably 1 to 80 mg KOH / g, more preferably 1 to 40 mg KOH / g, even more preferably 1 to 30 mg KOH / g, and particularly preferably 5 to 30 mg KOH / g. The acid value of the carboxyl group-containing (meth)acrylic polymer serves as an indicator of the ease of crosslinking when reacting with a polyfunctional aziridine compound or a polyfunctional epoxy compound. An acid value below the upper limit is preferable because it provides excellent stretchability of the antistatic layer. An acid value above the lower limit is preferable because it provides excellent adhesion of the antistatic layer. When multiple types of carboxyl group-containing (meth)acrylic polymers are used in the antistatic layer, the above range of acid value is the preferred range of acid value for all of the multiple types of carboxyl group-containing (meth)acrylic polymers. The acid value of carboxyl group-containing (meth)acrylic polymers is measured by the method specified in JIS K0070:1992.

[0051] In a carboxyl group-containing (meth)acrylic polymer, the carboxyl group may be present in the side chain, at the end of the main chain, or in both the side chain and the main chain. It is preferable that it be present in at least the side chain, as this allows for easy adjustment of the carboxyl group content.

[0052] Examples of carboxyl group-containing (meth)acrylic polymers in which a carboxyl group is present in the side chain include (meth)acrylic polymers having units based on a carboxyl group-containing monomer. Examples of carboxyl group-containing monomers include carboxyl group-containing (meth)acrylic monomers. Examples of carboxyl group-containing (meth)acrylic monomers include carboxyl group-containing (meth)acrylate and (meth)acrylic acid. Examples of carboxyl group-containing (meth)acrylate include ω-carboxy-polycaprolactone mono(meth)acrylate and mono-2-((meth)acryloyloxy)ethyl succinic acid. These monomers may be used individually or in combination of two or more.

[0053] Carboxyloid (meth)acrylic polymers may consist solely of units based on carboxyloid monomers, or they may further contain units based on monomers other than carboxyloid monomers. Examples of monomers other than carboxyloid monomers include (meth)acrylates that do not contain hydroxyl groups or carboxyloid groups, and hydroxylloid (meth)acrylates. These monomers may be used individually or in combination of two or more.

[0054] Examples of (meth)acrylates that do not contain hydroxyl and carboxyl groups include alkyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, toluyl (meth)acrylate, benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, glycidyl (meth)acrylate, 2-aminoethyl (meth)acrylate, 3-(methacryloyloxypropyl)trimethoxysilane, trifluoromethylmethyl (meth)acrylate, and 2-trifluoromethylethyl (meth)acrylate. Examples include rilate, 2-perfluoroethylethyl (meth)acrylate, 2-perfluoroethyl-2-perfluorobutylethyl (meth)acrylate, 2-perfluoroethyl (meth)acrylate, perfluoromethyl (meth)acrylate, diperfluoromethylmethyl (meth)acrylate, 2-perfluoromethyl-2-perfluoroethylmethyl (meth)acrylate, 2-perfluorohexylethyl (meth)acrylate, 2-perfluorodecylethyl (meth)acrylate, and 2-perfluorohexadecylethyl (meth)acrylate.

[0055] Preferably, alkyl (meth)acrylates are compounds in which the alkyl group has 1 to 12 carbon atoms, and examples include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, and dodecyl (meth)acrylate.

[0056] Examples of hydroxyl group-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1,4-cyclohexanedimethanol monoacrylate, and 2-acryloyloxyethyl-2-hydroxyethyl-phthalic acid.

[0057] The mass-average molecular weight (hereinafter also referred to as "Mw") of the carboxyl group-containing (meth)acrylic polymer is preferably 10,000 to 1,000,000, more preferably 50,000 to 800,000, and even more preferably 100,000 to 600,000. When Mw is above the lower limit, the strength of the antistatic layer is excellent. When Mw is below the upper limit, the extensibility of the antistatic layer is excellent. The Mw of the carboxyl group-containing (meth)acrylic polymer is a polystyrene-converted value obtained by measuring it by gel permeation chromatography using a calibration curve prepared using standard polystyrene samples with known molecular weights.

[0058] A polyfunctional aziridine compound is a compound having two or more aziridine groups in one molecule. From the viewpoint of not increasing the crosslinking density of the antistatic layer too much and obtaining high extensibility, the number of aziridine groups in a polyfunctional aziridine compound is preferably 6 or less, and particularly preferably 3 or less. Examples of polyfunctional aziridine compounds include 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate], 4,4-bis(ethyleneiminocarbonylamino)diphenylmethane, and trimethylolpropane-tris(β-aziridinyl)propionate. A polyfunctional aziridine compound may be used alone or in combination of two or more.

[0059] The polyfunctional aziridine compound may be a commercially available product. Examples of commercially available products include Aracoat CL910 (trade name) manufactured by Arakawa Chemical Industries, Ltd., Chemitight® DZ-22E (trade name) manufactured by Nippon Shokubai Co., Ltd., and Chemitight® PZ-33 (trade name) manufactured by Nippon Shokubai Co., Ltd.

[0060] From the viewpoint of obtaining high extensibility without excessively increasing the crosslinking density of the antistatic layer, the aziridine equivalent of the polyfunctional aziridine compound is preferably 50 g / eq or more, more preferably 75 g / eq or more, and even more preferably 100 g / eq or more. From the viewpoint of increasing the strength of the antistatic layer, the aziridine equivalent of the polyfunctional aziridine compound is preferably 300 g / eq or less, and more preferably 250 g / eq or less. From this viewpoint, the aziridine equivalent of the polyfunctional aziridine compound is preferably 75 to 250 g / eq, and more preferably 100 to 200 g / eq.

[0061] A polyfunctional epoxy compound is a compound having two or more epoxy groups in one molecule. From the viewpoint of not increasing the crosslinking density of the antistatic layer too much and obtaining high extensibility, the number of epoxy groups in a polyfunctional epoxy compound is preferably 6 or less, and particularly preferably 3 or less. Examples of polyfunctional epoxy compounds include N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, resorcinol diglycidyl ether, and glycerol polyglycidyl ether. Epoxy compounds may be used individually or in combination of two or more.

[0062] The polyfunctional epoxy compound may be a commercially available product. Examples of commercially available products include TETRAD-X (trade name) and TETRAD-C (trade name) from Mitsubishi Gas Chemical Company, and Denacol® EX-201 (trade name) and Denacol® EX-313 (trade name) from Nagase ChemteX Corporation.

[0063] From the viewpoint of obtaining high extensibility without excessively increasing the crosslinking density of the antistatic layer, the epoxy equivalent of the polyfunctional epoxy compound is preferably 30 g / eq or more, more preferably 50 g / eq or more, and even more preferably 90 g / eq or more. From the viewpoint of increasing the strength of the antistatic layer, the epoxy equivalent of the polyfunctional epoxy compound is preferably 300 g / eq or less, more preferably 200 g / eq or less, even more preferably 150 g / eq or less, and particularly preferably 120 g / eq or less. From this viewpoint, the epoxy equivalent of the polyfunctional epoxy compound is preferably 30 to 300 g / eq, more preferably 50 to 200 g / eq, and even more preferably 90 to 120 g / eq.

[0064] The total proportion of aziridine groups of the polyfunctional aziridine compound and epoxy groups of the polyfunctional epoxy compound with respect to 100 mol% of the carboxyl groups of the carboxyl group-containing (meth)acrylic polymer is preferably 15 to 130 mol%, and particularly preferably 25 to 60 mol%. When the total proportion of aziridine groups and epoxy groups is below the above upper limit value, the crosslinking density becomes sufficiently low, and the stretchability of the antistatic layer is excellent. When the total proportion of aziridine groups and epoxy groups is above the above lower limit value, the crosslinking density becomes sufficiently high, and the strength of the antistatic layer is excellent.

[0065] The surface resistivity of the antistatic layer is preferably 1 × 10 １０ Ω / sq or less, and more preferably 1 × 10 ９ Ω / sq or less. The lower limit value of the surface resistivity of the antistatic layer is not particularly limited, but it may be 1 × 10 ７ Ω / sq or more. Within the above range, the antistatic function on the surface of the release film is exhibited, and it becomes easier to prevent electrostatic breakdown of the semiconductor element. The content of the antistatic agent in the antistatic layer is appropriately set so that the surface resistivity of the antistatic layer falls within the above range.

