TW202239925A - Optical adhesive sheet for foldable device - Google Patents

Abstract

An optical adhesive sheet (S), which serves as an optical adhesive agent sheet for a foldable device according to the present invention, has an adhesive agent layer (10). The adhesive agent layer (10) has a shear storage elastic modulus of 20-50 kPa at 25 DEG C. After being affixed to an adherend and then left to stand for a two-minute first standing at 25 DEG C, the adhesive agent layer (10) has a first adhesive strength Xa to the adherend at 25 DEG C. Furthermore, after being affixed to the adherend, subjected to a heating and pressurization treatment at 50 DEG C and 0.5 MPa for 15 minutes, and then left to stand for a 72-hour second standing at 25 DEG C, the adhesive agent layer (10) has a second adhesive strength Xb to the adherend at 25 DEG C. The first adhesive strength Xa and the second adhesive strength Xb satisfy the relationship 2.2 ≤ Xb/Xa ≤ 5.

Description

Optical adhesive sheet for foldable devices

The invention relates to an optical adhesive sheet for a foldable device.

The display panel has, for example, a laminated structure including a pixel panel, a touch panel, a polarizer, and a cover film. In the manufacturing process of such a display panel, in order to join the elements included in the laminated structure, for example, a transparent adhesive sheet (optical adhesive sheet) is used. On the other hand, for example, for smartphone applications and tablet terminal applications, the development of display panels that can be repeatedly bent (foldable) has been carried out. In the foldable display panel, each element in the laminated structure is made to be able to be bent repeatedly, and an optical adhesive sheet is used for the connection between the elements. The optical adhesive sheet for foldable devices, such as a foldable display panel, is described, for example in the following patent document 1. [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2018-111754

[Problem to be solved by the invention]

For optical adhesive sheets, reworkability related to the operation of attaching to the adherend is required. Specifically, when problems occur when attaching the optical adhesive sheet to the adherend (position shift of the adhesive sheet on the adherend, etc.), the optical adhesive sheet is required to have Appropriate peeling and light peeling, so that the optical adhesive sheet can be used again for lamination. When a foldable device includes high-priced components such as polarizing plates, especially from the viewpoint of avoiding manufacturing loss due to poor bonding, the requirement for reworkability of the optical adhesive sheet is strong.

Moreover, the optical adhesive sheet in a foldable device is also required to exhibit sufficient adhesion reliability to an adherend. However, at the bent portion of the device, peeling of the optical adhesive sheet from the adherend easily occurred previously. The reason for this is that when the device is bent, stress such as shear stress locally acts on the bent portion of the optical adhesive sheet. The occurrence of this peeling is not preferable since it will cause a malfunction of the device.

The present invention provides an optical adhesive sheet for foldable devices, which is suitable for ensuring reworkability of being attached to an adherend and suppressing peeling from a bent adherend. [Technical means to solve the problem]

The present invention [1] includes an optical adhesive sheet for foldable devices, which has an adhesive layer, the adhesive layer has a shear storage elastic modulus of 20 kPa to 50 kPa at 25°C, and the adhesive After the agent layer is attached to the adherend at 25°C for 2 minutes for the first time, the adherend has a first adhesive force Xa at 25°C. The adhesive layer is attached to the adherend Then heat and pressurize the adherend under the conditions of 50°C, 0.5 MPa and 15 minutes, and then put it at 25°C for 72 hours. The adhesive force Xb, the first adhesive force Xa and the second adhesive force Xb satisfy 2.2≦Xb/Xa≦5.

Regarding the adhesive layer of the optical adhesive sheet of the present invention, the above-mentioned first adhesive force Xa (adhesive force at 2 minutes after being attached to the adherend) and the above-mentioned second adhesive force Xb (heated and pressurized after being attached) Adhesion after 72 hours) satisfies 2.2≦Xb/Xa≦5. A configuration in which the ratio (Xb/Xa) of the second adhesive force Xb to the first adhesive force Xa is 2.2 or more (a configuration in which the first adhesive force Xa is reduced such that Xb/Xa is about 2.2 or greater) is suitable for use in In the bonding operation of the optical adhesive sheet to the adherend, the light peeling property of the adhesive layer is ensured to ensure reworkability, and after the optical adhesive sheet is used to bond the adherend indirectly, it takes about 72 hours. The internal adhesive force increases over time to ensure a specific bonding force. A configuration in which the ratio (Xb/Xa) is 5 or less (a configuration in which the first adhesive force Xa is not too small so that Xb/Xa is about 5 or less) is suitable for securing the adhesive layer in the above lamination operation. The required adhesive force is used to achieve good temporary fixation of the optical adhesive sheet to the adherend, and to ensure the above-mentioned adhesion between the adherends. That is, the present optical adhesive sheet is suitable for both the appropriate implementation of the bonding operation and the reworkability, and the bonding force after bonding between adherends is ensured by increasing the adhesive force of the adhesive layer over time.

