Curable composition for circuit protection, cured product thereof, and control component

Abstract

To provide a curable composition for circuit protection that can be cured not only in an irradiated portion irradiated with active energy rays but also in a non-irradiated portion by an anaerobic state, that can provide a cured product having relatively good electrical insulation properties in both the irradiated portion and the non-irradiated portion, and that can be cured in a relatively short time in the non-irradiated portion.SOLUTION: The invention provides, e.g., a curable composition for circuit protection including a polymerizable compound having a plurality of (meth)acryloyl groups in a molecule, a (meth)acrylic acid alkyl ester monomer, an acyl group-containing compound having a specific molecular structure, and an organic peroxide.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a curable composition for circuit protection, a cured product thereof, and a control component. [Background technology]

[0002] BACKGROUND ART Curable compositions that are cured by irradiation with active energy rays such as ultraviolet rays have been known. Among these curable compositions, there are known curable compositions that are cured even under anaerobic conditions. As described above, as a curable composition that can be cured by irradiation with active energy rays and also in an anaerobic condition, for example, a curable composition containing a compound having a (meth)acryloyl group, saccharin, an organic peroxide, and a photopolymerization initiator is known (for example, Patent Document 1). Furthermore, as the curable composition, a curable composition containing a polymerizable acrylate ester, 1-(2-carboxyacryloyl)-2-phenylhydrazine, an organic peroxide, and a photopolymerization initiator is known (for example, Patent Document 2).

[0003] The curable compositions described in Patent Documents 1 and 2 are used to provide cured products for use as adhesives, for example. When active energy rays are irradiated onto a coating film or the like of the curable compositions described in Patent Documents 1 and 2, the irradiated, exposed portions are cured by a radical polymerization reaction, and further, the unexposed portions that cannot be irradiated with active energy rays are put into an anaerobic state and cured. In other words, the curable compositions described in Patent Documents 1 and 2 can be cured in all portions, regardless of whether they are irradiated or unirradiated, by irradiation with active energy rays. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 06-013692 [Patent Document 2] Patent No. 3087374 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, it is conceivable that the curable compositions described in Patent Documents 1 and 2 may be used for purposes other than adhesives, for example. If the curable composition described in Patent Document 1 is used as a circuit protection material, the cured product is required to have good electrical insulation properties after curing.

[0006] However, conventional curable compositions such as those described in Patent Documents 1 and 2 have a problem in that they do not necessarily exhibit good electrical insulation properties. In response to this, a curable composition has been proposed in which an isocyanate compound is further added to the curable composition. Such a curable composition is also referred to as a moisture-curable photocurable composition because the non-irradiated portions are cured by moisture. However, in the non-irradiated portions, the (meth)acryloyl group-containing compound that should undergo polymerization upon irradiation with active energy rays remains unreacted, leaving the curable composition in a semi-cured state, and the cured product does not necessarily have sufficient electrical insulation. Furthermore, it takes a relatively long time for the curable composition to cure in the non-irradiated portions.

[0007] Therefore, there is a demand for a curable composition for protecting circuits that can give a cured product with relatively good electrical insulation properties in both the cured and non-irradiated areas after irradiation, and that can cure in a relatively short time in the non-irradiated areas.

[0008] In view of the above problems and demands, an object of the present invention is to provide a curable composition for protecting circuits that can be cured under anaerobic conditions not only in an irradiated portion irradiated with active energy rays but also in a non-irradiated portion, capable of giving a cured product with relatively good electrical insulation properties in both the irradiated and non-irradiated portions, and that can be cured in a relatively short time in the non-irradiated portion. Another object of the present invention is to provide a cured product of the above curable composition for circuit protection. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the curable composition for circuit protection according to the present invention comprises a polymerizable compound having a plurality of (meth)acryloyl groups in the molecule, a (meth)acrylic acid alkyl ester monomer, an acyl group-containing compound having a molecular structure represented by the following formula (1) or (2), and an organic peroxide: [ka]

[0010] The cured product according to the present invention is a cured product of the above-mentioned curable composition for circuit protection, and is adhered to an object to be protected. The control part according to the present invention comprises a cured product of the above-described curable composition for circuit protection, and a component of an electric or electronic circuit, at least a portion of the surface of which is covered with the cured product. [Effects of the Invention]

[0011] The curable composition of the present invention can be cured not only by irradiation with active energy rays but also under anaerobic conditions, and can be cured in a relatively short time in non-irradiated areas. Moreover, the cured product of the curable composition can have relatively good electrical insulation properties in both the cured areas after irradiation and the cured areas after anaerobic conditions. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing an example of a urethane (meth)acrylate oligomer contained in the curable composition. [Figure 2A] FIG. 2A is a schematic diagram showing an example of a site where a curing reaction by ultraviolet light and a curing reaction under anaerobic conditions proceeds after a curable composition is applied to the surface of an IC package. [Figure 2B] FIG. 2B is a schematic diagram showing an example of a site where a curing reaction due to ultraviolet light and a curing reaction under anaerobic conditions progress after the curable composition is applied to the surface of a chip component. [Figure 2C] FIG. 2C is a schematic diagram showing an example in which a curing reaction proceeds under anaerobic conditions at a site where the curable composition has entered a component back-side through-hole. [Figure 2D] FIG. 2D is a schematic diagram showing an example of a region where a curable composition penetrates between a BGA and an electric circuit board on which the BGA is mounted, and where a curing reaction due to ultraviolet light and a curing reaction under anaerobic conditions proceeds. [Figure 3] FIG. 3 is a schematic diagram showing a method for an insulation resistance evaluation test. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, one embodiment of the curable composition for circuit protection according to the present invention will be described. The curable composition for circuit protection according to this embodiment (hereinafter also simply referred to as the curable composition) is mainly used to coat (cover) components of electronic or electric circuits or connections between components. Thereafter, for example, the curable composition is cured and used to cover the components with a cured film. That is, the curable composition according to this embodiment is, for example, a curable composition for protecting electronic or electric circuits.

