WO2022130837A1

WO2022130837A1 - Shock absorbing sheet

Info

Publication number: WO2022130837A1
Application number: PCT/JP2021/041308
Authority: WO
Inventors: 牧人中村; 千登志鈴木
Original assignee: Ａｇｃ株式会社
Priority date: 2020-12-17
Filing date: 2021-11-10
Publication date: 2022-06-23
Also published as: JPWO2022130837A1; KR20230121725A; CN116547136A

Abstract

Provided is a shock absorbing sheet which has excellent shock absorbing performance, durability against repeated bending, and flexibility at low temperatures. The shock absorbing sheet comprises a resin foam layer obtained by curing a resin composition containing monofunctional urethane (meth)acrylate, wherein the monofunctional urethane (meth)acrylate is one or more monomers selected from reaction products of a compound containing a certain (meth)acryloyloxy group.

Description

Shock absorbing sheet

The present invention relates to a shock absorbing sheet suitable for electronic devices and the like.

Mobile devices such as smart phones, tablet terminals, and notebook computers may have their housings and display panels damaged due to the impact of being dropped or hit.
In order to prevent such damage, for example, between the cover panel and the housing, between a display device such as a liquid crystal display or organic electroluminescence (organic EL) and a touch screen panel, and on the back side of the display device. For example, a shock absorbing sheet is used.

As such a shock absorbing sheet, a foam sheet of an olefin resin or an acrylic resin typified by polyethylene is known (see, for example, Patent Document 1).

International Publication No. 2020/013258

In recent years, foldable mobile devices equipped with foldable displays, that is, foldable devices, have been developed. The shock absorbing sheet provided in the foldable device is required to have not only shock absorbing performance but also durability against repeated bending (hereinafter, also referred to as "repeated bending durability").
In addition, since mobile devices can be carried and used in various environments, the shock absorbing sheet provided on mobile devices has shock absorbing performance and repeated bending durability even in extremely cold environments at low temperatures of 0 ° C or lower. Flexibility that can be demonstrated is required.

However, it cannot be said that the conventional impact absorbing sheet made of foam sheet of olefin resin or acrylic resin has sufficient durability for repeated bending and flexibility at low temperature.

The present invention solves such a problem, and an object of the present invention is to provide a shock absorbing sheet having excellent shock absorbing performance, durability against repeated bending, and excellent flexibility at low temperature.

INDUSTRIAL APPLICABILITY According to the present invention, a resin foam layer manufactured by using a predetermined urethane acrylate having a polyether chain and a urethane bond can provide a shock absorbing sheet having excellent shock absorbing performance, repeated bending durability and flexibility at low temperature. Based on finding.

The present invention provides the following means.
[1] It has a resin foam layer obtained by curing a resin composition containing a monofunctional urethane (meth) acrylate, and the monofunctional urethane (meth) acrylate is obtained from the reaction products of the following (i) to (iii). A shock absorbing sheet that is one or more selected monomers.
(I) An equimolar reaction product of a compound having a (meth) acryloyloxy group and a polyether monool, and the above-mentioned compound having a (meth) acryloyloxy group has one isocyanate group in one molecule. A reaction product which is a compound having one or two (meth) acryloyloxy groups in one molecule.
(Ii) An equimolar reaction product of polyether monool, diisocyanate and a compound having a (meth) acryloyloxy group, wherein the compound having a (meth) acryloyloxy group has one isocyanate group in one molecule. A reaction product which is a compound having a group that reacts with and has 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, wherein the compound having a (meth) acryloyloxy group has one isocyanate group in one molecule. A reaction product which is a compound having one or two (meth) acryloyloxy groups in one molecule.
[2] The shock absorbing sheet according to [1], wherein the monomer has a molecular weight of 3,000 to 30,000.
[3] The shock 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.
[4] The shock absorbing sheet according to any one of [1] to [3], wherein the monomer is the reaction product of (i).
[5] The shock absorbing sheet according to any one of [1] to [4], wherein the resin foam layer contains hollow particles.
[6] The shock absorbing sheet according to any one of [1] to [5], wherein the resin foam layer is formed by a mechanical floss method.
[7] The shock absorbing sheet according to any one of [1] to [6], which has a thickness of 300 μm or less.
[8] The shock absorbing sheet according to any one of [1] to [7], which is used for electronic devices.
[9] The shock absorbing sheet according to any one of [1] to [8], which is arranged on the back side of the display device.
[10] An adhesive tape comprising the shock absorbing sheet according to any one of [1] to [9] and an adhesive material provided on at least a part of at least one surface of the shock absorbing sheet.

According to the present invention, it is possible to provide a shock absorbing sheet having excellent shock absorbing performance, durability against repeated bending, and excellent flexibility at low temperature.

The definitions and meanings of terms and notations in the present specification are shown below.
"(Meta) acryloyloxy group" is a general term for acryloyloxy group and methacryloyloxy group.
"(Meta) acrylate" is a general term for acrylate and methacrylate. Similarly, "(meth) acrylic acid" is a general term for acrylic acid and methacrylic acid.
The "functional number" means the number of (meth) acryloyloxy groups in one molecule unless otherwise specified. The "average number of functional groups" means the average number of (meth) acryloyloxy groups in one molecule having a formula amount based on a chemical formula or a number average molecular weight as one unit, unless otherwise specified.
The "monofunctional urethane (meth) acrylate" means a urethane (meth) acrylate in which the average number of functional groups in one molecule is substantially 1, and the average number of functional groups in one molecule is 0.7 to 1.4. Urethane (meth) acrylate, preferably 0.8 to 1.3, is a urethane (meth) acrylate having substantially one (meth) acryloyloxy group in one molecule, that is, a monofunctional urethane (meth). ) Considered as acrylate.
The "isomolar reaction product" means that the molar ratio of the reacting compound is substantially 1, and the molar ratio is 0.7 to 1.4, preferably 0.8 to 1.3. The reaction product is considered to be an equimolar reaction product.
Similarly, "equal number of moles" of reacting groups (or compounds) means that the molar ratio of reacting groups (or compounds) is substantially 1, which is 0.7. When it is ~ 1.4, preferably 0.8 ~ 1.3, it is considered that the number of moles of the reacting groups (or compounds) is equal.
The "hydroxyl value" is determined by measurement according to JIS K 1557: 2007.
The "molecular weight converted to hydroxyl value" is a value calculated from the formula of 56,100 / (hydroxyl value) × (number of active hydrogens of initiator).
The "NCO index" in the reaction between the isocyanate group-containing compound and the hydroxyl group-containing compound is a value expressed as a percentage of the equivalent ratio of the isocyanate group of the isocyanate group-containing compound to the hydroxyl group of the hydroxyl group-containing compound.
Unless otherwise specified, the "molecular weight" means a formula weight based on a chemical formula or, in the case of a compound having a molecular weight distribution, a number average molecular weight. The "number average molecular weight" is a polystyrene-equivalent molecular weight determined by gel permeation chromatography (GPC) based on a calibration curve prepared using a standard polystyrene sample.

The shock absorbing sheet of the present invention has a resin foam layer obtained by curing a resin composition containing a monofunctional urethane (meth) acrylate, and the monofunctional urethane (meth) acrylate is the following (i) to (iii). One or more monomers selected from the reaction products of (hereinafter, also referred to as "first monomer").
(I) An equimolar reaction product of a compound having a polyether monool and 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. Product.
(Ii) An equimolar reaction product of a compound having a polyether monool, a diisocyanate and a (meth) acryloyloxy group.
The compound having a (meth) acryloyloxy group has a group that reacts with one isocyanate group in one molecule, and has one or two (meth) acryloyloxy groups in one molecule. Is a reaction product.
(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. Product.

The shock absorbing sheet of the present invention having the resin foam layer as described above is excellent in shock absorbing performance, repeated bending durability and flexibility at low temperature.

