Photocurable resin composition

Abstract

To provide a resin composition that allows curing to a deep region by irradiation with energy rays.SOLUTION: The present invention relates to a photocurable resin composition comprising a radical polymerizable component (A), a photopolymerization initiator (B), a filler (C), and an organic peroxide (D), wherein the component (A) includes a polyfunctional (meth)acrylate (A1) and / or a monofunctional (meth)acrylate (A2) having a (meth)acrylamide group, the component (B) is an intramolecular cleavage-type photoradical polymerization initiator, the component (C) has a specific gravity of 4.0 or more, a total content of the component (A1) and the component (A2) is 26 pts.mass or more and 100 pts.mass or less with respect to 100 pts.mass of the component (A), and a content of the component (D) is 1.3 pts.mass or more with respect to 100 pts.mass of the component (A).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photocurable resin composition. [Background technology]

[0002] If the rotating body of a rotating electrical device, such as a motor, is not perfectly balanced, it will generate a lot of vibration during rotation. One method for achieving this balance is to apply a photocurable adhesive for balance adjustment as a weight. The specific gravity of a photocurable adhesive that does not contain a filler is low, at around 1. Therefore, when adjusting the weight using only a photocurable adhesive that does not contain a filler, a large amount of adhesive must be applied. This has the disadvantage that, in motors that have become increasingly smaller in recent years, there is not enough space for the adhesive to fill, making it difficult to achieve sufficient balance adjustment.

[0003] Patent Document 1 discloses a photocurable resin composition for motor balances, which contains a compound having an ethylenically unsaturated group, an inorganic filler, a catalyst that absorbs light in the visible light region, and a catalyst that is activated by heating. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-104705 Summary of the Invention [Problem to be solved by the invention]

[0005] In the photocurable resin composition disclosed in Patent Document 1, depending on the refractive index of the inorganic filler, the light may not reach deep into the composition during irradiation, making it impossible to cure the entire composition. This tendency is particularly pronounced when an inorganic filler with a specific gravity of 4.0 or more is used.

[0006] An object of the present invention is to provide a resin composition that can be cured to a deep portion by irradiation with energy rays. [Means for solving the problem]

[0007] The present invention relates to the following: [1] A photocurable resin composition comprising a radical polymerization reactive component (A), a photopolymerization initiator (B), a filler (C), and an organic peroxide (D), The component (A) contains a polyfunctional (meth)acrylate (A1) and / or a monofunctional (meth)acrylate having a (meth)acrylamide group (A2), Component (B) is an intramolecular cleavage-type photoradical polymerization initiator, Component (C) has a specific gravity of 4.0 or more, the total content of component (A1) and component (A2) is 26 parts by mass or more and 100 parts by mass or less per 100 parts by mass of component (A), The content of component (D) is 1.3 parts by mass or more relative to 100 parts by mass of component (A). Photocurable resin composition. [2] The photocurable resin composition according to [1], wherein the acrylic equivalent of components (A1) and (A2) contained in component (A) is 1,000 g / eq or less. [3] The photocurable resin composition according to [1] or [2], wherein the content of component (C) is 70 parts by mass or more and 1,000 parts by mass or less per 100 parts by mass of component (A). [4] The photocurable resin composition according to any one of [1] to [3], which is used for a balance weight of a rotating body. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a resin composition that can be cured to a deep portion by irradiation with energy rays. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Term definition] The term "(meth)acrylate" means at least one of acrylate and methacrylate. The term "(meth)acryloyl group" refers to at least one of an acryloyl group and a methacryloyl group. The term "(meth)acrylamide group" refers to at least one of an acrylamide group and a methacrylamide group. The "radical polymerization reactive component (A)" is also referred to as "component (A)." The same applies to the "photopolymerization initiator (B)" and the like. With regard to numerical ranges, "to" means that both ends of the range are included. Also, "less than" means "the same as or less than," and "more than" means "the same as or greater than."

[0010] [Photocurable resin composition] The photocurable resin composition comprises a radical polymerization reactive component (A), a photopolymerization initiator (B), a filler (C), and an organic peroxide (D), wherein component (A) comprises a polyfunctional (meth)acrylate (A1) and / or a monofunctional (meth)acrylate (A2) having a (meth)acrylamide group, component (B) is an intramolecular cleavage-type photoradical polymerization initiator, component (C) has a specific gravity of 4.0 or more, the total content of components (A1) and (A2) is 26 parts by mass or more and 100 parts by mass or less per 100 parts by mass of component (A), and the content of component (D) is 1.3 parts by mass or more per 100 parts by mass of component (A).