[0014] The curable composition of this embodiment contains a polymerizable compound having multiple (meth)acryloyl groups in the molecule, a (meth)acrylic acid alkyl ester monomer, an acyl group-containing compound having a specific molecular structure (described in detail later), and an organic peroxide. The curable composition of this embodiment preferably further contains a photopolymerization initiator or an amine compound. The curable composition of this embodiment is a photocurable composition and also an anaerobic curable composition.

[0015] The curable composition of the present embodiment can be cured not only by irradiation with active energy rays but also under anaerobic conditions, and the cured product of the curable composition can have good electrical insulation properties both in the cured portion cured by the irradiation and in the non-irradiated portion cured under anaerobic conditions. This allows, for example, the backside of a component on a mounting board that cannot be irradiated with active energy rays, or portions such as through-holes that are structurally in an anaerobic state, to have sufficient electrical insulation. Furthermore, even in a portion that is not irradiated with active energy rays and is not structurally anaerobic, sufficient electrical insulation can be exhibited by exposing it to an anaerobic condition. The anaerobic condition can be achieved, for example, by using an oxygen scavenger during packaging, replacing the surrounding environment with nitrogen gas, or reducing the oxygen gas concentration in the surrounding environment by vacuum treatment.

[0016] <Polymerizable compound having multiple (meth)acryloyl groups in the molecule> The polymerizable compound contained in the curable composition of this embodiment is, for example, a urethane (meth)acrylate polymer or urethane (meth)acrylate oligomer having a plurality of (meth)acryloyl groups and urethane bonds in the molecule. The polymerizable compound may be synthesized using raw material monomers. Alternatively, a commercially available product may be used as the polymerizable compound. In this specification, the term "(meth)acrylate" encompasses both "acrylate" and "methacrylate." The same applies to the terms "(meth)acrylic" and "(meth)acryloyl group."

[0017] The urethane (meth)acrylate polymer or urethane (meth)acrylate oligomer is, for example, a urethane reaction product of a difunctional or higher isocyanate compound, a polyol compound, and a hydroxy group-containing (meth)acrylate. The isocyanate compound is preferably a difunctional isocyanate compound.

[0018] (Isocyanate compounds) The isocyanate compound for obtaining the urethane reaction product is not particularly limited as long as it is a compound having two or more isocyanate groups (-NCO) in the molecule (bifunctional or higher).

[0019] Examples of the isocyanate compound include aromatic polyisocyanate compounds, alicyclic polyisocyanate compounds, and aliphatic polyisocyanate compounds. These isocyanate compounds may have two, three, or four isocyanate groups in the molecule. It is preferable that the isocyanate compound has a molecular structure in which the isocyanate group is not directly bonded to the aromatic ring, in order to improve the weather resistance of the cured product after curing. These isocyanate compounds may be used alone or in combination of two or more.

[0020] Examples of the isocyanate compound include bifunctional isocyanates such as aromatic isocyanate compounds such as toluene-2,4-diisocyanate, 1,3-bis(isocyanatomethyl)benzene, and bis(4-isocyanatophenyl)methane, and alicyclic isocyanate compounds such as isophorone diisocyanate and 1,3-bis(isocyanatomethyl)cyclohexane. Furthermore, examples of the isocyanate compound include trifunctional or tetrafunctional isocyanate compounds such as isocyanurates, adducts, and biurets of aliphatic diisocyanates having a total of 6 to 10 carbon atoms. Bifunctional isocyanates such as isophorone diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, and 1,3-bis(isocyanatemethyl)benzene, or isocyanurates, adducts, and biuret forms of aliphatic diisocyanates having a total of 6 to 10 carbon atoms are preferred because they are less susceptible to oxidation and have good weather resistance due to a structure in which the isocyanate group is not directly bonded to the aromatic ring, and because they have few crosslinking points and have good flexibility.

[0021] (Polyol compound) The polyol compound for obtaining the urethanization reaction product may be an aliphatic polyether polyol (having a repeating structure of a linear or branched hydrocarbon and an ether in the molecule), a polyolefin polyol, or an aliphatic polycarbonate polyol (having a main chain composed of multiple carbonate ester groups (-O-CO-O-) in the molecule and no aromatic structure between the carbonate ester groups). The polyol compound may be, for example, a diol compound.

[0022] The polyolefin portion of the polyolefin polyol (diol) may have, for example, an unsaturated double bond. More specifically, the polyolefin portion of the polyolefin polyol may have an unsaturated double bond and a hydrogen atom bonded to the α-position carbon atom of the unsaturated double bond. When the polyolefin portion has the above molecular structure, the hydrogen atom bonded to the α-position carbon atom relative to the unsaturated double bond reacts with an organic peroxide. Therefore, when the polymerizable compound is placed in an anaerobic state, oxygen (O2) is consumed. This improves the anaerobic curability of the curable composition, and the cured product of the curable composition may have better electrical insulation properties. The polyolefin polyol having an unsaturated double bond in the polyolefin moiety may have the unsaturated double bond in the main chain or in the side chain. When the unsaturated double bond is at the end of the side chain, the α-carbon is the carbon next to the carbon closest to the main chain among the two carbons forming the unsaturated double bond in the side chain. On the other hand, when the unsaturated double bond is in the middle of the side chain or in the main chain, the α-carbon refers to the two carbons next to each of the two carbons forming the unsaturated double bond.

[0023] Examples of aliphatic polyether diols include polyethylene glycol, polypropylene glycol, and polybutylene glycol (polytetramethylene glycol). Polypropylene glycol or polytetramethylene glycol, which have a larger carbon number (the number of carbon atoms relative to oxygen atoms in the hydrocarbon-ether repeating unit), is preferred because they can exhibit better electrical insulation properties. Examples of polyolefin diols include branched polyolefin diols such as unhydrogenated 1,2-polybutadiene diol or hydrogenated 1,2-polybutadiene diol, and linear polyolefin diols such as unhydrogenated 1,4-polybutadiene diol or hydrogenated 1,4-polybutadiene diol.

