Method for producing cured product, and cured product

Abstract

The present invention provides: a method for producing a cured product which has excellent appearance and excellent resolution even if formed into a thick film; or a cured product which is obtained using this method for producing a cured product. This method for producing a cured product includes: a lamination step for obtaining a curable resin laminate by laminating curable resin layers using dry films that each have a first film and a curable resin layer; and a curing step for obtaining a cured product by curing the curable resin laminate. The content of a filler in the curable resin layer is 30% by mass or more based on the total solid content. The curable resin layer has a high filler content surface, which is a surface region that has a relatively high filler content, and a low filler content surface, which is a surface region that has a relatively low filler content. In the lamination step, a pair of curable resin layers adjacent to each other are sequentially laminated so that the high filler content surface of one curable resin layer is superposed on the low filler content surface of the other curable resin layer.

Description

Method for producing cured product and cured product

[0001] The present invention relates to a method for producing a cured product and the cured product.

[0002] In recent years, with the trend toward miniaturization and higher performance of electronic devices, insulating materials (solder resists) used on circuit boards are required to have properties such as high elasticity, low thermal expansion, and hiding power in addition to good appearance. A known method for achieving these properties is to thicken the solder resist film.

[0003] For example, a solder resist formed by laminating multiple coating films made of a white curable composition containing titanium oxide has been disclosed (see Patent Document 1). Also, a method has been disclosed in which multiple photosensitive films are exposed to light each time they are laminated, and then developed after lamination to form a thick-film resist (see Patent Document 2).

[0004] JP 2015-5784 A JP 2004-157422 A

[0005] However, while the techniques of Patent Document 1 and Patent Document 2 can suppress the occurrence of holes (pinholes) formed due to the influence of light blocking by foreign matter, the appearance is impaired by unevenness caused by linear defects (coating streaks) formed due to differences in the concentration of the curable resin composition. Furthermore, if the solder resist is made thick, there is a problem that fine patterning becomes difficult and resolution decreases when a curable resin layer such as a coating film or dry film made of a curable resin composition is exposed to light in the process of forming the solder resist.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for producing a cured product that has excellent appearance and excellent resolution even when a thick film is formed, and to provide a cured product obtained by the method for producing a cured product.

[0007] One aspect of the present invention is a method for producing a cured product, the method comprising: a lamination step of laminating a curable resin layer using a dry film having a first film and a curable resin layer to obtain a curable resin laminate; and a curing step of curing the curable resin laminate to obtain a cured product, wherein the curable resin layer has a filler content of 30 mass% or more based on the total solids content, and the curable resin layer has a high-filler content side that is a surface region having a relatively high filler content and a low-filler content side that is a surface region having a relatively low filler content, and the lamination step is a step of sequentially laminating the high-filler content side of one curable resin layer and the low-filler content side of the other curable resin layer for a pair of adjacent curable resin layers.

[0008] In the method for producing a cured product according to the above aspect, the filler is preferably silica.

[0009] In any of the above aspects of the method for producing a cured product, the thickness of the curable resin layer is preferably 25 μm or less.

[0010] In any of the above aspects of the method for producing a cured product, the curing step preferably includes an exposure step of irradiating the entire curable resin laminate with energy rays to simultaneously expose each of the curable resin layers included in the curable resin laminate.

[0011] In any of the above-described aspects of the method for producing a cured product, the laminating step is preferably a step of laminating at least two or more curable resin layers.

[0012] In any of the above aspects of the method for producing a cured product, the thickness of the curable resin laminate is preferably 20 μm or more.

[0013] Another aspect of the present invention is a cured product comprising a plurality of laminated resin-cured layers, each of which has a filler content of 30 mass% or more based on the total solid content, each of which has a high-filler content surface that is a surface region having a relatively high filler content and a low-filler content surface that is a surface region having a relatively low filler content, and for a pair of adjacent resin-cured layers, the high-filler content surface of one of the resin-cured layers and the low-filler content surface of the other of the resin-cured layers are laminated.

[0014] According to the present invention, it is possible to provide a method for producing a cured product that has excellent appearance and excellent resolution even when formed into a thick film, and a cured product obtained by the method for producing a cured product.

[0015] Fig. 1 is a schematic cross-sectional view of a cured product according to this embodiment. Fig. 2 is a schematic cross-sectional view of a dry film according to this embodiment. Figs. 3(a) to 3(c) are process cross-sectional views illustrating a manufacturing process (lamination process) of a curable resin laminate according to this embodiment.

[0016] Hereinafter, embodiments of the present invention will be described in detail. In this specification, the expression "a to b" in the description of a range of values ​​means that the range is from a to b, unless otherwise specified.

[0017] When the compounds described have isomers, all possible isomers can be used in the present invention unless otherwise specified.

[0018] In this specification, "(meth)acrylic" is meant to encompass both "acrylic" and "methacrylic", and "(meth)acrylate" is meant to encompass both "acrylate" and "methacrylate".

[0019] The weight average molecular weight can be measured by a known method, for example, by gel permeation chromatography (GPC) as a polystyrene-equivalent molecular weight.

[0020] In this specification, the term "resin composition" may be used to mean a "curable resin composition," and the term "resin layer" may be used to mean a "curable resin layer."

[0021] In this specification, the term "curable resin laminate" refers to the state of a "cured product" before curing, and the term "curable resin layer" refers to the state of a "resin cured layer" before curing.

[0022] In this specification, the terms "process" and "step" refer to an operation carried out to achieve the purpose of that process or step, regardless of whether the content of that process or step can be clearly distinguished from other processes or steps.

[0023] In this specification, when the upper and lower limits of a numerical range are separately stated, all combinations of each lower limit and each upper limit are considered to be substantially stated within a consistent range.

[0024] 1. Cured Product 1-1. Structure Fig. 1 is a schematic cross-sectional view of a cured product 10 according to this embodiment. As shown in Fig. 1, the cured product 10 according to this embodiment is configured by laminating multiple resin cured layers 11 to 14.

[0025] In this embodiment ( FIG. 1 ), an example in which four resin-cured layers 11 to 14 are laminated is shown, but this embodiment is not limited to this. Any number of resin-cured layers may be laminated as long as there are two or more layers. For example, the number of resin-cured layers is preferably two to seven, more preferably three to six, and even more preferably four. By setting the number of resin-cured layers within the above range, it is possible to form a cured product 10 that has excellent resolution while maintaining high elasticity, a low coefficient of thermal expansion, and hiding power.