[0066] From the viewpoint of reducing the surface resistivity of the first surface (the surface on the release layer side) of the release film while maintaining the releasability, the average thickness of the antistatic layer is preferably 0.05 to 3 μm, and more preferably 0.05 to 2 μm. The average thickness of the antistatic layer and the average thickness of the release layer described later are obtained by observing the cross section of the release film using a focused ion beam scanning electron microscope (FIB-SEM). In FIB-SEM, the boundary of the layer can be determined from the difference in contrast between layers, and the thickness of each layer can be measured. Such measurement is performed at 30 randomly selected locations. When surface unevenness is observed, at least 30 locations from the concave part to the convex part are used, and the average thickness of each layer can be obtained by averaging the measurement results. When there is no difference in contrast between the antistatic layer and the release layer during cross-sectional observation by FIB-SEM and it is difficult to distinguish the boundary of the layer, a scanning transmission electron microscope (STEM-EDX) is used to distinguish the boundary of the layer based on the presence or absence of characteristic elements in the antistatic layer (particularly, the antistatic agent contained in the antistatic layer) and the release layer.

[0067] (Release layer) The release layer is preferably a layer that has the function of assisting electron conduction to the antistatic layer.

[0068] The release layer includes at least one conductive material selected from conductive polymers, ionic liquids, surfactants, conductive metal oxides, metal ion conductive salts, and conductive carbon materials. This makes it easier for the release layer to have the function of assisting electron conduction to the antistatic layer.

[0069] Conductive polymers are polymers in which electrons move and diffuse along the polymer backbone (polymer skeleton). Examples of conductive polymers include polyaniline polymers, polyacetylene polymers, poly(p-phenylene) polymers, polypyrrole polymers, polythiophene polymers, and polyvinylcarbazole polymers.

[0070] Examples of ionic liquids include ammonium-based ions such as imidazolium salts and pyridinium salts, phosphonium-based ions, and neutral ions. Examples of anions include halogen-based ions such as bromide ions and triflate, boron-based ions such as tetraphenylborate, and phosphorus-based ions such as hexafluorophosphate.

[0071] Surfactants exert their antistatic effect by absorbing moisture from the air through their hydrophilic groups. The surfactant may be nonionic or ionic. Examples of ionic surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants, with cationic surfactants being preferred from the viewpoint of the antistatic performance of the release film.

[0072] One type of surfactant may be used, or two or more types may be used. When two or more types are used, excellent kneadability, bleed-promoting properties, and surface film-forming properties tend to be obtained. The surfactant may be low molecular weight or high molecular weight. It is preferable that the surfactant is a polymer. The number average molecular weight of the surfactant is preferably 3000 or more, and more preferably 5000 or more. On the other hand, the number average molecular weight of the surfactant is preferably 100,000 or less, and more preferably 50,000 or less.

[0073] Examples of surfactants include glycerin esters, amide surfactants, and polymers having a quaternary ammonium salt structure. Examples of polymers having a quaternary ammonium salt structure include (meth)acrylic acid copolymers having a quaternary ammonium salt structure, maleic acid copolymers having a quaternary ammonium salt structure, polyvinylpyrrolidone copolymers having a quaternary ammonium salt structure, polyethyleneimine copolymers having a quaternary ammonium salt structure, polyoxyethylene-polyoxypropylene copolymers having a quaternary ammonium salt structure, polyvinyl alcohol copolymers having a quaternary ammonium salt structure, polyvinyl ether copolymers having a quaternary ammonium salt structure, and polyacrylamide copolymers having a quaternary ammonium salt structure. From the viewpoint of dispersibility in the release layer, polymers having a quaternary ammonium salt structure are preferred, and (meth)acrylic acid copolymers having a quaternary ammonium salt structure (hereinafter also referred to as "quaternary ammonium salt-containing (meth)acrylic polymers") are even more preferred. In the case of polymers having a quaternary ammonium salt structure, unlike conductive polymers, electrons do not travel through the polymer skeleton, and the hydrophilic groups modified on the polymer skeleton absorb moisture from the air, thereby exhibiting an antistatic effect. If the surfactant can be well dispersed in the release layer, conductive paths formed by the surfactant can easily connect, and the release film tends to have excellent antistatic properties.

[0074] The quaternary ammonium salt-containing (meth)acrylic polymer preferably has a quaternary ammonium salt structure in the polymer main chain. In this case, the outflow of the quaternary ammonium salt from the system is easily suppressed. From the viewpoint of suppressing bleed-out, the number average molecular weight of the quaternary ammonium salt-containing (meth)acrylic polymer is preferably 3000 or more, and more preferably 5000 or more. From the viewpoint of dispersibility in the release layer, the number average molecular weight of the quaternary ammonium salt-containing (meth)acrylic polymer is preferably 100,000 or less, and more preferably 50,000 or less.

[0075] Methods for obtaining quaternary ammonium salt-containing (meth)acrylic polymers include copolymerizing a quaternary ammonium salt-containing monomer with (meth)acrylate, and ion-exchanging the carboxyl groups in a copolymer of (meth)acrylate and a carboxyl group-containing monomer with a quaternary ammonium salt. Examples of quaternary ammonium salt-containing monomers include methyl chloride salt of dimethylaminoethyl methacrylate and methyl chloride salt of dimethylaminopropyl acrylamide.

[0076] In quaternary ammonium salt-containing (meth)acrylic polymers, the quaternary ammonium salt content is preferably 0.1 mol% or more, and more preferably 0.5 mol% or more, relative to the total amount (100 mol%) of all units constituting the quaternary ammonium salt-containing (meth)acrylic polymer, from the viewpoint of excellent antistatic performance. Furthermore, from the viewpoint of dispersibility in the release layer, it is preferably 20 mol% or less, and more preferably 5 mol% or less.

[0077] Examples of conductive materials include conductive metal oxides such as titanium oxide, tin oxide, tin-doped indium oxide, antimond-doped tin oxide, phosphorus-doped tin oxide, zinc antimonate, and antimony oxide.

[0078] Examples of conductive materials include metal ion conductive salts such as lithium salt compounds.

[0079] Among conductive materials, examples of conductive carbon materials include carbon nanotubes and graphite. Carbon nanotubes are preferred from the viewpoint that they can exhibit high antistatic performance with only a small amount of addition, do not impair mold release properties, and have a small particle size so can be included even in thin mold release layers.

[0080] Examples of carbon nanotubes include multi-wall, single-wall, ladder, and branched types, with the ladder type being preferred. The number of layers in multi-wall carbon nanotubes is preferably 4 to 7. The ladder type is a structure in which carbon nanotubes are cross-linked or branched, and is also called a carbon nanostructure. The diameter of the carbon nanotubes is preferably 1 nm or more, more preferably 10 nm or more. The diameter of the carbon nanotubes is preferably 50 nm or less, more preferably 40 nm or less. The length of the carbon nanotubes is preferably 10 nm or more, more preferably 40 nm or more. The length of the carbon nanotubes is preferably 200 nm or less, more preferably 100 nm or less.

[0081] The conductive materials described above may be used in combination of one or more types. From the viewpoint of transfer prevention, conductive polymers, ionic liquids, surfactants, metal ion conductive salts, and conductive carbon materials are preferred as conductive materials. Furthermore, from the viewpoint of obtaining a release film with excellent antistatic performance, surfactants and conductive carbon materials are preferred, and from the viewpoint of dispersibility, surfactants are even more preferred.

[0082] The conductive material may be included as particles in the release layer, dispersed in it, or compatible with other resins in the release layer.

[0083] The content of the conductive material in the release layer is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.8% by mass or more, and particularly preferably 1.0% by mass or more, from the viewpoint of electron conduction assistance function. Also, from the viewpoint of release properties, it is preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 6% by mass or less, and particularly preferably 4% by mass or less. In other words, the content of the conductive material in the release layer is preferably 0.001% by mass to 10% by mass. The surface resistivity of the single film of the release layer is 1 × 10⁻⁶ １１ It is preferable that the ratio be Ω / □ or greater. Within the above range, the antistatic function will not be exhibited in a single release layer, and only the electro-electric assist function will be exhibited.

