JP7069066B2 - Repeated bending display - Google Patents

Description

The present invention relates to an adhesive sheet for a device that is repeatedly bent, as well as a repeatedly bent laminated member and a repeatedly bent device.

In recent years, a flexible flexible display has been proposed as a display body (display) of an electronic device, which is a kind of device. As the bendable display, in addition to the one that forms a curved surface only once, a repeatedly bendable display for the purpose of repeatedly bending (bending) has been proposed.

In a repetitive bending display as described above, it is conceivable 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. Be done. However, when a conventional pressure-sensitive adhesive sheet is used for a repeatedly bent display, there arises a problem that floating or peeling occurs at the interface between the pressure-sensitive adhesive layer and the adherend.

Patent Document 1 discloses a pressure-sensitive adhesive having an object of suppressing the occurrence of floating and peeling of the pressure-sensitive adhesive layer even if it is repeatedly bent.

Japanese Unexamined Patent Publication No. 2016-108555

On the other hand, in the repetitive bending display as described above, when the display is repeatedly bent, a line may be formed at the bent portion. The pressure-sensitive adhesive described in Patent Document 1 cannot sufficiently solve the problem of repeated flexibility.

The present invention has been made in view of the above-mentioned actual conditions, and an object of the present invention is to provide an adhesive sheet, a repeatedly bent laminated member, and a repeatedly bent device having excellent repeatability.

In order to achieve the above object, first, the present invention is an adhesive sheet having an adhesive layer for adhering one flexible member constituting a device to be repeatedly bent and another flexible member. The thickness of the pressure-sensitive adhesive layer is 2 μm or more and less than 100 μm, and the storage elasticity G'(-20) of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer at −20 ° C. is 0.01 MPa or more and 50 MPa. The two gas barrier films and the pressure-sensitive adhesive layer are laminated and fixed so that both sides of the pressure-sensitive adhesive layer are in contact with the gas barrier layers of the two gas barrier films. Provided is an adhesive sheet characterized in that the surface adhesive force, which is the maximum stress when the gas barrier film is pulled up in the vertical direction at a speed of 5 mm / min, is 35 N / cm ² or more (Invention 1).

The pressure-sensitive adhesive sheet according to the above invention (Invention 1) is a laminated body in which one flexible member and another flexible member are bonded to each other by the pressure-sensitive adhesive layer because the pressure-sensitive adhesive layer has the above-mentioned physical characteristics. When bent, it has excellent repeatability and it is difficult to form a line in the bent portion under a wide range of temperatures.

In the above invention (Invention 1), the two polyimide films and the pressure-sensitive adhesive layer are laminated and fixed so that both sides of the pressure-sensitive adhesive layer are in contact with the two polyimide films. It is preferable that the surface adhesive force, which is the maximum stress when the other polyimide film is pulled up in the vertical direction at a speed of 5 mm / min, is 30 N / cm ² or more (Invention 2).

In the above inventions (Inventions 1 and 2), the storage elastic modulus G'(85) of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer at 85 ° C. is preferably 0.005 MPa or more and 0.30 MPa or less (invention). 3).

In the above inventions (Inventions 1 to 3), the storage elastic modulus G'(25) of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer at 25 ° C. is preferably 0.01 MPa or more and 0.30 MPa or less (invention). 4).

In the above inventions (Inventions 1 to 4), the gel fraction of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is preferably 30% or more and 95% or less (Invention 5).

In the above inventions (Inventions 1 to 5), the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is preferably an acrylic pressure-sensitive adhesive (Invention 6).

In the above inventions (Inventions 1 to 6), 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 7).

Secondly, 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 composed of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (Invention 1 to 7) (Invention 8).

Thirdly, the present invention provides a repetitive bending device including the repetitive bending laminated member (invention 8) (invention 9).

The pressure-sensitive adhesive sheet, the repeatedly bent laminated member, and the repeatedly bent device according to the present invention are excellent in repeated bending property, and it is difficult to form a line in a bent portion under a wide range of temperatures.

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. It is sectional drawing of the repeated bending device which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described.
[Adhesive sheet]
The pressure-sensitive adhesive sheet according to an embodiment of the present invention has a pressure-sensitive adhesive layer for adhering one flexible member constituting a repeatedly bending device to another flexible member, and the pressure-sensitive adhesive is preferable. A release sheet is laminated on one side or both sides of the agent layer. The repetitive bending device and the flexible member will be described later.

The thickness of the pressure-sensitive adhesive layer (value measured according to JIS K7130) is 2 μm or more and less than 100 μm. The storage elastic modulus G'(-20) of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer at −20 ° C. is 0.01 MPa or more and 50 MPa or less. Further, the two gas barrier films and the pressure-sensitive adhesive layer are laminated and fixed so that both sides of the pressure-sensitive adhesive layer are in contact with the gas barrier layers of the two gas barrier films. The surface adhesive force, which is the maximum stress when the film is pulled up in the vertical direction at a speed of 5 mm / min, is 35 N / cm ² or more.

