Photocurable composition, sealant, and cured product

Abstract

The present invention provides a photocurable composition which has excellent barrier properties against both water and helium and can retain satisfactory force of adhesion to adherends.　This photocurable composition comprises the following (A) to (D) components, wherein the (B) component and the (C) component are contained in amounts of 1-50 parts by mass and 50-300 parts by mass, respectively, per 100 parts by mass of the (A) component: (A) component is polyisobutylene having a (meth)acryloyl group in the molecule; (B) component is a urethane-modified (meth)acrylate oligomer (excluding the (A) component); (C) component is a (meth)acrylate monomer (excluding the (A) and (B) components); and (D) component is a photoinitiator.

Description

Technical Field

[0001] The present invention relates to a photocurable composition containing a (meth)acrylate compound having a polyisobutylene skeleton.

Background Art

[0002] In the field of hard disk drives, it is known that air turbulence (wind turbulence) occurs due to the high-speed rotation of the disk, etc., and vibrations occur in the disk and the magnetic head. To suppress such problems, for example, a technique of enclosing helium in a housing as disclosed in Japanese Patent Application Laid-Open No. 2008-090886 (corresponding to US Patent Application Publication No. 2008 / 0088969) is widely used. However, there has been a problem that helium leaks out in the case of sealing with a polymer. In response to such a problem, Japanese Patent Application Laid-Open No. 2014-148650 (corresponding to US Patent Application Publication No. 2015 / 0368388) has proposed a technique related to a sealant having good moisture barrier properties. However, such a sealant has a problem in that it has low barrier properties against helium in addition to low adhesive force to the adherend.

Summary of the Invention

Problems to be Solved by the Invention

[0003] As described above, according to the conventional technology, it has been difficult to maintain good adhesion to the adherend while obtaining good barrier properties against both moisture and helium in a photocurable sealant.

[0004] Therefore, an object of the present invention is to provide a photocurable composition that is excellent in barrier properties against both moisture and helium and can maintain good adhesion to the adherend. Another object of the present invention is to provide a sealant using the above photocurable composition and a cured product obtained by curing the above photocurable composition.

Means for Solving the Problems

[0005] As a result of intensive studies to achieve the above object, the present inventors have found that the photocurable composition described in detail below is excellent in barrier properties against both moisture and helium and can maintain good adhesion to an adherend, and thus have completed the present invention.

[0006] The gist of the present invention will be described below. A first embodiment of the present invention is a photocurable composition containing the following components (A) to (D), and containing 1 to 50 parts by mass of the following component (B) and 50 to 300 parts by mass of the following component (C) with respect to 100 parts by mass of the following component (A): Component (A): Polyisobutylene having a (meth)acryloyl group in the molecule Component (B): Urethane-modified (meth)acrylate oligomer (excluding component (A)) Component (C): (Meth)acrylate monomer (excluding components (A) and (B)) Component (D): Photoinitiator.

[0007] A second embodiment of the present invention is the photocurable composition according to the first embodiment, containing 10 to 30 parts by mass of the component (B) with respect to 100 parts by mass of the component (A).

[0008] A third embodiment of the present invention is the photocurable composition according to the first or second embodiment, containing 100 to 200 parts by mass of the component (C) with respect to 100 parts by mass of the component (A).

[0009] A fourth embodiment of the present invention is the photocurable composition according to any one of the first to third embodiments, wherein the component (A) contains polyisobutylene having an aromatic hydrocarbon group in the molecule.

[0010] A fifth embodiment of the present invention is the photocurable composition according to any one of the first to fourth embodiments, wherein the component (C) contains a (meth)acrylate monomer having a structure of the following formula (C-1).

[0011] The sixth embodiment of the present invention further includes a filler as component (E), and contains 0.1 to 50 parts by mass of the component (E) with respect to 100 parts by mass of the component (A), and is the photocurable composition according to any one of the first to fifth embodiments.

[0012] The seventh embodiment of the present invention is the photocurable composition according to any one of the first to sixth embodiments, wherein the component (B) is a urethane-modified (meth)acrylate oligomer not containing a rubber skeleton.

[0013] The eighth embodiment of the present invention is a sealant containing the photocurable composition according to any one of the first to seventh embodiments.

[0014] The ninth embodiment of the present invention is the sealant according to the eighth embodiment, which is used for a hard disk drive.

[0015] The tenth embodiment of the present invention is a cured product obtained by curing the photocurable composition according to any one of the first to seventh embodiments by light irradiation.

Brief Description of Drawings

[0016]

Figure 1

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described. It should be noted that the present disclosure is not limited only to the following embodiments.

[0018] In this specification, "X to Y" indicating a range means a range including the lower limit value (X) and the upper limit value (Y). Concentration and %, unless otherwise specified, represent mass concentration and mass %, respectively, and the ratio is a mass ratio unless otherwise specified. Also, unless otherwise noted, measurements of operations and physical properties were carried out under the conditions of room temperature (20 to 25 °C) / relative humidity 40 to 50%RH, but are not limited to this condition. Further, "A and / or B" includes each of A and B and all combinations of one or more, specifically, means at least one of A and B, and means A, B, and the combination of A and B.

[0019] [Photocurable composition] The photocurable composition according to one embodiment of the present invention (hereinafter, also referred to as "photocurable composition" or simply "composition") contains the following components (A) to (D), and with respect to 100 parts by mass of the following component (A), contains 1 to 50 parts by mass of the following component (B) and 50 to 300 parts by mass of the following component (C), and is a photocurable composition: Component (A): Polyisobutylene having a (meth)acryloyl group in the molecule Component (B): Urethane-modified (meth)acrylate oligomer (excluding component (A)) Component (C): (Meth)acrylate monomer (excluding component (A) and component (B)) Component (D): Photoinitiator.

[0020] The photocurable composition according to one embodiment of the present invention is excellent in barrier properties against both moisture and helium, and can maintain good adhesion to the adherend. Specifically, the photocurable composition according to one embodiment of the present invention not only has a low water vapor transmission coefficient as a measure of moisture barrier properties and a low helium transmission coefficient as a measure of helium barrier properties, but also has good adhesion to the adherend.

[0021] <(Component (A))> The component (A) contained in the composition according to the present invention is a polyisobutylene having one or more (meth)acryloyl groups in the molecule. The polyisobutylene refers to a polymer having a polyisobutylene skeleton containing a repeating unit represented by the following formula (A-1). In the present specification, the "polyisobutylene skeleton containing a repeating unit represented by the following formula (A-1)" is also simply referred to as the "polyisobutylene skeleton". Further, in the present specification, the term "(meth)acryloyl" includes both acryloyl and methacryloyl. Therefore, for example, the term "(meth)acryloyl group" includes both an acryloyl group (H2C=CH-C(=O)-) and a methacryloyl group (H2C=C(CH3)-C(=O)-). Similarly, the term "(meth)acrylic" includes both acrylic and methacrylic.

[0022]

Chemical formula

[0023] Further, in the present specification, the "polymer" is not limited by theory, and refers to, for example, a compound having a structure with repeating units of monomers in the molecule, such as a main chain, and having two or more repeating units.

[0024] The polyisobutylene as the component (A) is not particularly limited as long as it is a polymer having one or more (meth)acryloyl groups and a polyisobutylene skeleton. Further, regarding the component (A) that can be used in the present invention, a compound having a urethane bond in addition to one or more (meth)acryloyl groups and a polyisobutylene skeleton is included in the component (A) and not included in the component (B).

[0025] In a preferred embodiment, the polyisobutylene as component (A) contains the polyisobutylene skeleton as a block. Further, in a preferred embodiment, in the above formula (A-1), n is 2 or more. The composition according to the present invention is presumed to have low water permeability due to the polyisobutylene skeleton contained in component (A). Here, from the viewpoint of further improving the barrier properties and adhesiveness to water and helium, in the above formula (A-1), n is preferably from 2 to 300, more preferably from 10 to 150, and particularly preferably from 20 to 100.

