Dry film and cured product

Abstract

Provided is a dry film which is highly filled with a filler and is unlikely to cause dents when a protective film is laminated. An aspect of the present invention is a dry film comprising a first film and a resin layer laminated on the first film. The resin layer is formed from a resin composition containing an epoxy resin, a curing agent, an inorganic filler, and an elastomer. Based on the total solid content of the resin composition, the content of the inorganic filler is 60.0-90.0 mass%, and the content of the elastomer is 1.0-20.0 mass%. When a melt viscosity curve of the resin layer is created, a minimum point of the melt viscosity curve exists in a range of 50-120 °C, a melt viscosity (A2) at the minimum point is 100 Pa·s or more, and a ratio (A3 / A1) of a melt viscosity (A3) at 120 °C to a melt viscosity (A1) at 50 °C is 1.0 or more.

Description

Dry film and cured product

[0001] The present invention relates to a dry film and a cured product.

[0002] With the trend of miniaturization and high performance of electronic devices in recent years, the wiring density in printed wiring boards has been increasing. Along with this, the demand for improving the reliability by enhancing the heat resistance of laminated substrates for wiring and the like has been intensifying. In particular, in semiconductor package substrates, warpage caused by the difference in the coefficient of thermal expansion between the chip and the substrate during component mounting or package assembly has become a major issue, and thus a lower coefficient of thermal expansion is required.

[0003] Under such demands, technologies have been developed to achieve a lower coefficient of thermal expansion using materials with a high filler content. For example, in Patent Document 1, an ultraviolet curable sheet material having characteristics such as a filler content of 45% by volume or more of the entire resin composition and a low coefficient of thermal expansion is disclosed.

[0004] Japanese Patent Application Laid-Open No. 2014-XXX636

[0005] Here, as one of the means for forming protective films and insulating layers such as solder resist and interlayer insulating layers provided on printed wiring boards used in electronic devices and the like, dry films (laminated films) are used. Also, usually, a protective film is laminated on the dry film to prevent dust adhesion during storage or transportation. However, when laminating a protective film on a dry film with a high filler content, there has been a problem that indentations can occur due to the influence of the filler. When indentations occur on the protective film, not only does it result in poor appearance, but there is also a problem that when peeling the resin layer from the protective film, transfer of the resin layer to the protective film (so-called crying separation) is likely to occur.

[0006] Therefore, an object of the present invention is to provide a dry film with a high filler content that is less likely to cause indentations when a protective film is laminated, and a cured product obtained using the dry film.

[0007] One embodiment of the present invention is a dry film comprising a first film and a resin layer laminated on the first film. The resin layer is formed from a resin composition comprising an epoxy resin, a curing agent, an inorganic filler, and an elastomer. Based on the total solid content of the resin composition, the inorganic filler content is 60.0 to 90.0% by mass, and the elastomer content is 1.0 to 20.0% by mass. When a melt viscosity curve of the resin layer is prepared according to the measurement method described below, the minimum point of the melt viscosity curve is in the range of 50 to 120°C, the melt viscosity (A2) at the minimum point is 100 Pa·s or more, and the ratio (A3 / A1) of the melt viscosity at 50°C (A1) to the melt viscosity at 120°C (A3) is 1.0 or more. (Measurement method) The sample thickness is adjusted to a range of 300 to 400 μm, and the change in viscous resistance is measured using a rheometer at a heating rate of 5 °C / min in the temperature range of 40 to 140 °C.

[0008] The D90 of the inorganic filler is preferably 3.0 μm or less. The mass loss rate when the resin layer is heated at 100°C for 20 minutes is preferably 0.5 to 4.0% by mass.

[0009] Another embodiment of the present invention is a cured product obtained by curing the resin layer of the dry film.

[0010] The present invention provides a dry film with a high filler content that is less prone to dents when a protective film is laminated over it, and a cured product obtained using the dry film.

[0011] In this specification, if isomers exist for the compounds described, all possible isomers are usable in the present invention unless otherwise specified.

[0012] Where the upper and lower limits of a numerical range are described separately in this specification, all combinations of each lower limit and each upper limit shall be substantially described to the extent that they are not inconsistent.