Since the pressure-sensitive adhesive layer in the present embodiment has the above-mentioned physical properties, when the laminate formed by bonding one flexible member and another flexible member by the pressure-sensitive adhesive layer is bent, it is repeatedly bent. It has excellent properties, and it is difficult to form a line at the bent portion under a wide range of temperatures. In particular, when the above-mentioned surface adhesive force is 35 N / cm ² or more, it is possible to suppress the occurrence of floating or peeling at the interface between the pressure-sensitive adhesive layer and the adherend even if it is repeatedly bent. Further, in particular, when the storage elastic modulus G'(-20) is 0.01 MPa or more, it is presumed that minute floating is unlikely to occur at the interface between the pressure-sensitive adhesive layer and the adherend. Further, in particular, when the storage elastic modulus G'(-20) is 50 MPa or less, the action on the adherend due to the hardness of the pressure-sensitive adhesive layer becomes small, and it becomes difficult to form a line on the adherend itself. Further, in particular, when the thickness of the pressure-sensitive adhesive layer is 2 μm or more, it is easy to exert a desired adhesive force, and it is possible to effectively suppress the formation of lines at the bent portion. Further, in particular, when the thickness of the pressure-sensitive adhesive layer is less than 100 μm, the force acting on the adherend from the pressure-sensitive adhesive layer at the time of bending is relaxed, and the repeatability becomes better. It is considered that it becomes difficult to form a line in the bent portion under a wide temperature by comprehensively exerting such an action and effect. Specifically, even when the laminate is bent 30,000 times at temperatures of -20 ° C, 25 ° C, and 85 ° C, it is difficult for lines to form at the bent portion, and of course, bubbles, floating, and peeling occur. It is suppressed. In particular, even when one flexible member in the laminated body is a gas barrier film or a laminated body containing a gas barrier film, the above-mentioned excellent repetitive flexibility is exhibited.

From the viewpoint of the repeatability described above, the storage elastic modulus G'(-20) of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer at −20 ° C. needs to be 0.01 MPa or more, and is 0.02 MPa or more. It is preferably 0.06 MPa or more, and more preferably 0.08 MPa or more. Similarly, from the viewpoint of repeatability, the storage elastic modulus G'(-20) at −20 ° C. needs to be 50 MPa or less, preferably 10 MPa or less, more preferably 1 MPa or less, and particularly particularly. It is preferably less than 0.3 MPa, more preferably less than 0.1 MPa.

The storage elastic modulus G'(85) of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer at 85 ° C. is preferably 0.30 MPa or less, more preferably 0.23 MPa or less, and particularly 0.14 MPa or less. It is preferably 0.09 MPa or less, and most preferably 0.03 MPa or less. As a result, the force acting on the adherend from the pressure-sensitive adhesive layer is reduced with bending, and a device having excellent bending resistance at high temperatures can be obtained. On the other hand, the storage elastic modulus G'(85) at 85 ° C. is preferably 0.005 MPa or more, more preferably 0.008 MPa or more, and particularly preferably 0.01 MPa or more. As a result, the adhesive layer does not become too soft even at high temperatures, and the cohesive force is maintained. At the same time, it is difficult for the adhesive layer to have a density difference between the bent portion and the non-bent portion. It is easy to suppress the occurrence of such things.

The storage elastic modulus G'(25) of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer at 25 ° C. is preferably 0.30 MPa or less, more preferably 0.20 MPa or less, and particularly 0.09 MPa or less. It is preferably present, and more preferably 0.05 MPa or less. This makes it easier to exhibit adhesiveness. On the other hand, the storage elastic modulus G'(25) at 25 ° C. is preferably 0.01 MPa or more, more preferably 0.02 MPa or more, and particularly preferably 0.03 MPa or more. As a result, the repeatability in the standard ambient temperature region is excellent, and the workability such as tip cutting is improved.

The method for measuring the storage elastic modulus in the present specification is as shown in a test example described later.

The surface adhesive force of the pressure-sensitive adhesive layer to the gas barrier film needs to be 35 N / cm ² or more, preferably 38 N / cm ^{2 or more, and particularly 40 N / cm 2 or} more, from the viewpoint of the repeatability described above. It is preferably 45 N / cm ² or more. On the other hand, the upper limit of the surface adhesive force is not particularly limited, but is preferably 1000 N / cm ² or less, particularly preferably 500 N / cm ² or less, and further 100 N / cm ² from the viewpoint of reworkability. The following is preferable.

In the method for measuring the surface adhesive force of the pressure-sensitive adhesive layer on the gas barrier film, specifically, first, a gas barrier film having a gas barrier layer made of modified polysilazane is attached to a glass plate (the gas barrier layer side is an exposed surface). Prepare a sheet. Then, the pressure-sensitive adhesive layer is sandwiched between the two gas barrier films so that the gas barrier layer of each gas barrier film is in contact with the pressure-sensitive adhesive layer (10 mm × 10 mm). Then, as the maximum stress (N / cm ² ) when one gas barrier film is fixed and the other gas barrier film is pulled up in the vertical direction (perpendicular to the plane of the horizontally installed gas barrier film) at a speed of 5 mm / min. Can be measured. A more detailed measurement method is as shown in a test example described later.