[0026] 1-1-1. Resin-cured layer Each of the resin-cured layers 11 to 14 contains a filler. The shade of the fill color in each of the resin-cured layers 11 to 14 in FIG. 1 indicates the distribution of the filler. A darker fill color indicates a relatively higher filler content, and a lighter fill color indicates a relatively lower filler content. The filler distribution changes stepwise in the stacking direction in each of the resin-cured layers 11 to 14. That is, the filler is distributed so as to change stepwise in the stacking direction in each of the resin-cured layers 11 to 14.

[0027] For example, the resin-cured layer 11 has a high-filler content surface 11a, which is a surface region having a relatively high filler content, and a low-filler content surface 11b, which is a surface region having a relatively low filler content. In other words, the filler content in the high-filler content surface 11a is higher than the filler content in the low-filler content surface 11b. It is preferable that the filler content be higher as one approaches the high-filler content surface 11a side and lower as one approaches the low-filler content surface 11b side. In other words, it is preferable that the filler be distributed more as one approaches the high-filler content surface 11a side and less as one approaches the low-filler content surface 11b side.

[0028] Similar to the resin-cured layer 11 described above, each of the resin-cured layers 12 to 14 has a high-filler content surface 12a to 14a and a low-filler content surface 12b to 14b. In other words, the filler content in the high-filler content surfaces 12a to 14a is higher than the filler content in the low-filler content surfaces 12b to 14b. It is preferable that the filler content be higher as one approaches the high-filler content surfaces 12a to 14a and lower as one approaches the low-filler content surfaces 12b to 14b. In other words, it is preferable that the filler be distributed more as one approaches the high-filler content surfaces 12a to 14a and less as one approaches the low-filler content surfaces 12b to 14b.

[0029] In the cured product 10 of this embodiment, a pair of adjacent cured resin layers are stacked such that the high filler content surface of one cured resin layer and the low filler content surface of the other cured resin layer are stacked.

[0030] More specifically, the resin-cured layer 11 and the resin-cured layer 12, which are a pair of adjacent resin-cured layers, are laminated so that the high-filler content surface 11a of the resin-cured layer 11 contacts the low-filler content surface 12b of the resin-cured layer 12. Similarly, the resin-cured layer 12 and the resin-cured layer 13 are laminated so that the high-filler content surface 12a of the resin-cured layer 12 contacts the low-filler content surface 13b of the resin-cured layer 13. The resin-cured layer 13 and the resin-cured layer 14 are laminated so that the high-filler content surface 13a of the resin-cured layer 13 contacts the low-filler content surface 14b of the resin-cured layer 14.

[0031] In the cured product 10 of this embodiment, the resin cured layers 11 to 14 each contain a filler, and therefore the elastic modulus of the cured product 10 can be improved and the thermal expansion coefficient can be reduced more than conventional ones.

[0032] In the cured product 10 of this embodiment, the resin-cured layers 11 to 14 are laminated, and the filler distribution in each layer changes stepwise in the stacking direction, resulting in a uniform filler distribution throughout the cured product 10. This allows the cured product 10 of this embodiment to have improved resolution compared to a single-layer thick film. Furthermore, the difference in thermal expansion coefficient between the cured product 10 and the substrate is further reduced, thereby further reducing warping of the cured product 10 when producing a printed wiring board or the like. Furthermore, even if pinholes occur in each of the resin-cured layers 11 to 12, because multiple layers are laminated, the pinholes that occur in each layer are filled by the other layers, preventing the cured product 10 as a whole from impairing its appearance due to pinholes.

[0033] 1-2. Thickness 1-2-1. Cured Product The thickness of the cured product 10 is preferably 10 μm or more, 15 μm or more, or 20 μm or more, and is preferably 65 μm or less, 60 μm or less, or 55 μm or less.

[0034] When the thickness of the cured product 10 is within the above range, the cured product 10 becomes thicker, and therefore the cured product 10 has higher elasticity. Therefore, when the cured product 10 is formed on a printed circuit board or the like, displacement of the board can be further suppressed. In addition, the concealment of circuits, scratches, etc. can be further improved. The thermal expansion coefficient of the cured product 10 can be further reduced.

[0035] 1-2-2. Resin Cured Layer The thickness of each of the resin cured layers 11 to 14 is preferably 3 μm or more, 5 μm or more, or 8 μm or more, and is preferably 25 μm or less, 20 μm or less, or 15 μm or less.

[0036] When the thicknesses of the cured resin layers 11 to 14 are within the above range, the distribution of the filler becomes more uniform throughout the entire cured product 10, thereby further improving the resolution.

[0037] In this embodiment (FIG. 1), an example is shown in which the resin-cured layers 11 to 14 are formed to have approximately the same thickness, but this embodiment is not limited to this, and the resin-cured layers 11 to 14 may be formed to have different thicknesses. Furthermore, the filler content in each resin-cured layer, the filler content on the high-filler content side, the filler content on the low-filler content side, the presence or absence of a filler concentration gradient (in the thickness direction) in the resin-cured layer, or the degree of such a gradient, may be the same or different among the multiple resin-cured layers.

[0038] 2. Dry Film Fig. 2 is a schematic cross-sectional view of the dry film D1 of this embodiment. As shown in Fig. 2, the dry film D1 has a curable resin layer 21 and a first film P1. In order to prevent dust and the like from adhering to the dry film D1, a peelable second film (not shown) may be further laminated on the surface of the curable resin layer 21 opposite the first film P1. The dry film D1 is used in the manufacturing process of the cured product 10, which will be described later.

[0039] The configuration and manufacturing method of the dry film D1 of this embodiment will be described below with reference to FIG.

[0040] 2-1. Configuration 2-1-1. Curable Resin Layer The curable resin layer 21 is formed by applying a curable resin composition (described later) onto the first film P1 and then evaporating and drying the organic solvent contained in the curable resin composition layer. The curable resin composition contains a filler.

[0041] The shade of the fill color in the curable resin layer 21 in Fig. 2 represents the distribution of the filler. A darker fill color indicates a relatively higher filler content, and a lighter fill color indicates a relatively lower filler content. The filler content varies stepwise in the stacking direction in the curable resin layer 21. That is, the filler is distributed in the curable resin layer 21 so as to vary stepwise in the stacking direction.

[0042] For example, the curable resin layer 21 has a high-filler content surface 21a, which is a surface region with a relatively high filler content, and a low-filler content surface 21b, which is a surface region with a relatively low filler content. In other words, the filler content in the high-filler content surface 21a is higher than the filler content in the low-filler content surface 21b. It is preferable that the filler content be higher toward the high-filler content surface 21a side and lower toward the low-filler content surface 21b side. In other words, it is preferable that the filler be distributed more toward the high-filler content surface 21a side and less toward the low-filler content surface 21b side.

