WO2018174085A1

WO2018174085A1 - Curable composition, sheet and laminate produced using same, and image display device

Info

Publication number: WO2018174085A1
Application number: PCT/JP2018/011170
Authority: WO
Inventors: 大樹田畑
Original assignee: 三菱ケミカル株式会社
Priority date: 2017-03-22
Filing date: 2018-03-20
Publication date: 2018-09-27
Also published as: JP2019059910A; KR20190124318A; TW201841948A; CN110431174A

Abstract

Provided is a sheet which can exhibit good adhesiveness and retentivity, high transparency and water vapor barrier properties, and contains an isobutylene polymer (A) and an acrylate-based polymer (B), wherein the acrylate-based polymer (B) contains a monofunctional acrylate unit and a polyfunctional acrylate unit as structural units, at least one of maximum points of loss tangent (tanδ) in a shear measurement of the sheet at a frequency of 1 Hz falls within the range from -30°C to 30°C, and the haze of the sheet is 2.0% or less.

Description

Curable composition, sheet, laminate using the same, and image display device

The present invention relates to a sheet having adhesive strength, holding power, transparency and water vapor barrier property, and further relates to a curable composition for producing this sheet.

In recent years, curved or foldable display devices using organic light emitting diodes (OLEDs) and quantum dots (QDs) have been developed and are being widely commercialized.
Such a display device has a structure in which a plurality of film-like constituent members are bonded with a transparent optical adhesive (OCA) sheet. However, conventionally used acrylic OCA sheets have various problems due to lack of moisture-proof performance, and problems such as corrosion and migration of metal electrodes, and new material-based OCA sheets have been demanded.

As a polymer material that can solve the above-described problem, a polymer (referred to as “isobutylene polymer”) containing isobutene as a polymerization component and a copolymerization component can be given.
The isobutylene polymer has a feature that the water vapor barrier property is particularly high as a general-purpose soft resin, but the cohesive force is too small to be applied to the resin composition, so that the adhesive residue, low-temperature flow, insufficient holding power, etc. There was a problem.

As one of the methods for making full use of such an isobutylene polymer having a low cohesive force, there is known a method for improving cohesive force by polymerizing an acrylate after mixing a monomer such as acrylate with the isobutylene polymer. .

For example, Non-Patent Document 1 discloses a composition having a semi-IPN structure consisting of a network of isobutylene polymer and polycyclohexyl methacrylate (PCHMA), which is a monofunctional acrylate, and this composition has a low temperature flow. It is disclosed that the water vapor barrier property inherent in the isobutylene polymer is suppressed.

Patent Document 1 discloses a pressure-sensitive adhesive composition containing a sealing resin such as an isobutylene polymer, a polyfunctional acrylate, and a specific silane compound, and a pressure-sensitive adhesive film obtained from this pressure-sensitive adhesive composition has an excellent water vapor content. It describes that it has barrier properties and transparency.

Special table 2016-527377

Although the pressure-sensitive adhesive sheet composed of the isobutylene polymer and the polyfunctional acrylate disclosed in Patent Document 1 can have excellent water vapor barrier properties, the glass transition temperature is too low to obtain a sufficient pressure-sensitive adhesive force. I had a problem that I couldn't.
As a method of increasing the glass transition temperature, a method of blending a large amount of a tackifier such as petroleum resin is known, and even in Example 1 of Patent Document 1, about 25% by mass of a hydrogenated DCPD-based tackifier is present. It has been added. However, when such a large amount of tackifier is blended, the glass transition temperature can be increased, but the holding power as a property capable of maintaining the adhesion state for a long period of time is lowered.

In addition, the isobutylene polymer / DCPA-based composition containing tricyclodecane dimethanol diacrylate (DCPA) exemplified in the example of Patent Document 1 described above has a refractive index of the cured product equal to the refractive index of the isobutylene polymer. Since it is very close, the transparency of the composition can be maintained to some extent. However, when such an isobutylene polymer / DCPA composition is observed with a transmission electron microscope (TEM), the compatibility of the isobutylene polymer and DCPA is not good, and a DCPA cured product having a size of 1 μm or more is dispersed. In such a state, there is a possibility that a problem occurs in holding power and transparency.

In the system shown in Non-Patent Document 1, when the content ratio of the isobutylene polymer is large, the characteristics of the isobutylene polymer appear remarkably, and it is difficult to obtain a pressure-sensitive adhesive sheet having sufficient adhesion and holding power. there were.

The present invention provides a sheet having good adhesive strength, good holding power, excellent transparency, and excellent water vapor barrier properties, and further a curable composition for producing this sheet. To do.

The present invention is a sheet comprising an isobutylene polymer (A) and an acrylate polymer (B), wherein the acrylate polymer (B) has a unit structure represented by the following formula (1) as a structural unit. Each of the sheet has a functional acrylate unit and a polyfunctional acrylate unit, and the sheet has at least one maximum point of loss tangent (tan δ) in shear measurement at a frequency of 1 Hz in a range of −30 ° C. to 30 ° C., and has a haze. A sheet that is 2.0% or less is proposed.

(In the formula, R represents a hydrocarbon group, and R ′ represents hydrogen (H) or a methyl group (CH ₃ ), respectively).

The present invention also provides a curable composition containing 5 parts by mass or more and less than 100 parts by mass of an acrylate monomer with respect to 100 parts by mass of the isobutylene polymer (A), and the monofunctional acrylate monomer and the polyfunctional acrylate are used as the acrylate monomer. The present invention proposes a curable composition having a monomer and containing the polyfunctional acrylate in the curable composition in an amount of 0.5% by mass or more and less than 10% by mass.

The curable composition proposed by the present invention can be cured to produce the sheet proposed by the present invention. And since the sheet proposed by the present invention contains a monofunctional acrylate unit having a unit structure represented by the above formula (1) as a structural unit and an acrylate polymer (B) having a polyfunctional acrylate unit, A semi-IPN (interpenetrating polymer network) structure can be formed between the isobutylene polymer (A) and the acrylate polymer (B), and both water vapor barrier properties and transparency can be achieved. Furthermore, since at least one maximum point of loss tangent (tan δ) in shear measurement at a frequency of 1 Hz is in the range of −30 ° C. to 30 ° C., a sheet having excellent adhesion and holding power can be obtained. Property, holding power, transparency, and water vapor barrier property can be improved. Therefore, by using this sheet as a constituent member of an image display device or the like, it is possible to contribute to the thinning of the image display device or the like.

6 is a graph showing loss tangents (tan δ) of sheets (samples) obtained in Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-2, that is, sheets (samples) after curing treatment. It is the photograph which observed the sheet | seat (sample) obtained in Example 2-1, ie, the sheet | seat (sample) after a hardening process, with the transmission electron microscope (1000 times). It is the photograph which observed the sheet | seat (sample) obtained in Example 2-1, ie, the sheet | seat (sample) after a hardening process, with the transmission electron microscope (5000 times). It is the photograph which observed the sheet | seat (sample) obtained in Example 2-3, ie, the sheet | seat (sample) after a hardening process, with the transmission electron microscope (2000 times). It is the photograph which observed the sheet | seat (sample) obtained in Example 2-3, ie, the sheet | seat (sample) after a hardening process, with the transmission electron microscope (5000 times). It is the photograph which observed the sheet | seat (sample) obtained by the comparative example 2-1, ie, the sheet | seat (sample) after a hardening process with the transmission electron microscope (1000 times). It is the photograph which observed the sheet | seat (sample) obtained by the comparative example 2-2, ie, the sheet | seat (sample) after a hardening process, with the transmission electron microscope (1000 times).

Hereinafter, the present invention will be described in detail. However, the contents of the present invention are not limited to the embodiments described below.

[This sheet]
A sheet according to an example of an embodiment of the present invention (referred to as “the present sheet”) is a sheet including an isobutylene polymer (A) and an acrylate polymer (B).

<Isobutylene polymer (A)>
The isobutylene polymer (A) constituting this sheet is a polymer having an isobutylene skeleton in the main chain or side chain, and has a structural unit of the following formula (2).

The isobutylene polymer (A) has a function of improving the water vapor barrier property of the sheet.

As the isobutylene polymer (A), an isobutylene polymer which is a homopolymer of isobutylene, a copolymer of isobutylene and isoprene, a copolymer of isobutylene and n-butene, a copolymer of isobutylene and butadiene, and these copolymers And halogenated butyl rubber obtained by bromination or chlorination. These polymers can be used singly or in combination of two or more.

Among these, from the viewpoint of improving the durability and weather resistance of the sheet and reducing the water vapor transmission rate, the isobutylene polymer (A) may be an isobutylene polymer, an isobutylene / isoprene copolymer, or a combination thereof. Is preferred.

The isobutylene / isoprene copolymer has, in its molecule, a repeating unit derived from isobutylene [—CH ₂ —C (CH ₃ ) ₂ —] and a repeating unit derived from isoprene [—CH ₂ —C (CH ₃ ) ═CH. A synthetic rubber having —CH ₂ —].
The content of repeating units derived from isoprene in the isobutylene / isoprene copolymer is usually from 0.1 to 99 mol%, preferably from 0.5 to 50 mol%, more preferably from all repeating units. 1 to 10 mol%.
If the repeating unit derived from isoprene in the isobutylene / isoprene copolymer is in the above range, it is preferable because this sheet having excellent moisture resistance can be obtained.

The type of isobutylene / isoprene copolymer is not particularly limited. Examples thereof include regenerated isobutylene / isoprene copolymer and synthetic isobutylene / isoprene copolymer. Among these, a synthetic isobutylene / isoprene copolymer is preferable.

Examples of the method for synthesizing the isobutylene polymer include a method in which a monomer component such as isobutylene is polymerized in the presence of a Lewis acid catalyst such as aluminum chloride or boron trifluoride.
Moreover, a commercial item can also be used as an isobutylene polymer (A). Examples of commercially available products include Vistanex (manufactured by Exxon Chemical Co.), Hycar (manufactured by Goodrich), Oppanol (manufactured by BASF), Tetrax (manufactured by JXTG), Nippon Polybutene (manufactured by JXTG), and the like. .

The weight average molecular weight (Mw) of the isobutylene polymer (A) is preferably 1,000 to 2,000,000 g / mol, more preferably 1,500 g / mol or more or 1,500,000 g / mol or less. Among them, it is more preferably 2,000 g / mol or more and 1,000,000 g / mol or less, especially 50,000 g / mol or more, especially 100,000 g / mol or more, especially 120,000 g / mol or more.
Since the isobutylene polymer weight average molecular weight (Mw) is an isobutylene polymer (A) having a molecular weight of 1,000 g / mol or more, the fluidity of the curable composition forming the sheet becomes appropriate, and the sheet shape It becomes easy to hold the shape after molding. Moreover, a uniform structure | tissue is easy to be obtained because it is an isobutylene polymer (A) whose weight average molecular weight (Mw) is 2,000,000 g / mol or less.
Here, the weight average molecular weight (Mw) is a value measured by gel permeation chromatography using tetrahydrofuran as a solvent (GPC analysis) and converted to standard polystyrene.

