JP2022087156A - Adhesive for repetitive bending deice, adhesive sheet, repetitive bending laminate member and repetitive bending device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive agent for repetitive bending device and an adhesive sheet, capable of alleviating bending state of a repetitive bending device even after releasing external force when the force is applied to the repetitive bending device for repeatedly bending the device, and capable of suppressing reduction of durability, and a repetitive bending laminate member and a repetitive bending device, of which the bending state can be alleviated even after releasing external force when repeatedly bent and reduction of durability can be suppressed.

SOLUTION: There is provided an adhesive for repetitive bending device for laminating one bending member 21 and another bending member 22, constituting a device repeatedly bent, containing a polyrotaxane compound.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to adhesives and pressure-sensitive adhesives for devices that are repeatedly bent, as well as repeatedly bent laminated members and repeatedly bent devices.

In recent years, a bendable display has been proposed as a display body (display) of an electronic device, which is a kind of device. Such a flexible display is expected to have a wide range of uses, for example, for a stationary display that is curved and installed on a columnar pillar, or for a mobile display that can be bent or rolled and carried.

Examples of the type of the flexible display include an organic electroluminescence (organic EL) display, an electrophoretic display (electronic paper), and a liquid crystal display using a plastic film as a substrate.

In a flexible display as described above, it is common that one flexible member (flexible member) constituting the flexible display and another flexible member are bonded to each other by an adhesive layer of an adhesive sheet. It is considered to be the target. Here, as a conventional non-bendable adhesive sheet for a display, for example, those shown in Patent Documents 1 and 2 are known.

The flexible display may be repeatedly bent (bent) as described in Patent Document 3, instead of being curved only once. When a conventional adhesive sheet is used for a repetitive bending device for such an application, the flexible display may remain largely bent even after the external force is released, and the bent state may be fixed.

Japanese Unexamined Patent Publication No. 2015-174907 Japanese Unexamined Patent Publication No. 2016-774 Japanese Unexamined Patent Publication No. 2016-2764

In order to solve the above problems, it is conceivable to reduce the cohesive force of the adhesive and make the adhesive a soft design. However, in that case, floating or peeling occurs between the flexible member and the adhesive layer under durable conditions, which causes a decrease in durability.

The present invention has been made in view of such an actual situation, and when it is repeatedly bent by being applied to a repeatedly bending device, the bending state of the repeatedly bending device can be relaxed even after the external force is released. At the same time, the adhesive and the pressure-sensitive adhesive sheet for the repeatedly bending device that can suppress the decrease in durability, and in the case of repeated bending, the bending state can be alleviated even after the external force is released, and the decrease in durability is achieved. It is an object of the present invention to provide a repetitive bending laminated member and a repetitive bending device that can be suppressed.

In order to achieve the above object, first, the present invention is a pressure-sensitive adhesive for a repetitive bending device for adhering one flexible member constituting a device to be repeatedly bent to another flexible member. , A pressure-sensitive adhesive for a repetitive bending device, which comprises a polyrotaxane compound (Invention 1).

When the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive for a repetitive bending device according to the above invention (Invention 1) is bent and then an external force is released, the stress applied to the bent portion can be relieved by the sliding effect exerted by the polyrotaxane compound. can. As a result, even when the repeatedly bending device to which the pressure-sensitive adhesive layer is applied is bent, the pressure-sensitive adhesive layer is maintained in a flexible state even in the bent portion. Therefore, even when the repeatedly bent device to which the pressure-sensitive adhesive layer is applied is repeatedly bent, the above-mentioned effect is exhibited, so that the repeatedly bent device is greatly bent even after the external force of the repeated bending is released. Is suppressed from being fixed, and the bending state of the repeatedly bending device can be effectively alleviated. Further, since the pressure-sensitive adhesive layer can maintain a flexible state, it can easily follow the repeatedly bending device. As a result, the repeatedly bent device to which the pressure-sensitive adhesive layer is applied is effectively suppressed from floating and peeling at the interface between the repeatedly bent device and the pressure-sensitive adhesive layer even when repeatedly bent, and has excellent durability. It will be. Further, since the pressure-sensitive adhesive for the repeatedly bending device can obtain the above-mentioned physical properties by containing the polyrotaxane compound, it is not necessary to reduce the cohesive force of the pressure-sensitive adhesive and make the pressure-sensitive adhesive a soft design. Therefore, it is possible to suppress a decrease in durability due to insufficient cohesive force.

In the above invention (Invention 1), a pressure-sensitive adhesive obtained by cross-linking a pressure-sensitive adhesive composition containing a (meth) acrylic acid ester polymer (A), a cross-linking agent (B), and the polyrotaxane compound (C). (Invention 2).

The pressure-sensitive adhesive for repeated bending devices according to the above inventions (Inventions 1 and 2) preferably has a storage elastic modulus G'(-20) at −20 ° C. of 0.01 MPa or more and 1.8 MPa or less (Invention 3). ).

The pressure-sensitive adhesive for repeated bending devices according to the above inventions (Inventions 1 to 3) preferably has a storage elastic modulus G'(50) at 50 ° C. of 0.001 MPa or more and 0.5 MPa or less (Invention 4).

The pressure-sensitive adhesive for a repetitive bending device according to the above inventions (Inventions 1 to 4) preferably has a 100% modulus of 0.005 N / mm ² or more and 0.1 N / mm ² or less (Invention 5).

The pressure-sensitive adhesive for a repetitive bending device according to the above inventions (Inventions 1 to 5) preferably has a breaking elongation of 500% or more and 4000% or less in a tensile test (Invention 6).

The pressure-sensitive adhesive for a repetitive bending device according to the above inventions (Inventions 1 to 6) preferably has a breaking stress of 0.2 N / mm ² or more and 5 N / mm ² or less in a tensile test (Invention 7).

Secondly, the present invention is a pressure-sensitive adhesive sheet having an pressure-sensitive adhesive layer for adhering one flexible member constituting a device to be repeatedly bent and another flexible member, and the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer. Provided is a pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesives for repeatedly bending devices (Inventions 1 to 7) (Invention 8).

In the above invention (Invention 8), the pressure-sensitive adhesive sheet includes two release sheets, and the pressure-sensitive adhesive layer is sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets. (Invention 9).

Thirdly, the present invention has an adhesive layer for bonding one flexible member and another flexible member constituting a device to be repeatedly bent, and the one flexible member and the other flexible member to each other. Provided is a repeatedly bent laminated member comprising the above, wherein the pressure-sensitive adhesive layer is the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (Invention 8 and 9) (Invention 10).

In the above invention (Invention 10), it is preferable that at least one of the one flexible member and the other flexible member is a display element (Invention 11).

Fourth, the present invention provides a repetitive bending device including the repetitive bending laminated member (inventions 10 and 11) (invention 12).

The pressure-sensitive adhesive and the pressure-sensitive adhesive sheet for a return bending device according to the present invention can alleviate the bending state of the repeatedly bending device even after the external force is released when the pressure-sensitive adhesive and the pressure-sensitive adhesive sheet are repeatedly bent by being applied to the repeatedly bending device. It is possible to suppress a decrease in durability. Further, the repeatedly bent laminated member and the repeatedly bent device according to the present invention can alleviate the bent state of the repeatedly bent device even after the external force is released when the repeatedly bent device is repeatedly bent, and the decrease in durability is suppressed. Can be done.

It is sectional drawing of the adhesive sheet which concerns on one Embodiment of this invention. It is sectional drawing of the repeated bending laminated member which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described.
[Adhesive for repeated bending devices]
The adhesive for a repetitive bending device according to the present embodiment (hereinafter, may be simply referred to as “adhesive”) is for bonding one flexible member constituting the repetitive bending device to another flexible member. Adhesive. The repetitive bending device and the flexible member will be described later.

The pressure-sensitive adhesive according to this embodiment contains a polyrotaxane compound. The polyrotaxane compound has a mechanical bond between the cyclic molecule and the linear molecule penetrating the cyclic molecule, and the cyclic molecule can freely move on the linear molecule. Due to the sliding effect based on such a structure, when the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive is bent, the stress applied to the bent portion can be relieved. As a result, even when the repeatedly bending device to which the pressure-sensitive adhesive layer is applied is bent, the pressure-sensitive adhesive layer is maintained in a flexible state even in the bent portion. Therefore, even when the repeatedly bent device to which the pressure-sensitive adhesive layer is applied is repeatedly bent, the above-mentioned effect is exhibited, so that the repeatedly bent device is greatly bent even after the external force of the repeated bending is released. Is suppressed from being fixed, and the bending state of the repeatedly bending device can be effectively alleviated. This effect may be hereinafter referred to as "the bending state relaxation effect of the repeatedly bending device". As an example, the number of repeated bendings is 30,000 times.

