Active energy ray-curable resin composition

Abstract

The present invention provides an active energy ray-curable resin composition which is excellent in terms of ejection properties and curability in a deep portion, and which enables the achievement of a cured product that has a low hardness, can exhibit a high aspect ratio, and can exhibit good reworkability and wet heat tear resistance.　Provided is an active energy ray-curable resin composition which contains the following component (A), component (B), component (C), and component (D): (A) a urethane acrylate oligomer which has a weight average molecular weight of not less than 10,000 but less than 40,000 and comprises a urethane skeleton that has an ether bond; (B) a monofunctional acrylic acid ester monomer; (C) a photopolymerization initiator; and (D) fumed silica. The active energy ray-curable resin composition is characterized in that: the component (C) contains a compound that has a benzoyl group; a cured product, which has a thickness of 2 mm and is obtained by irradiating the active energy ray-curable resin composition with ultraviolet light at an illuminance of 300 mW / cm2 and an accumulated light quantity of 3,000 mJ / cm2 using a high-pressure mercury lamp, has a storage elastic modulus G' of 700,000 Pa or less at 25°C as determined in a rotating shear mode at a vibration frequency of 1 Hz at a heating rate of 5°C / min over a temperature range of -60°C to 70°C using a dynamic viscoelasticity measurement device; and with respect to the cured product, the peak temperature of Tanδ is 15°C or less, and the peak height of Tanδ is 1.7 or less.

Description

Active energy ray-curable resin composition

[0001] The present invention relates to an active energy ray-curable resin composition.

[0002] Active energy ray-curable resin compositions have been widely used in coatings, adhesives, cast-in-place liquid gaskets (CIPG), and other applications due to their ability to cure in a short time.

[0003] Active energy ray-curable resin compositions used in the above-mentioned applications can be subject to oxygen inhibition during photocuring if the cured surface is exposed to air (oxygen), resulting in insufficient curing of the cured surface and tackiness. Active energy ray-curable resin compositions used in coating and CIPG applications, in particular, require a tack-free cured surface to prevent contamination from adhering to the cured surface and to prevent substrates from sticking together. Being tack-free is crucial for reworkability, as it allows for easy peeling in the event of a defect in components where a CIPG is applied to a device-mounted housing and then bonded to a cover case. In particular, for CIPG applications, the CIPG thickness must be increased depending on the component shape and design, requiring good deep curing properties.

[0004] As such an active energy ray-curable resin composition, a photocurable composition containing specific components such as an elastomer (A), a monomer (B) having a (meth)acryloyl group, and a photopolymerization initiator (C) has been proposed (see, for example, Patent Document 1).

[0005] Japanese Patent Application Laid-Open No. 2022-174718

[0006] However, the photocurable composition described in Patent Document 1 uses a specific elastomer (A) and a monomer (B) having a (meth)acryloyl group. Because the Tg of the monomer having a (meth)acryloyl group is high, the composition is expected to have high hardness. Active energy ray-curable resin compositions used in CIPG applications, etc., are required to have low hardness in the cured product. Furthermore, to improve the tack-free properties and reworkability of the cured surface, measures to increase crosslink density by using multifunctional acrylates or low-molecular-weight urethane acrylates are commonly used. However, these measures result in a problem of high hardness in the cured product. When used in housings made of resins such as ABS and polycarbonate, these cured products may undergo creep deformation.

[0007] Although it is possible to form a soft cured product with low hardness by adding a thiol compound to the active energy ray-curable resin composition or by selecting an oligomer skeleton, the resulting product has problems of low strength and reduced resistance to tearing under moist heat, and the cured product is prone to develop surface tackiness, resulting in reduced reworkability.

[0008] Furthermore, the photocurable composition described in Patent Document 1 has not been fully investigated in terms of exhibiting properties suitable for CIPG applications, such as dischargeability, a high aspect ratio, etc. Active energy ray-curable resin compositions used for CIPG applications are required to be able to be applied to the desired shape when applied to the area where the CIPG is to be formed at a certain discharge pressure and application speed, that is, to have excellent dischargeability, and there is a problem that if the discharge amount at a certain discharge pressure is small, the composition cannot be used for CIPG applications.

[0009] Furthermore, the above-mentioned active energy ray-curable resin composition is required to be able to be formed into a desired shape, and the cured product thus formed is required to exhibit a high aspect ratio.

[0010] In view of the above circumstances, an object of the present invention is to provide an active energy ray-curable resin composition that has excellent dischargeability and deep curing properties, that can produce a cured product with low hardness and a high aspect ratio, and that can produce a cured product with good reworkability and moist heat tear resistance.

[0011] As a result of extensive research, the present inventors have discovered that an active energy ray-curable resin composition containing specific components (A) to (D), in which component (C) includes a compound having a benzoyl group, can be cured by using a high-pressure mercury lamp at an illumination intensity of 300 mW / cm. 2 , cumulative light intensity 3000mJ / cm 2 The present inventors have found that the above-mentioned object can be achieved by using an active energy ray-curable resin composition in which a 2 mm-thick cured product obtained by irradiating the resin with ultraviolet light under the above conditions has a storage modulus G' at 25°C of 700,000 Pa or less, a Tan δ peak temperature of 15°C or less, and a Tan δ peak height of 1.7 or less, as measured using a dynamic viscoelasticity apparatus in a rotational shear mode with an oscillation frequency of 1 Hz, a heating rate of 5°C / min, and a temperature range of -60°C to 70°C, and the above-mentioned object has been achieved, leading to the completion of the present invention.

