Photocurable resin composition

Abstract

To provide a resin composition which can be cured to a deep part by irradiation with an active energy ray and has a high specific gravity.SOLUTION: The present invention relates to a liquid photocurable resin composition containing a radical polymerization reactive component (A), a photopolymerization initiator (B), and a filler (C). The component (C) has a specific gravity of 3.0 or more and a refractive index of 1.80 or less. The content of the component (C) is 70 pts.mass or more and 1,000 pts.mass or less based on 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, a lot of vibration will occur during rotation. One method for achieving this balance is to attach a resin composition for balance adjustment as a weight to achieve weight balance.

[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. Furthermore, if the proportion of filler (powder) in the composition is increased to increase the specific gravity of the composition, the composition may lose its fluidity (become extremely viscous), which may reduce workability or make application itself difficult.

[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 and has a high specific gravity. [Means for solving the problem]

[0007] The present invention relates to the following: [1] A liquid photocurable resin composition comprising a radical polymerization reactive component (A), a photopolymerization initiator (B), and a filler (C), Component (C) has a specific gravity of 3.0 or more and a refractive index of 1.80 or less, A photocurable resin composition, 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). [2] The photocurable resin composition according to [1], which has a viscosity at 25°C of 1,000 to 100,000 mPa·s. [3] The photocurable resin composition according to [1] or [2], wherein the component (C) is at least one selected from the group consisting of barium sulfate, alumina, glass, and barium carbonate. [4] The component (A) is one or more selected from the group consisting of monofunctional radical-polymerization-reactive monomers (A1) having a cyclic structure containing no one or more atoms selected from O and N, and monofunctional radical-polymerization-reactive monomers (A2) having a heterocyclic structure containing O and / or N, The photocurable resin composition according to any one of [1] to [3], further comprising a difunctional or higher functional radical polymerization reactive component (A3). [5] The photocurable resin composition of any one of [1] to [4], wherein the content of component (C) is 20 to 85 parts by mass per 100 parts by mass of the photocurable resin composition. [6] The photocurable resin composition according to any one of [1] to [5], 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 and has a high specific gravity. 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 "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 is a liquid photocurable resin composition containing a radical polymerization reactive component (A), a photopolymerization initiator (B), and a filler (C), wherein the component (C) has a specific gravity of 3.0 or more and a refractive index of 1.80 or less, and the content of the component (C) is 70 parts by mass or more and 1,000 parts by mass or less per 100 parts by mass of the component (A).

[0011] The photocurable resin composition can be cured to a deep portion by irradiation with energy rays. That is, the photocurable resin composition has deep curing properties. Therefore, it is possible to reduce the influence of remaining uncured resin composition on surrounding components. Furthermore, the photocurable resin composition has a high specific gravity. Therefore, it is possible to efficiently adjust the rotation balance of the rotating body.

[0012] <Radical polymerization reactive component (A)> The radical polymerization reactive component (A) is not particularly limited as long as it has a radical polymerization reactive functional group, and examples thereof include a radical polymerization reactive oligomer and a radical polymerization reactive monomer. The radical polymerization reactive functional group is not particularly limited as long as it is a group containing an unsaturated double bond, but an alkenyl group (e.g., a vinyl group, an allyl group, etc.) or a (meth)acryloyl group is preferred, and a (meth)acryloyl group is particularly preferred. Component (A) may consist solely of a radical polymerization reactive monomer, or may be a mixture of a radical polymerization reactive monomer and a radical polymerization reactive oligomer.

[0013] In component (A), the weight-average molecular weight of the radical polymerization reactive oligomer is preferably 1,500 or more, and particularly preferably 1,500 to 50,000. As a method for measuring the weight-average molecular weight, for components with relatively high molecular weights such as oligomers and polymers, a method of converting the measurement results of gel permeation chromatography (GPC) using a calibration curve of standard polystyrene is generally known. In addition, since monomers do not have a molecular weight distribution, they can be determined from the structural formula.

[0014] The radical polymerization reactive monomer preferably has 1 radical polymerization reactive functional group. That is, the radical polymerization reactive monomer is preferably a monofunctional monomer, and particularly preferably a monofunctional (meth)acrylate monomer.