Further, since the pressure-sensitive adhesive layer can maintain a flexible state, it can easily follow the repeatedly bending device. As a result, the repeatedly bent device to which the pressure-sensitive adhesive layer is applied is effectively suppressed from floating and peeling at the interface between the repeatedly bent device and the pressure-sensitive adhesive layer even when repeatedly bent, and has excellent durability. It will be. Further, since the pressure-sensitive adhesive according to the present embodiment can obtain the above-mentioned physical properties by containing the polyrotaxane compound, it is not necessary to reduce the cohesive force of the pressure-sensitive adhesive and to design the pressure-sensitive adhesive to be soft. When the cohesive force of the pressure-sensitive adhesive is reduced, the durability is generally lowered, but according to the pressure-sensitive adhesive according to the present embodiment, it is not necessary to reduce the cohesive force of the pressure-sensitive adhesive, and therefore the durability is lowered. It can be suppressed. By the above action, for example, a laminated body obtained by laminating two flexible members via a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive according to the present embodiment is subjected to high-temperature and high-humidity conditions, for example, at 85 ° C. and 85% RH. Even when left under the conditions for 72 hours, the occurrence of floating or peeling at the interface between the flexible member and the pressure-sensitive adhesive layer is suppressed.

The type of the pressure-sensitive adhesive according to the present embodiment is not particularly limited, and may be, for example, any of an acrylic pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, a polyurethane-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, and the like. Further, the pressure-sensitive adhesive may be an emulsion type, a solvent type or a solvent-free type, and may be either a crosslinked type or a non-crosslinked type. Among them, an acrylic pressure-sensitive adhesive that easily exerts the above-mentioned action and effect and has excellent adhesive physical properties, optical properties, and the like is preferable.

The pressure-sensitive adhesive according to the present embodiment is, in particular, a pressure-sensitive composition containing a (meth) acrylic acid ester polymer (A), a cross-linking agent (B), and a polyrotaxane compound (C) (hereinafter, “sticky composition”). It is preferably a pressure-sensitive adhesive obtained by cross-linking (sometimes referred to as "object P"). With such an adhesive, the effect of relaxing the bending state of the repeatedly bending device can be obtained satisfactorily, and a good adhesive force and a predetermined cohesive force can be obtained, so that the durability is excellent. In addition, in this specification, (meth) acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. In addition, the concept of "polymer" shall be included in "polymer".

(1) Component (1-1) (meth) acrylic acid ester polymer (A) of the adhesive composition P
The glass transition temperature (Tg) of the (meth) acrylic acid ester polymer (A) is preferably −40 ° C. or lower, particularly preferably −42 ° C. or lower, and further preferably −45 ° C. as an upper limit value. The following is preferable. When the upper limit of the glass transition temperature (Tg) is the above, the flexibility of the obtained pressure-sensitive adhesive can be improved. As a result, the bending state relaxing effect of the repeatedly bending device becomes more excellent. The lower limit of the glass transition temperature (Tg) of the (meth) acrylic acid ester polymer (A) is not particularly limited, but is preferably −90 ° C. or higher, particularly preferably −80 ° C. or higher, and further. Is preferably −70 ° C. or higher. The method for measuring the glass transition temperature (Tg) is as shown in the test example described later.

The (meth) acrylic acid ester polymer (A) contains a (meth) acrylic acid alkyl ester having an alkyl group having 2 to 20 carbon atoms and a reactive functional group in the molecule as a monomer unit constituting the polymer. It is preferable to contain the monomer (reactive functional group-containing monomer) having.

The (meth) acrylic acid ester polymer (A) contains a (meth) acrylic acid alkyl ester having an alkyl group having 2 to 20 carbon atoms as a monomer unit constituting the polymer, thereby achieving preferable adhesiveness. Can be expressed. The (meth) acrylic acid alkyl ester having an alkyl group having 2 to 20 carbon atoms has a glass transition temperature (Tg) of -40 ° C or lower as a homopolymer (hereinafter, may be referred to as “low Tg alkyl acrylate”). .) Is preferable. By containing such a low Tg alkyl acrylate as a constituent monomer unit, the glass transition temperature (Tg) of the (meth) acrylic acid ester polymer (A) can be easily set in the above-mentioned range, and the obtained pressure-sensitive adhesive can be easily set. Flexibility can be improved.

Examples of the low Tg alkyl acrylate include n-butyl acrylate (Tg-55 ° C.), n-octyl acrylate (Tg-65 ° C.), isooctyl acrylate (Tg-58 ° C.), and 2-ethylhexyl acrylate (Tg). -70 ° C), isononyl acrylate (Tg-58 ° C), isodecyl acrylate (Tg-60 ° C), isodecyl methacrylate (Tg-41 ° C), n-lauryl methacrylate (Tg-65 ° C), tridecyl acrylate (Tg −55 ° C.), tridecyl methacrylate (−40 ° C.) and the like are preferably mentioned. Above all, from the viewpoint of further improving the flexibility of the obtained pressure-sensitive adhesive, the homopolymer Tg of the low Tg alkyl acrylate is more preferably −45 ° C. or lower, and more preferably −50 ° C. or lower. It is particularly preferable to have. Specifically, n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferable. These may be used alone or in combination of two or more. The alkyl group in the (meth) acrylic acid alkyl ester having 2 to 20 carbon atoms of the alkyl group means a linear, branched or cyclic alkyl group.

The (meth) acrylic acid ester polymer (A) preferably contains a low Tg alkyl acrylate as a lower limit value of 50% by mass or more, and particularly 60% by mass or more, as a monomer unit constituting the polymer. Is preferable, and more preferably 70% by mass or more is contained. By containing 50% by mass or more of the low Tg alkyl acrylate, the glass transition temperature (Tg) of the (meth) acrylic acid ester polymer (A) can be easily set within the above range.

Further, the (meth) acrylic acid ester polymer (A) preferably contains the above low Tg alkyl acrylate as a monomer unit constituting the polymer in an upper limit of 99% by mass or less, and particularly preferably in an amount of 97% by mass or less. It is preferable that the content is 95% by mass or less. By containing 99% by mass or less of the low Tg alkyl acrylate, a suitable amount of other monomer components (particularly, a monomer containing a reactive functional group) can be introduced into the (meth) acrylic acid ester polymer (A). ..

Further, the (meth) acrylic acid ester polymer (A) may be a monomer having a glass transition temperature (Tg) of more than 0 ° C. as a homopolymer (hereinafter referred to as “hard monomer”” as a monomer unit constituting the polymer. There is also preferable to use together. As a result, the glass transition temperature (Tg) can be easily set in the above-mentioned range, and a desired cohesive force can be imparted to the obtained pressure-sensitive adhesive. The hard monomer also includes a reactive functional group-containing monomer described later.

Examples of the hard monomer include methyl acrylate (Tg10 ° C.), methyl methacrylate (Tg105 ° C.), ethyl methacrylate (Tg65 ° C.), n-butyl methacrylate (Tg20 ° C.), and isobutyl methacrylate (Tg48 ° C.). T-butyl methacrylate (Tg107 ° C), n-stearyl acrylate (Tg30 ° C), n-stearyl methacrylate (Tg38 ° C), cyclohexylacrylic acid (Tg15 ° C), cyclohexyl methacrylate (Tg66 ° C), phenoxyethyl acrylate (Tg 5 ° C), phenoxyethyl methacrylate (Tg 54 ° C), benzyl methacrylate (Tg 54 ° C), isobornyl acrylate (Tg 94 ° C), isobornyl methacrylate (Tg 180 ° C), acryloylmorpholin (Tg 145 ° C), adamantyl acrylate (Tg 115 ° C). ℃), acrylic monomer such as adamantyl methacrylate (Tg141 ℃), acrylic acid (Tg103 ℃), dimethylacrylamide (Tg89 ℃), acrylamide (Tg165 ℃), vinyl acetate (Tg32 ℃), styrene (Tg80 ℃) and the like. Can be mentioned. These may be used alone or in combination of two or more. Among the above-mentioned hard monomers, from the viewpoint of facilitating the setting of the glass transition temperature (Tg) of the (meth) acrylic acid ester polymer (A) in the above-mentioned range, and from the viewpoint of imparting a desired cohesive force to the obtained pressure-sensitive adhesive. , Isobornyl acrylate, acryloyl morpholine and at least one of acrylic acid are particularly preferred.