[0026] The polyisobutylene as component (A) may contain other constitutional units other than the repeating unit represented by formula (A-1). When the polyisobutylene as component (A) contains the above other constitutional units, a diblock or triblock may be formed together with a block formed by polymerizing the other constitutional units. That is, the polyisobutylene may be in a form (diblock) further containing a block formed by polymerizing other constitutional units (polymerizable monomers) in addition to the block composed of the repeating unit represented by formula (A-1). Further, the polyisobutylene may be in a form (triblock) containing two blocks formed by polymerizing other constitutional units (polymerizable monomers) in addition to the block composed of the repeating unit represented by formula (A-1). Among them, the polyisobutylene preferably does not contain a block derived from other polymerizable monomers and is a monoblock containing only a block composed of the repeating unit represented by formula (A-1).

[0027] Here, from the viewpoint of making it easier to obtain a cured product (improving the curability) by introducing a rigid skeleton, component (A) preferably contains polyisobutylene having an aromatic hydrocarbon group. By using polyisobutylene having an aromatic hydrocarbon group, when the composition is cured, a decrease in curability due to the flexibility of the polyisobutylene skeleton can be suppressed.

[0028] The above aromatic hydrocarbon group may be contained in either the main chain or the side chain of polyisobutylene as the component (A). From the viewpoint of improving the curability of the composition, the aromatic hydrocarbon group is preferably contained between the polyisobutylene skeleton and the (meth)acryloyl group.

[0029] The aromatic hydrocarbon ring contained in the aromatic hydrocarbon group is not particularly limited. For example, benzene ring, biphenyl ring, naphthalene ring, pentalene ring, indene ring, anthracene ring, azulene ring, fluorene ring, heptalene ring, acenaphthalene ring, phenalene ring, phenanthrene ring, triphenylene ring, pyrene ring, chrysene ring, picene ring, perylene ring, pentaphene ring, pentacene ring, tetraphene ring, hexaphene ring, hexacene ring, etc. can be mentioned. Considering the availability, it is preferably a benzene ring or a naphthalene ring, and particularly preferably a benzene ring. That is, the aromatic hydrocarbon group is preferably a group derived from the above aromatic hydrocarbon ring.

[0030] Furthermore, from the viewpoint of improving the curability of the composition, polyisobutylene preferably contains a divalent aromatic hydrocarbon group. Here, as the divalent aromatic hydrocarbon group, an aromatic hydrocarbon group having 6 to 30 carbon atoms is preferable. For example, it is preferably a phenylene group, a biphenylene group, a naphthylene group, an anthrylene group, a fluorenylene group, a phenanthrylene group, or a pyrenylene group, more preferably a phenylene group, a biphenylene group, a naphthylene group, an anthrylene group, or a fluorenylene group, and particularly preferably a phenylene group.

[0031] In addition, the aromatic hydrocarbon group may be substituted. At this time, the substituent is not particularly limited, and examples thereof include a monovalent hydrocarbon group having 1 to 20 carbon atoms and an alkoxy group having 1 to 20 carbon atoms. Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, an isopentyl group, a neopentyl group, a hexyl group, an isohexyl group, a neohexyl group, a heptyl group, an octyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, a 2-ethylhexyl group, a nonyl group, a decanyl group, and the like. Examples of the alkoxy group having 1 to 20 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group, an isopentyloxy group, a neopentyloxy group, a hexyloxy group, an isohexyloxy group, a neohexyloxy group, a heptyloxy group, an octyloxy group, an isooctyloxy group, a sec-octyloxy group, a tert-octyloxy group, a 2-ethylhexyloxy group, a nonyloxy group, and the like.

[0032] The polyisobutylene as the component (A) preferably contains two or more (meth)acryloyl groups in the compound. From the viewpoint of curability, the number of (meth)acryloyl groups contained in the polyisobutylene is preferably 1 to 12, more preferably 2 to 8, still more preferably 2 to 4, and particularly preferably 2. Further, the (meth)acryloyl group may be present in either the side chain and / or the terminal of the molecule, but from the viewpoint of rubber elasticity, it is preferably present at the terminal of the molecule. Furthermore, from the viewpoint of curability, the polyisobutylene as the component (A) preferably has one or more acryloyl groups in one molecule, more preferably has 1 to 12 acryloyl groups, still more preferably has 2 to 8 acryloyl groups, still more preferably has 2 to 4 acryloyl groups, and particularly preferably has 2 acryloyl groups.

[0033] (A) The molecular weight of polyisobutylene as a component is not particularly limited, but from the viewpoint of excellent adhesiveness, the number average molecular weight is preferably 200 to 500,000, more preferably 500 to 400,000, even more preferably 1,000 to 100,000, and particularly preferably 3,000 to 50,000. In this specification, the number average molecular weight and the weight average molecular weight are values calculated by the standard polystyrene conversion method using Gel Permeation Chromatography (GPC).

[0034] (A) The component may be used alone or in combination of two or more. When two or more are used in combination, the content of the (A) component refers to the total amount.

[0035] (A) Polyisobutylene as a component may be either a commercially available product or a synthetic product. The production method of the (A) component is not limited, and it can be produced by the production methods such as JP-A-2013-35901, JP-A-2013-216782, Re-Published 2013-047314 (corresponding to US Patent Application Publication No. 2014 / 243444), WO2017 / 099043 (corresponding to US Patent Application Publication No. 2018 / 362676), etc.

[0036] Specific examples of commercially available products of the (A) component include EPION (registered trademark) series EP400V manufactured by Kaneka Corporation, but are not limited thereto.

[0037] In addition, in order to reduce the permeability of inert gases such as helium, the photocurable composition according to one embodiment of the present invention preferably substantially does not contain compounds having a rubber skeleton such as polybutadiene, hydrogenated polybutadiene, polyisoprene rubber, and hydrogenated polyisoprene, other than the component (A). In the present specification, "substantially does not contain" means that the composition includes a mode in which the target substance is contained by contamination, but the target substance may be present in a proportion of 0.1% by mass or less (lower limit: 0% by mass) with respect to the total amount of the composition. Further, in the present specification, the "rubber skeleton" refers to a structure contained in rubber molecules such as polybutadiene, hydrogenated polybutadiene, polyisoprene rubber, hydrogenated polyisoprene, or styrene copolymers thereof.

[0038] <Component (B)> The component (B) contained in the composition according to the present invention is a urethane-modified (meth)acrylate oligomer, provided that the component (A) is excluded. The composition according to the present invention contains 1 to 50 parts by mass of the component (B) with respect to 100 parts by mass of the component (A). When the content of the component (B) with respect to 100 parts by mass of the component (A) is less than 1 part by mass, when the composition is used to adhere to an adherend, the sealing property at the interface becomes a problem, which is not preferable from the viewpoint of adhesiveness. That is, the adhesive force cannot be maintained. On the other hand, when the content of the component (B) with respect to 100 parts by mass of the component (A) exceeds 50 parts by mass, the permeability of helium increases. Further, separation from the component (A) becomes a problem.

[0039] (B) The urethane-modified (meth)acrylate oligomer as a component is a (meth)acrylate oligomer ((meth)acryloyl group-containing oligomer) having one or more urethane bonds (-NH-C(=O)-O-). The (meth)acrylate oligomer is an oligomer having one or more (meth)acryloyl groups. In the present specification, the "oligomer" refers to those having a weight average molecular weight exceeding 1,000. The weight average molecular weight of component (B) is preferably more than 1,000 and 200,000 or less, more preferably 5,000 to 100,000, and particularly preferably 10,000 to 50,000. Within such a range, the adhesiveness can be further enhanced.