[0015] Examples of the radical polymerization reactive component (A) include a monofunctional radical polymerization reactive monomer (A1) having a cyclic structure containing no atom selected from O and N, a monofunctional radical polymerization reactive monomer (A2) having a heterocyclic structure containing O and / or N, a polyfunctional radical polymerization reactive component (A3), and a radical polymerization reactive component (A4) other than components (A1) to (A3).

[0016] <<A monofunctional radical polymerization reactive monomer (A1) having a cyclic structure containing no atom selected from O and N>> Component (A1) is a monofunctional radical polymerization reactive monomer having a cyclic structure containing no atom selected from O and N. The cyclic structure may be a monocyclic or polycyclic structure. The cyclic structure may be an alicyclic structure or an aromatic ring structure. The total number of atoms constituting one alicyclic structure is not particularly limited, but is preferably 3 to 20. The total number of atoms constituting one aromatic ring structure is not particularly limited, but is preferably 6 to 20. The cyclic structure preferably consists only of carbon atoms. Component (A1) is preferably an alicyclic (meth)acrylate monomer or an aromatic (meth)acrylate monomer.

[0017] Examples of the alicyclic (meth)acrylate monomer include isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyl oxyethyl (meth)acrylate, norbornene (meth)acrylate, cyclohexyl (meth)acrylate, and the like.

[0018] Examples of the aromatic (meth)acrylate monomer include benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, ethoxylated o-phenylphenol acrylate, phenoxybenzyl (meth)acrylate, phenylphenol ethyloxy (meth)acrylate, naphthalene (meth)acrylate, and the like.

[0019] Component (A1) may be one kind or a combination of two or more kinds.

[0020] <<Mono-functional radical polymerization reactive monomer (A2) having a hetero ring structure containing O and / or N>> Component (A2) is a compound having a radical polymerization reactive group and a hetero ring structure containing O and / or N. The hetero ring structure of component (A2) has one or more selected from the group consisting of an oxygen atom and a nitrogen atom as hetero atoms constituting the ring structure.

[0021] When the hetero ring structure contains an oxygen atom, the number of oxygen atoms in the ring hetero structure is preferably 1 to 3, and particularly preferably 1 to 2. When the hetero ring structure contains a nitrogen atom, the number of nitrogen atoms in the hetero ring structure is preferably 1 to 2, and particularly preferably 1. When the hetero ring structure contains both an oxygen atom and a nitrogen atom, the total number of oxygen atoms and nitrogen atoms in the hetero ring structure is preferably 2 to 4, and particularly preferably 2 to 3.

[0022] The heterocyclic structure may be a monocyclic or polycyclic ring. The total number of atoms constituting one heterocyclic structure is not particularly limited, but is preferably 3 to 20. The heterocyclic structure is preferably a 5- or 6-membered monocyclic heterocyclic structure. Examples of heterocyclic structures include morpholine, furan, tetrahydrofuran, dioxane, pyrrolidine, piperidine, piperazine, pyrrolidone, and maleimide.

[0023] The total number of heterocyclic structures contained in component (A2) is preferably 1 to 3, and particularly preferably 1 or 2. When the heterocyclic structures are polycyclic structures, the number of such polycyclic structures is counted as 1. Component (A2) is preferably a (meth)acrylate monomer having a (meth)acryloyl group.

[0024] Specific examples of component (A2) include tetrahydrofurfuryl (meth)acrylate, alkoxylated tetrahydrofurfuryl acrylate caprolactone-modified tetrahydrofurfuryl (meth)acrylate, morpholine (meth)acrylate (also called 4-(meth)acryloylmorpholine, etc.), pentamethylpiperidinyl (meth)acrylate, and cyclic trimethylolpropane formal (meth)acrylate.

[0025] Component (A2) may be one type or a combination of two or more types.

[0026] <<Difunctional or higher functional radical polymerization reactive component (A3)>> Examples of the difunctional or higher radical polymerization reactive component (A3) include difunctional or higher radical polymerization reactive oligomers and difunctional or higher radical polymerization reactive monomers. The difunctional or higher radical polymerization reactive oligomer is an oligomer having two or more radical polymerization reactive groups in the molecule. Examples of the difunctional or higher radical polymerization reactive oligomer include (meth)acrylate oligomers having two or more (meth)acryloyl groups in the molecule, and preferred (meth)acrylate oligomers include urethane (meth)acrylate oligomers and epoxy (meth)acrylate oligomers.