[0013] In this specification, the term "solids" is used to mean non-volatile components (components other than volatile components such as solvents).

[0014] In this specification, components contained in a resin composition and their content may be described without distinction from components contained in a resin layer which is a dried coating film of the resin composition and their content.

[0015] In this specification, unless otherwise specified, any compound listed as a component is disclosed in this specification in both a form in which the listed compound is used alone and in a form in which two or more of the listed compounds are used in appropriate combinations.

[0016] For each component described herein, if a commercially available product exists, a commercially available product may be used as needed.

[0017] The structure, physical properties, manufacturing method, and applications / usage methods of the dry film relating to this disclosure will be described below. The present invention is not limited to these.

[0018] <<<Structure>>> The dry film according to this disclosure comprises a first film (base film) and a resin layer laminated on the first film and formed of a resin composition.

[0019] More specifically, the dry film according to this disclosure comprises a resin layer obtained by applying a resin composition to at least one surface of a first film and then drying it. Preferably, the dry film has a second film (protective film) laminated on top of the resin layer.

[0020] The thickness (film thickness) of the resin layer is not particularly limited, but is preferably 10 μm or more, 20 μm or more, or 30 μm or more, and preferably 500 μm or less, 400 μm or less, or 300 μm or less.

[0021] The first film (base film) and the second film (protective film) can be known films used for dry films.

[0022] The first film is one that serves to support the resin layer of the dry film, and when the dry film is laminated onto a substrate such as a circuit board by heating or other means to form an integral molded product, it refers to a film that is laminated to at least the resin layer.

[0023] Examples of the first film include thermoplastic films such as polyester films made of polyethylene terephthalate. The first film may be subjected to appropriate surface treatment.

[0024] The thickness of the first film is not particularly limited, but is preferably 1 μm or more, 2 μm or more, or 5 μm or more, and is also preferably 200 μm or less, 150 μm or less, or 100 μm or less.

[0025] The second film is provided on the side of the resin layer opposite the first film to the dry film, with the purpose of preventing dust and other debris from adhering to the surface of the resin layer and improving handling. When the second film is laminated onto a substrate such as a circuit board by heating or other means to form an integral molded product with the resin layer side of the dry film in contact with it, it is peeled off from the resin layer before lamination.

[0026] Examples of the second film include polyethylene film and polypropylene film. The second film may be subjected to appropriate surface treatment. The first and second films may be made of the same material or different materials, but it is preferable that the second film has less adhesion to the resin layer than the first film.

[0027] The thickness of the second film is not particularly limited, but is preferably 1 μm or more, 5 μm or more, or 10 μm or more, and is preferably 200 μm or less, 100 μm or less, or 50 μm or less.

[0028] Next, we will describe the resin composition that forms the resin layer.

[0029] <<Resin Composition>> The resin composition preferably contains epoxy resin, a curing agent, an inorganic filler, and an elastomer. The resin composition may also contain other components. The following describes each component.

[0030] <Epoxy Resin> The epoxy resin is not particularly limited as long as it has two or more epoxy groups in its molecule, and conventionally known epoxy resins can be used.

[0031] Examples of epoxy resins include bisphenol-type epoxy resins (e.g., bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol E type epoxy resin, brominated bisphenol A type epoxy resin, bisphenol S type epoxy resin), hydrogenated bisphenol-type epoxy resins (e.g., hydrogenated bisphenol A type epoxy resin), phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin, biphenyl type epoxy resin, naphthol type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, triphenylmethane type epoxy resin, alicyclic epoxy resin, aliphatic chain epoxy resin, phosphorus-containing epoxy resin, anthracene type epoxy resin, norbornene type epoxy resin, adamantane type epoxy resin, fluorene type epoxy resin, aminophenol type epoxy resin, aminocresol type epoxy resin, and alkylphenol type epoxy resin.

[0032] The epoxy resin is preferably present in an amount of 1.0% by mass or more, 2.0% by mass or more, or 5.0% by mass or more, based on the total solid content of the resin composition, and is also preferably present in an amount of 35.0% by mass or less, 25.0% by mass or less, or 15.0% by mass or less.

