Shock-absorbing sheet

Abstract

Provided is an impact-absorbing sheet having excellent impact absorption performance, durability against repeated bending, and excellent flexibility at low temperatures. The sheet comprises a resin foam layer formed by curing a resin composition containing a monofunctional urethane (meth)acrylate, wherein the monofunctional urethane (meth)acrylate is one or more monomers selected from reaction products of compounds containing a predetermined (meth)acryloyloxy group.

Description

Technical Field

[0001] The present invention relates to a shock-absorbing sheet suitable for electronic equipment and the like. Background Art

[0002] Mobile devices such as smartphones, tablets, and laptops can sometimes be damaged by the impact of being dropped or bumped, causing damage to the casing or display panel.

[0003] To prevent such damage, impact absorbing sheets are used, for example, between a cover panel and a housing, between a display device such as a liquid crystal or organic electroluminescent (OLED) device and a touch screen, and on the back side of the display device.

[0004] As such an impact-absorbing sheet, a foam sheet of an olefin resin represented by polyethylene or an acrylic resin is known (for example, see Patent Document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2020 / 013258 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] In recent years, the development of foldable mobile devices equipped with foldable displays, i.e., foldable devices, has been underway. Shock-absorbing sheets used in foldable devices are required not only to have shock-absorbing performance but also to have durability against repeated bending (hereinafter referred to as "repeated bending durability").

[0010] Furthermore, since mobile devices are often carried and used in various environments, impact-absorbing sheets installed in these devices are required to exhibit impact-absorbing performance and flexibility with repeated bending durability even in extremely cold environments below 0°C.

[0011] However, conventional impact-absorbing sheets made of foam sheets of olefin resins or acrylic resins cannot be said to have sufficient repeated bending durability and flexibility at low temperatures.

[0012] The present invention is to solve such a problem, and an object of the present invention is to provide an impact-absorbing sheet having excellent impact absorption performance, durability against repeated bending, and flexibility at low temperatures.

[0013] Solutions for solving problems

[0014] The present invention is based on the discovery that a resin foam layer produced using a predetermined urethane acrylate having a polyether chain and a urethane bond can provide an impact-absorbing sheet having excellent impact absorption performance, repeated bending durability, and flexibility at low temperatures.

[0015] The present invention provides the following means.

[0016] [1] An impact-absorbing sheet comprising a resin foam layer formed by curing a resin composition containing a monofunctional urethane (meth)acrylate, wherein the monofunctional urethane (meth)acrylate is one or more monomers selected from the reaction products of the following (i) to (iii).

[0017] (i) An equimolar reaction product of a polyether monool and a compound having a (meth)acryloyloxy group, wherein the compound having a (meth)acryloyloxy group has one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule.

[0018] (ii) an equimolar reaction product of a polyether monool, a diisocyanate, and a compound having a (meth)acryloyloxy group, wherein the compound having a (meth)acryloyloxy group has one group reactive with an isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule.

[0019] (iii) an equimolar reaction product of a polyether polyol and a compound having a (meth)acryloyloxy group, wherein the compound having a (meth)acryloyloxy group has one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule.

[0020] [2] The impact-absorbing sheet according to [1], wherein the molecular weight of the monomer is 3,000 to 30,000.

[0021] [3] The impact-absorbing sheet according to [1] or [2], wherein the cured product of the resin composition has a glass transition temperature of -55°C or lower.

[0022] [4] The impact-absorbing sheet according to any one of [1] to [3], wherein the monomer is a reaction product of (i).

[0023] [5] The impact-absorbing sheet according to any one of [1] to [4], wherein the resin foam layer contains hollow particles.

[0024] [6] The impact-absorbing sheet according to any one of [1] to [5], wherein the resin foam layer is formed by a mechanical foaming method.

[0025] [7] The impact-absorbing sheet according to any one of [1] to [6], wherein the thickness is 300 μm or less.

[0026] [8] The impact-absorbing sheet according to any one of [1] to [7], which is used for electronic equipment.

[0027] [9] The impact-absorbing sheet according to any one of [1] to [8], which is arranged on the back side of a display device.

[0028]

[10] An adhesive tape comprising:

[0029] The impact-absorbing sheet according to any one of [1] to [9]; and

[0030] An adhesive material is provided on at least a portion of at least one surface of the impact-absorbing sheet.

[0031] Effects of the Invention

[0032] According to the present invention, it is possible to provide an impact-absorbing sheet having excellent impact absorption performance, durability against repeated bending, and flexibility at low temperatures. DETAILED DESCRIPTION

[0033] The following are definitions and meanings of the terms and expressions used in this specification.

[0034] The "(meth)acryloyloxy group" is a general term for an acryloyloxy group and a methacryloyloxy group.

[0035] "(Meth)acrylate" is a general term for acrylate and methacrylate. Similarly, "(meth)acrylic acid" is a general term for acrylic acid and methacrylic acid.

[0036] Unless otherwise specified, the “number of functional groups” refers to the number of (meth)acryloyloxy groups in one molecule. The “average number of functional groups” refers to the average number of (meth)acryloyloxy groups in one molecule, with the formula weight or number average molecular weight based on the chemical formula as one unit, unless otherwise specified.

[0037] "Monofunctional urethane (meth)acrylate" refers to a urethane (meth)acrylate having an average functional group number of substantially 1 in one molecule. A urethane (meth)acrylate having an average functional group number of 0.7 to 1.4, preferably 0.8 to 1.3, in one molecule is regarded as a urethane (meth)acrylate having substantially one (meth)acryloyloxy group in one molecule, that is, a monofunctional urethane (meth)acrylate.

[0038] The term "equimolar reaction product" means that the molar ratio of the reacted compounds is substantially 1, and a reaction product in which the molar ratio is 0.7 to 1.4, preferably 0.8 to 1.3 is regarded as an equimolar reaction product.

[0039] Similarly, "equal molar numbers" of the reacting groups (or compounds) means that the molar ratio of the reacting groups (or compounds) is substantially 1. When the molar ratio is 0.7 to 1.4, preferably 0.8 to 1.3, the molar numbers of the reacting groups (or compounds) are considered equal.

[0040] The "hydroxyl value" is determined by measurement in accordance with JIS K 1557:2007.

[0041] The “hydroxyl value-equivalent molecular weight” is a value calculated from the formula: 56,100 / (hydroxyl value)×(the number of active hydrogen atoms in the initiator).

[0042] The “NCO index” in the reaction between an isocyanate group-containing compound and a hydroxyl group-containing compound is a value obtained by expressing the equivalent ratio of the isocyanate groups in the isocyanate group-containing compound to the hydroxyl groups in the hydroxyl group-containing compound as a percentage.

[0043] Unless otherwise specified, "molecular weight" refers to the formula weight based on the chemical formula, or, in the case of a compound with a molecular weight distribution, the number average molecular weight. "Number average molecular weight" refers to the polystyrene-equivalent molecular weight determined by gel permeation chromatography (GPC) based on a calibration curve prepared using standard polystyrene samples.

[0044] The impact-absorbing sheet of the present invention comprises a resin foam layer formed by curing a resin composition containing a monofunctional urethane (meth)acrylate, wherein the monofunctional urethane (meth)acrylate is one or more monomers (hereinafter also referred to as "first monomers") selected from the reaction products of the following (i) to (iii).

[0045] (i) an equimolar reaction product of a polyether monool and a compound having a (meth)acryloyloxy group,

[0046] The compound having a (meth)acryloyloxy group is a compound having one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule.

[0047] (ii) an equimolar reaction product of a polyether monool, a diisocyanate and a compound having a (meth)acryloyloxy group,

[0048] The compound having a (meth)acryloyloxy group is a compound having one group reactive with an isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule.

[0049] (iii) an equimolar reaction product of a polyether polyol and a compound having a (meth)acryloyloxy group,

[0050] The compound having a (meth)acryloyloxy group is a compound having one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule.

[0051] The impact-absorbing sheet of the present invention having the resin foam layer as described above is excellent in impact absorption performance, repeated bending durability, and flexibility at low temperatures.

[0052] [Resin foam layer]

[0053] The resin foam layer is formed by curing a resin composition containing a monofunctional urethane (meth)acrylate, and contains a cured product of the resin composition and bubbles.

[0054] Resin compositions containing monofunctional urethane (meth)acrylates can undergo photopolymerization or thermal polymerization using the (meth)acryloyloxy groups of the monofunctional urethane (meth)acrylates. Furthermore, the monofunctional urethane (meth)acrylates, by having flexible graft chains that do not contribute to crosslinking, yield a cured product with excellent flexibility. The resin foam layer based on this cured product can exhibit excellent impact absorption properties. Furthermore, the cured product exhibits low temperature dependence of its storage modulus over a wide temperature range of -20°C to 80°C, maintaining excellent flexibility even at temperatures below 0°C.

[0055] From the viewpoint of the curing speed of the resin composition, the (meth)acryloyloxy group of the monofunctional urethane (meth)acrylate is preferably an acryloyloxy group.

