JPH08109231A - Actinic-radiation-curing resin composition for adjusting balance of rotor of motor or the like and rotor corrected in balance therewith - Google Patents

Abstract

PURPOSE: To obtain an actinic-radiation-curing composition which can give a motor rotor with an a accurately adjusted balance in good productivity by simple short-time irradiation by using a specified actinic-radiation-curing resin. CONSTITUTION: This composition comprises an actinic-radiation-curing compound having at least one ethylenic unsaturation in the molecule, a free radical photopolymerization initiator and/or a cationic photopolymerization initiator or comprises an actinic-radiation-curing compound having at least one epoxy group in the molecule and a cationic photopolymerization initiator. The above compounds may each have at least two bonded halogen atoms, desirably bromine atoms. These compounds having bromine atoms may be used in combination.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy ray-curable resin composition for balancing rotors of motors and a rotor whose balance is corrected using the same. More specifically, the rotor balancing energy is characterized by applying a resin composition containing an energy ray-curable resin to a rotor, irradiating radiation or visible light to form a cured film, and correcting the rotor balance. The present invention relates to a wire-curable resin composition and a rotor whose balance is corrected using the same.

[0002]

2. Description of the Related Art Motors, especially small precision motors,
In addition to constantly rotating at a constant speed, smooth and stable rotation without unevenness in rotation is required. For that purpose, the rotors of the motors must be in a state of being dynamically balanced with respect to the rotating shaft, that is, in a state of being rotationally balanced. In order to achieve this rotation balance, conventionally, a method of applying a paste or putty-like two-component epoxy resin composition to the coil ends of the rotor and then heating it to form a cured film has been used. However, the method of using a two-component thermosetting resin is complicated in handling such as the need to mix a paste-like or putty-like extremely high-viscosity main agent and a curing agent in a predetermined ratio, and before curing. In addition, there is a defect that the coating becomes non-uniform due to a decrease in viscosity due to heating.

[0003]

As a method for solving the above-mentioned problems of the prior art, a method of using a one-pack type thermosetting epoxy resin composition imparting thixotropic property (JP-A-63-92639). No.) is proposed. However, this method requires a heating furnace for heating after coating the resin in order to form a cured film, which consumes a large amount of heat energy, or when curing at room temperature, it takes a long time before curing. There are problems such as the need for time and poor storage stability of the resin.

[0004]

In order to solve the above problems, the present inventors have earnestly studied, and as a result, after applying a curable resin composition containing a specific energy ray curable resin to a rotor, It has been found that the balance of the rotor can be corrected efficiently by irradiating with energy rays such as radiation or visible rays. The present invention has been completed based on this finding. That is, the present invention includes (1) an active energy ray-curable compound (A) having one or more ethylenically unsaturated double bonds in one molecule, a photoradical polymerization initiator (C) and / or a photocation. An active energy ray-curable resin composition for balancing rotors of motors, which comprises a polymerization initiator (D). (2) The active energy ray-curable resin composition for balancing a motor rotor according to (1) above, wherein the compound (A) is an active energy ray-curable compound having two or more bromine atoms in its molecule. ) An active energy ray-curable resin composition for balancing a rotor of a motor, comprising an active energy ray-curable compound (B) having one or more epoxy groups in one molecule and a photocationic polymerization initiator (D), 4) The active energy ray-curable resin composition for balancing a motor rotor of the above (3), wherein the compound (B) is an active energy ray-curable compound having two or more bromine atoms in the molecule, (5) Active energy ray-curable compound (a) having two or more bromine atoms and one or more ethylenically unsaturated double bond in one molecule, and / or activity having two or more bromine atoms in one molecule Enel -Active energy ray-curable resin composition for balancing rotors of motors, which contains a ray-curable epoxy compound (b) and a photoradical initiator (C) and / or a photocationic initiator (D), (6) The balance activity of the motor rotor according to any one of (1) to (5) above, wherein the resin composition has a specific gravity of 1.4 (25 ° C) or more and a viscosity of 1,000 poise (25 ° C) or less. An energy ray curable resin composition, (7) An active energy ray curable resin composition for balancing a motor rotor according to any one of (1) to (6) above, which contains an inorganic filler (E). (8) A motor type rotor to which the active energy ray-curable resin composition according to any one of (1) to (7) is attached. Regarding

