Method for producing cured film, printed wiring board, and electronic device

Abstract

Provided is a method for producing a cured film having a large film thickness and a high Tg through light irradiation and thermal curing while suppressing the occurrence of cracks on the surface. The present invention pertains to a method for producing a cured film having a glass transition temperature (Tg) of 120°C or higher and a film thickness of 50 µm or more, the method comprising: a step for forming a temporarily cured film that exhibits an elongation at break of 7-200%, by applying a curable composition containing a compound having a (meth)acryloyl group and a compound having an epoxy group and irradiating the applied curable composition with light a plurality of times; and a step for thermally curing the temporarily cured film.

Description

Method for manufacturing a cured film, printed circuit board, and electronic device.

[0001] The present invention relates to a method for manufacturing a cured film, a printed circuit board, and an electronic device.

[0002] Electric vehicles (EVs) and drones require power electronics, which are power supply devices that provide relatively high voltage or high current. Electronic devices that require power electronics use printed circuit boards (PCBs), which are made by etching copper from copper plates or copper-clad laminates to form wiring. Solder resist is then formed on the outermost layer of the PCB as an insulating protective layer.

[0003] For PCBs requiring high current, relatively thick copper wiring is used to reduce wiring resistance and thus the size of the PCB. To insulate and protect such wiring, a thick solder resist film is necessary.

[0004] Incidentally, the use of compositions possessing both photocuring and thermocuring properties has been proposed as materials for solder resists (Patent Documents 1 and 2, etc.). Such compositions enable rapid and precise pattern formation due to their photocuring properties. Furthermore, such compositions can enhance the heat resistance and mechanical strength of the cured film due to their thermocuring properties.

[0005] A composition possessing both photocuring and thermocuring properties is applied to a substrate, a pre-cured film is formed by light irradiation, and then it is thermocured. Regarding the light irradiation of such a composition, Patent Document 3, which concerns adhesives, describes using a light intensity of 300 mW / m². ２ The above is described. Furthermore, Patent Document 4, which is also a document concerning adhesives, states that the illuminance at 365 nm is 100 mW / cm². ２ The cumulative light intensity should be 1000 mJ / cm². ２ It is stated that light should be shone on it.

[0006] Japanese Patent Publication No. 2016-204453, Japanese Patent Publication No. 2018-203912, Japanese Patent Publication No. 2017-066170, Japanese Patent Publication No. 2019-183165

[0007] The adhesives described in Patent Documents 3 and 4 typically form films with a thickness of only about 30 μm at most. Furthermore, the adhesive materials usually have low glass transition temperatures (Tg). In contrast, attempting to form a cured film with a greater thickness and a higher glass transition temperature (Tg) often resulted in cracking during heating.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a method for manufacturing a cured film that has a thick film thickness and a high Tg, while suppressing the occurrence of cracks on the surface, by light irradiation and heat curing. The present invention also aims to provide a wiring board and electronic equipment having a cured film manufactured by the above method.

[0009] To solve the above problems, one aspect of the present invention relates to a method for manufacturing a cured film, a printed circuit board, and an electronic device as described in [1] to

[10] below. [1] A method for manufacturing a cured film having a glass transition temperature (Tg) of 120°C or higher and a film thickness of 50 μm or higher, comprising the steps of: applying a curable composition containing a compound having a (meth)acryloyl group and an epoxy compound, and irradiating the applied curable composition with light multiple times to form a pre-cured film having a breaking elongation of 7% or more and 200% or less; and thermal curing the pre-cured film. [2] The method for manufacturing a cured film according to [1], wherein the pre-cured film has a breaking strength of 0.5 N or more and 20 N or less. [3] The method for manufacturing a cured film according to [1] or [2], wherein the application of the curable composition is performed by a non-contact type pattern forming method. [4] The method for producing a cured film according to any one of [1] to [3], wherein the curable composition is provided by providing a composition having a viscosity of 5 mPa·s or more and 100 mPa·s or less at the temperature at the time of application. [5] The method for producing a cured film according to any one of [1] to [4], wherein the curable composition is provided by providing a plurality of compositions including composition A, which contains a thermosetting agent or thermosetting accelerator for reacting the epoxy compound, and composition B, which contains the epoxy compound. [6] The method for producing a cured film according to any one of [1] to [5], wherein the curable composition is provided by providing a one-component composition containing a compound having a (meth)acryloyl group, the epoxy compound, and a thermosetting agent or thermosetting accelerator for reacting the epoxy compound. [7] The method for producing a cured film according to any one of [1] to [6], wherein the curable composition contains silica particles surface-treated with a silane coupling agent. [8] The method for producing a cured film according to any one of [1] to [7], wherein the cured film is an insulating material. A printed circuit board having a cured film manufactured by any of the manufacturing methods described in [9], [1], to [8]. An electronic device having the printed circuit board described in

[10] , [9].

[0010] The present invention provides a method for manufacturing a cured film, which produces a thick cured film with a high Tg by light irradiation and heat curing, while suppressing the occurrence of cracks on the surface.

[0011] Figure 1 is a schematic diagram showing the general configuration of the apparatus used in the example to apply the curable composition to the substrate and to irradiate the applied curable composition with light.

[0012] The embodiments of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments.

[0013] 1. One embodiment of the method for manufacturing a cured film relates to a method for manufacturing a cured film having a glass transition temperature (Tg) of 120°C or higher and a film thickness of 50 μm or higher. In this embodiment, a curable composition is irradiated with light to form a pre-cured film, and then the pre-cured film is heat-cured to produce a cured film.

[0014] The above curable composition comprises a photopolymerizable compound having a (meth)acryloyl group and a thermosetting epoxy compound. Details of the curable composition will be described later.

[0015] 1-1. Formation of a Pre-cured Film In this embodiment, in order to form a cured film with a large thickness, the curable composition is applied to the substrate and the applied curable composition is irradiated with light multiple times. Specifically, a curable composition that hardens (or thickens) by either light irradiation or heating is applied to the surface of the substrate (or the surface of a curable composition that has already been irradiated with light). Then, the applied curable composition is irradiated with light. By repeatedly applying the curable composition and irradiating with light, a pre-cured film with a thickness corresponding to the thickness of the cured film to be formed is formed.

[0016] In this embodiment, a pre-cured film having a break elongation of 7% to 200% is formed by repeatedly applying a curable composition and irradiating it with light.