[0056] 〔First Unit〕

[0057] The monofunctional urethane (meth)acrylate is one or more first monomers selected from the reaction products of (i) to (iii) (hereinafter also referred to as "monomer (1-1)", "monomer (1-2)", and "monomer (1-3)"). That is, the resin composition contains a monofunctional urethane (meth)acrylate as the first monomer. The first monomer in the resin composition may be a single monomer or a combination of two or more monomers.

[0058] The molecular weight of the first monomer is preferably 3,000 to 30,000, more preferably 4,000 to 20,000, and even more preferably 5,000 to 17,000. A molecular weight of 3,000 or greater makes the cured resin composition more flexible, while a molecular weight of 30,000 or less makes it easier to adjust the viscosity of the resin composition. When two or more first monomers are used in combination, the molecular weight of each is preferably within the above range.

[0059] <Monomer (1-1)>

[0060] Monomer (1-1) is a reaction product of the aforementioned (i), and is an equimolar reaction product of the polyether monool (i-1) and the compound (i-2) having a (meth)acryloyloxy group. The compound (i-2) having a (meth)acryloyloxy group is a compound having one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule.

[0061] The monomer (1-1) is preferably a compound represented by formula (1).

[0062]

[0063] In formula (1), R 1 It is a monovalent organic group having one or two (meth)acryloyloxy groups.

[0064] R 12 It is preferably an alkylene group having 2 to 8 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms. 12 There are two or more types of R in one molecule. 12 In the case of -OR 12 -chains can be block or random. 12 It is preferably one or more selected from the group consisting of an ethylene group, a propylene group, a 1,2-dimethylethylene group, and a 1-ethylethylene group, and more preferably one or more selected from the group consisting of an ethylene group and a propylene group.

[0065] In addition, (OR 12 ) is also preferably a unit based on the monomer (a) described later, wherein the monomer (a) has one epoxy group and an ether bond other than the ether bond of the epoxy group in one molecule. The unit based on monomer (a) is preferably a unit represented by formula (11). Monomer (a) may be used alone or in combination of two or more.

[0066]

[0067] In formula (11), R 101 -R 103 -OR 104The monovalent group shown, R 102 A hydrogen atom or -R 105 -OR 106 The monovalent group shown. 103 、R 105 Each independently represents a linear or branched alkylene group having 1 to 3 carbon atoms, R 104 、R 106 Each independently represents a linear or branched alkyl group having 1 to 18 carbon atoms.

[0068] As R 103 、R 105 The alkylene groups are each independently preferably methylene, ethylene, n-propylene, or isopropylene, more preferably methylene or ethylene, and still more preferably methylene.

[0069] R 104 、R 106 The number of carbon atoms in each independently is preferably 1-14, more preferably 1-12, and even more preferably 2-10.

[0070] As R 104 、R 106 Examples of the straight-chain alkyl group include methyl, ethyl, n-propyl, n-butyl, n-octyl, n-decyl, lauryl, cetyl, and stearyl, with methyl, ethyl, and n-butyl being preferred. A branched-chain alkyl group has a structure in which hydrogen atoms (excluding those bonded to terminal carbon atoms) in the aforementioned straight-chain alkyl group are replaced by alkyl groups. Examples of the substituted alkyl group include methyl and ethyl. A branched-chain alkyl group is preferably 2-ethylhexyl.

[0071] As the monomer (a), a monomer represented by formula (12) is preferred.

[0072]

[0073] R in formula (12) 101 and R 102 have the same meanings as the same symbols in formula (11).

[0074] Examples of the monomer represented by formula (12) include methyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, lauryl glycidyl ether, and hexyl glycidyl ether. From the viewpoint of better flexibility of the cured product of the obtained resin composition, butyl glycidyl ether and 2-ethylhexyl glycidyl ether are preferred.

[0075] In formula (1), R 13 is an alkyl group having 1 to 20 carbon atoms. 13 An alkyl group having 1 to 8 carbon atoms is preferred, a methyl group, an ethyl group, or a butyl group is more preferred, and a butyl group is further preferred.

[0076] a is an integer of 20 to 600. a is preferably an integer of 35 to 500, more preferably an integer of 65 to 250.

[0077] (Polyether monool (i-1))

[0078] The polyether monool (i-1) in the monomer (1-1) is a compound obtained by ring-opening polymerization of an initiator having an active hydrogen-containing group and having one or more active hydrogen atoms with an alkylene oxide and / or the aforementioned monomer (a), and has an initiator residue, a polyether chain, and hydroxyl groups corresponding to the number of active hydrogen atoms in the initiator.

[0079] From the viewpoint of adjusting the flexibility and strength of the cured product of the resin composition, the ratio of the mass of the monomer (a) to the total mass of the alkylene oxide and the monomer (a) is preferably 0 to 90 mass %, more preferably 0 to 85 mass %, and even more preferably 10 to 80 mass %.

[0080] The alkylene oxide is preferably an alkylene oxide having 2 to 8 carbon atoms, and more preferably an alkylene oxide having 2 to 4 carbon atoms. Specific examples of the alkylene oxide include propylene oxide, ethylene oxide, 1,2-butylene oxide, and 2,3-butylene oxide.

[0081] Examples of the active hydrogen-containing group possessed by the initiator include a hydroxyl group, a carboxyl group, and an amino group having one hydrogen atom bonded to a nitrogen atom. The active hydrogen-containing group possessed by the initiator is preferably a hydroxyl group or a carboxyl group, more preferably a hydroxyl group, and even more preferably an alcoholic hydroxyl group.

[0082] Examples of initiators having one active hydrogen atom include monohydric alcohols, monohydric phenols, monocarboxylic acids, and amine compounds having one hydrogen atom bonded to a nitrogen atom. Preferred initiators are monohydric aliphatic alcohols and monohydric aliphatic carboxylic acids, with monohydric aliphatic alcohols being more preferred. Furthermore, polyoxyalkylene monools having a lower molecular weight than the target polyether monool can be used as initiators.

[0083] The number of carbon atoms in the monohydric aliphatic alcohol as the initiator is preferably 1 to 20, more preferably 2 to 8. Specific examples of the monohydric aliphatic alcohol as the initiator include ethanol, propanol, 2-propanol, and butanol.

[0084] The number of carbon atoms of the monovalent aliphatic carboxylic acid serving as the initiator is preferably 2 to 20, more preferably 2 to 8, including the carbon atoms of the carboxyl group.

[0085] The oxyalkylene group in the polyether monool (i-1) is preferably composed of only an oxypropylene group or a combination of an oxypropylene group and other groups. The oxyalkylene group other than the oxypropylene group is preferably an oxyethylene group.

[0086] The ratio of the oxypropylene group to the total oxyalkylene groups in the polyether monool (i-1) is preferably 50 to 100 mass%, more preferably 80 to 100 mass%. In addition, when the initiator is a polyoxyalkylene monool having a lower molecular weight than the target polyether monool, the oxyalkylene groups in the initiator are regarded as the oxyalkylene groups in the obtained polyether monool.

[0087] Among the polyether monols (i-1), low hydroxyl value, i.e., high molecular weight polyoxyalkylene monools can be produced by ring-opening polymerization of an alkylene oxide having 3 or more carbon atoms, particularly propylene oxide, with an initiator in the presence of a double metal cyanide complex catalyst.

[0088] Examples of the low-hydroxyl-value polyoxyalkylene monool include polyoxyalkylene monools having a hydroxyl value of 40 mgKOH / g or less.

[0089] Polyoxyalkylene monools having a low hydroxyl value of oxyethylene groups can be produced by ring-opening polymerization of an alkylene oxide having 3 or more carbon atoms, particularly propylene oxide, in the presence of a composite metal cyanide complex catalyst, using a polyoxyalkylene monool having a high hydroxyl value of oxyethylene groups, for example, a hydroxyl value of 50 mgKOH / g or more, as an initiator.

[0090] The polyoxyalkylene monool having a high hydroxyl value can be produced by the aforementioned ring-opening polymerization in the presence of an alkaline catalyst such as potassium hydroxide.

[0091] In the production of polyoxyalkylene monools, the initiator and alkylene oxide introduced into the reaction system are generally low in water content after water has been removed by degassing under reduced pressure, etc. Generally, the lower the water content of the initiator used in the production of polyoxyalkylene monools, the better, preferably 500 ppm by mass or less, and more preferably 300 ppm by mass or less. When the water content is within the above range, the amount of polyoxyalkylene glycol generated from water is suppressed, resulting in a reduction in the amount of by-products generated from the polyoxyalkylene glycol, making it easier to adjust the upper limit of the average hydroxyl number of the resulting polyoxyalkylene monool to 1.2 or less.

[0092] The lower the water content of the polyether monool (i-1) used as the raw material of the monomer (1-1), the more preferably it is, and relative to the polyether monool (i-1), it is preferably 300 mass ppm or less, more preferably 250 mass ppm or less, and even more preferably 50 to 200 mass ppm. If the water content is within the above range, the formation of by-products formed by water and compounds containing isocyanate groups is reduced, and the stability of the monomer (1-1) as the reaction product is improved. Furthermore, it is easy to suppress the appearance change of the resin composition over time, and it is easy to obtain a cured product of the resin composition with good flexibility.