[0043] Typically, the filler contained in a curable resin composition has a higher specific gravity than the other components in the curable resin composition. Therefore, when the curable resin composition is applied to the first film P1 to form a curable resin composition layer, the filler is thought to gradually settle toward the first film P1 due to gravity. The organic solvent contained in the curable resin composition layer is then evaporated and dried to obtain a dry film D1 having the first film P1 and the curable resin layer 21. This results in the formation of the curable resin layer 21 in a state in which the filler distribution in the curable resin layer 21 changes gradually in the direction of gravity (a state in which the filler content is gradually higher on the first film P1 side). As a result, the curable resin layer 21 has a high-filler content surface 21a, which is a surface region with a relatively high filler content, and a low-filler content surface 21b, which is a surface region with a relatively low filler content (see FIG. 2 ).

[0044] The thickness of the curable resin layer 21 can be appropriately set within the range of preferably 3 to 25 μm, more preferably 3 to 20 μm, and even more preferably 3 to 15 μm.

[0045] 2-1-2. First Film The first film P1 of this embodiment serves to support each curable resin layer 21. Any known film can be used as the first film P1 without any particular limitation. For example, films made of thermoplastic resins such as polyester films such as polyethylene terephthalate and polyethylene naphthalate, polyimide films, polyamideimide films, polypropylene films, and polystyrene films can be suitably used. Among these, polyester films are preferred from the viewpoints of heat resistance, mechanical strength, and handleability. A laminate of these films can also be used as the first film.

[0046] From the viewpoint of improving mechanical strength, the thermoplastic resin film as described above is preferably a film stretched in a uniaxial or biaxial direction.

[0047] The thickness of the first film is not particularly limited, and can be, for example, 10 μm to 150 μm.

[0048] 2-1-3. Second Film The second film of this embodiment has the role of protecting the surface of the curable resin layer 21. The second film may be any film as long as the adhesive strength between the curable resin layer 21 and the first film P1 is smaller than the adhesive strength between the curable resin layer 21 and the first film P1 when the second film is peeled off. For example, a polyethylene film, a polytetrafluoroethylene film, a polypropylene film, or surface-treated paper may be used.

[0049] The thickness of the second film is not particularly limited and may be appropriately selected depending on the application within the range of approximately 10 to 150 μm. The surface of the second film that comes into contact with the curable resin layer 21 may be subjected to a release treatment.

[0050] 2-2. Dry Film Manufacturing Method The dry film manufacturing method of this embodiment includes a preparation step of preparing a curable resin composition and a production step of producing a dry film having a first film and a curable resin layer. Each step will be described below.

[0051] 2-2-1. Preparation Step In the preparation step, the various raw materials of the curable resin composition described below are mixed and stirred to prepare the composition.

[0052] 2-2-1-1. Curable Resin Composition The curable resin composition is a resin composition that constitutes the curable resin layer. The curable resin composition contains an alkali-soluble resin, a photopolymerization initiator, a filler, and, as necessary, other components (additives). Each component contained in the curable resin composition will be described below.

[0053] 2-2-1-1-1. Alkali-Soluble Resin The alkali-soluble resin of this embodiment is not particularly limited, and known materials can be used. The alkali-soluble resin of this embodiment may be either a negative-type or a positive-type, with a negative-type being more preferred. Examples of alkali-soluble resins include compounds having two or more phenolic hydroxyl groups, carboxyl group-containing resins, compounds having a phenolic hydroxyl group and a carboxyl group, and compounds having two or more thiol groups.

[0054] Among these, carboxyl group-containing resins or phenolic resins are preferred because of their excellent adhesion to the substrate. Furthermore, carboxyl group-containing resins are more preferred because of their excellent developability. The carboxyl group-containing resin may be a carboxyl group-containing photosensitive resin having an ethylenically unsaturated group, or a carboxyl group-containing resin without an ethylenically unsaturated group.

[0055] Specific examples of the carboxyl group-containing resin include the following compounds (which may be either oligomers or polymers):

[0056] (1) Carboxyl group-containing resins obtained by copolymerizing an unsaturated carboxylic acid such as (meth)acrylic acid with an unsaturated group-containing compound such as styrene, α-methylstyrene, lower alkyl (meth)acrylate, or isobutylene.

[0057] (2) Carboxyl group-containing urethane resins obtained by polyaddition reaction of diisocyanates such as aliphatic diisocyanates, branched aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates with carboxyl group-containing dialcohol compounds such as dimethylolpropionic acid and dimethylolbutanoic acid, and diol compounds such as polycarbonate polyols, polyether polyols, polyester polyols, polyolefin polyols, acrylic polyols, bisphenol A alkylene oxide adduct diols, and compounds having phenolic hydroxyl groups or alcoholic hydroxyl groups.

[0058] (3) A carboxyl-terminated urethane resin obtained by reacting an acid anhydride with the terminal of a urethane resin obtained by a polyaddition reaction of a diisocyanate compound such as an aliphatic diisocyanate, a branched aliphatic diisocyanate, an alicyclic diisocyanate, or an aromatic diisocyanate with a diol compound such as a polycarbonate polyol, a polyether polyol, a polyester polyol, a polyolefin polyol, an acrylic polyol, a bisphenol A alkylene oxide adduct diol, or a compound having a phenolic hydroxyl group or an alcoholic hydroxyl group.

[0059] (4) Carboxyl group-containing urethane resins obtained by polyaddition reaction of diisocyanates with (meth)acrylates of bifunctional epoxy resins such as bisphenol A type epoxy resins, hydrogenated bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bixylenol type epoxy resins, and biphenol type epoxy resins, or their partially acid anhydride-modified products, carboxyl group-containing dialcohol compounds, and diol compounds.

[0060] (5) A carboxyl group-containing urethane resin that is (meth)acrylated at the terminal by adding a compound having one hydroxyl group and one or more (meth)acryloyl groups in the molecule, such as a hydroxyalkyl (meth)acrylate, during the synthesis of the resin (2) or (4).

[0061] (6) A carboxyl group-containing urethane resin that is (meth)acrylated at the terminal by adding a compound having one isocyanate group and one or more (meth)acryloyl groups in the molecule, such as a reaction product of isophorone diisocyanate and pentaerythritol triacrylate, during the synthesis of the resin (2) or (4).

[0062] (7) Carboxyl group-containing resins obtained by reacting a polyfunctional epoxy resin with (meth)acrylic acid and adding a dibasic acid anhydride such as phthalic anhydride, tetrahydrophthalic anhydride, or hexahydrophthalic anhydride to the hydroxyl groups present in the side chains.

[0063] (8) A carboxyl group-containing resin obtained by reacting a polyfunctional epoxy resin in which the hydroxyl groups of a difunctional epoxy resin are further epoxidized with epichlorohydrin with (meth)acrylic acid, and then adding a dibasic acid anhydride to the resulting hydroxyl groups.