[0024] Examples of the aliphatic polycarbonate diol include aliphatic polycarbonate diols in which the hydrocarbon moiety in which carbon atoms are bonded successively is a straight-chain hydrocarbon. The aliphatic portion (hydrocarbon portion in which carbon atoms are bonded successively) in the aliphatic polycarbonate diol may have 4 or more and 12 or less carbon atoms.

[0025] As the polyol compound (for example, a diol compound) for obtaining the above urethane reaction product, a commercially available product can be used.

[0026] (Hydroxy group-containing (meth)acrylate) The hydroxyl group-containing (meth)acrylate used to obtain the urethane reaction product has one hydroxyl group and one (meth)acryloyl group in the molecule. Specifically, the hydroxyl group-containing (meth)acrylate is an alkyl ester compound of (meth)acrylic acid, a hydroxyalkyl (meth)acrylate in which one hydroxyl group is bonded to any carbon atom in the alkyl moiety. The number of carbon atoms in the alkyl moiety is preferably 1 to 4. The (meth)acryloyl group of the hydroxyl group-containing (meth)acrylate can initiate a polymerization reaction when irradiated with active energy rays. Furthermore, the (meth)acryloyl group of the hydroxyl group-containing (meth)acrylate can initiate a polymerization reaction when placed in an anaerobic environment in the presence of an organic peroxide and an amine compound.

[0027] Examples of hydroxy group-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc. The hydroxy group-containing (meth)acrylate is preferably 2-hydroxyethyl (meth)acrylate because of its better polymerizability upon irradiation with active energy rays.

[0028] An example of the urethane reaction product is represented by the general formula in Figure 1. The urethane reaction product generally has a molecular weight on the order of an oligomer. The polymerizable compound may include, for example, a urethane reaction product of a difunctional alicyclic isocyanate compound, a diol compound such as an aliphatic polyether diol or a branched polyolefin diol, and a hydroxyalkyl (meth)acrylate.

[0029] The curable composition for circuit protection of the present embodiment may contain unreacted components that have not undergone the urethanization reaction. The curable composition for circuit protection of the present embodiment may also contain a urethanization reaction catalyst blended in to promote the urethanization reaction. As described above, the curable composition for circuit protection of this embodiment contains various reaction products and unreacted components. Therefore, it is generally impractical to identify the molecular structure of all of the compounds contained therein. In other words, it is generally impractical to directly identify the structure or properties of all of the compounds contained in the curable composition for circuit protection of this embodiment. However, since the molecular structure of the compound before the urethanization reaction is identified and the product of the urethanization reaction can be adequately predicted by adjusting the blending ratio of each raw material before the reaction, it is quite possible to predict the molecular structure of the urethanization reaction product.

[0030] <(Meth)acrylic acid alkyl ester monomer> The (meth)acrylic acid alkyl ester monomer contained in the curable composition of this embodiment is an alkyl ester compound of (meth)acrylic acid. Examples of the (meth)acrylic acid alkyl ester monomer include monofunctional (meth)acrylic acid alkyl ester monomers having one (meth)acryloyl group in the molecule. The (meth)acrylic acid alkyl ester monomer is a compound that can undergo a polymerization reaction when irradiated with active energy rays. Furthermore, the (meth)acrylic acid alkyl ester monomer is a compound that can undergo a polymerization reaction when placed in an anaerobic environment in the presence of an organic peroxide and an amine compound.

[0031] Examples of the monofunctional (meth)acrylic acid alkyl ester monomer include a (meth)acrylic acid alkyl ester monomer having a cyclic hydrocarbon structure in the molecule, and a (meth)acrylic acid alkyl ester monomer having a chain hydrocarbon structure in the molecule.

[0032] In a (meth)acrylic acid alkyl ester monomer having a cyclic hydrocarbon structure in its molecule, the cyclic hydrocarbon structure is preferably a saturated hydrocarbon (alicyclic). Furthermore, such a (meth)acrylic acid alkyl ester monomer preferably has 8 to 15 carbon atoms in its molecule. Furthermore, such a (meth)acrylic acid alkyl ester monomer preferably does not contain a benzene ring, an ether bond (—CH2-O—CH2-), an —OH group, or a —COOH group as a polar group in its molecule. In such a (meth)acrylic acid alkyl ester monomer, the cyclic hydrocarbon structure may be a saturated hydrocarbon structure containing 4 to 8 carbon atoms and containing no heteroatoms. Such a (meth)acrylic acid alkyl ester monomer may be monocyclic, bicyclic, or polycyclic. The bicyclic or polycyclic cyclic hydrocarbon structures may share two or more carbon atoms. In a bicyclic or polycyclic (meth)acrylic acid alkyl ester monomer, at least one cyclic hydrocarbon structure may be a saturated hydrocarbon structure, for example, all of the cyclic hydrocarbon structures may be saturated hydrocarbon structures. In such alkyl (meth)acrylate monomers, a methyl group or an ethyl group may further be bonded to the carbon of the saturated cyclic hydrocarbon structure.

[0033] Specifically, examples of (meth)acrylic acid alkyl ester monomers having a cyclic hydrocarbon structure in the molecule include isobornyl (meth)acrylate, dicyclopentadieneoxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and adamantyl (meth)acrylate. When the curable composition contains a (meth)acrylic acid alkyl ester monomer having a cyclic hydrocarbon structure in the molecule, the cured product obtained by curing the curable composition can have more sufficient moisture resistance and more sufficient electrical insulation properties.

[0034] <Acyl group-containing compounds> The acyl group-containing compound contained in the curable composition of the present embodiment is not particularly limited as long as it has a molecular structure represented by the following formula (1) or the following formula (2). Such an acyl group-containing compound may have the property of generating radicals when irradiated with active energy rays (such as ultraviolet rays). [ka]

[0035] Examples of acyl group-containing compounds having the molecular structure represented by the above formula (1) include (±)-camphorquinone, 3-methylcyclopentane-1,2-dione (CAS: 765-70-8), and 3,5,5-trimethylcyclohexane-1,2-dione (CAS: 57696-89-6).