[0011] Photocurable resin compositions can be cured to their depths by irradiation with light (energy rays). That is, photocurable resin compositions have deep curing properties. This can reduce the impact on surrounding components caused by remaining uncured resin composition. Furthermore, light irradiation activates the intramolecular cleavage-type photoradical polymerization initiator (B), which then proceeds with the polymerization reaction of the radical polymerization reactive component (A), generating heat. Furthermore, light irradiation may cause the filler (C) to absorb light and generate heat. This heat generation heats the interior of the photocurable resin composition, which is not penetrated by light. This heating is thought to cleave the organic peroxide (D) and generate radicals, thereby curing the interior, which is not accessible to light. Therefore, photocurable resin compositions are thought to have excellent deep curing properties regardless of the refractive index of the component (C). Furthermore, even if component (C) is a filler that reflects light (e.g., a metal filler), the photocurable resin composition is thought to have excellent deep curing properties.

[0012] Furthermore, the photocurable resin composition tends to have a high specific gravity because it contains component (C) with a specific gravity of 4.0 or more, which makes it possible to efficiently adjust the rotational balance of the rotating body.

[0013] <Radical polymerization reactive component (A)> The radical polymerization reactive component (A) contains a polyfunctional (meth)acrylate (A1) and / or a monofunctional (meth)acrylate having a (meth)acrylamide group (A2).

[0014] · Polyfunctional (meth)acrylate (A1) The polyfunctional (meth)acrylate (A1) is a component having a (meth)acryloyl group as a radical polymerization reactive group.

[0015] Examples of the component (A1) include epoxy (meth)acrylates, urethane (meth)acrylates, and other polyfunctional (meth)acrylates.

[0016] Epoxy (meth)acrylate is an epoxy resin in which all epoxy groups have reacted with (meth)acrylic acid. Epoxy (meth)acrylate is an epoxy resin in which some of the epoxy groups have reacted with (meth)acrylic acid; that is, the resin may contain a radical polymerization reactive component having epoxy groups and (meth)acryloyl groups. Examples of epoxy resins include aromatic epoxy resins, aliphatic epoxy resins, alicyclic epoxy resins, and other epoxy resins. Commercially available epoxy (meth)acrylates include EB3700 (manufactured by Daicel-Allnex) and EB3708 (manufactured by Daicel-Allnex).

[0017] Examples of urethane (meth)acrylates include aromatic, aliphatic, polyether, polycarbonate, polyester, and combinations thereof. Commercially available urethane (meth)acrylates include EBECRYL4858 (manufactured by Daicel-Allnex Co., Ltd.), UN-2301 (manufactured by Negami Chemical Co., Ltd.), EBECRYL4859 (manufactured by Daicel-Allnex Co., Ltd.), and EBECRYL4738 (manufactured by Daicel-Allnex Co., Ltd.).

[0018] Other polyfunctional (meth)acrylates are components having two or more (meth)acryloyl groups in the molecule. Examples of other polyfunctional (meth)acrylates include ethoxylated 1,6-hexanediol di(meth)acrylate, 1,6-hexanediol acrylic acid polymer ester, polyester di(meth)acrylate, polyethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, epichlorohydrin-modified glycerol tri(meth)acrylate, ethoxylated glycerol tri(meth)acrylate, PO (propylene oxide)-modified glycerol tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, alkoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol octa(meth)acrylate, and polypentaerythritol poly(meth)acrylate. Furthermore, the other polyfunctional (meth)acrylate may be a component having two or more (meth)acrylamide groups in the molecule.

[0019] The number of (meth)acryloyl groups contained in component (A1) is preferably 2 to 6, and particularly preferably 2 to 4.

[0020] Component (A1) may be one type or a combination of two or more types.

[0021] Monofunctional (meth)acrylate with (meth)acrylamide group (A2) The monofunctional (meth)acrylate (A2) having a (meth)acrylamide group is a component having a (meth)acrylamide group as a radical polymerization reactive group. Examples of the component (A2) include compounds represented by the following formula (1):

[0022] [ka]

[0023] [During the ceremony, R 1is a hydrogen atom or a methyl group, R 2 and R 3 are each independently a hydrogen atom, an alkyl group, a hydroxyalkyl group, or an aryl group that is unsubstituted or substituted with one or more groups selected from the group consisting of a hydroxyl group and an alkyl group, or R 2 and R 3 together with the N atom to which they are attached form an alicyclic group (preferably a morpholino group) which may contain an oxygen atom.