[0017] A pre-cured film with a break elongation of 7% or more can be said to be in a state that is not too hard and can undergo plastic deformation. Such a pre-cured film can sufficiently relieve the stress caused by shrinkage during subsequent thermal curing, making it less prone to cracking during thermal curing. Cracks reduce the insulating properties of the cured film. Therefore, by making it less prone to cracking, dielectric breakdown can be reduced, and the insulating properties of the cured film can be improved. Furthermore, in such a pre-cured film, the curable composition has not completely hardened by light irradiation, and unreacted thermosetting compounds can move somewhat freely. By thermal curing such a pre-cured film, the thermosetting compounds react sufficiently with each other to form a crosslinked structure, and a cured film with a high Tg and high heat resistance can be formed. Therefore, the cured film formed in this way is very useful as an insulating protective layer such as solder resist. Moreover, since the next curable composition is applied to a curable composition that is not completely hardened, the adhesion between layers of the composition is also increased, and delamination of the cured film is less likely to occur. While there is no particular upper limit to the elongation at break, it is set to 200% or less from the viewpoint of forming a hardened film with a high Tg and less prone to cracking during heating.

[0018] From the above viewpoint, the elongation at break of the pre-cured film is preferably 7% to 200%, more preferably 10% to 100%, and even more preferably 30% to 60%.

[0019] Furthermore, the pre-cured film preferably has a tensile strength of 0.5 N or more and 20 N or less. A pre-cured film with a tensile strength of 20 N or less is in a state where the curable composition has not completely hardened, and unreacted thermosetting compounds can move freely to some extent. Therefore, during thermal curing, the thermosetting compounds react sufficiently with each other to form a cross-linked structure, and a cured film with a high Tg and high heat resistance can be formed. A pre-cured film with a tensile strength of 0.5 N or more can be said to have been cured by light irradiation to the extent that bleeding is unlikely to occur. In particular, the side of the pre-cured film closest to the substrate receives multiple light irradiations, so in order to sufficiently suppress bleeding, the tensile strength tends to be 0.5 N or more.

[0020] From the above viewpoint, the tensile strength of the pre-cured film is preferably 0.4 N or more and 25 N or less, more preferably 1 N or more and 20 N or less, and even more preferably 2 N or more and 10 N or less.

[0021] The elongation at break and strength at break of the partially cured film can be values ​​measured using a known load measuring instrument (such as a digital force gauge).

[0022] The elongation at break and tensile strength of the partially cured film can be adjusted by the composition of the curable composition and the conditions of light irradiation, etc.

[0023] The method for applying the curable composition is not particularly limited. The curable composition may be applied by a contact method or a non-contact method. Contact methods include bar coating, spin coating, and dip coating. Non-contact methods include inkjet, airbrush, spray coating, dispenser, and electrospray methods. The method for applying the curable composition is preferably one that allows for pattern formation during application, and from the viewpoint of controlling the pattern with high precision, the inkjet method is preferred.

[0024] Alternatively, when applying the curable composition, a pattern may not be formed. Instead, light irradiation may be performed via a photoresist or photomask, and then the pattern may be formed by development.

[0025] The curable composition may be provided by applying a one-component composition. Alternatively, the curable composition may be provided by applying a two-component (or more than two-component) composition prepared by separating the materials contained in the curable composition into other compositions. These compositions will be described later.

[0026] Light irradiation should be carried out under conditions that allow the photopolymerizable compounds contained in the curable composition to polymerize and crosslink. The light to be irradiated is not particularly limited, but ultraviolet light, especially ultraviolet light having a peak wavelength of 360 nm to 410 nm, is preferred.

[0027] The illuminance of the light being emitted is 50 W / cm². ２ More than 4000W / cm ２It is preferably the following, 300 W / cm ２ or more and 3000 W / cm ２ or less. When the illuminance is 50 W / cm ２ or more, the photopolymerizable compound can be sufficiently polymerized and crosslinked to sufficiently suppress bleeding. Also, the higher the illuminance, the more sufficiently the photopolymerizable compound reacts, and it is easier to increase the glass transition temperature (Tg) of the cured film. Also, the higher the illuminance, the easier it is to polymerize the photopolymerizable compound in the three-dimensional direction, resulting in a hard, low elongation-at-break, and low breaking strength uncured film that breaks before stretching. Furthermore, the higher the illuminance, the shorter the irradiation time to reach the required light amount, and the higher the productivity. When the illuminance is low, linear polymerization takes precedence over the crosslinking reaction. When the illuminance is 3000 W / cm ２ or less, it becomes easier to form a polymer with a long molecular chain by linear polymerization of the photopolymerizable compound, so that the elongation at break of the uncured film can be increased or the breaking hardness can be decreased.

[0028] The light amount per irradiation is preferably 100 mJ / cm ２ or more and 4000 mJ / cm ２ or less, more preferably 300 mJ / cm ２ or more and 3000 mJ / cm ２ or less. When the light amount is 100 mJ / cm ２ or more, the photopolymerizable compound can be sufficiently polymerized and crosslinked to sufficiently suppress bleeding. Also, the higher the illuminance, the more sufficiently the photopolymerizable compound reacts, and it is easier to increase the glass transition temperature (Tg) of the cured film. When the light amount is 4000 mJ / cm ２ or less, the polymerization and crosslinking of the photopolymerizable compound can be sufficiently suppressed, and the elongation at break of the uncured film can be increased or the breaking hardness can be decreased.

[0029] The conditions for light irradiation may be set according to the composition of the curable composition or the like so that a temporarily cured film having the above-described properties can be formed. For example, the elongation at break of the temporarily cured film can be increased as the illuminance of light irradiation is decreased. On the other hand, the breaking strength of the temporarily cured film can be decreased as the illuminance of light irradiation is increased. Also, the elongation at break of the temporarily cured film can be increased as the amount of light irradiated each time is decreased. On the other hand, the breaking strength of the temporarily cured film can be decreased as the amount of light irradiated each time is increased. By appropriately taking these balances, a temporarily cured film having desired properties can be obtained.

[0030] The type of the substrate is not particularly limited and may be selected according to the use of the cured film. For example, a printed wiring board (PCB) in which wiring is formed by etching copper of a copper plate or a copper-clad laminate, an aluminum substrate, a ceramic substrate, a plastic film-based flexible substrate, or the like can be used as the substrate.

[0031] 1-2. Thermal curing of the temporarily cured film Subsequently, the formed temporarily cured film is thermally cured.