[0027] The urethane (meth)acrylate oligomer may be an aromatic, aliphatic, polyether, polycarbonate, polyester, or combination thereof. Commercially available urethane (meth)acrylate oligomers include those described in the examples, as well as EBECRYL4858 (manufactured by Daicel-Allnex Corporation), UN-2301 (manufactured by Negami Chemical Industry Co., Ltd.), EBECRYL4859 (manufactured by Daicel-Allnex Corporation), and EBECRYL4738 (manufactured by Daicel-Allnex Corporation).

[0028] Epoxy (meth)acrylate oligomers are oligomers in which all epoxy groups in an epoxy resin have reacted with (meth)acrylic acid. Epoxy (meth)acrylate oligomers may also include oligomers in which some of the epoxy groups in an epoxy resin have reacted with (meth)acrylic acid, i.e., oligomers containing epoxy groups and (meth)acryloyl groups in the resin. Examples of epoxy resins include aromatic epoxy resins, aliphatic epoxy resins, alicyclic epoxy resins, and other epoxy resins. Commercially available epoxy (meth)acrylate oligomers include EB3700 (manufactured by Daicel-Allnex) and EB3708 (manufactured by Daicel-Allnex).

[0029] The (meth)acrylate oligomer may have 2 to 6 (meth)acryloyl groups, or may have 2 to 4 (meth)acryloyl groups.

[0030] A difunctional or higher functional radical polymerization reactive monomer is a monomer having two or more radical polymerization reactive groups in the molecule. Examples of difunctional or higher functional radical polymerization reactive monomers include ethoxylated bisphenol A di(meth)acrylate and modified bisphenol A di(meth)acrylate.

[0031] Component (A3) may be one type or a combination of two or more types. For example, component (A3) may consist solely of one or more difunctional or higher radical polymerization reactive oligomers or difunctional or higher radical polymerization reactive monomers. Component (A3) may also be a combination of one or more difunctional or higher radical polymerization reactive oligomers and one or more difunctional or higher radical polymerization reactive monomers.

[0032] <<Radical Polymerization Reactive Component (A4) Other than Components (A1) to (A3)>> The radical polymerization reactive component (A4) other than the components (A1) to (A3) may be a monofunctional radical polymerization reactive component having no cyclic structure. The component (A4) is preferably a (meth)acrylate monomer or oligomer having a (meth)acryloyl group.

[0033] Examples of the (meth)acrylate monomer that is component (A4) include alkyl (meth)acrylate monomers, hydroxyalkyl (meth)acrylates, and (meth)acrylates of (poly)alkylene glycol monoalkyl ethers.

[0034] Examples of the alkyl(meth)acrylate monomer include methyl(meth)acrylate, ethyl(meth)acrylate, tert-butyl(meth)acrylate, isooctyl(meth)acrylate, isomyristyl(meth)acrylate, and lauryl(meth)acrylate.

[0035] Examples of hydroxyalkyl (meth)acrylates include hydroxyethyl (meth)acrylate (e.g., 2-hydroxyethyl (meth)acrylate), hydroxypropyl (meth)acrylate (e.g., 2-hydroxypropyl (meth)acrylate), hydroxybutyl (meth)acrylate (e.g., 4-hydroxybutyl (meth)acrylate), and diethylene glycol monoethyl ether (meth)acrylate.

[0036] Examples of (meth)acrylate monomers of (poly)alkylene glycol monoalkyl ethers include alkoxyethyl (meth)acrylate, alkoxypropyl (meth)acrylate, alkoxybutyl (meth)acrylate, and polymers of these alkylene glycols (e.g., methoxytriethyleneoxyethyl (meth)acrylate), etc. Here, the number of carbon atoms in the alkyl group, alkoxy group, and alkylene group is preferably 1 to 6.

[0037] The (meth)acrylate oligomer of component (A4) is not particularly limited as long as it has one (meth)acryloyl group in the molecule. The (meth)acrylate oligomer of component (A4) is the same as that described above for component (A3), except that the number of (meth)acryloyl groups in the molecule is one.

[0038] Component (A4) may be a combination of one or more types, such as a combination of one or more (meth)acrylate monomers and one or more (meth)acrylate oligomers.

[0039] <<Preferred Embodiments of Component (A)>> Component (A) preferably contains one or two selected from the group consisting of components (A1) and (A2) and component (A3). In this case, component (A) may or may not contain component (A4).