[0033] <Curing agent> The curing agent is not particularly limited, and conventionally known curing agents used in combination with epoxy resins can be used.

[0034] Examples of curing agents include phenolic resins, polycarboxylic acids and their acid anhydrides, cyanate ester resins, activated ester resins, melamine, triazine-containing resins, amines such as tertiary amines and polyamines, polyamide resins, dicyandiamides, and polymercaptans.

[0035] The curing agent is preferably a phenolic resin. Examples of phenolic resins include phenol novolac resins, alkylphenol novolac resins, bisphenol A novolac resins, dicyclopentadiene type phenolic resins, Xylok type phenolic resins, terpene-modified phenolic resins, cresol / naphthol resins, polyvinylphenols, phenol / naphthol resins, α-naphthol skeleton-containing phenolic resins, triazine-containing cresol novolac resins, and the like.

[0036] The curing agent content is preferably 5 parts by mass or more, 10 parts by mass or more, or 20 parts by mass or more, and also preferably 50 parts by mass or less, 40 parts by mass or less, or 35 parts by mass or less, when the epoxy resin content in the resin composition is 100 parts by mass.

[0037] <Inorganic Fillers> Inorganic fillers that can be used include metal oxides such as alumina and titanium oxide; metal hydroxides such as aluminum hydroxide and magnesium hydroxide; clay minerals such as talc and mica; fillers with a perovskite crystal structure such as barium titanate and strontium titanate; and silica, boron nitride, aluminum borate, barium sulfate, calcium carbonate, etc.

[0038] The inorganic filler is preferably silica.

[0039] Silica may be surface-treated with a coupling agent. By treating the surface with a silane coupling agent, the dispersibility with respect to other components can be improved. As the silane coupling agent, for example, an epoxy silane coupling agent, a mercapto silane coupling agent, a vinyl silane coupling agent, etc. can be used. As the epoxy silane coupling agent, for example, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, etc. can be used. As the mercapto silane coupling agent, for example, γ-mercaptopropyltriethoxysilane, etc. can be used. As the vinyl silane coupling agent, for example, vinyltriethoxysilane, etc. can be used.

[0040] The average particle size of the inorganic filler (for example, silica) is preferably 0.01 μm or more, 0.05 μm or more, or 0.1 μm or more, and is preferably 2.5 μm or less, 2.0 μm or less, or 1.5 μm or less. Here, the average particle size can be determined as the median diameter (D50, volume basis) by cumulative distribution from the measured values of the particle size distribution by the laser diffraction / scattering method using a commercially available laser diffraction / scattering type particle size distribution measuring device. Also, the average particle size of the inorganic filler (for example, silica) shall indicate the value measured as described above for the powdery material before preparing (preliminary stirring, kneading) the resin composition.

[0041] Further, the D90 (volume basis) of the inorganic filler in the cumulative distribution described above is preferably 3.0 μm or less, 2.5 μm or less, or 2.0 μm or less. The lower limit value of D90 is not particularly limited, but for example, it is 0.1 μm.

[0042] By using such an inorganic filler, it becomes easy to form a resin layer having excellent performance and a predetermined melt viscosity characteristic.

[0043] The content of the inorganic filler is preferably 60.0% by mass or more, 65.0% by mass or more, 70.0% by mass or more, 72.0% by mass, or 75.0% by mass or more, based on the total solid content of the resin composition, and is also preferably 90.0% by mass or less, 89.0% by mass or less, 88.0% by mass or less, 87.0% by mass or less, or 85.0% by mass or less. By setting the content of the inorganic filler within such a range, the filler is highly filled, and it becomes easier to form a resin layer having predetermined melt viscosity characteristics.

[0044] Also, the content of the inorganic filler is preferably 30.0% by volume or more, 40.0% by volume or more, 50.0% by volume or more, or 55.0% by volume, based on the total solid content of the resin composition, and is also preferably 85.0% by volume or less, 80.0% by volume or less, or 75.0% by volume or less.

[0045] <Elastomer> The elastomer is not particularly limited, and conventionally known ones can be used.