[0093] The average number of hydroxyl groups in one molecule of the polyether monool (i-1) is preferably 0.80 to 1.20, more preferably 0.90 to 1.10.

[0094] The hydroxyl value of the polyether monool (i-1) is preferably 1.6 to 18.1 mgKOH / g, more preferably 2.8 to 14 mgKOH / g, and even more preferably 3.1 to 11.2 mgKOH / g.

[0095] The polyether monool (i-1) in the monomer (1-1) may be a mixture of two or more polyether monools. In this case, each polyether monool is preferably a polyoxyalkylene monool within the above-mentioned category.

[0096] Examples of the polyether monool (i-1) include those represented by formula (1a).

[0097] H-(OR 12 ) a -OR 13 ···(1a)

[0098] In formula (1a), R 12 、R 13 and a have the same meanings as the same symbols in formula (1).

[0099] (Compound (i-2) having a (meth)acryloyloxy group)

[0100] The compound (i-2) having a (meth)acryloyloxy group is a compound having one isocyanate group and one or two (meth)acryloyloxy groups in one molecule. The compound (i-2) having a (meth)acryloyloxy group is preferably a (meth)acrylate having an isocyanate group bonded to an aliphatic hydrocarbon group or an alicyclic hydrocarbon group, and more preferably an isocyanatoalkyl (meth)acrylate.

[0101] The number of carbon atoms of the alkylene group excluding the isocyanate group in the isocyanatoalkyl group is preferably 8 or less, more preferably 4 or less.

[0102] Examples of the compound (i-2) having a (meth)acryloyloxy group include compounds represented by formula (1b).

[0103]

[0104] In formula (1b), R 11 is a hydrogen atom or a methyl group. 11 Preferred is a hydrogen atom.

[0105] s is an integer of 1-4, preferably an integer of 1-2.

[0106] Specific examples of the compound (i-2) having a (meth)acryloyloxy group include 2-isocyanatoethyl (meth)acrylate and isocyanatomethyl methacrylate. Commercially available products include, for example, "Karenz (registered trademark; hereinafter omitted) AOI" and "Karenz MOI" (both manufactured by Showa Denko K.K.).

[0107] Examples of the compound (i-2) having a (meth)acryloyloxy group include compounds represented by formula (1c).

[0108]

[0109] In formula (1c), R 11 is a hydrogen atom or a methyl group. 11 Preferred is a hydrogen atom.

[0110] R 14 R is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 14 Preferred is methyl.

[0111] t is an integer of 1 to 8. t is preferably an integer of 1 to 4, more preferably an integer of 1 to 2.

[0112] u is an integer of 0 to 4. Preferably, u is an integer of 0 to 2.

[0113] Specific examples of the compound (i-2) having a (meth)acryloyloxy group include 2,2-(bisacryloyloxymethyl)propyl isocyanate and 1,1-(bisacryloyloxymethyl)ethyl isocyanate (trade name "Karenz BEI", manufactured by Showa Denko K.K.), and 1,1-(bisacryloyloxymethyl)ethyl isocyanate is preferred.

[0114] The monomer (1-1) is preferably at least one selected from the group consisting of the compound represented by formula (1-1-1), the compound represented by formula (1-1-2), and formula (1-1-3).

[0115]

[0116] In formula (1-1-1), formula (1-1-2) and formula (1-1-3), m, n1 and n2 are each independently preferably an integer of 20 to 600, more preferably an integer of 35 to 500, and even more preferably an integer of 65 to 250.

[0117] Bu is butyl.

[0118] <Monomer (1-2)>

[0119] Monomer (1-2) is a reaction product of the aforementioned (ii), and is an equimolar reaction product of a polyether monool (ii-1), a diisocyanate (ii-2) and a compound (ii-3) having a (meth)acryloyloxy group. The compound (ii-3) having a (meth)acryloyloxy group is a compound having one group reactive with an isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule.

[0120] As the monomer (1-2), a compound represented by formula (2) is preferable.

[0121]

[0122] In formula (2), R 2 It is a monovalent organic group having one or two (meth)acryloyloxy groups.

[0123] R 22 It is preferably an alkylene group having 2 to 8 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms. 22 There are two or more types of R in one molecule. 22 In the case of -OR 22 -chains can be block or random. 22 It is preferably one or more selected from the group consisting of ethylene, propylene, 1,2-dimethylethylene, and 1-ethylethylene, and more preferably one or two selected from the group consisting of ethylene and propylene.

[0124] In addition, (OR 22 ) is also consistent with (OR 12 ) is preferably a unit based on the aforementioned monomer (a), wherein the monomer (a) has one epoxy group and an ether bond other than the ether bond of the epoxy group in one molecule. The preferred embodiment of the monomer (a) is the same as that of the monomer (1-1).

[0125] R 23 is an alkyl group having 1 to 20 carbon atoms. 23 An alkyl group having 2 to 8 carbon atoms is preferred, and a butyl group is more preferred.

[0126] R 24 It is a divalent group obtained by removing two isocyanate groups from a diisocyanate. Examples of diisocyanates are described below.

[0127] b is an integer of 20 to 600. b is preferably an integer of 35 to 500, more preferably an integer of 65 to 250.

[0128] (Polyether monool (ii-1))

[0129] The polyether monool (ii-1) is the same as the polyether monool (i-1) in the monomer (1-1), and the preferred aspects are also the same.

[0130] Examples of the polyether monool (ii-1) include those represented by formula (2a).

[0131] H-(OR 22 ) b -OR 23 ···(2a)

[0132] In formula (2a), R 22 、R 23 and b have the same meanings as the same symbols in formula (2).

[0133] (Diisocyanate (ii-2))

[0134] Diisocyanate (ii-2) is a compound having two isocyanate groups in one molecule.

[0135] Examples of the diisocyanate (ii-2) include non-yellowing aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and various modified forms of these diisocyanates (modified forms having two isocyanate groups). The diisocyanate may be used alone or in combination of two or more.

[0136] The diisocyanate (ii-2) is preferably at least one selected from aliphatic diisocyanates and alicyclic diisocyanates from the viewpoint of flexibility and repeated bending durability of the cured product of the resin composition.

[0137] Specific examples of the non-yellowing aromatic diisocyanate include xylylene diisocyanate and tetramethylxylylene diisocyanate.

[0138] Specific examples of the aliphatic diisocyanate include 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate.

[0139] Examples of the alicyclic diisocyanate include isophorone diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, 2,5-norbornane diisocyanate, and 2,6-norbornane diisocyanate.

[0140] Examples of the diisocyanate (ii-2) include compounds represented by formula (2b).

[0141] O=C=NR 24 -N=C=O ···(2b)

[0142] In formula (2b), R24 have the same meanings as the same symbols in formula (2).

[0143] As the diisocyanate, from the viewpoint of flexibility and repeated bending durability of the cured product of the resin composition, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, and 4,4′-dicyclohexylmethane diisocyanate are preferred.

[0144] (Compound (ii-3) having a (meth)acryloyloxy group)

[0145] The compound (ii-3) having a (meth)acryloyloxy group is a compound having one group reactive with an isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule.

[0146] Examples of the group reactive with an isocyanate group include a hydroxyl group and an amino group having a nitrogen atom bonded to a hydrogen atom. The number of hydroxyl groups and the number of hydrogen atoms bonded to the nitrogen atom in the group reactive with an isocyanate group are preferably each 1. Furthermore, the group reactive with an isocyanate group is preferably a hydroxyl group bonded to an aliphatic hydrocarbon group or an alicyclic hydrocarbon group.

[0147] As the compound (ii-3) having a (meth)acryloyloxy group, hydroxyalkyl (meth)acrylates and hydroxycycloalkyl (meth)acrylates are preferred, and hydroxyalkyl (meth)acrylates having a hydroxyalkyl group with 8 or less carbon atoms are particularly preferred.

[0148] Examples of the compound (ii-3) having a (meth)acryloyloxy group include compounds represented by formula (2c).

[0149]

[0150] In formula (2c), R 21 is a hydrogen atom or a methyl group. 21 Preferred is a hydrogen atom.

[0151] p is an integer of 1 to 4. Preferably, p is an integer of 1 to 2.

[0152] Specific examples of the compound (ii-3) having a (meth)acryloyloxy group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. Commercially available products include Light Ester HO-250 (N), Light Ester HOP (N), Light Ester HOA (N), Light Ester HOP-A (N), and Light Ester HOB (N) (all manufactured by Kyoeisha Chemical Co., Ltd.) and 4-HBA (manufactured by Osaka Organic Chemical Industry Co., Ltd.).

[0153] Examples of the compound (ii-3) having a (meth)acryloyloxy group include compounds represented by formula (2d).

[0154]

[0155] In formula (2d), R 21 is a hydrogen atom or a methyl group. 21 Preferred is a hydrogen atom.