[0012] That is, the present invention relates to the following active energy ray-curable resin composition: 1. An active energy ray-curable resin composition containing the following components (A), (B), (C), and (D): (A) a urethane acrylate oligomer having a urethane skeleton having an ether bond and a weight average molecular weight of 10,000 or more and less than 40,000, (B) a monofunctional acrylic acid ester monomer, (C) a photopolymerization initiator, and (D) fumed silica, wherein the component (C) contains a compound having a benzoyl group, and the active energy ray-curable resin composition is heated at an illuminance of 300 mW / cm using a high-pressure mercury lamp. 2 , cumulative light intensity 3000mJ / cm 2Item 1. An active energy ray-curable resin composition characterized in that a 2 mm-thick cured product obtained by irradiating ultraviolet light under the above conditions has a storage modulus G' at 25°C of 700,000 Pa or less, a Tan δ peak temperature of 15°C or less, and a Tan δ peak height of 1.7 or less, as measured using a dynamic viscoelasticity apparatus in a rotational shear mode with a vibration frequency of 1 Hz, at a heating rate of 5°C / min, and in a temperature range of -60°C to 70°C. 2. An active energy ray-curable resin composition according to Item 1, wherein the component (C) includes (i) methyl benzoyl formate and (ii) a benzophenone compound or an α-hydroxyacetophenone compound. 3. The active energy ray-curable resin composition according to Item 1 or 2, wherein the content of the component (A) is 10 to 30 mass%, where the total content of the component (A) and the component (B) is 100 mass%. 4. 4. The active energy ray-curable resin composition according to any one of Items 1 to 3, wherein the component (B) contains the following components (B1) and (B2): (B1) phenoxyethyl acrylate; and (B2) an alkyl acrylate having 8 or 12 carbon atoms, or an alkyl acrylate having 9 to 10 carbon atoms and an iso structure. The content of the component (B2) is 30% by mass or less, where the total content of the components (B1) and (B2) is 100% by mass.

[0013] The active energy ray-curable resin composition of the present invention has excellent dischargeability and deep curing properties, and the cured product has low hardness and can exhibit a high aspect ratio. The cured product also exhibits good reworkability and moist heat tear resistance.

[0014] The present invention will be described in detail below.

[0015] 1. Active Energy Ray-Curable Resin Composition The active energy ray-curable resin composition of the present invention is an active energy ray-curable resin composition containing the following components (A), (B), (C), and (D): (A) a urethane acrylate oligomer having a urethane skeleton having an ether bond and a weight average molecular weight of 10,000 or more and less than 40,000, (B) a monofunctional acrylic acid ester monomer, (C) a photopolymerization initiator, and (D) fumed silica; the component (C) contains a compound having a benzoyl group; and the active energy ray-curable resin composition is heated at an illuminance of 300 mW / cm using a high-pressure mercury lamp. 2 , cumulative light intensity 3000mJ / cm 2 The cured product having a thickness of 2 mm obtained by irradiating with ultraviolet light under the above conditions is an active energy ray-curable resin composition having a storage modulus G' at 25°C of 700,000 Pa or less, a Tan δ peak temperature of 15°C or less, and a Tan δ peak height of 1.7 or less, as measured using a dynamic viscoelasticity device in a rotational shear mode with a vibration frequency of 1 Hz, a heating rate of 5°C / min, and a temperature range of -60°C to 70°C.

[0016] The active energy ray-curable resin composition having the above characteristics contains the above-mentioned specific components (A) to (D), and the component (C) contains a compound having a benzoyl group. Furthermore, the cured product obtained by curing under specific conditions exhibits the above-mentioned properties, and therefore the active energy ray-curable resin composition has excellent dischargeability.

[0017] In this specification, "dischargeability" refers to the ability to apply a CIPG or other cured product to a desired shape (bead shape) when applied at a certain discharge pressure and application speed to a location where a cured product is desired to be formed, and means that the product can be applied under a wide range of conditions, specifically, that the product can accommodate bead widths ranging from narrow to wide within a predetermined discharge pressure range, and can accommodate bead heights ranging from small to large, but does not mean that the product can be applied to a wide range of bead widths and bead heights.

[0018] Furthermore, since the active energy ray-curable resin composition of the present invention has the above-mentioned configuration, it has excellent deep curing properties, and the cured product has low hardness and excellent flexibility. The cured product can exhibit a high aspect ratio, and the cured product can exhibit good reworkability and moist heat tear resistance.

[0019] The active energy ray-curable resin composition of the present invention as described above can be used for CIPG applications in a variety of products, and can be suitably used for, for example, control equipment such as sensors, devices for home appliances, digital cameras, and in-vehicle electrical components.

[0020] The active energy ray-curable resin composition of the present invention will be described in detail below.

[0021] The active energy ray-curable resin composition of the present invention was heated at an illuminance of 300 mW / cm using a high-pressure mercury lamp. 2 , cumulative light intensity 3000mJ / cm 2 A 2 mm-thick cured product obtained by UV irradiation under the above conditions has a storage modulus G' of 700,000 Pa or less at 25°C, as measured using a dynamic viscoelasticity apparatus in a rotational shear mode with a vibration frequency of 1 Hz, a heating rate of 5°C / min, and a temperature range of -60°C to 70°C. If the storage modulus G' of the cured product exceeds 700,000 Pa, the hardness increases. The storage modulus G' is preferably 650,000 Pa or less, more preferably 650,000 Pa or less, and even more preferably 600,000 Pa or less. There is no particular limitation on the lower limit of the storage modulus G', and it may be, for example, 100,000 Pa, 200,000 Pa, 300,000 Pa, or 400,000 Pa.

