TWI786201B - Adhesive for repetitive bending device, adhesive sheet, repetitive bending laminated member, and repetitive bending device - Google Patents

Abstract

[Problem] To provide a solution that can suppress the deformation of the adhesive layer after being released from the bent state when it is applied to a repeatedly bending device and repeatedly bends it, and when it is in a bent state for a long time, and alleviates the damage to the repeatedly bending device. Adhesives and adhesive sheets for repetitive bending devices for the effects of repeated bending and the effects of being in a bent state. [Solution] An adhesive for a repetitive bending device, which is an adhesive for a repetitive bending device for bonding one flexible member constituting the repetitive bending device to another flexible member, wherein a pressure of 3000 Pa is applied to the adhesive The value of the creep compliance modulus measured under stress is defined as the minimum creep compliance modulus J(t) _min (MPa ^-1 ), and 3000Pa continues to be applied after the aforementioned minimum creep compliance modulus J(t) _min is measured The stress until 3757 seconds has elapsed. The maximum creep compliance modulus measured during this period is defined as the maximum creep compliance modulus J(t) _max (MPa ^-1 ), which is calculated by the following formula (I): The variable compliance modulus ΔlogJ(t) is below 2.79. ΔlogJ(t) = log J(t) _max - log J(t) _min (I)

Description

Adhesive for repetitive bending device, adhesive sheet, repetitive bending laminated member, and repetitive bending device

The present invention relates to an adhesive and an adhesive sheet for a repetitive bending device, a repetitive bending laminated member, and a repetitive bending device.

In recent years, a flexible display has been proposed as a display body (display) of electronic equipment as a device. Such a flexible display, for example, can be bent and installed on a cylindrical column to be used as a fixed display, or it can be folded or rolled and carried to be used as a portable display, and its wide range of uses has attracted much attention. expect.

Examples of types of flexible displays include organic electroluminescence (organic EL) displays, electrophoretic displays (electronic paper), liquid crystal displays using plastic films as substrates, and the like.

In the flexible display as described above, it is generally considered that one flexible member (flexible member) constituting the flexible display is bonded to the other flexible member by an adhesive layer of an adhesive sheet. Here, as an adhesive sheet for conventional displays that cannot be bent, for example, adhesive sheets disclosed in Patent Document 1 and Patent Document 2 are known.

A flexible display is not formed into a curved surface only once, but as described in Patent Document 3, it may be bent (folded) repeatedly. Furthermore, such a repeatedly bendable display may also be fixed in a bent state for a long time. When a conventional adhesive sheet is used for such a repeatedly bendable device, even after it is released from the bent state, the adhesive layer deforms and the bendable display maintains a large bend and is fixed in such a bend. situation in the state. [Prior art literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2015-174907 [Patent Document 2] Japanese Patent Laid-Open No. 2016-774 [Patent Document 3] Japanese Patent Laid-Open No. 2016-2764

[Problems to be Solved by the Invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an adhesive and an adhesive sheet for a repetitive bending device, which can be used when the repetitive bending device is repeatedly bent and when it is in a bent state for a long time. After being released from the bent state, the deformation of the adhesive layer can also be suppressed, and the influence of repeated bending by the repeated bending device and the influence caused by being in a bent state can be alleviated, and a repeated bending laminated member and a repeated bending device can be provided. In the case of being bent and in the bent state for a long time, after releasing from the bent state, the influence caused by repeated bending and the influence caused by being in the bent state can be alleviated. [Means used to solve the problem]

In order to achieve the above object, first, the present invention provides an adhesive for a repetitive bending device, which is an adhesive for a repetitive bending device for bonding one flexible member constituting the repetitive bending device to another flexible member, wherein The creep compliance modulus value measured when a stress of 3000 Pa is applied to the aforementioned adhesive is defined as the minimum creep compliance modulus J(t) _min (MPa ^-1 ), and when the aforementioned minimum creep compliance modulus J ( After t) _min , continue to apply a stress of 3000Pa until 3757 seconds have elapsed. The maximum creep compliance modulus value measured during this period is defined as the maximum creep compliance modulus J(t) _max (MPa ^-1 ), which is given by the following formula (I) The calculated creep compliance modulus change value ΔlogJ(t) is 2.79 or less (Invention 1). ΔlogJ(t) = log J(t) _max - log J(t) _min (I)

In the above-mentioned invention (Invention 1), by satisfying the above-mentioned physical properties, in the case of applying to a repetitive bending device and repeatedly bending it and in the case of being in a bent state for a long time, after being released from the bent state, almost no Deformation of the adhesive layer occurs, and the repeatedly bending device can be suppressed from being fixed in a greatly bent state, and the effect of the repeatedly bending device being subjected to repeated bending and being in a bent state can be alleviated.

In the above invention (Invention 1), the loss tangent (tan δ) at 25° C. obtained by the dynamic viscoelasticity measurement method according to JIS K7244-1 is preferably 0.328 or more and 0.85 or less (Invention 2).

In the above-mentioned invention (Invention 2), by satisfying the above-mentioned physical properties, it becomes easy to exhibit a high adhesive force, and even when it is applied to a repeated bending device and it is bent repeatedly and in a bent state for a long time, As described above, the interface between the adhesive layer and the adherend can also be suppressed from peeling off at the bent portion by interacting with the fact that deformation of the adhesive layer hardly occurs.

In the above inventions (Inventions 1 and 2), the storage modulus (G') at 25°C is preferably not less than 0.01 MPa and not more than 0.25 MPa.

In the above inventions (Inventions 1 to 3), the loss modulus (G'') at 25°C is preferably not less than 0.005 MPa and not more than 0.10 MPa (Invention 4).

In the above inventions (Inventions 1 to 4), the adhesive is preferably an adhesive obtained by crosslinking an adhesive composition containing a (meth)acrylate polymer (A) and a crosslinking agent (B). (Invention 5).

Second, the present invention provides an adhesive sheet having an adhesive layer for attaching one flexible member constituting a repetitive bending device to another flexible member, wherein the adhesive layer is formed by the repetitive bending device. Formed (Invention 6) with an adhesive (Inventions 1-5).

In the above invention (Invention 6), preferably, the adhesive sheet includes two release sheets, and the adhesive layer is sandwiched by the release sheets so as to contact the release surfaces of the two release sheets (Invention 7).

Thirdly, the present invention provides a repetitive bending laminated member comprising one flexible member and other flexible members constituting a repetitive bending device, and an adhesive layer for bonding the one flexible member and the other flexible member to each other. A repeatedly bending laminated member, wherein the adhesive layer is the adhesive layer (Invention 8) of the aforementioned adhesive sheet (Invention 6, 7).

In the above invention (Invention 8), it is preferable that at least one of the one flexible member and the other flexible member is a display element (Invention 9).

Fourth, the present invention provides a repetitive bending device including the aforementioned repetitive bending laminated member (Inventions 8 and 9) (Invention 10). [Effect of the present invention]

According to the adhesive agent and the adhesive sheet for a repetitive bending device of the present invention, when it is applied to a repetitive bending device and it is bent repeatedly, or in the case of being in a bent state for a long time, after being released from the bent state, almost no damage occurs. The deformation of the adhesive layer can alleviate the influence of repeated bending and the influence caused by being in a bent state. Furthermore, according to the repetitive bending laminated member and the repetitive bending device of the present invention, when it is repeatedly bent or in a bent state for a long time, after being released from the bent state, it is possible to alleviate the influence of repeated bending and The effect of being in a bent state.

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

According to the adhesive of this embodiment, the creep compliance modulus (creep compliance) value measured when a stress of 3000 Pa is applied to the adhesive is defined as the minimum creep compliance modulus J(t) _min (MPa ^-1 ) , and after measuring the minimum creep compliance modulus J(t) _min , continue to apply a stress of 3000Pa until 3757 seconds have elapsed, and the maximum creep compliance modulus value measured during this period is defined as the maximum creep compliance modulus J(t) _max (MPa ^-1 ), the creep compliance modulus change value ΔlogJ(t) calculated from the following formula (I) is 2.79 or less. ΔlogJ(t) = log J(t) _max -log J(t) _min (I) In addition, "when a stress of 3000Pa is applied to the adhesive" refers to the time when a stress is applied to the adhesive and the stress reaches 3000Pa . The details of the measurement method of the creep compliance modulus J(t) are shown in Test Examples described later.