[0064] (9) A carboxyl group-containing polyester resin obtained by reacting a polyfunctional oxetane resin with a dicarboxylic acid and adding a dibasic acid anhydride to the resulting primary hydroxyl group.

[0065] (10) A carboxyl group-containing resin obtained by reacting a compound having multiple phenolic hydroxyl groups in one molecule with an alkylene oxide such as ethylene oxide or propylene oxide, reacting the resulting reaction product with an unsaturated group-containing monocarboxylic acid, and then reacting the resulting reaction product with a polybasic acid anhydride.

[0066] (11) A carboxyl group-containing resin obtained by reacting a compound having multiple phenolic hydroxyl groups in one molecule with a cyclic carbonate compound such as ethylene carbonate or propylene carbonate, reacting the resulting reaction product with an unsaturated group-containing monocarboxylic acid, and then reacting the resulting reaction product with a polybasic acid anhydride.

[0067] (12) A carboxyl group-containing resin obtained by reacting an epoxy compound having multiple epoxy groups in one molecule with a compound having at least one alcoholic hydroxyl group and one phenolic hydroxyl group in one molecule, such as p-hydroxyphenethyl alcohol, and an unsaturated group-containing monocarboxylic acid, such as (meth)acrylic acid, and then reacting the alcoholic hydroxyl groups of the resulting reaction product with a polybasic acid anhydride, such as maleic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, or adipic anhydride.

[0068] (13) A carboxyl group-containing resin obtained by further adding a compound having one epoxy group and one or more (meth)acryloyl groups in the molecule, such as glycidyl (meth)acrylate or α-methylglycidyl (meth)acrylate, to the carboxyl group-containing resin described in (1) to (12) above.

[0069] Among the carboxyl group-containing resins, it is preferable to include at least one of the carboxyl group-containing resins (7), (8), (10), (11), and (13), and from the viewpoint of further improving insulation reliability, it is more preferable to include the carboxyl group-containing resin described in (10) or (11).

[0070] The acid value of the alkali-soluble resin is not particularly limited as long as it does not impair the effects of the present invention, and is, for example, 20 to 200 mgKOH / g, preferably 40 to 150 mgKOH / g. When the acid value of the alkali-soluble resin is in this range, development of the curable resin laminate with an aqueous alkali solution after exposure becomes easier, and drawing of a normal cured product pattern becomes easier.

[0071] The weight average molecular weight of the alkali-soluble resin varies depending on the resin skeleton, but can be 1,500 to 150,000, preferably 1,500 to 100,000, more preferably 1,500 to 50,000, and particularly preferably 1,500 to 30,000. When the weight average molecular weight is within this range, the tack-free performance, storage stability, moisture resistance of the curable resin laminate after exposure, and developability are excellent, and film loss during development and degradation of resolution can be further suppressed.

[0072] The alkali-soluble resins can be used alone or in combination.

[0073] 2-2-1-1-2. Photopolymerization Initiator The photopolymerization initiator of this embodiment is not particularly limited, and any photopolymerization initiator known as a photopolymerization initiator or a photoradical generator can be used.

[0074] Examples of the photopolymerization initiator include bisacylphosphine oxides such as bis-(2,6-dichlorobenzoyl)phenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, bis-(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, and bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; Monoacylphosphine oxides such as 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylphosphinic acid methyl ester, 2-methylbenzoyldiphenylphosphine oxide, pivaloylphenylphosphinic acid isopropyl ester, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; hydroxyacetophenones such as 1-hydroxy-cyclohexyl phenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, and 2-hydroxy-2-methyl-1-phenylpropan-1-one; Benzoins such as benzoin, benzil, benzoin methyl ether, benzoin ethyl ether, benzoin n-propyl ether, benzoin isopropyl ether, and benzoin n-butyl ether; benzoin alkyl ethers; benzophenones such as benzophenone, p-methylbenzophenone, Michler's ketone, methylbenzophenone, 4,4'-dichlorobenzophenone, and 4,4'-bisdiethylaminobenzophenone;Acetophenones such as acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone, 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; thioxanthones such as thioxanthone, 2-ethylthioxanthone, 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, and 2,4-diisopropylthioxanthone; Anthraquinones such as anthraquinone, chloroanthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone, 2-amylanthraquinone, and 2-aminoanthraquinone; ketals such as acetophenone dimethyl ketal and benzyl dimethyl ketal; benzoic acid esters such as ethyl-4-dimethylaminobenzoate, 2-(dimethylamino)ethyl benzoate, and p-dimethylbenzoic acid ethyl ester; oxime esters such as 1,2-octanedione, 1-[4-(phenylthio)-2-(O-benzoyloxime)], ethanone, and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime); Titanocenes such as bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro)-3-(1H-pyrrol-1-yl)phenyl)titanium and bis(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(1-pyr-1-yl)ethyl)phenyl]titanium; phenyl disulfide 2-nitrofluorene, butyroin, anisoin ethyl ether, azobisisobutyronitrile, tetramethylthiuram disulfide, etc. These can be used alone or in combination.

[0075] The amount of the photopolymerization initiator is not particularly limited, and is preferably 0.5 to 20% by mass relative to 100% by mass of the alkali-soluble resin. When the amount of the photopolymerization initiator is within this range, a curable resin composition and a cured product having excellent surface curability, less halation, and better resolution can be obtained.

[0076] 2-2-1-1-3. Filler Examples of the filler include inorganic fillers and organic fillers.

[0077] Examples of inorganic fillers that can be used include metal oxides such as silica, alumina, and titanium oxide; metal hydroxides such as aluminum hydroxide and magnesium hydroxide; clay minerals such as talc and mica; fillers having a ferovskite crystal structure such as barium titanate and strontium titanate; boron nitride, aluminum borate, barium sulfate, and calcium carbonate.

[0078] Examples of organic fillers that can be used include fluororesin fillers such as polytetrafluoroethylene (PTFE), tetrafluoroethylene / ethylene copolymer (ETFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), and polyvinyl fluoride (PVF); and hydrocarbon resin fillers such as cycloolefin polymer (COP) and cycloolefin copolymer (COC).

[0079] The filler is preferably an inorganic filler. From the viewpoint of further improving the heat resistance and mechanical properties of the cured product, silica is more preferred. The average particle size of the silica is preferably 0.01 to 5 μm, more preferably 0.01 to 1 μm. Here, the average particle size can be determined as the median diameter (d50, volume basis) based on the cumulative distribution from the particle size distribution measured by the laser diffraction / scattering method using a commercially available laser diffraction / scattering particle size distribution analyzer. The average particle size of the silica refers to the value measured as described above on a powder prior to preparation (pre-stirring, kneading) of the resin composition.