[0022] The active energy ray-curable resin composition of the present invention was heated at an illuminance of 300 mW / cm using a high-pressure mercury lamp. 2 , cumulative light intensity 3000mJ / cm 2 A 2 mm thick cured product obtained by UV irradiation under the above conditions has a Tan δ peak temperature of 15°C or less, measured using a dynamic viscoelasticity device in a rotational shear mode with an oscillation frequency of 1 Hz, at a temperature rise rate of 5°C / min, and in a temperature range of -60°C to 70°C. The Tan δ peak temperature is preferably 10°C or less. There is no particular limitation on the lower limit of the Tan δ peak temperature, and it may be -25°C, -20°C, etc.

[0023] The active energy ray-curable resin composition of the present invention was heated at an illuminance of 300 mW / cm using a high-pressure mercury lamp. 2 , cumulative light intensity 3000mJ / cm 2 A 2mm-thick cured product obtained by UV irradiation under the above conditions has a peak height of 1.7 or less when measured using a dynamic viscoelasticity apparatus in a rotational shear mode with a vibration frequency of 1Hz, a heating rate of 5°C / min, and a temperature range of -60°C to 70°C. If the Tan δ peak height exceeds 1.7, reworkability decreases. The Tan δ peak height is preferably 1.5 or less, more preferably 1.3 or less. There is no particular limitation on the lower limit of the Tan δ peak height, and it may be 0.8 or 0.85.

[0024] In the present invention, the storage modulus G', the peak temperature of Tan δ, and the peak height of Tan δ are specifically measured by the following measurement methods.

[0025] Measurement method for dynamic viscoelasticity (storage modulus G', Tanδ peak temperature, Tanδ peak height): A 2 mm thick silicone rubber sheet formed into a rectangular frame was prepared as a spacer. The spacer was then placed on an aluminum plate that had been treated with a release agent, and the active energy ray-curable resin composition was dripped into the frame of the spacer. Quartz glass was prepared, and placed on top of the active energy ray-curable resin composition so that it was in contact with the resin composition. The mixture was then compressed and measured in this state using a high-pressure mercury lamp at an illuminance of 300 mW / cm. 2 , cumulative light intensity 3000mJ / cm 2 The quartz glass is peeled off to prepare a sample for measuring dynamic viscoelasticity. Using the sample prepared as described above, dynamic viscoelasticity measurements (heating process) are performed using a dynamic viscoelasticity measuring device (TA Instruments, Model HR-10) in rotational shear mode at a frequency of 1 Hz, in the temperature range of -60°C to 70°C, and at a heating rate of 5°C / min. The measured values ​​are the peak temperature, peak height, and storage modulus G' at 25°C of Tan δ obtained by the measurement.

[0026] Hereinafter, each component constituting the active energy ray-curable resin composition of the present invention will be described in detail.

[0027] Component (A) Component (A) is a urethane acrylate oligomer having a weight average molecular weight of 10,000 or more and less than 40,000, which is composed of a urethane skeleton having an ether bond.

[0028] The weight-average molecular weight (Mw) of component (A) is 10,000 or more and less than 40,000. If the weight-average molecular weight is less than 10,000, the hardness of the cured product of the active energy ray-curable resin composition will be too high, making it unsuitable for applications such as CIPG. The weight-average molecular weight is preferably 11,000 to 38,000, and more preferably 13,000 to 33,000.

[0029] In the present invention, the weight average molecular weight (Mw) is a measured value obtained by converting the value into standard polystyrene using a gel permeation chromatograph (GPC) measuring device.

[0030] The urethane acrylate oligomer of component (A) has a urethane skeleton containing an ether bond, and is not particularly limited as long as its weight-average molecular weight is within the above-mentioned range. Examples of such urethane acrylate oligomers include urethane acrylates having a polytetramethylene ether glycol derivative skeleton, a polypropylene glycol skeleton, a polyethylene glycol skeleton, or modified structures thereof.

[0031] The urethane acrylate oligomer of component (A) can be obtained by reacting a polyol having the above-mentioned polytetramethylene ether glycol derivative skeleton, polyether polycarbonate skeleton, polypropylene glycol skeleton, polyethylene glycol skeleton, polypropylene triol skeleton, or a modified structure thereof with at least one isocyanate compound selected from the group consisting of alicyclic diisocyanate compounds, aliphatic diisocyanate compounds, and aromatic diisocyanate compounds, followed by an addition reaction (also referred to as a urethanization reaction) between the isocyanate group and the hydroxyl group of an acrylate having a hydroxyl group.

[0032] The diisocyanate compound is preferably an alicyclic diisocyanate, such as 4,4'-methylenebis(cyclohexyl isocyanate), 1,3-(isocyanatomethyl)cyclohexane, or isophorone diisocyanate.

[0033] The urethane acrylate oligomer of component (A) can be a commercially available product, such as UV-3300B (manufactured by Mitsubishi Chemical Corporation) or UV-3700B (manufactured by Mitsubishi Chemical Corporation).