When the (meth) acrylic acid ester polymer (A) contains the above-mentioned hard monomer as a monomer unit constituting the polymer, the hard monomer is contained in an amount of 1% by mass from the viewpoint of improving the cohesive force of the obtained pressure-sensitive adhesive. It is preferably contained in an amount of 2% by mass or more, and more preferably 3% by mass or more. Further, the (meth) acrylic acid ester polymer (A) preferably contains the hard monomer in an amount of 30% by mass or less, and particularly preferably 20% by mass or less, as a monomer unit constituting the polymer. Further, it is preferably contained in an amount of 15% by mass or less.

The (meth) acrylic acid ester polymer (A) contains a reactive functional group-containing monomer as a monomer unit constituting the polymer, and thus via the reactive functional group derived from the reactive functional group-containing monomer. , Will react with the cross-linking agent (B) described later, thereby forming a cross-linked structure (three-dimensional network structure), and a pressure-sensitive adhesive having a desired cohesive force can be obtained.

The reactive functional group-containing monomer contained in the (meth) acrylic acid ester polymer (A) as a monomer unit constituting the polymer includes a monomer having a hydroxyl group in the molecule (monomer containing a hydroxyl group) and carboxy in the molecule. Preferred examples thereof include a monomer having a group (monomer containing a carboxy group) and a monomer having an amino group in the molecule (monomer containing an amino group). These reactive functional group-containing monomers may be used alone or in combination of two or more.

Among the above-mentioned reactive functional group-containing monomers, the (meth) acrylic acid ester polymer (A) contains a hydroxyl group from the viewpoint of lowering the glass transition temperature (Tg) and imparting desired flexibility to the obtained pressure-sensitive adhesive. It is preferable to use a monomer. Further, among the above-mentioned reactive functional group-containing monomers, it is preferable to use a carboxy group-containing monomer from the viewpoint of improving the cohesive force of the obtained pressure-sensitive adhesive.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and (meth). ) Acrylic acid (meth) Acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylic acid can be mentioned. Above all, from the viewpoint of the glass transition temperature (Tg), the reactivity of the obtained (meth) acrylic acid ester polymer (A) with the cross-linking agent (B) of the hydroxyl group, and the copolymerizability with other monomers. It is preferably at least one of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate. These may be used alone or in combination of two or more.

Examples of the carboxy group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Of these, acrylic acid is preferable from the viewpoint of the reactivity of the carboxy group in the obtained (meth) acrylic acid ester polymer (A) with the cross-linking agent (B) and the copolymerizability with other monomers. These may be used alone or in combination of two or more.

The (meth) acrylic acid ester polymer (A) preferably contains a reactive functional group-containing monomer in an amount of 1% by mass or more as a lower limit value, particularly 3% by mass or more, as a monomer unit constituting the polymer. It is preferable that the content is 5% by mass or more. Further, the (meth) acrylic acid ester polymer (A) preferably contains a reactive functional group-containing monomer as an upper limit value of 40% by mass or less, preferably 30% by mass or less, as a monomer unit constituting the polymer. It is more preferably contained, particularly preferably 20% by mass or less, and further preferably 15% by mass or less. When the (meth) acrylic acid ester polymer (A) contains the reactive functional group-containing monomer in the above amount as the monomer unit, the cohesive force of the obtained pressure-sensitive adhesive becomes appropriate, and the durability of the obtained pressure-sensitive adhesive layer becomes appropriate. And the effect of alleviating the bending state of the repetitive bending device is achieved at a high level.

It is also preferable that the (meth) acrylic acid ester polymer (A) does not contain a carboxy group-containing monomer, particularly acrylic acid which is also a hard monomer, as a monomer unit constituting the polymer. Since the carboxy group is an acid component, a transparent conductive film such as tin-doped indium oxide (ITO), a metal film, etc. Even when a metal mesh or the like is present, it is possible to suppress those defects (corrosion, change in resistance value, etc.) due to acid.

If desired, the (meth) acrylic acid ester polymer (A) may contain another monomer as a monomer unit constituting the polymer. As the other monomer, a monomer containing no reactive functional group is preferable so as not to interfere with the action of the reactive functional group-containing monomer. Examples of such other monomers include (meth) acrylic acid alkoxyalkyl esters such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, as well as a glass transition temperature (Tg) of -40 as a homopolymer. Examples thereof include monomers having a temperature higher than ° C and a temperature of 0 ° C or lower (hereinafter, may be referred to as “medium Tg alkyl acrylate”). Examples of the medium Tg alkyl acrylate include ethyl acrylate (Tg-20 ° C.), isobutyl acrylate (Tg-26 ° C.), 2-ethylhexyl methacrylate (Tg-10 ° C.), and n-lauryl acrylate (Tg-23 ° C.). ° C.), isostearyl acrylate (Tg-18 ° C.) and the like. These may be used alone or in combination of two or more.

The polymerization mode of the (meth) acrylic acid ester polymer (A) may be a random copolymer or a block copolymer.

The lower limit of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 200,000 or more, particularly preferably 400,000 or more, and further preferably 600,000 or more. When the lower limit of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is the above, the durability of the pressure-sensitive adhesive becomes more excellent. The weight average molecular weight in the present specification is a value in terms of standard polystyrene measured by a gel permeation chromatography (GPC) method.

Further, the upper limit of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 2 million or less, particularly preferably 1.5 million or less, and further preferably 900,000 or less. preferable. When the upper limit of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is as described above, the flexibility of the obtained pressure-sensitive adhesive becomes more excellent.

In the adhesive composition P, the (meth) acrylic acid ester polymer (A) may be used alone or in combination of two or more.

(1-2) Crosslinking agent (B)
The cross-linking agent (B) cross-links the (meth) acrylic acid ester polymer (A) with the heating of the adhesive composition P containing the cross-linking agent (B) as a trigger to form a three-dimensional network structure. .. As a result, the cohesive force of the obtained pressure-sensitive adhesive is improved, and the obtained pressure-sensitive adhesive layer becomes excellent in durability.

The cross-linking agent (B) may be any as long as it reacts with the reactive group of the (meth) acrylic acid ester polymer (A), and for example, an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, and an amine-based cross-linking agent. , Melamine-based cross-linking agent, aziridine-based cross-linking agent, hydrazine-based cross-linking agent, aldehyde-based cross-linking agent, oxazoline-based cross-linking agent, metal alkoxide-based cross-linking agent, metal chelate-based cross-linking agent, metal salt-based cross-linking agent, ammonium salt-based cross-linking agent, etc. Can be mentioned. Among the above, it is preferable to use an isocyanate-based cross-linking agent having excellent reactivity with the reactive functional group-containing monomer. The cross-linking agent (B) may be used alone or in combination of two or more.

The isocyanate-based cross-linking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanates, and alicyclic polyisocyanates such as hydrogenated diphenylmethane diisocyanate. , And their biurets, isocyanates, and adducts, which are reactants with low molecular weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Of these, trimethylolpropane-modified aromatic polyisocyanates, particularly trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate, are preferable from the viewpoint of reactivity with hydroxyl groups.

The content of the cross-linking agent (B) in the adhesive composition P is preferably 0.01 part by mass or more, preferably 0.1 part by mass with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). It is more preferably parts by mass or more, particularly preferably 0.5 parts by mass or more, and further preferably 1 part by mass or more. The content is preferably 10 parts by mass or less, particularly preferably 6 parts by mass or less, and further preferably 4 parts by mass or less. When the content of the cross-linking agent (B) is within the above range, the cohesive force of the obtained adhesive becomes appropriate, and the durability of the obtained adhesive layer and the effect of alleviating the bending state of the repeatedly bent device are compatible. Achieved at a high level.