The isobutylene polymer (A) can also be used in combination of two or more types of isobutylene polymers (A) having different average molecular weights. For example, an isobutylene polymer having a weight average molecular weight of less than 100,000 g / mol and an isobutylene polymer having a weight average molecular weight of 100,000 g / mol or more are used in combination as an isobutylene polymer having a bimodal molecular weight distribution. be able to.
Thus, even if the original is a separate raw material, the weight average molecular weight of the whole isobutylene polymer (A) is 1,000 to 2,000,000 g / mol, more preferably 1,500 to 1,500,000. 000 g / mol, more preferably 2,000 to 1,000,000 g / mol.

Examples of commercially available products having a weight average molecular weight of less than 100,000 g / mol include trade name: Tetrax (JXTG), trade name: Nisseki Polybutene (JXTG), and trade name: Hymor (JXTG). As a commercial product having a weight average molecular weight of 100,000 g / mol or more, trade name: Opanol (BASF) can be mentioned.

<Acrylate polymer (B)>
The acrylate polymer (B) constituting the sheet includes, as structural units, a monofunctional acrylate unit having a unit structure represented by the following formula (1) (also simply referred to as “monofunctional acrylate”) and a polyfunctional acrylate unit (simply Those having “polyfunctional acrylate”) are preferred.

(Monofunctional acrylate)
In folding display applications, etc., it may be required to lower the Tg of this sheet. In such a case, the acrylate polymer (B) preferably has at least two types of monofunctional acrylates. By using two or more types of monofunctional acrylates, the number of carbon atoms in the side chain becomes uneven, and the Tg of the sheet can be lowered. Moreover, it becomes possible to adjust Tg of this sheet to a desired temperature range by adjusting the blending ratio of two or more types of monofunctional acrylates.
For example, in some formulations, when isostearyl (iso-C18) acrylate is used alone as a monofunctional acrylate, the Tg of the sheet is about -2 ° C, while isostearyl (iso-C18) acrylate and cetyl (n When C16) acrylate is blended at a mass ratio of 1: 1, the Tg of the sheet can be reduced to around -20 ° C.

The monofunctional acrylate is preferably a monofunctional acrylate having a long-chain alkyl chain having 10 or more carbon atoms from the viewpoint of compatibility with the isobutylene polymer (A).
As a monofunctional acrylate having a long-chain alkyl chain having 10 or more carbon atoms, a monofunctional aliphatic acrylate which is an acrylate having one (meth) acryloyloxy group and having a long-chain alkyl chain having 10 or more carbon atoms The structure is shown in the following formula (3).

In the above formula (3), R represents a long-chain alkyl group having 10 or more carbon atoms.
In the above formula, R ′ is hydrogen (H) or a methyl group (CH ₃ ).

The long chain alkyl group (R) having 10 or more carbon atoms is an alkyl group having 10 or more carbon atoms in the main chain. For example, a decyl group (C ₁₀ ), an undecyl group (C ₁₁ ), a dodecyl group (C ₁₂ ), a tridecyl group (C ₁₃ ), a tetradecyl group (C ₁₄ ), a pentadecyl group (C ₁₅ ), a hexadecyl group (C ₁₆ ), heptadecyl _{(C 17),} octadecyl _{(C 18),} can be exemplified nonadecyl _{(C 19)} or the like.

The carbon number of the main chain in the long chain alkyl group (R) is preferably 20 or less, particularly 18 or less. If the number of carbon atoms is 18 or less, crystallization between monofunctional aliphatic acrylates hardly occurs, and transparency due to low haze and high total light transmittance is easily exhibited. On the other hand, if the main chain has 10 or more carbon atoms, the long-chain alkyl group (R) may have a branched alkyl group. In general, a branched alkyl group is less likely to be crystallized in a normal temperature region than a straight chain alkyl group, and transparency is easily exhibited.

Further, if the long-chain alkyl group (R) is composed of two or more different combinations, crystallization can be suppressed and transparency can be improved.

The acrylate polymer (B) preferably contains a monofunctional acrylate in the range of 60 to 90% by mass, more preferably 70% by mass or more and 90% by mass or less. By setting it as such a range, creep resistance can also be improved, maintaining the transparency of this sheet | seat.

The content of the monofunctional acrylate with respect to the entire sheet is preferably 3% by mass or more. The creep resistance of this sheet | seat can be improved because it is 3 mass% or more. From such a viewpoint, the content of the monofunctional acrylate with respect to the entire sheet is more preferably 5% by mass or more, and more preferably 10% by mass or more. On the other hand, about the upper limit, it is preferable that content of monofunctional acrylate is 50 mass% or less. By being 50 mass% or less, the water vapor | steam barrier property and impact energy absorptivity of this sheet | seat can be improved. From this viewpoint, the content of the monofunctional acrylate is more preferably 40% by mass or less, and among them, 35% by mass or less, particularly 30% by mass or less, and particularly preferably 25% by mass or less.

The acrylate polymer (B) contains at least one monofunctional acrylate which is a branched alkyl group as R in the above formula (1) from the viewpoint of lowering the crystallinity of the side chain and improving the transparency. Is preferred.

(HSP distance)
The Hansen solubility parameter (HSP) distance between the isobutylene polymer (A) and the monofunctional acrylate of the acrylate polymer (B) is preferably 5.0 or less, more preferably 4.5 or less. Further, it is particularly preferably 3.8 or less.
If the Hansen solubility parameter (HSP) distance between the isobutylene polymer (A) and the monofunctional acrylate of the acrylate polymer (B) is 5.0 or less, the isobutylene polymer (A) and the acrylate polymer (B ), And the deterioration of transparency due to bleed out and increased dispersion diameter can be suppressed.

The HSP of the monofunctional acrylate is preferably at a position where the HSP distance to the isobutylene polymer (A) is 5.0 or less, and more preferably at a position of 4.5 or less.
Examples of monofunctional acrylates having an HSP distance of 5.0 or less with the isobutylene polymer (A) include, for example, isostearyl acrylate, isohexadecyl acrylate, stearyl acrylate, hexadecyl acrylate, isotetradecyl acrylate, tetradecyl acrylate , Isododecyl acrylate, dodecyl acrylate, isodecyl acrylate, and the like.

Here, the “hansen solubility parameter (HSP)” is an index representing the solubility of how much a certain substance is soluble in another certain substance.
HSP is a three-dimensional space in which the solubility parameter introduced by Hildebrand is divided into three components: a dispersion term δD, a polar term δP, and a hydrogen bond term δH. The dispersion term δD indicates the effect due to the dispersion force, the polar term δP indicates the effect due to the dipole force, the hydrogen bond term δH indicates the effect due to the hydrogen bond force,
δD: Energy derived from intermolecular dispersion force δP: Energy derived from intermolecular polar force δH: Energy derived from intermolecular hydrogen bonding force (Here, each unit is MPa ^0.5 .)

The definition and calculation of HSP are described in the following documents.
Charles M. Hansen, Hansen Solubility Parameters: A Users Handbook (CRC Press, 2007).

The dispersion term reflects the van der Waals force, the polar term reflects the dipole moment, and the hydrogen bond term reflects the action of water, alcohol, etc. Those having similar vectors by HSP can be determined to have high solubility, and the similarity of vectors can be determined by the distance of the Hansen solubility parameter (HSP distance). In addition, Hansen's solubility parameter can be an index not only for determining solubility, but also for determining how much a certain substance is likely to exist in another certain substance, that is, how good the dispersibility is.

In the present invention, HSP [δD, δP, δH] can be easily estimated from its chemical structure by using, for example, computer software Hansen Solubility Parameters in Practice (HSPIP). Specifically, it is obtained from the chemical structure by the Y-MB method implemented in HSPiP. When the chemical structure is unknown, the chemical structure is obtained by the sphere method implemented in HSPiP from the result of the dissolution test using a plurality of solvents.

HSP distance (Ra) is to example solute HSP of (acrylate polymer in the present invention _{(B)) (δD 1,} δP 1, δH 1) and, HSP solvent (isobutylene polymer in the present invention (A)) the _{_{(δD 2, δP 2, δH}} 2) when formed into a can be calculated by the following equation.
HSP distance (Ra) = {4 × ( δD 1 -δD 2) 2 + (δP 1 -δP 2) 2 + (δH 1 -δH 2) 2} 0.5

(Polyfunctional acrylate)
When the acrylate polymer (B) contains a polyfunctional acrylate, the network of the acrylate polymer (B) can be adjusted, and as a result, the plateau elastic modulus of the sheet can be adjusted. By adjusting the plateau elastic modulus, it is possible to adjust the ease of wetting when this sheet is attached and the ease of entrainment of bubbles.
The plateau elastic modulus can be increased as the addition amount of the polyfunctional acrylate is increased, and the plateau elastic modulus can be decreased as the molecular weight of the polyfunctional acrylate is increased.

The polyfunctional acrylate is an acrylate having two or more (meth) acryloyloxy groups, and at least (meth) acryloyloxy groups are bonded via a hydrocarbon group.
As an example of the polyfunctional acrylate, the structure of the bifunctional aliphatic acrylate is shown in the following formula (4).

In the formula (4), R is hydrogen (H) or methyl group (CH _3).
X is an aliphatic hydrocarbon group or an alicyclic hydrocarbon group.

The HSP of the polyfunctional acrylate is preferably at a position where the HSP distance from the isobutylene polymer (A) is 9.0 or less, and more preferably at a position of 8.0 or less.
By setting the HSP distance within the above range, troubles related to transparency and adhesiveness such as bleed out can be suppressed.

In the polyfunctional acrylate, the aliphatic hydrocarbon group or alicyclic hydrocarbon group (X) is preferably a hydrocarbon group that does not contain multiple bonds from the viewpoint of long-term stability of the sheet.

Examples of the polyfunctional acrylate include diacrylates having a linear alkyl group such as 1,9-nonanediol diacrylate, 1,10-decanediol diacrylate, hydrogenated polybutadiene acrylate; tricyclodecanediol diacrylate, tricyclode Examples thereof include diacrylates having an alicyclic skeleton such as candimethanol diacrylate. However, it is not limited to these.

Polyfunctional urethane acrylate can also be used as the polyfunctional acrylate.
From the viewpoint of compatibility with the isobutylene polymer (A), a urethane acrylate having an aliphatic polymer such as polybutadiene in the skeleton is preferable.
Examples of commercially available urethane acrylate include trade name: CN9014 NS (Sartomer), trade name: BAC-45 (manufactured by Osaka Organic Chemical Co., Ltd., polybutadiene-terminated diacrylate), and the like.
Since such a polymer-based polyfunctional acrylate has an effect of lowering the plateau elastic modulus of the sheet, the acrylate polymer (B) constituting the sheet contains the polyfunctional acrylate. It can be suitably used for folding displays and impact resistant applications.

The polyfunctional acrylate is not limited to the bifunctional acrylate, and may be a polyfunctional acrylate having 3, 4, or 4 (meth) acryloyl groups. However, from the viewpoint of long-term stability of the sheet and easy availability of the acrylate, a bifunctional acrylate is preferable.

Note that the polyfunctional acrylate may be only one type or two or more types.