[0024] In formula (1), the number of carbon atoms in the alkyl group and the alkyl moiety of the hydroxyalkyl group is preferably 1 to 18, and particularly preferably 1 to 6. The number of carbon atoms in the aryl group is preferably 6 to 20. The aryl group is preferably a phenyl group. The morpholino group refers to a monovalent group in which a hydrogen atom has been removed from the secondary amine portion of morpholine.

[0025] Examples of the component (A2) include (meth)acrylamides; N-alkyl(meth)acrylamides having an alkyl group having 1 to 4 carbon atoms, such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, and N-butyl(meth)acrylamide; N,N-dialkyl(meth)acrylamides having an alkyl group having 1 to 4 carbon atoms, such as N,N-dimethyl(meth)acrylamide and N,N-diethyl(meth)acrylamide; N-(2-hydroxyethyl)(meth)acrylamide, N-(3-hydroxypropyl)(meth)acrylamide, and N-(4 Examples of (meth)acrylamides include N-hydroxyalkyl (meth)acrylamides having an alkyl group having 2 to 4 carbon atoms, such as N-(2-hydroxybutyl) (meth)acrylamide; (meth)acrylamides having an unsubstituted or substituted aryl group, such as N-phenyl (meth)acrylamide, N-(2-hydroxyphenyl) (meth)acrylamide, N-(3-hydroxyphenyl) (meth)acrylamide, N-(4-hydroxyphenyl) (meth)acrylamide, and N-(2-methylphenyl) (meth)acrylamide; and (meth)acrylamides having a cyclic structure, such as 4-(meth)acryloylmorpholine. From the viewpoint of deep curing properties, N-hydroxyethyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, and 4-(meth)acryloylmorpholine are preferred.

[0026] Component (A2) may be one type or a combination of two or more types.

[0027] Further radical polymerization reactive component (A3) The component (A) may further contain a radical polymerization reactive component (A3) other than the components (A1) and (A2).

[0028] Component (A3) is not particularly limited as long as it has a radically polymerizable functional group. The radically polymerizable functional group is not particularly limited as long as it is an unsaturated double bond-containing group, but is preferably an alkenyl group (e.g., a vinyl group, an allyl group, etc.) or a (meth)acryloyl group, and particularly preferably a (meth)acryloyl group. Examples of component (A3) include a polyfunctional radically polymerizable component having two or more unsaturated double bond-containing groups other than a (meth)acryloyl group as the radically polymerizable group, and a monofunctional (meth)acrylate having one (meth)acryloyl group (excluding component (A2)).

[0029] Examples of component (A3) include monofunctional (meth)acrylates (excluding component (A2)). Monofunctional (meth)acrylates (excluding component (A2)) are components that do not have a (meth)acrylamide group. Examples of monofunctional (meth)acrylates (excluding component (A2)) include alicyclic (meth)acrylates, hydroxyl group-containing (meth)acrylates, aromatic (meth)acrylates, alkyl (meth)acrylates, and (meth)acrylates having a heterocyclic structure.

[0030] Examples of the alicyclic (meth)acrylate include isobornyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, norbornene (meth)acrylate, dicyclopentanyl (meth)acrylate, and cyclohexyl (meth)acrylate.

[0031] Examples of the hydroxyl group-containing (meth)acrylate include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and diethylene glycol monoethyl ether (meth)acrylate.

[0032] Examples of aromatic (meth)acrylate monomers include benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, ethoxylated o-phenylphenol acrylate, phenoxybenzyl (meth)acrylate, phenylphenolethyloxy (meth)acrylate, and naphthalene (meth)acrylate.

[0033] Examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, tert-butyl (meth)acrylate, isooctyl (meth)acrylate, isomyristyl (meth)acrylate, and lauryl (meth)acrylate.

[0034] Examples of the (meth)acrylate having a heterocyclic structure include tetrahydrofurfuryl (meth)acrylate.

[0035] Component (A3) is preferably an alicyclic (meth)acrylate and / or aromatic (meth)acrylate monomer, and is particularly preferably an alicyclic (meth)acrylate. Component (A3) may be one type or a combination of two or more types.

[0036] <Characteristics of Component (A)> Acrylic equivalent The acrylic equivalent of components (A1) and (A2) contained in component (A) is preferably 1,000 g / eq or less, and particularly preferably 100 to 800 g / eq. When the acrylic equivalent of components (A1) and (A2) contained in component (A) is 1,000 g / eq or less, the number of reaction sites in the composition tends to increase. Furthermore, the heat generated by the entire composition during curing increases, which tends to result in better curability.

[0037] When component (A) contains component (A1) but does not contain component (A2), the "acrylic equivalent of components (A1) and (A2) contained in component (A)" means the acrylic equivalent of component (A1). The same applies when component (A) contains component (A2) but does not contain component (A1).