(1-3) Polyrotaxane compound (C)
The polyrotaxane compound (C) is a compound in which a linear molecule penetrates through the openings of at least two cyclic molecules and has block groups at both ends of the linear molecule. In this polyrotaxane compound (C), the cyclic molecule can freely move on the linear molecule, but the cyclic molecule has a structure in which the cyclic molecule cannot escape from the linear molecule due to the block group. That is, the linear molecule and the cyclic molecule maintain their morphology while exhibiting a sliding effect by a so-called mechanical bond rather than a chemical bond such as a covalent bond. When the pressure-sensitive adhesive (tacky composition P) according to the present embodiment contains the polyrotaxane compound (C) having such a mechanical bond, the pressure-sensitive adhesive layer obtained is repeatedly formed by a repeatedly bending device which is an adherend. Even when it is bent, it is easy to release stress and it is easy to follow the repeated bending device. As a result, when the pressure-sensitive adhesive according to the present embodiment is repeatedly applied to the bending device and repeatedly bent, the bending state of the repeatedly bending device can be relaxed even after the external force is released. In particular, when the cyclic molecule of the polyrotaxane compound (C) is a cyclic oligosaccharide having a hydroxyl group as a reactive group, when the isocyanate-based cross-linking agent is used as the cross-linking agent (B), the isocyanate-based cross-linking agent is used. The (meth) acrylic acid ester polymer (A) and the polyrotaxane compound (C) (cyclic molecule) are crosslinked via the crosslink, and the cyclic molecule freely moves on the linear molecule in the polyrotaxane compound (C). As a result, the flexibility as a crosslinked body is significantly improved. As a result, the effect of relaxing the bending state of the repeatedly bending device becomes more excellent.

The polyrotaxane compound (C) in the present embodiment preferably has a cyclic oligosaccharide as a cyclic molecule. By using a cyclic oligosaccharide as the cyclic molecule of the polyrotaxane compound (C), it is possible to select an appropriate ring diameter, whereby the effect of the movement of the cyclic molecule on the linear molecule is likely to be exhibited. Further, when the cyclic oligosaccharide has a hydroxyl group as a reactive group, the reaction with the isocyanate-based cross-linking agent is easy. Furthermore, it is easy to introduce various substituents and the like, whereby the compatibility between the polyrotaxane compound (C) and other components can be adjusted by the polyrotaxane compound (C). Furthermore, cyclic oligosaccharides have the advantage of being easily available. In addition, in this specification, "cyclic" of "cyclic molecule" or "cyclic oligosaccharide" means substantially "cyclic". That is, the cyclic molecule does not have to be completely ring-closed, and may have a helical structure, for example, as long as it can move on the linear molecule.

Examples of the cyclic oligosaccharide include cyclodextrins such as α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin, and α-cyclodextrin is particularly preferable. Two or more kinds of cyclic molecules of the polyrotaxane compound (C) may be mixed in the polyrotaxane compound (C) or in the pressure-sensitive adhesive (tacky composition P).

When the cyclic molecule (cyclic oligosaccharide) of the polyrotaxane compound (C) has a hydroxyl group as a reactive group, the hydroxyl group may be the hydroxyl group originally possessed by the cyclic oligosaccharide (meaning the state before modification). However, it may be a hydroxyl group introduced as a substituent into the cyclic oligosaccharide.

The hydroxyl value of the cyclic molecule is preferably 10 mgKOH / g or more, more preferably 30 mgKOH / g or more, and particularly preferably 50 mgKOH / g or more as the lower limit. When the lower limit of the hydroxyl value is the above, the polyrotaxane compound (C) can sufficiently react with the isocyanate-based cross-linking agent. The hydroxyl value of the cyclic molecule is preferably 1000 mgKOH / g or less, more preferably 200 mgKOH / g or less, and particularly preferably 100 mgKOH / g or less. When the upper limit of the hydroxyl value exceeds the above value, a large number of crosslinks occur in the same cyclic molecule, so that the cyclic molecule itself becomes a crosslink point, and the effect of the crosslink point of the polyrotaxane compound (C) as a whole can be exhibited. As a result, sufficient stress relaxation property of the pressure-sensitive adhesive layer may not be ensured.

The linear molecule of the polyrotaxane compound (C) is a molecule or substance that is encapsulated in a cyclic molecule and can be integrated by a mechanical bond rather than a chemical bond such as a covalent bond, and is linear. If so, it is not particularly limited. In addition, in this specification, a "straight line" of a "linear molecule" means a substantially "straight line". That is, the linear molecule may have a branched chain as long as the cyclic molecule can move on the linear molecule.

As the linear molecule of the polyrotaxane compound (C), for example, polyethylene glycol, polypropylene glycol, polyisobutylene, polyisobutylene, polybutadiene, polytetrahydrofuran, polyacrylic acid ester, polydimethylsiloxane, polyethylene, polypropylene and the like are preferable. Two or more kinds of linear molecules may be mixed in the adhesive composition P.

The number average molecular weight of the linear molecule of the polyrotaxane compound (C) is preferably 3,000 or more as a lower limit value, particularly preferably 10,000 or more, and further preferably 20,000 or more. preferable. When the lower limit of the number average molecular weight is equal to or higher than the above, the amount of movement of the cyclic molecule on the linear molecule is secured, and the stress relaxation property of the pressure-sensitive adhesive can be sufficiently obtained. The number average molecular weight of the linear molecule of the polyrotaxane compound (C) is preferably 300,000 or less as an upper limit value, particularly preferably 200,000 or less, and further preferably 100,000 or less. Is preferable. When the upper limit of the number average molecular weight is not more than the above, the solubility of the polyrotaxane compound (C) in a solvent and the compatibility with the (meth) acrylic acid ester polymer (A) are improved.

The blocking group of the polyrotaxane compound (C) is not particularly limited as long as it is a group capable of retaining the skewered form of the cyclic molecule by the linear molecule. Examples of such a group include a bulky group and an ionic group.

Specifically, the blocking group of the polyrotaxane compound (C) is a dinitrophenyl group, a cyclodextrin group, an adamantan group, a trityl group group, a fluorescein group, a pyrene group, an anthracene group, or the like, or a number average molecular weight of 1,000. The main chain or side chain of a polymer of up to 1,000,000 is preferable, and two or more of these blocking groups may be mixed in the polyrotaxane compound (C) or in the adhesive composition P.

The polyrotaxane compound (C) described above can be obtained by a conventionally known method (for example, the method described in JP-A-2005-154675).

The content of the polyrotaxane compound (C) in the adhesive composition P according to the present embodiment is 0.1 part by mass or more as a lower limit with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). It is preferably 1 part by mass or more, and more preferably 5 parts by mass or more. When the lower limit of the content of the polyrotaxane compound (C) is the above, the bending state relaxing effect of the repetitive bending device becomes more excellent. The content of the polyrotaxane compound (C) is preferably 50 parts by mass or less, more preferably 25 parts by mass or less, and particularly preferably 10 parts by mass or less as an upper limit value. When the upper limit of the content of the polyrotaxane compound (C) is the above, the total light transmittance of the pressure-sensitive adhesive layer can be maintained high, which is suitable for optical applications.

(1-4) Various Additives Various additives usually used for acrylic pressure-sensitive adhesives, such as silane coupling agents, ultraviolet absorbers, antistatic agents, and tackifiers, are added to the pressure-sensitive adhesive composition P, if desired. Agents, antioxidants, light stabilizers, softeners, fillers, refractive index adjusters and the like can be added. The polymerization solvent and the diluting solvent described later are not included in the additives constituting the adhesive composition P.

The adhesive composition P preferably contains the above-mentioned silane coupling agent. As a result, in the obtained pressure-sensitive adhesive layer, the adhesion to the flexible member, which is an adherend, is improved, and the durability is further improved.

The silane coupling agent is an organosilicon compound having at least one alkoxysilyl group in the molecule, which has good compatibility with the (meth) acrylic acid ester polymer (A) and has light transmittance. preferable.

Examples of such silane coupling agents include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacrypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 2-(. 3,4-Epoxycyclohexyl) Silicon compounds having an epoxy structure such as ethyltrimethoxysilane, mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane , Amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-Chloropropyltrimethoxysilane, 3-Isoxypropyltriethoxysilane, or at least one of these, and alkyl group-containing silicon compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. Examples thereof include the condensate of. These may be used individually by 1 type and may be used in combination of 2 or more type.

The content of the silane coupling agent in the adhesive composition P is preferably 0.01 part by mass or more, particularly 0.05 part by mass with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). It is preferably 1 part by mass or more, and more preferably 0.1 part by mass or more. The content is preferably 1 part by mass or less, particularly preferably 0.5 part by mass or less, and further preferably 0.3 part by mass or less.

(2) Production of Adhesive Composition P The adhesive composition P produces a (meth) acrylic acid ester polymer (A), and the obtained (meth) acrylic acid ester polymer (A) and a cross-linking agent. It can be produced by mixing (B) with the polyrotaxane compound (C) and, if desired, adding an additive.