The polyfunctional acrylate is preferably contained in the sheet in a proportion of 0.5% by mass or more and less than 10% by mass, particularly 0.7% by mass or more or less than 9% by mass, of which 1.0% by mass or more, or 8 More preferably, it is contained in a proportion of less than 0.0% by mass. Bleed out can be reduced by setting the polyfunctional acrylate content to less than 10% by mass. On the other hand, transparency can be expressed by making content of polyfunctional acrylate into 0.5 mass% or more.

(Content ratio)
In the present sheet, the acrylate polymer (B) is preferably contained in a proportion of 5 parts by mass or more and less than 100 parts by mass with respect to 100 parts by mass of the isobutylene polymer (A).
If content of an acrylate polymer (B) is 5 mass parts or more, the cohesion force of this curable composition can be improved effectively. Moreover, if content of an acrylate polymer (B) is 100 mass parts or less, the dispersion diameter of the (B) component in this sheet | seat can be made small, express favorable transparency, and favorable transparency. It can be expressed.
From this viewpoint, the content of the acrylate polymer (B) is preferably 5 parts by mass or more and less than 100 parts by mass with respect to 100 parts by mass of the isobutylene polymer (A), and more preferably 8 parts by mass or more or 90 parts by mass. Or less, more preferably 10 parts by mass or more or 80 parts by mass or less.

<Physical properties of this sheet>
(Thickness)
The thickness of the sheet is not particularly limited. For example, it is 0.01 mm or more, more preferably 0.03 mm or more, still more preferably 0.05 mm or more. On the other hand, the upper limit is preferably 1 mm or less, more preferably 0.7 mm or less, and still more preferably 0.5 mm or less.
If the thickness is 0.01 mm or more, the handleability is good, and if the thickness is 1 mm or less, it can contribute to the thinning of the laminate.

(Dispersibility)
In this sheet, when a longitudinal section or a transverse section of the sheet is observed with a transmission electron microscope (magnification: 1000 to 5000 times), it is preferable that a lump having a maximum diameter of 1 μm or more is not observed.
The fact that no lump having a maximum diameter of 1 μm or more is observed in this way means that the isobutylene polymer (A) and the acrylate polymer (B) are highly compatible. Both water vapor barrier properties and transparency can be achieved.
“A lump with a maximum diameter of 1 μm or more is not observed” means that the sheet is dyed with ruthenium tetroxide or the like and then frozen with a cryomicrotome or the like, and the sheet is perpendicular to or parallel to the sheet surface. When cutting and preparing sections of about 80 nm in thickness, and observing the sections at 10 times at random from 1000 to 5000 times with a transmission electron microscope (TEM), This means that no lump with a maximum diameter of 1 μm or more is observed in any field of view.
As described above, when the content of the acrylate polymer (B) is smaller than that of the isobutylene polymer (A), the “lumps having a maximum diameter of 1 μm or more” are lumps composed of the acrylate polymer (B).

As described above, the fact that a lump having a maximum diameter of 1 μm or more is not observed means that the isobutylene polymer (A) and the acrylate polymer (B) are highly compatible with each other. As shown in FIGS. 2 to 5, the isobutylene polymer (A) and the acrylate polymer (B) have a co-continuous structure in which they are uniformly dispersed.

The acrylate monomer, which is the precursor of the acrylate polymer (B), is uniformly mixed with the isobutylene polymer (A), and the acrylate monomer in the mixture is polymerized. Can take.

(Tan δ)
In the present sheet, it is preferable that at least one maximum point of loss tangent (tan δ) in shearing at a frequency of 1 Hz is in a range of −30 to 30 ° C.
When the maximum point of the loss tangent (tan δ) is in the range of −30 to 30 ° C., a sheet having good adhesion and holding power can be obtained.
By selecting an acrylate having a long-chain alkyl chain having 10 or more carbon atoms as the main component of the acrylate polymer (B) and selecting the kind of isobutylene polymer and the ratio of these, the range of −30 to 30 ° C. The maximum point of loss tangent (tan δ) can be adjusted. Also, the maximum point of loss tangent can be adjusted within the range of −30 to 30 ° C. by adding a tackifier described later. However, it is not limited to such a method.

In this sheet, the maximum value of the loss tangent (tan δ) at a shear frequency of 1 Hz is within a range of −30 to 30 ° C., and the maximum value of the loss tangent at a frequency of 1 Hz is 0.5 or more. From the viewpoint of ensuring adhesion, it is more preferably 0.55 or more, and even more preferably 0.6 or more.

The loss tangent (tan δ) at 100 ° C. of the sheet is preferably 0.6 or less, and more preferably 0.5 or less. When the loss tangent (tan δ) is 0.6 or less, sufficient high-temperature holding power can be expressed.

In order to set the tan δ at 100 ° C. of the sheet to 0.6 or less as described above, a polyfunctional acrylate may be blended with the acrylate polymer and sufficiently polymerized. However, it is not limited to this method.

(Glass-transition temperature)
The sheet preferably has a single glass transition temperature (Tg).
It is rare for a multicomponent system consisting of at least the component (A) and the component (B) to have a single glass transition temperature (Tg) like a single material. However, in this sheet, since the compatibility of the component (A) and the component (B) is good, the glass transition temperature (Tg) can be made single. When the glass transition temperature is single, the transparency of the sheet can be increased.
Here, the “glass transition temperature” refers to the temperature at which the main dispersion peak of loss tangent (tan δ) appears. Therefore, when only one maximum point of loss tangent (tan δ) in shearing at a frequency of 1 Hz is observed, it can be considered that the glass transition temperature (Tg) is single.

(Total light transmittance and haze)
This sheet preferably has a total light transmittance of 85% or more, more preferably 88% or more, and further preferably 90% or more.
The sheet preferably has a haze of 2.0% or less, more preferably less than 1.0%, and particularly preferably less than 0.9%. When the haze is 2.0% or less, the sheet can be used for a display device depending on the application.

(Water vapor transmission rate)
The sheet is required to have a water vapor transmission rate as low as possible in order to suppress deterioration of the light emitting element due to water and improve the life of the display device.
From this viewpoint, the water vapor transmission rate in an environment of a temperature of 40 ° C. and a relative humidity of 90% RH in terms of 100 μm thickness (when the thickness is 100 μm) of the sheet is preferably 20 g / m ² · 24 h or less, It is more preferably 15 g / m ² · 24 h or less, and particularly preferably 10 g / m ² · 24 h or less. The lower limit is not particularly limited, but is generally 0.5 g / m ² · 24 h or more.
When the water vapor transmission rate is 20 g / m ² · 24 h or less, water vapor from the outside is prevented and suppressed from reaching the object to be sealed, and the water vapor barrier property is improved.
In order to make the water vapor transmission rate in the above range, it is preferred that the isobutylene polymer (A) is contained in an appropriate amount as the present sheet.

Here, the water vapor transmission rate can be measured according to JIS K7129B.
For example, when the thickness is A μm and the water vapor transmission rate is Bg / (m ² · day), the water vapor transmission rate in terms of 100 μm thickness is obtained by applying the formula B × A / 100. be able to.

<Method for producing this sheet>
Next, the manufacturing method of this sheet | seat is demonstrated. However, the following description is an example of a method for manufacturing the sheet, and the sheet is not limited to the one manufactured by the manufacturing method.

The present sheet can be obtained by curing an uncured sheet made of the present curable composition described later.

As a method for forming the present curable composition into an uncured sheet, a known method such as dry lamination, extrusion casting method using a T die, extrusion lamination method, calendar method, inflation method or the like can be employed. Among these, from the viewpoint of handling properties, productivity, and the like, a melt molding method such as an extrusion casting method and an extrusion lamination method is preferable.

When the melt molding not using a solvent is selected, the present curable composition for melt molding has a storage elastic modulus (G ′) at a shear frequency of 1 Hz in an uncured state of 1,000 Pa at 20 ° C. As mentioned above, it is especially preferable that it is 50,000 Pa or more and 160 Pa or less and 10,000 Pa or less.
If G ′ at 20 ° C. is in the above range, the shape can be maintained at room temperature after molding. If G ′ at 160 ° C. is in the above range, molding can be performed without entraining bubbles.

The elastic modulus (storage elastic modulus) G ′ and viscosity (loss elastic modulus) G ″ and tan δ = G ″ / G ′ at various temperatures can be measured using a strain rheometer.

The molding temperature at the time of melt molding is preferably adjusted as appropriate depending on the flow characteristics, film forming properties, and the like. In particular, the temperature is preferably 0 to 230 ° C., more preferably 80 ° C. or more, and particularly preferably 90 ° C. or more or 160 ° C. or less.
In the case of melt molding, the thickness of the sheet can be appropriately adjusted by the lip gap of the T die, the sheet take-up speed, and the like.

A cured product can be produced by irradiating and curing the present curable composition with heat and / or active energy rays. In particular, the sheet can be produced by irradiating the curable composition formed into a sheet with heat and / or active energy rays.
Here, as the active energy rays to be irradiated, ionizing radiation such as α rays, β rays, γ rays, neutron rays, electron rays, ultraviolet rays, visible rays, and the like can be mentioned. Ultraviolet rays are preferred from the viewpoint of reaction control.
Moreover, it does not specifically limit regarding irradiation energy of an active energy ray, irradiation time, an irradiation method, etc., A polymerization initiator should be activated and an acrylate component should just be polymerized.

Moreover, as another embodiment of the method for producing the present sheet, the present curable composition described later can be dissolved in an appropriate solvent, and various coating techniques can be used. However, in this embodiment, it is necessary to consider in terms of manufacturing cost such as solvent recovery.
When the coating technique is used, the present sheet can be obtained by heat curing in addition to the above active energy ray irradiation curing.

When selecting molding by a coating technique, in addition to active energy ray curing, a cured composition is easily obtained by thermal curing, and when it is a thermosetting composition, it has a decomposition temperature higher than the drying temperature of the solvent. A polymerization initiator is selected.

In the case of coating, the thickness of the sheet can be adjusted by the coating thickness and the solid content concentration of the coating solution.

In addition, it is preferable to set it as the laminated body by which a release film is laminated | stacked on the at least single side | surface of this sheet | seat from a viewpoint of blocking prevention and foreign material adhesion prevention.
As will be described later, this laminate can be cured by irradiation with heat and / or active energy rays to obtain a laminate in which a release film is laminated on at least one surface of the sheet. it can.
If necessary, embossing and various irregularities (conical, pyramidal, hemispherical, etc.) processing may be performed. Further, various surface treatments such as corona treatment, plasma treatment and primer treatment may be performed on the surface for the purpose of improving adhesion to various adherends.

<This curable composition>
Examples of the curable composition (referred to as “the present curable composition”) according to an embodiment of the present invention include a curable composition containing an isobutylene polymer (A) and an acrylate monomer.
The “curable composition” means a composition having a property capable of being cured.
As described above, the present curable composition can be formed into a sheet and cured to produce the present sheet. However, the manufacturing method of this sheet | seat is not limited to the said method.

The isobutylene polymer (A) constituting the present curable composition may be the isobutylene polymer (A) described in the present sheet.

From the same viewpoint as the present sheet, the acrylate monomer constituting the curable composition includes a monofunctional acrylate monomer (also referred to as “monofunctional acrylate”) and a polyfunctional acrylate monomer (also referred to as “polyfunctional acrylate”), respectively. It is preferable to have.