[0038] ·Molecular weight When component (A1) has a molecular weight distribution, the weight-average molecular weight of component (A1) is preferably at least 200, and particularly preferably from 300 to 20,000. A commonly known method for measuring the weight-average molecular weight of relatively high-molecular-weight components such as oligomers and polymers is to convert the results of gel permeation chromatography (GPC) measurement using a calibration curve of standard polystyrene.

[0039] When component (A1) does not have a molecular weight distribution, the molecular weight of component (A1) can be determined from the structural formula. The molecular weight of component (A1) is preferably 200 or more, and particularly preferably 300 to 10,000. When component (A1) does not have a molecular weight distribution, the molecular weight of component (A1) can be determined from the structural formula.

[0040] The molecular weight of component (A2) is preferably 100 or more, and particularly preferably 100 to 1,000. Generally, component (A2) does not have a molecular weight distribution, and therefore the molecular weight of component (A2) can be determined from the structural formula.

[0041] <<Preferred Embodiments of Component (A)>> When component (A) contains component (A1) but does not contain component (A2), component (A) may also contain component (A3). When component (A) contains component (A2) but does not contain component (A1), component (A) may or may not contain component (A3). Furthermore, the component (A) may consist of only the component (A1) and the component (A2).

[0042] <Photopolymerization initiator (B)> The photopolymerization initiator (B) is an intramolecular cleavage-type photoradical polymerization initiator. Component (B) generates radicals upon irradiation with energy rays, and these radicals can initiate a polymerization reaction. Examples of component (B) include acetophenone-based photopolymerization initiators, benzyl ketal-based photopolymerization initiators, and phosphine oxide-based photopolymerization initiators.

[0043] Examples of acetophenone-based photopolymerization initiators include 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone-1,2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2-methyl-1-[4-methylthio]phenyl]-2-morpholinopropan-1-one, 2-hydroxy-2-methyl-1-phenyl-1-propanone, oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone], and oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone].

[0044] Examples of benzil ketal photopolymerization initiators include 2,2-dimethoxy-1,2-diphenylethan-1-one.

[0045] Examples of the phosphine oxide photopolymerization initiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide.

[0046] Commercially available products of component (B) include KIP-150 manufactured by DKSH Japan, and the Omnirad® series, such as Omnirad184, Omnirad819, Omnirad127, and Omnirad1173, the Darocur® series, such as Darocur1173, and the Lucirin® series, such as Lucirin TPO, all manufactured by IGM Resins BV. From the viewpoint of reducing the susceptibility to oxygen inhibition, which can cause non-curing in the radical reaction of component (A), Omnirad1173, Omnirad819, and Omnirad184 are preferred. Component (B) may be one type or a combination of two or more types.

[0047] <Filler (C)> The photocurable resin composition contains a filler (C) having a specific gravity of 4.0 or more. If the specific gravity of the filler is less than 4.0, the specific gravity of the composition cannot be increased efficiently. Furthermore, in such cases, using a large amount of filler to increase the specific gravity of the composition tends to result in poor fluidity of the composition. From the viewpoint of efficiently increasing the specific gravity of the photocurable resin composition and suppressing sedimentation of component (C) in the photocurable resin composition to prevent the formation of a concentration gradient, the specific gravity of component (C) is preferably 4.0 or more and 20.0 or less, particularly preferably 4.0 or more and 18.0 or less. The specific gravity of component (C) can be measured according to JIS K 6833.

[0048] Examples of the component (C) include inorganic fillers, such as metal fillers, metal oxide fillers, and other inorganic fillers.

[0049] Examples of the metal filler include silver (Ag), copper (Cu), gold (Au), aluminum (Al), magnesium (Mg), rhodium (Rh), tungsten (W), molybdenum (Mo), cobalt (Co), nickel (Ni), platinum (Pt), palladium (Pd), chromium (Cr), tantalum (Ta), lead (Pb), vanadium (V), zirconium (Zr), titanium (Ti), indium (In), iron (Fe), zinc (Zn), and alloys thereof.

[0050] Examples of the metal oxide filler include fillers of metal oxides such as magnesium oxide, aluminum oxide, silicon oxide, zirconium oxide, titanium oxide, zinc oxide, tin oxide, and indium oxide.

[0051] Other inorganic fillers include glass fillers, clay mineral fillers such as talc, kaolinite, and smectite, nitride fillers such as silicon nitride, aluminum nitride, and titanium nitride, boride fillers such as boron nitride, titanium boride, and boron oxide, and hydroxide fillers such as aluminum hydroxide and magnesium hydroxide. Further other inorganic fillers include barium sulfate, strontium carbonate, barium carbonate, and potassium iodide.