In the present invention, the energy rays are not particularly limited, and examples thereof include radiation such as X-rays and gamma rays, ultraviolet rays such as deep ultraviolet rays and near ultraviolet rays, and visible rays. Examples of the energy ray-curable compound (A) having one or more ethylenically unsaturated double bonds in one molecule used in the present invention include acrylamides, (meth) acrylate monomers, triallyl isocyanurate, and trimethylol. Compounds having an allyl group such as propane di (tri) allyl ether, pentaerythritol tri (tetra) allyl ether, diallyl phthalate, N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylcarbazole, divinylbenzene, styrene, diethylene glycol divinyl ether And a compound having a vinyl group such as bisphenol A diethyl vinyl ether. In addition, by reaction of epoxy (meth) acrylates or polyhydric alcohols and polybasic acids obtained by the reaction of bisphenol type or novolac type aromatic epoxy resin or aliphatic epoxy resin with (meth) acrylic acid. Polyester (meth) obtained by reaction of the obtained polyester polyol and (meth) acrylic acid
Examples thereof include acrylates, urethane polyols (meth) acrylates obtained by reacting polyether polyols, polyester polyols, caprolactone polyols, polycarbonate polyols, etc. with organic polyisocyanates and hydroxy (meth) acrylate compounds. These compounds can be used in combination of two or more, if necessary.

Examples of acrylamides include N-methyl (meth) acrylamide and N-methoxymethyl acrylate. Examples of the (meth) acrylate monomers include glycidyl (meth)
Acrylate, Acroylmorpholine, Hydroxyethyl (meth) acrylate, Hydroxypropyl (meth)
Acrylate, phenoxyethyl acrylate, tetrahydrofurfuryl (meth) acrylate, acryloylmorpholine, dimethylaminoethyl (meth) acrylate
, Tricyclodecane (meth) acrylate, dicyclopentadieneoxyethyl (meth) acrylate, isobornyl (meth) acrylate, 2,2-bis (4- (meth) acryloyloxyethoxyphenyl) propane, 2,2-bis (4-) (Meth) acryloyloxyethoxyphenyl) methane, neopentyl glycol di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, tricyclodecane dimethylol di (meth) acrylate dioxane glycol di (meth) acrylate, penta Erythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate , It can be exemplified dipentaerythritol hexa (meth) acrylate, dipentaerythritol Roh poly (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate.

The energy ray-curable compound (A) having one or more ethylenically unsaturated double bonds in one molecule used in the present invention has two or more halogen atoms bonded in the molecule. Good. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like, and a bromine atom is preferable. Examples of the energy ray-curable compound (a) having two or more bromine atoms and one or more ethylenically unsaturated double bonds in one molecule include dibromoneopentyl glycol di (meth) acrylate,
2,4,6-Tribromophenyl (meth) acrylate, 2- (2,4,6-tribromophenoxy) ethyl (meth) acrylate, ethylene oxide modified tetrabromobisphenol A diacrylate (New Frontier BR-42, No. Ichikogyo Seiyaku Co., Ltd.), ethylene oxide modified tetrabromobisphenol A dimethacrylate (New Frontier BR-42M, Daiichi Kogyo Seiyaku Co., Ltd.) and the like. Also, dibromophenyl glycidyl ether, dibromo neopentyl glycol diglycidyl ether, epoxidized di (tri) bromophenol, epoxidized di (tri) bromocresol, epoxidized brominated phenol novolac, epoxidized tetrabromobisphenol A, etc. And an epoxy (meth) acrylate which is a reaction product of the epoxy compound of (1) and (meth) acrylic acid. These compounds having two or more bromine atoms and one or more ethylenically unsaturated double bonds in one molecule can be used alone or in combination of two or more at an arbitrary ratio, if necessary. . Further, these compounds may be used in combination with other compounds having one or more ethylenically unsaturated double bonds in the above molecule.