According to the adhesive of this embodiment, since it has a small variation value of the creep compliance modulus as described above, the variation in strain when a predetermined stress is applied is small, that is, almost no deformation occurs. Therefore, even when the adhesive layer formed of the aforementioned adhesive is repeatedly bent and in the bent state for a long time, the adhesive layer to which the adhesive layer is applied is released from the bent state. The adhesive layer is hardly deformed, and the repeatedly bending device can be suppressed from being fixed in a greatly bent state, and the influence of the repeatedly bending device being subjected to repeated bending and being in a bent state can be alleviated. Hereinafter, the above-mentioned effect may be referred to as "bending state alleviating effect of the repetitive bending device". In addition, as an index of the number of times of the above-mentioned repeated bending, for example, 30,000 times can be illustrated as an example.

Furthermore, according to the adhesive of the present embodiment, the loss tangent (tan δ) at 25° C. obtained according to the dynamic viscoelasticity measurement method of JIS K7244-1 is preferably not less than 0.328 and not more than 0.85. In addition, the details of the measurement method of the loss tangent (tan δ) are shown in Test Examples described later.

In particular, the adhesive according to the present embodiment has a high loss tangent (tan δ) as described above, so the viscosity becomes strong and it becomes easy to exhibit a high adhesive force. Therefore, when the repeatedly bending device using the adhesive layer formed by the aforementioned adhesive is repeatedly bent, or when it is in a bent state for a long time, it can be compatible with the small creep compliance modulus as described above. The interaction of deformation of the adhesive layer hardly occurs due to the variable value can suppress the peeling of the interface between the adhesive layer and the adherend at the bent portion. Hereinafter, the above-mentioned effect may be referred to as "interfacial peeling suppression effect".

From the point of view of the relaxation effect of the bending state of the repeated bending device, the above-mentioned creep compliance modulus change value ΔlogJ(t) needs to be 2.79 or less, preferably 2.30 or less, especially 2.00 or less, and further preferably 1.95 or less. better. In addition, the lower limit of the variation value of the creep compliance modulus is not particularly limited, and it is generally preferably above 1.00, especially preferably above 1.20.

The minimum creep compliance modulus J(t) _min of the adhesive according to the present embodiment is preferably at least 0.5MPa ^-1 as the lower limit, especially preferably at least 0.8MPa ^{-1 ,} further preferably at least 1.0MPa -1 ¹ or more is more preferable. Since the lower limit value of the minimum creep compliance modulus J(t) _min is as described above, the creep compliance modulus fluctuation value ΔlogJ(t) becomes easy to satisfy the aforementioned value. The upper limit of the minimum creep compliance modulus J(t) _min is not particularly limited, usually below 5.0MPa ^-1 is preferred, especially below 4.5MPa ^-1 , further preferably below 4.0MPa ^-1 good.

Furthermore, the maximum creep compliance modulus J(t) _max of the adhesive of this embodiment is preferably set at 1000 MPa ^-1 or less, especially 800 MPa ^-1 or less, and further preferably 500 MPa ^-1 as the upper limit. Below is better, and below 120MPa ^-1 is the best. Since the upper limit value of the maximum creep compliance modulus J(t) _max is as described above, the creep compliance modulus fluctuation value ΔlogJ(t) becomes easy to satisfy the aforementioned value. The lower limit of the maximum creep compliance modulus J(t) _max is not particularly limited, and it is usually preferably above 10MPa ^-1 , especially preferably above 15MPa ^-1 , and more preferably above 20MPa ^-1 .

On the other hand, the loss tangent (tanδ) at 25°C of the adhesive according to the present embodiment is preferably at least 0.328, particularly preferably at least 0.45, as the lower limit value from the viewpoint of the effect of suppressing interfacial peeling. , and more preferably 0.55 or more. Furthermore, from the viewpoint of maintaining the shape of the adhesive layer, the upper limit of the loss tangent (tan δ) is preferably 0.85 or less, particularly preferably 0.75 or less, further preferably 0.65 or less.

The type of the adhesive according to this embodiment is not particularly limited as long as it satisfies the above physical properties, and may be, for example, an acrylic adhesive, a polyester adhesive, a polyurethane adhesive, a rubber adhesive, silicone Any of ketone-based adhesives, etc. Furthermore, the above-mentioned adhesive may be any of emulsion type, solvent type, or solvent-free type, and may also be of any type of crosslinking type or non-crosslinking type. Among them, an acrylic adhesive that easily satisfies the aforementioned physical properties and has excellent adhesive properties, optical properties, and the like is preferable.

Furthermore, the acrylic adhesive may have active energy ray curability or active energy ray non-curability, may have thermal crosslinkability or non-crosslinkability, or may have a combination of the foregoing, and In order to obtain good flexibility, it is preferable to have active energy ray non-curability. As the active energy ray non-curable acrylic adhesive, a crosslinking type is particularly preferable, and a heat crosslinking type is further more preferable.

The adhesive according to this embodiment is particularly preferably an adhesive composition (hereinafter sometimes referred to as "adhesive composition P") containing a (meth)acrylate polymer (A) and a crosslinking agent (B). Crosslink the resulting adhesive. Such an adhesive can easily satisfy the above-mentioned physical properties, and can obtain good adhesive force and predetermined cohesive force, so it has excellent durability. In addition, in this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, "polymer" also includes the concept of "copolymer".

(1) Components of the adhesive composition P (1-1) (meth)acrylate polymer (A) The (meth)acrylate polymer (A) preferably contains an alkyl (meth)acrylate and a monomer having a reactive functional group in the molecule (a monomer containing a reactive functional group) monomeric unit of a substance.

Since (meth)acrylate polymer (A) contains an alkyl (meth)acrylate as a monomer unit which comprises this polymer, it can produce favorable adhesiveness. As the alkyl (meth)acrylate, an alkyl (meth)acrylate having an alkyl group having 1 to 20 carbon atoms is preferable. The alkyl group may be linear or branched, and may have a cyclic structure.

Alkyl (meth)acrylates having 1 to 20 carbon atoms as the alkyl group, those having a glass transition temperature (Tg) as a homopolymer (homopolymer) of -40°C or lower (hereinafter sometimes referred to as "" Low Tg alkyl acrylate (alkyl acrylate) is preferred. By including such a low Tg alkyl acrylate as a constituent monomer unit, the flexibility of the adhesive obtained can be improved.

Examples of low Tg alkyl acrylates include, for example, n-butyl acrylate (Tg is -55°C), n-octyl acrylate (Tg is -65°C), isooctyl acrylate (Tg is -58°C), ), 2-ethylhexyl acrylate (Tg is -70°C), isononyl acrylate (Tg is -58°C), isodecyl acrylate (Tg is -60°C), isodecyl methacrylate (Tg is -60°C), isodecyl methacrylate (Tg is -58°C), -41°C), n-dodecyl methacrylate (Tg is -65°C), tridecyl acrylate (Tg is -55°C), tridecyl methacrylate (Tg is -40°C )Wait. Among them, from the viewpoint of more effectively improving flexibility, as the low-Tg alkyl acrylate, the Tg of the homopolymer is preferably -45°C or lower, and particularly preferably -50°C or lower. Specifically, n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferred. These materials may be used alone or in combination of two or more.

In the (meth)acrylate polymer (A), as a monomer unit constituting the polymer, the lower limit value of the low Tg alkyl acrylate is preferably 50% by mass or more, particularly 55% by mass. The above is preferable, and it is more preferable to contain 60 mass % or more. The glass transition temperature (Tg) of a (meth)acrylate polymer (A) can be easily set in the said range by containing 50 mass % or more of the said low Tg alkylacrylate.