[0156] R 25 R is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 25 Preferred is methyl.

[0157] q is an integer of 1 to 8. q is preferably an integer of 1 to 4, more preferably an integer of 1 to 2.

[0158] r is an integer of 0 to 4. Preferably, r is an integer of 0 to 2.

[0159] Specific examples of the compound (ii-3) having a (meth)acryloyloxy group include 2,2-(bisacryloyloxymethyl)propane-1-ol and 1,1-(bisacryloyloxymethyl)ethane-1-ol, and 1,1-(bisacryloyloxymethyl)ethane-1-ol is preferred.

[0160] <Monomer (1-3)>

[0161] Monomer (1-3) is a reaction product of the aforementioned (iii), and is an equimolar reaction product of a polyether polyol (iii-1) and a compound (iii-2) having a (meth)acryloyloxy group. The compound (iii-2) having a (meth)acryloyloxy group is a compound having one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule.

[0162] The monomer (1-3) is preferably a compound represented by formula (III).

[0163] R3 -NH-C(=O)-Z 1 ···(III)

[0164] In formula (III), R 3 It is a monovalent organic group having one or two (meth)acryloyloxy groups.

[0165] Z 1 It is a polyether polyol residue obtained by removing one hydrogen atom from one hydroxyl group in the polyether polyol.

[0166] As the monomer (1-3), a compound represented by formula (3) is more preferable.

[0167]

[0168] In formula (3), R 3 is the same as R in formula (III) 3 The same symbol has the same meaning.

[0169] R 32 It is preferably an alkylene group having 2 to 8 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms. 32 There are two or more types of R in one molecule. 32 In the case of -OR 32 -chains can be block or random. 32 It is preferably one or more selected from the group consisting of ethylene, propylene, 1,2-dimethylethylene, and 1-ethylethylene, and more preferably one or two selected from the group consisting of ethylene and propylene.

[0170] In addition, (OR 32 ) is also consistent with (OR 12 ) is preferably a unit based on monomer (a) having one epoxy group and an ether bond other than the ether bond of the epoxy group in one molecule. Preferred aspects of monomer (a) are the same as those for monomer (1-1).

[0171] c is an integer of 20 to 600. c is preferably an integer of 35 to 500, more preferably an integer of 65 to 250.

[0172] (Polyether polyol (iii-1))

[0173] The polyether polyol (iii-1) is a compound having an initiator residue, a polyether chain, and hydroxyl groups corresponding to the number of active hydrogen atoms in the initiator, obtained by ring-opening polymerization of an initiator having an active hydrogen-containing group and having two or more active hydrogen atoms with an alkylene oxide and / or the aforementioned monomer (a).

[0174] The alkylene oxide is preferably an alkylene oxide having 2 to 4 carbon atoms. Specific examples of the alkylene oxide having 2 to 4 carbon atoms include propylene oxide, ethylene oxide, 1,2-butylene oxide, and 2,3-butylene oxide.

[0175] In addition, as monomer (a), a monomer represented by the aforementioned formula (12) is preferred. Examples of the monomer represented by formula (12) include methyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, lauryl glycidyl ether, and hexyl glycidyl ether. From the viewpoint of better flexibility of the cured product of the obtained resin composition, butyl glycidyl ether and 2-ethylhexyl glycidyl ether are preferred.

[0176] From the viewpoint of adjusting the flexibility and strength of the cured product of the obtained resin composition, the ratio of the mass of the monomer (a) to the total mass of the alkylene oxide and the monomer (a) is preferably 0 to 90 mass %, more preferably 0 to 85 mass %, and even more preferably 10 to 80 mass %.

[0177] Examples of the active hydrogen-containing group possessed by the initiator include a hydroxyl group, a carboxyl group, and an amino group having a hydrogen atom bonded to a nitrogen atom. The active hydrogen-containing group possessed by the initiator is preferably a hydroxyl group, and more preferably an alcoholic hydroxyl group.

[0178] Examples of initiators having two or more active hydrogen atoms include water, polyols, polyphenols, polycarboxylic acids, and amine compounds having two or more hydrogen atoms bonded to nitrogen atoms. The initiator is preferably water or a dihydric aliphatic alcohol, more preferably a dihydric aliphatic alcohol. Furthermore, a polyoxyalkylene polyol having a lower molecular weight than the target polyether polyol may be used as the initiator.

[0179] The number of carbon atoms of the divalent aliphatic alcohol as an initiator is preferably 2 to 8. Specific examples of the divalent aliphatic alcohol as an initiator include polypropylene glycols such as ethylene glycol, propylene glycol, and dipropylene glycol, and 1,4-butanediol.

[0180] The oxyalkylene groups in the polyether polyol (iii-1) are preferably composed solely of oxypropylene groups or a combination of oxypropylene groups and other groups. The oxyalkylene groups other than oxypropylene groups are preferably oxyethylene groups and oxytetramethylene groups. The ratio of oxypropylene groups to the total oxyalkylene groups in the polyether polyol is preferably 50 to 100% by mass, more preferably 80 to 100% by mass.

[0181] In addition, when the initiator is a polyoxyalkylene polyol having a molecular weight lower than that of the target polyether polyol, the oxyalkylene group in the initiator is regarded as the oxyalkylene group in the obtained polyether polyol.

[0182] Among the polyether polyols (iii-1), low hydroxyl value, i.e., high molecular weight polyoxyalkylene polyols can be produced by ring-opening polymerization of an alkylene oxide having 3 or more carbon atoms, particularly propylene oxide, with an initiator in the presence of a double metal cyanide complex catalyst.

[0183] Examples of the low-hydroxyl-value polyoxyalkylene polyol include polyoxyalkylene polyols having a hydroxyl value of 40 mgKOH / g or less.

[0184] Among the polyether polyols (iii-1), polyoxyalkylene polyols having a low hydroxyl value of oxyethylene groups can be produced by using a polyoxyalkylene polyol having a high hydroxyl value of oxyethylene groups, for example, a hydroxyl value of 50 mgKOH / g or more, as an initiator and subjecting an alkylene oxide having 3 or more carbon atoms, especially propylene oxide, to ring-opening polymerization in the presence of a composite metal cyanide complex catalyst.

[0185] Among the polyether polyols (iii-1), polyoxyalkylene polyols having a high hydroxyl value and polyoxyalkylene polyols having a high hydroxyl value as initiators can also be produced using a base catalyst such as KOH.

[0186] The average number of hydroxyl groups in one molecule of polyether polyol (iii-1) is preferably 1.60 to 2.00, more preferably 1.70 to 2.00, and even more preferably 1.80 to 1.96. A polyether polyol having an average number of hydroxyl groups in one molecule of 1.60 to 2.00 is sometimes referred to as a polyether diol.

[0187] The hydroxyl value of the polyether polyol (iii-1) is preferably 1.6 to 18.1 mgKOH / g, more preferably 2.8 to 14 mgKOH / g.

[0188] The polyether polyol (iii-1) may be a mixture of two or more polyether polyols. In this case, each polyether polyol is preferably a polyether polyol within the above-mentioned scope, and each polyether polyol is preferably a polyether diol within the above-mentioned scope.

[0189] Examples of the polyether polyol (iii-1) include those represented by formula (3a).

[0190] H-(OR 32 ) c -OH ···(3a)

[0191] In formula (3a), R 32 and c have the same meanings as the same symbols in formula (3).

[0192] (Compound (iii-2) having a (meth)acryloyloxy group)

[0193] The compound (iii-2) having a (meth)acryloyloxy group is a compound having one isocyanate group and one or two (meth)acryloyloxy groups in one molecule. The compound (iii-2) having a (meth)acryloyloxy group is the same as the compound (i-2) having a (meth)acryloyloxy group in the monomer (1-1), and the preferred embodiment is the same.

[0194] 〔Second Unit〕

[0195] In addition to the first monomer, the resin composition preferably further comprises a second monomer, wherein the second monomer is one or more selected from the reaction products of (iv) and (v) below (hereinafter also referred to as "monomer (2-1)" and "monomer (2-2)"). That is, the resin composition preferably further comprises the first monomer and the second monomer. The second monomer in the resin composition may be a single monomer or a combination of two or more monomers.

[0196] (iv) a reaction product of a polyether polyol and a compound having a (meth)acryloyloxy group,

[0197] The compound having a (meth)acryloyloxy group is a compound having one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule.

[0198] The number of moles of the hydroxyl groups in the polyether polyol is equal to the number of moles of the compound having a (meth)acryloyloxy group.

[0199] (v) a reaction product of a polyol (A), a polyisocyanate and a compound having a (meth)acryloyloxy group,

[0200] The polyol (A) is at least one selected from polyoxyalkylene polyols, polyester polyols, poly(meth)acrylic polyols, polycarbonate polyols, castor oil-based polyols, and polyolefin polyols.

[0201] The compound having a (meth)acryloyloxy group is a compound having one group reactive with an isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule.