[Resin foam layer]
The resin foam layer is obtained by curing a resin composition containing a monofunctional urethane (meth) acrylate, and contains a cured product of the resin composition and air bubbles.
The resin composition containing the monofunctional urethane (meth) acrylate can be photopolymerized or thermally polymerized by the (meth) acryloyloxy group of the monofunctional urethane (meth) acrylate. Further, since the monofunctional urethane (meth) acrylate has a flexible graft chain that does not contribute to cross-linking, a cured product having excellent flexibility can be obtained, and the resin foam layer made of the cured product is excellent. It is possible to demonstrate the shock absorption performance. Further, the cured product has a small temperature dependence of the storage elastic modulus in a wide temperature range of −20 to 80 ° C., and can maintain excellent flexibility even in a low temperature range of 0 ° C. or lower.
The (meth) acryloyloxy group of the monofunctional urethane (meth) acrylate is preferably an acryloyloxy group from the viewpoint of the curing rate of the resin composition.

[First monomer]
The monofunctional urethane (meth) acrylate is a reaction product of the above (i) to (iii) (hereinafter, “monomer (1-1)”, “monomer (1-2)” and “single amount”. It is one or more first monomers selected from (also referred to as "body (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 used alone or in combination of two or more.

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. When the molecular weight is 3,000 or more, the cured product of the resin composition tends to be flexible, and when it is 30,000 or less, the viscosity of the resin composition tends to be adjusted. When two or more kinds are used in combination as the first monomer, it is preferable that the molecular weight of each is within the above range.

<Monomer (1-1)>
The monomer (1-1) is the reaction product of the above (i), and is an equimolar reaction production of the polyether monool (i-1) and the compound (i-2) having a (meth) acryloyloxy group. A compound (i-2) having a (meth) acryloyloxy group, which has one isocyanate group in one molecule and one or two (meth) acryloyl in one molecule. It is a compound having an oxy group.

As the monomer (1-1), the compound represented by the formula (1) is preferable.

In formula (1), R ¹ is a monovalent organic group having one or two (meth) acryloyloxy groups.
R ¹² is preferably an alkylene group having 2 to 8 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms. Multiple R ^12s present in one molecule may be the same or different from each other. When two or more kinds of R ¹² are present in one molecule, the -OR ^12- chain may be block or random. R ¹² is preferably one or more selected from an ethylene group, a propylene group, a 1,2-dimethylethylene group and a 1-ethylethylene group, and more preferably one or more selected from an ethylene group and a propylene group.

Further, it is also preferable that (OR ¹² ) is a unit based on the monomer (a) described later, which has one epoxy group in one molecule and an ether bond other than the ether bond of the epoxy group. The unit based on the monomer (a) is preferably the unit represented by the formula (11). The monomer (a) may be used alone or in combination of two or more.

In formula (11), R ¹⁰¹ is a monovalent group represented by -R ¹⁰³ -OR ¹⁰⁴ , and R ¹⁰² is a hydrogen atom or a monovalent group represented by -R ¹⁰⁵ -OR ¹⁰⁶ . Is the basis of. R ¹⁰³ and R ¹⁰⁵ are independently linear or branched alkylene groups having 1 to 3 carbon atoms, and R ¹⁰⁴ and R ¹⁰⁶ are independently linear or branched alkyl groups having 1 to 18 carbon atoms. It is the basis.
As the alkylene group of R ¹⁰³ and R ¹⁰⁵ , a methylene group, an ethylene group, an n-propylene group and an isopropylene group are preferable, a methylene group and an ethylene group are more preferable, and a methylene group is further preferable.
The carbon atoms of R ¹⁰⁴ and R ¹⁰⁶ are independently preferably 1 to 14, more preferably 1 to 12, and even more preferably 2 to 10.
Examples of the linear alkyl group of R ¹⁰⁴ and R ¹⁰⁶ include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-octyl group, an n-decyl group, a lauryl group, a cetyl group and a stearyl group. A methyl group, an ethyl group, and an n-butyl group are preferable. The branched alkyl group has a structure in which a hydrogen atom (excluding a hydrogen atom bonded to a terminal carbon) in the linear alkyl group is substituted with an alkyl group. Examples of the alkyl group to be substituted include a methyl group and an ethyl group. As the branched alkyl group, a 2-ethylhexyl group is preferable.

As the monomer (a), the monomer represented by the formula (12) is preferable.

R ¹⁰¹ and R ¹⁰² in the formula (12) have the same meaning as the same symbol in the formula (11).

Examples of the monomer represented by the formula (12) include methyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, lauryl glycidyl ether, and hexyl glycidyl ether, and the flexibility of the cured product of the obtained resin composition is exemplified. Butyl glycidyl ether and 2-ethylhexyl glycidyl ether are preferable from the viewpoint of better properties.

In formula (1), R ¹³ is an alkyl group having 1 to 20 carbon atoms. R ¹³ preferably has an alkyl group having 1 to 8 carbon atoms, more preferably a methyl group, an ethyl group, and a butyl group, and even more preferably a butyl group.
a is an integer of 20 to 600. For a, an integer of 35 to 500 is preferable, and an integer of 65 to 250 is more preferable.

(Polyether monool (i-1))
The polyether monool (i-1) in the monomer (1-1) is an initiator having an active hydrogen-containing group and having one or more active hydrogens, and an alkylene oxide and / or the above. It is a compound having an initiator residue, a polyether chain, and a hydroxyl group corresponding to the number of active hydrogens of the initiator, which is obtained by ring-opening polymerization of the monomer (a).

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% by mass from the viewpoint of adjusting the flexibility and strength of the cured product of the resin composition. It is more preferably 0 to 85% by mass, further preferably 10 to 80% by mass.

As the alkylene oxide, an alkylene oxide having 2 to 8 carbon atoms is preferable, and an alkylene oxide having 2 to 4 carbon atoms is more preferable. Specific examples of the alkylene oxide include propylene oxide, ethylene oxide, 1,2-butylene oxide, and 2,3-butylene oxide.

Examples of the active hydrogen-containing group possessed by the initiator include a hydroxyl group, a carboxy group, and an amino group having one hydrogen atom bonded to a nitrogen atom. As the active hydrogen-containing group of the initiator, a hydroxyl group and a carboxy group are preferable, a hydroxyl group is more preferable, and an alcoholic hydroxyl group is further preferable.

Examples of the initiator having one active hydrogen include a monohydric alcohol, a monohydric phenol, a monovalent carboxylic acid, and an amine compound having one hydrogen atom bonded to a nitrogen atom. As the initiator, a monohydric aliphatic alcohol and a monovalent aliphatic carboxylic acid are preferable, and a monovalent aliphatic alcohol is more preferable. Further, polyoxyalkylene monool having a molecular weight lower than that of the desired polyether monool may be used as an initiator.

The carbon number of the monohydric aliphatic alcohol as an initiator is preferably 1 to 20 and more preferably 2 to 8. Specific examples of the monohydric aliphatic alcohol as an initiator include ethanol, propanol, 2-propanol and butanol.
The carbon number of the monovalent aliphatic carboxylic acid as an initiator is preferably 2 to 20 including the carbon atom of the carboxy group, and more preferably 2 to 8.

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 another group, and an oxyalkylene other than the oxypropylene group. As the group, an oxyethylene group is preferable.
The ratio of the oxypropylene group to the total oxyalkylene group in the polyether monool (i-1) is preferably 50 to 100% by mass, more preferably 80 to 100% by mass. When the initiator is a polyoxyalkylene monool having a lower molecular weight than the target polyether monool, the oxyalkylene group in the initiator is regarded as the oxyalkylene group in the obtained polyether monool.

In the polyether monool (i-1), the low hydroxyl value, that is, the high molecular weight polyoxyalkylene monool is an alkylene oxide having 3 or more carbon atoms as an initiator in the presence of a composite metal cyanide complex catalyst, particularly. , Propylene oxide can be produced by ring-opening polymerization.
Examples of the polyoxyalkylene monool having a low hydroxyl value include polyoxyalkylene monool having a hydroxyl value of 40 mgKOH / g or less.
The low hydroxyl group polyoxyalkylene monool having an oxyethylene group is a composite metal cyanide complex using a polyoxyalkylene monool having a high hydroxyl value having an oxyethylene group, for example, a polyoxyalkylene monool having a hydroxyl value of 50 mgKOH / g or more as an initiator. It 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 catalyst.
The polyoxyalkylene monool having a high hydroxyl value can be produced by the ring-opening polymerization in the presence of an alkaline catalyst such as potassium hydroxide.