On the other hand, in the (meth)acrylate polymer (A), as a monomer unit constituting the polymer, the upper limit value of the above-mentioned low Tg alkyl acrylate is preferably 99.9% by mass or less, especially It is preferably at most 99% by mass, more preferably at most 98% by mass. By including 99.9% by mass or less of the aforementioned low-Tg alkyl acrylate, an appropriate amount of other monomer components (especially reactive functional group-containing monomers) can be introduced into the (meth)acrylate polymer (A).

In addition, the alkyl (meth)acrylate having 1 to 20 carbon atoms in the alkyl group may contain a monomer having a glass transition temperature (Tg) exceeding 0°C as a homopolymer (hereinafter sometimes called "high Tg alkyl acrylate"). By including such a high Tg alkyl acrylate as a constituent monomer unit, the creep compliance modulus variation value of the obtained adhesive may easily satisfy the above value.

Furthermore, the alkyl (meth)acrylate having 1 to 20 carbon atoms as the alkyl group is preferably used in combination of a low Tg alkyl acrylate and a high Tg alkyl acrylate. Thereby, the variation value of the creep compliance modulus and the loss tangent of the obtained adhesive become easy to satisfy the above-mentioned values.

When the (meth)acrylate polymer (A) contains the above-mentioned high Tg alkyl acrylate as a monomer unit constituting the polymer, its content is preferably 5% by mass or more, especially 10% by mass. The above is preferable, and more preferably 15% by mass or more. Furthermore, the content is preferably not more than 30% by mass, particularly preferably not more than 25% by mass, and more preferably not more than 20% by mass.

Examples of the above-mentioned high Tg alkyl acrylates include methyl acrylate (Tg: 10°C), methyl methacrylate (Tg: 105°C), ethyl methacrylate (Tg: 65°C), methyl N-butyl acrylate (Tg is 20°C), isobutyl methacrylate (Tg is 48°C), tertiary butyl methacrylate (Tg is 107°C), n-octadecyl acrylate (Tg is 30°C) ℃), n-octadecyl methacrylate (Tg is 38 ℃), cyclohexyl acrylate (Tg is 15 ℃), cyclohexyl methacrylate (Tg is 66 ℃), benzyl methacrylate (Tg is 54°C), isobornyl acrylate (Tg is 94°C), isobornyl methacrylate (Tg is 180°C), propane Adamantyl acrylate (Tg: 115°C), adamantyl methacrylate (Tg: 141°C), morpholine acrylate (Tg: 145°C), etc. Among them, methyl acrylate, methyl methacrylate, and isobornyl acrylate are preferable from the viewpoint of cohesion. These materials may be used alone or in combination of two or more.

In addition, in the case of using a low Tg alkyl acrylate and a high Tg alkyl acrylate in combination as an alkyl (meth)acrylate having 1 to 20 carbon atoms in the alkyl group, the (meth)acrylate In the polymer (A), the upper limit of the low Tg alkyl acrylate as a monomer unit constituting the polymer is preferably 85% by mass or less, particularly preferably 75% by mass or less, and further preferably 75% by mass or less. It is more preferable to contain 65 mass % or less. Thereby, the variation value of the creep compliance modulus and the loss tangent of the obtained adhesive become easy to satisfy the above-mentioned values.

The (meth)acrylate polymer (A) contains a reactive functional group-containing monomer as a monomer unit constituting the polymer, and through the reactive functional group derived from the reactive functional group-containing monomer group, react with the cross-linking agent (B) described later, thereby forming a cross-linking structure (three-dimensional network structure), and then obtaining an adhesive with the desired cohesion.

(Meth)acrylate polymer (A), as the reactive functional group-containing monomer contained in the monomer unit constituting the polymer, preferably, a monomer having a hydroxyl group in the molecule (a hydroxyl-containing monomer body), monomers with carboxyl groups in the molecule (carboxyl-containing monomers), monomers with amine groups in the molecule (amine-containing monomers), etc. 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, hydroxyl-containing monomers and carboxyl-containing monomers are preferred, especially hydroxyl-containing monomers. Since the hydroxyl-containing monomer has a relatively low glass transition temperature (Tg) as a homopolymer, the obtained (meth)acrylate polymer (A) is easy to maintain high flexibility, while the carboxyl-containing monomer can Improve the adhesive force of the (meth)acrylate polymer (A).

Examples of hydroxyl-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, (meth) Hydroxyalkyl (meth)acrylates, such as 2-hydroxybutyl acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc. Among them, from the viewpoint of the flexibility of the obtained (meth)acrylate polymer (A), 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate are used as good. These materials may be used alone or in combination of two or more.

Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among them, acrylic acid is preferable from the viewpoint of the adhesive force of the obtained (meth)acrylate polymer (A). These materials may be used alone or in combination of two or more.

When the (meth)acrylate polymer (A) contains a hydroxyl-containing monomer as a monomer unit constituting the polymer, the content of the hydroxyl-containing monomer is preferably 0.1% by mass or more, particularly It is preferable to contain 0.3 mass % or more. Furthermore, the content of the hydroxyl group-containing monomer is preferably not more than 30% by mass, particularly preferably not more than 25% by mass, and more preferably not more than 20% by mass. On the other hand, when the (meth)acrylate polymer (A) contains a carboxyl group-containing monomer as a monomer unit constituting the polymer, the content of the carboxyl group-containing monomer is preferably 0.5% by mass or more. , especially preferably 1% by mass or more. Furthermore, the content of the carboxyl group-containing monomer is preferably not more than 10% by mass, particularly preferably not more than 7% by mass, and more preferably not more than 5% by mass. By the contents of hydroxyl-containing monomers and carboxyl-containing monomers as described above, the obtained (meth)acrylate polymer (A) has better flexibility and adhesiveness, and the obtained The adhesive layer achieves a higher degree of relaxation effect on the bending state of the repeatedly bending device.

In addition, when the (meth)acrylate polymer (A) contains only a hydroxyl group-containing monomer as a reactive functional group-containing monomer constituting the monomer unit of the polymer, the content thereof is 1% by mass or more. Preferably, it is more than 3% by mass, particularly preferably at least 5% by mass, more preferably at least 10% by mass, and most preferably at least 15% by mass.

The (meth)acrylate polymer (A) may contain a nitrogen atom-containing monomer as a monomer unit constituting the polymer. As monomers containing nitrogen atoms, monomers having amine groups, monomers having amide groups, monomers having nitrogen-containing heterocycles, etc. can be listed, among which monomers having nitrogen-containing heterocycles are preferred. .

As a monomer having a nitrogen-containing heterocycle, for example, N-(meth)acryloyl morpholine (N-(meth)acryloyl morpholine), N-vinyl-2-pyrrolidone (N-vinyl- 2-pyrrolidone), N-(meth)acryloyl pyrrolidone (N-(meth)acryloyl pyrrolidone), N-(meth)acryloyl piperidine (N-(meth)acryloyl piperidine), N-(meth)acryloyl piperidine Base) acryloylpyrrolidine (N-(meth)acryloylpyrrolidine), N-(meth)acryloyl aziridine (N-(meth)acryloyl aziridine), (meth)acryloyl aziridine ethyl ester (aziridinyl ethyl (meth)acrylate), 2-vinylpyridine (2-vinylpyridine), 4-vinylpyridine, 2-vinylpyrazine (2-(vinylpyrazine)), 1-vinyl imidazole (1-vinyl imidazole) , N-vinyl carbazole (N-vinyl carbazole), N-vinyl phthalimide (N-vinylphthalimide), etc. Among them, N-(meth)acrylamide can exert more excellent adhesion Morpholine is preferred, and N-acryloylmorpholine is particularly preferred. These materials may be used alone or in combination of two or more.

In the case where the (meth)acrylate polymer (A) includes a nitrogen atom-containing monomer as a monomer unit constituting the polymer, the content of the nitrogen atom-containing monomer is preferably 1% by mass or more, particularly It is preferable to contain 3 mass % or more. Furthermore, the content of the nitrogen atom-containing monomer is preferably not more than 20% by mass, particularly preferably not more than 15% by mass, and more preferably not more than 10% by mass.