The monofunctional acrylate monomer and the polyfunctional acrylate monomer in the acrylate monomer may be the monofunctional acrylate and polyfunctional acrylate described in this sheet, respectively.

The acrylate monomer preferably contains two or more types of the monofunctional acrylate from the viewpoint of controlling the Tg after curing and suppressing crystallization.

The acrylate monomer preferably contains a monofunctional acrylate having a long alkyl chain having 10 or more carbon atoms.
When the acrylate monomer contains a monofunctional acrylate having a long alkyl chain having 10 or more carbon atoms, the entanglement between the isobutylene polymer (A) and the acrylate polymer (B) is further increased. As a result, a curable composition and a sheet having excellent adhesion and holding power can be obtained.
In addition, the present curable composition, which selectively contains a long-chain alkyl acrylate having 10 or more carbon atoms, greatly affects the higher-order structure of the present curable composition, and is a two-component curable composition. Can exhibit very good transparency.

The polyfunctional acrylate is preferably contained in the curable composition in an amount of 0.5% by mass or more and less than 10% by mass, and more preferably 0.7% by mass or more or less than 9% by mass, of which 1.0% by mass or more. Or it is more preferable to contain in less than 8.0 mass%.
Bleed out can be reduced by setting the polyfunctional acrylate content to less than 10% by mass. On the other hand, transparency can be expressed by making content of polyfunctional acrylate into 0.5 mass% or more.

It is preferable to contain 5 parts by mass or more and less than 100 parts by mass of the acrylate monomer with respect to 100 parts by mass of the isobutylene polymer (A).
If the said content of an acrylate monomer is 5 mass parts or more, the cohesion force of this curable composition can be improved effectively. Moreover, if the content of the acrylate monomer is 100 parts by mass or less, the dispersion diameter of the acrylate polymer (B) in the present curable composition can be reduced, and good transparency is exhibited and good transparency is achieved. Sex can be expressed.
From this viewpoint, the content ratio of the acrylate monomer is preferably 5 parts by mass or more and less than 100 parts by mass with respect to 100 parts by mass of the isobutylene polymer (A), and more preferably 8 parts by mass or more or 90 parts by mass or less. More preferably, it is 10 mass parts or more or 80 mass parts or less.

From the above points, a preferable curable composition is a curable composition containing 5 parts by mass or more and less than 100 parts by mass of an acrylate monomer with respect to 100 parts by mass of the isobutylene polymer (A), and as the acrylate monomer, A curable composition having a monofunctional acrylate monomer and a polyfunctional acrylate monomer, and containing the polyfunctional acrylate in the curable composition in an amount of 0.5% by mass or more and less than 10% by mass is given. be able to.

(Polymerization initiator)
The curable composition preferably contains a polymerization initiator in order to obtain curability.
The polymerization initiator is not particularly limited as long as it is a polymerization initiator that can be used for the polymerization reaction of acrylate. For example, those activated by heat and those activated by active energy rays can be used. Any of those that generate radicals to cause radical reactions and those that generate cations and anions to cause addition reactions can be used.

A preferred polymerization initiator is a photopolymerization initiator, and generally the selection of the photopolymerization initiator depends at least in part on the specific components used in the curable composition and the desired cure rate.

Examples of the photopolymerization initiator include acetophenone such as phenyl or diphenylphosphine oxide, ketone, and acridine, benzoin, benzophenone, benzoyl compound, anthraquinone, thioxanthone, and phosphine oxide.
Specifically, LUCIRIN (BASF) available as trade names DAROCUR (Ciba Specialty Chemicals), IRGACURE (Ciba Specialty Chemicals) and ethyl-2,4,6-trimethylbenzoyldiphenyl phosphinate available as LUCIRIN TPO A photoinitiator can be mentioned.

As the photopolymerization initiator, one having an excitation wavelength region of 400 nm or more can be selected and used. Specific photopolymerization initiators include, for example, α-diketones such as camphorquinone and 1-phenyl-1,2-propanedione; 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,4,6 Acylphosphine oxides such as -trimethylbenzoyl) -phenylphosphine oxide; 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1,2-methyl-1- (4-methylthiophenyl) Α-aminoalkylphenones such as -2-morpholinopropan-1-one; or bis (η5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrole) -1-yl) phenyl) titanium and other titanocene compounds and the like Can. Of these, α-diketones and acylphosphine oxides are preferable from the viewpoint of good polymerization activity and low harm to the living body, and camphorquinone and 2,4,6-trimethylbenzoyldiphenylphosphine oxide are more preferable. preferable.

On the other hand, a thermal polymerization initiator can be used in addition to the photopolymerization initiator to form a crosslinked structure.
Examples of thermal polymerization initiators include azo compounds, quinine, nitro compounds, acyl halides, hydrazones, mercapto compounds, pyrylium compounds, imidazoles, chlorotriazines, benzoins, benzoin alkyl ethers, diketones, phenones, and dilauroyl peroxide and NOF. Co. And organic peroxides such as 1,1-di (t-hexylperoxy) -3,3,5-trimethylcyclohexane available as PERHEXA TMH.

The polymerization initiator is often used at a concentration of about 0.01 to about 10% by weight, particularly about 0.01 to about 5% by weight, based on the total weight of the curable composition. A mixture of polymerization initiators may be used.

(Tackifier)
The curable composition may further contain a tackifier in order to increase the adhesiveness.
Generally, the isobutylene resin composition contains a large amount of a tackifier. However, the content of the tackifier is preferably less than 10% by mass in order to prevent problems such as a decrease in high-temperature cohesion due to the addition of the tackifier and yellowing. By setting it as this range, it can be set as the present curable composition excellent in high temperature cohesive force. The tackifier may be any compound or mixture of compounds that enhance the adhesion of the curable composition.

Examples of the tackifier include an aliphatic hydrocarbon tackifier represented by a terpene tackifier, an aromatic hydrocarbon tackifier represented by a phenol tackifier, and a rosin tackifier. Representative alicyclic hydrocarbon tackifiers, tackifiers composed of these hydrocarbon copolymers, epoxy tackifiers, polyamide tackifiers, ketone tackifiers, and hydrogens thereof An additive etc. are mentioned. Among these, from the viewpoint of compatibility, an aliphatic hydrocarbon tackifier, an aromatic hydrocarbon tackifier, an alicyclic hydrocarbon tackifier, and a tack made of these hydrocarbon copolymers An imparting agent is preferred. Particularly preferred are aliphatic hydrocarbon tackifiers.
These tackifiers can be used alone or in combination of two or more.

(Other)
The present curable composition may contain a softening agent.
The softening agent can adjust the viscosity of the composition in order to improve processability, for example.

Examples of the softening agent that can be used include petroleum hydrocarbons such as aromatic, paraffin, and naphthene, petroleum jelly, petroleum asphalt, and the like. However, it is not limited to these.
In embodiments that use a softener, a single softener or a combination of softeners can be used.
In the present curable composition, the liquid isobutylene polymer is treated as the isobutylene polymer (A).

The present curable composition may be a filler, a rust inhibitor, an acrylamide, a curing accelerator, a filler, a silane coupling agent, an ultraviolet absorber, an ultraviolet stabilizer, an antioxidant, a stabilizer, or some of them. May be added to the curable composition.
The amount of these additives is typically preferably selected so as not to adversely affect the curing of the curable composition or to adversely affect the physical properties of the curable composition.

(State and form)
The state and form of the curable composition are arbitrary. For example, it may be liquid, gel, solid, or other state.

The present curable composition may be in various forms such as a sheet shape, a rod shape, a hollow shape, and other shapes. Among these, for example, an unstretched sheet used as an adhesive sheet can be given.

When this curable composition exhibits a sheet form, the thickness is not particularly limited. For example, it is 0.01 mm or more, more preferably 0.03 mm or more, still more preferably 0.05 mm or more. On the other hand, the upper limit is preferably 1 mm or less, more preferably 0.7 mm or less, and still more preferably 0.5 mm or less.
When the thickness of the curable composition presents a sheet shape is 0.01 mm or more, the handling property is good, and when the thickness is 1 mm or less, it can contribute to the thinning of the laminate. .

(Method for producing the present curable composition)
Hereinafter, the manufacturing method of this curable composition is demonstrated. However, the following description is an example of a method for producing the present curable composition, and the present curable composition is not limited to those produced by such a production method.

The curable composition contains, for example, an isobutylene polymer (A) (also referred to as “component (A)”) and an acrylate monomer containing a monofunctional acrylate (also referred to as “component (B)”). Preparing the composition, polymerizing the component (B) using the monofunctional acrylate, curing the curable composition, and preparing the curable composition by appropriately processing as necessary. Can do. However, it is not limited to such a manufacturing method.

For example, the component (A), an acrylate monomer containing a monofunctional acrylate, a polymerization initiator, and an optional component are mixed into a kneading machine (for example, a single screw extruder, a twin screw extruder, a planetary mixer, a twin screw mixer). , A pressure kneader or the like) to prepare a curable composition that is a precursor of the present curable composition.
When mixing various raw material resins to obtain a curable composition, various additives such as silane coupling agents and antioxidants may be blended with the resin in advance and then supplied to the extruder. All materials may be supplied after being melt-mixed, or a master batch in which only the additive is previously concentrated in the resin may be prepared and supplied.

(Sheet forming method)
As a method for forming the present curable composition into a sheet, a known method such as an extrusion casting method using a T die, an extrusion laminating method, a calendar method, an inflation method, or the like can be employed. Among these, from the viewpoint of handling properties, productivity, and the like, a melt molding method such as an extrusion casting method and an extrusion lamination method is preferable.

When a melt molding not using a solvent is selected, the present curable composition for melt molding has a storage elastic modulus (G ′) at a shear frequency of 1 Hz in an uncured state of 50,000 Pa at 20 ° C. As mentioned above, it is preferable that it is 10,000 Pa or less at 160 degreeC.
If G ′ at 20 ° C. is in the above range, the shape can be maintained at room temperature after molding. If G ′ at 160 ° C. is in the above range, molding can be performed without entraining bubbles.

The molding temperature at the time of melt molding is appropriately adjusted depending on flow characteristics, film forming properties, etc., but is preferably 80 to 230 ° C., more preferably 90 to 160 ° C.
In the case of melt molding, the thickness of the sheet can be appropriately adjusted by the lip gap of the T die, the sheet take-up speed, and the like.

From the viewpoint of blocking prevention and foreign matter adhesion prevention, a laminate in which a release film is laminated on at least one surface of a sheet obtained by sheet-molding the present curable composition produced as described above is preferable.
If necessary, at least one surface of the sheet may be embossed or processed with various irregularities (such as a cone, a pyramid shape, or a hemispherical shape). Further, various surface treatments such as corona treatment, plasma treatment and primer treatment may be performed on the surface for the purpose of improving adhesion to various adherends.

The sheet can be produced by irradiating a heat and / or active energy ray on the sheet obtained by molding the curable composition produced as described above.
Here, as the active energy rays to be irradiated, ionizing radiation such as α rays, β rays, γ rays, neutron rays, electron rays, ultraviolet rays, visible rays, and the like can be mentioned. Ultraviolet rays are preferred from the viewpoint of reaction control. Moreover, it does not specifically limit regarding the irradiation energy of an active energy ray, irradiation time, an irradiation method, etc., A polymerization initiator should be activated and acrylate should just be polymerized.