[0084] The release layer is preferably a layer that has release properties. The release layer may or may not be tacky. The release layer preferably contains at least one selected from (meth)acrylic polymers, epoxy polymers, and urethane polymers, and more preferably contains a (meth)acrylic polymer that is a reaction cured product of a hydroxyl group-containing (meth)acrylic polymer and a polyfunctional isocyanate compound. The ratio of the hydroxyl group-containing (meth)acrylic polymer to the polyfunctional isocyanate compound is preferably 30:3 to 30:15, and more preferably 30:3 to 30:10. Note that the urethane polymer does not have units based on monomers having (meth)acryloyl groups.

[0085] When the release layer contains a quaternary ammonium salt-containing (meth)acrylic polymer as a conductive material, it is preferable that the release layer contains a (meth)acrylic polymer from the viewpoint of dispersibility of the conductive material in the release layer, and more preferably that it contains a (meth)acrylic polymer that is a reaction-cured product of a hydroxyl group-containing (meth)acrylic polymer and a polyfunctional isocyanate compound.

[0086] The hydroxyl groups in hydroxyl group-containing (meth)acrylic polymers are crosslinking functional groups that react with isocyanate groups in polyfunctional isocyanate compounds. The hydroxyl value of hydroxyl group-containing (meth)acrylic polymers is preferably 1 to 100 mg KOH / g, and particularly preferably 29 to 100 mg KOH / g. When multiple types of hydroxyl group-containing (meth)acrylic polymers are used in the release layer, the range of the hydroxyl value is the preferred range of the total hydroxyl value of the multiple types of hydroxyl group-containing (meth)acrylic polymers. The hydroxyl value is measured by the method specified in JIS K0070:1992.

[0087] The hydroxyl group-containing (meth)acrylic polymer may or may not have a carboxyl group. The carboxyl group, like the hydroxyl group, is a crosslinking functional group that reacts with the isocyanate group in the polyfunctional isocyanate compound. The acid value of the hydroxyl group-containing (meth)acrylic polymer is preferably 100 mg KOH / g or less, more preferably 30 mg KOH / g or less, and may be 0 mg KOH / g.

[0088] The crosslinking functional group equivalent (total equivalent of hydroxyl groups and carboxyl groups) of a hydroxyl group-containing (meth)acrylic polymer is preferably 2,000 g / mol or less, more preferably 500 to 2,000 g / mol, and particularly preferably 600 to 1,000 g / mol. "Total equivalent of hydroxyl groups and carboxyl groups" refers to the total mass per mole of hydroxyl groups and carboxyl groups in the hydroxyl group-containing (meth)acrylic polymer.

[0089] The equivalent amount of crosslinking functional groups corresponds to the molecular weight between crosslinking points and is a physical property that governs the elastic modulus after crosslinking (elastic modulus of the reaction-cured product). When the equivalent amount of crosslinking functional groups is 2,000 g / mol or less, the elastic modulus of the reaction-cured product becomes sufficiently high, resulting in excellent release properties from the resin encapsulation part of the release layer and excellent peelability from semiconductor chips, source electrodes, or sealing glass. Furthermore, when the equivalent amount of crosslinking functional groups is 2,000 g / mol or less, migration (transfer) to the resin encapsulation part is suppressed. The equivalent amount of crosslinking functional groups of a hydroxyl group-containing (meth)acrylic polymer is determined by dividing the molecular weight of potassium hydroxide (56.1) by the sum of the hydroxyl value and acid value of the hydroxyl group-containing (meth)acrylic polymer and multiplying by 1000.

[0090] In a hydroxyl group-containing (meth)acrylic polymer, the hydroxyl group may be present in the side chain, at the end of the main chain, or in both the side chain and the main chain. It is preferable that it be present in at least the side chain, as this allows for easy adjustment of the hydroxyl group content.

[0091] As the hydroxy group-containing (meth)acrylic polymer in which a carboxyl group is present in the side chain, a copolymer having the following unit c1 and unit c2 is preferable. Unit c1: A unit based on a hydroxy group-containing (meth)acrylate. Unit c2: A unit based on a monomer other than unit c1.

[0092] Examples of unit c1 include a unit represented by the following formula 1. -(CH ２ -CR １ (COO-R ２ -OH))- Formula 1 However, R １ is a hydrogen atom or a methyl group, and R ２ is an alkylene group having 2 to 10 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms, or -R ３ -OCO-R ５ -COO-R ４ [[ID=1十九]]-. R ３ and R ４ are each independently an alkylene group having 2 to 10 carbon atoms, and R ５ is a phenylene group.

[0093] As R １ , a hydrogen atom is preferable. The alkylene groups in R ２ , R ３ , and R ４ may be linear or branched.

[0094] Specific examples of the monomer that becomes unit c1 include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1,4-cyclohexanedimethanol monoacrylate, and 2-acryloyloxyethyl-2-hydroxyethyl-phthalic acid. etc. The monomer that becomes unit c1 may be used alone or in combination of two or more. From the viewpoint of excellent reactivity of the hydroxy group, unit c1 is preferably one in which R ２ in the above formula 1 is an alkylene group having 2 to 10 carbon atoms. That is, a unit based on a hydroxyalkyl (meth)acrylate having a hydroxyalkyl group having 2 to 10 carbon atoms is preferable.

[0095] The ratio of unit c1 to the total number of all units constituting the hydroxyl group-containing (meth)acrylic polymer (100 mol%) is preferably 3 mol% or more, more preferably 40 mol% or less, more preferably 30 mol% or less, and even more preferably 20 mol% or less. When the ratio of unit c1 is above the lower limit, the crosslinking density by the polyfunctional isocyanate compound becomes sufficiently high, and the release layer has excellent release properties from resins and electronic components, which is preferable. When the ratio of unit c1 is below the upper limit, the release layer has excellent adhesion, which is preferable.

[0096] Unit c2 is not particularly limited as long as it is copolymerizable with the monomer that forms unit c1. Unit c2 may have a carboxyl group, but it is preferable that it does not have a reactive group that can react with isocyanate groups other than a carboxyl group (e.g., an amino group). Examples of monomers that form unit c2 include macromers having an unsaturated double bond, (meth)acrylates without a hydroxyl group, (meth)acrylic acid, acrylonitrile, and the like.

[0097] Examples of macromers having unsaturated double bonds include macromers having polyoxyalkylene chains, such as (meth)acrylates of polyethylene glycol monoalkyl ethers.

[0098] Examples of (meth)acrylates that do not have a hydroxyl group include alkyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, toluyl (meth)acrylate, benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, glycidyl (meth)acrylate, 2-aminoethyl (meth)acrylate, 3-(methacryloyloxypropyl)trimethoxysilane, trifluoromethylmethyl (meth)acrylate, and 2-trifluoromethylethyl (meth)acrylate. Examples include 2-perfluoroethylethyl (meth)acrylate, 2-perfluoroethyl-2-perfluorobutylethyl (meth)acrylate, 2-perfluoroethyl (meth)acrylate, perfluoromethyl (meth)acrylate, diperfluoromethylmethyl (meth)acrylate, 2-perfluoromethyl-2-perfluoroethylmethyl (meth)acrylate, 2-perfluorohexylethyl (meth)acrylate, 2-perfluorodecylethyl (meth)acrylate, and 2-perfluorohexadecylethyl (meth)acrylate.

[0099] Preferably, alkyl (meth)acrylates are compounds in which the alkyl group has 1 to 12 carbon atoms, and examples include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, and dodecyl (meth)acrylate.

[0100] The unit c2 preferably contains at least units based on alkyl (meth)acrylate. The ratio of alkyl (meth)acrylate units to the total number of all units constituting the hydroxyl group-containing (meth)acrylic polymer (100 mol%) is preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and preferably 97 mol% or less. When the ratio of alkyl (meth)acrylate units is above the lower limit, the glass transition temperature, mechanical properties, etc. derived from the structure of alkyl (meth)acrylate are expressed, and the mechanical strength and tackiness of the release layer are excellent. When the ratio of alkyl (meth)acrylate units is below the upper limit, the crosslinking density increases because the hydroxyl group content is sufficient, and a high modulus of elasticity can be expressed.