[0040] (B) From the viewpoint of improving adhesiveness, the urethane-modified (meth)acrylate oligomer as a component preferably has 2 to 10 (meth)acryloyl groups in one molecule, more preferably has 2 to 8 (meth)acryloyl groups, even more preferably has 2 to 4 (meth)acryloyl groups, and most preferably has 2 (meth)acryloyl groups (bifunctional (meth)acrylate oligomer). Also, from the same viewpoint, component (B) is preferably an acrylate oligomer having one or more acryloyl groups in one molecule. Further from the same viewpoint, the urethane-modified (meth)acrylate oligomer as a component preferably has 2 to 10 acryloyl groups in one molecule, more preferably has 2 to 8 acryloyl groups, even more preferably has 2 to 4 acryloyl groups, and particularly preferably has 2 acryloyl groups (bifunctional acrylate oligomer).

[0041] Examples of the main skeleton of the urethane-modified (meth)acrylate oligomer include an ester bond, an ether bond, a carbonate bond, and the like. Urethane-modified (meth)acrylate oligomers having these main skeletons can be obtained, for example, by forming a urethane bond through the reaction of a polyester polyol, a polyether polyol, or a polycarbonate polyol serving as the main skeleton with a polyisocyanate, and further adding acrylic acid or a compound having a hydroxyl group and a (meth)acryloyl group to the unreacted isocyanate groups. However, the synthesis method is not limited to these. From the viewpoint of improving adhesiveness, the main skeleton of the urethane-modified (meth)acrylate oligomer is preferably polyester, polyether, or polycarbonate, and particularly preferably polyether. That is, from the viewpoint of improving adhesiveness, the composition according to the present invention preferably contains, as the component (B), a urethane-modified (meth)acrylate oligomer having a polyether skeleton, and more preferably contains a urethane-modified acrylate oligomer having a polyether skeleton.

[0042] In a more preferred embodiment, from the viewpoint of improving the barrier property of helium, the urethane-modified (meth)acrylate oligomer as the component (B) is preferably a urethane-modified (meth)acrylate oligomer not containing a rubber skeleton.

[0043] (B) component, the urethane-modified (meth) acrylate oligomer, may be either a commercially available product or a synthetic product. Specific examples of commercially available products of the (B) component include AH-600, AT-600, UA-306H, UF-8001G, etc. manufactured by Kyoeisha Chemical Co., Ltd.; UN-6200, UN-6202, UN-6300, UN-6301 manufactured by Negami Kogyo Co., Ltd. and the Violet Light (registered trademark) series UV-2000B, UV-3300B, UV-3700B, etc. manufactured by Mitsubishi Chemical Corporation as urethane-modified (meth) acrylate oligomers having a polyether backbone; UN-7600, UN-7700, etc. manufactured by Negami Kogyo Co., Ltd. as urethane-modified (meth) acrylate oligomers having a polyester backbone; UN-9000PEP, UN-9200A, etc. manufactured by Negami Kogyo Co., Ltd. as urethane-modified (meth) acrylate oligomers having a polycarbonate backbone; although not limited thereto.

[0044] The composition according to the present invention contains 1 to 50 parts by mass of the (B) component with respect to 100 parts by mass of the (A) component. In a more preferred form, the composition according to the present invention contains 10 to 30 parts by mass of the (B) component with respect to 100 parts by mass of the (A) component. In an even more preferred form, the composition according to the present invention contains 15 to 25 parts by mass of the (B) component with respect to 100 parts by mass of the (A) component. In the composition according to the present invention, when the (B) component is contained in an amount of 1 part by mass or more, 10 parts by mass or more, and further 15 parts by mass or more with respect to 100 parts by mass of the (A) component, good adhesive strength can be maintained. Also, in the composition according to the present invention, when the (B) component is contained in an amount of 50 parts by mass or less, 30 parts by mass or less, and further 25 parts by mass or less with respect to 100 parts by mass of the (A) component, separation from the (A) component can be effectively suppressed.

[0045] (B) component may be used alone or in combination of two or more. When a plurality of (B) components are included, the total amount thereof is within the above range.

[0046] <(C) component> The component (C) contained in the composition according to the present invention is a (meth)acrylate monomer, provided that the components (A) and (B) are excluded. The composition according to the present invention contains 50 to 300 parts by mass of the component (C) with respect to 100 parts by mass of the component (A). When the content of the component (C) with respect to 100 parts by mass of the component (A) is less than 50 parts by mass, the viscosity becomes high as a photocurable composition, which is not preferable from the viewpoint of workability. On the other hand, when the content of the component (C) with respect to 100 parts by mass of the component (A) exceeds 300 parts by mass, separation from the component (A) becomes a problem.

[0047] The (meth)acrylate monomer as the component (C) is an ester monomer having one or more (meth)acryloyl groups. The molecular weight of the component (C) is not particularly limited, but considering the dilution of the components (A) and (B), the molecular weight of the component (C) is preferably 1000 or less, more preferably 500 or less, and particularly preferably 400 or less. Further, from the viewpoint of excellent compatibility with the component (A), the molecular weight of the component (C) is preferably 80 or more, more preferably 100 or more, and particularly preferably 150 or more. The molecular weight of the component (B) can be measured by a known method such as gas chromatography-mass spectrometry (GC-MS). Further, the structure of the component (B) can be specified by a method such as NMR, and the molecular weight can be specified by performing calculations based on the structure.

[0048] The (meth)acrylate monomer as the component (C) preferably has 1 to 3 (meth)acryloyl groups (that is, a 1- to 3-functional (meth)acrylate monomer). Further, from the viewpoint of excellent compatibility with the component (A), the component (C) preferably contains a monofunctional (mono-functional) (meth)acrylate monomer, and more preferably contains a monofunctional acrylate monomer.

[0049] Specific examples of the monofunctional (meth)acrylate monomer as the (C) component include lauryl (meth)acrylate, isononyl (meth)acrylate, isooctyl (meth)acrylate, stearyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ethyl carbitol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, butoxyethyl (meth)acrylate, butoxytriethylene glycol (meth)acrylate, 2-ethylhexyl polyethylene glycol (meth)acrylate, methoxydipropylene glycol (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, glycerol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, ethylene oxide-modified succinic acid (meth)acrylate, caprolactone-modified 2-hydroxyethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, etc. (meth)acrylates having a chain structure; (meth)acrylates having an alicyclic structure such as cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate; (meth)acrylates having an aromatic ring structure such as benzyl (meth)acrylate, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxytetraethylene glycol (meth)acrylate, nonylphenoxyethyl (meth)acrylate, nonylphenoxytetraethylene glycol (meth)acrylate, nonylphenyl polypropylene glycol (meth)acrylate, nonylphenol EO-modified (meth)acrylate (n≈1), ethylene oxide-modified phthalic acid (meth)acrylate; (meth)acrylates having a heterocyclic structure such as tetrahydrofurfuryl (meth)acrylate, caprolactone-modified tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, morpholinoethyl (meth)acrylate;Examples include, but are not limited to, ethylene oxide-modified phosphoric (meth)acrylate and the like.