[0046] Examples of the elastomer include diene synthetic rubbers (such as polyisoprene rubber, polybutadiene rubber, styrene-butadiene rubber, polychloroprene rubber, nitrile rubber, ethylene-propylene rubber, etc.), non-diene synthetic rubbers (such as ethylene-propylene rubber, butyl rubber, acrylic rubber, polyurethane rubber, fluorine rubber, silicone rubber, epichlorohydrin rubber, etc.), natural rubber, styrene-based elastomers, olefin-based elastomers, urethane-based elastomers, polyester-based elastomers, polyamide-based elastomers, acrylic-based elastomers, and silicone-based elastomers, as well as those obtained by modifying these.

[0047] The content of the elastomer is preferably 1.0% by mass or more, 1.1% by mass or more, or 1.2% by mass or more, based on the total solid content of the resin composition, and is also preferably 20.0% by mass or less, 18.0% by mass or less, or 16.0% by mass or less. By setting the content of the elastomer within such a range, it becomes easier to form a resin layer having predetermined melt viscosity characteristics.

[0048] <Other Components> The resin composition may contain other components. Examples of other components include conventionally known additives such as curing accelerators, colorants, defoamers, leveling agents (surface modifiers), adhesion promoters, flame retardants, thickeners, anti-aging agents, antioxidants, and catalysts, as well as organic solvents. The resin composition may also contain resin materials other than epoxy resin as needed. The content of other components can be appropriately changed depending on the application.

[0049] The resin composition according to this disclosure preferably contains a curing accelerator. The curing accelerator is a component that promotes the curing reaction of epoxy resin alone, or the curing reaction of epoxy resin with a resin other than epoxy resin. Examples of curing accelerators include imidazole derivatives such as imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 4-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, and 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole; hydrazine compounds such as adipic acid dihydrazide and sebacate acid dihydrazide; and phosphorus compounds such as triphenylphosphine.

[0050] The content of the curing accelerator is preferably 0.1 parts by mass or more, 0.2 parts by mass or more, or 0.5 parts by mass or more, and also preferably 10 parts by mass or less, 5 parts by mass or less, or 2 parts by mass or less, when the epoxy resin content in the resin composition is 100 parts by mass.

[0051] <<<Physical Properties>>> <<Mass Loss Rate>> The mass loss rate when the resin layer is heated at 100°C for 20 minutes is preferably 0.5 to 4.0 mass%, and more preferably 1.0 to 3.5 mass%. By setting the mass loss rate within this range, it becomes easier to form a resin layer having a predetermined melt viscosity characteristic. The mass loss rate is calculated as ([Mass of the resin layer before heating] - [Mass of the resin layer after heating]) / [Mass of the resin layer before heating].

[0052] Furthermore, in measuring this mass loss rate, the lost mass is considered to be approximately equal to the mass of solvent remaining in the resin layer. Therefore, this mass loss rate can be expressed as the amount of solvent remaining in the resin layer.

[0053] The mass loss rate can be adjusted by factors such as the coating thickness of the resin composition, the drying temperature and drying time when forming the resin layer, etc. For example, when the coating thickness of the resin composition is increased and drying is performed, solvent tends to remain inside the resin layer, and the mass loss rate (amount of residual solvent) tends to increase.

[0054] <<Melting Viscosity>> When a melting viscosity curve of the resin layer is created according to the method described later, it is preferable that at least one or all of the following (1) to (3) be satisfied. (1) The minimum point of the melting viscosity curve is located in the range of 50 to 120°C, 60 to 115°C, or 80 to 110°C. (2) The melting viscosity (A2) at the minimum point is 100 Pa·s or more. The upper limit of the melting viscosity (A2) is not particularly limited, but for example, it is 40,000 Pa·s or 20,000 Pa·s. If there are multiple minimum points, the one with the smallest melting viscosity value is used. (3) The ratio (A3 / A1) of the melting viscosity at 50°C (A1) to the melting viscosity at 120°C (A3) is 1.0 or more, 1.2 or more, or 1.5 or more. The upper limit of A3 / A1 is not particularly limited, but for example, it could be 200.0, 150.0, or 120.0.