[0101] The mass-average molecular weight (Mw) of the hydroxyl group-containing (meth)acrylic polymer is preferably 100,000 to 1,200,000, more preferably 200,000 to 1,000,000, and even more preferably 200,000 to 700,000. When Mw is above the lower limit, the release layer exhibits excellent release properties from resins and electronic components. When Mw is below the upper limit, the release layer exhibits excellent adhesion properties. The Mw of the hydroxyl group-containing (meth)acrylic polymer is a polystyrene-converted value obtained by measuring it by gel permeation chromatography using a calibration curve prepared with standard polystyrene samples of known molecular weight.

[0102] The glass transition temperature (Tg) of a hydroxyl group-containing (meth)acrylic polymer is preferably 20°C or lower, and more preferably 0°C or lower. When Tg is below the upper limit, the release layer exhibits sufficient flexibility even at low temperatures and is less likely to peel off from the substrate. The lower limit of Tg is not particularly limited, but within the molecular weight range mentioned above, -60°C or higher is preferred. Tg is the midpoint glass transition temperature measured by differential scanning calorimetry (DSC).

[0103] Polyfunctional isocyanate compounds are compounds having two or more isocyanate groups, and compounds having 3 to 10 isocyanate groups are preferred. Examples of polyfunctional isocyanate compounds include hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate (NDI), tolidine diisocyanate (TODI), isophorone diisocyanate (IPDI), xylene diisocyanate (XDI), triphenylmethane triisocyanate, and tris(isocyanatephenyl)thiophosphate. Also, examples include isocyanurate (trimer) and burette forms of these polyfunctional isocyanate compounds, and adduct forms of these polyfunctional isocyanate compounds and polyol compounds. It is preferable that polyfunctional isocyanate compounds have an isocyanurate ring, as the planarity of the ring structure allows the reaction-cured product (release layer) to exhibit a high elastic modulus. Examples of polyfunctional isocyanate compounds having an isocyanurate ring include isocyanurate derivatives of HDI (isocyanurate-type HDI), isocyanurate derivatives of TDI (isocyanurate-type TDI), and isocyanurate derivatives of MDI (isocyanurate-type MDI).

[0104] The release layer may contain other components. Examples of other components include crosslinking catalysts (e.g., amines, metal compounds, acids, etc.), reinforcing fillers, coloring dyes, pigments, particles, etc.

[0105] The crosslinking catalyst can be any substance that functions as a catalyst for the reaction (urethane formation reaction) between a hydroxyl group-containing acrylic copolymer and a crosslinking agent when a polyfunctional isocyanate compound is used as the crosslinking agent. General urethane formation reaction catalysts can be used, and examples include amine compounds such as tertiary amines, organotin compounds, organolead compounds, organozinc compounds, and other organometallic compounds. Examples of tertiary amines include trialkylamines, N,N,N',N'-tetraalkyldiamines, N,N-dialkylamino alcohols, triethylenediamines, morpholine derivatives, and piperazine derivatives. Examples of organotin compounds include dialkyltin oxides, fatty acid salts of dialkyltin, and fatty acid salts of stannous tin.

[0106] As the crosslinking catalyst, organotin compounds are preferred, with dioctyl tin oxide, dioctyl tin dilaurate, dibutyl tin laurylate, and dibutyl tin dilaurate being particularly preferred. Alternatively, a dialkylacetylacetone tin complex catalyst, synthesized by reacting a dialkyltin ester with acetylacetone in a solvent and having a structure in which two molecules of acetylacetone are coordinated to one dialkyltin atom, can be used. The amount of crosslinking catalyst used is preferably 0.01 to 0.5 parts by mass per 100 parts by mass of the hydroxyl group-containing acrylic polymer.

[0107] The particles may be incorporated into the release layer from the viewpoint of improving the laser marking visibility of semiconductor packages manufactured using the release film according to this embodiment. Note that if a substrate having an uneven surface structure is used, the release layer does not need to contain particles. The material of the particles contained in the release layer is not particularly limited; for example, they may be organic or inorganic particles. The average particle diameter is preferably 2.0 μm or more, and preferably 10 μm or less.

[0108] From the viewpoint of the release properties of the release film, it is preferable for the release layer to have a certain thickness, and a thicker release layer is particularly preferable when the substrate surface is a matte surface with an uneven shape. On the other hand, increasing the thickness of the release layer deteriorates the antistatic properties. However, by including a conductive material in the release layer, the release layer is more likely to have the function of assisting electron conduction to the antistatic layer, so that good antistatic properties can be maintained while maintaining release properties. Therefore, from the viewpoint of the release properties of the release film, the average thickness of the release layer is preferably 0.1 μm or more, more preferably 2.5 μm or more, and even more preferably 3 μm or more. Also, from the viewpoint of the smoothness of the release layer, it is preferably 40 μm or less, more preferably 15 μm or less, and even more preferably 7 μm or less.

[0109] (Other layers) The release film may have other layers. These other layers may be provided between the substrate layer and the antistatic layer, or between the antistatic layer and the release layer, or on the side of the substrate layer opposite to the antistatic layer, or on the side of the release layer opposite to the antistatic layer. For example, the other layer may be the first surface of the release film. Examples of other layers include a gas barrier layer and a colored layer. These layers may be used individually or in combination of two or more. The average thickness of each of the other layers is preferably 0.05 to 3 μm, and more preferably 0.05 to 2 μm.

[0110] (Physical properties of the release film) The surface resistivity of the first surface of the release film is 1 × 10⁻⁶ ９ Preferably, Ω / □ or less, 5 × 10 ８ Ω / □ or less is more preferable, and 1 × 10 ８ A value of Ω / □ or less is even more preferable. In this case, damage to the semiconductor chip due to discharge during peeling can be effectively prevented. The lower limit of the surface resistivity of the first surface of the release film is not particularly limited, but 1 × 10 ７ The ratio may be greater than or equal to Ω / □. Surface resistivity can be measured in accordance with IEC 60093, the double-ring electrode method.

[0111] The first surface of the release film may be either a mirror surface or a matte surface with an uneven shape. The shape of the first surface of the release film is transferred to the surface of the semiconductor package when the semiconductor element is sealed using the release film to obtain a semiconductor package. Therefore, the shape of the first surface should be selected according to the desired shape of the semiconductor package, but a matte surface with an uneven shape is preferable because it makes it easier to print information such as part numbers and QR codes on the semiconductor package using laser marking.

[0112] When the first surface of the release film is mirror-finished, the arithmetic mean roughness Ra is preferably 0.15 μm or less. The lower limit of the arithmetic mean roughness Ra is not particularly limited, but is preferably 0.02 μm or more. Also, when the first surface of the release film is mirror-finished, the ten-point average roughness Rz is preferably 0.6 μm or less. The lower limit of the ten-point average roughness Rz is not particularly limited, but is preferably 0.1 μm or more.

[0113] When the first surface of the release film is a matte surface with an uneven shape, the arithmetic mean roughness Ra is preferably 4.0 μm or less, more preferably 3.0 μm or less, even more preferably 2.5 μm or less, and particularly preferably 2.0 μm or less, from the viewpoint of the visibility of laser marking on semiconductor packages obtained using the release film. The arithmetic mean roughness Ra is preferably greater than 0.15 μm, more preferably 0.2 μm or more, and even more preferably 0.4 μm or more, from the viewpoint of the visibility of laser marking on semiconductor packages obtained using the release film. Furthermore, when the first surface of the release film is a matte surface with an uneven shape, the ten-point average roughness Rz is preferably 20 μm or less, more preferably 12 μm or less, and even more preferably 9.0 μm or less, from the viewpoint of the visibility of laser marking on semiconductor packages obtained using the release film, the ten-point average roughness Rz is preferably greater than 0.5 μm, and preferably 0.7 μm or more, from the viewpoint of the visibility of laser marking on semiconductor packages obtained using the release film.