In the production of polyoxyalkylene monool, the initiator and alkylene oxide to be charged into the reaction system are usually those having low water content obtained by removing water by degassing under reduced pressure or the like. Generally, the smaller the water content of the initiator in the production of polyoxyalkylene monool, the more preferably 500 mass ppm or less, and more preferably 300 mass ppm or less. When the water content is within the above range, the amount of polyoxyalkylene diol produced from water is suppressed, and as a result, the amount of by-products produced by the polyoxyalkylene diol is suppressed, and the obtained poly It is easy to adjust the upper limit of the average number of hydroxyl groups of oxyalkylene monool to 1.2 or less.

The water content of the polyether monool (i-1) used as a raw material for the monomer (1-1) is preferably as small as possible, preferably 300 mass ppm or less with respect to the polyether monool (i-1). 250 mass ppm or less is more preferable, and 50 to 200 mass ppm is further preferable. When the water content is within the above range, the formation of by-products between the water content and the isocyanate group-containing compound is small, and the stability of the reaction product monomer (1-1) is improved. Further, it is easy to suppress the change in appearance of the resin composition with time, and it is easy to obtain a cured product of the resin composition having good flexibility.

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.
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.

The polyether monool (i-1) in the monomer (1-1) may be a mixture of two or more kinds of polyether monools. In this case, it is preferable that each polyether monool is a polyoxyalkylene monool included in the above category.

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

In formula (1a), R ¹² , R ¹³ and a have the same meaning as the same symbol in formula (1).

((Meta) Compound having acryloyloxy group (i-2))
The compound having a (meth) acryloyloxy group (i-2) is a compound having one isocyanate group in one molecule and one or two (meth) acryloyloxy groups in one molecule. Is. As the compound (i-2) having a (meth) acryloyloxy group, a (meth) acrylate having an isocyanate group bonded to an aliphatic hydrocarbon group or an alicyclic hydrocarbon group is preferable, and an isocyanate alkyl (meth) acrylate is preferable. More preferred.
The carbon number of the alkylene group excluding the isocyanate group of the isocyanate alkyl group is preferably 8 or less, more preferably 4 or less.

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

In formula (1b), R ¹¹ is a hydrogen atom or a methyl group. R ¹¹ is preferably a hydrogen atom.
s is an integer of 1 to 4, and an integer of 1 to 2 is preferable.

Specific examples of the compound (i-2) having a (meth) acryloyloxy group include 2-isocyanate ethyl (meth) acrylate, isocyanate methyl methacrylate and the like. Examples of commercially available products include "Karenzu (registered trademark; hereinafter, notation omitted) AOI" and "Karenzu MOI" (all manufactured by Showa Denko KK).

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

In formula (1c), R ¹¹ is a hydrogen atom or a methyl group. R ¹¹ is preferably a hydrogen atom.
R ¹⁴ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R ¹⁴ is preferably a methyl group.
t is an integer from 1 to 8. t is preferably an integer of 1 to 4, more preferably an integer of 1 to 2.
u is an integer from 0 to 4. u is preferably an integer of 0 to 2.

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 "Karenzu"). BEI ”, manufactured by Showa Denko Co., Ltd.), and 1,1- (bisacryloyloxymethyl) ethyl isocyanate is preferable.

The monomer (1-1) is selected from the compound represented by the formula (1-1-1), the compound represented by the formula (1-1-2) and the formula (1-1-3). One or more is preferable.

In the formula (1-1-1), the formula (1-1-2) and the formula (1-1-3), m, n1 and n2 are each independently preferably an integer of 20 to 600, preferably 35 to 500. Is more preferred, and an integer of 65 to 250 is even more preferred.
Bu is a butyl group.

<Monomer (1-2)>
The monomer (1-2) is the reaction product of the above (ii) and has a polyether monool (ii-1), a diisocyanate (ii-2) and a (meth) acryloyloxy group (ii-). The equimolar reaction product of 3), the compound (ii-3) having a (meth) acryloyloxy group, has a group that reacts with one isocyanate group in one molecule, and is in one molecule. It is a compound having one or two (meth) acryloyloxy groups.

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

In formula (2), R ² is a monovalent organic group having one or two (meth) acryloyloxy groups.
R ²² is preferably an alkylene group having 2 to 8 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms. Multiple R ^22s present in one molecule may be the same or different from each other. When two or more kinds of R ²² are present in one molecule, the -OR ^22- chain may be block or random. R ²² is preferably one or more selected from an ethylene group, a propylene group, a 1,2-dimethylethylene group and a 1-ethylethylene group, and more preferably one or two selected from an ethylene group and a propylene group.
Further, (OR ²² ) is the same as (OR ¹² ) in the formula (1), the monomer (a) having one epoxy group in one molecule and an ether bond other than the ether bond of the epoxy group. It is also preferable that the unit is based on. The preferred embodiment of the monomer (a) is the same as that of the monomer (1-1).
R ²³ is an alkyl group having 1 to 20 carbon atoms. R ²³ preferably has an alkyl group having 2 to 8 carbon atoms, and more preferably a butyl group.
R ²⁴ is a divalent group obtained by removing two isocyanate groups from diisocyanate. Examples of diisocyanates will be described later.
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.

(Polyether monool (ii-1))
The polyether monool (ii-1) is the same as the polyether monool (i-1) in the monomer (1-1), and the preferred embodiment is also the same.

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

In formula (2a), R ²² , R ²³ and b have the same meaning as the same symbol in formula (2).

(Diisocyanate (ii-2))
Diisocyanate (ii-2) is a compound having two isocyanate groups in one molecule.
Examples of the diisocyanate (ii-2) include non-yellowing aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and various modified products of these diisocyanates (modified products having two isocyanate groups). The diisocyanate may be used alone or in combination of two or more.
As the diisocyanate (ii-2), one or more selected from aliphatic diisocyanates and alicyclic diisocyanates are preferable from the viewpoint of flexibility and repeated bending durability of the cured product of the resin composition.

Specific examples of the non-yellowing aromatic diisocyanate include xylylene diisocyanate and tetramethylxylylene diisocyanate.
Specific examples of the aliphatic diisocyanate include 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate and lysine diisocyanate.
Examples of the alicyclic diisocyanate include isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,5-norbornane diisocyanate and 2,6-norbornane diisocyanate.

Examples of the diisocyanate (ii-2) include a compound represented by the formula (2b).

In equation (2b), R ²⁴ has the same meaning as the same symbol in equation (2).
As the diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate are preferable from the viewpoint of flexibility and repeated bending durability of the cured product of the resin composition.

((Meta) Compound having acryloyloxy group (ii-3))
The compound (ii-3) having a (meth) acryloyloxy group has a group that reacts with one isocyanate group in one molecule, and one or two (meth) acryloyloxy in one molecule. It is a compound having a group.
Examples of the group that reacts with the isocyanate group include an amino group having a nitrogen atom to which a hydroxyl group and a hydrogen atom are bonded. The number of hydroxyl groups in the group that reacts with the isocyanate group and the number of hydrogen atoms bonded to the nitrogen atom are preferably one each. Further, as the group that reacts with the isocyanate group, a hydroxyl group bonded to an aliphatic hydrocarbon group or an alicyclic hydrocarbon group is preferable.

As the compound (ii-3) having a (meth) acryloyloxy group, hydroxyalkyl (meth) acrylate and hydroxycycloalkyl (meth) acrylate are preferable, and hydroxyalkyl (meth) acrylate having 8 or less carbon atoms of the hydroxyalkyl group. Is particularly preferable.

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

In formula (2c), R ²¹ is a hydrogen atom or a methyl group. R ²¹ is preferably a hydrogen atom.
p is an integer of 1 to 4. p is preferably an integer of 1 to 2.

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, and 4-hydroxy. Examples thereof include butyl (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) (above, Kyoeisha Chemical Co., Ltd.). ), 4-HBA (manufactured by Osaka Organic Chemical Industry Co., Ltd.).

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

In formula (2d), R ²¹ is a hydrogen atom or a methyl group. R ²¹ is preferably a hydrogen atom.
^R25 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R ²⁵ is preferably a methyl group.
q is an integer from 1 to 8. q is preferably an integer of 1 to 4, more preferably an integer of 1 to 2.
r is an integer from 0 to 4. r is preferably an integer of 0 to 2.