[0055] (Method for measuring melt viscosity) Multiple resin layers are stacked as needed to create a sample. The sample thickness (gap) is adjusted to a range of 300 to 400 μm, and the change in viscous resistance is measured using a rheometer at a heating rate of 5°C / min in the temperature range of 40 to 140°C. For example, a rheometer manufactured by HAAKE (product name "RheoStressRS-6000") can be used. The measurement is performed under the following conditions: oscillation heating method (5°C / min), frequency: 1 Hz, stress control: 3 Pa, parallel plate: 20 mm.

[0056] With dry films possessing these characteristics, although the detailed reasons are unclear, it is thought that the aggregation of inorganic fillers near the surface of the resin layer is moderately suppressed, which tends to make it less likely for dents to occur when a protective film is laminated.

[0057] The properties related to melt viscosity can be adjusted by the thickness of the resin layer (coating thickness of the resin composition), the temperature at which the resin composition is dried, the content of elastomer, inorganic filler, curing agent, and curing accelerator in the resin composition, and the type of epoxy resin. For example, when the coating thickness of the resin composition is thick, as mentioned above, the amount of residual solvent in the resin layer may increase, and the heat generated during drying the resin composition is less likely to reach the center of the resin composition, thus reducing the unintended curing effect due to heat during drying. Therefore, the thicker the coating thickness of the resin composition, the lower the melt viscosity tends to be. Also, the lower the inorganic filler content, the lower the melt viscosity tends to be. Furthermore, when measuring the melt viscosity at 40 to 140°C, the curing of the epoxy resin due to heat progresses gradually, but when the curing accelerator content is low, the curing of the epoxy resin does not progress easily even when exposed to high temperatures, and the melt viscosity at 120°C tends to be low.

[0058] <<<Manufacturing Method>>> A dry film can be manufactured by applying a resin composition onto a first film and drying it. Alternatively, after drying the resin composition on the first film to form a resin layer, a second film may be laminated onto the resin layer.

[0059] The means for applying the resin composition are not particularly limited, and conventionally known methods such as blade coaters, lip coaters, comma coaters, and film coaters can be used.

[0060] The drying method for the resin composition is not particularly limited, and conventionally known methods such as hot air circulation drying ovens, IR ovens, hot plates, and convection ovens can be used. Furthermore, the drying conditions are not particularly limited and can be adjusted as appropriate considering the composition of the resin composition. As an example, drying can be carried out at a temperature of 25 to 130°C for 1 to 30 minutes.

[0061] <<<Applications / Method of Use>>> A cured product can be obtained by curing the resin layer of the dry film of this disclosure.

[0062] More specifically, a cured product can be obtained by laminating a resin layer of dry film onto a desired object and then heating the resin layer.

[0063] The heating conditions (curing conditions) can be adjusted as appropriate depending on the materials used. For example, the heating temperature is 120 to 200°C, and the heating time is 5 to 180 minutes.

[0064] The applications of the cured product relating to this disclosure are not particularly limited and can be applied to a variety of applications such as circuit boards, adhesives, paints, printing inks, coating materials, molding materials, pattern-forming materials, building materials, optical components, semiconductor devices, and display devices. Because the cured product relating to this disclosure is highly filled with inorganic fillers and has a low coefficient of thermal expansion, it is preferably applied as a material for constituting printed wiring boards used in electronic devices and the like.

[0065] Next, the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to these.

[0066] <<Raw Materials>> <Epoxy Resin> Product Name "R710" (Manufactured by Air Water Inc.) Product Name "jER828" (Manufactured by Mitsubishi Chemical Corporation) Product Name "ERP-4030" (Manufactured by ADEKA Corporation) Product Name "Epiclon HP-6000L" (Manufactured by DIC Corporation)

[0067] <Hardening agent> Product name: "HF-4M" (manufactured by Meiwa Kasei Co., Ltd.), phenol novolac resin