[0114] The total mass of the release layer and antistatic layer in the release film is 2 g / m². ２ The above is preferable, 3 g / m ２ The above is more preferable: 5 g / m２ The above is even more preferable. A larger total mass of the release layer and antistatic layer in the release film makes it less likely for the release layer and antistatic layer to be missed during coating. Furthermore, since the release film of the present invention contains a conductive material in the release layer, it tends to have excellent antistatic properties even if the total mass of the release layer and antistatic layer is large. From the viewpoint of the release properties of the release film, the total mass of the release layer and antistatic layer in the release film is 40 g / m². ２ The following is preferable: 30 g / m ２ The following is more preferable: 20 g / m ２ The following is even more preferable: 15 g / m ２ The following are particularly preferable.

[0115] The total mass of the release layer and antistatic layer in a release film can be determined by removing the release layer and antistatic layer from the release film and measuring the mass difference before and after removal. The release layer and antistatic layer can be removed by impregnating the release film with a solvent and scrubbing the surface with a melamine sponge. The type of solvent and impregnation time should be selected according to the materials of the antistatic layer and release layer of the release film, but one example is impregnation with ethyl acetate for 4 hours.

[0116] <Method for manufacturing release film> The release film according to this embodiment can be manufactured by forming an antistatic layer on one main surface (first surface of the substrate) of the substrate, followed by forming a release layer.

[0117] The method for forming the antistatic layer is not particularly limited, but a preferred method involves coating the antistatic layer composition onto the first surface of the substrate and drying it. Various known wet coating methods can be used for the coating, such as gravure coating, die coating, and bar coating. The drying temperature and time are adjusted as appropriate depending on the type and content of the liquid medium.

[0118] A preferred method for forming the release layer is to coat the antistatic layer with a release layer composition containing the components of the release layer and a liquid medium, and then dry it. Various known wet coating methods can be used for the coating, such as the gravure coating method, die coating method, and bar coating method. The drying temperature and time should be adjusted as appropriate depending on the type and content of the liquid medium.

[0119] <Method for Manufacturing Semiconductor Packages> The release film according to this embodiment is useful in the sealing process when manufacturing a semiconductor package having a semiconductor element and a resin sealing portion formed from a curable resin that seals the semiconductor element. A method for manufacturing a semiconductor package using the release film according to this embodiment is, for example, to place a substrate equipped with a semiconductor element in the cavity of a mold, to place the release film according to this embodiment on the cavity surface of the mold where the substrate is not placed, with the first surface of the release film facing the space inside the cavity of the mold, to fill the cavity with a curable resin, and to cure the curable resin in contact with the release film to form a resin sealing portion that seals the semiconductor element.

[0120] The method for manufacturing the semiconductor package according to this embodiment can employ known manufacturing methods, except for the use of the release film according to this embodiment. For example, compression molding and transfer molding can be used as methods for forming the resin encapsulation portion, and known compression molding apparatus or transfer molding apparatus can be used as the apparatus in this case. The manufacturing conditions are also the same as those in known semiconductor package manufacturing methods.

[0121] Based on the above, the following release films are disclosed in this specification: [1] A release film having a substrate, an antistatic layer, and a release layer in that order, wherein the release layer comprises at least one conductive material selected from conductive polymers, ionic liquids, surfactants, conductive metal oxides, metal ion conductive salts, and conductive carbon materials. [2] The release film according to [1], wherein the conductive material comprises a surfactant or a conductive carbon material. [3] The release film according to [1] or [2], wherein the surfactant comprises a polymer having a quaternary ammonium salt structure. [4] The release film according to any one of [1] to [3], wherein the antistatic layer comprises an antistatic agent, and both the antistatic agent and the conductive material in the release layer are polymers. [5] The release film according to any one of [1] to [4], wherein the release layer comprises at least one selected from (meth)acrylic polymers, epoxy polymers, and urethane polymers. [6] A release film according to any one of [1] to [5], wherein the release layer contains a (meth)acrylic polymer and the conductive material is a (meth)acrylic polymer. [7] A release film according to any one of [1] to [6], wherein the average thickness of the release layer is 2.5 μm or more. [8] The total mass of the release layer and the antistatic layer is 2 g / m ２ The above is the release film according to any one of [1] to [7]. [9] The release film according to any one of [1] to [8], wherein the antistatic agent is a conductive polymer and the conductive material in the release layer is a polymer having a quaternary ammonium salt structure.

[0122] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the following description.

[0123] [Evaluation Method] (Thickness) The average thickness of the substrate, antistatic layer, and release layer was determined by observing the cross-section of the release film using a focused ion beam scanning electron microscope (FIB-SEM). With FIB-SEM, the boundaries between layers can be determined from the difference in contrast between layers, and the thickness of each layer can be measured. The average thickness of the substrate was determined by performing the same measurement using a focused ion beam scanning electron microscope (FIB-SEM) at 30 randomly selected locations, and at least 30 locations between concave and convex areas if surface irregularities were observed, and averaging the measurement results.

[0124] (Arithmetic Mean Roughness Ra) The arithmetic mean roughness Ra (μm) was measured in accordance with JIS B0601:2013 (ISO 4287:1997, Amd. 1:2009). The reference length lr (cutoff value λc) was 0.8 mm, and the measurement length was 8 mm. For the measurement, a surface roughness measuring instrument (SURFCOM 480A, manufactured by Tokyo Seimitsu Co., Ltd.) was used, and for both the substrate and the release film, Ra was determined at a total of 6 locations: 3 locations perpendicular to the flow direction during film manufacturing and 3 locations parallel to it. The average value of these measurements was taken as the Ra of the surface.

[0125] (Ten-point average roughness Rz) The ten-point average roughness Rz (μm) was measured in accordance with JIS B0601:2013 (ISO 4287:1997, Amd. 1:2009). Using a Mitutoyo SJ-310 (4 mN, 5 μm / 90° probe), Rz was measured at a total of three locations, and the average value of these measurements was taken as Rz. For measuring the ten-point average roughness Rz of the substrate, the release film was impregnated in ethyl acetate for 4 hours, and then the release layer and antistatic layer were removed by rubbing with a melamine sponge to expose the surface of the substrate.

[0126] (Total mass of release layer and antistatic layer) After impregnating the release film in a solvent (ethyl acetate) for 4 hours, the release layer and antistatic layer were removed by scrubbing with a melamine sponge. The difference in mass before and after removal was calculated as the total mass of the release layer and antistatic layer (g / m³). ２ )

[0127] (Surface Resistivity) The surface resistivity (Ω / □) of the first surface of the release film (the surface on the release layer side, the surface in contact with the curable resin) was measured in accordance with IEC 60093, the double-ring electrode method. The measuring instrument was an ultra-high resistance meter R8340 (manufactured by Advantec), and a resistance chamber 12704A was used as the electrode. The measurement was performed with an applied voltage of 500V for a duration of 1 minute. A (Good): 1 × 10⁻⁶ ９ (Ω / □) or less C (defective): 1×10 ９ (Ω / □) super

[0128] (Appearance) The release film was placed on a horizontal surface, and the color of the coated surface was visually evaluated while illuminating it with a white fluorescent lamp. A (Good): The entire coated surface shows a consistent color. C (Poor): Uneven coating is noticeable due to differences in brightness and color.

[0129] (Coating defects) The coating surface of the release film was analyzed using a scanning electron microscope (SEM-EDAX) at a 1000x magnification field of view at five or more locations to observe the coating condition. A (Good): No areas where the substrate surface is exposed C (Poor): Areas where the substrate surface is exposed are found

[0130] (Release) A 13cm x 13cm x 100μm thick aluminum foil (JIS H4000:2006 AIN30P) was placed on a 13cm x 13cm first stainless steel plate. On top of that, a 125μm thick polyimide film, cut out from 10cm x 12cm to 8cm x 10cm, was placed as a spacer. Furthermore, an appropriate amount of semiconductor encapsulating epoxy resin (Sumicon EME G770H typeF ver.GR (manufactured by Sumitomo Bakelite Co., Ltd.)) was sprinkled as a curable resin into the cut-out portion of the polyimide film. On top of that, a release film cut to 13cm x 13cm was placed so that its first surface was in contact with the curable resin, after being pre-statically discharged. Finally, a 13cm x 13cm stainless steel plate was placed on top.