Specific examples of the compound (ii-3) having a (meth) acryloyloxy group include 2,2- (bis-acryloyloxymethyl) propan-1-ol and 1,1- (bisacryloyloxymethyl) ethane-1-. Alls are mentioned, with 1,1- (bisacryloyloxymethyl) ethane-1-ol being preferred.

<Monomer (1-3)>
The monomer (1-3) is the reaction product of the above (iii), and is an equimolar reaction product of the polyether polyol (iii-1) and the compound (iii-2) having a (meth) acryloyloxy group. The compound (iii-2) having a (meth) acryloyloxy group has one isocyanate group in one molecule and one or two (meth) acryloyloxy in one molecule. It is a compound having a group.

As the monomer (1-3), the compound represented by the formula (III) is preferable.
R ³ -NH-C (= O) -Z ¹ ... (III)
In formula (III), R ³ is a monovalent organic group having one or two (meth) acryloyloxy groups.
Z ¹ is a residue of the polyether polyol obtained by removing one hydrogen atom from one of the hydroxyl groups in the polyether polyol.

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

In formula (3), R ³ has the same meaning as the same symbol in R ³ in formula (III).
R ³² is preferably an alkylene group having 2 to 8 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms. The plurality of R ^32s present in one molecule may be the same as or different from each other. When two or more kinds of R ³² are present in one molecule, the chain of -OR ³² -may be block or random. R ³² is preferably one or more selected from an ethylene group, a propylene group, a 1,2-dimethylethylene group and a 1-ethylethylene group, and more preferably one or two selected from an ethylene group and a propylene group.
Further, (OR ³² ) is a monomer (a) having an epoxy group in one molecule and an ether bond other than the ether bond of the epoxy group, similarly to (OR ¹² ) in the formula (1). It is also preferable that the unit is based on. The preferred embodiment of the monomer (a) is the same as that of the monomer (1-1).
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.

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

As the alkylene oxide, an alkylene oxide having 2 to 4 carbon atoms is preferable. 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.
Further, as the monomer (a), the monomer represented by the above formula (12) is preferable, and as the monomer represented by the formula (12), methyl glycidyl ether, butyl glycidyl ether, 2-. Ethylhexyl glycidyl ether, lauryl glycidyl ether, and hexyl glycidyl ether are exemplified, and butyl glycidyl ether and 2-ethylhexyl glycidyl ether are preferable because the cured product of the obtained resin composition has better flexibility.

The ratio of the mass of the monomer (a) to the total mass of the alkylene oxide and the monomer (a) is 0 to 90% by mass from the viewpoint of adjusting the flexibility and strength of the cured product of the obtained resin composition. Preferably, 0 to 85% by mass is more preferable, and 10 to 80% by mass is further preferable.

Examples of the active hydrogen-containing group possessed by the initiator include a hydroxyl group, a carboxy group, and an amino group having a hydrogen atom bonded to a nitrogen atom. As the active hydrogen-containing group of the initiator, a hydroxyl group is preferable, and an alcoholic hydroxyl group is more preferable.

Examples of the initiator having two or more active hydrogens include water, a polyhydric alcohol, a polyhydric phenol, a polyvalent carboxylic acid, and an amine compound having two or more hydrogen atoms bonded to a nitrogen atom. As the initiator, water or a divalent fatty alcohol is preferable, and a divalent fatty alcohol is more preferable. Further, a polyoxyalkylene polyol having a molecular weight lower than that of the target polyether polyol may be used as an initiator.

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

The oxyalkylene group in the polyether polyol (iii-1) is preferably composed of only an oxypropylene group or a combination of an oxypropylene group and another group, and as an oxyalkylene group other than the oxypropylene group. Is preferably an oxyethylene group or an oxytetramethylene group. The ratio of the oxypropylene group to the total oxyalkylene group in the polyether polyol is preferably 50 to 100% by mass, more preferably 80 to 100% by mass.
When the initiator is a polyoxyalkylene polyol having a lower molecular weight than the target polyether polyol, the oxyalkylene group in the initiator is regarded as the oxyalkylene group in the obtained polyether polyol.

Among the polyether polyols (iii-1), the polyoxyalkylene polyol having a low hydroxyl value, that is, a high molecular weight, is an alkylene oxide having 3 or more carbon atoms as an initiator in the presence of a composite metal cyanide complex catalyst, particularly. , Propylene oxide can be produced by ring-opening polymerization.
Examples of the polyoxyalkylene polyol having a low hydroxyl value include a polyoxyalkylene polyol having a hydroxyl value of 40 mgKOH / g or less.
Among the polyether polyols (iii-1), the polyoxyalkylene polyol having a low hydroxyl group having an oxyethylene group has a high hydroxyl value having an oxyethylene group, for example, a polyoxyalkylene polyol having a hydroxyl value of 50 mgKOH / g or more. 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.
Among the polyether polyols (iii-1), the polyoxyalkylene polyol having a high hydroxyl value and the polyoxyalkylene polyol having a high hydroxyl value as an initiator can also be produced by using an alkaline catalyst such as KOH.

The average number of hydroxyl groups in one molecule of the polyether polyol (iii-1) is preferably 1.60 to 2.00, more preferably 1.70 to 2.00, still 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 may be referred to as a polyether diol.
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.

The polyether polyol (iii-1) may be a mixture of two or more kinds of polyether polyols. In this case, each polyether polyol is preferably a polyether polyol included in the above category, and each polyether polyol is preferably a polyether diol included in the above category.

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

In formula (3a), R ³² and c have the same meaning as the same symbol in formula (3).

((Meta) Compound having acryloyloxy group (iii-2))
The compound having a (meth) acryloyloxy group (iii-2) is a compound having one isocyanate group in one molecule and one or two (meth) acryloyloxy groups in one molecule. Is. 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 also the same. ..

[Second monomer]
In addition to the first monomer, the resin composition contains the following reaction products (iv) and (v) (hereinafter, "monomer (2-1)" and "monomer (2-2)". It is also preferable to contain a second monomer which is one or more selected from). That is, it is also preferable that the resin composition contains a first monomer and a second monomer. The second monomer in the resin composition may be used alone or in combination of two or more.
(Iv) A 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.
A reaction product in which the number of moles of the hydroxyl group of the polyether polyol is equal to the number of moles of the compound having the (meth) acryloyloxy group.
(V) A reaction product of a compound having a polyol (A), a polyisocyanate and a (meth) acryloyloxy group.
The polyol (A) is one or more selected from polyoxyalkylene polyols, polyester polyols, poly (meth) acrylic polyols, polycarbonate polyols, castor oil-based polyols and polyolefin polyols.
The compound having a (meth) acryloyloxy group has a group that reacts with one isocyanate group in one molecule, and has one or two (meth) acryloyloxy groups in one molecule. And
A reaction product in which the total number of moles of the hydroxyl group of the polyol (A) and the group reacting with the isocyanate group of the compound having the (meth) acryloyloxy group is equal to the number of moles of the isocyanate group of the polyisocyanate.

The second monomer is a polyfunctional urethane (meth) acrylate having two or more (meth) acryloyloxy groups, and can act as a crosslinkable monomer that crosslinks the first monomer. The resin composition containing the first monomer and the second monomer reduces the curing shrinkage rate of the resin composition, and the cured product of the resin composition has excellent flexibility.

The second monomer preferably has a molecular weight of 6,000 to 60,000, more preferably 8,000 to 40,000, and even more preferably 10,000 to 34,000. .. When the molecular weight is 6,000 or more, the flexibility of the cured product of the resin composition can be easily obtained, and when it is 60,000 or less, the viscosity of the resin composition becomes low and the resin composition can be easily mixed. Become.

<Monomer (2-1)>
The monomer (2-1) is the reaction product of the above (iv), and is the reaction product of the polyether polyol (iv-1) and the compound (iv-2) having a (meth) acryloyloxy group. The compound (iv-2) having a (meth) acryloyloxy group has one isocyanate group in one molecule and one or two (meth) acryloyloxy groups in one molecule. It is a compound having, and the number of moles of the hydroxyl group of the polyether polyol (iv-1) is equal to the number of moles of the compound (iv-2) having a (meth) acryloyloxy group.