Moreover, when the viscosity of the curable composition is sufficiently low as a result of adding paraffin or isoparaffin as a softening agent, a curable composition can be formed by solventless coating on the film using a die coater or a comma coater. You may get

(coating)
Moreover, as another embodiment of the method for producing the curable composition, the curable composition can be dissolved in an appropriate solvent, and various coating techniques can be used. However, in this embodiment, it is necessary to consider in terms of manufacturing cost such as solvent recovery.
When the coating technique is used, the present curable composition can also be obtained by heat curing in addition to the above active energy ray irradiation curing.

When selecting molding by a coating technique, as the cured composition, in addition to active energy ray curing, it is easy to obtain a cured composition that is thermosetting, and in the case of a thermosetting composition, from the drying temperature of the solvent A polymerization initiator having a high decomposition temperature is selected.

<This folder bull sheet>
Next, among the sheets, a sheet having a foldable property (referred to as “this foldable sheet”) will be described.

In recent years, the demand for optical adhesive (OCA) for foldable (foldable) displays is increasing. When the user of the display folds, the conventional acrylic adhesive having a glass transition temperature (Tg) near 0 ° C. causes a problem that buckling occurs at the bonding interface. This is influenced by the dynamic viscoelasticity of the adhesive in the frequency range that humans bend. Therefore, it is preferable to further lower the glass transition temperature (Tg) of the adhesive and lower the elastic modulus in the low temperature region.
From this viewpoint, the glass transition temperature (Tg) of the foldable sheet is preferably −15 ° C. or lower, and more preferably −20 ° C. or lower.
In addition, from the viewpoint of adhesive strength near normal temperature, the glass transition temperature (Tg) of the glass transition temperature (Tg) of the foldable sheet is preferably −30 ° C. or higher.

In the foldable sheet, it is preferable that at least one maximum point of loss tangent (tan δ) in shearing at a frequency of 1 Hz is in a range of −30 ° C. to −15 ° C.
Thus, when the maximum point of the loss tangent (tan δ) is in the range of −30 to −15 ° C., a sheet having good adhesion and holding power can be obtained.

As will be described later, the acrylate polymer (B) has at least two types of monofunctional acrylate components having different R in the above formula (1), so that the maximum point of loss tangent (tan δ) is −30 ° C. to −30 ° C. It becomes easy to make it the range of 15 degreeC.
In addition, the maximum point of loss tangent (tan δ) can be appropriately adjusted by selecting the kind of acrylate constituting the isobutylene polymer (A) and the acrylate polymer (B) and the composition ratio thereof.
Furthermore, the maximum point of loss tangent can be adjusted within the range of −30 to −15 ° C. by adding a tackifier described later. However, it is not limited to such a method.

In this foldable sheet, the acrylate polymer (B) is an acrylate having an acrylate unit structure having an ester part having a large number of carbon atoms (for example, 12 or more carbon atoms) from the viewpoint of compatibility with the isobutylene polymer (A). It is preferable that it is a polymer.
Therefore, the curable composition and the foldable sheet containing a monofunctional acrylate having a hydrocarbon group having 12 or more carbon atoms as the acrylate monomer of the curable composition are preferably used. The monofunctional acrylate has a characteristic that its glass transition temperature (Tg) is relatively higher than that of a general monofunctional acrylate, and can increase the Tg of the present curable composition and the present foldable sheet.

Here, the Tg of a homopolymer of a monofunctional acrylate having a hydrocarbon group having 12 or more carbon atoms on the market is specifically shown. It can be seen that the larger the carbon number, the higher the Tg, and in all cases, the Tg is higher than −15 ° C. Thus, the Tg of the homopolymer comprising the component is shown as “polymer Tg” below.
・ Lauryl acrylate (C12 straight chain, polymer Tg: -3 ° C)
・ Hexadecyl acrylate (C16 straight chain, polymer Tg: 35 ° C)
Stearyl acrylate (C18 straight chain, polymer Tg: 30 ° C.)
・ Behenyl acrylate (C22 straight chain, polymer Tg: 50 ° C.)

In addition, when the branched hydrocarbon group is introduced, the Tg of the homopolymer is lower than that of the straight chain having the same carbon number, but the Tg of the commercially available branched alkyl acrylate shown below is still -15. Over ℃.
Isostearyl acrylate (C18 branched, polymer Tg: 15 ° C. (DMA))

In addition to these monofunctional acrylates having a hydrocarbon group having 12 or more carbon atoms, polyfunctional acrylates and the like can be added to the curable composition or the foldable sheet for crosslinking.
As for the polyfunctional acrylate, from the viewpoint of compatibility with the isobutylene polymer (A), an acrylate having the following hydrocarbon group is selected, and the Tg of the resulting curable composition is further increased.
・ 1,9-nonanediol diacrylate (C9 linear bifunctional, polymer Tg: 68 ° C.)
1,10-decanediol diacrylate (C10 linear bifunctional, polymer Tg: 91 ° C.)
Tricyclodecane dimethanol diacrylate (C12 alicyclic bifunctional, polymer Tg: 190 ° C.)

It is known that the Tg of the acrylate copolymer (B) is obtained using the following FOX formula.
Formula of FOX: 1 / Tg = W1 / T1 + W2 / T2 +... Wn / Tn
In the formula, Tg is the theoretical glass transition temperature (K), W1, W2... Wn is the mass fraction of each monomer, and T1, T2... Tn are the measured glass transition temperatures (K) of each monomer. It is.

In other words, even an acrylate polymer having a relatively low polymer Tg containing isostearyl acrylate as a main structural unit is affected by the Tg of a minor component such as a polyfunctional acrylate and the interaction with an isobutylene polymer. As a result, there was a problem that the Tg of the actual curable composition did not fall below -15 ° C.
Thus, in the past, when trying to obtain a curable composition comprising an isobutylene polymer and an acrylate polymer having good compatibility, the maximum point of the loss tangent in shearing at a frequency of 1 Hz of the curable composition is − The actual situation is that the temperature exceeds 15 ° C., and it has been difficult to adjust it to −15 ° C. or lower.

In the foldable sheet, the acrylate polymer (B) contains at least two types of monofunctional acrylates, whereby the Tg of the curable composition can be dramatically reduced. This is considered to be due to a change in the interaction between the side chains composed of the long-chain hydrocarbon group of the acrylate polymer (B). As a result, a special phenomenon showing a Tg significantly lower than the Tg predicted from the FOX equation can be obtained.
In this manner, the present curable composition having at least one maximum point of loss tangent (tan δ) in shear at a frequency of 1 Hz in the range of −30 ° C. to −15 ° C. can be produced and buckled by bending. Therefore, the present foldable sheet can be realized, and a curable composition having excellent adhesion, holding power, and water vapor barrier properties can be obtained.

(Acrylate polymer (B))
The acrylate polymer (B) in the foldable sheet preferably contains a monofunctional acrylate in a proportion of 60 parts by mass or more with respect to 100 parts by mass of the acrylate polymer (B), especially 70 parts by mass or more. More preferably, it is contained in a proportion of 80 parts by mass or more.
When the monofunctional acrylate is 60 parts by mass or more, the cohesive force of the sheet is effectively improved, and the good adhesive force and holding force of the curable composition are exhibited.

In the foldable sheet, R is not particularly limited in the above formula (1) of the acrylate polymer (B). However, the R is preferably a hydrocarbon group having a restricted carbon number of 12 to 30 from the viewpoint of adhesiveness and holding power. In addition, R may contain a double bond, a triple bond, or an aromatic ring, and is preferably a hydrocarbon group that does not contain a double bond, a triple bond, or an aromatic ring from the viewpoint of long-term stability. .
Specific examples of R include, for example, a decyl group (C ₁₀ ), an undecyl group (C ₁₁ ), a dodecyl group (C ₁₂ ), a tridecyl group (C ₁₃ ), a tetradecyl group (C ₁₄ ), and a pentadecyl group (C ₁₅ ). , Hexadecyl group (C ₁₆ ), heptadecyl group (C ₁₇ ), octadecyl group (C ₁₈ ), nonadecyl group (C ₁₉ ) and the like.

Here, the acrylate polymer (B) preferably includes at least two types of the monofunctional acrylate components having Rs having different carbon numbers in the above formula (1).
By including at least two types of monofunctional acrylate components having different carbon numbers R, it becomes easy to bring the maximum point of loss tangent (tan δ) to a range of −30 ° C. to −15 ° C., which is folded as described later. It can be set as an optical adhesive for possible (foldable) displays.
The acrylate polymer (B) preferably contains two types of acrylates having different R in the formula (1), and may contain three or more types.

The acrylate polymer (B) constituting the sheet preferably contains at least one monofunctional acrylate component which is a branched alkyl group as R in the above formula (1).

By including at least one monofunctional acrylate component in which R in the above formula (1) is a branched alkyl group, the maximum point of loss tangent (tan δ) of this foldable sheet is within a range of −30 ° C. to −15 ° C. As will be described later, the optical adhesive can be folded (foldable) for a display. Further, it has an advantage that it is difficult to crystallize in a normal temperature region and transparency is easily developed.
If it is a branched alkyl group, there will be no restriction | limiting in particular. For example isodecyl group _{(C 10),} isoundecyl group _{(C 11),} isododecyl group _{(C 12),} isotridecyl group _{(C 13),} isotetradecyl group _{(C 14),} iso-pentadecyl group _{(C 15),} isohexadecyl Preferred examples include branched alkyl groups such as a group (C ₁₆ ), an isoheptadecyl group (C ₁₇ ), an isooctadecyl (isostearyl) group (C ₁₈ ), and an isonononadecyl group (C ₁₉ ).
The branched alkyl group may be either secondary or tertiary, and the position of branching and the number of branches are not particularly limited as long as they can exist chemically and stably.

Regarding the content of the monofunctional acrylate component in which R in the above formula (1) is a branched alkyl group, 30 monofunctional acrylate components in which R is a branched alkyl group with respect to 100 parts by mass of the acrylate polymer (B). The amount is preferably from 80 parts by mass to 80 parts by mass, more preferably from 35 parts by mass to 75 parts by mass. If the content is 30 parts by mass or more, it becomes easy to express the transparency of the foldable sheet. On the other hand, if it is 80 parts by mass or less, the maximum point of the loss tangent (tan δ) of the foldable sheet can be easily set in the range of −30 ° C. to −15 ° C.

Hereinafter, the acrylate monomer which is a monomer constituting the acrylate polymer (B) will be described.

A monofunctional acrylate that becomes an acrylate polymer (B) by the curing reaction is shown in the following formula (3).

As described above, the HSP of the monofunctional acrylate is preferably located at a position where the HSP distance to the isobutylene polymer (A) is 5.0 or less, more preferably 4.5 or less.
Examples of monofunctional acrylates having an HSP distance of 5.0 or less with the isobutylene polymer (A) include isostearyl acrylate, isohexadecyl acrylate, stearyl acrylate, hexadecyl acrylate, isotetradecyl acrylate, tetradecyl acrylate, Examples thereof include isododecyl acrylate, dodecyl acrylate, and isodecyl acrylate.