[0052] Metal oxide fillers and other inorganic fillers tend to have lower thermal conductivity than metal fillers, so when component (C) is a metal oxide filler or other inorganic filler, it tends to be difficult for the reaction heat generated by light irradiation to be dissipated, which tends to further improve deep curing.

[0053] Component (C) is preferably at least one selected from the group consisting of zirconium oxide, magnesium oxide, aluminum oxide, glass, barium sulfate, barium carbonate, strontium carbonate, potassium iodide, tungsten (W), and molybdenum (Mo).

[0054] From the viewpoint of good dispersibility in the photocurable resin composition, the average particle size of component (C) is preferably 0.5 to 150 μm, and particularly preferably 1 to 100 μm. In this specification, the average particle size of component (C) is the median size (D50).

[0055] Component (C) may be a commercially available product or may be produced by a known method. For example, a powdered glass filler can be obtained by producing glass from various raw materials by a common method such as melt quenching, vapor phase synthesis, or sol-gel method, followed by a pulverization step and, if necessary, adjusting the particle size with a sieve. The average particle size of the resulting glass filler can be adjusted by adjusting the degree of pulverization in these pulverization steps.

[0056] Component (C) may be one type or a combination of two or more types.

[0057] <Organic peroxide (D)> The organic peroxide (D) is a compound containing a peroxy group (-OO-). Component (D) is a radical source. The radicals generated from component (D) accelerate the curing reaction.

[0058] Examples of the organic peroxide (D) include diacyl peroxides, hydroperoxides, dialkyl peroxides, peroxyketals, peroxyesters, and peroxycarbonates.

[0059] Examples of diacyl peroxides include dilauroyl peroxide, dibenzoyl peroxide, and bis-3,5,5-trimethylhexanoyl peroxide.

[0060] Examples of hydroperoxides include 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide (for example, Kayacumene H manufactured by Kayaku Aguzo Co., Ltd.), and t-butyl hydroperoxide.

[0061] Examples of dialkyl peroxides include dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 1,3-bis(t-butylperoxyisopropyl)benzene, t-butylcumyl peroxide, di-t-butyl peroxide, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3.

[0062] Examples of peroxyketals include 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 1,1-di-t-butylperoxycyclohexane, and 2,2-di-t-butylperoxybutane.

[0063] Examples of peroxyesters include 1,1,3,3-tetramethylbutylperoxyneodecanoate, α-cumylperoxyneodecanoate, t-butylperoxyneodecanoate, t-butylperoxyneoheptanoate, t-butylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, t-amylperoxy 2-ethylhexanoate, t-butylperoxy 2-ethylhexanoate, di-t-butylperoxyhexahydroterephthalate, t-amylperoxy 3,5,5-trimethylhexanoate, t-butylperoxyacetate, t-butylperoxybenzoate, t-hexylperoxybenzoate, and t-amylperoxybenzoate.

[0064] Examples of peroxycarbonates include di-2-ethylhexyl peroxydicarbonate, diisopropyl peroxydicarbonate, t-butylperoxyisopropyl carbonate, t-butylperoxy 2-ethylhexyl carbonate, and 1,6-bis(t-butylperoxycarbonyloxy)hexane.

[0065] Commercially available products of component (D) include t-hexylperoxy-2-ethylhexanoate (Perhexyl (registered trademark) O) and t-butylperoxy-2-ethylhexanoate (Pertible (registered trademark) O), both of which are available from NOF Corporation. Component (D) may be one type or a combination of two or more types.

[0066] <Additional Ingredient (E)> The photocurable resin composition may contain, as necessary, an additional component (E) within the scope of not impairing the effects of the present invention. Examples of component (E) include an inorganic thixotropic agent, other photoinitiators, polymer components, silane coupling agents, surfactants, slip agents, polymerization inhibitors, photosensitizers, antioxidants, stabilizers, colorants, solvents, and fillers.

[0067] The thixotropic agent containing an inorganic substance is not particularly limited as long as it has a high thickening or thixotropic effect when added in a small amount. Examples of inorganic substances contained in the thixotropic agent include fumed silica, calcium carbonate, carbon black, kaolin, clay, activated clay, silica sand, silica stone, diatomaceous earth, anhydrous aluminum silicate, hydrated magnesium silicate, talc, perlite, white carbon, mica fine powder, bentonite, etc. Furthermore, the thixotropic agent may consist solely of an inorganic substance, or may be an inorganic substance surface-treated with a fatty acid and / or a resin acid.