[0202] The total number of moles of the hydroxyl groups of the polyol (A) and the groups reactive with isocyanate groups of the compound having a (meth)acryloyloxy group is equal to the number of moles of the isocyanate groups of the polyisocyanate.

[0203] The second monomer is a polyfunctional urethane (meth)acrylate having two or more (meth)acryloyloxy groups, which functions as a crosslinking monomer that crosslinks the first monomer. A resin composition comprising the first and second monomers exhibits reduced cure shrinkage, and the cured product of the resin composition exhibits excellent flexibility.

[0204] The molecular weight of the second monomer is preferably 6,000 to 60,000, more preferably 8,000 to 40,000, and even more preferably 10,000 to 34,000. A molecular weight of 6,000 or greater facilitates flexibility in the cured product of the resin composition, while a molecular weight of 60,000 or less reduces the viscosity of the resin composition, making mixing of the resin composition easier.

[0205] <Single Element (2-1)>

[0206] Monomer (2-1) is a reaction product of the aforementioned (iv), and is a reaction product of a polyether polyol (iv-1) and a compound (iv-2) having a (meth)acryloyloxy group. The compound (iv-2) having a (meth)acryloyloxy group is a compound having one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule. The number of moles of hydroxyl groups in the polyether polyol (iv-1) is equal to the number of moles of the compound (iv-2) having a (meth)acryloyloxy group.

[0207] The monomer (2-1) is preferably a compound represented by formula (IV).

[0208] R 4 -NHC(=O)-Z 2 -C(=O)NH-R 4 ···(IV)

[0209] In formula (IV), R 4 It is a monovalent organic group having one or two (meth)acryloyloxy groups.

[0210] Z 2 It is a residue of a polyether polyol (iv-1) obtained by removing two hydrogen atoms from two hydroxyl groups in the polyether polyol (iv-1).

[0211] As the monomer (2-1), a compound represented by formula (4) is more preferable.

[0212]

[0213] In formula (4), R 4 have the same meanings as the same symbols in formula (IV).

[0214] R 42It is preferably an alkylene group having 2 to 8 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms. 42 There are two or more types of R in one molecule. 42 In the case of -OR 42 -chains can be block or random. 42 It is preferably one or more selected from the group consisting of ethylene, propylene, 1,2-dimethylethylene, and 1-ethylethylene, and more preferably one or two selected from the group consisting of ethylene and propylene.

[0215] In addition, (OR 42 ) is also consistent with (OR 12 ) is preferably a unit based on monomer (a) having one epoxy group and an ether bond other than the ether bond of the epoxy group in one molecule. Preferred aspects of monomer (a) are the same as those for monomer (1-1).

[0216] d is an integer of 20 to 600. d is preferably an integer of 35 to 500, more preferably an integer of 65 to 250.

[0217] The polyether polyol (iv-1) is the same as the polyether polyol (iii-1) in the monomer (1-3), and the preferred aspects are also the same.

[0218] The compound (iv-2) having a (meth)acryloyloxy group is the same as the compound (i-2) having a (meth)acryloyloxy group in the monomer (1-1), and preferred embodiments are also the same.

[0219] <Monomer (2-2)>

[0220] Monomer (2-2) is a reaction product of the aforementioned (v), and is a reaction product of a polyol (A), a polyisocyanate (v-1) and a compound (v-2) having a (meth)acryloyloxy group, wherein the polyol (A) is one or more selected from the group consisting of a polyether polyol, a polyester polyol, a poly(meth)acrylic polyol, a polycarbonate polyol, a castor oil-based polyol and a polyolefin polyol, and the compound (v-2) having a (meth)acryloyloxy group is a compound having one group reactive with an isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule, and the total number of moles of the hydroxyl group of the polyol (A) and the group reactive with an isocyanate group of the compound (v-2) having a (meth)acryloyloxy group is equal to the number of moles of the isocyanate group of the polyisocyanate (v-1).

[0221] As the monomer (2-2), a compound represented by formula (5) is preferable.

[0222]

[0223] In formula (5), R 5 It is a monovalent organic group having one or two (meth)acryloyloxy groups.

[0224] R 52 It is preferably an alkylene group having 2 to 8 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms. 52 There are two or more types of R in one molecule. 52 In the case of -OR 52 -chains can be block or random. 52 It is preferably one or more selected from the group consisting of ethylene, propylene, 1,2-dimethylethylene, and 1-ethylethylene, and more preferably one or two selected from the group consisting of ethylene and propylene.

[0225] In addition, (OR 52 ) is also consistent with (OR 12 ) is preferably a unit based on monomer (a) having one epoxy group and an ether bond other than the ether bond of the epoxy group in one molecule. Preferred aspects of monomer (a) are the same as those for monomer (1-1).

[0226] R 54 It is a divalent group obtained by removing two isocyanate groups from a diisocyanate. The diisocyanate is the same as the diisocyanate in the monomer (1-2), and the preferred embodiment is also the same.

[0227] e is an integer of 20 to 600. e is preferably an integer of 35 to 500, more preferably an integer of 65 to 250.

[0228] Among the polyols (A), the polyether polyol is the same as the polyether polyol (iii-1) among the monomers (1-3), and the preferred embodiments are also the same.

[0229] The polyether polyol, polyester polyol, poly(meth)acrylic polyol, polycarbonate polyol, castor oil-based polyol, and polyolefin polyol in the polyol (A) may be any of those described in

[0016] to

[0028] of JP-A-2020-37689 without particular limitation.

[0230] As the polyether polyol, a polymer polyol obtained by dispersing a polymer having units derived from a (meth)acrylate monomer in a polyether polyol may also be used. The polymer polyol may be a commercially available product, for example, the "ULTIFLOW (registered trademark)" series, the "SHARPFLOW (registered trademark)" series (all manufactured by Sanyo Chemical Industries, Ltd.), and the "Excenol (registered trademark)" series (manufactured by AGC Corporation).

[0231] Polyisocyanate (v-1) is a compound having two or more isocyanate groups in one molecule. As the polyisocyanate, a compound having two or three isocyanate groups in one molecule is preferred, and a diisocyanate is more preferred. As the diisocyanate, the same as the diisocyanate (ii-2) in monomer (1-2) is preferred.

[0232] Specific examples of the polyisocyanate (v-1) include tolylene diisocyanate, hexamethylene diisocyanate, diphenylmethylene diisocyanate, and isophorone diisocyanate. From the perspective of ease of adjusting the elongation and strength of the cured product of the resin composition, hexamethylene diisocyanate or isophorone diisocyanate is preferred.

[0233] The compound (v-2) having a (meth)acryloyloxy group is the same as the compound (ii-2) having a (meth)acryloyloxy group in the monomer (1-2), and preferred embodiments are also the same.

[0234] [Contents of the first monomer and the second monomer]

[0235] From the viewpoint of appropriate flexibility and repeated bending durability of the cured product of the resin composition, the content of the first monomer is preferably 50 to 98 parts by mass, more preferably 70 to 95 parts by mass, and even more preferably 80 to 90 parts by mass based on 100 parts by mass of the resin composition.

[0236] Monomer (1-1), monomer (1-2) and monomer (1-3) can be used alone or in combination of two or more. As the first monomer, it is more preferred to include one or more selected from monomer (1-1) and monomer (1-2). In 100 parts by mass of the first monomer, from the viewpoint of reducing the cure shrinkage of the resin composition and the flexibility of the cured product of the resin composition, the total content of monomer (1-1) and monomer (1-2) is preferably 50 parts by mass or more, more preferably 80 parts by mass or more, and particularly preferably 100 parts by mass. In this case, the content of monomer (1-1) is preferably 50 to 100 parts by mass relative to 100 parts by mass of the total content of monomer (1-1) and monomer (1-2).

[0237] When the resin composition contains a second monomer, from the viewpoint of appropriate flexibility and repeated bending durability of the cured product of the resin composition, the content of the second monomer is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 15 parts by mass or less relative to 100 parts by mass of the resin composition.

[0238] [Other ingredients]

[0239] From the viewpoints of the flexibility and repeated bending durability of the cured product of the resin composition, the resin composition may contain other components in addition to the first monomer and the second monomer. Examples of other components include monomers other than the first monomer and the second monomer (hereinafter also referred to as "other monomers"), polymerization initiators, and the like.

[0240] Furthermore, as required, optional components may include catalysts (tertiary amine compounds, quaternary ammonium compounds, tin laurate compounds, etc.), colorants such as pigments and dyes, silane coupling agents, tackifying resins, antioxidants, light stabilizers, metal inert agents, rust inhibitors, anti-aging agents, moisture absorbents, anti-hydrolysis agents, antistatic agents, foam stabilizers, fillers, etc. Furthermore, a solvent may be included.

[0241] These other components are blended in the resin composition in such a range that the effects of the present invention are not impaired.

[0242] The resin foam layer may contain hollow particles, and the air bubbles in the resin foam layer may be formed by utilizing the hollow parts of the hollow particles. In this case, the hollow particles are disposed in the resin composition.