[0036] Examples of acyl group-containing compounds having the molecular structure represented by the above formula (2) include acylphosphine oxide compounds. Examples of acylphosphine oxide compounds include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (CAS: 162881-26-7) and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (CAS: 75980-60-8). These compounds can have the same effect as a photopolymerization initiator.

[0037] As the acyl group-containing compound, commercially available products can be used.

[0038] <Photopolymerization initiator> The photopolymerization initiator that can be contained in the curable composition of this embodiment is not particularly limited as long as it is a compound that generates radicals upon irradiation with active energy rays (such as ultraviolet rays). However, compounds having the molecular structure of formula (1) or (2) above are excluded. Examples of photopolymerization initiators include acetophenone-based polymerization initiators, o-acyloxime-based polymerization initiators, benzophenone-based polymerization initiators, and thioxanthone-based polymerization initiators. As the photopolymerization initiator, hydrogen abstraction type photopolymerization initiators such as benzophenone-based polymerization initiators and thioxanthone-based polymerization initiators are preferred. Commercially available photopolymerization initiators can be used.

[0039] <Organic peroxide> The organic peroxide contained in the curable composition of this embodiment is not particularly limited, and a general organic peroxide may be used. The organic peroxide is a compound capable of generating radicals, and therefore has the effect of accelerating the reaction when the curable composition is cured under anaerobic conditions. That is, the organic peroxide is a compound capable of accelerating the progress of each polymerization reaction of the (meth)acryloyl group in the polymerizable compound and the (meth)acryloyl group in the (meth)acrylic acid alkyl ester monomer.

[0040] The organic peroxide is preferably an organic peroxide having a 10-hour half-life temperature of 100° C. or higher, which has the advantage of further improving the storage stability of the curable composition.

[0041] The organic peroxide is preferably a hydroperoxide, such as p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, or t-butyl hydroperoxide.

[0042] <Amine compounds> The amine compound that can be contained in the curable composition of this embodiment is not particularly limited, and a general amine compound can be used. The amine compound has the effect of accelerating the reaction when the curable composition is cured under anaerobic conditions. Furthermore, the amine compound has the effect of accelerating the curing reaction of the curable composition when irradiated with active energy rays, particularly with a specific photopolymerization initiator (hydrogen abstraction photopolymerization initiator).

[0043] Examples of the amine compound include secondary amines or tertiary amines having a specific molecular structure. Examples of the amine compound include amine compounds having an aromatic ring structure or amine compounds having a heterocyclic structure. The amine compound preferably includes at least one of a tertiary amine compound having an aromatic ring and a secondary amine compound having a heterocyclic structure.

[0044] The amine compound preferably contains a dimethylaminobenzoic acid ester. By including the specific amine compound in the curable composition, the curing reaction rate of the curable composition can be maintained at a moderate level, allowing the curable composition to reach the interior of the microstructure before the curable composition becomes too viscous as the curing reaction progresses. Therefore, a cured product with good electrical insulation can be produced even inside the microstructure. Additionally, the storage stability of the curable composition can be improved.

[0045] In the curable composition of this embodiment, the mass ratio of the (meth)acrylic acid alkyl ester monomer to the polymerizable compound (urethane (meth)acrylate polymer or oligomer) is preferably 1.0 or more and 5.0 or less, more preferably 3.0 or less, and even more preferably 2.0 or less, which allows the curable composition to reach the interior of the microstructure as described above, and also allows the cured product to have good flexibility.

[0046] In the curable composition of this embodiment, the mass ratio of the specific acyl group-containing compound to the total amount of the polymerizable compound (urethane (meth)acrylate polymer or oligomer) and the (meth)acrylic acid alkyl ester monomer is preferably 0.005 or more and 0.030 or less. A mass ratio of 0.005 or more allows the curable composition to be cured more sufficiently. On the other hand, a mass ratio of 0.030 or less allows the electrical insulation of the cured product to be more reliably ensured.

[0047] In the curable composition of this embodiment, the mass ratio of the organic peroxide to the total amount of the polymerizable compound (urethane (meth)acrylate polymer or oligomer) and the (meth)acrylic acid alkyl ester monomer is preferably 0.005 or more and 0.030 or less. A mass ratio of 0.005 or more allows the curable composition to be cured more sufficiently. On the other hand, a mass ratio of 0.030 or less allows the electrical insulation of the cured product to be more reliably ensured.

[0048] In the curable composition of this embodiment, the mass ratio of the amine compound to the total amount of the polymerizable compound (urethane (meth)acrylate polymer or oligomer) and the (meth)acrylic acid alkyl ester monomer is preferably 0.005 or more and 0.030 or less. A mass ratio of 0.005 or more allows the curable composition to be cured more sufficiently, and the electrical insulation of the cured product to be further improved. On the other hand, a mass ratio of 0.030 or less ensures the electrical insulation of the cured product.

[0049] In the curable composition of this embodiment, the mass ratio of the photopolymerization initiator to the total amount of the polymerizable compound (urethane (meth)acrylate polymer or oligomer) and the (meth)acrylic acid alkyl ester monomer is preferably 0.003 or more and 0.03 or less. When such a mass ratio is 0.003 or more, the curable composition can be cured more sufficiently and the electrical insulation of the cured product can be further improved. On the other hand, when such a mass ratio is 0.03 or less, the electrical insulation of the cured product can be more reliably ensured.

[0050] The curable composition of the present embodiment may contain, as needed, a photosensitizer, a reducing agent that contributes to a curing reaction under anaerobic conditions, a polymerization inhibitor, an antioxidant, a dye (fluorescent dye), a pigment, and the like. Examples of reducing agents include saccharin and organic compounds having an unsaturated double bond and hydrogen bonded to the α-carbon of the unsaturated double bond (e.g., unsaturated fatty acids and butadiene rubber oligomers).