[0032] The conditions for thermal curing are not particularly limited and may be determined according to the composition of the curable composition or the like. For example, it may be carried out at a temperature of 120°C or higher and 250°C or lower for a time of 10 minutes or longer and 5 hours or shorter. Also, a pre-bake may be carried out at a relatively low temperature (about 80°C) before the thermal curing.

[0033] 1-3. Curable composition The curable composition may be a composition containing a photopolymerizable compound and a thermosetting compound. The curable composition may contain a photoinitiator for polymerizing and crosslinking the photopolymerizable compound, and may further contain a photosensitizer, if necessary. Also, the curable composition may contain a thermosetting agent for crosslinking the thermosetting compound, and may further contain a thermosetting accelerator, if necessary. Also, the curable composition may contain a filler for enhancing the mechanical strength of the cured film, if necessary.

[0034] 1-3-1. Photopolymerizable compound A photopolymerizable compound is a compound that polymerizes or crosslinks by light irradiation with the assistance of a photoinitiator or the like, if necessary.

[0035] Photopolymerizable compounds enable rapid and precise pattern formation of curable compositions and improve the pattern accuracy of the cured film by suppressing bleeding. Furthermore, photopolymerizable compounds facilitate increasing the thickness of each layer of the pre-cured film formed by a single light irradiation. Additionally, because photopolymerizable compositions form a pre-cured film with high surface flatness upon light irradiation of the curable composition, the layer structure remains stable even after multiple applications of the curable composition and subsequent light irradiation.

[0036] The photopolymerizable compound may contain radical polymerizable compounds, cationic polymerizable compounds, or both. From the viewpoint of reducing the influence of humidity during photopolymerization, it is preferable that the photopolymerizable compound contains radical polymerizable compounds. Examples of radical polymerizable compounds include compounds having a (meth)acryloyl group, other compounds having vinyl groups, and compounds having maleimide gas. Examples of cationic polymerizable compounds include compounds having alicyclic epoxy groups and compounds having oxetane groups.

[0037] The photopolymerizable compound may include monofunctional compounds having only one functional group for polymerization or crosslinking within the molecule, or polyfunctional compounds having multiple such functional groups within the molecule, or both. From the viewpoint of the flexibility of the cured film, it is preferable that the photopolymerizable compound includes monofunctional compounds. Furthermore, from the viewpoint of the strength of the cured film, it is preferable that the photopolymerizable compound includes polyfunctional compounds.

[0038] For example, increasing the proportion of monofunctional compounds among the photopolymerizable compounds increases the elongation at break of the pre-cured film. Conversely, decreasing the proportion of monofunctional compounds among the photopolymerizable compounds decreases the tensile strength of the pre-cured film. Furthermore, using compounds with low glass transition temperatures as the monofunctional compounds increases the elongation at break of the pre-cured film. Conversely, using compounds with high glass transition temperatures as the monofunctional compounds decreases the tensile strength of the pre-cured film.

[0039] In this specification, (meth)acryloyl means acryloyl or methacryloyl, (meth)acrylate means acrylate or methacrylate, and (meth)acrylic means acrylic or methacrylic.

[0040] In this embodiment, the curable composition includes a compound having a (meth)acryloyl group as a photopolymerizable compound. The compound having a (meth)acryloyl group further improves the pattern accuracy of the cured film.

[0041] Examples of monofunctional compounds containing a (meth)acryloyl group include tetrahydrofurfuryl (meth)acrylate, 2-ethylhexyl (meth)acrylate, phenoxyethyl (meth)acrylate, isobornyl (meth)acrylate, 3-methyl-1,5-pentanediol (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, ethoxylated-o-phenylphenol (meth)acrylate, and 2-(meth)acryloyloxyethyl succinic acid.

[0042] Examples of polyfunctional compounds containing a (meth)acryloyl group include diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate with more than one ethylene oxide group, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate with more than one propylene oxide group, 1,3-butylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-Decanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, (meth)acrylic acid modified product of alkylene oxide adduct of bisphenol A, (meth)acrylic acid modified product of alkylene oxide adduct of bisphenol F, tricyclodecanedimethanol di(meth)acrylate, pentaerythritol di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, (meth)acrylic acid modified product of alkylene oxide modified product of trimethylolpropane, pentaerythritol tri(meth)acrylate, dipentaerythritol This includes di(meth)acrylate, trimethylolpropane tri((meth)acryloyloxypropyl) ether, (meth)acrylic acid modified products of alkylene oxide modified isocyanuric acid, dipentaerythritol propionate tri(meth)acrylate, tri((meth)acryloyloxyethyl) isocyanurate, sorbitol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, sorbitol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, sorbitol penta(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, sorbitol hexa(meth)acrylate, and acrylic acid modified products of alkylene oxide modified phosphazene, etc.

[0043] These photopolymerizable compounds may be used individually or in combination. The type and amount of photopolymerizable compounds can be determined according to the characteristics of the pre-cured film and the cured film.

[0044] The content of the photopolymerizable compound in the curable composition is preferably 10% by mass or more and 55% by mass or less based on the total mass of the curable composition. The above content of the photopolymerizable compound also includes the content of the photo / thermosetting compound described later. The higher the content of the photopolymerizable compound, the higher the accuracy of the pattern can be. On the other hand, the lower the content of the photopolymerizable compound, the higher the elongation at break of the pre-cured film and the lower the breaking strength. The above content of the photopolymerizable compound is more preferably 15% by mass or more and 50% by mass or less, and even more preferably 18% by mass or more and 45% by mass or less.

[0045] 1-3-2. Photopolymerization Initiators The photopolymerization initiator may contain a photoradical polymerization initiator, a photocationic polymerization initiator, or both. When the curable composition contains a radical polymerizable compound as the photopolymerizable compound, it is preferable to include a photoradical polymerization initiator as the photopolymerization initiator. When the curable composition contains a cationic polymerizable compound as the photopolymerizable compound, it is preferable to include a photocationic polymerization initiator as the photopolymerization initiator.

[0046] Photoradical polymerization initiators are compounds that generate radicals upon irradiation with light, thereby initiating the polymerization and crosslinking of radical polymerizable compounds.

[0047] Examples of photoradical polymerization initiators include benzoin compounds, alkylphenone compounds, acetophenone compounds, aminoacetophenone compounds, anthraquinone compounds, thioxanthone compounds, ketal compounds, acylphosphine oxide compounds, oxime ester compounds, and titanocene compounds.

[0048] Examples of benzoin compounds include benzoin, benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether.