Further, the two polyimide films and the pressure-sensitive adhesive layer are laminated and fixed so that both sides of the pressure-sensitive adhesive layer are in contact with the two polyimide films, respectively, and the other polyimide film is vertically attached from one of the fixed polyimide films. The surface adhesive force, which is the maximum stress when pulled up at a speed of 5 mm / min, is preferably 30 N / cm ² or more. Thereby, in particular, even when one flexible member in the laminated body is a polyimide film or a laminated body containing the polyimide film, the above-mentioned excellent repeatability is satisfactorily exhibited.

The surface adhesive force of the pressure-sensitive adhesive layer to the polyimide film is preferably 30 N / cm ² or more, particularly preferably 35 N / cm ² or more, and further 40 N / cm ² from the viewpoint of the repeatability described above. The above is preferable. On the other hand, the upper limit of the surface adhesive force is not particularly limited, but is preferably 1000 N / cm ² or less, particularly preferably 500 N / cm ² or less, and further 100 N / cm ² from the viewpoint of reworkability. The following is preferable.

The method for measuring the surface adhesive force of the pressure-sensitive adhesive layer on the polyimide film is the same as the method for measuring the surface adhesive force on the gas barrier film, except that the adherend is changed from the gas barrier film to the polyimide film.

The gel fraction of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is preferably 30% or more, more preferably 40% or more, particularly preferably 50% or more, and further preferably 60% or more. It is preferable to have. As a result, the pressure-sensitive adhesive exhibits a suitable cohesive force that can withstand repeated bending. As a result, the above-mentioned repetitive flexibility becomes more excellent. On the other hand, the gel fraction of the pressure-sensitive adhesive in the present embodiment is preferably 95% or less, more preferably 90% or less, particularly preferably 85% or less, and further preferably 80% or less. It is preferably 77% or less, and most preferably 77% or less. As a result, it is presumed that the destruction of the crosslinked structure in the pressure-sensitive adhesive due to repeated bending is suppressed, and the pressure-sensitive adhesive layer itself is suppressed from becoming cloudy. The method for measuring the gel fraction in the present specification is as shown in a test example described later.

The lower limit of the thickness of the pressure-sensitive adhesive layer needs to be 2 μm or more, preferably 5 μm or more, and more preferably 10 μm or more, from the viewpoint of repetitive flexibility due to the adhesive force. In particular, it is preferably 15 μm or more, and more preferably 20 μm or more. Further, the upper limit of the thickness of the pressure-sensitive adhesive layer needs to be less than 100 μm from the viewpoint of repeated flexibility due to the force acting on the adherend from the pressure-sensitive adhesive layer, and may be 80 μm or less. It is more preferably 60 μm or less, particularly preferably 40 μm or less, and further preferably 30 μm or less from the viewpoint of obtaining a thinner repetitive bending device. The pressure-sensitive adhesive layer may be formed as a single layer, or may be formed by laminating a plurality of layers.

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. 1. Components 1-1. Adhesive layer The adhesive layer 11 has the above-mentioned physical properties and thickness.
The type of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 11 is not particularly limited as long as the above physical properties (particularly, the storage elasticity G'(-20) at −20 ° C. and the surface adhesive force to the gas barrier film) are satisfied, and for example, acrylic. Any of a based 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 may be used. 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 satisfies the above-mentioned physical properties and is excellent in adhesive physical properties, optical properties, etc. is preferable, and a solvent-type acrylic pressure-sensitive adhesive is particularly preferable.

Specifically, the pressure-sensitive adhesive in the present embodiment is a pressure-sensitive adhesive composition containing a (meth) acrylic acid ester polymer (A) and a cross-linking agent (B) (hereinafter referred to as “sticky composition P”). It is preferable that the pressure-sensitive adhesive is obtained by cross-linking (there is). With such an adhesive, it is easy to satisfy the above-mentioned physical properties, and it is easy to obtain good adhesive strength. 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 (meth) acrylic acid ester polymer (A) is a (meth) acrylic acid alkyl ester and a monomer having a reactive functional group in the molecule (monomer containing a reactive functional group) as a monomer unit constituting the polymer. And are preferably contained.

The (meth) acrylic acid ester polymer (A) can exhibit preferable tackiness by containing the (meth) acrylic acid alkyl ester as the monomer unit constituting the polymer. As the (meth) acrylic acid alkyl ester, a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms is preferable. The alkyl group may be linear or branched, or may have a cyclic structure.

Examples of the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms include methyl (meth) acrylic acid, ethyl (meth) acrylic acid, propyl (meth) acrylic acid, and n- (meth) acrylic acid. Butyl, (meth) acrylic acid n-pentyl, (meth) acrylic acid n-hexyl, (meth) acrylic acid 2-ethylhexyl, (meth) acrylic acid isooctyl, (meth) acrylic acid n-decyl, (meth) acrylic acid Examples thereof include n-dodecyl, myristyl (meth) acrylate, palmityl (meth) acrylate, and stearyl (meth) acrylate. Among them, the (meth) acrylic acid ester having 1 to 8 carbon atoms of the alkyl group is preferable, and the (meth) having 4 to 8 carbon atoms of the alkyl group is preferable from the viewpoint of the physical properties related to the storage elastic modulus G'and the surface adhesive force described above. Acrylic acid esters are particularly preferred. Specifically, n-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate are preferable, and n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferable. These may be used alone or in combination of two or more.