[0068] <Inorganic Fillers> Product name "Sciqas-LT" (manufactured by Sakai Chemical Industry Co., Ltd.), vinylsilane treated product product name "SP-01MS" (manufactured by Tokuyama Corporation), trimethylsilylsilane treated product product name "SO-C2" (manufactured by Admatex Co., Ltd.), untreated product product name "SP-15MS" (manufactured by Tokuyama Corporation), trimethylsilylsilane treated product

[0069] <Elastomers> Product name: Teisan Resin SG-80H (manufactured by Nagase ChemteX Corporation), MEK cut product, solids content 18% by mass, acrylic ester copolymer (functional groups: carboxyl group, hydroxyl group) Product name: ToughTec H1052 (manufactured by Asahi Kasei Corporation), hydrogenated styrene-based thermoplastic elastomer Product name: YX6954 (manufactured by Mitsubishi Chemical Corporation), phenoxy resin, cyclohexanone cut product, solids content 30% by mass

[0070] Regarding the product "ToughTec H1052" (manufactured by Asahi Kasei Corporation), it was mixed with cyclohexanone and heated at 70°C while stirring to obtain a solution with a solid content of 15% by mass, which was then used.

[0071] <Additives> Product name: "BYK-350" (manufactured by Bic Chemie Japan Co., Ltd.), acrylate-based surface modifier

[0072] <Curing Accelerator> Product name: "2E4MZ" (manufactured by Shikoku Chemicals Co., Ltd.), 2-ethyl-4-methylimidazole

[0073] <<Example 1>> <Preparation of Resin Composition> The epoxy resin shown in Table 1 was placed in a container, and a solvent mixed so that the volume ratio of diethylene glycol monoethyl ether acetate and cyclohexanone was 1:1 was added, and the mixture was stirred while heating to 50°C. After confirming that the epoxy resin had dissolved in the solvent, an inorganic filler was added and the mixture was stirred thoroughly to obtain a resin solution. The viscosity of the resin solution was measured using a rotational viscometer (measurement temperature: 25°C, rotation speed: 5 rpm), and it was confirmed that the viscosity was in the range of 5,000 to 20,000 mPa·s. If the viscosity exceeded 20,000 mPa·s, more solvent was added to the resin solution to adjust it to the above range. After that, the resin solution was kneaded in a three-roll mill, and then a curing agent, elastomer, additives, and curing accelerator were added, and the mixture was stirred thoroughly with a stirrer to obtain a resin composition. Table 1 shows the types of each raw material (epoxy resin, hardener, inorganic filler, elastomer, additive, curing accelerator), the amount of each raw material blended as solid content (parts by mass), and the D50 and D90 values ​​of the inorganic filler used.

[0074] <Formation of the Resin Layer> The resin composition was applied to the first film (support film, PET film) using a die coater. The first film used was product name "TN200" (manufactured by Toyobo Co., Ltd., thickness 38 μm). Next, the applied resin composition was dried in a hot air circulating drying oven to obtain a resin layer. When applying the resin composition, the application thickness was adjusted so that the film thickness of the resin layer after drying was the value shown in Table 1. Furthermore, taking the film thickness into consideration, the drying conditions in the hot air circulating drying oven were changed within the range of 70 to 120°C and 5 to 10 minutes so that the mass loss rate, described later, was the value shown in Table 1.

[0075] <Lamination of the second film> Using a laminator set to 50°C, the second film (protective film) was laminated onto the resin layer to obtain the dry film according to Example 1. This dry film has the first film (support film), resin layer, and second film (protective film) laminated in this order. Two types of second films were used: (1) "Alfan FG-201" (manufactured by Oji F-Tech Co., Ltd., OPP film, thickness 16 μm) and (2) "FSA-100M" (manufactured by Futamura Chemical Co., Ltd., OPP film, thickness 30 μm). As described later, Alfan FG-201 was used to prepare the dry film used for measuring the mass loss rate, and FSA-100M was used to prepare the dry film used for checking dents.

[0076] <<Examples 2-8, Comparative Examples 1-5>> Dry films according to Examples 2-8 and Comparative Examples 1-5 were prepared in the same manner as in Example 1, except that the types and amounts of each raw material were changed to those shown in Table 1, and the coating thickness was adjusted so that the film thickness of the resin layer after drying was as shown in Table 1.