As the monomer (2-1), a compound represented by the formula (IV) is preferable.
R ⁴ -NHC (= O) -Z ² -C (= O) NH-R ⁴ ... (IV)
In formula (IV), ^R4 is a monovalent organic group having one or two (meth) acryloyloxy groups.
Z ² is a residue of the polyether polyol (iv-1) obtained by removing two hydrogen atoms from the two hydroxyl groups in the polyether polyol (iv-1).

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

In equation (4), ^R4 has the same meaning as the same symbol in equation (IV).
R ⁴² is preferably an alkylene group having 2 to 8 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms. The plurality of R ^42s present in one molecule may be the same as or different from each other. When two or more types of R ⁴² are present in one molecule, the -OR ⁴² -chain may be block or random. R ⁴² is preferably one or more selected from an ethylene group, a propylene group, a 1,2-dimethylethylene group and a 1-ethylethylene group, and more preferably one or two selected from an ethylene group and a propylene group.
Further, (OR ⁴² ) is a monomer (a) having an epoxy group in one molecule and an ether bond other than the ether bond of the epoxy group, similarly to (OR ¹² ) in the formula (1). It is also preferable that the unit is based on. The preferred embodiment of the monomer (a) is the same as that of the monomer (1-1).
d is an integer of 20 to 600. For d, an integer of 35 to 500 is preferable, and an integer of 65 to 250 is more preferable.

The polyether polyol (iv-1) is the same as the polyether polyol (iii-1) in the monomer (1-3), and the preferred embodiment is also the same.

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 the preferred embodiment is also the same. ..

<Monomer (2-2)>
The monomer (2-2) is the reaction product of the above (v), and is a reaction of the polyol (A), the polyisocyanate (v-1) and the compound (v-2) having a (meth) acryloyloxy group. The product, the polyol (A) is one or more selected from polyether polyols, polyester polyols, poly (meth) acrylic polyols, polycarbonate polyols, castor oil-based polyols and polyolefin polyols, and (meth) acryloyloxy. The group-bearing compound (v-2) is a compound having a group that reacts with one isocyanate group in one molecule and having one or two (meth) acryloyloxy groups in one molecule. Yes, the total number of moles of the group that reacts with the hydroxyl group of the polyol (A) and the isocyanate group of the compound (v-2) having the (meth) acryloyloxy group, and the molar of the isocyanate group of the polyisocyanate (v-1). Is equal to the number.

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

In formula ( ⁵ ), R5 is a monovalent organic group having one or two (meth) acryloyloxy groups.
R ⁵² is preferably an alkylene group having 2 to 8 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms. The plurality of R ^52s present in one molecule may be the same or different from each other. When two or more types of R ⁵² are present in one molecule, the -OR ⁵² -chain may be block or random. R ⁵² is preferably one or more selected from an ethylene group, a propylene group, a 1,2-dimethylethylene group and a 1-ethylethylene group, and more preferably one or two selected from an ethylene group and a propylene group.
Further, (OR ⁵² ) is a monomer (a) having an epoxy group in one molecule and an ether bond other than the ether bond of the epoxy group, similarly to (OR ¹² ) in the formula (1). It is also preferable that the unit is based on. The preferred embodiment of the monomer (a) is the same as that of the monomer (1-1).
R ⁵⁴ is a divalent group obtained by removing two isocyanate groups from diisocyanate. The diisocyanate is the same as that of the diisocyanate in the monomer (1-2), and the preferred embodiment is also the same.
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.

Among the polyols (A), the polytatetel polyol is the same as the polyether polyol (iii-1) in the monomer (1-3), and the preferred embodiment is also the same.
The polyether polyol, polyester polyol, poly (meth) acrylic polyol, polycarbonate polyol, castor oil-based polyol, and polyolefin polyol in the polyol (A) are described in [0016] to [0028] of JP-A-2020-37689. You can use things without any restrictions.
As the polyether polyol, a polymer polyol in which a polymer having a unit based on a (meth) acrylate monomer is dispersed in a polyether polyol can also be used. The polymer polyol may be a commercially available product, for example, "Ultiflow (registered trademark)" series, "Sharpflow (registered trademark)" series (all manufactured by Sanyo Chemical Industries, Ltd.), "Exenol (registered trademark)". ) ”Series (manufactured by AGC Corporation) and the like.

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 preferable, and diisocyanate is more preferable. The diisocyanate is the same as that of the diisocyanate (ii-2) in the monomer (1-2), and the preferred embodiment is also the same.
Specific examples of the polyisocyanate (v-1) include tolylene diisocyanate, hexamethylene diisocyanate, diphenylmethylene diisocyanate, and isophorone diisocyanate. Hexamethylene diisocyanate or isophorone diisocyanate is preferable from the viewpoint of the elongation of the cured product of the resin composition and the ease of adjusting the strength.

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 the preferred embodiment is also the same. ..

[Contents of 1st monomer and 2nd monomer]
The content of the first monomer with respect to 100 parts by mass of the resin composition is preferably 50 to 98 parts by mass from the viewpoint of appropriate flexibility and repeated bending durability of the cured product of the resin composition. It is more preferably 70 to 95 parts by mass, and even more preferably 80 to 90 parts by mass.
The monomer (1-1), the monomer (1-2) and the monomer (1-3) may be used alone or in combination of two or more. It is more preferable that the first monomer contains at least one selected from the monomer (1-1) and the monomer (1-2). The total content of the monomer (1-1) and the monomer (1-2) in 100 parts by mass of the first monomer reduces the curing shrinkage rate of the resin composition and the cured product of the resin composition. From the viewpoint of flexibility, it 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 the monomer (1-1) is 50 to 100 parts by mass with respect to the total content of the monomer (1-1) and the monomer (1-2) by 100 parts by mass. Is preferable.

When the second monomer is contained in the resin composition, the second monomer is contained in 100 parts by mass of the resin composition from the viewpoint of appropriate flexibility and repeated bending durability of the cured product of the resin composition. The amount is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 15 parts by mass or less.

[Other ingredients]
The resin composition contains components other than the first monomer and the second monomer from the viewpoint of improving the flexibility and repeated bending durability of the cured product of the resin composition. May be good. Examples of other components include a first monomer and a monomer other than the second monomer (hereinafter, also referred to as “other monomer”), a polymerization initiator and the like.
Further, if necessary, catalysts (tertiary amine compounds, quaternary ammonium compounds, tin laurate compounds, etc.), colorants such as pigments and dyes, silane coupling agents, tackifier resins, antioxidants, light Stabilizers, metal deactivating agents, rust inhibitors, antiaging agents, hygroscopic agents, antioxidants, antistatic agents, foam stabilizers, fillers and the like may be contained as arbitrary components. Further, a solvent may be contained.
These other components in the resin composition are blended in a content within a range that does not impair the effects of the present invention.

Further, the resin foam layer contains hollow particles, and bubbles in the resin foam layer may be formed by the hollow portion of the hollow particles. In this case, the hollow particles are blended in the resin composition.

<Other monomers>
The other monomer is a compound that copolymerizes with the first monomer (when the resin composition contains the second monomer, the first monomer and the second monomer). One type may be used alone, or two or more types may be used in combination.
Examples of the other monomer include alkyl (for example, from the viewpoint of ease of copolymerization with the first monomer and the second monomer, ease of adjusting the viscosity of the resin composition, and the like. Examples thereof include (meth) acrylates such as meta) acrylates, hydroxyl group-containing (meth) acrylates, and amino group-containing (meth) acrylates.

Examples of the alkyl (meth) acrylate include an alkyl (meth) acrylate having a linear or branched alkyl group, and the number of carbon atoms of the alkyl group is, for example, preferably 1 to 18 and more preferably 1 to 14. 1 to 10 are more preferable.
Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth) acrylate. sec-butyl (meth) acrylate, t-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) Examples thereof include acrylate and n-tetradecyl (meth) acrylate.
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, and polyoxyethylene (meth). ) Acrylate, polyoxypropylene (meth) acrylate and the like can be mentioned.
Examples of the amino group-containing (meth) acrylate include aminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, and dimethylaminomethyl (meth) acrylate.