[0034] The content of component (A) is preferably 4 to 45% by mass, more preferably 7 to 40% by mass, and even more preferably 9 to 30% by mass, based on 100% by mass of the active energy ray-curable resin composition. By having the content of component (A) in this range, the dischargeability of the active energy ray-curable resin composition is further improved, and the cured product can have lower hardness and a higher aspect ratio, and can exhibit better reworkability and moist heat tear resistance.

[0035] The content of component (A) relative to the total of component (A) and component (B), which will be described later, is preferably 5 to 45 mass%, more preferably 8 to 40 mass%, and even more preferably 10 to 30 mass%. When the content of component (A) is within the above range, the dischargeability of the active energy ray-curable resin composition is further improved, and the cured product can have lower hardness and a higher aspect ratio, and can exhibit better reworkability and moist heat tear resistance.

[0036] Component (B) Component (B) is a monofunctional acrylic acid ester monomer. By including the component (B), the hardness of the cured product of the active energy ray-curable resin composition is reduced, making it suitable for use in CIPG applications, etc. Furthermore, despite the low hardness of the cured product, the active energy ray-curable resin composition of the present invention can exhibit excellent reworkability and moist heat tear resistance.

[0037] The component (B) is not particularly limited as long as it is a monofunctional acrylate monomer. Examples of such monofunctional acrylate monomers include monofunctional (meth)acrylate monomers having one unsaturated bond in the molecule.

[0038] Specific examples of the monofunctional (meth)acrylic acid ester monomer include chain alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 1-ethylheptyl (meth)acrylate, nonyl (meth)acrylate, n-octyl acrylate, isononyl (meth)acrylate, isodecyl acrylate, 1-butylamyl (meth)acrylate, lauryl (meth)acrylate, and octadecyl (meth)acrylate; and chain alkyl (meth)acrylates such as isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and phenoxyethanol. (meth)acrylates having a cyclic structure such as polyethylene glycol (meth)acrylate, nonylphenoxy polyethylene glycol (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, phenoxy (meth)acrylate, phenoxyethyl (meth)acrylate, alkylphenoxy (meth)acrylate, and alkylphenoxyethyl (meth)acrylate; hydroxyalkyl (meth)acrylates having a hydroxyl group such as hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, and 2-hydroxylauryl (meth)acrylate, or 2-hydroxy-3-phenoxypropyl acrylate;and mono(meth)acrylates of oligo- or polyoxyalkylene glycols such as diethylene glycol mono(meth)acrylate, triethylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, dipropylene glycol mono(meth)acrylate, trimethylene glycol mono(meth)acrylate, and polypropylene glycol (meth)acrylate. These may be used alone or in combination of two or more.

[0039] Among these, it is preferable to use at least one selected from the group consisting of (meth)acrylic acid ester monomers having an alicyclic structure, (meth)acrylic acid ester monomers having a cyclic structure such as an aromatic skeleton, (meth)acrylic acid ester monomers having an aromatic skeleton and modified with ethylene oxide, (meth)acrylic acid ester monomers having a hydroxyl group in the molecule, and chain alkyl (meth)acrylates. Among these, it is particularly preferable to use chain alkyl (meth)acrylates, from the viewpoint of making the cured product of the active energy ray-curable resin composition more flexible.

[0040] Examples of (meth)acrylic acid ester monomers having an alicyclic structure include isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentanyl (meth)acrylate. Examples of (meth)acrylates having an aromatic skeleton and modified with ethylene oxide include phenoxypolyethylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, and nonylphenoxypolyethylene glycol (meth)acrylate, and examples of (meth)acrylic acid ester monomers having a cyclic structure such as an aromatic skeleton include phenoxyethyl (meth)acrylate.

[0041] Among these, phenoxy polyethylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, etc. are particularly preferred.

[0042] The glass transition temperature (Tg) of the monofunctional acrylic acid ester monomer of component (B) is preferably −80 to 15° C., more preferably −70 to 5° C. When the glass transition temperature of component (B) is within the above range, the cured product obtained by curing the active energy ray-curable resin composition of the present invention has appropriate flexibility, and can be suitably used for coating applications and CIPG applications.

[0043] The content of component (B) is preferably 50 to 95% by mass, more preferably 60 to 92% by mass, and even more preferably 70 to 90% by mass, relative to 100% by mass of the total of components (A) and (B). When the content of component (B) is within the above range, the cured product obtained by curing the active energy ray-curable resin composition of the present invention has appropriate flexibility, making it suitable for use in coating applications and CIPG applications.

[0044] The component (B) preferably contains phenoxyethyl acrylate as the component (B1) and an alkyl acrylate having 8 or 12 carbon atoms or an alkyl acrylate having an iso structure and having 9 to 10 carbon atoms as the component (B2). When the component (B) contains the above-mentioned components (B1) and (B2), the hardness of the cured product of the active energy ray-curable resin composition becomes lower.

[0045] When the component (B) contains the above-mentioned components (B1) and (B2), the content of the component (B2) is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less, based on 100% by mass of the total content of the components (B1) and (B2). The content of the component (B2) is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, based on 100% by mass of the total content of the components (B1) and (B2).

[0046] Component (C) The component (C) is a photopolymerization initiator. In the present invention, the component (C) includes a compound having a benzoyl group. By including the component (C), the deep curability of the active energy ray-curable resin composition of the present invention is improved.

[0047] Examples of compounds having a benzoyl group include methyl benzoyl formate (methyl benzoylformate).