[0080] The silica is preferably blended in a slurry state. By blending in a slurry state, it is easier to highly disperse the silica and suppress aggregation, so that the silica having the average particle size in the above-mentioned specific range is easier to handle. In addition, by blending in a slurry state, it is easier to maintain the precision (in 1 μm units) of the film thickness of the resin layer.

[0081] The filler is preferably a surface-treated filler, which can provide a cured product with higher elasticity and a lower coefficient of thermal expansion without impairing resolution.

[0082] The content of the filler in the curable resin composition is preferably 30% by mass or more, preferably 30 to 90% by mass or more, and more preferably 50 to 90% by mass or less, based on the total solid content. By setting the filler content within the above range, the elastic modulus of the cured product can be further improved and the thermal expansion coefficient of the cured product can be further reduced.

[0083] 2-2-1-1-4. Organic Solvent The organic solvent is not particularly limited, and examples thereof include chloroform, methylene chloride, and toluene. Additionally, solvents such as N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), cyclohexanone, propylene glycol monomethyl ether acetate (PMA), diethylene glycol monoethyl ether acetate (CA), methyl ethyl ketone, ethyl acetate, and anisole may also be used. Only one type of organic solvent may be used, or two or more types may be used.

[0084] 2-2-1-1-5. Other Components / Additives Other components may include photocurable compounds and thermosetting compounds other than the alkali-soluble resins described above. In addition, additives may include colorants, antisettling agents, polymerization inhibitors, ultraviolet absorbers, silane coupling agents, plasticizers, flame retardants, antistatic agents, antioxidants, antioxidants, antibacterial and antifungal agents, antifoaming agents, leveling agents, thickeners, adhesion-imparting agents, thixotropy-imparting agents, photoinitiator assistants, sensitizers, photobase generators, thermoplastic resins, elastomers, organic fillers, release agents, surface treatment agents, dispersants, dispersion assistants, surface modifiers, stabilizers, and phosphors. These may be used alone or in combination.

[0085] In the production process, the curable resin composition prepared in the preparation process is applied onto the first film P1 to form a curable resin composition layer, and then the organic solvent is evaporated and dried to produce a dry film D1 having the first film P1 and the curable resin layer 21.

[0086] The curable resin composition, which has been adjusted to an appropriate viscosity using an organic solvent in the preparation step, is then applied to a uniform thickness on a first film P1 using a comma coater, blade coater, lip coater, rod coater, squeeze coater, reverse coater, transfer roll coater, gravure coater, spray coater, or the like in the production step. The applied curable resin composition forms a curable resin composition layer. The organic solvent contained in the curable resin composition layer is then evaporated and dried, typically at a temperature of 50 to 130°C for 1 to 30 minutes, to convert the curable resin composition layer into a curable resin layer 21. This procedure yields a dry film D1 having the first film P1 and the curable resin layer 21 (see FIG. 2).

[0087] In this embodiment, the manufacturing process for the cured product 10, described below, requires at least the same number of dry films as the number of resin-cured layers 11 to 14 of the cured product 10. For example, the cured product 10 of this embodiment has four layers, namely, the resin-cured layers 11 to 14, stacked together. For this reason, it is preferable to prepare at least four dry films. That is, it is preferable to prepare at least four dry films D1 to D4, such as the dry film D1 (see FIG. 2) having the first film P1 and the curable resin layer 21, the dry film D2 having the first film P2 and the curable resin layer 22, the dry film D3 having the first film P3 and the curable resin layer 23, and the dry film D4 having the first film P4 and the curable resin layer 24. The dry films D2 to D4 have the same configuration and are manufactured using the same method as the dry film D1, and therefore are not illustrated or described here.

[0088] 3. Method for Producing Cured Product The cured product 10 of this embodiment is produced by sequentially laminating curable resin layers on a substrate to form a curable resin laminate, and curing the curable resin laminate. The method for producing the cured product 10 of this embodiment includes: a lamination step of laminating curable resin layers on a substrate using the dry film described above to obtain a curable resin laminate; and a curing step of curing the curable resin laminate to obtain the cured product 10. Each step will be described below.

[0089] 3(a) to 3(c) are cross-sectional views showing the manufacturing process (lamination process) of the curable resin laminate 20 according to this embodiment. In the lamination process, the curable resin layers 21 to 24 are laminated on the substrate Q using the dry films D1 to D4 described above to obtain the curable resin laminate 20. The lamination process includes a bonding step and a lamination step, which will be described later. Each step will be described below with reference to FIG. 3.

[0090] 3A is a cross-sectional view showing a process after the above-described dry film D1 is bonded to the substrate Q. As shown in FIG. 3A, in the bonding step, the dry film D1 is bonded to the substrate Q by lamination so that the curable resin layer 21 and the substrate Q face each other.

[0091] Specifically, first, the second film (not shown) is peeled from the dry film D1, which is made up of a first film P1, a curable resin layer 21, and a second film (not shown) laminated in this order. Then, the dry film D1 is bonded to the substrate Q using a vacuum laminator at a temperature of 80 to 110°C and a pressure of 0.5 MPa, with the curable resin layer 21 facing the substrate Q (see FIG. 3(a)).

[0092] The substrate Q is not particularly limited, and may be a printed wiring board or flexible printed wiring board with a circuit formed in advance using copper or the like, or a copper-clad laminate for high-frequency circuits using materials such as paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth / non-woven cloth epoxy, glass cloth / paper epoxy, synthetic fiber epoxy, fluororesin / polyethylene / polyphenylene ether, polyphenylene oxide / cyanate, or the like. Examples of the copper-clad laminate include all grades (such as FR-4), as well as metal substrates, polyimide films, PET films, polyethylene naphthalate (PEN) films, glass substrates, ceramic substrates, and wafer plates. The substrate Q may be subjected to a known pretreatment, such as chemical polishing. Examples of such pretreatment include etching (e.g., etching with an organic acid; 1 μm etching), discoloration prevention treatment, water washing, and drying. From the viewpoint of adhesion to the cured product, it is preferable to use a substrate Q that has been pretreated, and it is particularly preferable to use a substrate that has been chemically polished.

[0093] 3-1-2. Lamination Step In the lamination step, the first film P1 is peeled off from the dry film D1 that was attached to the substrate Q in the laminating step, and a curable resin layer 22 is laminated on the surface of the curable resin layer 21 opposite the substrate Q using another dry film D2. The curable resin layers 23 and 24 are laminated in the same manner, successively, to obtain a curable resin laminate 20.