Moreover, it is preferable that at least one kind of R in the formula (3) is a branched alkyl group. By including at least one monofunctional acrylate component in which R is a branched alkyl group, the maximum point of loss tangent (tan δ) of the foldable sheet can be easily set in the range of −30 ° C. to −15 ° C. As will be described later, an optical adhesive for a foldable display can be obtained. Further, it has an advantage that it is difficult to crystallize in a normal temperature region and transparency is easily developed. The branched alkyl group may be secondary or tertiary, and the position of the branch and the number of branches are not particularly limited as long as they can exist chemically and stably.

With respect to the foldable sheet, 60% of the monofunctional acrylate having the unit structure of the above formula (3) is used with respect to 100 parts by weight of the acrylate in the precursor composition before curing (hereinafter referred to as “curable composition”). It is preferably contained in an amount of at least part by mass, more preferably at least 70 parts by mass, and even more preferably at least 80 parts by mass.

The polyfunctional acrylate is an acrylate having two or more acryloyloxy groups and having at least acryloyloxy groups bonded via a hydrocarbon group. As an example of the polyfunctional acrylate monomer, the structure of a bifunctional aliphatic acrylate monomer is shown in the following formula (4).

In the above formula (4), R is hydrogen (H) or a methyl group (CH ₃ ).

The content of the polyfunctional acrylate is preferably 0.5% by mass or more and less than 10% by mass with respect to the foldable sheet, more preferably 1% by mass or more or less than 9% by mass, and more preferably 2% by mass or more or 8%. More preferably, it is less than mass%.
By setting the polyfunctional acrylate content to 0.5% by mass or more, it is possible to improve the transparency and cohesive strength of the foldable sheet. Can express force.

The HSP of the polyfunctional acrylate used in the foldable sheet is preferably located at a position where the HSP distance to the isobutylene polymer (A) is 9.0 or less, and more preferably at a position of 8.0 or less.
By setting the HSP distance within the above range, troubles related to transparency and adhesiveness such as bleed out can be suppressed.

In the above formula (4), X is preferably an aliphatic hydrocarbon group or an alicyclic hydrocarbon group.

The polyfunctional acrylate used in this foldable sheet includes diacrylates having a linear alkyl group such as 1,9-nonanediol diacrylate, 1,10-decanediol diacrylate, hydrogenated polybutadiene acrylate; Examples thereof include, but are not limited to, diacrylates having an alicyclic skeleton such as decanediol diacrylate and tricyclodecane dimethanol diacrylate.

On the other hand, in the above formula (4), X may be a hydrocarbon group containing multiple bonds. Examples of such polyfunctional acrylates include trade name: BAC-45 (manufactured by Osaka Organic Chemical Co., Ltd., polybutadiene-terminated diacrylate).

Moreover, polyfunctional urethane acrylate can also be used as polyfunctional acrylate. From the viewpoint of compatibility with the component (A), a urethane acrylate having an aliphatic polymer such as polybutadiene in the skeleton is preferable. As a commercial item, brand name: CN9014 NS (Sartomer company) etc. can be mentioned.

Thus, there is no particular limitation on X in the above formula (4). From the viewpoint of transparency, X is preferably a hydrocarbon group consisting of a single bond.

The polyfunctional acrylate is not limited to a bifunctional acrylate, and a polyfunctional acrylate having 3, 4, or more than 4 (meth) acryloyl groups may be used. Among these, a bifunctional acrylate is preferable from the viewpoint of long-term stability of the sheet and ease of lowering the Tg of the curable composition.

In addition, only one type of polyfunctional acrylate may be used, or several types may be used in combination.

<Laminated body for image display device configuration, image display device>
By laminating the image display device constituting member on at least one surface of the sheet, an image display device constituting laminate can be formed, and the image display device can be configured using the image display device constituting laminate. it can.

At least one side of the sheet has a configuration in which any one or more members selected from the group consisting of a touch panel, an image display panel, a surface protection panel, a retardation film, a polarizing film, a color filter, and a flexible substrate are laminated. It can be set as the laminated body for image display apparatuses.
An image display device can be constituted by using the laminate for constituting an image display device composed of any one kind or a combination of two or more kinds.

Further, the present sheet may be an image display device provided on the display surface side and / or the non-display surface side as the image display device constituent member. For example, in a top emission type flexible OLED display, a light emitting layer is formed on a resin substrate such as polyimide, and the light emitting layer side is a display surface, but by disposing the sealing material on the non-display surface side of the resin substrate, Intrusion of water from the non-display surface side and moisture absorption of polyimide can be prevented, which can contribute to extending the life of the OLED. Further, the influence of the deformation of the display surface and external force can be suppressed.

This foldable sheet can be suitably used as a constituent member of a foldable image display device.

<Explanation of words>
In the present specification, when expressed as “X to Y” (X and Y are arbitrary numbers), “X is preferably greater than X” or “preferably Y”, with the meaning of “X to Y” unless otherwise specified. It also includes the meaning of “smaller”.
In addition, when expressed as “X or more” (X is an arbitrary number) or “Y or less” (Y is an arbitrary number), it is “preferably greater than X” or “preferably less than Y”. Includes intentions.

In the present invention, the expression “acrylate” is synonymous with acrylate and includes methacrylate unless otherwise specified.

The invention is further illustrated by the following examples. However, the examples are not intended to limit the invention in any way.

<Example 1>
First, compounds and materials used in Examples 1-1 to 1-2 and Comparative Examples 1-1 to 1-4 are shown below. Next, production methods in each Example and Comparative Example are shown, and then evaluated. A method will be described.

[Isobutylene polymer (A)]
Opanol N50 (manufactured by BASF, isobutylene polymer, Mw: 56,550,000 g / mol, (HSP δD: 15.1, δP: 0, δH: 0))
・ Tetrax 3T (manufactured by JX Energy Co., Ltd., isobutylene polymer, Mw: 49,000 g / mol, (HSP δD: 15.1, δP: 0, δH: 0))
Polybutene (iso-butene 96 mass%, n-butene 4 mass%, Mw: 3,720 Mn: 1,660 (HSP δD: 15.1, δP: 0, δH: 0))

[Acrylate (B)]
(I) Monofunctional aliphatic acrylate (b-1))
S-1800 ACL (manufactured by Shin-Nakamura Chemical Co., Ltd., isostearyl acrylate, branched alkyl having 18 carbons with one acryloyloxy group added, HSP distance from component (A): 3.74)
Blemmer CA (manufactured by NOF Corporation, cetyl acrylate, (HSP δD: 16.1, δP: 2.2, δH: 2.8, HSP distance from component A: 4.08))

(Ii) Multifunctional aliphatic acrylate (b-2))
A-DCP (manufactured by Shin-Nakamura Chemical Co., Ltd., tricyclodecane dimethanol diacrylate, HSP distance from component (A): 7.77)
A-NOD-N (manufactured by Shin-Nakamura Chemical Co., Ltd., 1.9-nonanediol diacrylate, HSP distance from component (A): 7.00)
NK ester A-DOD-N (manufactured by Shin-Nakamura Chemical Co., Ltd., 1,10-decanediol diacrylate, (HSP δD: 16.3, δP: 3.8, δH: 4.9, HSP distance from component A) : 6.64))
CN9014NS (Sartomer, hydrogenated polybutadiene bifunctional urethane acrylate)

[Tackifier]
・ Quinton CX495: Petroleum resin (antioxidant) manufactured by ZEON
Irganox 1076: manufactured by BASF, hindered phenol antioxidant (polymerization initiator)
-Omnirad TPO-G: manufactured by BASF, acylphosphine oxide photopolymerization initiator-Irgacure 184 (manufactured by BASF, 1-hydroxycyclohexyl phenyl ketone)

<Uncured sheet manufacturing method>
The isobutylene polymer (A), monofunctional aliphatic acrylate (b-1), polyfunctional aliphatic acrylate (b-2), and polymerization initiator used in the formulation shown in Table 2 were manufactured by Labo Plast Mill (manufactured by Toyo Seiki Seisakusho). ) At 110 ° C. and 60 rpm to obtain a curable composition.
Subsequently, a melted curable composition is supplied between two sheets of polyethylene terephthalate film (Mitsubishi Resin Co., Ltd., Diafoil MRF38, thickness: 38 μm) that has been subjected to a release treatment. By passing through, sandwich lamination was performed, and release films were provided on both sides, and an uncured sheet having a curable composition layer thickness of about 100 μm was obtained.
At this time, the temperature of the heating roll was 160 ° C., and the speed was 100 mm / min.

<Evaluation test of curable composition and uncured sheet>
(HSP, HSP distance (Ra))
The HSP was obtained from the chemical structure by the Y-MB method installed in HSPiP (trade name) which is HSP integrated software.
HSP distance (Ra) is, HSP the acrylate _{(B) (δD 1, δP} 1, δH 1) and then, isobutylene polymer HSP of _{(A) (δD 2, δP} 2, δH 2) when the following It was calculated by the following formula.
HSP distance (Ra) = {4 × ( δD 1 -δD 2) 2 + (δP 1 -δP 2) 2 + (δH 1 -δH 2) 2} 0.5

Table 1 shows the distances between the HSPs obtained by the Y-MB method of several components (b-1) and (b-2) and typical isobutylene polymers (A).

(Total light transmittance, haze)
Further, the total light transmittance and haze were obtained by pasting the release film on one side to the measurement hole, peeling off the other release film, and using a haze meter (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.). The total light transmittance was measured according to JIS K7361-1, and the haze was measured according to JIS K7136.

(Dynamic viscoelasticity)
The release film on both sides of the sheet obtained from the composition was peeled off, and a plurality of sheets were stacked to prepare a sheet having a thickness of about 2 mm, and punched into a circle with a diameter of 20 mm. A rheometer (manufactured by Eiko Seiki Co., Ltd., MARS), and measured under the conditions of adhesive jig: Φ20 mm parallel plate, strain: 0.1%, frequency: 1 Hz, temperature: −70 to 200 ° C., temperature increase rate: 3 ° C./min. The storage elastic modulus (G ′), loss elastic modulus (G ″), and loss tangent (tan δ) in the cured state were obtained.

<Curing sheet manufacturing method>
With the obtained uncured sheet laminated with a release film, the uncured sheet is cured by irradiating ultraviolet rays with a high-pressure mercury lamp so that the integrated light quantity at 365 nm is 2000 mJ / cm ^2, and 23 ° C. and 50% RH. The cured sheet was obtained by curing for 15 hours or longer.

<Evaluation test of cured sheet>
(Total light transmittance, haze)
Using the obtained cured sheet, measurement was performed in the same manner as the uncured sheet. The results are shown in Table 2.
(Dynamic viscoelasticity)
Using the obtained cured sheet, the storage elastic modulus (G ′), loss elastic modulus (G ″), and loss tangent (tan δ) in a cured state were obtained by measuring in the same manner as the uncured sheet.