[0040] <Photopolymerization initiator (B)> The photopolymerization initiator (B) is not particularly limited as long as it is a compound that generates radicals upon irradiation with energy rays. Component (B) includes 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, benzophenone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone-1,2-hydroxy-2-methyl Oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone], Oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone], Benzoin methyl ether, Benzoin ethyl ether, Benzoin isobutyl ether, Benzoin isopropyl ether, Bis(2,4,6-trimethylbenzoyl)phenylphosphine Oxide, oligo 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanol, oligo 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanol, 2-hydroxy-2-methyl-1-phenyl-1-propanone, isopropyl thioxanthone, methyl o-benzoylbenzoate, [4-(methylphenylthio)phenyl]phenylmethane, 2,4-diethyl thioxanthone, 2-chlorothioxanthone, benzophenone, ethyl anthraquinone, benzophenone anthraquinone monium salt, thioxanthone ammonium salt, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, 2,4,6-trimethylbenzophenone, 4-methylbenzophenone, 4,4'-bisdiethylaminobenzophenone, 1,4-dibenzoylbenzene, 10-butyl-2-chloroacridone, 2,2'-bis(o-chlorophenyl)-4,5,4',5'-tetrakis(3,4,5-trimethoxyphenyl)1,2'-biimidazole, 2,2'bis(o-chlorophenyl)4,5,4',5'-tetraphenyl-1,2'-biimidazole, 4-benzoyldiphenyl ether, acrylated benzophenone, bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium, o-methylbenzoyl benzoate, p-dimethylaminobenzoic acid ethyl ester, p-dimethylaminobenzoic acid isoamyl ethyl ester, activated tertiary amine, carbazole-phenone photopolymerization initiator, acridine photopolymerization initiator, triazine photopolymerization initiator, benzoyl photopolymerization initiator, etc.

[0041] Commercially available products of component (B) include KIP-150 manufactured by DKSH Japan, the Omnirad® series such as Omnirad184, Omnirad819, Omnirad127, and Omnirad1173, all manufactured by IGM Resins BV, the Darocur® series such as Darocur1173, the Lucirin® series such as Lucirin TPO, and ESACURE 1001M manufactured by ESACUR Nippon SiberHegner AG. Omnirad1173 and Omnirad184 are preferred from the viewpoint of reducing susceptibility to oxygen inhibition, which can cause non-curing in the radical reaction of component (A). Component (B) may be one type or a combination of two or more types.

[0042] <Filler (C)> The photocurable resin composition contains a filler (C) having a specific gravity of 3.0 or more and a refractive index of 1.80 or less. If the specific gravity of the filler is less than 3.0, 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. If the refractive index of component (C) exceeds 1.80, deep curing properties tend to be poor. From the viewpoints 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 3.0 or more and 10.0 or less, and particularly preferably 3.0 or more and 8.0 or less. From the viewpoint of excellent deep curing properties, the refractive index of component (C) is preferably 1.40 or more and 1.80 or less, and particularly preferably 1.50 or more and 1.80 or less.

[0043] The refractive index of component (C) is the refractive index for light with a wavelength of 589 nm, and can be measured in accordance with JIS K 7142, Method B. The specific gravity of component (C) can be measured in accordance with JIS K 6833.

[0044] Specific examples of component (C) include barium sulfate, alumina, glass, magnesium oxide, strontium carbonate, barium carbonate, potassium iodide, etc. Component (C) is preferably one or more selected from the group consisting of barium sulfate, alumina, glass, and barium carbonate.

[0045] 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 refers to the median size (D50).

[0046] 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.

[0047] Component (C) may be one type or a combination of two or more types.

[0048] <Additional Ingredient (D)> The photocurable resin composition may further contain a component (D) as needed, provided that the effects of the present invention are not impaired. Examples of component (D) include an inorganic thixotropic agent, a polymer component, a silane coupling agent, a surfactant, a slip agent, a polymerization inhibitor, a photosensitizer, an antioxidant, a stabilizer, a colorant, a solvent, and a filler.

[0049] 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.

[0050] Component (D) 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. Component (D) may be one kind of component or a combination of two or more kinds of components.