[0094] Specifically, the first film P1 is peeled from the dry film D1 having the curable resin layer 21 that was laminated onto the substrate Q in the lamination step (see FIG. 3( a)). Meanwhile, the second film (not shown) is peeled from the dry film D2 in which the first film P2, the curable resin layer 22, and the second film (not shown) are laminated in this order. The dry film D2 having the curable resin layer 22 is laminated using a laminator or the like so that the curable resin layer 21 and the curable resin layer 22 face each other. This operation results in the curable resin layer 22 being laminated on the surface of the curable resin layer 21 opposite the substrate Q (see FIG. 3( b)). The same operation as for the curable resin layer 22 described above is repeated for the curable resin layers 23 and 24, and they are laminated sequentially by lamination to produce the curable resin laminate 20 (see FIG. 3( c)).

[0095] FIG. 3(c) is a schematic cross-sectional view of the curable resin laminate 20 obtained by laminating the curable resin layers 21-24 of this embodiment onto a substrate Q, i.e., the curable resin laminate 20 at the stage when the lamination step is completed. As shown in FIG. 3(c), at the end of the lamination step, the curable resin layer 24 laminated by bonding the dry film D4 is positioned at the position furthest from the substrate Q (outermost layer) of the curable resin laminate 20. In the state of the curable resin laminate 20 after the lamination step is completed, the first film P4 has not been peeled off from the dry film D4 having the curable resin layer 24 laminated on the outermost layer, and the first film P4 is attached to the curable resin laminate 20 (curable resin layer 24). In this state, the exposure step (active energy ray irradiation included in the curing step) described below is performed. The first film P4 is peeled off after the exposure step is completed.

[0096] In the lamination step, lamination is preferably performed under at least the following different conditions, namely, a first lamination condition and a second lamination condition.

[0097] 3-1-2-1. First Lamination Conditions In the first lamination conditions, it is preferable to use a vacuum laminator and perform vacuum lamination under pressure and heat. The pressure conditions are preferably 0.1 to 1.0 MPa, the heating conditions are preferably 40 to 80°C, and the lamination time is preferably 20 to 40 seconds.

[0098] By performing vacuum lamination, when a circuit-formed substrate is used as the base material, even if the circuit substrate surface is uneven, the dry film adheres to the circuit substrate, preventing the inclusion of air bubbles and improving the ability to fill recesses on the substrate surface.

[0099] 3-1-2-2. Second Lamination Conditions In the second lamination conditions, lamination is preferably performed under the following pressure and heat conditions: Pressure conditions are 5 to 10 kgf / cm ２ The heating conditions are preferably 40 to 100° C. and the lamination time is preferably 50 to 70 seconds.

[0100] By setting the heating conditions as described above under each of the first lamination condition and the second lamination condition, the curable resin composition can maintain a higher viscosity, which further suppresses the flow of the filler and resin in each of the curable resin layers 21 to 24, allowing the curable resin laminate 20 to be formed on the substrate Q while maintaining the filler distribution and layer structure.

[0101] As described above, in this embodiment, the curable resin layers 21 to 24 are stacked by laminating the dry films D1 to D4, which makes it easier to maintain the layer structure. Furthermore, because the flow of filler within the curable resin layers is relatively suppressed, the filler can be cured in a state where its distribution changes stepwise in the stacking direction. This results in a more uniform distribution of filler throughout the cured product 10, further improving resolution.

[0102] In contrast, conventional methods such as screen printing, in which a coating film is applied multiple times, tend to cause excessive drying and make it difficult to maintain the layer structure. Furthermore, even if a filler is added, the filler tends to settle in the layer, resulting in excessive unevenness in the distribution of the filler, making it impossible to achieve a uniform distribution of the filler throughout the cured product.

[0103] In the curing step, the curable resin laminate 20 produced in the lamination step is cured to obtain a cured product 10. The curing step includes an exposure step, a development step, and a finishing step, which will be described later. Each step will be described below.

[0104] 3-2-1. Exposure Step In the exposure step, the curable resin laminate 20 produced in the lamination step is irradiated (exposed) with active energy rays.

[0105] Specifically, after producing the curable resin laminate 20 in the lamination step, the entire curable resin laminate 20 is selectively irradiated (exposed) with active energy rays through a photomask having a predetermined pattern formed thereon. At this time, it is preferable to simultaneously expose each of the curable resin layers 21 to 24 included in the curable resin laminate 20 (collective exposure). After exposure, it is preferable to leave the curable resin laminate 20 at room temperature for 10 to 180 minutes. Thereafter, the first film P4 attached to the curable resin layer 24, which is the outermost layer of the curable resin laminate 20, is peeled off.

[0106] By one-shot exposure, the entire curable resin laminate 20 is exposed, and each of the curable resin layers 21 to 24 included in the curable resin laminate 20 is simultaneously exposed, whereby a pattern can be formed in a shorter time than when exposure is performed for each layer. Furthermore, finer patterning is possible compared to when exposure is performed each time each of the curable resin layers 21 to 24 is laminated.

[0107] The exposure device used for actinic energy ray irradiation may be a device equipped with a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a mercury short arc lamp, or the like, and capable of irradiating actinic energy rays in the range of 350 to 450 nm. Furthermore, a direct imaging device (for example, a laser direct imaging device that draws an image directly with a laser based on CAD data from a computer) may also be used. The lamp light source or laser light source of the direct imaging device may have a maximum wavelength in the range of 350 to 450 nm. The exposure dose for image formation varies depending on factors such as the film thickness, but is generally 10 to 1,000 mJ / cm. ２ , preferably 20 to 800 mJ / cm ２ The range may be:

[0108] 3-2-2. Development Step In the development step, the unexposed areas are developed with an alkaline aqueous solution.

[0109] Specifically, the unexposed portion of the curable resin laminate 20 from which the first film P4 has been peeled in the above-described exposure step is developed (for example, for 60 to 90 seconds) with a dilute alkaline aqueous solution (for example, a 0.3 to 3 mass % aqueous sodium carbonate solution or potassium carbonate solution) to form a pattern on the curable resin laminate 20. After the pattern formation, the curable resin laminate 20 may be washed with a cleaning liquid.

[0110] The development treatment with an alkaline aqueous solution can be carried out by a dipping method, a shower method, a spray method, a brush method, etc., and the developer can be an aqueous alkaline solution of potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, ammonia, amines, etc. These may be used in combination.

[0111] In the finishing step, the curable resin laminate 20 on which the pattern has been formed in the developing step described above is irradiated with active energy rays, and then heated and cured (for example, at 100 to 220° C.). In the finishing step, the curable resin laminate 20 is completely cured, thereby forming a cured product 10.

[0112] The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to the following.