The (meth) acrylic acid ester polymer (A) preferably contains 60% by mass or more of the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms as the monomer unit constituting the polymer. , 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more. When the amount of the (meth) acrylic acid alkyl ester is equal to or more than the above amount, the (meth) acrylic acid ester polymer (A) can be imparted with suitable adhesiveness, and the storage elastic modulus G'is set to a low value. Easy to adjust. Further, it is preferable that the (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms of the alkyl group is contained in an amount of 99.9% by mass or less, particularly preferably 99.5% by mass or less, and further 99.0. It is preferably contained in an amount of% by mass or less. By setting the amount of the (meth) acrylic acid alkyl ester to the above amount or less, a desired amount of other monomer components can be introduced into the (meth) acrylic acid ester polymer (A).

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 pressure-sensitive adhesive easily satisfies the above-mentioned physical properties and surface adhesive force (and gel fraction) related to the storage elastic modulus G'.

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 reactive functional group-containing monomers, a hydroxyl group-containing monomer or a carboxy group-containing monomer is preferable, and a hydroxyl group-containing monomer is particularly preferable. The hydroxyl group-containing monomer easily satisfies the above-mentioned physical properties related to the storage elastic modulus G'. That is, if it is a hydroxyl group-containing monomer, the storage elastic modulus G'at low temperature can be reduced, and the storage elastic modulus G'of the obtained pressure-sensitive adhesive can be easily finely adjusted.

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). ) Hydroxyalkyl esters of (meth) acrylic acid such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylic acid can be mentioned. Among the above, a (meth) acrylic acid hydroxyalkyl ester having a hydroxyalkyl group having 1 to 4 carbon atoms is preferable from the viewpoint of easiness of satisfying the physical properties of the above-mentioned storage elastic modulus G'. Specifically, for example, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and the like are preferable, and 2-hydroxyethyl acrylate or 4-hydroxybutyl acrylate are particularly preferable. Be done. 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 adhesive strength of the obtained (meth) acrylic acid ester polymer (A). 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 as a lower limit value of 0.1% by mass or more as a monomer unit constituting the polymer, particularly 0.5. It is preferably contained in an amount of 1% by mass or more, and more preferably 1.0% 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 10% by mass or less, particularly 6% by mass, as a monomer unit constituting the polymer. It is preferably contained below, and more preferably 3% by mass or less. When the (meth) acrylic acid ester polymer (A) contains a reactive functional group-containing monomer in the above amount as a monomer unit, the cohesive force of the adhesive obtained by the cross-linking reaction with the cross-linking agent (B) is appropriate. Therefore, it becomes easy to satisfy the above-mentioned physical properties and surface adhesive force (and gel fraction) related to the storage elasticity G', especially the storage elasticity G'(-20) at −20 ° C.

It is also preferable that the (meth) acrylic acid ester polymer (A) does not contain a carboxy group-containing 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.

Here, "does not contain a carboxy group-containing monomer" means that the carboxy group-containing monomer is substantially not contained, and in addition to containing no carboxy group-containing monomer, a transparent conductive film using a carboxyl group, metal wiring, etc. It is permissible to contain a carboxy group-containing monomer to the extent that the corrosion of the above does not occur. Specifically, in the (meth) acrylic acid ester polymer (A), the carboxy group-containing monomer is contained in an amount of 0.1% by mass or less, preferably 0.01% by mass or less, more preferably 0.001 as a monomer unit. It is permissible to contain it in an amount of mass% or less.

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 inhibit the above-mentioned action of the reactive functional group-containing monomer. Examples of such monomers include non-reactive nitrogen atom-containing monomers such as N-acryloylmorpholine and N-vinyl-2-pyrrolidone, and (meth) such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate. Acrylic acid alkoxyalkyl esters, vinyl acetate, styrene and the like can be mentioned. 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 weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 250,000 or more, more preferably 300,000 or more, particularly preferably 400,000 or more, and further preferably 500,000. The above is preferable, and 700,000 or more is the most preferable. The weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 2.3 million or less, more preferably 2 million or less, particularly preferably 1.7 million or less, and further. It is preferably 1.4 million or less. When the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is within the above range, the physical characteristics, surface adhesive strength and gel fraction relating to the above-mentioned storage elastic modulus G'are likely to be satisfied. 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.

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 physical characteristics, surface adhesive force and gel fraction related to the above-mentioned storage elastic modulus G'are easily satisfied.

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 or 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 with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A), and particularly 0. It is preferably 06 parts by mass or more, and more preferably 0.12 parts by mass or more. The content is preferably 2.0 parts by mass or less, more preferably 1.5 parts by mass or less, particularly preferably 1.0 part by mass or less, and further preferably 0.5 parts by mass. It is preferably less than or equal to parts by mass. When the content of the cross-linking agent (B) is within the above range, the physical characteristics, surface adhesive strength and gel fraction related to the above-mentioned storage elastic modulus G'are likely to be satisfied.