[0051] (characteristic) The photocurable resin composition is liquid. Here, "liquid" means that it has fluidity at 25°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. When the viscosity of the photocurable resin composition at 25°C is 1,000 to 100,000 mPa·s, the liquid tends to remain stable at the applied position. Furthermore, when the viscosity is within this range, the dispersibility of the filler (C) in the photocurable resin composition tends to be good. Here, the viscosity is measured using an E-type viscometer at atmospheric pressure at 25°C, selecting an appropriate cone plate and rotation speed.

[0052] (Content of each ingredient) In the photocurable resin composition, the content of each component is as follows.

[0053] From the viewpoint of the viscosity of the photocurable resin composition, the total content of components (A1) and (A2) is preferably less than 100 parts by mass, and particularly preferably 40 parts by mass or more and 80 parts by mass or less, per 100 parts by mass of component (A). From the viewpoint of imparting properties such as adhesion to the photocurable resin composition, the content of component (A3) is preferably less than 100 parts by mass, and particularly preferably 20 parts by mass or more and 60 parts by mass or less, per 100 parts by mass of component (A).

[0054] 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).

[0055] The content of component (C) is 70 to 1,000 parts by mass per 100 parts by mass of component (A). If the content of component (C) is less than 70 parts by mass per 100 parts by mass of component (A), the specific gravity of the photocurable resin composition tends to be low. If the content of component (C) is more than 1,000 parts by mass per 100 parts by mass of component (A), the fluidity and / or deep curing properties of the composition tend to be poor. The content of component (C) is more preferably 100 to 700 parts by mass per 100 parts by mass of component (A), and particularly preferably 250 to 600 parts by mass per 100 parts by mass of component (A).

[0056] The content of component (C) is preferably 10 to 90 parts by mass, and particularly preferably 20 to 85 parts by mass, per 100 parts by mass of the photocurable resin composition.

[0057] The total content of component (A), component (B), and component (C) 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.

[0058] (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), and any further optional component.

[0059] (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 It is particularly preferred that:

[0060] [Application] Because the photocurable resin composition has a high specific gravity, it 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 imbalance in rotation of the rotating body.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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]

[0065] 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.

[0066] (Ingredients used) <Component (A): Radical polymerization reactive component> EBECRYL3700: Bisphenol A epoxy acrylate (manufactured by Daicel Allnex) TE2000: Urethane methacrylate (manufactured by Nippon Soda) UN-9000PEP: Urethane acrylate (manufactured by Negami Industrial Co., Ltd.) IBOA: Isobornyl acrylate (manufactured by Nippon Shokubai) ACMO: Acrylic morpholine (morpholine acrylate) (KJ Chemical) <Component (B): Photopolymerization initiator> Omnirad 1173: Photoinitiator: 2-hydroxy-2-methyl-1-phenyl-propan-1-one (manufactured by IGM Resins BV) <Component (C): Filler> CY0037M1: Glass filler (specific gravity: 3.7, refractive index: 1.65, manufactured by Takara Standard) AA-18: Alumina filler (specific gravity: 3.9, refractive index: 1.76, manufactured by Sumitomo Chemical) BMH100: Barium sulfate filler (specific gravity: 4.5, refractive index: 1.64, manufactured by Sakai Chemical Industry Co., Ltd.) <Component (C'): Other fillers> CF0093-R01: Glass filler (specific gravity: 2.4, refractive index: 1.50, manufactured by Takara Standard) GA-9: Glass filler (specific gravity: 5.8, refractive index: 1.87, manufactured by Nippon Electric Glass) BR12QZ: Zirconia filler (specific gravity: 5.7, refractive index: 2.10, manufactured by Daiichi Kigenso Kagaku Kogyo) <Ingredient (D): Other ingredients> TG-308F: Thixotropic agent (manufactured by Cabot Japan)

[0067] [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.

[0068] [Evaluation conditions] (1) Fluidity, viscosity The flowability of the photocurable resin composition was evaluated by visually inspecting the composition immediately after preparation and measuring its viscosity. The viscosity of the composition was measured at 25°C using an E-type viscometer (RE-125U manufactured by Toki Sangyo Co., Ltd., 25±1°C). The flowability was evaluated according to the following criteria. Good (fluid): Viscosity is 100,000 mPa·s or less. × (No fluidity): Viscosity exceeds 100,000 mPa·s, viscosity is too high to measure, or powdery matter is included, resulting in poor fluidity.