[0048] The compound having a benzoyl group may be a commercially available product, such as "Omnirad MBF" manufactured by iGM RESINS.

[0049] The component (C) preferably contains, in addition to the above-mentioned (i) methylbenzoyl formate, (ii) a benzophenone compound or an α-hydroxyacetophenone compound. When the component (C) has the above-mentioned structure, the deep curability and surface curability of the active energy ray-curable resin composition of the present invention are further improved.

[0050] When component (C) contains a benzophenone compound, the benzophenone compound undergoes a triplet excited state upon exposure to light and abstracts hydrogen from the oligomer and / or (meth)acrylate monomer as a donor, causing the oligomer and / or (meth)acrylate monomer from which hydrogen has been abstracted to generate radicals, which efficiently initiate radical polymerization and / or crosslinking reactions with the oligomer and / or (meth)acrylate monomer, thereby further improving the curability of the surface.

[0051] Examples of the benzophenone compound include benzophenone, 4-methylbenzophenone, 4-phenylbenzophenone, and benzophenone derivatives.

[0052] Specific examples of the benzophenone derivative include 4-(4-methylphenylthio)benzophenone, 4,4'-bis(diethylamino)benzophenone, and methyl 2-benzoylbenzoate.

[0053] The benzophenone compound contained in component (C) may be a commercially available product, such as those manufactured by iGM RESINS under the product names "Ommiad BP Flakes," "Omnirad 4MBZ Flakes," "Omnirad BMS," "Omnirad EMK," "Omnirad OMBB," and "Omnirad 4PBZ."

[0054] Examples of the α-hydroxyacetophenone compound include α-hydroxyacetophenone derivatives.

[0055] Specific examples of α-hydroxyacetophenone derivatives include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methylpropiophen, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophen, and 2,2'-dihydroxy-2,2'-dimethyl-1,1'-[methylenebis(4,1-phenylene)]bis(propan-1-one).

[0056] The α-hydroxyacetophenone derivative contained in component (C) may be a commercially available product, such as those manufactured by iGM RESINS under the product names "Omnirad 184," "Omnirad 1173D," "Omnirad 127D," "Esacure ONE," and "Esacure KIP 160."

[0057] Component (C) may further contain other photopolymerization initiators, such as phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, ethylphenyl(2,4,6-trimethylbenzoyl)phosphinate, benzyl ketal compounds, and α-aminoalkylphenone derivatives.

[0058] Examples of benzyl ketal compounds include 2,2-dimethoxy-2-phenylacetophenone, etc. Commercially available products of the benzyl ketal compounds include "Omnirad 651," etc.

[0059] Examples of α-aminoalkylphenone derivatives include 2-methyl-4'-(methylthio)-2-morpholinopropiophenone, 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone, etc. Commercially available products of the above benzyl ketal compounds include "Omnirad 907" and "Omnirad 369."

[0060] The component (C) may be used alone or in combination of two or more.

[0061] The content of component (C) is preferably 0.5 to 10 parts by mass, more preferably 1.0 to 8 parts by mass, and even more preferably 1.5 to 5 parts by mass, relative to 100 parts by mass of the total of components (A) and (B). By having the content of component (C) within the above range, the surface curability and deep curability of the active energy ray-curable resin composition can be maintained better, and the hardness of the active energy ray-curable resin composition after curing can be appropriately adjusted, allowing the composition to exhibit better reworkability and moist heat tear resistance.

[0062] Component (D) Component (D) is fumed silica.

[0063] The fumed silica is not particularly limited, and known fumed silica such as hydrophilic fumed silica having many hydrophilic silanol groups (Si—OH) on the surface, and hydrophobic fumed silica having many hydrophobic siloxane groups (Si—O—Si) on the surface can be used.

[0064] Since the active energy ray-curable resin composition of the present invention contains a urethane acrylate having an ether bond as component (A), it is preferable to use hydrophilic fumed silica as component (D). By using hydrophilic fumed silica as component (D), the aspect ratio of the active energy ray-curable resin composition can be further increased.

[0065] The average primary particle diameter of the fumed silica is preferably 5 nm to 50 μm. By using such fumed silica, it is possible to impart good thixotropy to the active energy ray-curable resin composition of the present invention, resulting in excellent coatability. In addition, it is possible to make the active energy ray-curable resin composition of the present invention transparent, and sufficient curability can be obtained even when irradiated with ultraviolet rays or the like.

[0066] In the present invention, the content of component (D) is preferably 4 parts by mass or more, more preferably 4.5 parts by mass or more, and even more preferably 5 parts by mass or more, relative to 100 parts by mass of the total of components (A) and (B). When the lower limit of the content of component (D) is within the above range, the cured product can exhibit better reworkability and moist heat tear resistance. Furthermore, the upper limit of the content of component (D) is not particularly limited, and may be 20 parts by mass, 15 parts by mass, 10 parts by mass, or 8 parts by mass, relative to 100 parts by mass of the total of components (A) and (B).

[0067] Other Components To the active energy ray-curable resin composition of the present invention, a polymerization inhibitor, an adhesion imparting agent, a leveling agent, an antifoaming agent, an antioxidant, a flame retardant, a colorant (pigment, dye, organic fluorescent pigment), an inorganic filler (crystalline silica, fused silica, calcium carbonate, talc, etc.), a synthetic zeolite, etc. may be added as appropriate depending on the purpose, etc.