Examples of the energy ray-curable compound (B) having one or more epoxy groups in one molecule used in the present invention include vinylcyclohexene dioxide, limonene (mono) diepoxide and 1,2-epoxy-5. -Hydroxy-4,7-methano-perhydroindene, 3,4
-Epoxycyclohexylmethyl- (3,4-epoxy) cyclohexanecarboxylate, bis (3,4-
Epoxy cyclohexyl) adipate, methacrylic acid-
Alicyclic epoxies such as (3,4-epoxycyclohexyl) methyl, bisphenol F type epoxies, bisphenol A type epoxies, bisphenol type epoxies such as bisphenol S type epoxies, phenol novolac type epoxies, cresol novolac type epoxies and other novolac type epoxies. Adipic acid diglycidyl ether, 1,6-
Examples thereof include hexanediol diglycidyl ether, polypropylene glycol diglycidyl ether, copolymers of glycidyl (meth) acrylate and vinyl monomers, and the like. These energy ray-curable compounds having one or more epoxy groups in one molecule may be used alone or in combination of two or more at an arbitrary ratio, if necessary.

The energy ray-curable compound (B) having one or more epoxy groups in one molecule used in the present invention may have two or more halogen atoms bonded in the molecule. Examples of the halogen atom include a fluorine atom,
Examples thereof include chlorine atom, bromine atom and iodine atom, with bromine atom being preferred. Examples of the energy ray-curable epoxy compound (b) having two or more bromine atoms and one or more epoxy groups in one molecule include dibromophenyl glycidyl ether, dibromoneopentyl glycol diglycidyl ether and di (tri) bromo. Epoxidized product of phenol, epoxidized product of di (tri) bromocresol,
Examples include epoxidized products of brominated phenol novolac and epoxidized tetrabromobisphenol A. Energy ray-curable epoxy compound (b) having two or more bromine atoms and one or more epoxy groups in one molecule
Can be used by mixing with other energy ray-curable compound having one or more epoxy groups in one molecule at an arbitrary ratio, if necessary.

As the photopolymerization initiator such as the photoradical initiator (C) and the photocationic initiator (D), any one can be used as long as it has a polymerization initiation ability upon irradiation with ultraviolet rays or visible rays. Specific examples of the photoradical initiator (C) include benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, acetophenone, and 2, 2.
-Dimethoxy-2-phenylacetophenone, 2,2-
Acetophenones such as diethoxy-2-phenylacetophenone, anthraquinones such as 2-methylanthraquinone, 2-ethylanthraquinone and 1-chloroanthraquinone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone and the like Thioxane, ketals such as acetophenone dimethyl ketal and benzyl dimethyl ketal, benzophenone such as benzophenone or xanthone, 1-hydroxycyclohexyl phenyl ketone (Ciba Geigy Corp., Irgacure 184), 1- (4-isopropyl) Phenyl) -2-hydroxy-2-methyl-propan-1-one (manufactured by Merck & Co., Darocur 111
6), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (manufactured by Merck Ltd., Darocur 11
73), 1- (4-dodecyl-phenyl) -2-hydroxy-2-methyl-propan-1-one (Merck K.K.).
Made, Darocur 953), benzoin, etc. and 4- (2-
Hydroxyethoxy) phenyl- (2-hydroxy-2
-Propyl) ketone (manufactured by Merck Ltd., Darocur 2
959) and the like.

Examples of the photocationic initiator (D) include polyarylsulfonium hexafluorophosphate, polyarylsulfonium hexafluoroantimonium salt, and other polyarylsulfonium complex salts, aromatic sulfonium salts of halogen-containing complex ions, and iodonium salts. And aromatic onium salts of Group 3a, 5a and 6a elements, metallocene compounds and the like.

When a (meth) acrylate is used as an energy ray-curable compound having one or more ethylenically unsaturated double bonds in one molecule, usually, a photoradical polymerization initiator (C) and ( Alternatively, a photocationic polymerization initiator (D) is used. When a vinyl ether compound or an epoxy compound is used as the energy ray-curable compound having one or more ethylenically unsaturated double bonds in one molecule, a photocationic polymerization initiator (D) is usually used.
These photo-radical initiators (C) or (and) photo-cationic initiators (D) may be used alone or in combination of two or more at an arbitrary ratio, if necessary.