Moreover, the adhesive layer of this optical adhesive sheet has the shear storage elastic modulus of 20 kPa or more and 50 kPa or less at 25 degreeC as mentioned above. The adhesive layer having this degree of flexibility is suitable for ensuring the cohesive force required for the bonding between the adherends, and when the adherend to which the adhesive layer is attached is bent, it acts locally on the bending portion. The stress on the adhesive layer is relaxed. Therefore, this optical adhesive sheet is suitable for suppressing peeling from the bent adherend.

The present invention [2] includes the optical adhesive sheet for foldable devices as described in the above [1], wherein the above-mentioned adhesive layer is attached to the above-mentioned adherend, subjected to the above-mentioned heat and pressure treatment, and then after 25 After the third standing still at ℃ for 168 hours, the adherend has a third adhesive force Xc at 25°C, and the first adhesive force Xa and the third adhesive force Xc satisfy 2.5≦Xc/Xa≦7.

A configuration in which the ratio (Xc/Xa) of the third adhesive force Xc to the first adhesive force Xa is 2.5 or more (a configuration in which the third adhesive force Xc is increased so that Xc/Xa is about 2.5 or greater) is essential for securing utilization. This optical adhesive sheet is preferable in terms of bonding reliability between adherends. The configuration where Xc/Xa is 7 or less (the first adhesive force Xa is not too small so that Xc/Xa is 7 or less) is essential for ensuring the above-mentioned bonding reliability, and also for the relationship between the optical adhesive sheet and the adherend. It is preferable to achieve a good temporary fixation of the optical adhesive sheet to the adherend in the bonding operation.

The present invention [3] includes the optical adhesive sheet for foldable devices as described in the above [1] or [2], wherein the adhesive layer is bonded to the adherend at 25°C for 30 minutes for the second 4 After standing still, the adherend has a fourth adhesive force Xd at 25°C, and the first adhesive force Xa and the fourth adhesive force Xd satisfy 0.7≦Xd/Xa≦1.4.

Such a configuration is preferable for peeling the optical adhesive sheet temporarily attached to the adherend from the adherend as needed in the bonding operation of the optical adhesive sheet to the adherend, and therefore, it is useful for securing the bonding operation. It is better in terms of reprocessing.

The present invention [4] includes the optical adhesive sheet for foldable devices described in any one of the above-mentioned [1] to [3], wherein the above-mentioned adhesive layer is bonded to the above-mentioned to-be-adhered During the fifth standing period of 300 minutes, the minimum adhesive force Ya to the adherend at 25° C. is 0.1 N/25 mm or more.

Such a configuration is preferable for achieving good temporary fixation of the optical adhesive sheet to the adherend in the bonding operation of the optical adhesive sheet to the adherend.

The present invention [5] includes the optical adhesive sheet for a foldable device as described in the above [4], wherein the elapsed time Ta of the adhesive layer is attached to the adherend until it has the minimum adhesive force Ya (min) satisfies 0≦Ta≦100.

Such a configuration is preferable for peeling the optical adhesive sheet temporarily bonded to the adherend from the adherend as needed, and therefore, it is preferable for securing reworkability in the bonding operation.

The present invention [6] includes the optical adhesive sheet for foldable devices described in any one of the above-mentioned [1] to [5], wherein the above-mentioned first adhesive force Xa is 0.1 N/25 mm or more and 10 N/25 mm or less.

Such a configuration is preferable for both the appropriate implementation of the bonding operation of the optical adhesive sheet to the adherend and the reworkability of the operation.

The adhesive sheet S which is one embodiment of the optical adhesive sheet for foldable devices of the present invention includes an adhesive layer 10 as shown in FIG. 1 . The adhesive sheet S has a sheet shape with a predetermined thickness, and extends in a direction (surface direction) perpendicular to the thickness direction. FIG. 1 exemplarily shows a state where release films L1 and L2 (release liners) are bonded to both surfaces of an adhesive sheet S. As shown in FIG. The peeling film L1 is arrange|positioned on one surface of the thickness direction T of the adhesive sheet S. The peeling film L2 is arrange|positioned on the other surface of the thickness direction T of the adhesive sheet S. The adhesive sheet S with a release film is, for example, in the form of a roll (not shown).

This adhesive sheet S is a transparent adhesive sheet (optical adhesive sheet) arranged at the light passing part of the foldable device. As a foldable device, for example, a foldable display panel may be mentioned. The foldable display panel has, for example, a laminated structure including a pixel panel, a touch panel, a polarizer, and a cover film. The adhesive sheet S is used, for example, to join the elements included in the above-mentioned laminated structure during the manufacturing process of the foldable display panel.