(Water vapor barrier property)
After measuring the thickness of the obtained cured sheet, the release PET on both sides was peeled off, a PET nonwoven fabric was attached instead, and the water vapor transmission rate of 40 ° C. and 90% Rh was measured by the JIS K7129B method. evaluated.
Good: 100 μm equivalent water vapor transmission rate of 20 g or less Defective: 100 μm equivalent water vapor transmission rate over 20 g In order to compare the slightly different thicknesses, the thickness of the cured sheet is A μm, In the case of a cured sheet having a transmittance of B (g / m ² · 24 h), a value in terms of 100 μm was obtained by applying the formula A × B / 100.

The uncured sheets obtained in Examples 1-1 and 1-2 had excellent transparency with low haze and high total light transmittance. Further, cured sheets obtained by curing these uncured sheets also had excellent transparency with low haze and high total light transmittance. Furthermore, the cured sheet obtained in Example 1-3 also had low haze, high total light transmittance, and excellent transparency.
The cured sheet of Example 1-1 is excellent in impact energy absorption during high-speed deformation because the peak of loss tangent (tan δ) at a frequency of 1 Hz has a maximum value of 0.3 at −35 ° C. Also, the water vapor permeability in terms of 100 μm was as good as 20 g / m ² · 24 h or less.
The cured sheet of Example 1-2 is excellent in impact energy absorption during high-speed deformation because the peak of loss tangent (tan δ) at a shear frequency of 1 Hz has a peak value of 0.4 at −38 ° C. Also, the water vapor permeability in terms of 100 μm was as good as 20 g / m ² · 24 h or less.

The cured sheets of Comparative Examples 1-1 to 1-3 using only the monofunctional aliphatic acrylate (b-1) as the acrylate had high haze and poor transparency. This is considered to be because the polymer produced and the isobutylene polymer were phase-separated on the order of micrometers by the polymerization proceeding only with the monofunctional acrylate.
In the cured sheet of Comparative Example 1-4 using only the polyfunctional alicyclic acrylate (b-2) as the acrylate, bleeding out was confirmed in an uncured state, and haze was not preferable in the uncured sheet. Further, the transparency of the cured sheet obtained by curing this uncured sheet also deteriorated.

<Example 2>
The compounds and materials used in Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-3 are shown below, followed by the production methods in each Example and Comparative Example, and then the evaluation method Will be described.

[Isobutylene polymer (A)]
(A) -1: Opanol N50SF (manufactured by BASF, isobutylene polymer, Mw: 56,550,000 g / mol, (HSP δD: 15.1, δP: 0, δH: 0))
(A) -2: Tetrax 3T (manufactured by JXTG, isobutylene polymer, Mw: 49,000 g / mol, (HSP δD: 15.1, δP: 0, δH: 0))
(A) -3: IP solvent 2835 (Idemitsu Co., Ltd., isobutylene polymer)

[Monomer of Acrylate Polymer (B)]
(I) Monofunctional aliphatic acrylate (B) -1: S-1800 ACL (manufactured by Shin-Nakamura Chemical Co., Ltd., isostearyl acrylate, an acrylate in which one acryloyloxy group is added to a branched alkyl having 18 carbon atoms. (A) HSP distance from component: 3.74)
(B) -2: Blemmer CA (manufactured by NOF Corporation, hexadecyl acrylate, acrylate in which one acryloyloxy group is added to linear alkyl having 16 carbon atoms. HSP distance from component (A): 4.08 )

(Ii) Multifunctional acrylate (B) -3: A-DCP (manufactured by Shin-Nakamura Chemical Co., Ltd., tricyclodecane dimethanol diacrylate, HSP distance from component (A): 7.77)
(B) -4: A-NOD-N (manufactured by Shin-Nakamura Chemical Co., Ltd., 1.9-nonanediol diacrylate, HSP distance from component (A): 7.00)
(B) -5: CD595 (Sartomer, 1.10-decanediol diacrylate, HSP distance from component (A): 6.65)

[Tackifier]
(C) -1: YS resin PX800 (manufactured by Yasuhara Chemical Co., Ltd., terpene resin)

(Polymerization initiator)
(D) -1: Darocur TPO (manufactured by BASF, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide)

<Production Methods: Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-2>
Kneading the isobutylene polymer, monofunctional aliphatic acrylate, polyfunctional acrylate, tackifier, and polymerization initiator at 110 ° C. and 60 rpm with a lab plast mill (manufactured by Toyo Seiki Seisakusho) with the formulation shown in Table 3. Then, a curable composition as a precursor was obtained.
Subsequently, a molten curable composition is supplied between two sheets of polyethylene terephthalate film (Mitsubishi Chemical Corporation, Diafoil MRF38, thickness: 38 μm) that has been subjected to a release treatment, and between two heating rolls. By passing, a sandwich lamination was performed, and a release film was provided on both sides, and a sheet-like curable composition having a curable composition layer thickness of about 100 μm was obtained.
At this time, the temperature of the heating roll was 160 ° C., and the speed was 100 mm / min.

Next, the obtained sheet-like curable composition is irradiated with ultraviolet rays using a high-pressure mercury lamp so that the integrated light quantity at 365 nm is 2000 mJ / cm ² in a state where a release film is laminated, and 23 ° C. and 50% RH. The laminated body which provided the sheet | seat (sample) containing a curable composition for the intermediate | middle layer by curing for 15 hours or more.

<Evaluation test of curable composition and uncured sheet>
(HSP, HSP distance (Ra))
The HSP was obtained from the chemical structure by the Y-MB method installed in HSPiP (trade name) which is HSP integrated software.
HSP distance (Ra) is, HSP the acrylate monomer _{_{(δD 1, δP 1, δH}} 1) and then, isobutylene polymer HSP of _{(A) (δD 2, δP} 2, δH 2) when the equation below Calculated by
HSP distance (Ra) = {4 × ( δD 1 -δD 2) 2 + (δP 1 -δP 2) 2 + (δH 1 -δH 2) 2} 0.5

(Dynamic viscoelasticity)
The release film on both sides of the obtained laminate was peeled off, and a plurality of sheets (samples) were stacked to produce a sheet having a thickness of about 2 mm, and punched into a circle with a diameter of 20 mm. A rheometer (Eiko Seiki Co., Ltd.) Using a company-made MARS), measure under conditions of adhesive jig: Φ20 mm parallel plate, strain: 0.1%, frequency: 1 Hz, temperature: −50 to 150 ° C., temperature increase rate: 3 ° C./min. Thus, the storage elastic modulus (G ′), loss elastic modulus (G ″), and loss tangent (tan δ) of the sheet (sample) were obtained.
In particular, the result of tan δ is shown in FIG.

(TEM observation)
The obtained sheet (sample) was dyed with ruthenium tetroxide and freeze-cut perpendicularly to the sheet surface using a Leica microtome EM UC7 to produce a plurality of sections having a thickness of about 80 nm. 3 sections were randomly extracted from the sample, and using a Hitachi transmission electron microscope “H-7650”, the section of each section was randomly set to 10 times at an acceleration voltage of 100 kv at a magnification of 1000 to 5000 times. Observation was made to confirm the dispersion state.
At this time, each of the three slices observed was randomly observed in 10 fields of view, and if no “lumps with a maximum diameter of 1 μm” were observed in any field of view, it was judged as “none”. When “a lump having a maximum diameter of 1 μm or more” was observed in the field of view, it was judged as “present”.
The electron micrograph of the sheet (sample) obtained in Example 2-1 is shown in FIGS. 2 and 3, and the electron micrograph of the sheet (sample) obtained in Example 2-3 is shown in FIGS. Electron micrographs of the sheets (samples) obtained in 2-1 and 2-2 are shown in FIGS. 6 and 7, respectively.

(Adhesion test)
One release film of the obtained sheet (sample) was peeled off, and a 50 μm polyethylene terephthalate film (manufactured by Mitsubishi Plastics, Diafoil T100, thickness 50 μm) was bonded as a backing film to prepare a laminate.
After the laminated product was cut into a length of 150 mm and a width of 10 mm, the remaining release film was peeled off, and the exposed adhesive surface was roll-bonded to soda lime glass. The bonded product was subjected to autoclave treatment (60 ° C., gauge pressure 0.2 MPa, 20 minutes) and finished and bonded to prepare a sample for measuring adhesive strength.

The adhesion force (N / cm) with glass when the peeling force measurement sample was peeled at a peeling angle of 180 ° and a peeling speed of 60 mm / min was measured and evaluated according to the following criteria.
○: Adhesive strength of 1 N / cm or more ×: Adhesive strength of less than 1 N / cm Table 3 shows the results for each of the curable compositions obtained.

(Retention force test)
Sheets (samples) having a thickness of 100 μm prepared in Examples and Comparative Examples were cut into 40 mm × 50 mm, the release film on one side was peeled off, and a polyethylene terephthalate film for backing (Diafoil S-100, manufactured by Mitsubishi Plastics, Inc.). , A thickness of 38 μm) was back-attached with a hand roller, and then cut into a strip shape having a width of 25 mm and a length of 100 mm to obtain a test piece.
Next, the remaining release film was peeled off and attached to a SUS plate (120 mm × 50 mm × thickness 1.2 mm) with a hand roller so that the application area was 25 mm × 25 mm.

Then, after the test piece was cured for 15 minutes in an atmosphere of 40 ° C., a weight of 1 kgf was attached to the test piece in the vertical direction and left standing, and then the falling time (minutes) of the weight was measured. Evaluated by criteria.
○: those that did not fall within 30 minutes ×: those that fell within 30 minutes Table 3 shows the results for the obtained curable compositions.

(Haze)
The haze is obtained by using a haze meter (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.) in a state where glass is bonded to both sides of a sheet (sample), and the total light transmittance according to JIS K7361-1, Each haze was measured accordingly. The results for each of the obtained curable compositions are shown in Table 3.

(Dampproof)
After measuring the thickness of the obtained sheet (sample), the release PET on both sides was peeled off, a PET nonwoven fabric was attached instead, and the water vapor transmission rate at 40 ° C. and 90% Rh was measured by the JIS K7129B method. Evaluation was based on the evaluation criteria.
○: Water vapor permeability in terms of 100 μm is 20 g / m ² · 24 h or less ×: Water vapor permeability in terms of 100 μm is over 20 g / m ² · 24 h

In order to compare those with slightly different thicknesses, in the case of a cured sheet having a cured sheet thickness of A μm and a water vapor transmission rate of B (g / m ² · 24 h), the formula A × B / 100 is used. It applied and calculated | required the value of 100 micrometer conversion. The results for each of the obtained curable compositions are shown in Table 3.

As shown in FIGS. 2 to 5, the curable compositions obtained in Examples 2-1 and 2-3, ie, sheets (samples), are highly compatible with the isobutylene polymer (A) and the acrylate polymer. In addition, a lump having a maximum diameter of 1 μm or more, in other words, a dispersed phase composed of an acrylate polymer (B) having a maximum diameter of 1 μm or more was not recognized. Also in the curable composition obtained in Example 2-2, that is, the sheet (sample), a lump having a maximum diameter of 1 μm or more, that is, a dispersed phase was not observed.