The inorganic filler (E) optionally used in the present invention imparts a viscosity suitable for adhering to the coil ends of rotors of motors, deformation after adhering and sagging prevention property. Along with this, it is used for increasing the specific gravity of the resin composition so that the balance can be corrected by using a small amount. Specific examples of the inorganic filler (E) include:
Examples thereof include metal oxides such as iron oxide, lead oxide, antimony oxide, titanium oxide, barium oxide, silicon oxide, and magnesium oxide, and powders and particles of barium sulfate. The above inorganic fillers may be used alone or in combination of two or more at an arbitrary ratio, if necessary.

The amount of the energy ray-curable compound (A) having one or more ethylenically unsaturated double bonds in one molecule in the resin composition (1) of the present invention is 40% of the total amount of the resin composition. ˜99.8% by weight is preferable, and particularly preferably 50 to 99% by weight. When the radical photopolymerization initiator (C) is used, the total amount of the resin composition is 0.1 to 0.1%.
It is preferably 10.0% by weight, particularly preferably 0.5 to
It is 7.0% by weight, and when the cationic photopolymerization initiator (D) is used, it is preferably 0.2 to 10.0% by weight of the total amount of the resin composition, and particularly preferably 1.0 to 8.0. weight%
Is. When the radical photopolymerization initiator (C) and the cationic photopolymerization initiator (D) are used in combination, the total amount used is preferably 0.2 to 10.0% by weight of the total amount of the resin composition, and particularly preferably 0. It is 5 to 8.0% by weight.

The amount of the energy ray-curable compound (B) having one or more epoxy groups in one molecule in the resin composition (2) of the present invention is 40 to 9 based on the total amount of the resin composition.
9.4 wt% is preferable, 50-99 wt% is particularly preferable, and the amount of the cationic photopolymerization initiator (D) used is preferably 0.5-10.0 wt%, particularly preferably 1.0- It is 5.0% by weight. The amount of the energy ray-curable compound (a) having two or more bromine atoms and one or more ethylenically unsaturated double bond in one molecule in the resin composition of (3) is the total amount of the resin composition. 40 to 99.8
Weight% is preferable, and 50 to 99 weight% is particularly preferable. When the radical photopolymerization initiator (C) is used,
0.1 to 10.0% by weight of the total amount of the resin composition is preferable, and 0.5 to 7.0% by weight is particularly preferable. When the cationic photopolymerization initiator (D) is used, Is preferably 0.2 to 10.0% by weight, and particularly preferably 0.5 to 8.0% by weight. When the radical photopolymerization initiator (C) and the cationic photopolymerization initiator (D) are used in combination, the total amount used is 0.2 to 10.0 of the total amount of the resin composition.
Weight% is preferable, and 0.5 to 8.0 weight% is particularly preferable. The amount of the inorganic filler (E) used in the resin composition of (5) is 2 to 50% by weight of the total amount of the resin composition.
Is preferable, and particularly preferably 5 to 40% by weight.

The energy ray-curable resin composition of the present invention contains compound (A) or (and) compound (B), radical photopolymerization initiator (C) or (and) cationic photopolymerization initiator (D) and, if necessary, According to the above, it is obtained by mixing the inorganic filler (E) by a known method such as stirring. In addition to the above components, the energy ray-curable resin composition of the present invention may optionally contain a photosensitizer, a photopolymerization accelerator, a peroxide, a non-reactive polymer, a thermal cross-linking agent, a polymerization inhibitor, and a sensitizer. Auxiliaries such as a sticking agent, a leveling agent, a fluidity improving agent, a defoaming agent, a matting agent, a plasticizer, a solvent, a filler, an ion scavenger, and a colorant such as a pigment or a dye can be used in combination.
Incidentally, the higher the specific gravity of the resin composition, the more it is possible to correct the balance by using a small amount of the resin composition and the separation with the inorganic filler added to impart high specific gravity and thixotropy becomes less likely to occur. Therefore, the specific gravity of the photocurable resin composition of the present invention is preferably 1.4 (25 ° C) or higher. If the viscosity of the resin composition is too high, it cannot be applied with a dispenser. Therefore, the viscosity is preferably 1,000 poise (25 ° C.) or less.