The (meth) acrylic acid ester polymer (A) can be produced by polymerizing a mixture of monomers constituting the polymer by an ordinary radical polymerization method. The polymerization of the (meth) acrylic acid ester polymer (A) is preferably carried out by a solution polymerization method using a polymerization initiator, if desired. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone and the like, and two or more of them may be used in combination.

Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more of them may be used in combination. Examples of the azo compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane1-carbonitrile), and 2, , 2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis (2-methylpropionate) 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (2-hydroxymethylpropionitrile), 2,2'-azobis [2- (2-imidazolin-2-yl)) Propane] and the like.

Examples of the organic peroxide include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples thereof include dicarbonate, t-butylperoxyneodecanoate, t-butylperoxyvivarate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

In the above polymerization step, the weight average molecular weight of the obtained polymer can be adjusted by adding a chain transfer agent such as 2-mercaptoethanol.

Once the (meth) acrylic acid ester polymer (A) is obtained, the solution of the (meth) acrylic acid ester polymer (A) is mixed with a cross-linking agent (B), a polyrotaxane compound (C), and optionally additives and dilutions. By adding the solvent and mixing well, the adhesive composition P (coating solution) diluted with the solvent is obtained.

If any of the above components is in the form of a solid, or if precipitation occurs when the component is mixed with another component in an undiluted state, the component is used alone as a diluting solvent in advance. It may be dissolved or diluted and then mixed with other ingredients.

Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methylene chloride and ethylene chloride, methanol, ethanol, propanol and butanol. Alcohols such as 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone and cyclohexanone, esters such as ethyl acetate and butyl acetate, and cellosolve solvents such as ethyl cellosolve are used.

The concentration and viscosity of the coating solution prepared in this manner may be any range as long as it can be coated, and may be appropriately selected depending on the situation. For example, the adhesive composition P is diluted to a concentration of 10 to 60% by mass. It should be noted that the addition of a diluting solvent or the like is not a necessary condition when obtaining the coating solution, and the diluting solvent may not be added as long as the adhesive composition P has a viscosity that allows coating. In this case, the adhesive composition P becomes a coating solution using the polymerization solvent of the (meth) acrylic acid ester polymer (A) as it is as a diluting solvent.

(3) Production of Adhesive The adhesive according to the present embodiment is preferably obtained by cross-linking the adhesive composition P. Crosslinking of the adhesive composition P can usually be carried out by heat treatment. It should be noted that this heat treatment can also be used as a drying treatment for volatilizing the diluting solvent or the like from the coating film of the adhesive composition P applied to the desired object.

The heating temperature of the heat treatment is preferably 50 to 150 ° C, particularly preferably 70 to 120 ° C. The heating time is preferably 10 seconds to 10 minutes, and particularly preferably 50 seconds to 2 minutes.

After the heat treatment, if necessary, a curing period of about 1 to 2 weeks may be provided at room temperature (for example, 23 ° C., 50% RH). If this curing period is required, the adhesive is formed after the curing period has elapsed, and if the curing period is not required, the adhesive is formed after the heat treatment is completed.

By the above heat treatment (and curing), the (meth) acrylic acid ester polymer (A) is sufficiently cross-linked via the cross-linking agent (B) to form a cross-linked structure, and a pressure-sensitive adhesive is obtained. Such a pressure-sensitive adhesive has a predetermined cohesive force, and the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive has excellent durability.

(4) Physical characteristics of adhesive (4-1) Storage elastic modulus G'(-20)
The storage elastic modulus G'(may be referred to as "storage elastic modulus G'(-20)" in the present specification) of the pressure-sensitive adhesive according to the present embodiment at −20 ° C. is 1.8 MPa as an upper limit value. It is preferably less than or equal to, particularly preferably 0.8 MPa or less, and further preferably 0.5 MPa or less. When the upper limit of the storage elastic modulus G'(-20) is the above, the pressure-sensitive adhesive becomes a soft material having a very high stress relaxation property. As a result, the bending state relaxing effect of the repeatedly bending device becomes more excellent. The lower limit of the storage elastic modulus G'(-20) is not particularly limited, but is preferably 0.01 MPa or more, particularly preferably 0.05 MPa or more, and further preferably 0.1 MPa or more. preferable.

(4-2) Storage elastic modulus G'(50)
The storage elastic modulus G'at 50 ° C. of the pressure-sensitive adhesive according to the present embodiment (may be referred to as "storage elastic modulus G'(50)" in the present specification) is 0.001 MPa or more as a lower limit. It is preferably 0.01 MPa or more, and more preferably 0.02 MPa or more. When the lower limit of the storage elastic modulus G'(50) is the above, the pressure-sensitive adhesive exhibits a predetermined cohesive force, and thus has better durability. The upper limit of the storage elastic modulus G'(50) is not particularly limited, but is preferably 0.5 MPa or less, particularly preferably 0.1 MPa or less, and further preferably 0.05 MPa or less. ..

(4-3) Storage elastic modulus G'(23)
The storage elastic modulus G'(may be referred to as" storage elastic modulus G'(23) "in the present specification) of the pressure-sensitive adhesive according to the present embodiment at 23 ° C. is 0.01 MPa or more as a lower limit. It is preferably 0.02 MPa or more, and more preferably 0.03 MPa or more. When the lower limit of the storage elastic modulus G'(23) is the above, it is possible to prevent the adhesive from seeping out due to bending at room temperature. The upper limit of the storage elastic modulus G'(23) is preferably 0.8 MPa or less, particularly preferably 0.2 MPa or less, and further preferably 0.1 MPa or less. When the upper limit of the storage elastic modulus G'(23) is the above, the pressure-sensitive adhesive can exhibit excellent bending resistance at room temperature.

The storage elastic moduli G'(-20), G'(50) and G'(23) are values measured by a method based on JIS K7244-6, and the specific measurement method is a test described later. As shown in the example.

(4-4) 100% Modulus The 100% modulus of the pressure-sensitive adhesive according to the present embodiment is preferably 0.005 N / mm ² or more, and particularly 0.01 N / mm ² or more, as a lower limit value. It is preferable, more preferably 0.015 N / mm ² or more. When the lower limit of 100% modulus is the above, the durability of the repetitive bending device becomes more excellent. The upper limit of the 100% modulus is preferably 0.1 N / mm ² or less, particularly preferably 0.07 N / mm ² or less, and further preferably 0.05 N / mm ² or less. .. When the upper limit of the 100% modulus is the above, the bending state relaxing effect of the repetitive bending device becomes more excellent. Since the pressure-sensitive adhesive according to the present embodiment contains a polyrotaxane compound, it is possible to achieve 100% modulus in the above range. The method for measuring 100% modulus in the present specification is as shown in a test example described later.

(4-5) Breaking elongation The breaking elongation of the pressure-sensitive adhesive according to the present embodiment in the tensile test is preferably 500% or more, particularly preferably 800% or more, and further 1000. % Or more is preferable. When the lower limit value of the breaking elongation is the above, the bending state relaxing effect of the repeatedly bending device becomes more excellent. In addition, it is possible to suppress the occurrence of problems such as the pressure-sensitive adhesive being coagulated and broken when repeatedly bent. Since the pressure-sensitive adhesive according to the present embodiment contains a polyrotaxane compound, it is possible to achieve the above-mentioned large elongation at break. The upper limit of the elongation at break is not particularly limited, but is preferably 4000% or less, particularly preferably 3500% or less, and further preferably 3000% or less. The method for measuring the elongation at break in the present specification is as shown in a test example described later.

(4-6) Breaking stress The breaking stress of the pressure-sensitive adhesive according to the present embodiment in the tensile test is preferably 0.2 N / mm ² or more, and particularly 0.3 N / mm ² or more as the lower limit. Is preferable, and more preferably 0.4 N / mm ² or more. When the lower limit of the breaking stress is the above, it is possible to suppress the occurrence of defects such as cohesive failure of the adhesive when repeatedly bending, and the durability of the repeatedly bending device is more excellent. Become. The upper limit of the breaking stress is not particularly limited, but is preferably 5 N / mm ² or less, particularly preferably 3 N / mm ² or less, and further preferably 2 N / mm ² or less. Since the pressure-sensitive adhesive according to the present embodiment contains a polyrotaxane compound, it is possible to achieve a breaking stress in the above range. The method for measuring the breaking stress in the present specification is as shown in a test example described later.