[0243] <Other monomers>

[0244] The other monomer is a compound copolymerizable with the first monomer (when the resin composition contains the second monomer, with the first monomer and the second monomer), and may be used alone or in combination of two or more.

[0245] From the viewpoint of ease of copolymerization with the first monomer and the second monomer and ease of adjustment of the viscosity of the resin composition, examples of other monomers include (meth)acrylates such as alkyl (meth)acrylates, hydroxyl group-containing (meth)acrylates, and amino group-containing (meth)acrylates.

[0246] Examples of the alkyl (meth)acrylate include alkyl (meth)acrylates having a linear or branched alkyl group. The alkyl group preferably has 1 to 18 carbon atoms, more preferably 1 to 14 carbon atoms, and even more preferably 1 to 10 carbon atoms.

[0247] Examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-undecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, and n-tetradecyl (meth)acrylate.

[0248] Examples of the hydroxyl group-containing (meth)acrylate include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, caprolactone-modified (meth)acrylate, polyoxyethylene (meth)acrylate, and polyoxypropylene (meth)acrylate.

[0249] Examples of the amino group-containing (meth)acrylate include aminoethyl (meth)acrylate, tert-butylaminoethyl (meth)acrylate, and dimethylaminomethyl (meth)acrylate.

[0250] As other monomers, crosslinkable monomers having two or more functional groups that crosslink the first monomer may be used. The crosslinkable monomers may be used alone or in combination of two or more.

[0251] The functional group of the crosslinkable monomer is preferably one or more selected from the group consisting of a (meth)acryloyloxy group, an epoxy group, an isocyanate group, a carboxyl group, a hydroxyl group, a carbodiimide group, an oxazoline group, an aziridine group, a vinyl group, an amino group, an imino group, and an amide group. The functional group may be protected with a removable protecting group.

[0252] The number of the functional groups in one molecule of the crosslinkable monomer is preferably 2 to 4, more preferably 2 or 3.

[0253] Examples of cross-linking monomers include difunctional alkyl (meth)acrylates such as 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and neopentyl glycol di(meth)acrylate; difunctional (meth)acrylates having a polyoxyalkylene chain such as polyethylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, polyethylene glycol-polypropylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate; trifunctional or higher functional (meth)acrylates such as trimethylolpropane tri(meth)acrylate, ε-caprolactone-modified tri(acryloyloxyethyl)isocyanurate, pentaerythritol tri(meth)acrylate, and pentaerythritol penta(meth)acrylate; and triallyl isocyanurate. From the viewpoint of ease of copolymerization with the first monomer and the second monomer and ease of adjusting the viscosity of the resin composition, polypropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ε-caprolactone-modified tris(acryloyloxyethyl)isocyanurate, and triallyl isocyanurate are preferred, and polypropylene glycol di(meth)acrylate and ε-caprolactone-modified tris(acryloyloxyethyl)isocyanurate are more preferred.

[0254] When a cross-linking monomer is added, the content in the resin composition is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 1.0 to 5 parts by mass, relative to 100 parts by mass of the first monomer (or the first and second monomers when the resin composition contains the second monomer), from the viewpoint of the flexibility of the cured product of the resin composition at low temperatures.

[0255] <Polymerization Initiator>

[0256] The resin composition can be cured by light or heat. In the device manufacturing process, light curing is faster and does not require high temperatures, thus preventing damage to the device due to heat.

[0257] In the case of photocuring, it is preferable to contain a photopolymerization initiator.

[0258] From the viewpoint of controlling the polymerization reaction, the photopolymerization initiator is preferably one that can be used by ultraviolet irradiation with a wavelength of 380 nm or less.

[0259] Examples of the photopolymerization initiator include those described in paragraphs

[0147] to

[0151] of International Publication No. 2018 / 173896.

[0260] As the photopolymerization initiator, a hydrogen abstraction type photopolymerization initiator is preferably used, in which the photoexcited initiator forms an excited complex with a hydrogen donor in the system, thereby transferring hydrogen from the hydrogen donor. Specific examples of the hydrogen abstraction type photopolymerization initiator include benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 4-(meth)acryloyloxybenzophenone, 4-[2-((meth)acryloyloxy)ethoxy]benzophenone, 4-(meth)acryloyloxy-4'-methoxybenzophenone, methyl 2-benzoylbenzoate, and methyl benzoylformate.

[0261] In addition, as the photopolymerization initiator, from the viewpoint of high sensitivity to light, acylphosphine oxide-based photoinitiators such as phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)2,4,4-trimethylpentylphosphine oxide are preferred.

[0262] The thermal polymerization initiator may be a known thermal polymerization initiator used for polymerization of (meth)acrylates, and examples thereof include azo compounds such as 2,2'-azobisbutyronitrile and peroxides such as benzoyl peroxide. The thermal polymerization initiator may be used alone or in combination of two or more.

[0263] From the viewpoint of appropriately performing curing accompanying polymerization of the resin composition, the content of the polymerization initiator in the resin composition is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, and even more preferably 0.2 to 5 parts by mass, relative to 100 parts by mass of the total of the first monomer and the second monomer.

[0264] <Hollow particles>

[0265] The hollow particles are not particularly limited and may be hollow inorganic or organic microspheres, or hollow microspheres of an organic-inorganic composite. Examples of hollow inorganic microspheres include hollow glass microspheres, such as hollow glass microspheres; hollow silica microspheres, hollow alumina microspheres, and other metal compound hollow microspheres; and hollow ceramic microspheres, such as hollow ceramic microspheres. Examples of hollow organic microspheres include hollow resin microspheres, such as hollow acrylic microspheres, hollow vinylidene chloride microspheres, phenol microspheres, and epoxy microspheres.

[0266] The average particle size of the hollow particles is not particularly limited as long as it is equal to or smaller than the thickness of the resin foam layer, but is preferably 10 to 150 μm, more preferably 20 to 130 μm, and even more preferably 30 to 100 μm from the viewpoint of good impact absorption performance.

[0267] The average particle size of the hollow particles can be measured by, for example, a laser diffraction method or a low-angle laser light scattering method.

[0268] From the viewpoint of uniformly distributing the bubbles in the resin foam layer, the ratio of the average particle size of the hollow particles to the thickness of the resin foam layer (average particle size / thickness) is preferably 0.1 to 0.9, more preferably 0.2 to 0.85.

[0269] The density of the hollow particles is not particularly limited, but is preferably 0.01 to 0.4 g / cm from the viewpoint of uniform distribution of cells in the resin foam layer. 3 , more preferably 0.02 to 0.3 g / cm 3 .

[0270] The content of the hollow particles in the resin composition also depends on the density of the hollow particles. From the viewpoint of the impact absorbency, flexibility at low temperatures, and repeated bending durability of the resin foam layer, the content is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, and even more preferably 1 to 3 parts by mass per 100 parts by mass of the resin composition.

[0271] 〔Glass transition temperature〕

[0272] The glass transition temperature (Tg) of the cured product of the resin composition is preferably -55°C or lower, more preferably -58°C or lower, and even more preferably -60°C or lower. A Tg of -55°C or lower provides the cured product of the resin composition with superior low-temperature flexibility and repeated flexure durability. To ensure that the resin foam layer formed from the cured product of the resin composition exhibits excellent impact absorption performance, the lower limit of the Tg is preferably -85°C or higher, more preferably -80°C or higher.

[0273] In addition, the Tg of the cured product of the resin composition in the present invention can be a value obtained by using the Fox equation based on the Tg value of the homopolymer of each monomer component in the resin composition.

[0274] 〔bubble〕

[0275] The resin foam layer comprises a cured product of the resin composition and air bubbles. As described above, the air bubbles in the resin foam layer may be formed from the hollow portions of hollow particles blended into the resin composition. Alternatively, the air bubbles may be formed by mixing a gas or a foaming agent into the resin composition and then foaming and curing the resulting composition.

[0276] When cells are formed using hollow particles, it is easy to make the cell diameter uniform and to control the cell distribution using closed cells. From the viewpoint of sufficient shock absorption, the cell distribution is preferably uniform.

[0277] When foaming is performed to form cells, the cells are covered with the resin composition and do not have an outer shell, unlike hollow particles. Therefore, a resin foam layer having excellent flexibility and repeated bending durability can be easily obtained.

[0278] The cells in the resin foam layer may be closed cells, open cells, or both closed cells and open cells.

[0279] 〔Apparent density〕

[0280] From the viewpoint of sufficient impact absorption performance, the apparent density of the resin foam layer is preferably 0.3 to 0.8 g / cm 3 , more preferably 0.45 to 0.8 g / cm 3 , more preferably 0.6 to 0.79 g / cm 3 .

[0281] The apparent density is determined by measurement in accordance with JIS K 7222:2005.

[0282] 〔thickness〕

[0283] From the viewpoints of the impact absorbing performance of the impact absorbing sheet and the installation space in the equipment, the thickness of the resin foam layer is preferably 300 μm or less, more preferably 20 to 280 μm, and even more preferably 50 to 250 μm.