[0068] The other photopolymerization initiator is a photopolymerization initiator other than component (B). Examples of other photopolymerization initiators include hydrogen abstraction-type radical photopolymerization initiators. Examples of hydrogen abstraction-type radical photopolymerization initiators include benzophenone-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, carbazole-phenone-based photopolymerization initiators, acridine-based photopolymerization initiators, triazine-based photopolymerization initiators, benzoyl-based photopolymerization initiators, oxime ester-based photopolymerization initiators, and camphorquinone-based photopolymerization initiators. The hydrogen abstraction-type radical photopolymerization initiator can be appropriately selected from known components.

[0069] Component (E) other than the above-mentioned components is not particularly limited as long as it is a component that is commonly used in photocurable resin compositions, and can be appropriately selected depending on the purpose. The photocurable resin composition preferably does not contain any other photopolymerization initiator. Component (E) may be one kind of component or a combination of two or more kinds of components.

[0070] (characteristic) The specific gravity of the photocurable resin composition is not particularly limited. From the viewpoint of being usable as a photocurable resin composition for a balance weight, the specific gravity of the photocurable resin composition is preferably 2.2 to 7.0, and particularly preferably 3.0 to 6.5. Here, the specific gravity of the photocurable resin composition can be measured according to JIS K 6833.

[0071] The viscosity of the photocurable resin composition at 25°C is not particularly limited. From the viewpoint of facilitating stable presence of the composition at the applied position and / or from the viewpoint of dispersibility of component (C), the viscosity of the photocurable resin composition at 25°C is preferably 100,000 mPa·s or less, more preferably 1,000 to 100,000 mPa·s, and particularly preferably 3,000 to 80,000 mPa·s. Here, the viscosity is a value measured using an E-type viscometer at atmospheric pressure at 25°C, with an appropriate cone plate and rotation speed selected.

[0072] (Content of each ingredient) In the photocurable resin composition, the content of each component is as follows.

[0073] The total content of components (A1) and (A2) per 100 parts by mass of component (A) is 26 parts by mass or more and 100 parts by mass or less. If the total content of components (A1) and (A2) per 100 parts by mass of component (A) is less than 26 parts by mass, deep section curing is poor. From the viewpoint of deep section curing, the total content of components (A1) and (A2) per 100 parts by mass of component (A) is preferably 50 to 100 parts by mass, and particularly preferably 70 to 100 parts by mass.

[0074] From the viewpoint of photocurability, the content of component (B) is preferably 0.5 to 10 parts by mass, more preferably 0.8 to 10 parts by mass, and particularly preferably 1.0 to 7.0 parts by mass, per 100 parts by mass of component (A).

[0075] The content of component (C) is preferably 70 to 1,000 parts by mass, more preferably 100 to less than 700 parts by mass, and particularly preferably 250 to 600 parts by mass, per 100 parts by mass of component (A). When the content of component (C) is within the above range per 100 parts by mass of component (A), the specific gravity of the photocurable resin composition tends to be efficiently increased. Furthermore, the fluidity and / or deep curability of the composition tends to be better.

[0076] The content of component (C) is preferably 10 to 90 parts by mass, and particularly preferably 20 to 88 parts by mass, per 100 parts by mass of the photocurable resin composition.

[0077] The content of component (D) is 1.3 parts by mass or more per 100 parts by mass of component (A). If the content of component (D) is less than 1.3 parts by mass per 100 parts by mass of component (A), deep section curing is poor. From the viewpoint of deep section curing, the content of component (D) is preferably 1.3 to 7.0 parts by mass, and particularly preferably 1.5 to 6.0 parts by mass per 100 parts by mass of component (A).

[0078] The total content of component (A), component (B), component (C), and component (D) relative to 100 parts by mass of the photocurable resin composition is preferably 55 parts by mass or more and 100 parts by mass or less, more preferably 70 parts by mass or more and 98 parts by mass or less, and particularly preferably 80 parts by mass or more and 97 parts by mass or less.

[0079] (Method for producing photocurable resin composition) The photocurable resin composition can be obtained by a production method including a step of mixing component (A), component (B), component (C), component (D), and optional component (E).