[0113] (Synthesis of alkali-soluble resin solution) 119.4 parts by mass of novolac cresol resin (Showa Denko K.K., SHONOL CRG951, OH equivalent: 119.4), 1.19 parts by mass of potassium hydroxide, and 119.4 parts of toluene were introduced into an autoclave equipped with a thermometer, a nitrogen introducing device / alkylene oxide introducing device, and a stirrer, and the system was purged with nitrogen while stirring, and heated to an elevated temperature. Next, 63.8 parts of propylene oxide were gradually added dropwise, and the temperature was raised to 125 to 132°C and 0 to 4.8 kg / cm. ２The mixture was reacted at 100°C for 16 hours. The mixture was then cooled to room temperature, and 1.56 parts of 89% phosphoric acid was added to the reaction solution to neutralize the potassium hydroxide, yielding a propylene oxide reaction solution of novolac cresol resin with a nonvolatile content of 62.1% and a hydroxyl value of 182.2 mgKOH / g (307.9 g / eq.). This solution contained an average of 1.08 moles of propylene oxide added per equivalent of phenolic hydroxyl group. 293.0 parts of the resulting propylene oxide reaction solution of novolac cresol resin, 43.2 parts of acrylic acid, 11.53 parts of methanesulfonic acid, 0.18 parts of methylhydroquinone, and 252.9 parts of toluene. A reactor equipped with a stirrer, thermometer, and air inlet tube was charged with air at a rate of 10 ml / min and the mixture was reacted at 110°C for 12 hours while stirring. The water produced by the reaction was distilled as an azeotrope with toluene, and 12.6 parts of water were distilled off. The mixture was then cooled to room temperature, neutralized with 35.35 parts of a 15% aqueous sodium hydroxide solution, and then washed with water. The toluene was then removed by distillation using an evaporator, while being replaced with 118.1 parts of diethylene glycol monoethyl ether acetate, to obtain a novolac acrylate resin solution. Next, 332.5 parts of the resulting novolac acrylate resin solution and 1.22 parts of triphenylphosphine were introduced into a reactor equipped with a stirrer, thermometer, and air inlet tube. Air was blown in at a rate of 10 ml / min. While stirring, 60.8 parts of tetrahydrophthalic anhydride was gradually added. The mixture was allowed to react at 95 to 101°C for 6 hours, cooled, and then discharged. In this way, a carboxyl group-containing alkali-soluble resin solution with a nonvolatile content of 65% and an acid value of 87.7 mgKOH / g of solids was obtained.

[0114] (Preparation of Surface-Treated Filler (Methacrylic Silane-Treated Silica)) 70 g of spherical silica (SFP-30M manufactured by Denka Co., Ltd.), 28 g of PMA (propylene glycol monomethyl ether acetate) as a solvent, and 2 g of KBM-503 manufactured by Shin-Etsu Chemical Co., Ltd. as a silane coupling agent were uniformly dispersed to obtain a silica solvent dispersion.

[0115] <Preparation of Curable Resin Composition> The components were blended according to the blending ratios shown in Blending Examples A to C in Table 1 below, and premixed in a stirrer. Then, the components were dispersed and kneaded in a bead mill to prepare the curable resin compositions of Blending Examples A to C.

[0116]

[0117] The blending amounts in Table 1 are in parts by mass. Details of each component in Table 1 are as follows. *1: Alkali-soluble resin solution having an ethylenically unsaturated group synthesized above *2: Irgacure TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide) manufactured by BASF Japan *3: JMT784 (titanocene photopolymerization initiator) manufactured by Yueyang Jinmaotai Technology Co., Ltd. *4: Epicron N-730A (phenol novolac epoxy resin) manufactured by DIC Corporation *5: Epicron N-870 (bisphenol A novolac epoxy resin) manufactured by DIC Corporation *6: Solvent dispersion of silica surface-treated with methacrylsilane, prepared above *7: Benton 38 manufactured by Toshin Kasei Co., Ltd. *8: CAP-504-0.2DPM30 manufactured by Eastman Corporation *9: Melamine manufactured by Nissan Chemical Industries, Ltd. *10: Kayacure DETX-S (2,4-diethylthioxanthone) manufactured by Nippon Kayaku Co., Ltd. *11: Blue pigment and yellow pigment

[0118] Examples 1 to 9, Comparative Examples 1 to 7 <Preparation of Evaluation Substrates> Evaluation substrates for the examples and comparative examples were prepared according to the following procedure so as to have the layer structures and thicknesses of each layer shown in Tables 2 and 3.

[0119] The above curable resin composition was applied to a polyethylene terephthalate film (hereinafter also referred to as PET film) (E5041, manufactured by Toyobo Co., Ltd.) (first film) measuring 300 mm x 130 mm and 25 μm thick so that the film thickness after drying was the thickness shown in Table 2, and the film was dried by heating to form a first curable resin layer. Next, a polypropylene film (MA411, manufactured by Oji F-Tex Co., Ltd.) (second film) measuring 300 mm x 100 mm and 15 μm thick was laminated onto the curable resin layer to form a dry film. The same procedure was repeated to prepare dry films having each curable resin layer from the second layer onwards, for the number of films to be laminated.

[0120] As the substrate, a double-sided printed wiring board measuring 150 mm x 95 mm and having a thickness of 0.4 mm was used, and a chemical polishing treatment equivalent to 1.0 μm was performed using a MEC Etch Bond CZ-8100 manufactured by MEC Corporation. A dry film having a first curable resin layer was cut out to 150 mm x 90 mm, and the polypropylene film (second film) was peeled off. Then, using a two-chamber vacuum laminator CVP-600 (manufactured by Nikko Materials Co., Ltd.), the dry film described above was bonded to the substrate after the pretreatment under the following conditions, with the curable resin layer facing the substrate. Lamination temperature: 80 ° C. Vacuuming: 30 seconds, 3 hPa Lamination: 30 seconds, 0.5 MPa

[0121] The first film was peeled off from the first dry film laminated on the substrate, and a dry film having a second curable resin layer was cut into 150 mm x 90 mm pieces on the exposed curable resin layer. After peeling off the second film, the second curable resin layer was laminated so that the second curable resin layer faced the first curable resin layer. Similarly, the third and subsequent curable resin layers were sequentially laminated to produce a curable resin laminate on the substrate. The outermost PET film of the produced curable resin laminate was not peeled off, and the PET film was left attached (curable resin laminate with PET film). The lamination when laminating the second and subsequent curable resin layers was performed under the following two different conditions.