[0077] <<Physical Property Measurement / Evaluation>> <Melting Viscosity> Based on the method described above, melting viscosity curves for the resin layer of each dry film were created, and the temperature of the minimum point of the melting viscosity curve, the melting viscosity at 50°C (A1), the melting viscosity at the minimum point (A2), the melting viscosity at 120°C (A3), and the ratio of the melting viscosity at 120°C to the melting viscosity at 50°C (A1) (A3 / A1) were measured. The measurement results are shown in Table 1.

[0078] <Mass Loss Rate> The mass loss rate of the resin layer in each example and comparative example was measured based on the following method. The measurement results are shown in Table 1.

[0079] The dry film with the product name "Alfan FG-201" laminated as the second film (protective film) was used as the measurement target. The second film was peeled off from the dry film, exposing the resin layer. The resin layer was laminated onto a 35 μm thick copper foil using a vacuum laminator called "CVP-300" (manufactured by Nikko Materials Co., Ltd.). At this time, the mass of the copper foil alone (M １ The total mass (M) of the copper foil and the resin layer was measured. The first film (support film) was peeled off from the resin layer. ２ The mass (M) of the copper foil and the dried resin layer was measured. The resin layer was dried at 100°C for 20 minutes. ３ The following was measured. The mass loss rate of the resin layer was calculated based on the following formula: Mass loss rate (mass%) = (M ２ -M ３ ) / (M ２ -M １ ) × 100

[0080] <Indentations> The presence or absence of indentations in the dry films of each example and comparative example was evaluated based on the following method. The evaluation results are shown in Table 1.

[0081] As a second film (protective film), a dry film laminated with product name "FSA-100M" was used as the evaluation subject. Dry film pieces were made by cutting the dry film into 20cm x 20cm pieces, and the number of bumps with a maximum diameter of 0.5mm or more was counted by visually observing the dry film pieces from both sides. The number of bumps was evaluated as follows: 0 to 1 bump was A, 2 to 10 bumps was B, and 11 or more bumps was C.

[0082]

[0083] From the above, it has been shown that even if the filler is highly filled (for example, the solid content ratio of inorganic filler in the resin composition or resin layer is 60% by mass or more), the occurrence of dents can be suppressed by making a dry film that satisfies the predetermined physical properties.

[0084] According to the present invention, a dry film is provided that is less prone to dents when a protective film is laminated, even if the filler is highly filled. In another view, the present invention provides a dry film with a protective film that is dent-free or has few dents. Therefore, the dry film according to this disclosure can be suitably applied to a variety of uses. Cross-reference of related applications

[0085] This application claims priority pursuant to Japanese Patent Application No. 2024-161569, filed with the Japan Patent Office on 19 September 2024, all of which disclosures are incorporated herein by reference in their entirety.

Claims

1. A dry film comprising a first film and a resin layer laminated on the first film, wherein the resin layer is formed from a resin composition containing an epoxy resin, a curing agent, an inorganic filler, and an elastomer, wherein, based on the total solid content of the resin composition, the inorganic filler content is 60.0 to 90.0% by mass, and the elastomer content is 1.0 to 20.0% by mass, and when a melt viscosity curve of the resin layer is prepared according to the measurement method described below, the minimum point of the melt viscosity curve is in the range of 50 to 120°C, the melt viscosity (A2) at the minimum point is 100 Pa·s or more, and the ratio (A3 / A1) of the melt viscosity at 50°C (A1) to the melt viscosity at 120°C (A3) is 1.0 or more. (Measurement method) The sample thickness is adjusted to a range of 300 to 400 μm, and the change in viscous resistance is measured using a rheometer at a heating rate of 5 °C / min in the temperature range of 40 to 140 °C.

2. The dry film according to claim 1, wherein the D90 of the inorganic filler is 3.0 μm or less.

3. The dry film according to claim 1, wherein the mass loss rate when the resin layer is heated at 100°C for 20 minutes is 0.5 to 4.0% by mass.

4. A cured product obtained by curing the resin layer of the dry film according to claim 1.

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