[0284] The impact-absorbing sheet of the present invention is preferably formed solely from a resin foam layer. Furthermore, to impart light-shielding properties and improve processability and handling, the resin foam layer may include other layers, such as a skin layer composed of various resins, on one or both sides. Examples of resins constituting the skin layer include the resins constituting the aforementioned resin composition, other acrylic resins, thermoplastic elastomers, polyolefin resins, polyester resins, urethane resins, and polyimide resins. Other layers may also include rubber, metal foil, and nonwoven fabrics.

[0285] The thickness of the other layer is preferably smaller than that of the resin foam layer within a range that does not impair the function of the resin foam layer. The thickness of the other layer is, for example, approximately 1 to 100 μm.

[0286] Thickness can be measured using a micrometer.

[0287] [Method for forming resin foam layer]

[0288] The formation of the resin foam layer is not particularly limited. When the cells in the resin foam layer are formed using hollow particles, the resin foam layer can be formed by, for example, applying a resin composition containing hollow particles onto a support such as a release film or a substrate and curing the resin composition.

[0289] The resin composition is prepared by mixing the first monomer, the hollow particles, and the second monomer and other components as needed. The mixing order of each component is not particularly limited. It should be noted that, from the viewpoints of operability such as mixing and coating, a solvent can be mixed in the resin composition and mixed. In this case, the solvent is preferably removed during or after curing.

[0290] The resin composition can be applied by any conventional method, including, but not limited to, slot die coating, reverse gravure coating, micro gravure coating, dipping, spin coating, brush coating, roll coating, and flexographic printing.

[0291] As described above, the resin composition may be cured by light curing or heat curing.

[0292] When the bubbles in the resin foam layer are formed by mixing gas, the gas can be mixed into the resin composition by mechanical foaming, and the bubble-containing resin composition is applied to a support such as a release film or substrate and cured.

[0293] As the resin composition at this time, from the viewpoint of forming uniform bubbles, etc., an emulsion in which a polymer is dispersed in a dispersion medium such as water can also be used. The emulsion is obtained by, for example, polymerizing the monomer components by emulsion polymerization, suspension polymerization, dispersion polymerization, etc. in the presence of a polymerization initiator, emulsifier, dispersion stabilizer, etc. which are compounded as needed. The emulsion can also be compounded with a foaming agent such as a surfactant as needed.

[0294] The dispersion medium of the emulsion preferably contains water. In addition to water, it may contain a polar solvent such as methanol, ethanol, isopropyl alcohol, acetone, dipropylene glycol, or tripropylene glycol. From the perspective of operability in the mechanical foaming method, the solid content of the emulsion is, for example, 30 to 70% by mass, preferably 35 to 60% by mass.

[0295] About mechanical foaming method, specifically, utilize the mixing mill of high-speed shear mode, vibration mode etc. to mix resin combination, and in this resin combination, mix gas.As gas, air, nitrogen, carbon dioxide, argon etc. can be used.Can use the device that makes pressurized gas ejection, make it mix in resin combination.The mixed amount of gas is preferably suitably adjusted according to the mode of obtaining resin foam layer with desired density.The bubble diameter in resin combination is roughly the same as the bubble diameter in resin foam layer, can be adjusted by compounding foaming agent etc. in resin combination or adjusting mixing time.

[0296] The coating method and curing of the resin composition are the same as in the case of forming the cells in the resin foam layer using hollow particles.

[0297] [How to use]

[0298] The impact-absorbing sheet of the present invention is suitable for use in electronic devices, particularly mobile devices such as smartphones, tablet computers, and laptop computers. Specifically, it is placed between the cover panel and housing of these mobile devices, between a liquid crystal or organic EL display device and its touchscreen, and on the back side of the display device to absorb impacts to these mobile devices and displays.

[0299] The impact-absorbing sheet of the present invention has excellent impact-absorbing performance even when thin, and thus contributes to thinning of electronic devices and preventing damage.

[0300] Furthermore, the impact-absorbing sheet of the present invention has excellent flexibility even at low temperatures, and can exhibit excellent impact-absorbing performance even in electronic devices used in low-temperature environments of 0°C or lower.

[0301] Furthermore, the impact-absorbing sheet of the present invention has excellent durability against repeated bending, and thus can continuously exhibit excellent impact-absorbing performance even in portions of a foldable device that bear loads due to repeated bending.

[0302] As needed, a resin sheet can be laminated on one or both sides of the impact-absorbing sheet. Examples of resins used in the resin sheet include polyolefin resins such as polyethylene and polypropylene, and thermoplastic resins such as polyester resins such as polyethylene terephthalate. Each resin sheet is preferably thinner than the impact-absorbing sheet, having a thickness of, for example, 10 to 300 μm, preferably 10 to 200 μm. The resin sheet can be bonded to the impact-absorbing sheet by thermocompression bonding, or alternatively, using an adhesive.

[0303] Alternatively, the shock absorbing sheet may be used as an adhesive tape by providing an adhesive material on at least a portion of one or both surfaces. The adhesive material of the adhesive tape allows the shock absorbing sheet to be easily bonded to components such as the housing of an electronic device.

[0304] The adhesive material comprises at least an adhesive layer, preferably consisting solely of an adhesive layer laminated on the surface of the impact-absorbing sheet. Alternatively, the adhesive material is a double-sided adhesive sheet comprising a substrate and adhesive layers disposed on both sides of the substrate, preferably adhered to the surface of the impact-absorbing sheet. Double-sided adhesive sheets can have one adhesive layer bonded to the impact-absorbing sheet and the other adhesive layer bonded to, for example, a component of an electronic device.

[0305] The adhesive constituting the adhesive layer is not particularly limited, and examples thereof include acrylic adhesives, urethane adhesives, and rubber adhesives. To achieve a thinner adhesive sheet, the thickness of the adhesive is preferably 5 to 200 μm, more preferably 7 to 150 μm. Furthermore, a release film such as release paper may be affixed to the adhesive layer to protect the adhesive layer of the adhesive sheet prior to use.

[0306] Example

[0307] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples.

[0308] [Manufacturing of resin composition]

[0309] According to the following Synthesis Examples and Production Examples, resin compositions for producing impact-absorbing sheet samples were produced.

[0310] 〔Determination of number average molecular weight〕

[0311] The number average molecular weight of the product obtained in the synthesis example was measured by gel permeation chromatography (GPC) under the following measurement conditions.

[0312] <Measurement Conditions>

[0313] Machine used: "HLC-8120GPC", manufactured by Tosoh Corporation

[0314] Columns used: Connect the following two columns in series

[0315] "TSKgel (registered trademark) G7000HXL", manufactured by Tosoh Corporation, 1 piece

[0316] "TSKgel (registered trademark) GMHXL", manufactured by Tosoh Corporation, 2 pieces

[0317] Column temperature: 40°C

[0318] Detector: Differential refractive index (RI) detector

[0319] Eluent: tetrahydrofuran

[0320] Flow rate: 0.8 mL / min

[0321] Sample concentration: 0.5% by mass

[0322] Sample injection volume: 100μL

[0323] Standard sample: polystyrene

[0324] [Raw material compound]

[0325] Details of the raw material compounds used in the Synthesis Examples and Production Examples are shown below.

[0326] DMC-TBA: zinc hexacyanocobaltate-tert-butyl alcohol complex

[0327] AOI: 2-acryloyloxyethyl isocyanate; "Karenz AOI", manufactured by Showa Denko K.K.

[0328] Photopolymerization initiator: Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide; "Irgacure (registered trademark) 819", manufactured by BASF

[0329] ADP-400: Polypropylene glycol diacrylate; "BLEMMER (registered trademark) ADP-400," manufactured by NOF Corporation; number average molecular weight approximately 400 (catalog value); Tg of the crosslinkable monomer and homopolymer is -18°C

[0330] M-325: ε-caprolactone-modified tris(acryloyloxyethyl) isocyanurate; "ARONIX (registered trademark) M-325," manufactured by Toagosei Co., Ltd.; crosslinkable monomer; homopolymer Tg is 195°C

[0331] BA: n-butyl acrylate; Tg of homopolymer is -54°C

[0332] MA: Methyl acrylate; Tg of homopolymer is -8°C

[0333] Hollow particles: "Expancel (registered trademark) 920DE80d30", manufactured by Japan Fillite Co., Ltd., average particle size 80 μm

[0334] [Synthesis example 1]

[0335] 0.2 g of DMC-TBA and 30 g of n-butanol were added to a pressure-resistant reactor equipped with a stirrer and a nitrogen inlet pipe. 3,970 g of propylene oxide was then added at a prescribed rate over 7 hours at 130°C under a nitrogen atmosphere. After confirming that the internal pressure of the pressure-resistant reactor had ceased to decrease, 4,000 g of polyoxypropylene monool having a hydroxyl value of 5.6 mgKOH / g (molecular weight converted to hydroxyl value: 10,000) and an average number of hydroxyl groups of 1.08 was obtained.