(4-7) Gel fraction The pressure-sensitive adhesive according to the present embodiment preferably has a gel fraction of 35% or more, particularly preferably 40% or more, and further preferably 45% or more. .. The gel fraction is preferably 90% or less, particularly preferably 76% or less, and further preferably 71% or less. The pressure-sensitive adhesive according to the present embodiment has a gel fraction of 45% or more, so that the adhesive has further excellent durability while maintaining stress relaxation property. The method for measuring the gel fraction is as shown in the test example described later.

[Adhesive sheet]
The pressure-sensitive adhesive sheet according to the present embodiment has a pressure-sensitive adhesive layer for adhering one flexible member constituting the repeatedly bending device to another flexible member, and the pressure-sensitive adhesive layer is the above-mentioned pressure-sensitive adhesive. It consists of.

FIG. 1 shows a specific configuration as an example of the pressure-sensitive adhesive sheet according to the present embodiment.
As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 according to the embodiment is in contact with the two release sheets 12a and 12b and the release surfaces of the two release sheets 12a and 12b. , 12b and the pressure-sensitive adhesive layer 11. The peeling surface of the release sheet in the present specification refers to a surface having peelability in the release sheet, and includes both a surface subjected to peeling treatment and a surface exhibiting peelability even without peeling treatment. ..

(1) Components (1-1) Adhesive Layer The adhesive layer 11 is composed of the adhesive according to the above-described embodiment, and is preferably composed of a pressure-sensitive adhesive obtained by cross-linking the adhesive composition P. ..

The thickness of the pressure-sensitive adhesive layer 11 (value measured according to JIS K7130) in the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably 5 μm or more, particularly preferably 10 μm or more, and further preferably 10 μm or more as a lower limit value. It is preferably 20 μm or more. The thickness of the pressure-sensitive adhesive layer 11 is preferably 300 μm or less as an upper limit value, particularly preferably 200 μm or less, and further preferably 100 μm or less. When the thickness of the pressure-sensitive adhesive layer 11 is within the above range, it is easy to exert a desired adhesive force, and the effect of relaxing the bending state of the repeatedly bending device becomes more excellent. The pressure-sensitive adhesive layer 11 may be formed as a single layer, or may be formed by laminating a plurality of layers.

(1-2) Release Sheet The release sheets 12a and 12b protect the pressure-sensitive adhesive layer 11 until the pressure-sensitive adhesive sheet 1 is used, and are peeled off when the pressure-sensitive adhesive sheet 1 (adhesive layer 11) is used. In the pressure-sensitive adhesive sheet 1 according to the present embodiment, one or both of the release sheets 12a and 12b are not always necessary.

Examples of the release sheets 12a and 12b include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, and polybutylene. Telephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene / (meth) acrylic acid copolymer film, ethylene / (meth) acrylic acid ester copolymer film, polystyrene film, polycarbonate film, polyimide film, fluorine A resin film or the like is used. In addition, these crosslinked films are also used. Further, these laminated films may be used.

It is preferable that the peeling surface (particularly the surface in contact with the pressure-sensitive adhesive layer 11) of the peeling sheets 12a and 12b is subjected to a peeling treatment. Examples of the release agent used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. Of the release sheets 12a and 12b, it is preferable that one of the release sheets is a heavy release type release sheet having a large release force and the other release sheet is a light release type release sheet having a small release force.

The thickness of the release sheets 12a and 12b is not particularly limited, but is usually about 20 to 150 μm.

(2) Physical Properties (2-1) Haze Value The haze value of the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably 70% or less, more preferably 60% or less, and particularly 50. % Or less, more preferably 40% or less. When the haze value of the pressure-sensitive adhesive layer 11 is 70% or less, transparency suitable for optical use (for display) can be ensured. The lower limit of the haze value of the pressure-sensitive adhesive layer 11 is not particularly limited, but is usually 0% or more. The haze value in the present specification is a value measured according to JIS K7136: 2000.

(2-2) Adhesive strength to the transparent conductive film The adhesive strength of the pressure-sensitive adhesive sheet 1 according to the present embodiment to the transparent conductive film made of ITO (tin-doped indium oxide) is preferably 5N / 25 mm or more as a lower limit value, and in particular. It is preferably 9N / 25mm or more, and more preferably 11N / 25mm or more. When the adhesive strength of the adhesive sheet 1 is 5 N / 25 mm or more, the durability becomes more excellent especially when the adherend is a transparent conductive film. On the other hand, the upper limit of the adhesive strength is not particularly limited, but is usually preferably 100 N / 25 mm or less, more preferably 75 N / 25 mm or less, and particularly preferably 50 N / 25 mm or less. The adhesive strength basically refers to the adhesive strength measured by the 180-degree peeling method according to JIS Z0237: 2009, and the specific test method is as shown in the test example described later.

(3) Production of Adhesive Sheet As an example of production of the adhesive sheet 1, a case where the adhesive composition P is used will be described. The coating liquid of the adhesive composition P is applied to the peeling surface of one of the release sheets 12a (or 12b), heat-treated to heat-crosslink the adhesive composition P to form a coating layer, and then the coating thereof. The peeling surface of the other peeling sheet 12b (or 12a) is superposed on the layer. When the curing period is required, the curing period is set, and when the curing period is not required, the coating layer becomes the adhesive layer 11 as it is. As a result, the adhesive sheet 1 is obtained. The conditions for heat treatment and curing are as described above.

As another production example of the pressure-sensitive adhesive sheet 1, a coating liquid of the pressure-sensitive adhesive composition P is applied to the peel-off surface of one of the release sheets 12a, heat-treated to heat-crosslink the pressure-sensitive adhesive composition P, and the coating layer is formed. To obtain a release sheet 12a with a coating layer. Further, the coating liquid of the adhesive composition P is applied to the peeling surface of the other release sheet 12b, heat-treated to heat-crosslink the adhesive composition P to form a coating layer, and the coating layer is attached. To obtain the release sheet 12b of. Then, the release sheet 12a with the coating layer and the release sheet 12b with the coating layer are bonded so that both coating layers are in contact with each other. When the curing period is required, the curing period is set, and when the curing period is not required, the above-mentioned laminated coating layer becomes the pressure-sensitive adhesive layer 11. As a result, the adhesive sheet 1 is obtained. According to this production example, even when the pressure-sensitive adhesive layer 11 is thick, stable production is possible.

As a method for applying the coating liquid of the adhesive composition P, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method and the like can be used.

[Repeatly bent laminated member]
As shown in FIG. 2, the repetitive bending laminated member 2 according to the present embodiment includes a first flexible member 21 (one flexible member) and a second flexible member 22 (another flexible member). , Which is located between them and comprises an adhesive layer 11 that attaches the first flexible member 21 and the second flexible member 22 to each other.

The pressure-sensitive adhesive layer 11 in the repeatedly bent laminated member 2 is the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 described above.

The repetitive bending laminated member 2 is a repetitive bending device itself or a member constituting a part of the repetitive bending device. The repetitive bending device is preferably, but is not limited to, a display capable of repeated bending (including bending). Examples of such a repetitive bending device include an organic electroluminescence (organic EL) display, an electrophoretic display (electronic paper), a liquid crystal display using a plastic substrate (film) as a substrate, a foldable display, and the like, and a touch panel. It may be.

The first flexible member 21 and the second flexible member 22 are members capable of repeated bending (including bending), and are, for example, a cover film, a barrier film, a polarizing film, a splitter, a retardation film, and the like. Viewing angle compensation film, brightness improvement film, contrast improvement film, diffusion film, semi-transmissive reflective film, electrode film, transparent conductive film, metal mesh film, film sensor, liquid crystal polymer film, light emitting polymer film, film-like liquid crystal module, organic Examples thereof include an EL module (organic EL film) and an electronic paper module (film-like electronic paper).

Among the above, at least one of the first flexible member 21 and the second flexible member 22 is a display element that can be repeatedly bent, specifically, a liquid crystal polymer film, a light emitting polymer film, a film-shaped liquid crystal module, and an organic material. An EL module (organic EL film) or an electronic paper module (film-like electronic paper) is preferable.