[0050] Specific examples of the bifunctional (meth)acrylate monomer as the component (C) include (meth)acrylates having a chain structure such as 1,3-butylene glycol di(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, ethylene oxide-modified neopentyl glycol di(meth)acrylate, propylene oxide-modified neopentyl glycol di(meth)acrylate, hydroxypivalic acid ester neopentyl glycol di(meth)acrylate, caprolactone-modified hydroxypivalic acid ester neopentyl glycol di(meth)acrylate, neopentyl glycol-modified trimethylolpropane di(meth)acrylate, stearic acid-modified pentaerythritol di(meth)acrylate; (meth)acrylates having an alicyclic structure such as dimethyloltricyclodecane di(meth)acrylate, dicyclopentenyl di(meth)acrylate, ethylene oxide-modified dicyclopentenyl di(meth)acrylate; (meth)acrylates having an aromatic ring structure such as bisphenol A di(meth)acrylate, ethylene oxide-modified bisphenol A di(meth)acrylate, ethylene oxide-modified bisphenol S di(meth)acrylate; (meth)acrylates having a heterocyclic structure such as dimethacryloyl isocyanurate; and the like. Examples include, but are not limited to, these.

[0051] Specific examples of the trifunctional (meth)acrylate monomer as the component (C) include (meth)acrylates having a chain structure such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, and propylene oxide-modified trimethylolpropane tri(meth)acrylate; (meth)acrylates having a heterocyclic structure such as tris(methacryloyloxyethyl) isocyanurate; and the like, but are not limited thereto.

[0052] From the viewpoint of reducing the viscosity of the resulting composition and easily controlling it within a suitable viscosity range, the composition according to the present invention preferably contains, as the component (C), at least one selected from the group consisting of monofunctional to trifunctional (meth)acrylate monomers having a chain structure, monofunctional to trifunctional (meth)acrylate monomers having an alicyclic structure, monofunctional to trifunctional (meth)acrylate monomers having an aromatic ring structure, and monofunctional to trifunctional (meth)acrylate monomers having a heterocyclic structure. From the same viewpoint, it is more preferable that the composition contains, as the component (C), at least one selected from the group consisting of monofunctional (meth)acrylate monomers having a chain structure, monofunctional (meth)acrylate monomers having an alicyclic structure, monofunctional (meth)acrylate monomers having an aromatic ring structure, and monofunctional (meth)acrylate monomers having a heterocyclic structure. Further from the same viewpoint, it is more preferable that the component (C) contains at least one selected from the group consisting of monofunctional acrylate monomers having a chain structure, monofunctional acrylate monomers having an alicyclic structure, monofunctional acrylate monomers having an aromatic ring structure, and monofunctional acrylate monomers having a heterocyclic structure.

[0053] In the present specification, the "(meth)acrylate monomer having a chain structure" refers to a (meth)acrylate monomer having no cyclic structure. The "chain structure" includes a linear structure and a branched-chain structure. Further, the "(meth)acrylate monomer having an alicyclic structure" refers to a (meth)acrylate monomer having a cyclic hydrocarbon group. Examples of the alicyclic structure include monocyclic cycloalkyl groups such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, methylcyclohexyl group, dimethylcyclohexyl group, etc.; monocyclic cycloalkenyl groups such as cyclobutenyl group, cyclopentenyl group, cyclohexenyl group, etc.; polycyclic cycloalkyl groups such as hydronaphthyl group, 1-adamantyl group, 2-adamantyl group, norbornyl group, methylnorbornyl group, isobornyl group, dicyclopentanyl group, tricyclodecyl group, tetracyclododecyl group, etc.; polycyclic cycloalkenyl groups such as dicyclopentenyl group, dicyclopentenyl oxyethyl group, etc.; and the like, but are not limited thereto.

[0054] More preferably, the component (C) includes monofunctional acrylate monomers having a chain hydrocarbon group (structure) such as isononyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, etc.; monofunctional acrylate monomers having an alicyclic structure such as isobornyl acrylate, dicyclopentanyl acrylate, etc.; monofunctional (meth)acrylate monomers having an aromatic ring structure represented by the following formula (C-1) such as nonylphenol EO-modified acrylate (n≈1), paracumylphenol EO-modified acrylate (n≈1.2), etc.; monofunctional acrylate monomers having a heterocyclic structure such as tetrahydrofurfuryl acrylate, etc.; but are not limited thereto.

[0055] [Chemical formula]

[0056] (In the above formula (C-1), R 1 is hydrogen or a methyl group, R 2is a hydrocarbon group having 1 to 20 carbon atoms, and n is an integer of 0 to 10.) In the above formula (C-1), R 1 is preferably hydrogen. Further, R 2 is preferably a hydrocarbon group having 5 to 10 carbon atoms. The hydrocarbon group as R 2 includes, for example, saturated hydrocarbon groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, isononyl group, decyl group, undecyl group, dodecyl group (lauryl group), tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group (stearyl group); unsaturated hydrocarbon groups such as vinyl group, 1-propenyl group, allyl group, 1-butenyl group, 3-butenyl group, isoprenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group; aromatic hydrocarbon groups such as phenyl group, naphthyl group, biphenyl group, fluorenyl group. Further, these substituents may be further substituted by one or more different arbitrary substituents. However, the above arbitrary substituents do not substitute the same kind of substituents. For example, the arbitrary substituents that substitute the aromatic hydrocarbon group do not include the aromatic hydrocarbon group. Among them, R 2 is preferably a saturated hydrocarbon group having 5 to 10 carbon atoms.

[0057] As a preferred embodiment, the composition according to the present invention contains, as component (C), at least one selected from the group consisting of isononyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isobornyl acrylate, dicyclopentanyl acrylate, nonylphenol EO-modified acrylate (n≈1) represented by the above formula (C-1), para-cumylphenol EO-modified acrylate (n≈1.2), and tetrahydrofurfuryl acrylate. As a more preferred embodiment, the composition according to the present invention contains, as component (C), at least one selected from the group consisting of isononyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isobornyl acrylate, dicyclopentanyl acrylate, nonylphenol EO-modified acrylate (n≈1) represented by the above formula (C-1), para-cumylphenol EO-modified acrylate (n≈1.2), and tetrahydrofurfuryl acrylate. By adopting such a form, good barrier properties against both moisture and helium can be exhibited. As a particularly preferred embodiment, the composition according to the present invention contains, as component (C), nonylphenol EO-modified acrylate (n≈1) represented by the above formula (C-1) and tetrahydrofurfuryl acrylate. By adopting such a form, the barrier property against helium is particularly improved.

[0058] Also, from the viewpoint of reducing outgassing discharged from the cured product, component (C) preferably contains a (meth)acrylate monomer represented by the above formula (C-1). From the same viewpoint, component (C) more preferably contains an acrylate monomer (R 1 is hydrogen) represented by the above formula (C-1). More preferred forms of R 1 and n in the (meth)acrylate monomer represented by the above formula (C-1) are as described above.

[0059] As the (meth)acrylate monomer as the component (C), either a commercially available product or a synthetic product may be used. Specific product names of commercially available products of the component (C) include INAA and IBXA manufactured by Osaka Organic Chemical Industry Co., Ltd.; SR440 manufactured by Arkema Co., Ltd.; 2-ethylhexyl acrylate manufactured by Mitsubishi Chemical Corporation; Aronix (registered trademark) M-111, M-110, and 2-ethylhexyl acrylate manufactured by Toagosei Co., Ltd.; Funcrile (registered trademark) FA-513AS manufactured by Showa Denko Materials Co., Ltd., etc., but are not limited thereto.

[0060] The composition according to the present invention contains 50 to 300 parts by mass of the component (C) with respect to 100 parts by mass of the component (A). In a more preferred form, the composition according to the present invention contains 100 to 200 parts by mass of the component (C) with respect to 100 parts by mass of the component (A). In an even more preferred form, the composition according to the present invention contains 130 to 180 parts by mass of the component (C) with respect to 100 parts by mass of the component (A). In the composition according to the present invention, since the component (C) is contained in an amount of 50 parts by mass or more, 100 parts by mass or more, and further 130 parts by mass or more with respect to 100 parts by mass of the component (A), the viscosity can be lowered as a photocurable composition. Further, in the composition according to the present invention, since the component (C) is contained in an amount of 300 parts by mass or less, 200 parts by mass or less, and further 180 parts by mass or less with respect to 100 parts by mass of the component (A), separation from the component (A) can be effectively suppressed.