As the other monomer, a monomer having crosslinkability and having two or more functional groups for cross-linking the first monomer can also be used. The crosslinkable monomer may be used alone or in combination of two or more.
The functional group of the crosslinkable monomer is a (meth) acryloyloxy group, an epoxy group, an isocyanate group, a carboxy group, a hydroxy group, a carbodiimide group, an oxazoline group, an aziridine group, a vinyl group, an amino group and an imino group. And one or more selected from amide groups are preferred. The functional group may be protected by a deprotectable protecting group.
The number of the functional groups in one molecule of the crosslinkable monomer is preferably 2 to 4, more preferably 2 or 3.

Examples of the crosslinkable monomer include 1,6-hexanediol di (meth) acrylicate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylicate and the like. Bifunctional alkyl (meth) acrylate; polyoxy such as polyethylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, polyethylene glycol / polypropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, etc. Bifunctional (meth) acrylate having an alkylene chain; trimethylolpropanetri (meth) acrylate, ε-caprolactone-modified tris (acryloxyethyl) isocyanurate, pentaerythritol tri (meth) acrylate, pentaerythritol penta (meth) acrylate, etc. Trifunctional or higher (meth) acrylates; triallyl isocyanurate and the like can be mentioned. 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, trimethyl propantri ( Meta) acrylate, ε-caprolactone-modified tris (acryloxyethyl) isocyanurate and triallyl isocyanurate are preferable, and polypropylene glycol di (meth) acrylate and ε-caprolactone-modified tris (acryloxyethyl) isocyanurate are more preferable.

When a monomer having crosslinkability is blended, the content in the resin composition is the first monomer (the resin composition is the second) from the viewpoint of the flexibility of the cured product of the resin composition at a low temperature. When the above-mentioned monomer is contained, the content of the crosslinkable monomer is preferably 0.1 to 20 parts by mass with respect to 100 parts by mass of the first monomer and the second monomer). , 0.5 to 10 parts by mass is more preferable, and 1.0 to 5 parts by mass is further preferable.

<Polymer initiator>
The curing of the resin composition may be photocuring or thermosetting. When curing in the device manufacturing process, if it is photocured, the curing speed is high and it is not necessary to raise the temperature to a high temperature, so that the device is not damaged by heat.
In the case of photocuring, it is preferable to contain a photopolymerization initiator.

As the photopolymerization initiator, those that can be used by ultraviolet irradiation having a wavelength of 380 nm or less are preferable from the viewpoint of controlling the polymerization reaction. The photopolymerization initiator may be used alone or in combination of two or more.
Examples of the photopolymerization initiator include those described in paragraphs [0147] to [0151] of International Publication No. 2018/173896.
As the photopolymerization initiator, a hydrogen abstraction type photopolymerization initiator in which a photoexcited initiator and a hydrogen donor in the system form an excited complex and transfer hydrogen of the hydrogen donor is preferable. Specific examples of the hydrogen abstraction type photopolymerization initiator include benzophenone, 4-methyl-benzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 4-( Examples thereof include meth) acryloyloxybenzophenone, 4- [2-((meth) acryloyloxy) ethoxy] benzophenone, 4- (meth) acryloyloxy-4'-methoxybenzophenone, methyl 2-benzoylbenzoate, and methyl benzoylgitate.
Further, as the photopolymerization initiator, phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4) from the viewpoint of high sensitivity to light. , 6-trimethylbenzoyl) ethoxyphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) 2,4,4-trimethylpentylphosphine oxide and other acylphosphine oxide-based photoinitiators are preferred.

As the thermal polymerization initiator, a known thermal polymerization initiator used for the polymerization of (meth) acrylate can be used by a known method, for example, an azo compound such as 2,2'-azobisbutyronitrile, or peroxide. Examples thereof include peroxides such as benzoyl. The thermal polymerization initiator may be used alone or in combination of two or more.

The content of the polymerization initiator in the resin composition is 100 parts by mass in total of the first monomer and the second monomer from the viewpoint of appropriate progress of curing accompanying the polymerization of the resin composition. , 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, still more preferably 0.2 to 5 parts by mass.

<Hollow particles>
The hollow particles are not particularly limited, and may be hollow inorganic or organic microspheres, or may be microspheres of a hollow organic-inorganic complex. Examples of the hollow inorganic microspheres include a hollow glass balloon such as a hollow glass balloon, a hollow silica balloon, a hollow balloon made of a metal compound such as a hollow alumina balloon, and a porcelain hollow balloon such as a hollow ceramic balloon. Be done. Examples of the hollow organic microspheres include hollow acrylic balloons, hollow vinylidene chloride balloons, phenol balloons, epoxy balloons, and other resin-made hollow balloons.

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

The ratio (average particle size / thickness) between the average particle size of the hollow particles and the thickness of the resin foam layer is preferably 0.1 to 0.9 from the viewpoint of making the distribution of bubbles in the resin foam layer uniform. 0.2 to 0.85 is more preferable.

The density of the hollow particles is not particularly limited, but is preferably 0.01 to 0.4 g / cm ³ and 0.02 to 0.3 g / cm ³ from the viewpoint of making the distribution of bubbles in the resin foam layer uniform. More preferred.

The content of the hollow particles in the resin composition depends on the density of the hollow particles, but from the viewpoint of shock absorption of the resin foam layer, flexibility at low temperature, and repeated bending durability, the content of the hollow particles in 100 parts by mass of the resin composition , 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, still more preferably 1 to 3 parts by mass.

〔Glass-transition temperature〕
The cured product of the resin composition preferably has a glass transition temperature (Tg) of −55 ° C. or lower, more preferably −58 ° C. or lower, and even more preferably −60 ° C. or lower. When Tg is −55 ° C. or lower, the flexibility and repeated bending durability of the cured product of the resin composition at low temperature are more excellent. From the viewpoint of enabling the resin foam layer obtained from the cured product of the resin composition to exhibit excellent impact absorption performance, the lower limit of Tg is preferably −85 ° C. or higher, more preferably −80 ° C. or higher.
As the Tg of the cured product of the resin composition in the present invention, a value obtained by the Fox formula can be used based on the Tg value of the homopolymer in each monomer component in the resin composition.

[Bubble]
The resin foam layer contains a cured product and air bubbles of the resin composition. As described above, the bubbles in the resin foam layer may be formed by the hollow portions of the hollow particles blended in the resin composition, or the resin composition may be mixed with a gas or a foaming agent to foam and cure. It can also be formed by making it.
When bubbles are formed by hollow particles, it is easy to make the bubble diameter uniform, and it is easy to control the bubble distribution by closed bubbles. The bubble distribution is preferably uniform from the viewpoint of sufficient impact absorption.
When foaming to form bubbles, unlike the case of hollow particles, the bubbles are covered with a resin composition and do not have an outer shell, so that a resin foam layer having excellent flexibility and repeated bending durability is obtained. Easy to obtain.
The bubbles in the resin foam layer may be closed cells, open cells, or both closed cells and open cells.

[Apparent density]
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 , and 0.6 to 0. From the viewpoint of sufficient shock absorption performance. 79 g / cm ³ is more preferred.
The apparent density is determined by measurement based on JIS K 7222: 2005.

〔thickness〕
The thickness of the resin foam layer is preferably 300 μm or less, more preferably 20 to 280 μm, still more preferably 50 to 250 μm, from the viewpoint of the shock absorption performance of the shock absorbing sheet and the installation space in the device.
It is also preferable that the shock absorbing sheet of the present invention comprises only a resin foam layer. Further, from the viewpoint of imparting light-shielding property and improving workability and handleability, another layer such as a skin layer composed of various resins may be provided on one side or both sides of the resin foam layer. .. Examples of the resin constituting the skin layer include resins constituting the resin composition, other acrylic resins, thermoplastic elastomers, polyolefin resins, polyester resins, urethane resins, and polyimide resins. Further, examples of the other layer include rubber, metal foil, non-woven fabric and the like.
The thickness of the other layers is within a range that does not impair the function of the resin foam layer, and is preferably less than the thickness of the resin foam layer. The thickness of the other layer is, for example, about 1 to 100 μm.
The thickness can be measured using a micrometer.