The (meth)acrylate polymer (A) may also contain other monomers as monomer units constituting the polymer, if necessary. As other monomers, monomers not containing reactive functional groups are preferred in order not to interfere with the aforementioned effects of reactive functional group-containing monomers. Examples of the aforementioned monomers include alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, vinyl acetate, Styrene etc. These materials may be used alone or in combination of two or more.

The polymerization form of the (meth)acrylate polymer (A) may be a random (random) copolymer or a block (block) copolymer.

The lower limit of the weight average molecular weight of the (meth)acrylate polymer (A) is preferably at least 100,000, particularly preferably at least 300,000, and more preferably at least 500,000. When the lower limit value of the weight average molecular weight of a (meth)acrylate polymer (A) is as mentioned above, the durability of an adhesive agent will become more excellent. In addition, in this specification, a weight average molecular weight is a standard polystyrene conversion value measured by the gel permeation chromatography (GPC) method.

In addition, the upper limit of the weight average molecular weight of the (meth)acrylate polymer (A) is preferably 1.5 million or less, particularly preferably 1.2 million or less, further preferably 1 million or less. When the upper limit value of the weight average molecular weight of a (meth)acrylate polymer (A) is as above-mentioned, the flexibility and adhesive force of the adhesive agent obtained will become more excellent.

In the adhesive composition P, (meth)acrylate polymer (A) may be used individually by 1 type, and may use it in combination of 2 or more types.

(1-2) Cross-linking agent (B) The crosslinking agent (B), by heating the adhesive composition P containing the crosslinking agent (B) as a trigger (trigger), crosslinks the (meth)acrylate polymer (A) to form a three-dimensional grid. Thereby, the cohesive force of the obtained adhesive improves, and an adhesive layer becomes excellent in durability.

As the crosslinking agent (B), any one can react with the reactive group of the (meth)acrylate polymer (A), for example, isocyanate crosslinking agent, epoxy Crosslinking agent based on amine, crosslinking agent based on amine, crosslinking agent based on melamine, crosslinking agent based on aziridine, crosslinking agent based on hydrazine, crosslinking agent based on aldehyde, crosslinking agent based on oxazoline Crosslinking agent, metal alkoxide type crosslinking agent, metal chelate type crosslinking agent, metal salt type crosslinking agent, ammonium salt type crosslinking agent, etc. Among the above, it is preferable to use an isocyanate having excellent reactivity with a monomer having a reactive functional group, especially a monomer having a hydroxyl group, which is a monomer unit constituting the (meth)acrylate polymer (A). Department of cross-linking agent. In addition, as the crosslinking agent (B), one type may be used alone, or two or more types may be used in combination.

The isocyanate crosslinking agent contains at least a polyisocyanate (polyisocyanate) compound. Examples of the polyvalent isocyanate compound include aromatic polyvalent isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, and hexamethylene diisocyanate. Aliphatic polyvalent isocyanate such as hexamethylene diisocyanate, isophorone diisocyanate (isophorone diisocyanate), alicyclic polyvalent isocyanate such as hydrogenated diphenylmethane diisocyanate, etc., and the above-mentioned biuret (biuret) , or isocyanurate (isocyanurate) body, as well as products-adducts reacted with low-molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil ( adduct) and so on. Among them, from the viewpoint of reactivity with hydroxyl groups, trimethylolpropane-modified aromatic polyvalent isocyanate, especially trimethylolpropane-modified toluene diisocyanate and trimethylolpropane-modified Xylyl diisocyanate is preferred.

The content of the crosslinking agent (B) in the adhesive composition P is preferably at least 0.1 parts by mass, particularly at least 0.4 parts by mass, based on 100 parts by mass of the (meth)acrylate polymer (A). Preferably, more preferably at least 1.0 parts by mass. Furthermore, the content is preferably not more than 10 parts by mass, particularly preferably not more than 8 parts by mass, and more preferably not more than 5 parts by mass. When the content of the crosslinking agent (B) is within the above range, the obtained adhesive becomes to have a suitable cohesive force, and the obtained adhesive layer can achieve a higher degree of bending state relaxation effect of the repeatedly bending device.

(1-3) Various additives If necessary, various additives commonly used in acrylic adhesives, such as silane coupling agents, ultraviolet absorbers, antistatic agents, tackifiers, antioxidants, light stabilizers, Softeners, fillers, refractive index modifiers, etc. In addition, a polymerization solvent or a diluting solvent which will be described later is not contained in the additives constituting the adhesive composition P.

(2) Preparation of Adhesive Composition P The (meth)acrylate polymer (A) is prepared, and the obtained (meth)acrylate polymer (A) is mixed with the crosslinking agent (B), and additives may be added as needed, thereby producing Adhesive composition P.

The (meth)acrylate polymer (A) can be produced by superposing|polymerizing the mixture of the monomer which comprises a polymer by a general radical (radical) polymerization method. It is preferable to perform superposition|polymerization of a (meth)acrylate polymer (A) by the solution polymerization method using a polymerization initiator as needed. 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 (azo) compounds, organic peroxides, and the like, 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( Cyclohexane (1-carbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxy ylvaleronitrile), 2,2'-azobis(2-methylpropionate) dimethyl ester, 2,4'-azobis(4-cyanovaleric acid), 2,2'-azobis (2-hydroxymethylpropionitrile), 2,2'-azobis[2-(2-imidazolin-2-yl)propane], etc.

Examples of organic peroxides include benzoyl peroxide, tert-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate ester, bis(2-ethoxyethyl) peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-butyl peroxypivalate, (3,5,5-trimethylhexyl base) peroxide, diacryl peroxide, diacetyl peroxide, etc.

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

When the (meth)acrylate polymer (A) is obtained, the crosslinking agent (B) and additives and diluting solvents are added to the solution of the (meth)acrylate polymer (A) according to the Mixing and further obtaining the adhesive composition P (coating solution) diluted with a solvent.

In addition, in the case of using any one of the above-mentioned components in solid form, or in the case where precipitation occurs when mixed with other components in an undiluted state, it is also possible to dissolve or dilute this component alone in a diluent solvent in advance, and then mixed with the other ingredients mentioned above.

As the diluting solvent, for example, aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated dichloromethane, 1,2-dichloroethane, etc. Alcohols such as hydrocarbons, methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone , esters such as ethyl acetate and butyl acetate, cellosolve solvents such as ethyl cellosolve, and the like.

The concentration and viscosity of the coating solution prepared in the above manner are not particularly limited as long as they are within the range where coating is possible, and can be appropriately selected depending on the situation. For example, it is diluted so that the concentration of the adhesive composition P may be 10 to 60% by mass. In addition, when obtaining a coating solution, addition of a diluent solvent etc. is not an essential requirement, If the adhesive composition P has the viscosity etc. which can apply|coat, it is not necessary to add a diluent solvent. In this case, the adhesive composition P is a coating solution in which the polymerization solvent of the (meth)acrylate polymer (A) is directly used as a dilution solvent.

(3) Preparation of adhesive The adhesive according to the present embodiment is preferably an adhesive obtained by crosslinking the adhesive composition P. The crosslinking of the adhesive composition P can usually be performed by heat treatment. In addition, this heat treatment can also be used as a drying treatment at the same time to volatilize the dilution solvent or the like from the coating film of the adhesive composition P applied on the desired object.

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

After the heat treatment, a curing period of about 1 to 2 weeks at normal temperature (for example, 23° C., 50% RH) may be provided as needed. In the case where this curing period is required, the adhesive is formed after the curing period passes, and in the case where the curing period is not required, the adhesive is formed after the heat treatment is completed.

Through the above-mentioned heat treatment (and curing), the (meth)acrylate polymer (A) is fully cross-linked by the cross-linking agent (B), thereby forming a cross-linked structure to obtain an adhesive. The adhesive may have a predetermined cohesion.

(4) Physical properties of the adhesive The lower limit of the storage modulus (G') at 25° C. of the adhesive according to the present embodiment is preferably 0.01 MPa or more. Furthermore, the upper limit of the storage modulus (G') is preferably not more than 0.25 MPa, especially not more than 0.20 MPa.