[0049] Examples of alkylphenone compounds include 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2-benzyl-2-(dimethylamino)-4′-morpholinobutyrophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, 1-[4-(2-hydroxyethoxyl)-phenyl]-2-hydroxy-methylpropanone, 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, and 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one.

[0050] Examples of acetophenone compounds include acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, and 1,1-dichloroacetophenone.

[0051] Examples of aminoacetophenone compounds include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, and N,N-dimethylaminoacetophenone, among others.

[0052] Examples of anthraquinone compounds include 2-methylanthraquinone, 2-ethylanthraquinone, and 2-t-butylanthraquinone.

[0053] Examples of thioxanthone compounds include 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, and 2,4-diisopropylthioxanthone.

[0054] Examples of ketal compounds include acetophenone dimethyl ketal and benzyl dimethyl ketal.

[0055] Examples of acylphosphine oxide compounds include 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.

[0056] Examples of oxime ester compounds include 1,2-octanedione and 1-[4-(phenylthio)-2-(o-benzoyl oxime)]. Other examples include ethanone and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-1-(o-acetyl oxime).

[0057] Examples of titanocene compounds include bis(cyclopentadienyl)-diphenyl-titanium and bis(cyclopentadienyl)-dichloro-titanium. Other examples include bis(cyclopentadienyl)-bis(2,3,4,5,6-pentafluorophenyl)titanium and bis(cyclopentadienyl)-bis(2,6-difluoro-3-(pyrrole-1-yl)phenyl)titanium.

[0058] The content of the photoradical polymerization initiator in the curable composition can be 1% by mass or more and 10% by mass or less, based on the total mass of the radical polymerizable compound.

[0059] Photocationic polymerization initiators are compounds that generate acid (cations) upon irradiation with light, thereby initiating the polymerization and crosslinking of cationic polymerizable compounds. Known photoacid generators can be used as photocationic polymerization initiators. Examples of photocationic polymerization initiators include aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium, and phosphonium. ６ F ５ ) ４ － , PF ６ － AsF ６ － SbF ６ － , and CF３ SO ３ － This includes salts, sulfonates that generate sulfonic acid, halides that photocatalyze hydrogen halides, and iron allene complexes.

[0060] The content of the photocationic polymerization initiator in the curable composition can be 1% by mass or more and 10% by mass or less based on the total mass of the cationic polymerizable compound.

[0061] 1-3-3. Photosensitizer A photosensitizer absorbs light of a different wavelength than the excitation wavelength of the photopolymerization initiator and propagates the energy from the absorbed light to the photopolymerization initiator. This allows the photosensitizer to increase the curing rate of the curable composition and to allow the photopolymerizable compound to react sufficiently even in deeper layers (on the substrate side). As a result, the photosensitizer can improve the adhesion and surface hardness of the cured film.

[0062] Examples of photosensitizers include amines such as triethanolamine, methyldiethanolamine, triisopropanolamine, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, (2-dimethylamino)ethyl benzoate, (n-butoxy)ethyl 4-dimethylaminobenzoate, and 2-ethylhexyl 4-dimethylaminobenzoate, as well as cyanines, phthalocyanines, merocyanines, porphyrins, spiro compounds, ferrocene, fluorene, fluged, imidazole, perylene, phenazine, and phenothiazine. This includes compounds such as polyenes, azo compounds, diphenylmethane, triphenylmethane, polymethine acridine, coumarin, ketocoumarin, quinacridone, indigo, styryl, pyrylium compounds, pyrometene compounds, pyrazolotriazole compounds, benzothiazole compounds, barbiturate derivatives, and thiobarbiturate derivatives, as well as compounds described in European Patent No. 568993, U.S. Patent No. 4508811, U.S. Patent No. 5227227, Japanese Patent Publication No. 2001-125255, and Japanese Patent Publication No. 11-271969, etc.

[0063] The amount of photosensitizer in the curable composition can be 0.01% by mass or more and 10% by mass or less, based on the total mass of the curable composition.

[0064] 1-3-4. Thermosetting Compounds Thermosetting compounds are compounds that polymerize or crosslink upon heating in the presence of a thermosetting agent or thermosetting accelerator. Thermosetting compounds enhance the heat resistance and mechanical strength of the cured film.

[0065] The thermosetting compound can be a known compound, such as a compound having an epoxy group.

[0066] Examples of thermosetting compounds having epoxy groups include bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, biphenyl type epoxy resins, aliphatic type epoxy resins, and glycidylamine type epoxy resins. Of these, epoxy resins having aromatic rings are preferred from the viewpoint of improving the heat resistance, insulation, mechanical strength, and thermal expansion coefficient of the cured film. More specifically, bisphenol type epoxy resins, phenol novolac type epoxy resins, and cresol novolac type epoxy resins are preferred.

[0067] Furthermore, thermosetting compounds may include compounds that do not have epoxy groups. Examples of thermosetting compounds that do not have epoxy groups include phenolic resins, unsaturated polyesters, cyanate esters, urea resins, and diallyl phthalates.

[0068] The content of the thermosetting compound in the curable composition is preferably 10% by mass or more and 70% by mass or less based on the total mass of the curable composition. The higher the content of the thermosetting compound, the higher the heat resistance and mechanical strength of the cured film can be. The content of the thermosetting compound is more preferably 15% by mass or more and 60% by mass or less, and even more preferably 20% by mass or more and 40% by mass or less.

[0069] 1-3-5. Thermosetting Agents A thermosetting agent is a compound that promotes the curing of a composition by a thermosetting compound by reacting with epoxy groups, etc., present in the thermosetting compound and crosslinking the thermosetting compounds together.

[0070] The thermosetting agent can be a known compound such as an acid anhydride, amine compound, modified polyamine compound, phenol compound, and isocyanate compound.

[0071] Examples of acid anhydrides used as thermosetting agents include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylbutenyltetrahydrophthalic anhydride, methylnadic anhydride, dodecyl succinic anhydride, chlorendic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic anhydride, methylcyclohexenetetracarboxylic anhydride, trimellitic anhydride, and polyazelaic anhydride.

[0072] Examples of amine compounds used as thermosetting agents include aliphatic amines, alicyclic amines, aromatic amines, hydrazides, and guanidine derivatives.