[0051] In the curable composition of this embodiment, the saccharin content is preferably less than 1% by mass (including 0%), and more preferably the curable composition does not contain saccharin. By keeping the saccharin content as low as possible, the electrical insulation properties of the cured product can be further improved. Furthermore, since saccharin is a type of sulfonimide, a lower saccharin content in the cured product can, for example, prevent the generation of strongly acidic compounds due to hydrolysis of saccharin under high temperature and humidity. Furthermore, the generation of corrosive sulfur compounds such as hydrogen sulfide and sulfur dioxide gas due to thermal decomposition of saccharin under high temperature environments can be prevented.

[0052] Next, one embodiment of a method for producing the curable composition according to the present invention will be described.

[0053] The method for producing the curable composition of the present embodiment includes the steps of: The method includes a step of mixing the above-mentioned polymerizable compound having multiple (meth)acryloyl groups in the molecule, a (meth)acrylic acid alkyl ester monomer, an acyl group-containing compound, an organic peroxide, and, if necessary, the above-mentioned photopolymerization initiator or amine compound.

[0054] The method for producing the curable composition of the present embodiment may include, for example, a step of synthesizing the polymerizable compound (urethane(meth)acrylate polymer or oligomer). Note that a commercially available product may be used as the polymerizable compound (urethane(meth)acrylate polymer or oligomer).

[0055] For example, the method for producing the curable composition of the present embodiment includes the following steps: a synthesis step of synthesizing the polymerizable compound (urethane (meth)acrylate polymer or oligomer); The method includes at least a mixing step of mixing the synthesized urethane (meth)acrylate polymer or oligomer, a (meth)acrylic acid alkyl ester monomer, an acyl group-containing compound, and an organic peroxide.

[0056] In the synthesis step, a urethane reaction product is obtained by subjecting at least a bifunctional or higher isocyanate compound, a polyol compound, and a hydroxyl group-containing (meth)acrylate to a urethane reaction. The compounds to be subjected to the urethane reaction are as described above.

[0057] In the synthesis process, in order to prevent unintended reactions due to moisture (water), the air in the reaction vessel is usually replaced with nitrogen before the urethane reaction is carried out.

[0058] In the synthesis step, general reaction conditions suitable for a urethanization reaction can be adopted. Preferably, in the synthesis step, the urethanization reaction is carried out by maintaining a temperature of 60 to 120°C for 0.5 to 3 hours.

[0059] In the synthesis step, the amounts (charge amounts) of the di- or higher functional isocyanate compound (a1), the polyol compound (a2), and the hydroxy group-containing (meth)acrylate (a3) ​​used (charged) are preferably as follows:

[0060] In the synthesis step, it is preferable to carry out the urethane reaction so that the total amount of hydroxy groups (—OH) in the polyol compound (a2) and the hydroxy group-containing (meth)acrylate (a3) ​​is 0.95 mol or more and 1.00 mol or less per 1 mol of isocyanate groups in the bifunctional or higher isocyanate compound (a1). By carrying out the urethane reaction at the above molar ratio, even if a small portion of the isocyanate groups are decomposed due to a trace amount of moisture, all of the hydroxy groups can be reacted quantitatively, and the excess isocyanate groups can be almost completely eliminated, thereby achieving both good electrical insulation properties of the cured product and good storage stability of the curable composition.

[0061] In the synthesis step, the amount of hydroxyl groups (-OH) in the hydroxyl group-containing (meth)acrylate (a3) ​​is preferably 0.2 to 1.0 moles per mole of hydroxyl groups (-OH) in the polyol compound (a2), which has the advantage of providing a cured product with both good electrical insulation and good flexibility.

[0062] In the synthesis step, the molar ratio of the bifunctional isocyanate compound to the polyol compound (a2) (for example, a diol compound) is preferably greater than 1. In the synthesis step, the molar number of isocyanate groups in the bifunctional isocyanate compound (a1) is preferably greater than the molar number of hydroxyl groups in the polyol compound (a2), and the ratio of the molar number of hydroxyl groups in the hydroxyl group-containing (meth)acrylate (a3) ​​to the difference in molar number is preferably 0.95 or more and 1.0 or less, which has the advantage that the cured product can have both good flexibility and good electrical insulation.

[0063] The synthesis step may be a one-step urethanization reaction carried out in the presence of a di- or higher functional isocyanate compound (a1), a polyol compound (a2), a hydroxy group-containing (meth)acrylate (a3), and the like. The synthesis step is preferably carried out in two stages: first, a urethanization reaction is carried out in the presence of a difunctional or higher isocyanate compound (a1) and a polyol compound (a2), and then a urethanization reaction is carried out with a hydroxyl group-containing (meth)acrylate (a3), etc. This makes it possible to more reliably produce a main chain structure formed by the reaction of a difunctional or higher isocyanate compound with a polyol compound.

[0064] In the mixing step, after the urethanization reaction, for example, the above-mentioned (meth)acrylic acid alkyl ester monomer, acyl group-containing compound, organic peroxide, and, if necessary, a photopolymerization initiator or an amine compound are further added.

[0065] In the mixing step, a reducing agent, a photosensitizer, a polymerization inhibitor, an antioxidant, a dye such as a fluorescent dye, a pigment, and the like may be further blended, if necessary.

[0066] The curable composition of the present embodiment can be cured by irradiation with active energy rays such as ultraviolet rays, and can be used as a cured product. Alternatively, the curable composition of the present embodiment can be cured by exposure to an anaerobic environment, and can be used as a cured product. Specifically, the curable composition may be applied to the area to be coated, and then irradiated with light such as ultraviolet light to cure the composition and form a cured coating film. Furthermore, in areas that are not irradiated with light and are kept sealed, the curing reaction can be carried out under anaerobic conditions. Even when the curable composition is not kept sealed, the curing reaction of the curable composition can be carried out by eliminating the influence of oxygen gas using an oxygen scavenger, nitrogen substitution treatment, vacuum treatment, or the like. The curable composition of the present embodiment may be cured by both a curing reaction caused by light and a curing reaction in an anaerobic environment, or by either one of the curing reactions.