[0080] (Method for curing photocurable resin composition) The photocurable resin composition can be cured by irradiating it with energy rays. The energy rays are not particularly limited, and active energy rays such as visible light, ultraviolet light, X-rays, and electron beams can be used. The energy rays are preferably ultraviolet light. As a light source of ultraviolet light, a light source that emits ultraviolet light (UV) can be used. Examples of the ultraviolet light source include a metal halide lamp, a high-pressure mercury lamp, a xenon lamp, a mercury-xenon lamp, a halogen lamp, a pulse xenon lamp, and an LED. The cumulative light amount of the energy rays is, for example, 500 to 10,000 mJ / cm at 365 nm. 2 It is preferable that the concentration is 1,000 to 8,000 mJ / cm 2 In addition, the photocurable resin composition is particularly preferably, for example, 700 mW / cm 2 × 10 seconds or more of light irradiation or 700mW / cm 2 It may be cured by irradiating with light for 10 seconds or more at 500 mW / cm 2 ×10 seconds or more of light irradiation or 500mW / cm 2 The resin may be cured by irradiating the resin with light for 10 seconds or more.

[0081] [Application] The photocurable resin composition can be used as a photocurable resin composition for a balance weight. The photocurable resin composition for a balance weight is preferably a photocurable resin composition for a balance weight of a rotating body. The balance weight of a rotating body refers to a cured product of the photocurable resin composition present in an amount sufficient to offset the rotational imbalance of the rotating body.

[0082] Examples of rotating bodies include rotating disks in HDDs (hard disk drives), rotors for motors, rolling mill rolls, rotary tools, shafts for various machines, rotors for motors such as brushless outer rotor motors and brush motors, and polygon mirrors for laser printers.

[0083] When the photocurable resin composition is used as a photocurable resin composition for a balance weight, a rotating body including the balance weight can be manufactured. The manufacturing method of the rotating body including the balance weight can be, for example, the following steps: A step of applying a photocurable resin composition to a rotating body; and A step of curing the photocurable resin composition to form a balance weight. Includes.

[0084] In the step of applying the photocurable resin composition to the rotating body, the application location and application method of the photocurable resin composition can be appropriately determined depending on the shape of the target rotating body. In the step of forming the balance weight, the method of curing the photocurable resin composition is as described above.

[0085] In addition, for methods of manufacturing a rotating body including a balance weight, reference can be made to the descriptions in Japanese Patent Application Laid-Open Nos. 8-104705, 5-180273, 5-38092, 2001-37174, 2008-61354, and 2021-156413. [Example]

[0086] The present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. Values ​​in the tables are in parts by weight unless otherwise specified.

[0087] (Ingredients used) <Component (A): Radical polymerization reactive component> Component (A1): Polyfunctional (meth)acrylate EBECRYL3700: Bisphenol A epoxy acrylate (manufactured by Daicel Allnex, bifunctional) Component (A2): Monofunctional (meth)acrylate having a (meth)acrylamide group ACMO: Acrylic morpholine (morpholine acrylate) (KJ Chemical) HEAA: Hydroxyethyl acrylamide (KJ Chemical) Component (A3): Other radical polymerization reactive components IBOA: Isobornyl acrylate (manufactured by Nippon Shokubai) IB: Isobornyl methacrylate (Kyoeisha Chemical Co., Ltd.) <Component (B): Photopolymerization initiator> Omnirad 1173: Photoinitiator: 2-hydroxy-2-methylpropiophenone (manufactured by IGM Resins BV) Omnirad 819: Photoinitiator: Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by IGM Resins BV) <Component (C): Filler> BR12QZ: Zirconia filler (specific gravity: 5.7, manufactured by Daiichi Kigenso Kagaku Kogyo) GA-9: Glass filler (specific gravity: 5.8, manufactured by Nippon Electric Glass) WL: Tungsten filler (specific gravity 19.3, made by Nippon Shinkinzoku) BMH100: Barium sulfate filler (specific gravity: 4.5, manufactured by Sakai Chemical Industry Co., Ltd.) <Component (D): Organic peroxide> Perocta O: 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (NOF Corp.) <Ingredient (E): Other ingredients> TG-308F: Thixotropic agent (manufactured by Cabot Japan) Camphorquinone: Other photopolymerization initiators (manufactured by Fujifilm Wako Pure Chemical Industries)

[0088] [Method for producing photocurable resin composition] According to the compounding ratios shown in the table, the components were mixed in a flask equipped with a stirrer for 30 minutes to 1 hour until homogenous, and then air bubbles were removed using a Thinky vacuum stirrer / defoamer to obtain photocurable resin compositions of the examples and comparative examples.