[0069] (3) Specific gravity of the composition The specific gravity of the composition was measured by the specific gravity cup method according to JIS K6833. Whether or not the composition had a high specific gravity was determined according to the following criteria. 〇 (High specific gravity): Specific gravity is 2.2 g / cm 3 That's all. × (Not high specific gravity): Specific gravity is 2.2 g / cm3 is less than.

[0070] (4) Deep hardening (1) 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 Duranex 3015 black manufactured by Polyplastics Co., Ltd., 15 mm long x 150 mm wide x 3 mm high), and the hole was filled with a liquid (composition) and scraped to make the liquid flat. Thereafter, the sheet was irradiated with 600 mW / cm using a UV irradiator (LC-8 (L9588-01) manufactured by Hamamatsu Photonics K.K.). 2 The cured product was peeled off from the PBT, and it was confirmed whether or not the curing had reached the PBT interface (whether or not there was any liquid). 〇: Hardened to a depth of 1 mm ×: Not cured to a depth of 1 mm

[0071] (5) Deep hardening (2) The liquid (composition) was filled into a black tube with an inner diameter of 5 mm and a height of 5 mm. The liquid was irradiated at 600 mW / cm using a UV irradiator (LC-8 (L9588-01) manufactured by Hamamatsu Photonics). 2 The curing depth was measured using a micrometer.

[0072] (6) Refractive index of filler The refractive index of the filler was measured by JIS K7142, Method B (immersion method using a microscope (Becke line method)). When catalog values ​​were available, those were used.

[0073] (7) Specific gravity of filler The specific gravity of the filler was measured using the JIS K6833 specific gravity cup method. When catalog values ​​were available, these were used.

[0074] The results are shown in the table below, where the amounts of each component are all in parts by mass.

[0075] [Table 1]

[0076] [Table 2]

[0077] As can be seen from Tables 1 and 2, the photocurable resin compositions of the Examples were excellent in appearance and fluidity, and in deep curing. In addition, the photocurable resin compositions had a specific gravity of 2.2 g / cm 3 As described above, the photocurable resin composition can be used as a balance weight.

[0078] Comparing Example 2 with Example 8, and comparing Example 3 with Example 4, it was found that the specific gravity of the composition increased when the content of component (C) increased relative to 100 parts by mass of the total of components (A) to (C). A comparison between Example 2 and Example 7 shows that when component (A) contained component (A2), deep curing was superior, but viscosity tended to increase. Comparison with Examples 1 to 3 showed that when component (C) was barium sulfate, the composition had a high specific gravity and was excellent in deep curing properties.

[0079] On the other hand, the compositions of Comparative Examples 1 to 3 contain a glass filler with a specific gravity of less than 3.0. The compositions of Comparative Examples 1 and 2 were poor in fluidity. The composition of Comparative Example 3 had fluidity but a low specific gravity. The compositions of Comparative Examples 4 to 6 contained a glass filler with a refractive index exceeding 1.80.The compositions of Comparative Examples 4 to 6 were poor in deep curability. The composition of Comparative Example 7 contained less than 70 parts by mass of component (C) per 100 parts by mass of component (A). The composition of Comparative Example 7 had poor deep section curability.

Claims

1. A liquid photocurable resin composition comprising a radical polymerization reactive component (A), a photopolymerization initiator (B), and a filler (C), Component (C) has a specific gravity of 3.0 or more and a refractive index of 1.80 or less, A photocurable resin composition, 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).

2. 2. The photocurable resin composition according to claim 1, having a viscosity at 25°C of 1,000 to 100,000 mPa·s.

3. 2. The photocurable resin composition according to claim 1, wherein the component (C) is at least one selected from the group consisting of barium sulfate, alumina, glass, and barium carbonate.

4. The component (A) comprises one or more monomers selected from the group consisting of monofunctional radical-polymerization-reactive monomers (A1) having a cyclic structure not containing one or more atoms selected from O and N, and monofunctional radical-polymerization-reactive monomers (A2) having a heterocyclic structure containing O and / or N, The photocurable resin composition according to claim 1, further comprising a difunctional or higher functional radical polymerization reactive component (A3).

5. 2. The photocurable resin composition according to claim 1, wherein the content of component (C) is 20 to 85 parts by mass per 100 parts by mass of the photocurable resin composition.

6. The photocurable resin composition according to any one of claims 1 to 5, which is used for a balance weight of a rotating body.

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