In order to apply and cure the energy ray-curable resin composition of the present invention to the rotors of motors as a balancing resin, it is possible to irradiate and cure with ultraviolet rays or electron beams after manually applying. Balance tester, dispenser,
It is preferable to automatically and continuously apply and cure a device using a combination of devices such as an ultraviolet irradiator, because a motor with balanced balance can be efficiently produced. To cure the energy ray-curable resin composition of the present invention, it is possible to use ultraviolet rays or visible rays irradiated by a high pressure mercury lamp, a metal halide lamp, a xenon lamp, an Ar laser, a He-Cd laser, a semiconductor laser or the like. it can. Alternatively, an electron beam can be used. After curing by irradiating with visible light or radiation, the heat ray of an infrared lamp or hot air can be used for further heat curing.

[0018]

EXAMPLES The present invention will be described in more detail below with reference to synthesis examples and examples, but the present invention is not limited to these examples. Synthesis Example 1 (Synthesis Example of Acrylate Oligomer) 254 g of epoxidized tetrabromobisphenol A in a 1 L reactor equipped with a thermometer, a cooling pipe, and a stirrer, 199 g of trimethylolpropane triacrylate as a reactive diluting monomer, and 44. 6 g, 2,4,6-tris (dimethylaminomethyl) phenol 2 g as a catalyst, and hydroquinone monomethyl ether 0.3 g as a polymerization inhibitor were charged at one time and stirred at 90 ° C.
The temperature was gradually raised to 90 ± 2 ° C. and the reaction was continued for 15 hours to obtain 498 g of epoxy acrylate. Its viscosity was 730 poise / 25 ° C. and its specific gravity was 1.419 / 25 ° C.

Synthesis Example 2 (Synthesis Example of Acrylate Oligomer) A 1 L reactor similar to Synthesis Example 1 was charged with 410 g of dibromophenylglycidyl ether, 90 g of acrylic acid, 1 g of hydroquinone monomethyl ether as a polymerization inhibitor, and 3 g of triphenylstibine as a catalyst. , 90 ° C for 10
After reacting for a time, 500 g of epoxy acrylate was obtained.
Its viscosity is 60 poise / 25 ° C, and its specific gravity is 1.666 / 2.
5 ° C.

Synthesis Example 3 (Synthesis Example of Acrylate Oligomer) In the same 1 L reactor as in Synthesis Example 1, 415 g of dibromomethylphenylglycidyl ether, 83 g of acrylic acid, 1 g of hydroquinone monomethyl ether as a polymerization inhibitor,
Charge 2g of triphenylstibine as a catalyst, 90 ℃
And reacted for 10 hours to obtain 499 g of epoxy acrylate. Its viscosity is 178 poise / 25 ° C, and its specific gravity is 1.6.
It was 42/25 ° C.

Examples 1 to 8 Compound (A) having one or more ethylenically unsaturated double bond in one molecule, photoradical initiator (C), photocationic initiator (D), in one molecule Compound (B) having one or more epoxy groups, compound (a) having two or more halogens and one or more ethylenically unsaturated double bond in one molecule, and two or more bromine in one molecule The epoxy compound (b) having an atom and the inorganic filler (E) were uniformly mixed according to the compounding ratio (parts by weight) shown in Table 1 to obtain a photocurable resin composition. Next, the physical properties of this composition, various properties of its cured product, and performance evaluation as a resin for balancing rotors of motors were evaluated as follows.

Viscosity: The viscosity of the composition at 25 ° C. was measured using an E-type viscometer manufactured by Tokimec Co., Ltd. Liquid specific gravity: The specific gravity of the composition at 25 ° C. was measured using a density / specific gravity meter manufactured by Kyoto Electronics Manufacturing Co., Ltd. Specific gravity of cured film: The specific gravity of a cured film at 25 ° C was determined from the difference between the weight in air and the weight in water. Curing speed: The composition was coated on a PET film to a thickness of 400 μm and irradiated with ultraviolet rays using a 2 KW (80 W / cm) high pressure mercury lamp to measure the irradiation dose until the inside of the composition was cured. did.