It is also preferable that the first flexible member 21 and the second flexible member 22 include a material having a glass transition temperature of room temperature or lower as a constituent member. The glass transition temperature of the material having a glass transition temperature of room temperature or less is preferably 25 ° C. or lower, particularly preferably 10 ° C. or lower, and further preferably 0 ° C. or lower as an upper limit value. The lower limit of the glass transition temperature of a material having a glass transition temperature of room temperature or lower is not particularly limited, but is preferably −150 ° C. or higher, particularly preferably −100 ° C. or higher, and further preferably −80 ° C. or higher. Since the first flexible member 21 and the second flexible member 22 contain a material having a glass transition temperature of room temperature or lower as described above, the flexibility of each flexible member becomes good, and the flexible member is repeatedly bent. It becomes easy to make it.

The Young's modulus of the first flexible member 21 and the second flexible member 22 is preferably 0.1 to 10 GPa, particularly preferably 0.5 to 7 GPa, and further preferably 1.0 to 1.0 GPa, respectively. It is preferably 5 GPa. When the Young's modulus of the first flexible member 21 and the second flexible member 22 is within such a range, it becomes easy to repeatedly bend each flexible member.

The thickness of the first flexible member 21 and the second flexible member 22 is preferably 10 to 3000 μm, particularly preferably 25 to 1000 μm, and further preferably 50 to 500 μm. .. When the thickness of the first flexible member 21 and the second flexible member 22 is within such a range, it becomes easy to repeatedly bend each flexible member.

In order to manufacture the repeatedly bent laminated member 2, as an example, one of the release sheets 12a of the pressure-sensitive adhesive sheet 1 is peeled off, and the exposed pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 is removed from one of the first flexible members 21. Adhere to the surface of.

After that, the other release sheet 12b is peeled off from the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1, the exposed pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 and the second flexible member 22 are bonded to each other, and the bending laminated member 2 is repeatedly bent. To get. Further, as another example, the bonding order of the first flexible member 21 and the second flexible member 22 may be changed.

[Repeat bending device]
The repetitive bending device according to the present embodiment includes the repetitive bending laminated member 2 described above, and may be composed of only the repetitive bending laminated member 2, one or a plurality of repetitive bending laminated members 2, and another. It may be configured to include a flexible member. When laminating one repeatedly bent laminated member 2 and another repeatedly bent laminated member 2, or when laminating the repeatedly bent laminated member 2 and another flexible member, the adhesive layer 11 of the adhesive sheet 1 described above is used. It is preferable to stack the layers through the layers.

In the repetitive bending device according to the present embodiment, since the pressure-sensitive adhesive layer is made of the above-mentioned pressure-sensitive adhesive, the bending state is alleviated even after the external force is released in the case of repeated bending. For example, in an environment of 23 ° C., the bending angle at the bent portion can be suppressed to 30 ° or less and the bending height can be suppressed to 4 cm or less after repeatedly bending 30,000 times in a bending diameter of 4 mmφ.

Further, in the repetitive bending device according to the present embodiment, since the pressure-sensitive adhesive layer is made of the above-mentioned pressure-sensitive adhesive, a decrease in durability can be suppressed. For example, even when the product is left at 85 ° C. and 85% RH for 72 hours, it is possible to suppress the occurrence of floating or peeling at the interface between the flexible member and the pressure-sensitive adhesive layer.

The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

For example, either or both of the release sheets 12a and 12b in the pressure-sensitive adhesive sheet 1 may be omitted, or a desired optical member may be laminated in place of the release sheets 12a and / or 12b.

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the scope of the present invention is not limited to these Examples and the like.

[Example 1]
1. 1. Preparation of (meth) acrylic acid ester polymer (A) 47 parts by mass of n-butyl acrylate, 47 parts by mass of 2-ethylhexyl acrylate, 5 parts by mass of acrylic acid and 1 part by mass of 2-hydroxypropyl acrylate are copolymerized. A (meth) acrylic acid ester polymer (A) was prepared. When the molecular weight of this (meth) acrylic acid ester polymer (A) was measured by the method described later, the weight average molecular weight (Mw) was 700,000.

2. 2. Preparation of Adhesive Composition 100 parts by mass (solid content conversion value; the same applies hereinafter) of the (meth) acrylic acid ester polymer (A) obtained in the above step 1 and a trimethylol propane-modified bird as a cross-linking agent (B). Range isocyanate (B1: manufactured by Toyochem, product name "BHS8515") 1.5 parts by mass and polyrotaxane compound (C) (manufactured by Advanced Soft Materials, product name "SELM Superpolymer SH3400P", linear molecule: Polyethylene glycol, cyclic molecule: α-cyclodextrin having hydroxypropyl group and caprolactone chain, block group: adamantan group, weight average molecular weight (Mw) 700,000, hydroxyl value 72 mgKOH / g) 5 parts by mass, as a silane coupling agent 3-Glycydoxypropyltrimethoxysilane (0.28 part by mass) was mixed with the mixture, and the mixture was sufficiently stirred and diluted with methyl ethyl ketone to obtain a coating solution of the tacky composition.

3. 3. Manufacture of Adhesive Sheet Peeling of a heavy-release type release sheet (manufactured by Lintec Corporation, product name "SP-PET752150") in which one side of a polyethylene terephthalate film is peeled off with a silicone-based release agent from the coating solution of the obtained adhesive composition. The treated surface was coated with a knife coater. Then, the coated layer was heat-treated at 90 ° C. for 1 minute to form a coated layer.

Next, a light release type release sheet (manufactured by Lintec Corporation, product name "SP-PET382120") in which the coating layer on the heavy release type release sheet obtained above and one side of the polyethylene terephthalate film were peeled off with a silicone-based release agent). The adhesive layer having a thickness of 25 μm was formed by laminating the light peeling type peeling sheet so that the peeled surface of the light peeling type peeling sheet was in contact with the coating layer and curing it under the conditions of 23 ° C. and 50% RH for 7 days. An adhesive sheet having a structure, that is, a heavy release type release sheet / an adhesive layer (thickness: 25 μm) / a light release type release sheet, was produced. The thickness of the pressure-sensitive adhesive layer is a value measured using a constant pressure thickness measuring device (manufactured by TECLOCK Co., Ltd., product name "PG-02") in accordance with JIS K7130.

Here, Table 1 shows each formulation (solid content conversion value) of the adhesive composition when the (meth) acrylic acid ester polymer (A) is 100 parts by mass (solid content conversion value). The details of the abbreviations and the like shown in Table 1 are as follows.
[(Meta) acrylic acid ester polymer (A)]
BA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate ACMO: N-acryloylmorpholin IBXA: isobornyl acrylate AA: acrylate HEMA: 2-hydroxyethyl methacrylate HEA: 2-hydroxyethyl acrylate HPA: 2 acrylate -Hydroxypropyl
[Crosslinking agent (B)]
B1: Trimethylolpropane-modified tolylene diisocyanate (manufactured by Toyochem, product name "BHS8515")
B2: Trimethylolpropane-modified xylylene diisocyanate (manufactured by Soken Chemical Co., Ltd., product name "TD-75")

[Examples 2 to 9, Comparative Examples 1 to 4]
The type and ratio of each monomer constituting the (meth) acrylic acid ester polymer (A), the weight average molecular weight (Mw) of the (meth) acrylic acid ester polymer (A), the blending amount of the cross-linking agent (B), and the polyrotaxane. A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the blending amount of the compound (C) and the thickness of the pressure-sensitive adhesive layer were changed as shown in Table 1.

[Test Example 1] (Measurement of glass transition temperature)
The glass transition temperature (Tg) of the (meth) acrylic acid ester polymer (A) prepared and used in Examples and Comparative Examples is measured by the differential scanning calorimetry device (manufactured by TA Instruments Japan, product name). It was measured by "DSC Q2000") at a temperature rise / fall rate of 20 ° C./min. The results are shown in Table 1.

[Test Example 2] (Measurement of storage elastic modulus (G'))
A plurality of adhesive layers of the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples were laminated to form a laminated body having a thickness of 3 mm. A cylinder (height 3 mm) having a diameter of 8 mm was punched out from the obtained laminated body of the pressure-sensitive adhesive layer, and this was used as a sample.

The storage elastic modulus (G') (MPa) of the above sample was measured by a torsional shear method using a viscoelasticity measuring instrument (DYNAMIC ANALAYZER, manufactured by REOMETRIC) in accordance with JIS K7244-6 under the following conditions. The results are shown in Table 2.
Measurement frequency: 1Hz
Measurement temperature: -20 ° C, 23 ° C, 50 ° C

[Test Example 3] (Measurement of gel fraction)
The adhesive sheet produced in Examples and Comparative Examples was cut into a size of 80 mm × 80 mm, the adhesive layer was wrapped in a polyester mesh (mesh size 200), the mass was weighed with a precision balance, and the above mesh alone was used. The mass of the adhesive alone was calculated by subtracting the mass of. The mass at this time is M1.