(1-3) 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 adhesiveness with the flexible member which is an adherend is improved, and the adhesive strength becomes more preferable.

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 a silane coupling agent include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacrypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glyceride. Silicon compounds having an epoxy structure such as sidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyl Mercapto group-containing silicon compounds such as dimethoxymethylsilane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyl Amino group-containing silicon compounds such as dimethoxysilane, 3-chloropropyltrimethoxysilane, 3-isoxapropyltriethoxysilane, or at least one of these, and methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltri. Examples thereof include a condensate with an alkyl group-containing silicon compound such as methoxysilane. 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. When the content of the silane coupling agent is in the above range, the obtained pressure-sensitive adhesive layer has improved adhesion to the flexible member as an adherend and has a larger adhesive strength.

(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 with (B) and adding an additive if desired.

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. By polymerizing the (meth) acrylic acid ester polymer (A) by the solution polymerization method, it becomes easy to increase the molecular weight of the obtained polymer and adjust the molecular weight distribution, and further reduce the production of the low molecular weight compound. Is possible. Therefore, even when the gel fraction is relatively small and the degree of cross-linking is loosened, it is difficult for the pressure-sensitive adhesive to be biased due to repeated bending, and it is easy to obtain a pressure-sensitive adhesive having excellent repeatability.

Examples of the polymerization solvent used in the solution polymerization method 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 cross-linking agent (B) and, if desired, an additive and a diluting solvent are sufficiently added to the solution of the (meth) acrylic acid ester polymer (A). To obtain a tacky composition P (coating solution) diluted with a solvent.

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 pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 11 in the present embodiment is preferably obtained by cross-linking the pressure-sensitive 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.

1-2. Peeling Sheets The peeling 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. 2. Physical Properties (1) Adhesive Strength The adhesive strength of the adhesive sheet 1 according to the present embodiment to soda lime glass is preferably 1.0 N / 25 mm or more as a lower limit value, and more preferably 2.0 N / 25 mm or more. In particular, it is preferably 3.0 N / 25 mm or more, and more preferably 5.0 N / 25 mm or more. When the lower limit of the adhesive force of the adhesive sheet 1 to the soda lime glass is the above, the repeatability becomes more excellent. On the other hand, the upper limit of the adhesive strength is not particularly limited, but usually, it is preferably 50 N / 25 mm or less, more preferably 40 N / 25 mm or less, and when the adhesive sheet is mistakenly bonded, the adhesive sheet is used. From the viewpoint of reworkability that enables re-sticking, it is particularly preferably 30 N / 25 mm or less, and further preferably 20 N / 25 mm or less.

(2) 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 30% or less, more preferably 10% or less, and particularly preferably 5% or less. It is preferable, more preferably 1% or less. Since the haze value of the pressure-sensitive adhesive layer 11 is as described above, the pressure-sensitive adhesive layer 11 is excellent in light transmission and is suitable for a repeatedly bent display. The lower limit of the haze value is not particularly limited, and is preferably 0% or more, and more preferably 0.1% or more.

The haze value is a characteristic value including the thickness of the pressure-sensitive adhesive layer, and it is preferable to satisfy the haze value regardless of the thickness of the pressure-sensitive adhesive layer. Here, the haze value in the present specification is a value measured according to JIS K7136: 2000.

(3) Color Taste The pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment has a chromaticity a * defined by the CIE1976L * a * b * color system of −5.0 to 5.0. Is preferable, and particularly preferably −3.0 to 3.0, and further preferably −2.0 to 2.0. Further, the pressure-sensitive adhesive layer 11 preferably has a chromaticity b * defined by the CIE1976L * a * b * color system of −5.0 to 5.0, and particularly −3.0 to 3.0. It is preferably -2.0 to 2.0. When the chromaticity a * and the chromaticity b * are in the above ranges, the pressure-sensitive adhesive layer 11 becomes almost colorless and transparent, and is suitable for a repeatedly bent display. The methods for measuring the chromaticity a * and the chromaticity b * in the present specification are as shown in the test examples described later.

3. 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 relatively 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 (repeated bending 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 gas barrier film, a hard coat film, and a polarizing film (platelet). , Polarizer, retardation film (phase difference plate), viewing angle compensation film, brightness improving film, contrast improving film, diffusion film, semi-transmissive reflective film, electrode film, transparent conductive film, metal mesh film, film sensor (touch) Sensor film), liquid crystal polymer film, light emitting polymer film, film-like liquid crystal module, organic EL module (organic EL film, organic EL element), electronic paper module (film-like electronic paper), TFT (Thin Film Transistor) substrate, etc. Be done.

Among the above, it is preferable that one of the first flexible member 21 and the second flexible member 22 is a gas barrier film or a laminated body having a gas barrier film on the pressure-sensitive adhesive layer 11 side. Further, it is particularly preferable that the other of the first flexible member 21 and the second flexible member 22 is a polyimide film or a laminate having a polyimide film on the pressure-sensitive adhesive layer 11 side. The gas barrier film and the polyimide film generally have low adhesion to the pressure-sensitive adhesive layer, but according to the pressure-sensitive adhesive layer 11 in the present embodiment, even if the gas barrier film or the polyimide film is an adherend, it is repeatedly flexible. It is excellent in and it becomes difficult to form a line in the bent part under a wide range of temperatures.