Furthermore, the lower limit of the loss modulus (G'') at 25° C. of the adhesive according to the present embodiment is preferably 0.005 MPa or more, especially 0.01 MPa or more. Furthermore, the upper limit of the loss modulus (G'') is preferably not more than 0.1 MPa, especially not more than 0.08 MPa.

When the storage modulus (G') and loss modulus (G'') of the adhesive according to the present embodiment are within the above-mentioned ranges, the adhesive force to the flexible member becomes good, and the durability of the repeated bending device can be improved. sex. In addition, the measurement methods of the storage modulus (G') and the loss modulus (G'') are as shown in the test examples described later.

[adhesive sheet] According to the adhesive sheet according to this embodiment, the adhesive is used for bonding one flexible member constituting the repeated bending device to the other flexible member, and the adhesive layer is formed of the aforementioned adhesive.

As an example of the adhesive sheet according to this embodiment, its specific structure is shown in FIG. 1 . As shown in FIG. 1 , according to an adhesive sheet 1 according to one embodiment, the two release sheets 12a and 12b are bonded by the two release sheets 12a and 12b so as to contact the release surfaces of the two release sheets 12a and 12b. The sandwiched adhesive layer 11 constitutes. In addition, the release surface of the release sheet in this specification refers to the surface having releasability in the release sheet, and includes a surface subjected to a release treatment and a surface that exhibits releasability even without a release treatment.

(1) Components (1-1) Adhesive layer The adhesive layer 11 is composed of the adhesive according to the aforementioned embodiments, preferably an adhesive obtained by crosslinking the adhesive composition P.

The thickness of the adhesive layer 11 in the adhesive sheet 1 according to the present embodiment (value measured according to JIS K 7130) is preferably at least 2 μm, particularly preferably at least 5 μm, and further preferably at least 10 μm. The above is better. When the lower limit of the thickness of the adhesive layer 11 is the above value, it is easy to exhibit a desired adhesive force, and it is possible to effectively suppress problems such as floating and peeling during repeated bending. Furthermore, the upper limit of the thickness of the adhesive layer 11 is preferably 150 μm or less, more preferably 100 μm or less, particularly preferably 70 μm or less, and more preferably 50 μm or less. When the upper limit of the thickness of the adhesive layer 11 is the above value, it is possible to suppress the problem of the adhesive or components constituting the adhesive bleeding from the adhesive layer due to repeated bending. In addition, the adhesive layer 11 may be formed as a single layer, or may be laminated and formed as a multilayer.

(1-2) Peeling sheet The release sheets 12a and 12b protect the adhesive layer 11 before the adhesive sheet 1 is used, and are peeled when the adhesive sheet 1 (adhesive layer 11) is used. In the adhesive sheet 1 according to this embodiment, one or both of the release sheets 12a and 12b are not necessarily required.

As the release sheets 12a and 12b, for example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, poly Ethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene-vinyl acetate film, ionomer resin film, Ethylene-(meth)acrylic acid copolymer film, ethylene-(meth)acrylate copolymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film, etc. Furthermore, crosslinked films of the above materials may also be used. Furthermore, laminated films of the above materials can also be used.

The release surfaces of the release sheets 12a and 12b (particularly, the surfaces in contact with the adhesive layer 11) are preferably subjected to release 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. In addition, among 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 is a light release type release sheet with 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) Manufacture of adhesive sheets As a manufacturing example of the adhesive sheet 1, the case where the said adhesive composition P is used is demonstrated. A coating solution of the adhesive composition P is applied to the peeling surface of one peeling sheet 12a (or 12b), heat-treated so that the adhesive composition P is thermally crosslinked to form a coating layer, and the other sheet is peeled off. The release side of the sheet 12b (or 12a) is superimposed on this coating layer. When a curing period is required, the adhesive layer 11 is formed by placing the coating layer for a period of curing time, and when a curing period is not required, the coating layer is directly used as the adhesive layer 11 . Thereby, the above-mentioned adhesive sheet 1 can be obtained. The conditions for heat treatment and curing are as described above.

As another production example of the adhesive sheet 1, a coating solution of the adhesive composition P is applied to the release surface of one release sheet 12a, heat-treated to thermally crosslink the adhesive composition P to form a coating layer, and then A coating layer-attached release sheet 12a is formed. Furthermore, the coating solution of the above-mentioned adhesive composition P is coated on the release surface of the other release sheet 12b, and heat treatment is performed to thermally crosslink the adhesive composition P to form a coating layer, and then form an attached coating layer. Release sheet 12b for the cloth layer. Next, the release sheet 12a with a coating layer and the release sheet 12b with a coating layer are bonded together so that both coating layers may contact each other. In the case where a curing period is required, the adhesive layer 11 is formed by placing the above-mentioned laminated coating layer for a period of curing period, and when the curing period is not required, the above-mentioned laminated coating layer is directly used as the adhesive layer 11 . Thereby, the above-mentioned adhesive sheet 1 can be obtained. According to this manufacturing example, even in the case where the adhesive layer 11 is relatively thick, the adhesive layer 11 can be stably manufactured.

As the coating method of the coating solution of the above-mentioned adhesive composition P, for example, bar coating (bar coating) method, knife coating (knife coating) method, roll coating (roll coating) method, sheet coating (blade coating) method can be used. coating) coating method, die coating (die coating) method, gravure coating (gravure coating) method, etc.

(3) Adhesion The lower limit of the adhesive force of the adhesive sheet 1 according to the present embodiment to the soda-lime glass is preferably 5.1 N/25 mm or more, especially 5.5 N/25 mm or more, and further preferably 6.0 N/25 mm or more. better. When the adhesive force of the adhesive sheet 1 is 5.1 N/25 mm or more, the effect of suppressing interfacial peeling becomes more excellent. On the other hand, the upper limit of the above-mentioned adhesive force is not particularly limited, but it is usually preferably below 25N/25mm, more preferably below 20N/25mm, and most preferably below 15N/25mm. In addition, the above-mentioned adhesive force is basically the adhesive force measured according to the 180-degree peeling method of JIS Z 0237:2009, and the specific test method is shown in the test example described later.

[Repeated bending laminated components] As shown in FIG. 2, the repeatedly bending laminated member 2 according to this embodiment includes a first flexible member 21 (one flexible member), a second flexible member 22 (other flexible members), and between them and bond the first flexible member 21 and the second flexible member 22 to each other.

The adhesive layer 11 in the above-mentioned repeated bending laminated member 2 is the adhesive layer 11 of the above-mentioned adhesive sheet 1 .

The repetitively bending laminated member 2 itself is a repetitive bending device, or is a member constituting a part of the repetitive bending device. The repeatedly bending device is preferably a display that can be repeatedly bent (including folded), but is not limited thereto. As such a repeating bending device, for example, organic electroluminescence (organic EL) display, electrophoretic display (electronic paper), flexible printed circuit board (flexible printed circuit board), using a plastic film substrate (film) as The liquid crystal display, foldable display, etc. of the substrate may also be a touch panel.

The first flexible member 21 and the second flexible member 22 are members that can be repeatedly bent (including folded), and examples thereof include a cover film, a barrier film, a polarizing film, Polarizer, retardation film, viewing angle compensation film, brightness enhancement film, contrast enhancement film, diffusion film, semi-transmissive reflection film, electrode film, transparent conductive film, metal mesh, film sensor (film sensor), liquid crystal polymer film, Light-emitting polymer film, thin film liquid crystal module (module), organic EL module (organic EL film), electronic paper module (film electronic paper), etc.

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 thin film liquid crystal Modules, organic EL modules (organic EL films), and electronic paper modules (film-like electronic paper) are preferred.

The Young's moduli of the first flexible member 21 and the second flexible member 22 are preferably 0.1 to 10 GPa, particularly preferably 0.5 to 7 GPa, and more preferably 1.0 to 5 GPa. Since the Young's modulus of the first flexible member 21 and the second flexible member 22 is within the above-mentioned range, it becomes easy to repeatedly bend each flexible member.