[0089] [Evaluation conditions] (1) Acrylic equivalent of component (A1) and component (A2) The acrylic equivalent refers to the molecular weight per acryloyl group. In other words, it is the value obtained by dividing the molecular weight by the acryloyl group. For example, the acrylic equivalent of a trifunctional acrylate with a molecular weight of 298 is 99.3. The acrylic equivalent in a composition is the value obtained by multiplying the acrylic equivalent of each component contained in the composition by its blending ratio and adding the resulting values ​​together. For example, in the case of a radically polymerizable composition consisting of 50 parts by weight of component A (acrylic equivalent of 100) and 50 parts by weight of component B (acrylic equivalent of 400), the acrylic equivalent is 250. The acrylic equivalents of components (A1) and (A2) in the composition were determined by these calculations.

[0090] (2) Specific gravity of composition and filler The specific gravities of the composition and filler were measured by the JIS K6833 specific gravity cup method.

[0091] (3) Deep hardening A silicone rubber sheet (10 mm long x 10 mm wide x 1 mm high) manufactured by AS ONE Corporation with a 5 mm diameter hole was attached to a black plastic (PBT (polybutylene terephthalate) Duranex 3015 black manufactured by Polyplastics Corporation, 15 mm long x 150 mm wide x 3 mm high), and the hole was filled with a liquid (composition). The liquid was then scraped off to make it flat. The silicone rubber sheet was then removed and immediately irradiated with 700 mW / cm using a UV irradiator (LC-8 (L9588-01) manufactured by Hamamatsu Photonics K.K.). 2 ×10 seconds or 500mW / cm 2 The cured product was then irradiated for 10 seconds to form a cured product. The cured product was peeled off from the PBT, and it was confirmed whether it had cured up to the PBT interface (to a depth of 1 mm) (whether there was any liquid). If it had cured to a depth of 1 mm, it was considered "cured." If it had not cured to a depth of 1 mm, it was considered "uncured."

[0092] The results are shown in the table below. All values ​​for the amount of each component are in parts by mass. "-" indicates that the value was not measured.

[0093] [Table 1]

[0094] [Table 2]

[0095] [Table 3]

[0096] From Tables 1 and 2, the photocurable resin compositions of the examples have a light output of 700 mW / cm 2 By irradiation with energy rays for 10 seconds, curing was achieved to a depth of 1 mm, demonstrating excellent deep curing properties. 2 ), the photocurable resin composition was cured to a depth of 1 mm, demonstrating excellent deep curing properties. 3 As described above, it can be said that the photocurable resin composition can be used as a balance weight.

[0097] Comparison of Example 1 with Examples 6 to 8 and 12 shows that when component (A) contained component (A2), deep curing was superior. Comparing Examples 1 and 9 with Example 11, when component (C) was barium sulfate filler, the deep curing properties were superior. A comparison between Example 6 and Example 11 shows that when the specific gravity of component (C) was high, the specific gravity of the composition was efficiently increased. A comparison between Example 6 and Example 10 shows that when component (C) was a metal oxide filler or other inorganic filler, the deep curing properties were superior compared to when it was a metal filler.

[0098] The compositions of Comparative Examples 1, 6, and 7 do not contain component (D). The composition of Comparative Example 2 contains less than 1.3 parts by mass of component (D). The composition of Comparative Example 3 contains less than 26 parts by mass of the total of components (A1) and (A2) per 100 parts by mass of component (A). The composition of Comparative Example 4 does not contain component (C) but contains another photopolymerization initiator (i.e., a hydrogen abstraction photopolymerization initiator). The composition of Comparative Example 5 does not contain either component (A1) or component (A2). The compositions of Comparative Examples 1 to 7 have a luminance of 700 mW / cm 2 The composition did not cure after 10 seconds of energy ray irradiation, and the deep curing property was poor.

Claims

1. A photocurable resin composition comprising a radical polymerization reactive component (A), a photopolymerization initiator (B), a filler (C), and an organic peroxide (D), The component (A) contains a polyfunctional (meth)acrylate (A1) and / or a monofunctional (meth)acrylate having a (meth)acrylamide group (A2), Component (B) is an intramolecular cleavage-type photoradical polymerization initiator, Component (C) has a specific gravity of 4.0 or more, the total content of component (A1) and component (A2) is 26 parts by mass or more and 100 parts by mass or less relative to 100 parts by mass of component (A), The content of component (D) is 1.3 parts by mass or more relative to 100 parts by mass of component (A). Photocurable resin composition.

2. 2. The photocurable resin composition according to claim 1, wherein the acrylic equivalent of component (A1) and component (A2) contained in component (A) is 1,000 g / eq or less.

3. 2. The photocurable resin composition according to claim 1, wherein the content of component (C) is 70 parts by mass or more and 1,000 parts by mass or less per 100 parts by mass of component (A).

4. The photocurable resin composition according to any one of claims 1 to 3, which is used for a balance weight of a rotating body.

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