The curable compositions obtained in Examples 2-1 to 2-3, that is, the sheets (samples), as can be seen from the results in Table 3 and FIG. 1, have good adhesive strength, good holding power, high It had transparency and was excellent in water vapor barrier properties.
The curable compositions or sheets (samples) obtained in Comparative Examples 2-1 and 2-2 do not have a maximum point of loss tangent in the shear at a frequency of 1 Hz in the range of −20 to 20 ° C. Therefore, it was inferior to the adhesive strength when it was made into a sheet.
Further, the curable compositions, that is, the sheets (samples) obtained in Comparative Examples 2-1 and 2-2, as shown in FIGS. 6 and 7, consist of a lump having a maximum diameter of 1 μm or more, that is, an acrylate polymer (B). A dispersed phase having a maximum diameter of 1 μm or more was observed. Therefore, it was inferior in transparency.

In Examples 2-1 to 2-3, although the content of the isobutylene polymer (A) is large relative to the acrylate polymer (B), a large tan δ peak derived from the isobutylene polymer is not observed, This is different from the system using PCHMA described in Non-Patent Document 1. This is a phenomenon observed when an acrylate polymer (B) mainly composed of a monofunctional acrylate having a long alkyl chain having 10 or more carbon atoms is used. The conventional isobutylene polymer IPN (interpenetrating network) This is a phenomenon not seen in (Structure).
It is inferred that the long-chain alkyl side chain of the component (B) exhibits viscoelastic behavior like a single material as a result of increasing the molecular entanglement with the isobutylene polymer (A).

<Example 3>
The compounds and materials used in Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-5 are shown below, followed by the production methods in each Example and Comparative Example, and then the evaluation method Will be described.

[Monomer of Acrylate Polymer (B)]
(I) Monofunctional acrylate (B) -1: S-1800 ALC (manufactured by Shin-Nakamura Chemical Co., Ltd., isostearyl acrylate, an acrylate in which one acryloyloxy group is added to a branched alkyl having 18 carbon atoms. HSP distance from component: 3.74)
(B) -2: Blemmer CA (manufactured by NOF Corporation, hexadecyl acrylate, acrylate in which one acryloyloxy group is added to linear alkyl having 16 carbon atoms. HSP distance from component (A): 4.08 )
(B) -3: Blemmer VA (manufactured by NOF Corporation, behenyl acrylate, acrylate in which one acryloyloxy unit is added to linear alkyl having 22 carbon atoms. HSP distance from component (A): 3.61)

(Ii) Multifunctional acrylate (B) -4: CD595 (Sartomer, 1.10-decanediol diacrylate, HSP distance from component (A): 6.65)
(B) -5: A-DCP (manufactured by Shin-Nakamura Chemical Co., Ltd., tricyclodecane dimethanol diacrylate, HSP distance from component (A): 7.77)
(B) -6: CN9014NS (manufactured by Sartomer, polybutadiene bifunctional urethane acrylate)

[Tackifier (C)]
(C) -1: YS resin PX800 (manufactured by Yasuhara Chemical Co., Ltd., terpene resin)

<Preparation method of sheet-like curable composition>
In the formulations shown in Tables 4 and 5, the isobutylene polymer, monofunctional acrylate, polyfunctional acrylate, tackifier, and polymerization initiator are mixed until uniform, and the precursor of the curable composition of the present invention. A curable composition was obtained.
Subsequently, a curable composition was developed between two sheets of polyethylene terephthalate film (Mitsubishi Chemical Corporation, Diafoil MRF38, thickness: 38 μm) that had been subjected to a release treatment. A sheet-like curable composition having a thickness of about 100 μm was obtained.

(Dynamic viscoelasticity)
The release film on both sides of the obtained laminate was peeled off, and a plurality of sheets (samples) were stacked to produce a sheet having a thickness of about 2 mm, and punched into a circle with a diameter of 20 mm. A rheometer (Eiko Seiki Co., Ltd.) Using a company-made MARS), measure under conditions of adhesive jig: Φ20 mm parallel plate, strain: 0.1%, frequency: 1 Hz, temperature: −70 to 150 ° C., heating rate: 3 ° C./min. Thus, the storage elastic modulus (G ′), loss elastic modulus (G ″), and loss tangent (tan δ) of the sheet (sample) were obtained.

(Bendability evaluation)
The release film on both sides of the obtained laminate is peeled off, and a 100 μm thick PET film and a 50 μm thick PET film are bonded to both surfaces, and the bonded product is autoclaved (60 ° C., gauge pressure 0.2 MPa, 20 minutes) ) Was applied and finished to prepare a sample for evaluation.
Using a sample for evaluation, DLDMMLH-FS manufactured by Yuasa System Co., Ltd., U-bending was repeated according to IEC 63715, with the PET side having a thickness of 50 μm facing inward. The test conditions were 20 ° C., frequency 1 Hz, R = 3 mm, 100,000 times, and the bendability was evaluated according to the following criteria.
○: No buckling or flow mark is observed after bending 100,000 times.
X: After buckling 100,000 times, either buckling or flow marks are observed.

The adhesion force (N / cm) with glass when the peeling force measurement sample was peeled at a peeling angle of 180 ° and a peeling speed of 60 mm / min was measured and evaluated according to the following criteria.
○: Adhesive strength of 1 N / cm or more x: Adhesive strength of less than 1 N / cm Tables 6 and 7 show the results for the obtained curable compositions.

Then, after the test piece was cured for 15 minutes in an atmosphere of 40 ° C., a weight of 1 kgf was attached to the test piece in the vertical direction and left standing, and then the falling time (minutes) of the weight was measured. Evaluated by criteria.
○: No fall within 30 minutes Δ: Over 10 minutes, fall within 30 minutes (within practical range)
X: Dropped within 10 minutes Tables 6 and 7 show the results for the obtained curable compositions.

(Haze)
The haze is obtained by applying a total light transmittance to JIS K7136 according to JIS K7361-1, using a haze meter (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.) in a state where glass is bonded to both sides of the sheet (sample). The haze was measured accordingly. The results for the obtained curable compositions are shown in Tables 6 and 7.

In order to compare those with slightly different thicknesses, in the case of a cured sheet having a cured sheet thickness of A μm and a water vapor transmission rate of B (g / m ² · 24 h), the formula A × B / 100 is used. It applied and calculated | required the value of 100 micrometer conversion. The results for the obtained curable compositions are shown in Tables 6 and 7.

<Production example using solvent>
In the formulation of Example 3-1 described in Table 4, the isobutylene polymer, monofunctional acrylate, polyfunctional acrylate, tackifier, and polymerization initiator were uniformly mixed to obtain a curable composition as a precursor. Obtained.
100 parts by mass of the obtained curable composition was transferred to a light-shielding container, and 200 parts by mass of heptane was added and dissolved to obtain a uniform coating solution.
Subsequently, the coating liquid was developed using an applicator on the release surface side of the polyethylene terephthalate film (Mitsubishi Chemical Corporation, Diafoil MRF38, thickness: 38 μm) subjected to the release treatment, and a dryer at 120 ° C. After drying for 15 minutes, another sheet of release-treated PET film was laminated using a hand roller, provided with a release film on both sides, and a curable composition layer having a thickness of about 100 μm. A curable composition was obtained.
Next, in the state where the obtained sheet-like curable composition is laminated with a release film, ultraviolet rays are irradiated using a high-pressure mercury lamp so that the integrated light amount at 365 nm is 2000 mJ / cm 2, at 23 ° C. and 50% RH. By curing for 15 hours or longer, a laminate including a sheet (sample) containing the curable composition in an intermediate layer was obtained. There were no differences in various physical properties and evaluation items even when compared with the production method using no solvent.

The sheets obtained in Examples 3-1 to 3-6 all have a maximum point of loss tangent (tan δ) in a shear of 1 Hz in the range of −30 ° C. to −15 ° C., and excellent adhesion It has strength, holding power, bendability and water vapor barrier properties.
In addition, Examples 3-1 to 3-5 were more significant in terms of holding power compared to Example 3-6. In addition, Examples 3-1 to 3-4 were more significant in terms of haze (transparency) than Example 3-5. However, even the haze of Example 3-5 is practical.
The sheets obtained in Comparative Examples 3-1 to 3-3 and Comparative Example 3-5 have a maximum point of loss tangent (tan δ) in a shear at a frequency of 1 Hz in a range of −30 ° C. to −15 ° C. No buckling was observed at the time of evaluation of the bendability.
Comparative Example 3-4 using an acrylate polymer composed only of a polyfunctional acrylate was inferior in adhesive strength and holding power, and was observed after flow at the time of evaluation of bending property.

Claims

A sheet comprising an isobutylene polymer (A) and an acrylate polymer (B),
The acrylate polymer (B) has, as a structural unit, a monofunctional acrylate unit having a unit structure represented by the following formula (1) and a polyfunctional acrylate unit,
The sheet has at least one maximum point of loss tangent (tan δ) in shear measurement at a frequency of 1 Hz in a range of −30 ° C. to 30 ° C. and a haze of 2.0% or less.

(In the formula, R represents a hydrocarbon group, and R ′ represents hydrogen (H) or a methyl group (CH 3 ), respectively).
The sheet according to claim 1, wherein the haze is less than 1.0%.
The sheet according to claim 1 or 2, wherein the acrylate polymer (B) contains 60% by mass to 90% by mass of a monofunctional acrylate unit.
4. A lump having a maximum diameter of 1 μm or more is not observed when the longitudinal or transverse section of the sheet is observed with a transmission electron microscope (magnification: 1000 to 5000 times). Sheet.
The sheet according to any one of claims 1 to 4, comprising 5 parts by mass or more and less than 100 parts by mass of the acrylate polymer (B) with respect to 100 parts by mass of the isobutylene polymer (A).
The acrylate polymer (B) contains a polyfunctional acrylate, and the content of the polyfunctional acrylate in the sheet is 0.5% by mass or more and less than 10% by mass. The sheet described in.
The sheet according to any one of claims 1 to 6, wherein at least one maximum point of loss tangent (tan δ) in shearing at a frequency of 1 Hz is in a range of -30 ° C to -15 ° C.
The sheet according to claim 7, wherein the acrylate polymer (B) has at least two types of monofunctional acrylate components.
The sheet according to claim 7 or 8, wherein the acrylate polymer (B) contains at least one monofunctional acrylate component which is a branched alkyl group as R in the above formula (1).
A curable composition containing 5 parts by mass or more and less than 100 parts by mass of an acrylate monomer with respect to 100 parts by mass of the isobutylene polymer (A),
As the acrylate monomer, each has a monofunctional acrylate monomer and a polyfunctional acrylate monomer,
A curable composition comprising the polyfunctional acrylate in the curable composition in a proportion of 0.5% by mass or more and less than 10% by mass.
The curable composition according to claim 10, comprising at least two types of the monofunctional acrylate.
An uncured sheet comprising the curable composition according to claim 10 or 11.
A sheet obtained by curing the uncured sheet according to claim 12.
A laminate in which a release film is laminated on at least one side of the sheet according to any one of claims 1 to 9 or the sheet according to claim 13.
A touch panel, an image display panel, a surface protection panel, a retardation film, a polarizing film, a color filter, and a flexible substrate on at least one side of the sheet according to any one of claims 1 to 9 or the sheet according to claim 13. The laminated body for image display apparatuses provided with the structure by which any 1 type or more in the group which consists of these is laminated | stacked.
An image display apparatus provided with the sheet according to any one of claims 1 to 9.
An image display device that can be bent, provided with the sheet according to any one of claims 7 to 9.