[0067] The active energy rays used to promote the curing reaction include, for example, ultraviolet light, infrared light, radiation, and electron beams. The light to be irradiated is preferably ultraviolet light. The light source may be a high-pressure mercury lamp, a metal halide lamp, a xenon lamp, a chemical lamp, an LED lamp, or the like. The irradiation intensity may be, for example, 100 W / cm. 2 More than 10,000mW / cm 2 The following can be adopted:

[0068] The temperature for promoting the curing reaction under anaerobic conditions is preferably 20 to 40° C., and the oxygen concentration is preferably less than 5 mg / L. Specific locations that become anaerobic include, for example, the gap between an IC package or a mounted component and a printed circuit board, a through-hole portion of a printed circuit board, an internal electrode portion of a chip component, a location that is covered with a cured product cured by light irradiation and is not sufficiently irradiated with light, or the back side of a lead portion of an IC package.

[0069] The object to be coated with the curable composition contains a metal in part. More specifically, at least a portion of the surface of the object to be coated with the curable composition may be formed of a metal. This further promotes curing of the curable composition. The metal is not particularly limited, but examples include copper, silver, iron, titanium, nickel, manganese, cobalt, tin, and lead. The metal may contain multiple types of metals such as those listed above. When a metal is present on the coated surface, the curing of the curable composition proceeds relatively quickly under anaerobic conditions. The curing reaction eventually proceeds even in areas away from the metal, producing a cured product. Because the resulting cured product is not liquid, it will not leak unintentionally under pressure.

[0070] The object to be protected by coating and covering with the curable composition (object to be protected) is mainly a component of an electric circuit or an electronic circuit. Examples of the object to be protected (the component) include a substrate, a mounted component, a connection between a mounted component and a substrate, and a connection between substrates. Examples of objects to be protected include wiring and terminals on mounting boards or mounted components used in precision equipment, wiring and terminals on mounting boards installed in automobiles, bicycles, trains, airplanes, ships, etc., wiring and terminals on mounting boards used in mobile devices (cell phones, digital cameras, digital video cameras, etc.), wiring and terminals on boards used in outdoor equipment (water heaters, air conditioner outdoor units, etc.), and wiring and terminals on mounting boards used in wet equipment such as washing machines, warm water toilet seats, and dishwashers.

[0071] For example, as shown in Figure 2A, when the curable composition is applied to a portion of the surface of an IC package, the curing reaction of the curable composition progresses in the portion (denoted by U) irradiated with active energy rays (such as ultraviolet rays). In portions that could become anaerobic even without active energy rays, the curing reaction of the curable composition progresses under anaerobic conditions, particularly in the portion (denoted by K) close to the metal (denoted by m1). The curing reaction also progresses and solidifies in the portion (denoted by G) away from the metal and not reached by the active energy rays. Furthermore, for example, as shown in FIG. 2B, when the curable composition is applied to a portion of the surface of a chip component having ceramics (s), a protective film (h), internal electrodes (m2), external electrodes (m3), and solder (m4), the curable composition proceeds to a curing reaction in the portion (U) irradiated with active energy rays (e.g., ultraviolet light). In portions that could become anaerobic even without active energy rays, the curable composition proceeds to a curing reaction under anaerobic conditions, particularly in portions (K) close to metal (m2, m3, m4). Furthermore, the curing reaction also proceeds to solidify in portions (G) away from the metal and not reached by active energy rays. 2C, in areas that may become anaerobic, such as through-holes on the back of components, the curing reaction of the curable composition proceeds under anaerobic conditions, particularly in areas (indicated by K) close to the metal (indicated by m4). The curing reaction also proceeds and solidifies in areas (indicated by G) far from the metal. Furthermore, for example, as shown in Fig. 2D, when the curable composition is applied to a portion of the surface of a BGA (ball grid array, a package substrate having an electrode configuration in which solder balls are arranged in a grid pattern), the curing reaction of the curable composition progresses in the portion (denoted by U) irradiated with active energy rays (such as ultraviolet rays). In the portion (denoted by G) that can become anaerobic even without the active energy rays, the curing reaction progresses and the composition solidifies.

[0072] The curable composition, cured product, and method for producing the curable composition of the present embodiment are as exemplified above, but the present invention is not limited to the curable compositions exemplified above. That is, various forms used in general curable compositions can be employed as long as they do not impair the effects of the present invention.

[0073] The matters disclosed by this specification include the following. [1] A curable composition for protecting a circuit, comprising: a polymerizable compound having a plurality of (meth)acryloyl groups in the molecule; a (meth)acrylic acid alkyl ester monomer; an acyl group-containing compound having a molecular structure represented by the following formula (1) or (2); and an organic peroxide: [ka] [2] The curable composition for protecting a circuit according to the above [1], wherein the acyl group-containing compound having a molecular structure represented by formula (1) is camphorquinone. [3] The curable composition for protecting a circuit according to the above [1] or [2], wherein the organic peroxide is a hydroperoxide exhibiting a 10-hour half-life temperature of 100°C or higher. [4] The curable composition for circuit protection according to any one of [1] to [3] above, wherein the polymerizable compound is at least a urethane reaction product of a bifunctional or higher isocyanate compound, a polyol compound, and a hydroxy group-containing (meth)acrylate. [5] The curable composition for protecting a circuit according to any one of [1] to [4] above, wherein the (meth)acrylic acid alkyl ester monomer contains a (meth)acrylic acid alkyl ester monomer having a cyclic hydrocarbon structure in the molecule. [6] The curable composition for protecting a circuit according to any one of the above [1] to [5], further comprising an amine compound. [7] The curable composition for protecting a circuit according to the above [6], wherein the amine compound is 4-dimethylaminobenzoic acid ester. [8] the polyol compound of the polymerizable compound is a polyolefin polyol, The curable composition for protecting a circuit according to [4] above, wherein the polyolefin portion of the polyolefin polyol has an unsaturated double bond and a hydrogen atom bonded to the α-carbon atom of the unsaturated double bond. [9] A cured product of the curable composition for circuit protection according to any one of [1] to [8] above, which is adhered to an object to be protected.