[0131] The sample prepared using the above procedure was pressed in a press machine at a temperature of 180°C, a pressure of 1 MPa, and a time of 3 minutes. After removing it from the press machine, the entire sample was placed on a 180°C hot plate, the stainless steel plate was removed, and the release film was peeled off manually over 5 seconds. The criteria for evaluating the release properties were as follows, with A and B being considered acceptable. A (Good): After removing the stainless steel plate, the release film was no longer adhered to the epoxy resin and could be easily peeled off manually with almost no force applied. B (Acceptable): After removing the stainless steel plate, the release film and epoxy resin were adhered and required force to peel off, but the entire surface could be peeled off. C (Poor): The entire surface could not be peeled off.

[0132] (Transfer Prevention) For samples with a release property rating of A, after peeling, the surface of the cured resin was observed with an optical microscope (magnification 100x) to check for any transfers originating from the release film. The evaluation criteria for transfer prevention are as follows: A (Good): No transfers were observed on the surface of the cured product. C (Poor): Transfers were observed on the surface of the cured product.

[0133] [Materials Used] (Base Material) ・ETFE film: An ETFE film was prepared using a fluororesin having units based on the monomers shown in ETFE(1) below. The method for preparing the ETFE film is described in each example. ETFE(1): TFE units / E units / PFBE units = 60 / 40 / 3.3 (molar ratio), melting point 225°C, MFR 15g / 10min

[0134] PET film: Toyobo Ester® Film G2CUO (manufactured by Toyobo Co., Ltd.), 50 μm thick

[0135] ETFE / PET / ETFE film: Prepared using the following PET film, ETFE film (i), ETFE film (ii), and adhesive coating solution. PET film: (Toyobo Ester® Film G2UO (manufactured by Toyobo Co., Ltd.), 25 μm thick, corona treated on both sides) Adhesive coating solution: A 10:1 (mass ratio) mixture of DIC Corporation's Chrisbon® NT-258 and Tosoh Corporation's Colonnate® 2096 was mixed with ethyl acetate to create an adhesive coating solution with a solid content of 10% by weight. ETFE film (i): AGC Corporation's 12N-S, 12 μm thick, corona treated on one side ETFE film (ii): AGC Corporation's 25HK-S, 25 μm thick, one side corona treated, the other side a matte surface with an uneven shape 5 g / m of adhesive coating solution applied to one surface of the PET film ２ The adhesive was applied and dried at 100°C. The amount of adhesive applied was 0.5 g / m². ２ The ETFE film (i) and the PET film were bonded together immediately after drying, with the corona-treated surface of the ETFE film (i) facing the PET side, to obtain a two-layer ETFE / PET film. 5 g / m² of adhesive solution was applied to the PET surface of the two-layer ETFE / PET film. ２ The material was applied and dried at 100°C. Immediately after drying, the ETFE film (ii) and the ETFE / PET two-layer film were laminated so that the corona-treated surface of the ETFE film (ii) faced the PET side, thereby obtaining a three-layer ETFE / PET / ETFE film.

[0136] (Antistatic Layer Liquid) ・Antistatic layer liquid (1): 10 parts by mass of a polythiophene-based conductive polymer dispersion containing acrylic resin (Aracoat® AS601D (solids content 4% by mass, manufactured by Arakawa Chemical Industries, Ltd.)) and 1 part by mass of a polyfunctional aziridine compound curing agent (Aracoat® CL910 (solids content 10% by mass, manufactured by Arakawa Chemical Industries, Ltd.)) were mixed. The resulting mixture was diluted with a mixed solvent of isopropanol / toluene / water = 50 / 40 / 10 (mass ratio) to obtain the antistatic layer liquid to achieve the solids content concentration for each example. The surface resistivity of the antistatic layer itself after the formation of the antistatic layer described later is 6.7 × 10⁻⁶. ７ The ratio is Ω / □, and the specific gravity of the antistatic layer is 1100 kg / m³.２ That was the case.

[0137] (Release layer liquid) ・Release layer liquid (1): 100 parts by mass of Nissetsu (registered trademark) KP2562 [manufactured by Nippon Carbide Industries Co., Ltd., solid content 35% by mass, hydroxyl group-containing (meth)acrylic polymer (hydroxyl value 70 mg KOH / g, crosslinking functional group equivalent 801 g / mol)], 6 parts by mass of Nissetsu (registered trademark) CK157 [(manufactured by Nippon Carbide Industries Co., Ltd., solid content 100% by mass, trifunctional isocyanate compound (isocyanurate-type hexamentiene diisocyanate)], and 21 parts by mass of Nissetsu (registered trademark) CK-939 (manufactured by Nippon Carbide Industries Co., Ltd., solid content 0.5% by mass, acetylacetone solution of dioctyl tin dilaurate)] were mixed. The resulting mixture was diluted with ethyl acetate to obtain the release layer liquid to the solid content concentration of each example. The specific gravity of the release layer after the formation of the release layer described later was 1100 kg / m ２ The following was the result. • Release layer liquid (2): A release layer liquid was obtained by adding a quaternary ammonium salt-containing (meth)acrylic polymer (1SX-1071I, manufactured by Taisei Fine Chemical Co., Ltd.) to release layer liquid (1). The amount added is shown in the tables below. Note that the specific gravity of the release layer after its formation, as described below, was 1100 kg / m³ regardless of the amount of quaternary ammonium salt-containing (meth)acrylic polymer added. ２ The following was the result. • Release layer liquid (3): A release layer liquid was obtained by adding ladder-type carbon nanotubes (ATHLOS® CNS, manufactured by Cabot Corporation) to release layer liquid (1). The amount added is shown in the tables below. Note that the specific gravity of the release layer after the formation of the release layer described below was 1100 kg / m³ regardless of the amount of carbon nanotubes added. ２ The following was the result. • Release layer liquid (4): 0.30 parts by mass of metal particles, SQ (manufactured by BASF Co., Ltd., iron powder, average particle size 6 μm), were added to 50 parts by mass of release layer liquid (1) and stirred to obtain a coating liquid. The obtained mixture was diluted with ethyl acetate to obtain a release layer liquid to the solid content concentration shown in Table 1. Note that the specific gravity of the release layer after its formation could not be accurately measured because of the presence of metal particles. Therefore, the specific gravity of the resin component excluding the metal particles was set to 1100 kg / m³, the same as that of release layer liquid (1). ２ This was used as a reference value.

[0138] [Example 1-1] ETFE (1) was fed into an extruder, and melt-extruded at 320°C using an extruder with the lip opening adjusted so that the film thickness was 100 μm. The film was taken up using a die roll with a surface textured surface and a die roll with a mirror surface, adjusting the film formation speed. An ETFE film was produced in which one side (substrate surface 1) was mirror-finished and the other side (substrate surface 2) had a textured structure. The arithmetic mean roughness Ra of the first surface was 0.1 μm, and the ten-point mean roughness Rz of the first surface was 0.5 μm. Furthermore, the first surface of the ETFE film was subjected to corona treatment. An antistatic layer liquid (1) with a solid content concentration of 4.0 mass% was coated onto the corona-treated surface of the ETFE film using a gravure coater and dried to form an antistatic layer with the average thickness and surface resistivity shown in Table 1. The coating was performed using a direct gravure method, and drying was carried out at 100°C for 1 minute. On the antistatic layer, a release layer liquid (2) with a solid content of 13% by mass (where the polymer content having a quaternary ammonium salt structure in the release layer is 0.05% by mass) was applied using a gravure coater and dried to form a release layer with the average thickness shown in Table 1. The coating was performed using a direct gravure method, and drying was carried out at 100°C for 1 minute. After that, the film was cured at 40°C for 120 hours to obtain a release film.

[0139] [Example 1-2] A release film was obtained in the same manner as in Example 1-1, except that the release layer was formed using release layer liquid (2) (where the content of quaternary ammonium salt-containing (meth)acrylic polymer in the release layer is 0.5% by mass) as the release layer liquid.

[0140] [Example 1-3] A release film was obtained in the same manner as in Example 1-1, except that the release layer was formed using release layer liquid (2) (where the content of quaternary ammonium salt-containing (meth)acrylic polymer in the release layer is 3.0% by mass).