[0073] Examples of modified polyamine compounds used as thermosetting agents include epoxy compound-added polyamines (reaction products of epoxy compounds and polyamines), Michael-added polyamines (reaction products of α,β unsaturated ketones and polyamines), Mannich-added polyamines (condensates of polyamines with formalin and phenol), thiourea-added polyamines (reaction products of thiourea and polyamines), and ketone-blocked polyamines (reaction products of ketone compounds and polyamines).

[0074] Examples of phenol compounds used as thermosetting agents include bis(4-hydroxyphenyl)-2,2-propane, 4,4′-dihydroxybenzophenone, bis(4-hydroxyphenyl)-1,1-ethane, and bis(4-hydroxyphenyl)-1,1-isobutane. Also included are polyhydric phenols such as bis(4-hydroxy-tert-butyl-phenyl)-2,2-propane, bis(2-hydroxynaphthyl)methane, and 1,5-dihydroxynaphthalene, as well as polyfunctional phenols such as phenol novolac resins, bisphenol novolac resins, and cresol novolac resins.

[0075] Examples of isocyanate compounds used as thermosetting agents include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, phenylene diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, phenyl isocyanate, 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, and 1,1-bis(acryloyloxymethyl)ethyl isocyanate. From the viewpoint of improving the storage stability of the composition, these isocyanates are preferably so-called blocked isocyanates, which are protected by a blocking group.

[0076] Examples of the blocking agents mentioned above include carboxylic acid esters, active methylene compounds, oxime compounds, monohydric alcohols or their isomers, glycol derivatives, phenols or their isomers, hydroxyl group-containing esters, amine compounds, alcoholamines, lactams, mercaptans, imidazoles, acid amides, acid imides, and urea compounds.

[0077] The amount of thermosetting agent in the curable composition is preferably 0.1 equivalents or more and 1.5 equivalents or less, and more preferably 0.8 equivalents or more and 1.2 equivalents or less, in terms of equivalent ratio to the epoxy equivalent of the thermosetting compound.

[0078] 1-3-6. Thermosetting accelerators Thermosetting accelerators are catalysts used to adjust the curing rate without reacting with the thermosetting composition.

[0079] The thermosetting accelerator can be a known compound such as tertiary amines and their salts, imidazole derivatives, phosphine compounds and phosphonium hydrochloride anhydride, amine compounds, modified polyamine compounds, and phenol compounds. Of these, tertiary amines or their salts and imidazole derivatives are preferred due to their high solubility, reactivity, and latent properties in the composition.

[0080] Examples of tertiary amines and their salts include 1,8-diazabicyclo(5,4,0)-undecene-7 (DBU) and its organic acid salts, 1,5-diazabicyclo(4,3,0)-nonene-5 (DBN) and its organic acid salts, 2,4,6-tris(dimethylaminomethyl)phenol, piperidine, N,N-dimethylpiperazine, triethylenediamine, benzyldimethylamine, and 2-(dimethylaminomethyl)phenol. Examples of the above organic acids include 2-ethylhexanoic acid, phenol, formic acid, o-phthalic acid, and p-toluenesulfonic acid.

[0081] Examples of imidazole derivatives include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 4-phenylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, 6-(2-(2-undecyl-1H-imidazole-1-yl)ethyl)-1,3,5-triazine-2,4-diamine, 6-[2-(2-methyl-1H-imidazole-1-yl)ethyl]-1,3,5-triazine-2,4-diamine, and 1-cyanoethyl-2-ethyl-4-methylimidazole.

[0082] Examples of phosphine compounds and phosphonium salts include tributylphosphine, triphenylphosphine, benzyltriphenylphosphonium bromide, ethyltriphenylphosphonium methanesulfonate, tetraphenylphosphonium tetraphenylborate, and tetra-n-butylphosphonium tetraphenylborate.

[0083] The content of the thermosetting accelerator in the curable composition is preferably 0.1% by mass or more and 5.0% by mass or less, and more preferably 0.1% by mass or more and 2.0% by mass or less, based on the total mass of the thermosetting compound. Note that the total mass of the thermosetting compound includes the mass of the photo / thermosetting compound.

[0084] 1-3-7. Photo- / thermosetting compound curable compositions may contain compounds that react and cure the composition upon either light irradiation or heating (hereinafter also simply referred to as "photo- / thermosetting compounds").

[0085] Photopolymerizable / thermosetting compounds can react with both photopolymerizable and thermosetting compounds. Therefore, photopolymerizable / thermosetting compounds can bond these polymers together, thereby increasing the toughness, mechanical strength, reducing delamination, and improving heat resistance of the cured product.

[0086] Photo- and thermosetting compounds can be compounds that contain both a vinyl group that reacts upon light irradiation and an epoxy group that reacts upon heating within their molecules. Preferably, photo- and thermosetting compounds are compounds that contain both a (meth)acryloyl group and a glycidyl group within their molecules.

[0087] Examples of compounds containing both a (meth)acryloyl group and a glycidyl group within their molecule include glycidyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate glycidyl ether.

[0088] The photo- / thermosetting compound may be a partial (meth)acrylic compound of an epoxy compound or a urethane-modified (meth)acrylic epoxy compound. Examples of partial (meth)acrylic compounds of epoxy compounds include compounds obtained by reacting some of the epoxy groups of novolac-type epoxy compounds and bisphenol-type epoxy compounds with (meth)acrylic acid.

[0089] The content of the photo / thermosetting compound in the curable composition is preferably 0.5% by mass or more and 30% by mass or less, based on the total mass of the curable composition. The higher the content of the photo / thermosetting compound, the more pronounced the above-mentioned effect of the photo / thermosetting compound becomes. By limiting the content of the photo / thermosetting compound to 30% by mass or less, the cured film can be made harder and its heat resistance can be improved. More preferably, the content of the above-mentioned photo / thermosetting compound is 1% by mass or more and 30% by mass or less.

[0090] 1-3-8. Fillers increase the mechanical strength of the cured film. In particular, fillers can reduce the coefficient of thermal expansion of the cured film, thereby improving its heat resistance.

[0091] On the other hand, according to the inventors' new findings, fillers are prone to cracking during thermal curing, and can reduce the adhesive strength at the lamination interface, making the cured film more susceptible to delamination. Therefore, when producing a cured film using a curable composition containing fillers, adjusting the physical properties of the pre-cured film to the above-mentioned range has a significant effect in reducing the likelihood of cracking and delamination.