[0061] The component (C) may be used alone or in combination of two or more. When a plurality of the component (C) is contained, the total amount thereof is within the above range.

[0062] <(Component (D))> The component (D) contained in the composition according to the present invention is a photoinitiator (photopolymerization initiator). A photoinitiator is a compound (photo radical polymerization initiator) that decomposes upon irradiation with light to generate radical species, and is used for radical polymerization of the components (A) to (C).

[0063] Photoinitiators as component (D) include, for example, dimethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, diethoxyacetophenone, acetophenone, propiophenone, benzophenone, xanthone, fluorein, benzaldehyde, anthraquinone, triphenylamine, 2,2-dimethoxy-1,2-diphenylethane-1-one, carbazole, 2-hydroxy-2-methylphenyl propan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 3-methylacetophenone, 4-methylacetophenone, 3-pentylacetophenone, 4-methoxyacetophenone, 3-bromoacetophenone, p-diacetylbenzene, 3-methoxybenzophenone, 4-allylacetophenone, 4-methylbenzophenone, 4-chloro-4-benzylbenzophenone, 3-chloroxanthone, 3,9-dichloroxanthone, 3-chloro-8-nonylxanthone, benzoyl, benzoin methyl ether, benzoin butyl ether, bis(4-dimethylaminophenyl)ketone, benzyl methyl ketal, 2-chlorothioxanthone, etc.; oligomer / polymer type photoinitiators such as 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone oligomer, polymer of 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone (n = 2 to 10), etc., but are not limited thereto.

[0064] Among them, from the viewpoint of reducing outgas generated from the cured product, component (D) preferably contains an oligomer / polymer type photoinitiator.

[0065] (D) As the photoinitiator, either a commercially available product or a synthetic product may be used. Specific examples of commercially available products of component (D) include oligomer-type polymerization initiators (oligomer / polymer-type photoinitiators) in which α-hydroxypropiophenone typified by ESACURE® KIP-150 manufactured by IGM Resins B.V. is bonded to the side chain, but are not limited thereto.

[0066] The composition according to the present invention preferably contains 0.1 to 10 parts by mass of component (D) with respect to 100 parts by mass of component (A). In a more preferred form, the composition according to the present invention contains 1.0 to 5.0 parts by mass of component (D) with respect to 100 parts by mass of component (A). In an even more preferred form, the composition according to the present invention contains more than 3.0 parts by mass and less than 5.0 parts by mass of component (D) with respect to 100 parts by mass of component (A). In the composition according to the present invention, when component (D) is contained in an amount of 0.1 part by mass or more, 1.0 part by mass or more, and further more than 3.0 parts by mass with respect to 100 parts by mass of component (A), optimal handleability is exhibited. Also, in the composition according to the present invention, when component (D) is contained in an amount of 10 parts by mass or less, 5.0 parts by mass, and further less than 5.0 parts by mass with respect to 100 parts by mass of component (A), good curability can be maintained.

[0067] (D) Component may be used alone or in combination of two or more. When a plurality of components (D) are contained, it is preferable that the total amount is within the above range.

[0068] <(E) component> The composition according to the present invention preferably further contains a filler as component (E) in addition to the above components (A) to (D). As the filler as component (E), those known in the art can be used, but among them, the filler is preferably amorphous silica having silanol groups remaining on the surface. That is, the filler as component (E) is preferably amorphous silica having silanol groups on the surface. Further, the amorphous silica has an average primary particle diameter of 1 to 100 nm and a specific surface area by the BET method of 10 to 300 m 2It is preferably hydrophilic silica powder (particles) with a specific surface area of 2 / g. More preferably, the amorphous silica has an average primary particle diameter of 5 to 30 nm and a specific surface area of 150 to 250 m 2 / g as hydrophilic silica powder (particles). In this specification, the average primary particle diameter is the value measured from the scanning electron microscope image of the measurement object using image analysis software or the like. Specifically, a predetermined number of particles with statistical reliability (for example, a total of 1000 or more, 100 particles per field of view × 10 or more surfaces) are observed, and particle images are extracted using analysis software to calculate the particle diameter.

[0069] After the production of amorphous silica, although silanol groups remain on its surface, there are compounds in which side chains are added to the silanol groups by various surface treatments. However, in the present invention, amorphous silica with silanol groups remaining on the surface (that is, surface-untreated amorphous silica) is suitable as the (E) component. According to such a form, it is possible to suppress the surface treatment agent from remaining and becoming outgassed. Further, according to the above form, the (E) component can contribute to the compatibility of a lower viscosity and a higher structure viscosity ratio and the stabilization by combining with the (A) to (C) components. In particular, the (A) component has a low polarity or is non-polar, while the surface-untreated amorphous silica has a polarity. Therefore, it is also preferable in that by using surface-untreated amorphous silica as a filler, the (A) component and the filler are less likely to mix with each other, and thixotropy suitable for the resulting composition can be imparted.

[0070] As the filler as the (E) component, either a commercially available product or a synthetic product may be used. Specific examples of commercially available products of the (E) component include, but are not limited to, AEROSIL (registered trademark) series OX50, 50, 90G, 130, 150, 200, 300, 380 manufactured by Nippon Aerosil Co., Ltd.

[0071] When the composition according to the present invention contains the component (E), it preferably contains 0.1 to 50 parts by mass of the component (E) with respect to 100 parts by mass of the component (A). In a more preferred form, the composition according to the present invention contains 1 to 30 parts by mass of the component (E) with respect to 100 parts by mass of the component (A). In an even more preferred form, the composition according to the present invention contains 5 to 25 parts by mass of the component (E) with respect to 100 parts by mass of the component (A). In the most preferred form, the composition according to the present invention contains the component (E) in an amount of 15 parts by mass or more and less than 25 parts by mass with respect to 100 parts by mass of the component (A). In the composition according to the present invention, when the component (E) is contained in an amount of 0.1 part by mass or more, 1 part by mass or more, 5 parts by mass or more, and further 15 parts by mass or more with respect to 100 parts by mass of the component (A), a high structure-viscosity ratio can be maintained. Also, in the composition according to the present invention, when the component (E) is contained in an amount of 50 parts by mass or less, 30 parts by mass or less, 25 parts by mass or less, and further less than 25 parts by mass with respect to 100 parts by mass of the component (A), the handleability is good, which is preferable.

[0072] (E) component may be used alone or in combination of two or more. When a plurality of (E) components are included, it is preferable that the total amount is within the above range.