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, it is repeatedly bent under a wide range of temperatures (for example, at temperatures of −20 ° C., 25 ° C., and 85 ° C.) (for example). Even at 30,000 times), the formation of lines at the bent portion is suppressed, and of course, the occurrence of bubbles and floating / peeling is also suppressed.

FIG. 3 shows a repetitive bending device as an example in the present embodiment. The repetitive bending device according to the present invention is not limited to the repetitive bending device.

As shown in FIG. 3, the repetitive bending device 3 according to the present embodiment includes a cover film 31, a first pressure-sensitive adhesive layer 32, a polarizing film 33, and a second pressure-sensitive adhesive layer 34, in order from the top. The touch sensor film 35, the third pressure-sensitive adhesive layer 36, the organic EL element 37, the fourth pressure-sensitive adhesive layer 38, and the TFT substrate 39 are laminated. The cover film 31, the polarizing film 33, the touch sensor film 35, the organic EL element 37, and the TFT substrate 39 correspond to the flexible member.

At least one of the first pressure-sensitive adhesive layer 32, the second pressure-sensitive adhesive layer 34, the third pressure-sensitive adhesive layer 36, and the fourth pressure-sensitive adhesive layer 38 is the pressure-sensitive adhesive layer 11 of the above-mentioned pressure-sensitive adhesive sheet 1. be. Any two or more of the first pressure-sensitive adhesive layer 32, the second pressure-sensitive adhesive layer 34, the third pressure-sensitive adhesive layer 36, and the fourth pressure-sensitive adhesive layer 38 is the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 described above. It is preferable that all the pressure-sensitive adhesive layers 32, 34, 36, and 38 are the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1.

The cover film 31 is a laminated body having a gas barrier film having a gas barrier layer on the first pressure-sensitive adhesive layer 32 side, or a gas barrier film (the gas barrier layer is on the pressure-sensitive adhesive layer 11 side) on the first pressure-sensitive adhesive layer 32 side. Is preferable. In this case, at least the first pressure-sensitive adhesive layer 32 is preferably the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 described above. Further, for example, when the TFT substrate 39 contains a polyimide film, particularly when the polyimide film is provided on the side of the fourth pressure-sensitive adhesive layer 38, at least the fourth pressure-sensitive adhesive layer 38 is the above-mentioned pressure-sensitive adhesive sheet 1. The pressure-sensitive adhesive layer 11 is preferable.

In the repeated bending device 3, at least the pressure-sensitive adhesive of the adhesive sheet 1 is obtained even when the device 3 is repeatedly bent under a wide range of temperatures (for example, at temperatures of −20 ° C., 25 ° C., and 85 ° C.) (for example, 30,000 times). In the laminated portion of the pressure-sensitive adhesive layer composed of the layer 11 and the flexible member bonded by the pressure-sensitive adhesive layer, it is suppressed that a line is formed in the bent portion, and of course, the generation of air bubbles and floating / peeling is also suppressed.

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 flexible 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) 49 parts by mass of n-butyl acrylate, 50 parts by mass of 2-ethylhexyl acrylate, and 1 part by mass of 4-hydroxybutyl acrylate were copolymerized by a solution polymerization method. , (Meta) 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 790,000.

2. 2. Preparation of Adhesive Composition 100 parts by mass (solid content conversion value; the same shall apply hereinafter) of the (meth) acrylic acid ester polymer obtained in the above step 1 and trimethylol propane-modified xiri as a cross-linking agent (B). 0.15 parts by mass of range isocyanate (XDI; manufactured by Soken Kagaku Co., Ltd., product name "TD-75") and 0.20 parts by mass of 3-glycidoxypropyltrimethoxysilane (Si1) as a silane coupling agent. A coating solution of the tacky composition was obtained by mixing, stirring well and diluting with methyl ethyl ketone.

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-PET381130") 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 Ester Polymer (A)]
BA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate 4HBA: 4-hydroxybutyl acrylate AA: HEA acrylate: 2-hydroxyethyl acrylate MA: methyl acrylate EO9: polyethylene glycol methacrylate (9 mol of ethylene oxide) Additives)
[Crosslinking agent (B)]
XDI: Trimethylolpropane-modified xylylene diisocyanate (manufactured by Soken Chemical Co., Ltd., product name "TD-75")
TDI: Trimethylolpropane-modified tolylene diisocyanate (manufactured by Toyochem, product name "BHS8515")
HDI: Hexamethylene diisocyanate

[Examples 2 to 8, Comparative Examples 1 to 6]
Types and proportions of each monomer constituting the (meth) acrylic acid ester polymer (A), weight average molecular weight (Mw) of the (meth) acrylic acid ester polymer (A), type and blending amount of the cross-linking agent (B). , The pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the blending amount of the silane coupling agent and the thickness of the pressure-sensitive adhesive layer were changed as shown in Table 1. In Example 4 and Comparative Example 1, the thickness of the pressure-sensitive adhesive layer was changed by changing the number of laminated coating layers formed on the lightly peelable release sheet.