The thicknesses of the first flexible member 21 and the second flexible member 22 are preferably 5 to 3000 μm, particularly preferably 10 to 1000 μm, and more preferably 10 to 500 μm. Since the thicknesses of the first flexible member 21 and the second flexible member 22 are within the above-mentioned range, it becomes easy to repeatedly bend each flexible member.

When manufacturing the above-mentioned repeatedly bending laminated member 2, as an example, one release sheet 12a of the adhesive sheet 1 can be peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1 can be bonded to the first flexible member 21 side. s surface.

After that, the other peeling sheet 12b is peeled off from the adhesive layer 11 in the adhesive sheet 1, and the exposed adhesive layer 11 in the adhesive sheet 1 is bonded to the second flexible member 22, and then the repeated bending laminated member 2 is obtained. . In addition, 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 repeated bending device according to the present embodiment is a repeated bending device provided with the above-mentioned repeated bending laminated member 2, and may be composed of only the repeated bending laminated member 2, or may be composed of one or more repeated bending laminated members 2 and composed of other flexible components. When one repeatedly bending laminated member 2 is laminated with another repeatedly bending member 2, or when the repeatedly bending laminated member 2 is laminated with another flexible member, it is preferable to laminate through the adhesive layer 11 of the aforementioned adhesive sheet 1.

According to the repeated bending device of this embodiment, since the adhesive layer is formed of the aforementioned adhesive, it is in a state of being in a state of repeated bending (for example, 30,000 times) and for a long time (for example, at least 24 hours or more). In the case of the bent state, after the release from the bent state, it is possible to suppress the repeated bending device from being fixed in the greatly bent state, and to alleviate the influence of repeated bending and the influence of being in the bent state. The effect of relieving the bending state of such a repeated bending device can be evaluated by, for example, the amount of static bending deformation in a static bending test and the amount of dynamic bending deformation in a dynamic bending test.

In the static bending test, a laminate consisting of two polyethylene terephthalate films (thickness: 12μm) sandwiching an adhesive layer (thickness: 12μm) was prepared as a test piece with a size of 200mm×50mm . As shown in FIG. 3 , under the environment of 23° C. and 50% RH, the test piece S was held in a bent state between holding plates P composed of two glass plates standing upright for 24 hours. At this time, the distance between the two holding plates P is set to 6 mm (the bending diameter of the test piece S: 6 mmψ), the approximate central part of the long side (200 mm) of the test piece S is used as the curved part, and the two sides of the test piece S are bent. The test piece S was held so that the short side (50 mm) was located on the upper side. After performing this static bending test, the test piece S was taken out from between the two holding plates P, and as shown in FIG. Next, the height h from the surface of the flat plate to the vertex of the bent portion (deformed portion) was measured as the amount of static bending deformation when the test was finished, 30 minutes after the test, and 24 hours after the test. The amount of static bending deformation can be used as the test result of the static bending test, and the effect of relaxing the bending state can be evaluated based on the amount of static bending deformation.

The amount of static bending deformation obtained by the static bending test at the end of the test is preferably less than 3 mm, especially preferably less than 1 mm, and more preferably less than 0.5 mm. In addition, after 30 minutes after the test, it is preferably 1 mm or less, particularly preferably 0.5 mm or less. Furthermore, after 24 hours after the test, it is preferably 0.5 mm or less, especially 0.3 mm or less. In addition, the lower limit of any of the above static bending deformations is preferably 0 mm.

On the other hand, in the dynamic bending test, a laminate composed of two polyethylene terephthalate films (thickness: 12 μm) sandwiching an adhesive layer (thickness: 12 μm) was made into a laminate with a size of 150 mm× 50mm test piece. As shown in FIG. 5 , this test piece S was held between two holding plates P of a planar non-load U-shaped tensile tester in an environment of 23° C. and 50% RH. One of the two holding plates P maintains a parallel relationship with the other holding plate P, and can reciprocate to approach and separate from the other holding plate P. As shown in FIG. The distance between the two holding plates P was set to vary from 86 mm to 6 mm (bending diameter of test piece S: 6 mmψ, reciprocating path length: 80 mm). The test piece S was fixed to the holding plate P so that the substantially central portion of the long side (150 mm) of the test piece S was a curved portion and the two short sides (50 mm) of the test piece S were located on the upper side. In this state, the test piece S was bent 30,000 times at a bending speed of 30 rpm (the reciprocating speed of the holding plate P). After performing this dynamic bending test, the test piece S was taken out from between the two holding plates P, and as shown in FIG. Next, the height h from the surface of the flat plate to the vertex of the bent portion (deformed portion) was measured as the amount of dynamic bending deformation when the test was finished and 24 hours after the test. This amount of dynamic bending deformation can be used as the test result of the dynamic bending test, and the bending state relaxation effect can be evaluated based on the amount of dynamic bending deformation.

The amount of dynamic bending deformation obtained by the dynamic bending test is preferably less than 3 mm, especially preferably less than 1 mm, and more preferably less than 0.5 mm at the end of the test. Furthermore, after 24 hours after the test, it is preferably 1 mm or less, especially 0.5 mm or less. In addition, the lower limit of any of the above-mentioned dynamic bending deformations is preferably 0 mm.

The embodiments described above are described for easy understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above-mentioned embodiments also covers all design changes and equivalents belonging to the technical scope of the present invention.

For example, in the adhesive sheet 1, either or both of the release sheets 12a and 12b may be omitted, and a necessary flexible member may be laminated instead of the release sheet 12a and/or the release sheet 12b. [Example]

Hereinafter, the present invention will be described more specifically through examples and the like, but the scope of the present invention is not limited to these examples and the like.

[Example 1] 1. Preparation of (meth)acrylate polymer (A) By solution polymerization, 47.8 parts by mass of 2-ethylhexyl acrylate, 47.8 parts by mass of n-butyl acrylate, 4 parts by mass of acrylic acid and 0.4 parts by mass of 2-hydroxypropyl acrylate were copolymerized to prepare (Meth)acrylate polymer (A). The molecular weight of this (meth)acrylate polymer (A) was measured by the method described later, and it was found that the weight average molecular weight (Mw) was 600,000.

2. Preparation of Adhesive Composition 100 parts by mass (calculated by solid content, the same below) of the (meth)acrylate polymer (A) obtained in the above step 1, and 3.75 parts by mass of trihydroxy Methylpropane-modified toluene diisocyanate (manufactured by Toyo Chemical Corporation, product name "BHS 8515") was mixed with each other and fully stirred, and diluted with toluene to obtain a coating solution of an adhesive composition ( Solid content concentration: 30.0% by mass).

3. Manufacture of adhesive sheet The obtained coating solution of the adhesive composition was applied to one surface of a polyethylene terephthalate film subjected to a release treatment using a silicone-based release agent using a comma coater. The peeling treatment surface of the obtained heavy-peeling type peeling sheet (manufactured by Lintec (Lintec), product name "SP-PET 382150"). Next, the coating layer was heat-treated at 90° C. for 1 minute to form a coating layer.

After that, the coating layer on the heavy release type release sheet obtained above and the light release type release sheet obtained by peeling one surface of the polyethylene terephthalate film with a silicone release agent (manufactured by Lintec Corporation, the product name is "SP-PET 381031"), the release treatment surface of this light-release type release sheet is attached to the coating layer in such a way that it is in contact with each other, and is kept at 23°C, 50%RH Cured for 7 days under certain conditions to form an adhesive sheet with an adhesive layer with a thickness of 12 μm, that is, to produce a structure with a heavy-release type release sheet/adhesive layer (thickness: 12 μm)/light-release type release sheet Adhesive sheet. In addition, the thickness of the adhesive layer is a value measured using a constant pressure thickness gauge (manufactured by TECLOCK, product name "PG-02") based on JIS K7130.

[Example 2] An adhesive sheet was produced in the same manner as in Example 1 except that the compounding amount of the crosslinking agent (B) was changed to 6.56 parts by mass.

[Example 3] By solution polymerization, 60 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of methyl methacrylate and 20 parts by mass of 2-hydroxyethyl acrylate were copolymerized to prepare (meth)acrylic acid Ester polymer (A). The molecular weight of this (meth)acrylate polymer (A) was measured by the method described later, and it was found that the weight average molecular weight (Mw) was 600,000.