[0092] The type of filler is not particularly limited. Examples of fillers include particles of silica, alumina, titanium oxide, aluminum hydroxide, zinc oxide, zirconium oxide, magnesium oxide, mica, bismuth oxychloride, talc, kaolin, barium sulfate, anhydrous silicic acid, calcium carbonate, magnesium carbonate, magnesium silicate, aluminum silicate, magnesium aluminum silicate, silicon carbide, silicon nitride, boron nitride, glass powder, metal oxides, and metals. Fillers may be hollow or solid particles.

[0093] The average particle size of the filler is preferably 0.1 μm or more and 2 μm or less, and more preferably 0.1 μm or more and 1 μm or less. Furthermore, the maximum particle size of the filler is preferably 2 μm or less. If the average particle size of the filler is 0.1 μm or more, the viscosity of the curable composition (or the composition that forms its material) is less likely to become high. Also, if the average particle size and maximum particle size of the filler are 2 μm or less, ejection from the nozzle of the inkjet head is easier when applying the composition by inkjet method. Furthermore, if the average particle size and maximum particle size of the filler are 2 μm or less, filler sedimentation in the composition is less likely to occur.

[0094] In this specification, the average particle diameter of the filler is the particle diameter at 50% of the cumulative value in the volume-based particle size distribution, measured by laser diffraction / scattering. The average particle diameter can be the value measured by, for example, a laser scattering diffraction particle size distribution analyzer (Malvern, Zetasizer Nano S90).

[0095] The filler is preferably surface-treated, and more preferably surface-treated with a silane coupling agent. In particular, when the filler is silica particles, surface treatment (especially surface treatment with a silane coupling agent) is preferred. Surface-treated fillers have their surface functional groups sealed by the surface treatment agent (silanol groups in the case of a silane coupling agent), making interparticle interactions less likely to occur in the composition. This facilitates ejection from the nozzle of the inkjet head when applying the composition by inkjet method. Furthermore, because aggregation is less likely to occur in the curable composition, the elongation at break of the pre-cured film tends to be high, and the tensile strength tends to be low.

[0096] The filler content in the curable composition is preferably 3% by mass or more and 40% by mass or less based on the total mass of the curable composition. The higher the filler content, the higher the mechanical strength and heat resistance of the cured film can be. The filler content is more preferably 5% by mass or more and 30% by mass or less.

[0097] 1-3-9. Other components of the curable composition may include water, organic solvents, bonding aids such as coupling agents, pigments, dyes, leveling agents, defoamers, and polymerization inhibitors.

[0098] Furthermore, the photopolymerizable compounds and some thermosetting compounds mentioned above are themselves liquids and can act as reactive diluents. Therefore, the water content in the curable composition is preferably 0% to 1% by mass, more preferably 0% to 0.5% by mass, and even more preferably 0% to 0.2% by mass, based on the total mass of the curable composition. In addition, the water content in the curable composition is preferably 0% to 5% by mass, more preferably 0% to 1% by mass, and even more preferably 0% to 0.5% by mass, based on the total mass of the curable composition.

[0099] 1-3-10. Physical Properties The application of the curable composition is preferably carried out by applying a composition (if it is a two-component composition, each of composition A, composition B, etc.) having a viscosity of 5 mPa·s or more and 100 mPa·s or less at the application temperature. The lower the viscosity at the application temperature, the easier it is to follow the irregularities of the substrate or the surface of the curable composition that has already been applied and irradiated with light, and the less likely it is to cause voids in the cured film due to the irregularities. In addition, the lower the viscosity at the application temperature, the easier it is to apply by methods such as inkjet printing, and the accuracy of the pattern can be improved. The viscosity of the curable composition at the application temperature is more preferably 5 mPa·s or more and 30 mPa·s or less, even more preferably 5 mPa·s or more and 10 mPa·s or less, and particularly preferably 5 mPa·s or more and 10 mPa·s or less.

[0100] 1-3-11. One-component and multi-component curable compositions: The curable composition only needs to be applied to the surface of the substrate (or the surface of the curable composition that has already been irradiated with light) before light irradiation when forming a pre-cured film. As described above, a one-component curable composition containing the above-mentioned components may be applied. Alternatively, a composition A containing any of the above-mentioned components and a composition B (and further compositions C, D, etc.) containing any of the others may be applied separately to prepare a curable composition containing the above-mentioned components on the surface.

[0101] When providing a multi-component composition, it is preferable to include a thermosetting accelerator and a thermosetting compound in a separate composition. This prevents the thermosetting compound from reacting during storage of the composition, thereby extending the pot life of the composition.

[0102] Alternatively, the multi-component composition is preferably a plurality of compositions comprising composition A containing the above-mentioned thermosetting agent or thermosetting accelerator, and composition B containing the above-mentioned thermosetting compound (particularly a compound having an epoxy group). In this case, it is preferable that composition B does not contain the thermosetting accelerator. Composition B may or may not contain the thermosetting agent. Furthermore, it is preferable that composition A does not contain the above-mentioned thermosetting compound (particularly a compound having an epoxy group), or that the content of the above-mentioned thermosetting compound (particularly a compound having an epoxy group) is less than that of composition B. This makes it possible to suppress the decrease in pot life due to the reaction of the thermosetting compound during storage of composition B.

[0103] Similarly, a photopolymerization initiator and a photopolymerizable compound may be included in a separate composition. In this case, the multi-component composition is preferably a plurality of compositions comprising composition A containing the above-mentioned photopolymerization initiator and composition B containing the above-mentioned photopolymerizable compound (particularly a compound having a (meth)acryloyl group). In this case, composition B shall not contain the photopolymerization initiator or shall contain less of the photopolymerization initiator than composition A. Furthermore, it is preferable that composition A shall not contain the photopolymerizable compound (particularly a compound having a (meth)acryloyl group) or shall contain less of the photopolymerizable compound (particularly a compound having a (meth)acryloyl group) than composition B.

[0104] These compositions can be prepared by mixing the components described above. Heating may be applied during the mixing process.

[0105] 2. Cured film In this embodiment, a cured film having a glass transition temperature (Tg) of 120°C or higher and a film thickness of 50 μm or higher is formed by the method described above.

[0106] In the method described above, thermosetting compounds can be sufficiently reacted with each other to form a crosslinked structure, thus enabling the formation of a cured film with a high Tg and high heat resistance. The Tg of the cured film is preferably 120°C to 300°C, more preferably 125°C to 250°C, and even more preferably 130°C to 200°C. The Tg of the cured film can be adjusted by the materials of the thermosetting compound and the photopolymerizable compound, and the conditions for forming the pre-cured film.