[Method for forming the resin foam layer]
The formation of the resin foam layer is not particularly limited, but when bubbles are formed in the resin foam layer by hollow particles, for example, a resin composition containing hollow particles is applied onto a support such as a release film or a base material. Then, it can be formed by curing.
The resin composition is prepared by mixing a first monomer, hollow particles, and a second monomer and other components to be blended as needed. The mixing order of each component is not particularly limited. From the viewpoint of handleability for mixing and coating, a solvent may be mixed with the resin composition and mixed. In this case, it is preferable to remove the solvent at the time of curing or after curing.
The method for applying the resin composition is not particularly limited, and the resin composition can be applied by a conventional method. For example, a slot die method, a reverse gravure coating method, a microgravure method, a dip method, a spin coating method, a brush coating method, a roll coating method, a flexographic printing method and the like can be mentioned.
As described above, the curing of the resin composition may be photo-curing or thermosetting.

When the gas is mixed to form bubbles in the resin foam layer, for example, the gas is mixed into the resin composition by the mechanical floss method, and the resin composition containing the bubbles is formed into a release film or a base material. It can be formed by applying it on a support such as, etc. and curing it.
As the resin composition in this case, an emulsion in which the polymer is dispersed in a dispersion medium such as water can also be used from the viewpoint of uniform bubble formation and the like. The emulsion can be obtained by, for example, polymerizing a monomer component by a method such as emulsion polymerization, suspension polymerization, or dispersion polymerization in the presence of a polymerization initiator, an emulsifier, a dispersion stabilizer, etc., which are blended as necessary. Will be. A foaming agent or the like made of a surfactant or the like may be added to the emulsion, if necessary.
The dispersion medium of the emulsion preferably contains water, and may contain a polar solvent such as methanol, ethanol, isopropanol, acetone, dipropylene glycol, or tripropylene glycol in addition to water. The solid content of the emulsion is, for example, 30 to 70% by mass, preferably 35 to 60% by mass, from the viewpoint of handleability in the mechanical floss method.

Specifically, in the mechanical floss method, a gas is mixed into the resin composition while kneading the resin composition with a kneader such as a high-speed shearing method or a vibration method. As the gas, air, nitrogen, carbon dioxide, argon or the like is used. It may be mixed with the resin composition by using a device for discharging a pressurized gas. It is preferable to appropriately adjust the amount of gas mixed so that the resin foam layer can be obtained at a desired density. The bubble diameter in the resin composition is substantially the same as the bubble diameter in the resin foam layer, and can be adjusted by blending a foam stabilizer or the like in the resin composition or adjusting the kneading time.
The coating method and curing of the resin composition are the same as in the case of forming bubbles in the resin foam layer by the hollow particles.

[Usage mode]
The shock absorbing sheet of the present invention can be suitably used for, for example, electronic devices, especially mobile devices such as smart phones, tablet terminals, and notebook computers. Specifically, these mobile devices are arranged between the cover panel and the housing of these mobile devices, between a display device such as a liquid crystal display or an organic EL and a touch screen panel, and on the back side of the display device. Absorbs the impact on devices and display devices.
Since the shock absorbing sheet of the present invention is excellent in shock absorbing performance even if it is thin, it contributes to preventing damage while making the electronic device thinner.
Further, the shock absorbing sheet of the present invention is also excellent in flexibility at a low temperature, and can exhibit excellent shock absorbing performance even in an electronic device used in a low temperature environment of 0 ° C. or lower.
Further, since the shock absorbing sheet of the present invention is also excellent in durability against repeated bending, excellent shock absorbing performance can be continuously exhibited even in a place where a load is applied due to repeated bending of the foldable device. Can be done.

The shock absorbing sheet may be used by laminating a resin sheet on one side or both sides thereof, if necessary. Examples of the resin used for 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 shock absorbing sheet, and has a thickness of, for example, 10 to 300 μm, preferably 10 to 200 μm. The resin sheet can be adhered to the shock absorbing sheet by thermocompression bonding, and can also be adhered to the shock absorbing sheet by using an adhesive or the like.

Further, the shock absorbing sheet can be used as an adhesive tape by providing an adhesive material on at least a part of one surface or both sides. The adhesive material of the adhesive tape makes it possible to easily attach the shock absorbing sheet to parts such as housings of electronic devices.
The adhesive material preferably has at least an adhesive material layer and is preferably composed of only the adhesive material layer laminated on the surface of the shock absorbing sheet. Further, the pressure-sensitive adhesive is a double-sided pressure-sensitive adhesive sheet provided with a base material and pressure-sensitive adhesive layers provided on both sides of the base material, and is preferably attached to the surface of the shock absorbing sheet. In the double-sided adhesive sheet, one adhesive layer can be adhered to a shock absorbing sheet, and the other adhesive layer can be adhered to a component of an electronic device or the like.
The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited, and for example, an acrylic pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, or the like can be used. The thickness of the pressure-sensitive adhesive is preferably 5 to 200 μm, more preferably 7 to 150 μm, from the viewpoint of thinning the pressure-sensitive adhesive sheet. Further, a release film such as a release paper may be further bonded on the adhesive material to protect the adhesive material layer of the adhesive sheet before use with the release film.

Hereinafter, the present invention will be specifically described based on Examples, but the present invention is not limited to the following Examples.

[Manufacturing of resin composition]
A resin composition for producing a shock absorbing sheet sample is produced according to the following synthetic examples and production examples.

[Measurement of number average molecular weight]
The number average molecular weight of the product obtained in the synthetic example was measured by gel permeation chromatography (GPC) under the following measurement conditions.
<Measurement conditions>
-Equipment used: "HLC-8120GPC", manufactured by Tosoh Corporation-Columns used: The following two types of columns are connected in series in order "TSKgel (registered trademark) G7000HXL", manufactured by Tosoh Corporation, one "TSKgel (registered trademark)" ) GMHXL ”, manufactured by Tosoh Corporation, 2 pieces ・ Column temperature: 40 ℃
・ Detector: Differential refractive index (RI) detector ・ Eluent: tetrahydrofuran ・ Flow velocity: 0.8 mL / min ・ Sample concentration: 0.5% by mass
-Sample injection amount: 100 μL
・ Standard sample: Polystyrene

[Raw material compound]
Details of the raw material compounds used in the synthetic examples and the production examples are as follows.
-DMC-TBA: Zinc hexcyanocobaltate-tert-butanol complex-AOI: 2-acryloyloxyethyl isocyanate; "Karenzu AOI", manufactured by Showa Denko Co., Ltd.-Photopolymerization initiator: phenylbis (2,4) 6-trimethylbenzoyl) phosphinoxide; "Irgacure (registered trademark) 819", manufactured by BASF ・ ADP-400: polypropylene glycol diacrylate; "Blemmer (registered trademark) ADP-400", manufactured by Nichiyu Co., Ltd .; number average molecular weight Approximately 400 (catalog value); crosslinkable monomer, homopolymer Tg-18 ° C.
M-325: ε-caprolactone-modified tris (acryloxyethyl) isocyanurate; "Aronix® M-325", manufactured by Toagosei Co., Ltd .; crosslinkable monomer; homopolymer Tg 195 ° C.
BA: n-butyl acrylate; homopolymer Tg-54 ° C.
MA: Methyl acrylate; homopolymer Tg-8 ° C
-Hollow particles: "Expansel (registered trademark) 920DE80d30", manufactured by Nippon Philite Co., Ltd., average particle diameter 80 μm

[Synthesis Example 1]
In a pressure resistant reactor equipped with a stirrer and a nitrogen introduction tube, 0.2 g of DMC-TBA and 30 g of n-butanol were added, and 3970 g of propylene oxide was added at a constant rate at 130 ° C. over 7 hours under a nitrogen atmosphere. I put it in. After confirming that the decrease in the internal pressure of the pressure resistant reactor had stopped, 4000 g of polyoxypropylene monool having a hydroxyl value of 5.6 mgKOH / g (molecular weight conversion in terms of hydroxyl value of 10,000) and an average number of hydroxyl groups of 1.08 was obtained.
In a reaction vessel equipped with a stirrer and a nitrogen introduction tube, 964.9 g of the polyoxypropylene monool and 13.1 g of AOI (NCO index 100) were added, and a 25 mass% toluene solution of bismuth 2-ethylhexanoate was added. In the presence of .08 g, the mixture was stirred at 70 ° C. for 3 hours to obtain a product containing monofunctional urethane acrylate (number average molecular weight 16,000). The homopolymer Tg of this product is −65 ° C.