[0336] 964.9 g of the aforementioned polyoxypropylene monool and 13.1 g of AOI (NCO index: 100) were added to a reaction vessel equipped with a stirrer and a nitrogen inlet tube. The mixture was stirred at 70°C for 3 hours in the presence of 0.08 g of a 25% by mass toluene solution of bismuth 2-ethylhexanoate to obtain a product containing a monofunctional urethane acrylate (number average molecular weight: 16,000). The homopolymer Tg of this product was -65°C.

[0337] [Manufacturing Example 1] Manufacture of Resin Composition 1A

[0338] 100 parts by mass of the product obtained in Synthesis Example 1, 2 parts by mass of ADP-400, 1 part by mass of M-325, 0.3 parts by mass of a photopolymerization initiator, and 2 parts by mass of hollow particles were mixed to prepare a resin composition 1A.

[0339] [Manufacturing Example 2] Manufacture of Resin Composition 1B

[0340] Resin composition 1B was prepared by mixing 100 parts by mass of an emulsion (solid content: 50% by mass) of a polymer obtained by emulsion polymerization of the product obtained in Synthesis Example 1 and 0.3 parts by mass of a photopolymerization initiator.

[0341] [Manufacturing Example 3] Manufacture of Resin Composition 2A

[0342] 25 parts by mass of BA, 75 parts by mass of MA, and 0.3 parts by mass of a photopolymerization initiator were mixed and partially polymerized by ultraviolet irradiation. Then, 2 parts by mass of ADP-400, 1 part by mass of M-325, 0.3 parts by mass of a photopolymerization initiator, and 2 parts by mass of hollow particles were added and mixed to prepare a resin composition 2A.

[0343] [Manufacturing Example 4] Manufacture of Resin Composition 2B

[0344] Resin composition 2B was prepared by mixing 100 parts by mass of an aqueous dispersion (solid content: 50% by mass) of an acrylic polymer obtained by emulsion polymerization of 25 parts by mass of BA and 75 parts by mass of MA with 0.3 parts by mass of a photopolymerization initiator.

[0345] [Manufacturing of Impact-Absorbing Sheet Samples]

[0346] Using each of the resin compositions obtained in Production Examples 1 to 4 above, impact-absorbing sheet samples were prepared.

[0347] [Example 1]

[0348] The resin composition 1A was applied onto a release film (a silicone-coated polyethylene terephthalate film: "SP-PET-O1-75BU", manufactured by Mitsui Chemicals Tohcello, Ltd., with a thickness of 75 μm; the same shall apply hereinafter) and irradiated with ultraviolet light (illuminance of 100 mW / cm 2 , light intensity is 1000mJ / cm 2 ), and a sample of an impact absorbing sheet having a resin foam layer with a thickness of 200 μm was prepared.

[0349] [Example 2]

[0350] Resin composition 1B was stirred at room temperature (25°C) for 1 minute using a stirrer, and air was incorporated by mechanical foaming to form bubbles in the resin composition 1B. The bubbled resin composition 1B was applied to a release film and irradiated with ultraviolet light to produce a 200 μm thick impact-absorbing sheet sample having a resin foam layer.

[0351] [Example 3]

[0352] A shock-absorbing sheet sample was prepared in the same manner as in Example 1 except that the resin composition 2A was used instead of the resin composition 1A.

[0353] [Example 4]

[0354] A shock-absorbing sheet sample was prepared in the same manner as in Example 2 except that the resin composition 2B was used instead of the resin composition 1B.

[0355] [Evaluation of Impact-Absorbing Sheet Samples]

[0356] The impact-absorbing sheet samples obtained in Examples 1 to 4 were evaluated for the following items, and the evaluation results shown in Table 1 were obtained.

[0357] 〔Glass transition temperature〕

[0358] The values are calculated using the Fox equation based on the glass transition temperature (Tg) of the homopolymer of each monomer component in the resin composition and the amount of each monomer component. It should be noted that for Examples 1 and 2, the Tg values obtained in Synthesis Example 1 were used in the calculations when the product was considered as a monomer.

[0359] 〔Impact test〕

[0360] Prepare a test piece (20 mm × 20 mm, 200 μm thick) cut out from the impact-absorbing sheet sample and after peeling off the peeling film. Apply a total of 5 impacts to the test piece within 10 seconds using a vibrator-type impact tester (test conditions: the mass of the impactor is 96 g, the vibration angle is 47°, and the temperature is 23°C). Measure the initial impact absorption rate (the first impact absorption rate) S1[%] and the impact absorption rate after applying 5 impacts (the fifth impact absorption rate) S5[%], and use the value SA calculated by S5 / S1×100[%] as an indicator of repeated impact absorption. Evaluate as shown in the following evaluation criteria. If the evaluation is A, the impact absorption performance is judged to be excellent, and if the evaluation is B, the impact absorption performance is judged to be insufficient.

[0361] <Evaluation Criteria>

[0362] A: SA is more than 80%

[0363] B: SA less than 80%

[0364] [Repeated bending test]

[0365] A KAPTON film (polyimide film; "KAPTON (registered trademark) 200EN", manufactured by DuPont Toray, 50 μm thick) was attached to the surface of the impact-absorbing sheet sample opposite the release film. Next, the release film of the impact-absorbing sheet sample was peeled off, and the corona-treated surface of a corona-treated PET film (a corona-treated biaxially oriented polyethylene terephthalate film "Lumirror (registered trademark) S10" (manufactured by Toray Industries, Ltd.)) was attached to the release film to prepare a test piece (50 mm wide, 100 mm long, 200 μm thick).

[0366] The following test was conducted using a U-shaped surface bending tester ("DLDM111LH", manufactured by YUASASYSTEM; test conditions: room temperature (25°C), bending radius 1.5mm, bending 180° and releasing the operation as one operation, repeated 100,000 times at a speed of 60 times / min): the test piece was repeatedly bent into a U-shape at halfway along its length with the KAPTON film side of the test piece as the inner side.

[0367] The appearance of the test piece after the test was visually observed and evaluated according to the following evaluation criteria. If the evaluation was A or B, it was considered that there was no problem in practical use and the repeated bending durability was excellent. If it was C, the repeated bending durability was judged to be insufficient and unsuitable for practical use.

[0368] <Evaluation Criteria>

[0369] A: No peeling, lifting or cracking occurred, and there was no change in appearance.

[0370] B: One or more of peeling, lifting, and cracking slightly occurred.

[0371] C: One or more of peeling, lifting, and cracking occurred significantly.

[0372] [Static bending test at -20°C]

[0373] The same test piece used in the repeated bending test was placed on a semicircular plate with a diameter of 3 mm and a thickness of 3 mm, with the KAPTON film facing inward, so that its longitudinal direction extended along the semicircumference. The plate was secured with adhesive tape and allowed to stand at -20°C for 10 days.

[0374] The appearance of the test piece after the test was visually observed and evaluated according to the same evaluation criteria as the repeated bending test. If the evaluation was A or B, it was considered that the flexibility at low temperature was excellent, and if it was C, it was judged that the flexibility at low temperature was insufficient.

[0375] [Table 1]

[0376] Table 1

[0377]

[0378] As shown in Table 1, Examples 1 and 2 were excellent in impact absorption performance, repeated bending durability, and flexibility at low temperatures.

Claims

1. An impact-absorbing sheet comprising a resin foam layer formed by curing a resin composition containing a monofunctional urethane (meth)acrylate, wherein the monofunctional urethane (meth)acrylate is one or more monomers selected from the group consisting of reaction products of the following (i) to (iii). (i) an equimolar reaction product of a polyether monool and a compound having a (meth)acryloyloxy group, The compound having a (meth)acryloyloxy group is a compound having one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule; (ii) an equimolar reaction product of a polyether monool, a diisocyanate and a compound having a (meth)acryloyloxy group, The compound having a (meth)acryloyloxy group is a compound having one group reactive with an isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule; (iii) an equimolar reaction product of a polyether polyol and a compound having a (meth)acryloyloxy group, The compound having a (meth)acryloyloxy group is a compound having one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule.

2. The impact-absorbing sheet according to claim 1, wherein The molecular weight of the monomer is 3,000 to 30,000.

3. The impact-absorbing sheet according to claim 1 or 2, wherein: The cured product of the resin composition has a glass transition temperature of -55°C or lower.

4. The impact-absorbing sheet according to claim 1 or 2, wherein: The monomer is the reaction product of (i).

5. The impact-absorbing sheet according to claim 1 or 2, wherein: The resin foam layer contains hollow particles.

6. The impact-absorbing sheet according to claim 1 or 2, wherein: The resin foam layer is formed by a mechanical foaming method. 7 . The impact-absorbing sheet according to claim 1 , having a thickness of 300 μm or less. The impact-absorbing sheet according to claim 1 or 2, which is used for electronic equipment. 9 . The impact-absorbing sheet according to claim 1 , which is arranged on the back side of a display device.

10. An adhesive tape comprising: The impact-absorbing sheet according to any one of claims 1 to 9; and An adhesive material is provided on at least a portion of at least one surface of the impact-absorbing sheet.

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