[0122] (First lamination conditions) Lamination temperature: 80°C Vacuuming: 30 seconds, 3 hPa Lamination: 30 seconds, 0.5 MPa

[0123] (Second lamination conditions) Lamination temperature: 100°C Press: 60 seconds, 8 kgf / cm ２

[0124] The curable resin laminate with the PET film obtained on the substrate was subjected to one-shot exposure (exposure amount: 300 mJ / cm) using a DI exposure device (Mms60, manufactured by Oak Manufacturing Co., Ltd.) through a photomask with an opening pattern of 80 μm and 100 μm. ２After that, the PET film was peeled off, and the 1% by mass Na ２ CO ３ Development was carried out using an aqueous solution at 30°C and a spray pressure of 0.2 MPa for 90 seconds to form a curable resin laminate having an opening pattern of 80 μm and 100 μm in diameter. The curable resin laminate was washed with a cleaning solution at 25°C and a spray pressure of 0.1 MPa for 90 seconds, and after exposure (exposure amount: 1000 mJ / cm ２ ), and heated at 170°C for 60 minutes to completely cure. Evaluation substrates were fabricated with a cured product formed on a substrate. The properties of the obtained evaluation substrates were evaluated as follows. The results are shown in Tables 2 and 3.

[0125] <Appearance Evaluation> The evaluation substrates of each example and comparative example were visually inspected for pinholes and unevenness. Evaluation of each item was performed according to the following criteria.

[0126] (Pinholes) 〇: No pinholes ×: Pinholes present

[0127] (Unevenness) 〇: No coating streaks ×: Coating streaks present

[0128] <Preparation of Samples for Concealment Evaluation> Samples for concealment evaluation of each Example and Comparative Example were prepared by the same procedure as in the above <Preparation of Evaluation Substrate>, except that the substrate used was a double-sided printed wiring board measuring 150 mm x 95 mm and having a thickness of 0.4 mm, on the circuit surface of which a scratch of 5 μm in depth and 10 mm in length was made using a cutter knife. The concealment evaluation samples of each Example and Comparative Example were visually observed for concealment and evaluated according to the following criteria.

[0129] (Concealing power) ◎: No scratches 〇: Slight scratches ×: Scratches

[0130] (Measurement of coefficient of linear thermal expansion (CTE)) The cured product was peeled from the evaluation substrate of each example and comparative example, and cut out to obtain a measurement size (3 mm x 10 mm) to serve as a measurement sample. The CTE of each measurement sample was measured using a TMA6100 manufactured by Hitachi High-Tech Corporation. The measurement conditions were a test load of 5 g, a temperature rise rate of 10°C / min, and a measurement in tension mode, with the sample heated from room temperature and repeated twice, and the average coefficient of linear thermal expansion (α2) calculated in the range of 200°C to 250°C in the second measurement was obtained.

[0131] (Resolution) In the evaluation substrates of each example and comparative example, the diameter of the opening end (Top) at φ80 μm and φ100 μm was measured at a measurement magnification of 1,000 times using an SEM (JSM6610LV, manufactured by JEOL Ltd.), and the rate of change T relative to the design value was calculated using the following formula: Rate of change T at φ80 μm=100−diameter / 80×100 Rate of change T at φ100 μm=100−diameter / 100×100

[0132] In the evaluation substrates of each example and comparative example, the diameter of the opening bottom (Bottom) at φ80 μm and φ100 μm was measured at a measurement magnification of 1,000 times using an SEM (JSM6610LV, manufactured by JEOL Ltd.), and the rate of change B relative to the design value was calculated using the following formula: Rate of change B at φ80 μm=100−diameter / 80×100 Rate of change B at φ100 μm=100−diameter / 100×100

[0133]

[0134]

[0135] Comparative Examples 1 and 2 were thin and therefore excellent in resolution, but pinholes occurred. Comparative Examples 3 to 7, which were thicker than Comparative Examples 1 and 2, suppressed the occurrence of pinholes, but unevenness occurred and the resolution decreased.

[0136] On the other hand, according to Example 1, although the thickness was similar to that of Comparative Example 2, not only was the resolution excellent, but the occurrence of pinholes was also suppressed. Furthermore, the results for the linear thermal expansion coefficient were also satisfactory, and it was found that a low thermal expansion coefficient could be achieved. Furthermore, in Examples 2-9, which were thicker than Example 1, the occurrence of unevenness was suppressed and the resolution excellent. Furthermore, although the thickness was similar to that of Comparative Examples 3-7, the linear thermal expansion coefficient was reduced, allowing for a further reduction in the thermal expansion coefficient. From the above, it was demonstrated that the manufacturing methods according to each Example can easily suppress the occurrence of pinholes and unevenness, and can obtain cured products that tend to have excellent resolution even when the film is thickened.

[0137] The present invention provides a method for producing a cured product that has excellent appearance and excellent resolution even when made thick, and the cured product can be used in miniaturized, high-performance electronic devices, etc. CROSS-REFERENCE TO RELATED APPLICATIONS

[0138] This application claims priority based on Japanese Patent Application No. 2023-187255, filed with the Japan Patent Office on October 31, 2023, the entire disclosure of which is incorporated herein by reference in its entirety.

[0139] 10 Cured product 20 Curable resin laminate P1 First film P4 First film D1 Dry film D4 Dry film Q Substrate

Claims

1. A method for producing a cured product, comprising: a lamination step of laminating the curable resin layer using a dry film having a first film and a curable resin layer to obtain a curable resin laminate; and a curing step of curing the curable resin laminate to obtain a cured product, wherein the filler content in the curable resin layer is 30 mass% or more based on the total solids content, and the curable resin layer has a high filler content side which is a surface region having a relatively high filler content, and a low filler content side which is a surface region having a relatively low filler content, and the lamination step is a step of sequentially laminating the high filler content side of one curable resin layer and the low filler content side of the other curable resin layer for a pair of adjacent curable resin layers.

2. The method for producing a cured product according to claim 1, wherein the filler is silica.

3. The method for producing a cured product according to claim 1 or 2, wherein the thickness of the curable resin layer is 25 μm or less.

4. A method for producing a cured product according to claim 1 or 2, wherein the curing process includes an exposure step of irradiating the entire curable resin laminate with energy rays, thereby simultaneously exposing each of the curable resin layers contained in the curable resin laminate.

5. The method for producing a cured product according to claim 1 or 2, wherein the lamination step is a step of laminating at least two or more curable resin layers.

6. The method for producing a cured product according to claim 1 or 2, wherein the thickness of the curable resin laminate is 20 μm or more.

7. A cured product having a plurality of laminated resin cured layers, each of which has a filler content of 30 mass% or more based on the total solid content, each of which has a high filler content surface that is a surface region having a relatively high filler content and a low filler content surface that is a surface region having a relatively low filler content, and for each of a pair of adjacent resin cured layers, the high filler content surface of one of the resin cured layers and the low filler content surface of the other of the resin cured layers are laminated together.

Images