[Manufacturing Example 1]
Using a polyethylene terephthalate (PET) film (manufactured by Toray Co., Ltd., product name "PET50A4100", thickness: 50 μm) with one side easily bonded as a base material, one side of the base material (smooth surface not easily bonded) A composition containing an ultraviolet (UV) curable resin and reactive silica (manufactured by JSR, product name "Opstar Z7530") is applied with a Meyer bar to form a coating film, and the coating film is applied at 70 ° C. for 1 minute. It was dried. Then, using a conveyor type UV light irradiation device (manufactured by Fusion Co., Ltd., product name "F600V"), the coating film is irradiated with UV under the following conditions to cure the coating film, and an anchor coat having a thickness of 1 μm is obtained. Formed a layer.
<UV irradiation conditions>
・ UV lamp: High-pressure mercury lamp ・ Line speed: 20 m / min ・ Integrated light intensity: 120 mJ / cm ²
・ Illuminance: 200mW / cm ²
・ Lamp height: 104 mm

Next, a coating material containing perhydropolysilazane as a main component (manufactured by Merck Performance Materials, product name “AZ-110a-20”) was applied to the surface of the anchor coat layer by a spin coating method. Then, it was heated at 120 ° C. for 1 minute to form a polysilazane layer containing perhydropolysilazane. The thickness of the formed polysilazane layer was 200 nm.

Next, using a plasma ion implantation device, argon (Ar) was implanted into the surface of the polysilazane layer by plasma ions to form a gas barrier layer made of modified polysilazane. In this way, a gas barrier film having a gas barrier layer made of modified polysilazane on one side of the base material (PET film) was obtained. The modification of polysilazane proceeds from the surface of the polysilazane layer. Therefore, the degree of modification does not affect the surface condition of the gas barrier layer, and therefore does not affect the bending resistance or the like.

[Test Example 1] (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 (product name: Tetron mesh # 200), and the mass was weighed with a precision balance. By subtracting the mass of the mesh alone, the mass of the adhesive alone was calculated. 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 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.

For the above sample, the storage elastic modulus G'was measured under the following conditions by the torsional shear method using a viscoelastic measuring instrument (DYNAMIC ANALAYZER, manufactured by REOMETRIC) in accordance with JIS K7244-6, and stored at -20 ° C. Elastic modulus G'(-20), storage elastic modulus G'(25) at 25 ° C. and storage elastic modulus G'(85) (MPa) at 85 ° C. were obtained. The results are shown in Table 2.
Measurement frequency: 1Hz
Measurement temperature: -20 ° C to 140 ° C

[Test Example 3] (Measurement of surface adhesion)
(1) Surface Adhesive Force to Gas Barrier Film The gas barrier film produced in Production Example 1 was cut into 25 mm × 25 mm and fixed to a glass plate (thickness 3 mm) with an adhesive so that the gas barrier layer was an exposed surface. Two pieces of this were prepared as test pieces.

The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were cut into 10 mm × 10 mm, and the pressure-sensitive adhesive layer was brought into contact with the respective gas barrier layer in the central portion of the two test pieces. It was sandwiched and pasted together. Then, after pressurizing with an autoclave manufactured by Kurihara Seisakusho Co., Ltd. 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, and this was used as a measurement sample.

Using a special jig, the obtained measurement sample is placed on the ground with the flat surface (main surface) of the gas barrier film against a universal tensile tester (manufactured by Orientec, product name "Tensilon RTA-T-2M"). It was installed so that it would be horizontal. Then, the maximum stress (N / cm) measured until the test piece is completely peeled off by pulling up the test piece from one fixed test piece in the vertical direction (perpendicular to the plane of the gas barrier film) at a speed of 5 mm / min. ² ) was defined as the surface adhesive force (surface adhesive force to the gas barrier film). The results are shown in Table 2.

(2) Surface adhesion to polyimide film Polyimide (PI) film (manufactured by Toray DuPont, product name "Kapton 100PI", thickness: 25 μm) is cut into 25 mm × 25 mm, and a glass plate (thickness 3 mm) is cut with an adhesive. Fixed to. Two pieces of this were prepared as test pieces. For this test piece, the surface adhesive force (surface adhesive force to the polyimide film) was measured in the same manner as in (1) above. The results are shown in Table 2.

[Test Example 4] (Measurement of adhesive strength)
The light release type release sheet is peeled off from the adhesive sheets obtained in Examples and Comparative Examples, and the exposed adhesive layer is a polyethylene terephthalate (PET) film having an easy adhesive layer (manufactured by Toyobo Co., Ltd., product name "PET A4300"). , Thickness: 100 μm) was bonded to an easy-adhesive layer to obtain a laminated body 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 110 mm.