With 100 parts by mass of the (meth)acrylate polymer (A) obtained in the above steps, and 1.88 parts by mass of the trimethylolpropane modified toluene diisocyanate (formed by Toyo Chemical Co., Ltd., the product name is "BHS 8515") mixed with each other and fully stirred, and diluted with methyl ethyl ketone (methyl ethyl ketone, MEK) to obtain a coating solution of the adhesive composition (solid content concentration : 30.0% by mass). An adhesive sheet was produced in the same manner as in Example 1 using the obtained coating solution of the adhesive composition.

[Example 4] By solution polymerization, 60 parts by mass of butyl acrylate, 20 parts by mass of methyl acrylate and 20 parts by mass of 2-hydroxyethyl acrylate were copolymerized to prepare (meth)acrylate polymer (A) . The molecular weight of this (meth)acrylate polymer (A) was measured by the method described later, and it was found that the weight average molecular weight (Mw) was 600,000.

With 100 parts by mass of the (meth)acrylate polymer (A) obtained in the above steps, and 1.88 parts by mass of the trimethylolpropane modified toluene diisocyanate (formed by Toyo Chemical Co., Ltd., product name "BHS 8515") were mixed with each other and fully stirred, and diluted with methyl ethyl ketone to obtain a coating solution of an adhesive composition (solid content concentration: 30.0% by mass). An adhesive sheet was produced in the same manner as in Example 1 using the obtained coating solution of the adhesive composition.

[Example 5] By solution polymerization, 65 parts by mass of 2-ethylhexyl acrylate, 5 parts by mass of N-acrylmorpholine, 15 parts by mass of isocamphoryl acrylate and 15 parts by mass of 2-hydroxyethyl acrylate polymerization, and then prepare (meth)acrylate polymer (A). The molecular weight of this (meth)acrylate polymer (A) was measured by the method described later, and it was found that the weight average molecular weight (Mw) was 500,000.

With 100 parts by mass of the (meth)acrylate polymer (A) obtained in the above steps, and 1.20 parts by mass of the trimethylolpropane modified toluene diisocyanate (formed by Toyo Chemical Co., Ltd., product name "BHS 8515") were mixed with each other and fully stirred, and diluted with methyl ethyl ketone to obtain a coating solution of an adhesive composition (solid content concentration: 30.0% by mass). An adhesive sheet was produced in the same manner as in Example 1 using the obtained coating solution of the adhesive composition.

[Example 6] Use the (meth)acrylate polymer (A) prepared in Example 3, and change the formulation amount of the crosslinking agent (B) to 0.47 parts by mass, except that, the rest are the same as in Example 1 way to make adhesive sheets.

[Example 7] Use the (meth)acrylate polymer (A) prepared in Example 3, and change the formulation amount of the crosslinking agent (B) to 0.94 parts by mass, except that, the rest are the same as in Example 1 way to make adhesive sheets.

[Example 8] Use the (meth)acrylate polymer (A) prepared in Example 4, and change the formulation amount of the crosslinking agent (B) to 0.47 parts by mass, except that, the rest are the same as in Example 1 way to make adhesive sheets.

[Example 9] Use the (meth)acrylate polymer (A) prepared in Example 4, and change the formulation amount of the crosslinking agent (B) to 0.94 parts by mass, except that, the rest are the same as in Example 1 way to make adhesive sheets.

[Example 10] Use the (meth)acrylate polymer (A) prepared in Example 5, and change the formulation amount of the crosslinking agent (B) to 0.60 parts by mass, except that, the rest are the same as in Example 1 way to make adhesive sheets.

[Comparative example 1] An adhesive sheet was produced in the same manner as in Example 1 except that the compounding amount of the crosslinking agent (B) was changed to 0.94 parts by mass.

[Comparative example 2] Use the (meth)acrylate polymer (A) prepared in Example 4, and change the formulation amount of the crosslinking agent (B) to 0.23 parts by mass, except that, the rest are the same as in Example 1 way to make adhesive sheets.

[Comparative example 3] Use the (meth)acrylate polymer (A) prepared in Example 5, and change the formulation amount of the crosslinking agent (B) to 0.15 parts by mass, except that, the rest are the same as in Example 1 way to make adhesive sheets.

[Comparative example 4] Use the (meth)acrylate polymer (A) prepared in Example 5, and change the formulation amount of the crosslinking agent (B) to 0.30 parts by mass, except that, the rest are the same as in Example 1 way to make adhesive sheets.

In addition, the composition of the (meth)acrylate polymer (A) and the compounding quantity of the crosslinking agent (B) in each Example and a comparative example (relative to 100 mass parts of (meth)acrylate polymer (A) ) in parts by mass) are listed in Table 1. Abbreviations in Table 1 are as follows. 2EHA: 2-Ethylhexyl Acrylate BA: n-butyl acrylate AA: Acrylic 2HPA: 2-Hydroxypropyl Acrylate MMA: methyl methacrylate HEA: 2-Hydroxyethyl Acrylate MA: methyl acrylate ACMO: N-Acryloylmorpholine IBXA: Isocamphoryl Acrylate

[Test Example 1] (Measurement of creep compliance modulus) The adhesive layer of the adhesive sheet produced in the Example and the comparative example was laminated|stacked, and the laminated body of thickness 0.5mm was formed further. A cylinder having a diameter of 8 mm (height: 0.5 mm) was punched out from the obtained laminated body of the adhesive layer, and this was used as a sample.

For the above samples, using a viscoelasticity measuring instrument (manufactured by Anton Paar, the product name is "MCR 302"), a stress of 3000 Pa is continuously applied under the following conditions, and the creep compliance modulus J (t ) (MPa ^-1 ). According to its measurement results, the value when a stress of 3000Pa is applied is defined as the minimum creep compliance modulus J(t) _min (MPa ^-1 ), and the minimum creep compliance modulus J(t) _min from the measurement to this minimum is deduced After 3757 seconds, the maximum creep compliance modulus J(t) _max (MPa ^-1 ) measured during this period. Measuring temperature: 25°C Measuring points: 1000 points (logarithmic graph)

According to the obtained minimum creep compliance modulus J(t) _min (MPa ^-1 ) and maximum creep compliance modulus J(t) _max (MPa ^-1 ), calculate the creep compliance modulus based on the following formula (I) The variation value ΔlogJ(t). The results are shown in Table 1. ΔlogJ(t) = log J(t) _max - log J(t) _min (I)

[Test Example 2] (Measurement of dynamic modulus of elasticity) The adhesive layer of the adhesive sheet produced in the Example and the comparative example was laminated|stacked, and the laminated body of thickness 0.5mm was formed further. A cylinder having a diameter of 8 mm (height: 0.5 mm) was punched out from the obtained laminated body of the adhesive layer, and this was used as a sample.

For the above sample, according to JIS K7244-1, using a viscoelasticity measuring device (manufactured by Anton Paar, product name "MCR 302"), the dynamic viscoelasticity was measured under the following conditions, and the storage mode at 25°C was observed Number (G') (MPa), loss modulus (G'') (MPa) and loss tangent (tanδ). The results are shown in Table 1. Measurement frequency: 1 Hz Measuring temperature range: -20～150℃

[Test example 3] (static bending test) In an environment of 23°C and 50% RH, the light-peeling release sheet was peeled off from the adhesive sheets produced in Examples and Comparative Examples, and the exposed adhesive layer was bonded to polyethylene terephthalate A film (manufactured by Toray, product name "S10 Lumirror", thickness: 12 μm) is on one surface. Next, the heavy-peeling type release sheet was peeled off, and the exposed adhesive layer was attached to another polyethylene terephthalate film (manufactured by Toray Corporation, product name "S10 Lumirror", thickness: 12 μm ) on one surface. Then, after pressurizing at 0.5 MPa and 50 degreeC for 20 minutes in the autoclave manufactured by Kurihara Seisakusho Co., Ltd., it left to stand under the conditions of 23 degreeC and 50%RH for 24 hours. The laminated body which consists of the obtained PET film/adhesive layer/PET film was cut into 200 mm x 50 mm, and this was used as a test piece.