[0073] <Organic peroxide> The photocurable composition according to the present invention may further contain an organic peroxide in addition to the above components (A) to (D) as long as the properties of the present invention are not impaired. When irradiated with light, the shaded areas not exposed to light may remain as uncured portions. However, since the composition contains an organic peroxide, it becomes easier to cure the uncured portions by heating, which is preferable. Specific examples of the organic peroxide include ketone peroxides such as methyl ethyl ketone peroxide, cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, methyl acetoacetate peroxide, and acetylacetone peroxide; peroxyketals such as 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)octane, n-butyl-4,4-bis(t-butylperoxy)valerate, and 2,2-bis(t-butylperoxy)butane; hydroperoxides such as t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, p-menthane hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, and 1,1,3,3-tetramethylbutyl hydroperoxide; dialkyl peroxides such as di-t-butyl peroxide, t-butyl cumyl peroxide, dicumyl peroxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3; diacyl peroxides such as acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, succinic acid peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, and m-toluoyl peroxide;Peroxydicarbonates such as diisopropyl peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, di(n-propyl) peroxydicarbonate, bis(4-t-butylcyclohexyl) peroxydicarbonate, dimyristyl peroxydicarbonate, di(2-ethoxyethyl) peroxydicarbonate, dimethoxyisopropyl peroxydicarbonate, di(3-methyl-3-methoxybutyl) peroxydicarbonate, diallyl peroxydicarbonate; peroxyesters such as t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxypivalate, t-butyl peroxyneodecanoate, cumyl peroxyneodecanoate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxylaurate, t-butyl peroxybenzoate, di-t-butyl peroxyisophthalate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butyl peroxymaleic acid, t-butyl peroxyisopropyl carbonate, cumyl peroxy octoate, t-hexyl peroxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxyneohexanoate, t-hexyl peroxyneohexanoate, cumyl peroxyneohexanoate; and acetylcyclohexylsulfonyl peroxide, t-butyl peroxyallyl carbonate, etc. are included, but are not limited thereto.;

[0074] The content of the organic peroxide is not particularly limited and can be appropriately set by those skilled in the art within a range that does not impair the characteristics of the present invention. Further, the organic peroxide may be used alone or in combination of two or more kinds.;

[0075] <Plasticizer> The photocurable composition according to the present invention may contain a non-reactive plasticizer in addition to the above components (A) to (D) within a range that does not impair the characteristics of the present invention. Here, "non-reactive" means not reacting with the components (A), (B), and (C) of the present invention to polymerize.;

[0076] Specific examples of non-reactive plasticizers include, as polycarboxylic acid ester plasticizers, aromatic polycarboxylic acid esters; as phthalic acid ester plasticizers, dioctyl phthalate (DOP), dibutyl phthalate (DBP), diheptyl phthalate (DHP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), butyl benzyl phthalate (BBP), etc.; as trimellitic acid ester plasticizers, trioctyl trimellitate (TOTM), triisodecyl trimellitate (TITM), etc.; as pyromellitic acid ester plasticizers, tetraoctyl pyromellitate, etc.; as aliphatic polycarboxylic acid ester plasticizers, di-2-ethylhexyl adipate (DOA),isodecyl adipate (DIDA), di-2-ethylhexyl sebacate (DOS), dibutyl sebacate (DBS), di-2-ethylhexyl maleate (DOM), dibutyl fumarate (DBF), di-2-ethylhexyl azelate (DOZ), di-2-ethylhexyl epoxyhexahydrophthalate, trioctyl citrate, glycerol triacetate, etc.; as phosphate ester plasticizers, trimethyl phosphate, tributyl phosphate, tri-(2-ethylhexyl) phosphate, tributoxyethyl phosphate, triphenyl phosphate, tricresyl phosphate, alkylaryl phosphate, triethyl phosphate, tri(chloroethyl) phosphate, tris(dichloropropyl) phosphate, tris(β-chloropropyl) phosphate, octyldiphenyl phosphate, tris(isopropylphenyl) phosphate, cresyl phenyl phosphate, etc. These are merely examples and are not limited thereto. Further, these may be used alone or in combination of two or more kinds.

[0077] Elastomers can also be used as non-reactive plasticizers. Such plasticizers are preferably elastomers that are solid or liquid at 25°C. However, considering handleability, elastomers that are liquid at 25°C are preferred. Specific examples of non-reactive elastomers include rubber-based elastomers such as polybutadiene, hydrogenated polybutadiene, polyisoprene, hydrogenated polyisoprene, polybutene, polyisobutylene, copolymers of these monomers, diblock polymers of these, and triblock polymers of these. Examples of block polymers include, but are not limited to, polystyrene-polyisobutylene diblock copolymers and polystyrene-polyisobutylene-polystyrene triblock copolymers. The said component preferably has compatibility with components (A) to (C). These may be used alone or in combination of two or more. In the composition according to the present invention, in order to further reduce the permeability of an inert gas such as helium, rather than using the plasticizer of the above rubber-based elastomer as the plasticizer, it is preferable to use at least one selected from the group consisting of polycarboxylic acid ester-based plasticizers, trimellitic acid ester-based plasticizers, pyromellitic acid ester-based plasticizers, aliphatic polycarboxylic acid ester-based plasticizers, and phosphate ester-based plasticizers.

[0078] The content of the plasticizer is not particularly limited and can be appropriately set by those skilled in the art within a range that does not impair the properties of the present invention.

[0079] <Optional component> The photocurable composition according to the present invention may further contain components other than the above components (A) to (D) as long as the properties of the present invention are not impaired. Examples of such components include colorants such as pigments and dyes; inorganic fillers such as metal powders, calcium carbonate, talc, alumina, and aluminum hydroxide (however, not including the above component (E)); organic fillers such as polystyrene fillers, polyurethane fillers, poly(meth)acrylic fillers, and rubber fillers (however, not including the above components (A) and (B)); plasticizers; flame retardants; antioxidants; polymerization inhibitors; defoamers; coupling agents; leveling agents; rheology control agents; and the like. By adding these other components, a composition and its cured product excellent in resin strength, adhesion strength, workability, storage stability, etc. can be obtained. The content of the above components is not particularly limited and can be appropriately set by those skilled in the art as long as the properties of the present invention are not impaired.

[0080] In addition, the photocurable composition according to the present invention may contain other monomers in addition to the above components (A) to (D) as long as the properties of the present invention are not impaired. Examples of such monomers include acrylic acid, methacrylic acid; (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-n-butyl(meth)acrylamide, N-tert-butyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, N-methylol(meth)acrylamide, N,N-dimethyl(meth)acrylamide, 4-(meth)acryloylmorpholine, N,N-diethyl(meth)acrylamide, N-methyl-N-ethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, and other (meth)acrylamide compounds; and the like.

[0081] <Composition ratio> In the composition according to the present invention, the content of each of the above components is preferably in the following ranges from the viewpoint of improving the barrier properties against both moisture and helium and maintaining good adhesion to the adherend. That is, the composition according to the present invention preferably contains 10 to 30 parts by mass, more preferably 15 to 25 parts by mass of component (B) with respect to 100 parts by mass of component (A); preferably contains 100 to 200 parts by mass, more preferably 130 to 180 parts by mass of component (C); preferably contains 1.0 to 5.0 parts by mass, more preferably contains more than 3.0 parts by mass and less than 5.0 parts by mass of component (D) (however, in each of the components (A) to (D), when two or more kinds are included, the total amount is within the above range).

[0082] Furthermore, when the composition contains component (E), the content of component (E) is preferably 0.1 to 50 parts by mass, more preferably 1 to 30 parts by mass, still more preferably 5 to 25 parts by mass, and particularly preferably 15 parts by mass or more and less than 25 parts by mass with respect to 100 parts by mass of component (A) (however, when two or more kinds are included in component (E), the total amount is within the above range).

[0083] <Viscosity> The viscosity of the composition according to the present invention (measurement temperature 25°C, shear rate 20 s -1 ) is not particularly limited, but from the viewpoint of workability and the like, it is preferably 3 to 40 Pa·s, more preferably 3 to 35 Pa·s, and still more preferably 5 to 30 Pa·s. Also, when the viscosity at a shear rate of 20 s -1 is defined as viscosity 1 and the viscosity at a shear rate of 2 s -1 is defined as viscosity 2, the value of viscosity 2 / viscosity 1 (structural viscosity ratio) is not particularly limited, but is preferably 3.0 to 6.0, more preferably 3.5 or more and less than 5.5, and still more preferably 4.0 to 5.4. In addition, unless otherwise specified, in this specification, the viscosity value is the value measured at 25°C using a cone-plate viscometer.