[0107] Furthermore, the method described above makes it possible to efficiently form thick cured films because cracking and delamination are less likely to occur even when forming a thick cured film. For example, even if the thickness of the cured film is 50 μm or more, a cured film without cracks or delamination can be formed. The thickness of the cured film can be adjusted by the amount of curable composition applied each time, the number of times the application and light irradiation are repeated, etc.

[0108] The cured film formed by the method described above can be used in insulating materials (especially insulating protective films for printed circuit boards), electronic components sealed with the cured film, etc. In particular, since the cured film is less prone to cracking and delamination even when formed to a thick film thickness, it can be suitably used as an insulating film between wiring in thick copper PCBs where a thick cured film is required. The cured film may be used as a planarizing film for the inner layer thick copper circuits of a thick copper PCB, or as an insulating protective film (solder resist) for the outer layer copper wiring.

[0109] For example, wiring boards used in electronic components for power electronics are expected to carry large currents through the wiring. Therefore, thick copper substrates such as 140 μm or more, 210 μm or more, or 300 μm or more are used. The cured film used on such substrates also needs to be thicker than the cured film formed on ordinary copper substrates. The cured film according to this embodiment is particularly suitable for these applications because it is less prone to cracking and delamination even when formed to a thick film.

[0110] The printed circuit board having a cured film according to this embodiment can be used in various electronic devices. Examples of such electronic devices include information devices such as mobile phones, personal computers, and smartphones; household appliances such as refrigerators, washing machines, and microwave ovens; medical devices; and industrial robots.

[0111] The present invention will be described in detail below with reference to examples, but the scope of the present invention is not limited to the examples.

[0112] 1. Preparation of Curable Compositions The following materials were mixed and filtered through a 3 μm membrane filter of ADVANTEC Teflon ("Teflon" is a registered trademark of Zakemars Company) to obtain compositions A1 to A8 and compositions B1 to B8. The viscosity of each of compositions A and B was determined in advance by checking the relationship between temperature and viscosity using a rheometer "MCR302" (manufactured by Anton Paar Corporation), and heating was controlled so that the viscosity of the compositions in the ink tank and inkjet head was in the range of 5 to 100 mPa·s.

[0113] • Epoxy compounds (thermosetting compounds) Bisphenol A type epoxy resin (EP-4300E, manufactured by ADEKA Corporation) • Thermosetting agents Acid anhydride-based thermosetting agents (YH306 (methylbutenyltetrahydrophthalic anhydride), manufactured by Mitsubishi Chemical Corporation) Amine-based thermosetting agents (Fujicure 7002, manufactured by T&K TOKA Corporation) • Thermosetting accelerators Imidazole compounds (2PZ-CN (1-cyanoethyl-2-ethylimidazole), manufactured by Shikoku Chemicals, Inc.) • Compounds having glycidyl groups and (meth)acryloyl groups (photo- / thermosetting compounds) 4-hydroxybutyl acrylate glycidyl ether (4HBAGE, manufactured by Mitsubishi Chemical Corporation) • Compounds having (meth)acryloyl groups (photopolymerizable compounds) A1: Dipropylene glycol diacrylate (M222, manufactured by Miwon) A2: A3: Acryloylmorpholine (manufactured by Kj Chemicals Co., Ltd., ACMO) A4: Isobornyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., IBXA) A5: N-Acryloyloxyethylhexahydrophthalimide (manufactured by Toagosei Co., Ltd., ARONIX M-140) Photopolymerization initiator: Omnirad 819 (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide) manufactured by IGM Resins, Inc. Filler: S1: Silica particles surface-treated with a silane coupling agent prepared by the method described below (manufactured by Admatex Co., Ltd., 5SP-C3) S2: Untreated silica particles (manufactured by Admatex Co., Ltd., AdmafineSO-C2)

[0114] (Method for preparing silica particles S1) 1 g of trimethoxyphenylsilane was added to 200 mL of ethanol and dissolved. 40 g of silica particles (AdmafineSO-C2, manufactured by Admatex Co., Ltd.) were added to the solution while stirring. This mixture was stirred at room temperature for 12 hours. After washing with ethanol, the silica particles were centrifuged and dried to obtain surface-treated silica.

[0115] The compositions of compositions A1 to A8 are shown in Table 1, and the compositions of compositions B1 to B8 are shown in Table 2. The units of the numerical values ​​for the amounts of each material shown in Tables 1 and 2 are in mass percent.

[0116]

[0117]

[0118] 2. Pre-cured film 2-1. As a substrate for fabricating the pre-cured film, a copper foil laminated substrate was prepared by laminating copper foil on both sides of a 1.6 mm thick FR-4 (Flame Retardant Type 4, glass epoxy substrate).

[0119] Using the apparatus whose schematic configuration is shown in Figure 1, one of compositions A1 to A8 and one of compositions B1 to B8 were applied to a substrate. Furthermore, the applied curable compositions were irradiated with light.

[0120] Both inkjet heads 112 and 114 were Konica Minolta KM1024i series (nozzle pitch 360 npi, 1024 nozzles, standard droplet size 30 pL, built-in heater). The composition was supplied from ink tanks (not shown) connected to each inkjet head and applied to the substrate. The flow path including the ink tanks was controlled by back pressure control to ensure that an appropriate meniscus was formed at the nozzles of the inkjet heads. The amount of each composition applied to the substrate was controlled by the voltage applied to each inkjet head, the droplet volume controlled by drop gradation, the resolution (dpi) of the dots formed on the substrate, and the number of scans.

[0121] Light sources 122 and 124 were placed on either side of the carriage 110. Both light sources 122 and 124 used UV-LED irradiators manufactured by Phoseon Technology, which utilize 395 nm UV-LEDs.

[0122] The distance between inkjet head 112 and inkjet head 114 was 4 cm, and the distance between each inkjet head and each light source was 10 cm.

[0123] On the printer stage 100, the carriage 110 and the substrate 200 were moved so that the carriage 110 scanned the substrate 200 in both directions. Then, one of compositions A1 to A8 was ejected from the inkjet head 112, and one of compositions B1 to B8 was ejected from the inkjet head 114. The liquid volume ratio of each composition was composition A:composition B = 1:5 (by mass).

[0124] After ejecting the composition from each inkjet head, it was UV exposed from a following light source with each back-and-forth scan. In this way, a rectangular pattern measuring 1 cm wide x 4 cm long and a linear pattern with a target width of 1.0 mm formed parallel to it in the longitudinal direction were created. Both of these patterns (pre-cured films) were formed so that the longitudinal direction was the scanning direction of the inkjet head. Furthermore, the resolution and number of scans were adjusted so that each pattern had a thickness of 200 ± 10 μm.