[10] A control part comprising a cured product of the curable composition for circuit protection according to any one of [1] to [9] above, and a component of an electric or electronic circuit, at least a portion of whose surface is covered with the cured product. [Example]

[0074] The present invention will now be described in more detail with reference to experimental examples, but the present invention is not limited to these examples.

[0075] A curable composition was produced by mixing [A] a urethane (meth)acrylate oligomer as a polymerizable compound, [B] a (meth)acrylic acid alkyl ester monomer, [C] an acyl group-containing compound, [E] an amine compound, and [F] an organic peroxide, etc., as follows.

[0076] <Ingredient details> [A] Polymerizable compound having (meth)acryloyl groups (theoretical average of two functional groups) in the molecule [UA-1] · Urethane acrylate oligomer (polymerizable polyurethane oligomer) commercially available products Product name: "NK Oligo UA-290TM" manufactured by Shin-Nakamura Chemical Co., Ltd. [UA-2] Urethane acrylate oligomer (polymerizable polyurethane oligomer) shown in Synthesis Example 1 [UA-3] Urethane acrylate oligomer (polymerizable polyurethane oligomer) shown in Synthesis Example 2 [UA-4] Urethane acrylate oligomer (polymerizable polyurethane oligomer) shown in Synthesis Example 3 [Raw materials for Synthesis Examples 1 to 3] (a1) Bifunctional isocyanate compound (alicyclic diisocyanate compound) 1,3-bis(isocyanatomethyl)cyclohexane (HXDI) (Product name: "Takenate 600" manufactured by Mitsui Chemicals, Inc.) (a2) Diol compound Polypropylene glycol (PPG) (Product name: Sannix PP600, manufactured by Sanyo Chemical Industries, Ltd.) Hydroxyl value: 187 [KOHmg / g] Branched polyolefin diol (Non-hydrogenated 1,2-polybutadiene diol with -OH groups at both ends) (Product name: "G-1000" manufactured by Nippon Sodasha) Hydroxyl value: 76 [KOHmg / g] (a3) Hydroxy group-containing (meth)acrylate 2-Hydroxyethyl acrylate (Product name: "Aclix HEA" manufactured by Toagosei Co., Ltd.) (z1) Urethane reaction catalyst Dibutyltin dilaurate reagent (z2) Polymerization inhibitor 1,4-Benzoquinone Reagent [B] (Meth)acrylic acid alkyl ester Isobornyl acrylate (IBXA) (commercial product, contains 100 ppm MEHQ) [C] Acyl group-containing compound (±)-Camphorquinone (CQN), a commercially available reagent (with hydrogen abstraction effect) 3-Methylcyclopentane-1,2-dione (PDN), commercially available reagent 3,5,5-trimethylcyclohexane-1,2-dione (HDN) commercially available reagent Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (BTPO) (Product name: Omnirad 380, manufactured by IGM Resins) [D] Photopolymerization initiator 4-Benzoyl-4'-methyldiphenyl sulfide (BMS) (Product name: Omnirad 705, manufactured by IGM Resins) Benzophenone-based (hydrogen abstraction) photoinitiator Reference: 2,4-Diethylthioxanthone (DETX) (Product name: "KAYACURE DETX-S" manufactured by Nippon Kayaku Co., Ltd.) Thioxanthone-based (hydrogen abstraction) photopolymerization initiator [E] Amine compound (polymerization accelerator) Ethyl dimethylaminobenzoate (DMB) (a tertiary amine with an aromatic ring structure) [F] Organic peroxides (all of which have a 10-hour half-life temperature of 100°C or higher) t-Butyl hydroperoxide (tBPO) Cumene hydroperoxide (CHPO) [G] Reducing agent for anaerobic curing Saccharin (SAC)

[0077] (Synthesis Example 1) The synthesis process was carried out by carrying out a urethane reaction at 90°C for 2 hours using the formulation shown in Table 1. The urethane reaction was carried out by adding (a1) to (a3), the urethane reaction catalyst, and the polymerization inhibitor all at once at room temperature under a nitrogen purge. In Table 1, the numbers in parentheses indicate the relative molar ratio of the molecules of each component. The molar ratio of the diol compound to the difunctional isocyanate compound was 5 / 6, and the theoretical degree of polymerization was 5.

[0078] (Synthesis Examples 2 and 3) Curable compositions were synthesized in the same manner as in Example 1, except that the blending amounts were changed to those shown in Table 1. In Synthesis Example 3, the molar ratio of diol compound / difunctional isocyanate compound was 1 / 2, and the theoretical degree of polymerization was 1.

[0079] In Synthesis Examples 1 to 3, IBXA was used as a reaction solvent, the concentration of the raw materials before the reaction was adjusted to 39.5 mass %, and the viscosity of the solution before the reaction was adjusted to 500 mPa·s or more and 900 mPa·s. Furthermore, when the urethane reaction products produced by the synthesis steps of Synthesis Examples 1 to 3 were analyzed by FT-IR, -1 The absorption of the isocyanate group around 1730 cm disappeared. -1 The increase in absorption of the nearby carbonyl group confirmed that a compound with a urethane bond had been synthesized.

[0080] [Table 1]

[0081] (Examples and Comparative Examples) Each curable composition was produced by mixing the raw materials in the amounts shown in Tables 2 to 4. In Comparative Examples 5 and 6, a commercially available curable composition (containing an isocyanate compound) for both photocuring and moisture curing was used. In Table 3, the amount of [B]IBXA in Examples 9 to 11 represents the total amount in the composition.

[0082] [Table 2]

[0083] [Table 3]

[0084] [Table 4]

[0085] The curable compositions prepared in the Examples and Comparative Examples were evaluated as follows: Specifically, the electrical insulation resistance of the cured products (cured films) prepared by curing the prepared curable compositions was measured.