[0068] Characteristics of the active energy ray-curable resin composition, etc. The active energy ray that cures the active energy ray-curable composition of the present invention is not particularly limited, and examples thereof include infrared rays, ultraviolet rays, visible light, laser light, X-rays, and electron beams. Among these, ultraviolet rays are preferred. As a light source for ultraviolet rays, a high-pressure mercury lamp, a metal halide lamp, or a UV-LED lamp can be used. For example, when a high-pressure mercury lamp is used, the cumulative light amount is preferably 2000 to 6000 mJ / cm. 2 When using a UV-LED lamp, the cumulative light intensity is 5,000 to 10,000 mJ / cm at a wavelength of 365 nm. 2 After irradiating, the cumulative light dose is 200-600mJ / cm at a wavelength of 280nm. 2 It is preferable to irradiate the

[0069] The viscosity of the active energy ray-curable resin composition of the present invention, measured at 25°C using a Brookfield RV viscometer (spindle No. 7) at a rotation speed of 1 rpm, is preferably 400,000 to 900,000 mPa·s, and more preferably 500,000 to 800,000 mPa·s. When the viscosity is in the above range, the dischargeability of the active energy ray-curable resin composition is further improved, and a higher aspect ratio can be exhibited.

[0070] The viscosity of the active energy ray-curable resin composition of the present invention, measured at 25°C using a Brookfield RV viscometer (spindle No. 7) at a rotation speed of 10 rpm, is preferably 60,000 to 130,000 mPa·s, and more preferably 70,000 to 120,000 mPa·s. When the viscosity is in the above range, the dischargeability of the active energy ray-curable resin composition is further improved, and a higher aspect ratio can be exhibited.

[0071] The TI value (thixotropic index) of the active energy ray-curable resin composition of the present invention is preferably 5.0 to 8.0, more preferably 6.0 to 7.0. When the TI value is within the above range, the dischargeability of the active energy ray-curable resin composition is further improved, and a higher aspect ratio can be exhibited.

[0072] In this specification, the viscosity measured at the above-mentioned rotation speeds of 1 rpm and 10 rpm and the TI value are measured by the measurement methods described in the Examples.

[0073] The aspect ratio of the cured product of the active energy ray-curable resin composition of the present invention is preferably 0.60 or more, more preferably 0.70 or more. By having the aspect ratio within the above range, it is possible to obtain a bead height of the cured product under a wide range of coating conditions, and it becomes easy to adjust the shape of parts for CIPG applications formed from the cured product to the desired shape as an alternative to molded solid gaskets. Furthermore, the upper limit of the aspect ratio is not particularly limited and may be 1.0, for example.

[0074] In this specification, the aspect ratio of the cured product is measured by the method described in the Examples.

[0075] The Shore A hardness of the cured product of the active energy ray-curable resin composition of the present invention is preferably 8 to 35, more preferably 10 to 30. When the Shore A hardness is within the above range, the CIPG can be easily compressed when bonding the housing, which is a component for CIPG applications, improving the properties of the component, such as waterproof performance, and further suppressing creep deformation of the component housing.

[0076] In this specification, the Shore A hardness of the cured product is measured by the method described in the Examples.

[0077] The method for producing the active energy ray-curable resin composition of the present invention is not particularly limited, and the composition can be produced by a conventional method. For example, the composition can be produced by kneading the above-mentioned components (A) to (D) and, if necessary, other components, using a kneader capable of temperature control and vacuum degassing, such as a planetary mixer, a twin-screw mixer, or a butterfly mixer.

[0078] Although the embodiments of the present invention have been described above, the present invention is not limited to these examples, and it goes without saying that the present invention can be embodied in various forms without departing from the spirit of the present invention.

[0079] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0080] The raw materials used in the examples and comparative examples are as follows:

[0081] (A) Component (A1): Urethane acrylate (polyether skeleton), Mw 13,000, product name: Art Resin UN-6304 (manufactured by Negami Chemical Industrial Co., Ltd.) (A2): Urethane acrylate (polyether skeleton), Mw 27,000, product name: Art Resin UN-6305 (manufactured by Negami Chemical Industrial Co., Ltd.) (A3): Urethane acrylate (polyether skeleton), Mw 33,000, product name: Art Resin EPB-402 (manufactured by Negami Chemical Industrial Co., Ltd.)

[0082] (B) Components (B1): Phenoxyethyl acrylate, product name: Light Acrylate PO-A (manufactured by Kyoeisha Chemical Co., Ltd.), Tg -22°C (B2-1): Isodecyl acrylate (C10), product name: IDAA (manufactured by Osaka Organic Chemical Industry Ltd.), Tg -62°C (B2-2): Isononyl acrylate (C9), product name: INAA (manufactured by Osaka Organic Chemical Industry Ltd.), Tg -58°C (B2-3): Isooctyl acrylate (C8), product name: NOAA (manufactured by Osaka Organic Chemical Industry Ltd.), Tg -65°C (B2-4): Lauryl acrylate (C12), product name: LA (manufactured by Osaka Organic Chemical Industry Ltd.), Tg -23°C