As shown in FIG. 3 , the obtained test piece was held in a bent state between holding plates P (separation distance: 6 mm) composed of two glass plates standing upright in an environment of 23° C. and 50% RH for 24 hours. . After carrying out this static bending test, as shown in Fig. 4, place the test piece on the flat plate, after finishing the test, after 30 minutes after the test and after 24 hours after the test, measure the bending portion (deformation) from the surface of the flat plate The height h of the vertex of part) is used as the amount of static bending deformation. Based on the measured amount of static bending deformation, static bendability was evaluated according to the following criteria. In addition, in the test piece (Example) after a test, it was confirmed visually whether peeling occurred in the interface between the adhesive layer of a bending part, and an adherend. The results are shown in Table 1. ◎: The amount of deformation at the end of the bending test is less than 1mm 〇: The amount of deformation at the end of the bending test is more than 1 mm and less than 3 mm, and the amount of deformation after 30 minutes after the test is less than 1 mm △: The amount of deformation at the end of the bending test is more than 3 mm and less than 6 mm, the amount of deformation after 30 minutes after the test is less than 5 mm, and the amount of deformation after 24 hours after the test is less than 1 mm ×: Other than the above

[Test Example 4] (Dynamic Bending Test) The laminated body which consists of the PET film/adhesive layer/PET film obtained similarly to Experiment 3 was cut into 150 mm x 50 mm, and this was used as a test piece. As shown in Fig. 5 , both ends of the obtained test piece were fixed to two plane-shaped no-load U-shaped tensile testing machines (manufactured by Yuasa System Equipment Co., Ltd., product name "DLDMLH-FS"). Keep on board. Thereafter, the test piece was bent 30,000 times at a bending diameter of 6 mmψ, a reciprocating path length of 80 mm, and a bending speed of 30 rpm in an environment of 23° C. and 50% RH.

After performing this dynamic bending test, as shown in Fig. 4, place the test piece on a flat plate, and measure the height from the surface of the flat plate to the apex of the bent portion (deformed portion) immediately after the end of the test and 24 hours after the test. h as the amount of dynamic bending deformation. Based on the measured amount of dynamic bending deformation, dynamic bendability was evaluated according to the following criteria. In addition, in the test piece (Example) after a test, it was confirmed visually whether peeling occurred in the interface between the adhesive layer of a bending part, and an adherend. The results are shown in Table 1. ◎: The deformation at the end of the bending test is 0mm 〇: The amount of deformation at the end of the bending test is 1 mm or less, and the amount of deformation after 24 hours after the test is 0 mm △: The amount of deformation at the end of the bending test is more than 1 mm and less than 3 mm, and the amount of deformation after 24 hours after the test is less than 1 mm ×: Other than the above

[Test Example 5] (Measurement of Adhesive Force) The light-peeling release sheet was peeled off from the adhesive sheet obtained in Examples, and the exposed adhesive layer was bonded to a polyethylene terephthalate (PET) film (produced by Toyobo Corporation) with an easy-adhesive layer. Manufacture, product name "PET A 4300"), thickness: 100μm) easy-adhesive layer, and then obtain a laminate of heavy-peeling 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 peeling type release sheet was peeled from the above-mentioned laminate, and the exposed adhesive layer was attached to soda lime glass (manufactured by Nippon Plate Glass Co., Ltd.), and heated at 23° C. , 50% RH environment for 30 minutes, using a tensile tester (Tensilon manufactured by ORIENTEC), under the conditions of a peeling speed of 300mm/min and a peeling angle of 180 degrees, the adhesion of the PET film to the adhesive was measured. Adhesion (N/25mm) when the laminate of the agent layer is peeled off from the soda-lime glass. Conditions other than those described here were measured in accordance with JIS Z 0237:2009. The results are shown in Table 1.

[Table 1]

As can be seen from Table 1, the adhesive layer of the adhesive sheet of the example has an excellent bending state relaxation effect when two flexible members are bonded and repeatedly bent, and when they are bent for a long time. Furthermore, the adhesive layers of the adhesive sheets of Examples 3 and 5 to 10 also had an excellent effect of suppressing interfacial peeling. [industrial availability]

The present invention is suitable for laminating 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 components 21‧‧‧The first flexible member 22‧‧‧The second flexible member S‧‧‧test piece P‧‧‧holding plate

[ Fig. 1 ] is a cross-sectional view of an adhesive sheet according to an embodiment of the present invention. [ Fig. 2 ] is a cross-sectional view of a repeatedly bending laminated member according to an embodiment of the present invention. [ Fig. 3 ] is an explanatory diagram (side view) for explaining a static bending test. [ Fig. 4 ] is an explanatory diagram (side view) for explaining the amount of deformation of a test piece as a test result of a bending test. [ Fig. 5 ] is an explanatory diagram (side view) for explaining a dynamic bending test.

1‧‧‧adhesive sheet

11‧‧‧adhesive layer

12a, 12b‧‧‧Peeling sheet

Claims (11)

An adhesive for a repetitive bending device, which is an adhesive for a repetitive bending device for bonding one flexible member constituting the repetitive bending device to another flexible member, wherein the adhesive is measured when a stress of 3000 Pa is applied to the adhesive The obtained creep compliance modulus value is defined as the minimum creep compliance modulus J(t) _min (MPa ^-1 ), and after measuring the aforementioned minimum creep compliance modulus J(t) _min , continue to apply a stress of 3000Pa until the Up to 3757 seconds, the maximum creep compliance modulus value measured during this period is defined as the maximum creep compliance modulus J(t) _max (MPa ^-1 ), the creep compliance modulus calculated by the following formula (I) The fluctuation value △logJ(t) is 2.79 or less, △logJ(t)=logJ(t) _max -logJ(t) _min (I), and the aforementioned adhesive will contain (meth)acrylate polymer (A) and The adhesive composition of the crosslinking agent (B) crosslinks the resulting adhesive. The adhesive for repeated bending devices as described in claim 1, wherein the loss tangent (tanδ) at 25°C according to the dynamic viscoelasticity measurement method of JIS K7244-1 is not less than 0.328 and not more than 0.85. The adhesive for repetitive bending devices as described in claim 1, wherein the storage modulus (G') at 25°C is not less than 0.01 MPa and not more than 0.25 MPa. The adhesive for repeated bending devices as described in claim 1 of the patent application, wherein the loss modulus (G") at 25°C is not less than 0.005 MPa and not more than 0.1 MPa. The adhesive for repetitive bending devices as described in claim 1, wherein the (meth)acrylate polymer (A) has a weight average molecular weight of not less than 500,000 and not more than 1.5 million. The adhesive for repetitive bending devices as described in item 1 of the scope of application, wherein the (meth)acrylate polymer (A) contains an alkyl (meth)acrylic acid alkyl group having 1 to 20 carbon atoms Esters, monomers whose glass transition temperature (Tg) exceeds 0°C as homopolymers are used as monomer units constituting polymers. An adhesive sheet having a bending structure for forming a repeated bending device An adhesive sheet with an adhesive layer attached to other flexible components, wherein the aforementioned adhesive layer is formed of the adhesive for repeated bending devices as described in any one of items 1 to 6 of the patent claims. The adhesive sheet according to claim 7, wherein the adhesive sheet has two release sheets, and the adhesive layer is sandwiched by the release sheets so as to contact the release surfaces of the two release sheets. A repeatedly bending laminated member, which is a repeatedly bending laminated member comprising one flexible member and other flexible members constituting a repetitive bending device, and an adhesive layer bonding the one flexible member and the other flexible member to each other, Wherein the aforementioned adhesive layer is the adhesive layer of the adhesive sheet as described in item 7 of the scope of application. The repeated bending laminated member according to claim 9 of the patent application, wherein at least one of the aforementioned one flexible member and the aforementioned other flexible member is a display element. A repetitive bending device, which is provided with the repetitive bending laminated member described in item 9 of the scope of the patent application.

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