Next, the pressure-sensitive adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23 ° C.) for 24 hours. After that, the adhesive was taken out, air-dried for 24 hours in an environment of a temperature of 23 ° C. and a relative humidity of 50%, and further dried in an oven at 80 ° C. for 12 hours. After drying, the mass was weighed with a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the mesh alone. The mass at this time is M2. The gel fraction (%) is represented by (M2 / M1) × 100. The results are shown in Table 2.

[Test Example 4] (Measurement of haze value)
For the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples, a haze value (%) was used using a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name “NDH-2000”) according to JIS K7136: 2000. Was measured. The results are shown in Table 2.

[Test Example 5] (Measurement of adhesive strength)
The light release type release sheet is peeled off from the adhesive sheets produced in Examples and Comparative Examples, and the exposed adhesive layer is easily applied to a polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., product name "Cosmo Shine A4300", thickness: 100 μm). It was bonded to the adhesive layer to obtain a laminate of a heavy release type release sheet / adhesive layer / PET film. The obtained laminate was cut into a width of 25 mm and a length of 100 mm.

In an environment of 23 ° C. and 50% RH, the heavy release type release sheet is peeled off from the laminate, the exposed pressure-sensitive adhesive layer is provided, and a transparent conductive film made of tin-doped indium oxide (ITO) is provided on one side. It was attached to a transparent conductive film of a terephthalate film (manufactured by Oike Kogyo Co., Ltd., product name "ITO film", thickness: 125 μm), and pressurized at 0.5 MPa, 50 ° C. for 20 minutes with an autoclave manufactured by Kurihara Seisakusho Co., Ltd. Then, after leaving it for 24 hours under the conditions of 23 ° C. and 50% RH, a tensile tester (manufactured by Orientec Co., Ltd., product name "Tencilon") was used under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180 degrees. , The adhesive strength (N / 25 mm) when the laminated body of the polyethylene terephthalate film and the adhesive layer was peeled from the transparent conductive film was measured. Conditions other than those described here were measured in accordance with JIS Z0237: 2009. The results are shown in Table 2.

[Test Example 6] (Tensile test)
A plurality of adhesive layers of the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples were laminated to make a total thickness of 800 μm, and then a sample having a width of 10 mm and a length of 75 mm was cut out. The above sample is set in a tensile tester (manufactured by Orientec, product name "Tencilon") so that the sample measurement site has a width of 10 mm and a length of 25 mm (extension direction), and the sample is measured in an environment of 23 ° C. and 50% RH. It was stretched at a tensile speed of 200 mm / min using a tensile tester. On the stress-strain curve (SS curve), the stress value at which the elongation rate is 100% was calculated (measured) as 100% modulus (N / mm ² ). Further, the sample was stretched until it broke, and the elongation at break (%) and the stress at rupture (N / mm ² ) were measured. The results are shown in Table 2.

[Test Example 7] (Bending test)
In an environment of 23 ° C. and 50% RH, the light release type release sheet was peeled off from the adhesive sheets produced in Examples and Comparative Examples, and the exposed adhesive layer was formed into a polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., product name). "Cosmo Shine 4300", thickness: 100 μm) was affixed to one side. Next, the heavy release type release sheet was peeled off, and the exposed adhesive layer was attached to one surface of another polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., product name "Cosmo Shine 4300", thickness: 100 μm). .. Then, after pressurizing with an autoclave manufactured by Kurihara Seisakusho at 0.5 MPa and 50 ° C. for 20 minutes, the mixture was left to stand for 24 hours under the conditions of 23 ° C. and 50% RH. The laminate composed of the PET film / adhesive layer / PET film thus obtained was cut into a width of 50 mm and a length of 200 mm, and this was used as a sample.

The obtained sample was repeatedly bent under the following conditions using a durability tester (manufactured by Yuasa System Equipment Co., Ltd., product name "plane body no-load U-shaped expansion / contraction tester"). Then, the sample was placed on a horizontal table, and one portion (part A) sandwiching the bent portion of the sample was fixed to the table surface. Then, the vertical distance (folding height; cm) from the table surface and the angle (folding angle; °) of the end portion of the other portion (part B) sandwiching the bent portion of the sample from the table surface are determined. It was measured. The results are shown in Table 2.
Bending diameter: 4 mmφ
Number of bends: 30,000 times Test temperature: 23 ° C

[Test Example 8] (Evaluation of durability)
A polyethylene terephthalate film (manufactured by Oike Kogyo Co., Ltd., ITO film, thickness: 125 μm) provided with a transparent conductive film made of tin-doped indium oxide (ITO) on one side of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples. ) And a polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., product name "Cosmo Shine A4300", thickness: 100 μm) were sandwiched between them to obtain a laminate.

The obtained laminate (sample) was autoclaved under the conditions of 50 ° C. and 0.5 MPa for 30 minutes, and then left at normal pressure at 23 ° C. and 50% RH for 24 hours. Then, it was stored for 72 hours under high temperature and high humidity conditions of 85 ° C. and 85% RH. After that, it was visually confirmed whether or not the interface between the pressure-sensitive adhesive layer and the adherend was lifted or peeled off, and the durability was evaluated according to the following criteria.
◎… There was no floating or peeling.
◯ ... One or two minute bubbles of less than 1 mm were generated, but there was no floating or peeling.
×… Floating or peeling occurred.

As can be seen from Table 2, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the example was excellent in the effect of alleviating the bending state and also in the durability under high temperature and high humidity conditions.

INDUSTRIAL APPLICABILITY The present invention is suitable for bonding one flexible member (for example, various films) constituting a repetitive bending device to another flexible member (for example, a display element).

1 ... Adhesive sheet 11 ... Adhesive layer 12a, 12b ... Peeling sheet 2 ... Repeated bending laminated member 21 ... First flexible member 22 ... Second flexible member

Claims (12)

An adhesive for a repetitive bending device for adhering one flexible member constituting a device to be repeatedly bent to another flexible member.
A pressure-sensitive adhesive for repetitive bending devices, which comprises a polyrotaxane compound. A claim comprising a pressure-sensitive adhesive obtained by cross-linking a pressure-sensitive adhesive composition containing the (meth) acrylic acid ester polymer (A), a cross-linking agent (B), and the polyrotaxane compound (C). The adhesive for a repetitive bending device according to 1. The pressure-sensitive adhesive for a repetitive bending device according to claim 1 or 2, wherein the storage elastic modulus G'(-20) at −20 ° C. is 0.01 MPa or more and 1.8 MPa or less. The pressure-sensitive adhesive for a repetitive bending device according to any one of claims 1 to 3, wherein the storage elastic modulus G'(50) at 50 ° C. is 0.001 MPa or more and 0.5 MPa or less. The pressure-sensitive adhesive for a repetitive bending device according to any one of claims 1 to 4, wherein the 100% modulus is 0.005 N / mm ² or more and 0.1 N / mm ² or less. The pressure-sensitive adhesive for a repetitive bending device according to any one of claims 1 to 5, wherein the elongation at break by a tensile test is 500% or more and 4000% or less. The pressure-sensitive adhesive for a repetitive bending device according to any one of claims 1 to 6, wherein the breaking stress in the tensile test is 0.2 N / mm ² or more and 5 N / mm ² or less. An adhesive sheet having an adhesive layer for adhering one flexible member and another flexible member constituting a device that is repeatedly bent.
A pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer comprises the pressure-sensitive adhesive for a repetitive bending device according to any one of claims 1 to 7. The adhesive sheet comprises two release sheets.
The pressure-sensitive adhesive sheet according to claim 8, wherein the pressure-sensitive adhesive layer is sandwiched between the peel-off sheets so as to be in contact with the peel-off surfaces of the two release sheets. With one flexible member and another flexible member constituting a device that is repeatedly bent,
It is a repetitive bending laminated member provided with an adhesive layer for bonding the one bending member and the other bending member to each other.
A repeatedly bent laminated member, wherein the pressure-sensitive adhesive layer is the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to claim 8. The repetitive bending laminated member according to claim 10, wherein at least one of the one bending member and the other bending member is a display element. A repetitive bending device comprising the repetitive bending laminated member according to claim 10 or 11.

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