[0086] <Hardening treatment> As shown in FIG. 3, the curing treatment was carried out by the following operations, and then the insulation resistance value was measured. A JIS II-type comb-shaped substrate (rectangular, copper thickness 35 μm) was prepared, with its back surface covered with polyimide film adhesive tape (Nitto Denko No. 360UL, tape thickness 0.06 μm). Two 3 mm-wide pieces of polyester tape (Nitto Denko N-300, tape thickness 0.10 μm) were attached to the surface along three sides of the comb-shaped substrate (excluding the side where the terminals were located). This tape was used as a spacer to prevent the composition from running off and to ensure that the composition cured at a predetermined thickness. The electrode area was masked with polyimide film adhesive tape, and then, using the polyester tape as a spacer, each curable composition was applied to one side of the comb-shaped substrate (copper thickness 35 μm) to a thickness of 200 μm. Two such samples were prepared. Then, one of the samples was exposed to a 500W metal halide lamp with an integrated light intensity of 3000mJ / cm 2 The sample was irradiated with ultraviolet light so that the light intensity was 1000 .mu.m (light-irradiated cured sample). The other sample was left to stand under the anaerobic conditions described below and cured under anaerobic conditions. Specifically, a glass epoxy substrate (one side entirely covered with the polyimide film adhesive tape) was prepared so as to be able to block ultraviolet light. Next, the coated portion of each sample (the surface coated with each curable composition) was placed facing the other side of the glass epoxy substrate without the adhesive tape, thereby placing the curable composition of each sample under anaerobic conditions. Furthermore, the comb-shaped substrate and the glass epoxy substrate were clamped with two binder clips so that a compressive force was applied in the thickness direction. The sample thus obtained was placed in a dark place and subjected to anaerobic conditions for 14 days, and then cured under anaerobic conditions (anaerobic-cured sample).

[0087] <Insulation resistance value> The adhesive tape masking the electrodes was removed from each test sample that had been cured (by light irradiation or anaerobic curing) as described above, and vinyl-coated copper wires were soldered to the electrodes. A DC voltage of 100 V was then applied to the comb-shaped electrodes, and the insulation resistance values ​​of the three comb-shaped wires were measured after 60 seconds, and the average value was calculated.

[0088] <Number of days until the curable composition solidifies> 3.0 g of the curable composition was weighed into an aluminum cup with a circular bottom diameter of 30 mm. This aluminum cup and an oxygen absorber (food oxygen absorber manufactured by Mitsubishi Gas Chemical Company, Inc., product name "Ageless S-100") were placed together in a barrier film packaging bag (Fukusuke Kogyo Co., Ltd., Barrier OPY type), and the bag was sealed using a thermal laminator. The test sample thus prepared was stored in a dark place at 20°C, and the number of days until the contents no longer flowed when the aluminum cup was tilted was measured.

[0089] <Viscosity of Curable Composition> 120 g of the curable composition was placed in a 250 mL light-shielding plastic bottle, and the viscosity at 25°C was measured using a Toki Sangyo RE-85R E-type viscometer. The viscosity was measured immediately after production and after 3 months at 20°C.

[0090] The evaluation results are shown in Tables 2 to 4. As can be seen from the evaluation results, the curable compositions of the Examples cured in a relatively short time under anaerobic conditions compared to the compositions of the Comparative Examples, and the cured products of the curable compositions of the Examples had high insulation resistance values ​​in both the light-irradiated portion and the portion cured under anaerobic conditions.

[0091] Conventional curable compositions for adhesive applications contain inorganic or organic reducing agents that reduce electrical insulation properties, and therefore, if such curable compositions for adhesive applications are simply applied to electrical insulation applications, it is expected that the reliability of the product will be impaired in terms of electrical insulation properties. [Industrial Applicability]

[0092] The curable composition (curable composition) of the present invention is used by being applied to circuit components constituting electronic circuits, electric circuits, etc., in order to cover at least a portion of the surface of the object to be protected with a cured product. Thereafter, it is cured by light irradiation or under anaerobic conditions, and the cured product adhered to the object to be protected is suitably used. The curable composition of the present invention is suitably used, for example, as a curable composition for insulating coatings (anaerobic curable composition for circuit protection).

Claims

1. A curable composition for protecting a circuit, comprising: a polymerizable compound having a plurality of (meth)acryloyl groups in the molecule; a (meth)acrylic acid alkyl ester monomer; an acyl group-containing compound having a molecular structure represented by the following formula (1) or (2); and an organic peroxide: 【Chemistry 1】

2. 2. The curable composition for protecting a circuit according to claim 1, wherein the acyl group-containing compound having a molecular structure represented by formula (1) is camphorquinone.

3. The curable composition for protecting a circuit according to claim 1 or 2, wherein the organic peroxide is a hydroperoxide having a 10-hour half-life temperature of 100°C or higher.

4. 3. The curable composition for protecting a circuit according to claim 1, wherein the polymerizable compound is a urethane reaction product of at least a difunctional or higher functional isocyanate compound, a polyol compound, and a hydroxy group-containing (meth)acrylate.

5. The curable composition for protecting a circuit according to claim 1 or 2, wherein the (meth)acrylic acid alkyl ester monomer contains a (meth)acrylic acid alkyl ester monomer having a cyclic hydrocarbon structure in the molecule.

6. The curable composition for protecting a circuit according to claim 1 or 2, further comprising an amine compound.

7. The curable composition for protecting a circuit according to claim 6, wherein the amine compound is a 4-dimethylaminobenzoic acid ester.

8. the polyol compound of the polymerizable compound is a polyolefin polyol, The curable composition for protecting circuits according to claim 4 , wherein the polyolefin moiety of the polyolefin polyol has an unsaturated double bond and a hydrogen atom bonded to the α-carbon atom of the unsaturated double bond.

9. A cured product of the curable composition for circuit protection according to claim 1 or 2, which is adhered to an object to be protected.

10. A control part comprising a cured product of the curable composition for circuit protection according to claim 1 or 2, and a component of an electric or electronic circuit, at least a portion of the surface of which is covered with the cured product.

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