[0083] Ingredients (C) (C1): Type II, methyl benzoyl formate (methylbenzoyl formate), product name: Omnirad MBF (manufactured by iGM Resins) (C2): Type II, 4-methylbenzophenone, product name: Omnirad 4MBZ Flakes (manufactured by iGM Resins) (C3): α-hydroxyalkylphenone (2-hydroxy-2-methylpropiophenone), product name: Omnirad 1173D (manufactured by iGM Resins) (C4): α-hydroxyalkylphenone (oligo(2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone)), product name: Esacure ONE (manufactured by iGM Resins) (C5): α-hydroxyacetophenone (1-hydroxycyclohexylphenyl ketone), product name: Omnirad 184 (manufactured by iGM Resins) (C6): Acylphosphine oxide (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, product name Omnirad 819 (manufactured by iGM Resins)

[0084] Component (D) (D1): Hydrophilic fumed silica, product name Reolosil QS-20L (manufactured by Tokuyama Corporation)

[0085] (Examples and Comparative Examples) The above-mentioned raw materials were mixed in the amounts shown in Table 1 using a rotation / revolution mixer, Model ARE-310 (manufactured by Thinky Corporation), and first, components (A), (B), and (C) were mixed and stirred at room temperature at a rotation speed of 2000 rpm for 15 to 20 minutes to homogenize these components. Next, component (D) was added, homogenized using a spatula, and similarly mixed and stirred for 15 minutes using the same mixer, and further stirred and degassed for 2 minutes 30 seconds in degassing mode to produce an active energy ray-curable resin composition.

[0086] (Evaluation Method) The following evaluations were carried out for the Examples and Comparative Examples.

[0087] Viscosity and TI Value The viscosity at 25°C was measured using a Brookfield RV viscometer (spindle No. 7) at rotation speeds of 1 rpm and 10 rpm. Based on the measurement results, the ratio (η1 / η2) of the viscosity at 1 rpm (η1) to the viscosity at 10 rpm (η2) was calculated and used as the TI value. These values ​​were measured after the active energy ray-curable resin composition was produced and then left to stand in an environment of 25°C for one day.

[0088] Aspect Ratio Using a Musashi Engineering dispenser (model ML-6000X), an active energy ray-curable resin composition was adjusted to 25.0°C and then applied to a bead width of 1000µm±100µm using an 18G needle (inner diameter 0.92mm) at a discharge pressure of 30-150kPa and a coating speed of 30mm / s. After UV irradiation, the cross section of the bead was cut and the width and height of the cross section were measured using a microscope (manufactured by Keyence Corporation). The aspect ratio was calculated using the following formula: Aspect Ratio = H / WH: bead height W: bead width. The calculated aspect ratio was evaluated according to the following criteria. A rating of △ or higher was deemed acceptable for practical use. ○: 0.70 or more △: 0.60 to less than 0.70 ×: less than 0.60

[0089] Hardness: The active energy ray-curable resin composition, adjusted to a thickness of 2 mm, was applied to a UV irradiation device (LIGHT HAMMER 6 manufactured by Fusion UV Systems) using a high-pressure mercury lamp as a light source at an illuminance of 300 mW / cm. 23000mJ / cm 2 The cured product was cured by irradiating it with light so that the integrated light intensity was 1000 kJ / cm. The cured product was cut into a size of 2 cm x 3 cm, and five pieces were stacked to prepare a test piece with a thickness of approximately 10 mm. The Shore A hardness of the test piece was then measured using a Type A durometer according to the measurement method in accordance with JIS K6253.

[0090] Reworkability: Using the same equipment and conditions as in the aspect ratio measurement method described above, an active energy ray-curable resin composition was applied to a SUS plate (size: 5 cm x 15 cm) to a width of 1000 ± 150 μm, a height of 750 μm ± 50 μm, and a length of 11 cm. The application was carried out by applying the active energy ray-curable resin composition in two parallel bead shapes with a 2 cm gap between them. Next, using the same UV irradiation equipment and light source as in the hardness measurement described above, the composition was applied to a SUS plate (size: 5 cm x 15 cm) to a width of 1000 ± 150 μm, a height of 750 μm ± 50 μm, and a length of 11 cm. 2 3000mJ / cm 2 The cured product was prepared by irradiating the material with an integrated light intensity of 1000 kJ / cm to obtain a cured product. 5 mm portions were cut off from both ends of the bead-shaped cured product to obtain a length of 10 cm. Next, the bead-shaped cured product was sandwiched between two SUS plates of the same size using a 0.5 mm thick aluminum spacer to obtain a compression ratio of approximately 30%, and then clamped until the SUS plate was tightly attached to the spacer to prepare a test specimen. The test specimen was then exposed to a 70°C oven for 5 hours and then left in a 25°C environment for 19 hours. The clamps were removed and the product was evaluated according to the following criteria. A rating of ○ indicates satisfactory practical use. ○: The SUS plate could be easily peeled off by hand without resistance, and no residue remained on the peeled surface. ×: The adhesive was so strong that the SUS plate could not be peeled off even with manual force.