[0141] [Example 1-4] A release film was obtained in the same manner as in Example 1-1, except that the release layer was formed using release layer liquid (2) (provided that the content of quaternary ammonium salt-containing (meth)acrylic polymer in the release layer was 5.0% by mass).

[0142] [Example 1-5] A release film was obtained in the same manner as in Example 1-1, except that a release layer was formed using release layer liquid (1) as the release layer liquid.

[0143] [Example 1-6] A release film was obtained in the same manner as in Example 1-1, except that release liquid (2) was used as the release liquid (however, the content of quaternary ammonium salt-containing (meth)acrylic polymer in the release layer was 0.5% by mass), and the release layer was formed to the average thickness shown in Table 1.

[0144] [Example 1-7] A release film was obtained in the same manner as in Example 1-6, except that the release layer was formed using release layer liquid (2) (where the content of quaternary ammonium salt-containing (meth)acrylic polymer in the release layer is 3.0% by mass) as the release layer liquid.

[0145] [Example 1-8] A release film was obtained in the same manner as in Example 1-6, except that a release layer was formed using release layer liquid (1) as the release layer liquid.

[0146] [Example 1-9] A release film was obtained in the same manner as in Example 1-1, except that release liquid (2) was used as the release liquid (however, the content of quaternary ammonium salt-containing (meth)acrylic polymer in the release layer was 1.0% by mass), and the release layer was formed to have the average thickness shown in Table 1.

[0147] [Example 1-10] A release film was obtained in the same manner as in Example 1-9, except that the release layer was formed using release layer liquid (2) (where the content of quaternary ammonium salt-containing (meth)acrylic polymer in the release layer is 3.0% by mass).

[0148] [Example 1-11] A release film was obtained in the same manner as in Example 1-9, except that a release layer was formed using release layer liquid (1) as the release layer liquid.

[0149] [Example 1-12] A release film was obtained in the same manner as in Example 1-1, except that the release layer liquid (3) (where the carbon nanotube content in the release layer is 0.02% by mass) was used as the release layer liquid, and the release layer was formed to have the average thickness shown in Table 1.

[0150] [Example 1-13] A release film was obtained in the same manner as in Example 1-1, except that a release layer was formed using release layer liquid (4) (solid content concentration 13% by mass) as the release layer liquid.

[0151] [Example 2-1] ETFE (1) was fed into an extruder, and melt-extruded at 320°C using an extruder with the lip opening adjusted so that the film thickness was 100 μm. The film was taken up using two original die rolls with surface irregularities to adjust the film formation speed, and an ETFE film having an irregular structure on both sides was produced. The arithmetic mean roughness Ra and ten-point mean roughness Rz of both sides are shown in Table 2 below. Furthermore, one side (first side) of the ETFE film was subjected to corona treatment. An antistatic layer liquid (1) with a solid content concentration of 4.0 mass% was coated onto the corona-treated side of the ETFE film using a gravure coater and dried to form an antistatic layer with the average thickness and surface resistivity shown in Table 2. Coating was performed using a direct gravure method, and drying was carried out at 100°C for 1 minute. A release layer liquid (2) with a solid content of 13% by mass (where the quaternary ammonium content in the release layer is 0.1% by mass) was applied to the antistatic layer using a gravure coater and dried to form a release layer with the average thickness shown in Table 2. The coating was performed using a direct gravure method, and drying was carried out at 100°C for 1 minute. After that, the film was cured at 40°C for 120 hours to obtain a release film.

[0152] [Example 2-2] A release film was obtained in the same manner as in Example 2-1, except that the release layer was formed using release layer liquid (2) (where the content of quaternary ammonium salt-containing (meth)acrylic polymer in the release layer is 0.5% by mass) as the release layer liquid.

[0153] [Example 2-3] A release film was obtained in the same manner as in Example 2-1, except that release liquid (2) was used as the release liquid (however, the content of quaternary ammonium salt-containing (meth)acrylic polymer in the release layer was 1.0% by mass), and the release layer was formed to have the average thickness shown in Table 2.

[0154] [Example 2-4] A release film was obtained in the same manner as in Example 2-1, except that the release layer was formed using release layer liquid (3) (where the carbon nanotube content in the release layer is 0.02% by mass) as the release layer liquid.

[0155] [Example 2-5] A release film was obtained in the same manner as in Example 2-1, except that a release layer was formed using release layer liquid (1) as the release layer liquid.

[0156] [Example 2-6] A release film was obtained in the same manner as in Example 2-5, except that the thickness of the release layer was as shown in Table 2.

[0157] [Example 2-7] ETFE (1) was fed into an extruder, and melt-extruded at 320°C using an extruder with the lip opening adjusted so that the film thickness was 100 μm. The film was taken up using two original die rolls with surface irregularities to adjust the film formation speed, and an ETFE film having an irregular structure on both sides was produced. The arithmetic mean roughness Ra and ten-point mean roughness Rz of both sides are shown in Table 3 below. Furthermore, one side (first side) of the ETFE film was subjected to corona treatment. An antistatic layer liquid (1) with a solid content concentration of 4.0 mass% was coated onto the corona-treated side of the ETFE film using a gravure coater and dried to form an antistatic layer with the average thickness and surface resistivity shown in Table 3. Coating was performed using a direct gravure method, and drying was carried out at 100°C for 1 minute. A release layer liquid (2) with a solid content of 13% by mass (where the quaternary ammonium salt-containing (meth)acrylic polymer content in the release layer is 0.5% by mass) was applied to the antistatic layer using a gravure coater and dried to form a release layer of the average thickness shown in Table 3. The coating was performed using a direct gravure method, and drying was carried out at 100°C for 1 minute. After that, the film was cured at 40°C for 120 hours to obtain a release film.

[0158] [Example 2-8] A release film was obtained in the same manner as in Example 2-7, except that release liquid (2) was used as the release liquid (however, the content of quaternary ammonium salt-containing (meth)acrylic polymer in the release layer was 3.0% by mass), and the release layer was formed to have the average thickness shown in Table 3.

[0159] [Example 2-9] A release film was obtained in the same manner as in Example 2-7, except that a release layer was formed using release layer liquid (1) as the release layer liquid.

[0160] [Example 2-10] A release film was obtained in the same manner as in Example 2-9, except that the thickness of the release layer was as shown in Table 3.

[0161] [Example 2-11] ETFE (1) was fed into an extruder, and melt-extruded at 320°C using an extruder with the lip opening adjusted so that the film thickness was 100 μm. The film was taken up using two original die rolls with surface irregularities to adjust the film formation speed, and an ETFE film having an irregular structure on both sides was produced. The arithmetic mean roughness Ra and ten-point mean roughness Rz of both sides are shown in Table 4 below. Furthermore, one side (first side) of the ETFE film was subjected to corona treatment. An antistatic layer liquid (1) with a solid content concentration of 4.0 mass% was coated onto the corona-treated side of the ETFE film using a gravure coater and dried to form an antistatic layer with the average thickness and surface resistivity shown in Table 4. Coating was performed using a direct gravure method, and drying was carried out at 100°C for 1 minute. A release layer liquid (2) with a solid content of 13% by mass (where the quaternary ammonium salt-containing (meth)acrylic polymer content in the release layer is 0.5% by mass) was applied to the antistatic layer using a gravure coater and dried to form a release layer of the average thickness shown in Table 4. The coating was performed using a direct gravure method, and drying was carried out at 100°C for 1 minute. After that, the film was cured at 40°C for 120 hours to obtain a release film.

[0162] [Example 2-12] A release film was obtained in the same manner as in Example 2-11, except that release liquid (2) was used as the release liquid (however, the content of quaternary ammonium salt-containing (meth)acrylic polymer in the release layer was 3.0% by mass), and the release layer was formed to the average thickness shown in Table 4.

[0163] [Example 2-13] A release film was obtained in the same manner as in Example 2-11, except that a release layer was formed using release layer liquid (1) as the release layer liquid.

[0164] [Example 2-14] A release film was obtained in the same manner as in Example 2-11, except that the thickness of the release layer was as shown in Table 4.