[0084] <Manufacturing method> The manufacturing method of the composition according to the present invention is not particularly limited and can be manufactured by a conventionally known method. For example, it can be manufactured by weighing predetermined amounts of components (A) to (D) and mixing them using a mixing means such as a stirrer. The temperature and mixing time during mixing are not particularly limited, but it is preferably mixed at 10 to 70 °C for 0.1 to 5 hours. Further, it is preferable to perform mixing while performing vacuum degassing.

[0085] [Cured product] Another aspect of the present invention relates to a cured product obtained by curing the above photocurable composition by light irradiation. The cured product according to one aspect of the present invention is preferably cured by irradiating the photocurable composition with active energy rays such as ultraviolet rays. More specifically, the cured product according to one aspect of the present invention is preferably obtained by applying the photocurable composition to an adherend and then irradiating the applied composition with active energy rays.

[0086] [Coating method] The method for applying the photocurable composition according to the present invention to an adherend is not particularly limited. For example, methods such as dispensing using an automatic coater, spraying, inkjet, screen printing, gravure printing, dipping, and spin coating can be used.

[0087] [Curing method] The photocurable composition according to the present invention can be cured by irradiating it with active energy rays (for example, light such as ultraviolet rays and visible light). The light source used at this time is not particularly limited, and a known light source can be used. For example, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a black light lamp, a sodium lamp, a halogen lamp, a xenon lamp, an LED, etc. can be mentioned.

[0088] As an apparatus for curing the composition according to the present invention by active energy ray irradiation (light irradiation), an irradiation apparatus having the above-described light source (such as a high-pressure mercury lamp or an LED using active energy rays such as ultraviolet rays and visible light as the light source) can be used. Specific examples of the apparatus include, but are not limited to, a belt conveyor type irradiator and a spot irradiator. The lower limit of the integrated light quantity is not particularly limited, but it is preferably 20 kJ / m 2 or more, more preferably 30 kJ / m 2 or more. The upper limit of the integrated light quantity is not particularly limited either, but it is preferably 80 kJ / m 2 or less, more preferably 70 kJ / m 2 or less.

[0089] [Use] As described above, the photocurable composition according to the present invention is excellent in barrier properties against both moisture and helium, and can maintain good adhesion to the adherend. Therefore, the photocurable composition according to the present invention can be suitably used for the use of the cover seal of a hard disk drive. That is, as still another form of the present invention, a sealant containing the above photocurable composition is provided. And a preferred form of the sealant is used for a hard disk drive.

[0090] The sealant containing the composition according to the present invention can exhibit the above excellent properties. By strictly controlling the shape and dimensions of the sealant for a hard disk drive, it is possible to prevent an inert gas such as helium inside the housing from leaking to the external environment, and further prevent the intrusion of moisture from the external environment. By eliminating variations in shape and dimensions, leakage and intrusion from the portion can be effectively prevented.

Examples

[0091] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited only to these examples. Hereinafter, the photocurable composition may sometimes be simply referred to as a composition.

[0092] [Examples 1 to 5, Comparative Examples 1 to 11] To prepare the composition, the following ingredients were prepared: Component (A): Polyisobutylene having a (meth)acryloyl group in the molecule Polyisobutylene having an aromatic hydrocarbon group and an acryloyl group at each end of the molecular chain (EPION (registered trademark) EP400V, manufactured by Kaneka Corporation; indicated as "EP400V" in Table 1) Component (A'): Polybutene elastomer (containing no (meth)acryloyl groups) Polybutene with a number average molecular weight of 930 (PB950 manufactured by Dalim Co., Ltd.; indicated as "PB950" in Table 1) Polybutene with a number average molecular weight of 400 (PB400 manufactured by Dalim Co., Ltd.; indicated as "PB400" in Table 1) Component (B): urethane-modified (meth)acrylate oligomer (excluding component (A)) -UV-curable urethane acrylate with a polyether backbone (manufactured by Mitsubishi Chemical Corporation) Shikoh (registered trademark) UV-3700B; listed as "UV-3700B" in Table 1; weight average molecular weight: 38,000; number of acryloyl groups: 2) Hydrogenated polybutadiene acrylate resin having (meth)acryloyl groups at both ends of hydrogenated polybutadiene via urethane bonds (TEAI-1000 manufactured by Nippon Soda Co., Ltd.; indicated as "TEAI-1000" in Table 1) Component (C): (meth)acrylate monomer (excluding components (A) and (B)) Isobornyl acrylate (IBXA manufactured by Osaka Organic Chemical Industry Ltd.; indicated as "IBXA" in Table 1) Tetrahydrofurfuryl acrylate (THF-A manufactured by Kyoeisha Chemical Co., Ltd.; referred to as "THF-A" in Table 1) Isononyl acrylate (INAA manufactured by Osaka Organic Chemical Industry Ltd.; indicated as "INAA" in Table 1) Nonylphenol EO modified acrylate (n≒1) (Aronix (registered trademark) M-111, manufactured by Toagosei Co., Ltd.; indicated as "M-111" in Table 1) · Para-cumylphenol EO-modified acrylate (n ≒ 1.2) (manufactured by Toagosei Co., Ltd., Aronix (registered trademark) M-110; described as "M-110" in Table 1) Component (D): Photoinitiator · Oligomer of 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone (manufactured by IGM Resins B.V., ESACURE (registered trademark) KIP-150; described as "KIP-150" in Table 1) Component (E): Filler · Hydrophilic silica with an average primary particle diameter of 12 nm and a specific surface area (BET method) of 200 m 2 / g (manufactured by Nippon Aerosil Co., Ltd., AEROSIL (registered trademark) 200; described as "200" in Table 1).

[0093] The components (A) to (E) were weighed and put into a stirrer. Then, while performing vacuum degassing, stirring was carried out at room temperature for 1 hour using the stirrer. The content of each component in the composition follows Table 1, and all numerical values indicate parts by mass.

[0094]

Table 1

[0095] For the compositions of Examples 1 to 5 and Comparative Examples 1 to 11, appearance confirmation (before and after curing), viscosity and structure viscosity ratio measurement, adhesive strength measurement, water vapor transmission coefficient measurement, and helium transmission coefficient measurement were carried out, and the results were summarized in Table 2.

[0096] [Appearance confirmation (before and after curing)] 10 g of the composition was taken in a test tube and left in a shaded state in a 25°C atmosphere for 3 days. Visual evaluation was carried out according to the following evaluation criteria, and the results were described in Table 2 as "Appearance (before curing)". It is preferable to be "transparent" or "cloudy". For the composition evaluated as "separated", it was marked as "-" in Table 2 without performing other evaluations. Then, for the composition in which separation was not confirmed, using a belt conveyor type ultraviolet irradiation machine, the integrated light quantity was 60 kJ / m 2Cure under the following conditions, visually evaluate according to the following evaluation criteria, and record the results as "Appearance (after curing)" in Table 2.

[0097] <Evaluation Criteria for Appearance (Before and After Curing)> ◎: Transparent ○: Cloudy ×: Separation.

[0098] [Measurement of Viscosity and Structure Viscosity Ratio] Using a rheometer, the viscosity and structure viscosity ratio were measured under the following conditions. HAAKE MARSIII manufactured by Thermo Fisher Scientific was used. The viscosity at a shear rate of 20 s -1 was defined as Viscosity 1, and the viscosity at a shear rate of 2 s -1 was defined as Viscosity 2. The value of Viscosity 1 was recorded in Table 2 as "Viscosity (Pa·s)". The value of Viscosity 2 / Viscosity 1 was recorded in Table 2 as "Structure Viscosity Ratio". In order to discharge at an optimal pressure in bead coating, the viscosity is preferably 3 - 35 Pa·s. Also, the structure viscosity ratio is preferably 3.0 - 6.0. When the structure viscosity ratio is 3.0 or more, the fluidity during coating is suppressed, and when the structure viscosity ratio is 6.0 or less, no corners are generated after coating.