[0091] Using the same equipment and conditions as in the aspect ratio measurement method described above, an active energy ray-curable resin composition was applied to a peelable PET film so that the bead height was 900 μm±100 μm and the bead length was 10 cm. Then, using a UV light source, the illuminance was 300 mW / cm. 2 3000mJ / cm 2The test specimens were then cured by irradiating the film with an integrated light intensity of 1.5 N to prepare test pieces. The test specimens were then left in a high-temperature, high-humidity chamber set at a temperature of 40°C and a humidity of 95% for 168 hours, after which they were removed and left at room temperature for another day. Using the test specimens, the breaking strength was measured at 23°C ± 2°C using a universal tensile tester (Shimadzu Corporation, Autograph), and the tear resistance to moist heat was evaluated according to the following evaluation criteria. Note that a rating of △ or higher is considered to be satisfactory for practical use. ○: Breaking strength of 1.5 N or more △: Breaking strength of 0.8 N to less than 1.5 N ×: Breaking strength less than 0.8 N

[0092] Dynamic Viscoelasticity (Storage Modulus G', Tanδ Peak Temperature, Tanδ Peak Height) A 2 mm thick silicone rubber sheet formed into a rectangular frame was prepared as a spacer. The spacer was then placed on an aluminum plate that had been treated with a release agent, and an active energy ray-curable resin composition was dropped into the frame of the spacer. Quartz glass was prepared, placed on top of the active energy ray-curable resin composition so that it was in contact with the resin composition, and compressed. In this state, the resin composition was subjected to UV irradiation at an illuminance of 300 mW / cm using the same UV irradiation device and light source as used in the hardness measurement. 2 Accumulated light intensity 3000mJ / cm 2 The UV irradiation was carried out under the conditions of . The quartz glass was peeled off to prepare a sample for measuring dynamic viscoelasticity. Using the sample prepared as described above, dynamic viscoelasticity measurements (heating process) were carried out using a dynamic viscoelasticity measuring device (TA Instruments, Model: HR-10) in rotational shear mode at a frequency of 1 Hz, in the temperature range of -60°C to 70°C, and at a heating rate of 5°C / min. The peak temperature, peak height, and storage modulus G' at 25°C obtained by the measurement were used as the measured values.

[0093] Dischargeability: The same equipment and SUS plate were prepared as in the aspect ratio measurement method described above. The temperature of the active energy ray-curable resin composition was adjusted to 25.0°C, and then the active energy ray-curable resin composition was applied to a length of 11 cm using an 18G nozzle at a dispensing pressure of 150 kPa and a dispensing speed of 30 mm / s, with the gap between the SUS plate and the nozzle tip adjusted to 6.0 mm. The weight of the applied active energy ray-curable resin composition was measured, and this was used as the discharge amount. Dischargeability was evaluated according to the following evaluation criteria. A rating of △ or higher indicates that there is no problem in practical use. ◎: Dispensed amount of 0.3 g or more ○: Dispensed amount of 0.15 to less than 0.3 g △: Dispensed amount of 0.05 to less than 0.15 g ×: Dispensed amount of less than 0.05 g

[0094] Deep curing: An active energy ray-curable resin composition was applied to a release-treated aluminum plate to a thickness of 2.0 mm ± 0.1 mm, and the applied composition was irradiated with the same UV irradiation device and light source as used in the hardness measurement above at an illuminance of 300 mW / cm. 2 , cumulative light intensity 3000mJ / cm 2 The cured product was then peeled off from the aluminum plate, and the cured state on the back side was visually inspected, and the deep curability was evaluated according to the following criteria. A rating of ○ indicates that there is no problem in practical use. ○: No liquid uncured material is observed. ×: Liquid uncured material is observed.

[0095] The results are shown in Table 1. In Table 1, the numerical values ​​for the blending amounts are in parts by mass, with the total of components (A) and (B) being 100 parts by mass.

[0096]

[0097] In Table 1, Comparative Example 3 was rated as × for deep curability, and since it was difficult to obtain a cured product of the active energy ray-curable resin composition, the hardness (Shore A), storage modulus G′, Tan δ peak temperature, and Tan δ peak height could not be measured, and were indicated as “measurable.”

Claims

1. An active energy ray-curable resin composition containing the following components (A), (B), (C), and (D): (A) A urethane acrylate oligomer having a urethane skeleton with an ether bond and a weight average molecular weight of 10,000 or more and less than 40,000; (B) A monofunctional acrylate monomer; (C) A photopolymerization initiator; (D) Fumed silica. The component (C) includes a compound having a benzoyl group. The active energy ray-curable resin composition is irradiated with ultraviolet rays using a high-pressure mercury lamp under the conditions of an illuminance of 300 mW / cm 2 , an integrated light quantity of 3000 mJ / cm 2 . The cured product with a thickness of 2 mm obtained by the ultraviolet irradiation has a storage elastic modulus G' at 25°C of 700,000 Pa or less, a peak temperature of Tanδ of 15°C or less, and a peak height of Tanδ of 1.7 or less, which are measured under the conditions of a rotational shear mode with a vibration frequency of 1 Hz, a temperature increase rate of 5°C / min, and a temperature range of -60°C to 70°C using a dynamic viscoelasticity measuring device. An active energy ray-curable resin composition characterized by the above.

2. The active energy ray-curable resin composition according to claim 1, wherein the component (C) contains (i) methylbenzoyl formate and (ii) a benzophenone compound or an α-hydroxyacetophenone compound.

3. The active energy ray-curable resin composition according to claim 1, wherein the content of the component (A) is 10 to 30% by mass based on 100% by mass of the total content of the component (A) and the component (B).

4. The active energy ray-curable resin composition according to claim 1, wherein the component (B) contains the following component (B1) and component (B2): (B1) phenoxyethyl acrylate (B2) an alkyl acrylate having 8 or 12 carbon atoms or an alkyl acrylate having 9 to 10 carbon atoms with an iso-structure. The content of the component (B2) is 30% by mass or less based on 100% by mass of the total content of the component (B1) and the component (B2).

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