[0023]

Table 1 Ingredients Example 1 2 3 4 5 6 7 8 Synthesis Example 1 (Component a) 50 Synthesis Example 2 (Component a) 100 50 82 Synthesis Example 3 (Component a) 50 100 100 BR-30 * 1 (Component a) 25 BR-31 * 2 (Component a) 60 25 R-561 * 3 (Component A) 40 2000 * 4 (Component B) 10 2021P * 5 (Component B) 30 8 BROC * 6 (Component b) 60 Irg-184 * 7 3 EPA * 8 2 2 2 DETX-S * 9 1 1 1 SP-170 * 10 3 3 Irg-261 * 11 3 3 Kayakumen H * 12 2 Sylysia 445 * 13 12 Viscosity (Pois / 25 ℃) 0.24 60 67 85 0.7 0.24 181 141 Liquid specific gravity (25 ° C) 1.46 1.67 1.63 1.60 1.41 1.46 1.65 1.63 Specific gravity of cured film (25 ° C) 1.77 1.73 1.69 1.74 Curing speed (mj / cm ² ) 600 400 300 400 450 600 400 400

Note * 1 New Frontier BR-30: 2,4,6-tribromophenyl acrylate; manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. * 2 New Frontier BR-31: 2- (2,4,
6-tribromophenoxy) ethyl acrylate; manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. * 3 KAYARADR-561: phenoxyethyl acrylate; manufactured by Nippon Kayaku Co., Ltd. * 4 Celoxide 2000: 4-vinylcyclohexene oxide; Asahi Denka Kogyo Co., Ltd. ) * 5 Celoxide 2021P: 3,4-epoxycyclohexylmethyl (3,4-epoxy) cyclohexanecarboxylate; manufactured by Asahi Denka Co., Ltd. * 6 BROC: dibromocresyl glycidyl ether; manufactured by Nippon Kayaku Co., Ltd. * 7 Irgacure 184: 1-hydroxycyclohexyl phenyl ketone; manufactured by Ciba Geigy * 8 KAYACUREEPA: ethyl 4- (N, N-dimethylamino) benzoate; manufactured by Nippon Kayaku Co., Ltd. * 9 KAYACUREDE TX-S: 2,4-diethylthioki Nippon Kayaku Co., Ltd. * 10 Adekaoptomer SP-170: Photocationic polymerization catalyst; Asahi Denka Kogyo Co., Ltd. * 11 Irgcure261: (1-6-η-cumene) (η-cyclopentadienyl) Iron (1+) hexafluorophosphate (1−); manufactured by Ciba Geigy * 12 Kayakumen H: Cumene hydroperoxide; Kayaku Akzo Co., Ltd. * 13 Sylysia 445: Synthetic silica; Fuji Silysia Chemical Co., Ltd.

[0025]

EFFECTS OF THE INVENTION By using the photocurable resin composition of the present invention, it is possible to produce a motor-type rotor whose balance is accurately corrected with high productivity by only irradiation with light for a short time.

Claims (8)

[Claims] 1. An active energy ray-curable compound (A) having one or more ethylenically unsaturated double bonds in one molecule,
An active energy ray-curable resin composition for balancing rotors of motors, which comprises a photoradical polymerization initiator (C) and / or a photocationic polymerization initiator (D). 2. The active energy ray-curable resin composition for balancing rotors of motors according to claim 1, wherein the compound (A) is an active energy ray-curable compound having two or more bromine atoms in the molecule. 3. An active energy ray-curable resin for balancing a rotor of a motor, which comprises an active energy ray-curable compound (B) having one or more epoxy groups in one molecule and a photocationic polymerization initiator (D). Composition. 4. The active energy ray-curable resin composition for balancing a motor rotor according to claim 3, wherein the compound (B) is an active energy ray-curable compound having two or more bromine atoms in the molecule. 5. An active energy ray-curable compound (a) having at least two bromine atoms and at least one ethylenically unsaturated double bond in one molecule, and / or at least two in one molecule. Active energy ray-curable resin composition for balancing rotors for motors containing an active energy ray-curable epoxy compound (b) having a bromine atom, a photoradical initiator (C) and / or a photocationic initiator (D) Stuff. 6. The motor according to claim 1, wherein the resin composition has a specific gravity of 1.4 (25 ° C.) or more and a viscosity of 1,000 poise (25 ° C.) or less. An active energy ray-curable resin composition for balancing a rotor. 7. The active energy ray-curable resin composition for balancing rotors of motors according to claim 1, which contains an inorganic filler (E). 8. A motor rotor to which the active energy ray-curable resin composition according to any one of claims 1 to 7 is attached.