[0125] A rectangular pattern was formed in the same manner as before, except that the substrate was changed to a Teflon substrate to allow for pattern removal, in order to measure the elongation at break, tensile strength, and glass dislocation temperature.

[0126] The substrate was changed to a 1.6 mm thick FR-4 (Flame Retrograde Type 4, glass epoxy substrate) substrate on which 200 μm thick copper wiring was patterned in a comb-like pattern with a line / space width (L / S) of 1 mm / 1 mm. A pattern for evaluating the insulating performance was formed in the same manner as before, except that the coating film thickness was adjusted so that it was 215 μm in the space areas and 15 μm on the copper wiring, and each composition was applied accordingly.

[0127] 2-2. Measurement of Pre-cured Film A rectangular pattern (pre-cured film) formed on a Teflon substrate was peeled off the substrate, and the elongation at break and breaking strength were measured using a digital force gauge (DS2, manufactured by Imada Corporation). During measurement, the rectangular pattern was chucked at a position of 0.7 mm from both ends in the longitudinal direction, one end was fixed, and the other end was connected to the digital force gauge, and it was stretched at a speed of 1 mm / s.

[0128] Table 3 shows the compositions used to form pre-cured films 1 to 17, the exposure conditions, and the physical properties of the pre-cured films.

[0129]

[0130] 3. Cured Film 3-1. Preparation of Cured Film Rectangular and linear patterns (pre-cured films) formed on each substrate were heated at 80°C for 1 hour, and then heated at 170°C for 2 hours to form a cured film.

[0131] 3-2. Evaluation and Measurement of Cured Film 3-2-1. Evaluation of Bleeding The line width of the linear pattern of the cured film formed on the copper foil laminate substrate was measured after heat curing and evaluated according to the following criteria: A: Line width 1.0 mm or more and less than 1.1 mm B: Line width 1.1 mm or more and 1.2 mm or less C: Line width 1.3 mm or more

[0132] 3-2-2. Evaluation of film-forming properties The presence or absence of crack formation on the surface of each cured film formed on the copper foil laminate substrate was evaluated.

[0133] 3-2-3. Measurement of Glass Transition Temperature A rectangular pattern (cured film) formed on a Teflon substrate was peeled off the substrate, and the glass transition temperature (Tg) of the cured film was measured using a thermal analyzer (SII TMA / SS7100) manufactured by Hitachi High-Tech Solutions Co., Ltd. under the following measurement conditions. <Measurement Conditions> Starting temperature for heating: 30°C Ending temperature for heating: 250°C Heating rate: 10°C / min Atmosphere: Under nitrogen

[0134] 3-2-4. Evaluation of Peel Strength For each cured film formed on a copper foil laminate substrate, a grid pattern of cuts was made according to the cross-cut method of JIS K5600-5-6:1999. Adhesive tape was applied to the cut areas and peeled off. The peel state of the cured film after peeling was observed, and the ratio of the number of squares remaining after tape removal to the number of squares created by the cuts (adhesion retention rate) was determined. Based on the obtained adhesion retention rate, the peel strength of the cured film obtained from each composition was evaluated according to the following criteria. Note that for cured films in which peeling was observed, there was no peeling at the interface between the copper foil laminate substrate and the cured film, and it is thought that the peeling occurred at the lamination interface of the cured film. A: Adhesion retention rate of 95% or more B: Adhesion retention rate of 90% or more and less than 95% C: Adhesion retention rate less than 90%

[0135] 3-2-5. Evaluation of Insulation Performance (Ion Migration Resistance) Using glass epoxy substrates with each cured film formed on them, a DC 100V voltage was continuously applied to metal wiring in an environment of 85°C and 85% relative humidity, and the time until a short circuit due to ion migration occurred was measured. A: No short circuit after 1000 hours of application B: Short circuit occurred between 500 hours and 1000 hours C: Short circuit occurred in less than 500 hours

[0136] The evaluation and measurement results for each cured film are shown in Table 4.

[0137]

[0138] As is clear from Tables 1 to 4, by forming a pre-cured film with a fracture elongation of 7% to 200%, and then thermally curing it, it was possible to produce a cured film with a thick film thickness and a high Tg while suppressing the occurrence of cracks on the surface.

[0139] This application claims priority to Japanese Patent Application No. 2024-232923, filed on 27 December 2024. All disclosures in the specification, claims, drawings and abstract contained in the above Japanese application are incorporated herein by reference.

[0140] This invention allows for the production of thick cured films by light irradiation and heat curing.

[0141] 100 Printer stage 110 Carriage 112, 114 Inkjet head 122, 124 Light source 200 Substrate

Claims

1. A method for producing a cured film having a glass transition temperature (Tg) of 120°C or higher and a film thickness of 50 μm or higher, comprising the steps of: applying a curable composition containing a compound having a (meth)acryloyl group and an epoxy compound, and irradiating the applied curable composition with light multiple times to form a pre-cured film having a break elongation of 7% or more and 200% or less; and thermal curing the pre-cured film.

2. The method for manufacturing a cured film according to claim 1, wherein the pre-cured film has a tensile strength of 0.5 N or more and 20 N or less.

3. The method for producing a cured film according to claim 1, wherein the curable composition is applied by a non-contact pattern forming method.

4. The method for producing a cured film according to claim 1, wherein the curable composition is provided by providing a composition having a viscosity of 5 mPa·s or more and 100 mPa·s or less at the temperature at the time of application.

5. The method for producing a cured film according to claim 1, wherein the curable composition is provided by providing a plurality of compositions, each comprising composition A containing a thermosetting agent or thermosetting accelerator for reacting the epoxy compound, and composition B containing the epoxy compound.

6. The method for producing a cured film according to claim 1, wherein the curable composition is provided by providing a one-component composition comprising the compound having a (meth)acryloyl group, the epoxy compound, and a thermosetting agent or thermosetting accelerator for reacting the epoxy compound.

7. The method for producing a cured film according to claim 1, wherein the curable composition comprises silica particles surface-treated with a silane coupling agent.

8. The method for manufacturing a cured film according to claim 1, wherein the cured film is an insulating material.

9. A printed circuit board having a cured film manufactured by the manufacturing method described in any one of claims 1 to 8.

10. An electronic device having a printed circuit board as described in claim 9.

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