[0165] [Example 2-15] ETFE (1) was fed into an extruder, and melt-extruded at 320°C using an extruder with the lip opening adjusted so that the film thickness was 100 μm. The film was taken up using two original die rolls with surface irregularities to adjust the film formation speed, and an ETFE film having an irregular structure on both sides was produced. The arithmetic mean roughness Ra and ten-point mean roughness Rz of both sides are shown in Table 5 below. Furthermore, one side (first side) of the ETFE film was subjected to corona treatment. An antistatic layer liquid (1) with a solid content concentration of 4.0 mass% was coated onto the corona-treated side of the ETFE film using a gravure coater and dried to form an antistatic layer with the average thickness and surface resistivity shown in Table 5. Coating was performed using the direct gravure method, and drying was carried out at 100°C for 1 minute. A release layer liquid (2) with a solid content of 13% by mass (where the quaternary ammonium salt-containing (meth)acrylic polymer content in the release layer is 3.0% by mass) was applied to the antistatic layer using a gravure coater and dried to form a release layer of the average thickness shown in Table 5. The coating was performed using a direct gravure method, and drying was carried out at 100°C for 1 minute. After that, the film was cured at 40°C for 120 hours to obtain a release film.

[0166] [Example 2-16] A release film was obtained in the same manner as in Example 2-15, except that the release layer was formed to have the average thickness shown in Table 5.

[0167] [Example 2-17] A release film was obtained in the same manner as in Example 2-15, except that a release layer was formed using release layer liquid (1) as the release layer liquid.

[0168] [Example 2-18] A release film was obtained in the same manner as in Example 2-17, except that the thickness of the release layer was as shown in Table 5.

[0169] [Example 2-19] A release film was obtained in the same manner as in Example 2-17, except that the thickness of the release layer was as shown in Table 5.

[0170] [Example 3-1] The substrate was replaced with a PET film, and one side of the PET film (the second surface of the substrate) was matted by sandblasting. A release film was obtained in the same manner as in Example 1-2, except that a release layer liquid (2) was applied to the other smooth surface (the first surface of the substrate).

[0171] [Example 3-2] A release film was obtained in the same manner as in Example 1-2, except that the base material was replaced with an ETFE / PET / ETFE film.

[0172] The above evaluations were performed on each of the above release films. The results are shown in Tables 1 to 5. Examples 1-1 to 1-4, 1-6 to 1-7, 1-9 to 1-10, and 1-12 are examples. Examples 1-5, 1-8, 1-11, and 1-13 are comparative examples. Examples 2-1 to 2-4 are examples, and Examples 2-5 to 2-6 are comparative examples. Examples 2-7 to 2-8 are examples, and Examples 2-9 to 2-10 are comparative examples. Examples 2-11 to 2-12 are examples, and Examples 2-13 to 2-14 are comparative examples. Examples 2-15 to 2-16 are examples, and Examples 2-17 to 2-19 are comparative examples. Examples 3-1 and 3-2 are examples.

[0173]

[0174]

[0175]

[0176]

[0177]

[0178]

[0179]

[0180] Examples 1-1 to 1-13 are release films obtained by laminating an antistatic layer and a release layer on the mirror-surface side of a substrate having a mirror surface and a matte surface. In Examples 1-5, 1-8, and 1-11, where the release layer did not contain a conductive material, the surface resistance of the first surface of the release film (the surface facing the release layer and in contact with the curable resin) remained high. In Examples 1-1 to 1-4, 1-6, 1-7, 1-9, 1-10, and 1-12, the surface resistance of the first surface of the release film (the surface facing the release layer and in contact with the curable resin) could be reduced by incorporating a specific conductive material into the release layer. They also showed good transfer prevention properties. In Example 1-13, the release film in which the conductive material contained in the release layer was metal particles did not show good transfer prevention properties. The release films in Examples 1-1 to 1-3 exhibited better release properties than the release film in Example 1-4, which had a higher content of conductive material. Therefore, it can be said that the content of conductive material in the release layer should preferably be 4% by mass or less. In the evaluation of the release properties of the release films in Examples 1-1 to 1-3, the magnitude of the force required for peeling was Example 1-1 < Example 1-2 < Example 1-3. Note that in the evaluation of release properties, a smaller force required for peeling indicates better release properties. In the evaluation of the release properties of the release films in Examples 1-6 and 1-7, the magnitude of the force required for peeling was Example 1-6 < Example 1-7. In the evaluation of the release properties of the release films in Examples 1-9 and 1-10, the magnitude of the force required for peeling was Example 1-9 < Example 1-10. In the evaluation of the release properties of the release films in Examples 1-3, 1-7, and 1-10, the magnitude of the force required for peeling was Example 1-10 < Example 1-7 < Example 1-3. In Examples 1-3, 1-7, and 1-10, the release films have the same type and content of conductive material, but differ in the thickness of the release layer. However, even though the release layer was made thicker to improve release properties, the surface resistivity could be kept low because the release layer contained conductive material.

[0181] Examples 2-1 to 2-19 are release films obtained by laminating an antistatic layer and a release layer on one of the matte surfaces of a substrate, where both surfaces are matte. In Examples 2-5 to 2-6, 2-9 to 2-10, 2-13 to 2-14, and 2-17 to 2-19, where the release layer does not contain a conductive material, the surface resistance of the first surface of the release film (the surface on the release layer side, which is in contact with the curable resin) remained high. In Example 2-19, where the release layer was thinner than in Example 2-18, the release film was worse than in Example 2-18 in terms of coating penetration, release properties, and transfer prevention. In Examples 2-1 to 2-4, 2-7 to 2-8, 2-11 to 2-12, and 2-15 to 2-16, the release film's surface resistance on its first surface (the surface facing the release layer and in contact with the curable resin) was reduced by incorporating a conductive material into the release layer. In the release performance evaluation of Examples 2-1 to 2-3, the magnitude of the force required for peeling was Example 2-1 < Example 2-2 < Example 2-3. In the release performance evaluation of Examples 2-7 and 2-8, the magnitude of the force required for peeling was Example 2-7 < Example 2-8. In the release performance evaluation of Examples 2-11 and 2-12, the magnitude of the force required for peeling was Example 2-11 < Example 2-12. In the release performance evaluation of Examples 2-15 and 2-16, the magnitude of the force required for peeling was Example 2-16 < Example 2-15.

[0182] Examples 3-1 and 3-2 are release films obtained by laminating an antistatic layer and a release layer on the mirrored side of a substrate having a mirrored surface and a matte surface. Regardless of the type of resin of the substrate, the release films of Examples 3-1 and 3-2 were able to reduce the surface resistance of the first surface of the release film (the surface on the release layer side, which is the surface in contact with the curable resin) by incorporating a specific conductive material into the release layer. They also showed good transfer prevention properties.

[0183] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2024-199741, filed on 15 November 2024, the contents of which are incorporated herein by reference.

[0184] 10 Release film 1 Substrate 1A Substrate surface 1B Substrate surface 2 Antistatic layer 3 Release layer

Claims

1. A release film having a base material, an antistatic layer, and a release layer in that order, wherein the release layer contains at least one conductive material selected from a conductive polymer, an ionic liquid, a surfactant, a conductive metal oxide, a metal ion conductive salt, and a conductive carbon material.

2. The release film according to claim 1, wherein the conductive material comprises a surfactant or a conductive carbon material.

3. The release film according to claim 1 or 2, wherein the surfactant comprises a polymer having a quaternary ammonium salt structure.

4. The release film according to claim 1 or 2, wherein the antistatic layer contains an antistatic agent, and both the antistatic agent and the conductive material in the release layer are polymers.

5. The release film according to claim 1 or 2, wherein the release layer comprises at least one selected from a (meth)acrylic polymer, an epoxy polymer, and a urethane polymer.

6. The release film according to claim 5, wherein the release layer contains a (meth)acrylic polymer and the conductive material is a (meth)acrylic polymer having a quaternary ammonium salt structure.

7. The release film according to claim 1 or 2, wherein the average thickness of the release layer is 2.5 μm or more.

8. The total mass of the release layer and the antistatic layer is 2 g / m². ２ The release film according to claim 1 or 2.

9. The release film according to claim 4, wherein the antistatic agent is a conductive polymer, and the conductive material in the release layer is a polymer having a quaternary ammonium salt structure.

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