[0099] <Measurement Conditions> Ambient temperature during measurement: 25°C Cone: C35 / 2 (angle 2°).

[0100] [Adhesion Measurement] On a plate made of SUS304 as the adherend, the composition was applied in a bead shape with a width of 3.0 ± 0.15 mm and a height of 2.0 ± 0.2 mm using a dispenser. Using a high-pressure mercury lamp with a belt conveyor type irradiator, the integrated light quantity was 60 kJ / m 2Under the condition of , the composition was irradiated with light and heated in a hot air drying furnace under baking conditions of 150 °C for 3 hours to obtain a test piece. After baking, the test piece was left standing overnight at room temperature. As shown in Figure 1, a digital force gauge manufactured by Nidec Corporation with a contactor attached was moved at a speed of 50 mm / min to push the bead from the side, and the maximum load at that time was defined as "strength (N)". The adhesive strength is preferably 10.0 N or more, more preferably 15.0 N or more. Also, after measuring the adhesive strength, the state in which the bead peels off from the adherend was visually evaluated according to the following evaluation criteria and described in Table 2 as "peeling state". Considering the leakage at the interface, it is preferably ◎ or ○.

[0101] <Evaluation criteria for peeling state> ◎: Cohesive failure over the entire surface ○: Cohesive failure over the entire surface but partial interfacial failure ×: Complete interfacial failure.

[0102] [Measurement of water vapor transmission coefficient] The composition was filled into a frame with a length of 50 mm × width of 50 mm × thickness of 0.6 mm, and irradiated with light and cured using a belt conveyor type ultraviolet irradiator under the condition of an integrated light amount of 30 kJ / m 2 . The cured product was heated in a hot air drying furnace under baking conditions of 150 °C for 3 hours. After baking, the "water vapor transmission rate (g / m 2 ·24 h)" under the conditions of 65 °C and 90% RH was measured using a water vapor transmission rate measuring device PERMATRAN-W (registered trademark) 3 / 34G manufactured by Mocon. Since the film thickness of the cured product is not used in the calculation of the water vapor transmission rate (WVTR), the moisture barrier property at the same thickness cannot be evaluated. Therefore, the value obtained by multiplying the WVTR by the "film thickness (μm)" of the cured product at the time of measurement is defined as the "water vapor transmission coefficient (g / m 2 ·24 h·μm)" and used as an index of moisture permeability. From the viewpoint of reducing the moisture permeability, the water vapor transmission coefficient is preferably 50 g / m 2 ·24 h·μm or less.

[0103] [Measurement of helium transmission coefficient] Based on JIS K 7126-1:2006, the gas permeability was measured by the differential pressure method. The composition was filled in a frame with a length of 50 mm × width of 50 mm × thickness of 0.6 mm, and using a belt conveyor type ultraviolet irradiation machine, the composition was irradiated with light and cured under the condition of an integrated light quantity of 30 kJ / m 2 The helium permeability was evaluated using GTR-21A-B manufactured by GTR Tech Co., Ltd. The "helium permeability coefficient (×10 -9 )(cc·cm / cm 2 ·sec·cmHg)" obtained by conversion from the "film thickness of the cured product (μm)" was measured. From the viewpoint of reducing the helium permeability, the helium permeability coefficient is preferably 8.0×10 -9 cc·cm / cm 2 ·sec·cmHg(cm 3 ·cm / cm 2 ·sec·cmHg) or less.

[0104]

Table 2

[0105] The compositions of Examples 1 to 5 contain 1 to 50 parts by mass of component (B) and 50 to 300 parts by mass of component (C) in total with respect to 100 parts by mass in total of component (A). These compositions have a water vapor permeability coefficient of the cured product of 50 g / m 2 ·24h·μm or less, and a helium permeability coefficient of 8.0×10 -9 cc·cm / cm 2 ·sec·cmHg(cm 3 ·cm / cm 2·sec·cmHg) or less, maintaining low permeability of moisture and helium. Furthermore, it has high strength, does not peel at the interface with the adherend, and can maintain sealing performance. On the other hand, Comparative Example 1 without component (A) has low helium permeability but high moisture permeability. Comparative Examples 2 and 3 without component (B) have low permeability of moisture and helium but low strength, and there is a risk of peeling at the interface with the adherend and inability to maintain sealing performance. Comparative Examples 4 to 6 have low moisture permeability but high helium permeability. Comparative Examples 7 to 11 contain a large amount of component (C) relative to 100 parts by mass of component (A). Although the cause is not clear, in Comparative Examples 7 and 8, there may be a possibility of separation of the composition because a urethane-modified (meth)acrylate oligomer without a rubber skeleton as component (B) is contained in a large amount. In Comparative Examples 9 to 11, since the component corresponding to component (A) is a polybutene elastomer not containing a (meth)acryloyl group, there may be a possibility of separation of the composition. When separation of the composition occurs, re-stirring must be performed immediately before bead coating. If the re-stirring is insufficient, unevenness occurs during curing in the bead, leading to bleed-out and destabilization of sealing characteristics.

Industrial Applicability

[0106] Due to the excellent viscosity and stability of the structure-viscosity ratio of the photocurable composition according to the present invention, the workability when used as a sealant is good and it can be efficiently formed. Further, the photocurable composition according to the present invention has high moisture barrier properties and helium barrier properties when used as a sealant. Therefore, it is useful as a cover seal for sealing the housing of a hard disk drive and as a sealant for other electrical and electronic components.

[0107] This application is based on Japanese Patent Application No. 2020-073243 filed on April 16, 2020, the disclosure of which is incorporated herein by reference in its entirety.

Explanation of Symbols

[0108] 1: Bead 2: Object to be worn 3: Contact (Digital force gauge is omitted) 4: Direction of travel of the contact

Claims

1. A photocurable composition comprising the following components (A) to (D) and satisfying at least one of the following (i) to (iv): Component (A): Polyisobutylene having a (meth)acryloyl group in the molecule Component (B): Urethane-modified (meth)acrylate oligomer (excluding component (A)) Component (C): (Meth)acrylate monomer (excluding components (A) and (B)) Component (D): Photoinitiator; (i) Containing 10 to 30 parts by mass of component (B) and 50 to 300 parts by mass of component (C) with respect to 100 parts by mass of component (A), (ii) Containing 1 to 50 parts by mass of component (B) and 100 to 200 parts by mass of component (C) with respect to 100 parts by mass of component (A), (iii) Containing 1 to 50 parts by mass of component (B) and 50 to 300 parts by mass of component (C) with respect to 100 parts by mass of component (A), Component (C) contains a (meth)acrylate monomer having a structure of the following formula (C-1): 【Chemical 1】 (In the above formula (C-1), R1 is hydrogen or a methyl group, R2 is a hydrocarbon group having 1 to 20 carbon atoms, and n is an integer of 0 to 10.) (iv) Containing 1 to 50 parts by mass of component (B) and 50 to 300 parts by mass of component (C) with respect to 100 parts by mass of component (A), Further containing a filler as component (E), and containing 0.1 to 50 parts by mass of component (E) with respect to 100 parts by mass of component (A).

2. The photocurable composition according to claim 1, wherein component (A) contains polyisobutylene having an aromatic hydrocarbon group in the molecule.

3. The photocurable composition according to claim 1 or 2, wherein component (B) is a urethane-modified (meth)acrylate oligomer not containing a rubber skeleton.

4. A sealant comprising the photocurable composition according to any one of claims 1 to 3.

5. The sealant according to claim 4, which is used for a hard disk drive.

6. A cured product obtained by curing the photocurable composition according to any one of claims 1 to 3 by light irradiation.

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