[Production Example 1] Production of Resin Composition 1A 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 the photopolymerization initiator, and hollow. 2 parts by mass of particles are mixed to prepare a resin composition 1A.

[Production Example 2] Production of Resin Composition 1B An emulsion which is an aqueous dispersion (solid content 50% by mass) of 100 parts by mass of a polymer obtained by emulsion polymerization of the product obtained in Synthesis Example 1 and photopolymerization. 0.3 parts by mass of the initiator is mixed to prepare a resin composition 1B.

[Production Example 3] Production of Resin Composition 2A 25 parts by mass of BA, 75 parts by mass of MA, and 0.3 parts by mass of a photopolymerization initiator are mixed, irradiated with ultraviolet rays to partially polymerize, and then ADP-400 2 A resin composition 2A is prepared by adding 1 part by mass of M-325, 0.3 part by mass of a photopolymerization initiator, and 2 parts by mass of hollow particles and mixing them.

[Production Example 4] Production of Resin Composition 2B An emulsion which is an aqueous dispersion (solid content 50% by mass) of 100 parts by mass of an acrylic polymer obtained by emulsion polymerization of 25 parts by mass of BA and 75 parts by mass of MA, and light. 0.3 parts by mass of the polymerization initiator is mixed to prepare a resin composition 2B.

[Manufacturing of shock absorbing sheet sample]
A shock absorbing sheet sample is prepared using each of the resin compositions obtained in Production Examples 1 to 4.

[Example 1]
The resin composition 1A is applied onto a release film (silicone-coated polyethylene terephthalate film: "SP-PET-O1-75BU", manufactured by Mitsui Chemicals Tocello Co., Ltd., thickness 75 μm; the same applies hereinafter) and ultraviolet rays (illuminance). By irradiating with 100 mW / cm ² and a light amount of 1000 mJ / cm ² ), a shock absorbing sheet sample having a resin foam layer with a thickness of 200 μm is prepared.

[Example 2]
The resin composition 1B was stirred at room temperature (25 ° C.) for 1 minute with a stirrer, and air was mixed by the mechanical floss method to form bubbles in the resin composition 1B. The resin composition 1B in which bubbles are formed is applied onto a release film and irradiated with ultraviolet rays to prepare a shock absorbing sheet sample having a resin foam layer having a thickness of 200 μm.

[Example 3]
A resin composition 2A is used instead of the resin composition 1A, and a shock absorbing sheet sample is prepared in the same manner as in Example 1 except for the resin composition 1A.

[Example 4]
A resin composition 2B is used instead of the resin composition 1B, and a shock absorbing sheet sample is prepared in the same manner as in Example 2 except for the resin composition 1B.

[Evaluation of shock absorbing sheet sample]
When the following items are evaluated for the shock absorbing sheet samples obtained in Examples 1 to 4, the evaluation results shown in Table 1 can be obtained.

〔Glass-transition temperature〕
The value calculated by the Fox formula was used based on the glass transition temperature (Tg) and the blending amount of the homopolymer of each monomer component in the resin composition. For Examples 1 and 2, the value of Tg in which the product obtained in Synthesis Example 1 was regarded as a monomer was used in the calculation.

[Impact test]
A test piece (20 mm × 20 mm, thickness 200 μm) from which the release film has been peeled off is prepared by cutting out from the shock absorbing sheet sample. This test piece is subjected to a total of 5 impacts within 10 seconds with a pendulum type impact tester (test conditions: impact element mass 96 g, swing angle 47 °, temperature 23 ° C). The initial impact absorption rate (first impact absorption rate) S1 [%] and the impact absorption rate after five impacts (fifth impact absorption rate) S5 [%] were measured, and S5 / S1 × The value SA calculated at 100 [%] was used as an index of repeated shock absorption. Evaluate as shown in the evaluation criteria below. If it is evaluation A, it is determined that the impact absorption performance is excellent, and if it is evaluation B, it is determined that the impact absorption performance is not sufficient.
<Evaluation criteria>
A: SA is 80% or more B: SA is less than 80%

[Repeat bending test]
A Kapton film (polyimide film; "Kapton (registered trademark) 200EN", manufactured by Toray DuPont Co., Ltd., thickness 50 μm) is attached to the surface of the shock absorbing sheet sample opposite to the release film. Next, the release film of the shock absorbing sheet sample was peeled off, and a corona-treated PET film (biaxially stretched polyethylene terephthalate film "Lumirror (registered trademark) S10" (manufactured by Toray Industries, Inc.) was subjected to corona treatment) on this surface. A test piece (width 50 mm, length 100 mm, thickness 200 μm) is prepared by laminating the corona-treated surfaces.
U-shaped planar bending tester ("DLDM111LH", manufactured by Yuasa System Equipment Co., Ltd .; test conditions: room temperature (25 ° C), bending radius 1.5 mm, bending 180 ° C open once, 60 times / min Repeat 100,000 times at the same speed) with the Kapton film side side of the test piece inside, and repeat the operation of bending in a U shape at the half position in the length direction.
Visually observe the appearance of the test piece after the test and evaluate as shown in the following evaluation criteria. If it is evaluation A or evaluation B, there is no practical problem and it can be said that it is excellent in repeated bending durability, and if it is evaluation C, it is judged that the repeated bending durability is not sufficient and it is not suitable for practical use.
<Evaluation criteria>
A: No peeling, floating or cracking occurs, and there is no change in appearance.
B: One or more of peeling, floating and cracking occurred slightly.
C: One or more of peeling, floating and cracking occurred remarkably.

[Static bending test at -20 ° C]
Using the same test piece as in the repeated bending test, the test piece is in close contact with the surface on the Kapton film side inside so that the length direction of the test piece is along the semicircle with a diameter of 3 mm and the semicircle with a thickness of 3 mm. Let me. It is fixed in this state with an adhesive tape and allowed to stand at −20 ° C. for 10 days.
The appearance of the test piece after the test is visually observed and evaluated according to the same evaluation criteria as in the repeated bending test. If it is evaluation A or evaluation B, it can be said that the flexibility at low temperature is excellent, and if it is evaluation C, it is determined that the flexibility at low temperature is not sufficient.

As shown in Table 1, Examples 1 and 2 are excellent in shock absorption performance, repeated bending durability, and flexibility at low temperature.

Claims

It has a resin foam layer obtained by curing a resin composition containing a monofunctional urethane (meth) acrylate, and the monofunctional urethane (meth) acrylate is selected from the reaction products of (i) to (iii) below. A shock absorbing sheet that is a monomer of seeds or more.
(I) An equimolar reaction product of a compound having a polyether monool and 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. Product.
(Ii) An equimolar reaction product of a compound having a polyether monool, a diisocyanate and a (meth) acryloyloxy group.
The compound having a (meth) acryloyloxy group has a group that reacts with one isocyanate group in one molecule, and has one or two (meth) acryloyloxy groups in one molecule. Is a reaction product.
(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. Product.
The shock absorbing sheet according to claim 1, wherein the monomer has a molecular weight of 3,000 to 30,000.
The shock 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.
The shock absorbing sheet according to any one of claims 1 to 3, wherein the monomer is the reaction product of (i).
The shock absorbing sheet according to any one of claims 1 to 4, wherein the resin foam layer contains hollow particles.
The shock absorbing sheet according to any one of claims 1 to 5, wherein the resin foam layer is formed by a mechanical floss method.
The shock absorbing sheet according to any one of claims 1 to 6, which has a thickness of 300 μm or less.
The shock absorbing sheet according to any one of claims 1 to 7, which is used for electronic devices.
The shock absorbing sheet according to any one of claims 1 to 8, which is arranged on the back side of the display device.
An adhesive tape comprising the shock absorbing sheet according to any one of claims 1 to 9 and an adhesive material provided on at least a part of at least one surface of the shock absorbing sheet.