In an environment of 23 ° C. and 50% RH, the heavy release type release sheet is peeled off from the above laminated body, and the exposed adhesive layer is one of a soda lime glass plate (manufactured by Nippon Sheet Glass Co., Ltd., thickness: 1.1 mm). It was affixed to the surface of No. 1 and pressurized at 0.5 MPa and 50 ° C. for 20 minutes in an autoclave manufactured by Kurihara Seisakusho. Then, after leaving it for 24 hours under the conditions of 23 ° C. and 50% RH, a PET film was used under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180 degrees using a tensile tester (Tensilon manufactured by Orientec). The adhesive force (N / 25 mm) when the laminated body with the adhesive layer was peeled off from the adherend 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 5] (Measurement of haze value)
The light peeling type peeling sheet was peeled off from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was attached to glass, and this was used as a sample for measurement. After performing background measurement with glass, the heavy release type release sheet is peeled off from the above measurement sample to expose the adhesive surface, and under the condition of 23 ° C., a haze meter (haze meter) according to JIS K7136: 2000. The haze value (%) was measured using a product name "NDH-5000" manufactured by Nippon Denshoku Kogyo Co., Ltd.). The results are shown in Table 2.

[Test Example 6] (Measurement of L * a * b *)
For the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, a simultaneous photometric spectroscopic chromaticity meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name "SQ2000") was used, and CIE1976L * a * b * color was applied. The chromaticity a * and chromaticity b * defined by the system were measured. The results are shown in Table 2.

[Test Example 7] (Evaluation of repeated flexibility)
In an environment of 23 ° C. and 50% RH, the light peeling type peeling sheet was peeled off from the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was formed into a polyimide (PI) film (manufactured by Toray DuPont). , Product name "Kapton 100PI", Thickness: 25 μm, Young's modulus: 3.4 GPa). Next, the heavy release type release sheet was peeled off, and the exposed pressure-sensitive adhesive layer was attached to the gas barrier layer surface of the gas barrier film (Young's modulus: 4.2 GPa) produced in Production Example 1. 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 PI film / adhesive layer / gas barrier 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"). After that, the state of the bent portion was visually confirmed, and the repeatability at each test temperature was evaluated according to the following criteria. The results are shown in Table 2.

<Test conditions>
Bending direction: Bending so that the PI film side faces each other Minimum bending diameter: 3 mmφ
Number of bends: 30,000 times Test temperature: -20 ° C, 25 ° C, 85 ° C
<Evaluation criteria for repeated flexibility>
◎… There is no line at the bent part.
〇… There is a line at the bent part, and the existence of the line can be confirmed even when viewed from the front.
Δ: Bubbles are generated in a part of the bent portion.
×: Floating / peeling has occurred at the bent portion.

As can be seen from Table 2, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the example has a line formed at the bent portion when two flexible members are bonded and repeatedly bent at each temperature from low temperature to high temperature. Was able to be suppressed. In addition, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the example had a high degree of colorless transparency.

INDUSTRIAL APPLICABILITY The present invention is suitable for bonding one flexible member (particularly a gas barrier film or a laminate containing a gas barrier film) constituting a repeatedly bending device to another flexible member.

1 ... Adhesive sheet 11 ... Adhesive layer 12a, 12b ... Peeling sheet 2 ... Repeated bending laminated member 21 ... First flexible member 22 ... Second flexible member 3 ... Repeated bending device 31 ... Cover film 32 ... First Adhesive layer 33 ... Polarizing film 34 ... Second adhesive layer 35 ... Touch sensor film 36 ... Third adhesive layer 37 ... Organic EL element 38 ... Fourth adhesive layer 39 ... TFT substrate

Claims (6)

With one flexible member and another flexible member that make up a display that is repeatedly bent,
It is a repetitive bending display provided with an adhesive layer for bonding the one bending member and the other bending member to each other.
The thickness of the pressure-sensitive adhesive layer is 10 μm or more and less than 100 μm.
The storage elastic modulus G'(-20) of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer at −20 ° C. is 0.01 MPa or more and 1 MPa or less .
The two gas barrier films and the pressure-sensitive adhesive layer are laminated so that both sides of the pressure-sensitive adhesive layer are in contact with the gas barrier layers of the two gas barrier films, and the other gas barrier film is vertically formed from one fixed gas barrier film. The surface adhesive force, which is the maximum stress when pulled up at a speed of 5 mm / min in the direction, is 35 N / cm ² or more.
It is repeatedly bent 30,000 times or more with a minimum bending diameter of 3 mmφ.
It features a repetitive bending display. The two polyimide films and the adhesive layer are laminated and fixed so that both sides of the pressure-sensitive adhesive layer are in contact with the two polyimide films, and the other polyimide film is vertically 5 mm from the fixed polyimide film. The repetitive bending display according to claim 1, wherein the surface adhesive force, which is the maximum stress when pulled up at a speed of / min, is 30 N / cm ² or more. The repetitive bending display according to claim 1 or 2, wherein the storage elastic modulus G'(85) of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer at 85 ° C. is 0.005 MPa or more and 0.30 MPa or less. .. The one according to any one of claims 1 to 3, wherein the storage elastic modulus G'(25) of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer at 25 ° C. is 0.01 MPa or more and 0.30 MPa or less. The described repetitive bending display. The repetitive bending display according to any one of claims 1 to 4, wherein the gel content of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is 30% or more and 95% or less. The repetitive bending display according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive.

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