The adhesive layer 10 has a shear storage elastic modulus of 20 kPa to 50 kPa at 25°C, and the first adhesive force Xa and the second adhesive force Xb satisfy 2.2≦Xb/Xa≦5.

The above-mentioned shear storage modulus of the adhesive layer 10 is a storage modulus determined by the dynamic viscoelasticity measurement described below for the examples (the same applies to the shear storage modulus described below). The first adhesive force Xa refers to the adhesive force of the adhesive layer 10 on the adherend at 25°C after it is attached to the adherend and left at 25°C for 2 minutes (first standing). The second adhesive force Xb-based adhesive layer 10 is attached to the adherend, then subjected to heat and pressure treatment, and then left to stand at 25° C. for 72 hours (second stand), the adherend The adhesive force of the body at 25°C. Adhered system polyimide film (the same applies to the adherend described below). The adhesion of the adhesive layer 10 to the adherend was performed under a load of reciprocating a 2 kg roller once in an environment of 25° C. (the same applies to the adhesion below). The heat and pressure treatment is performed under the conditions of a temperature of 50°C, a pressure of 0.5 MPa, and a treatment time of 15 minutes. The treatment starts within 3 minutes after the adhesive layer 10 is attached to the adherend (for the following The same is true for heat and pressure treatment). Adhesive force is an adhesive force measured as a peel strength by a peel test under conditions of a measurement temperature of 25°C, a peel angle of 180°, and a tensile speed of 300 mm/min (the same applies to the following adhesive force).

The adhesive layer 10 in the adhesive sheet S is as described above, the first adhesive force Xa (the adhesive force at 2 minutes after being attached to the adherend) and the above-mentioned second adhesive force Xb (the adhesive force after heat and pressure treatment after attachment) Adhesion after 72 hours) satisfies 2.2≦Xb/Xa≦5. A configuration in which the ratio (Xb/Xa) of the second adhesive force Xb to the first adhesive force Xa is 2.2 or more (a configuration in which the first adhesive force Xa is reduced such that Xb/Xa is about 2.2 or greater) is suitable for use in In the bonding operation of the adhesive sheet S to the adherend (for example, the bonding described below with reference to FIG. 2A ), the easy peelability of the adhesive layer 10 is ensured to ensure reworkability, and the adhesive sheet S will be used After bonding between adherends, a specific bonding force is ensured by increasing the adhesive force over time in a short period of about 72 hours. Ensuring reworkability helps to improve the manufacturing yield of foldable devices using the adhesive sheet S. On the other hand, a configuration in which the ratio (Xb/Xa) is 5 or less (a configuration in which the first adhesive force Xa is not too small so that Xb/Xa is about 5 or less) is suitable for securing the adhesive in the above-mentioned bonding operation. The layer 10 has the adhesive force necessary for this operation, realizes good temporary fixation of the adhesive sheet S to the adherend, and ensures the above-mentioned adhesion between the adherends. That is, the adhesive sheet S is suitable for both the appropriate implementation of the bonding operation and the reworkability, and the adhesive force of the adhesive layer 10 increases over time to ensure the bonding force after bonding between the adherends. When a sufficient bonding force is ensured by increasing the adhesive force of the adhesive layer 10 over time between the elements (adhered bodies) of the foldable device manufactured using the adhesive sheet S, the manufacture of the device During the process, for example, the aging process of the adhesive layer 10 in the factory can be eliminated (aging is performed during the shipping process at normal temperature, for example).

Moreover, the adhesive layer 10 has the shear storage elastic modulus of 20 kPa or more and 50 kPa or less at 25 degreeC as mentioned above. The adhesive layer 10 having this level of flexibility is suitable for ensuring the cohesive force required for bonding between adherends, and when bending the adherend to which the adhesive layer 10 is attached, it is suitable for partially The stress acting on the adhesive layer 10 is relaxed. Therefore, the adhesive sheet S is suitable for suppressing peeling from the bent adherend.

As described above, the adhesive sheet S is suitable for ensuring reworkability of sticking to an adherend and suppressing peeling from the bent adherend. In addition, the configuration in which the adhesive layer 10 has a shear storage elastic modulus of 20 kPa to 50 kPa at 25° C. is suitable for suppressing adhesion from the adhesive layer 10 during cutting in the production process of the adhesive sheet S. Tablets are attached to a cutting mechanism such as a Thomson knife used. Therefore, this configuration is suitable for achieving good processing yield of the adhesive sheet S.

From the standpoint of securing the reworkability of the bonding operation of the adhesive sheet S to the adherend and securing the bonding force after the adhesive sheet S is used to bond the adherends, Xb/Xa is preferably 2.3 or more, More preferably, it is 2.4 or more, Still more preferably, it is 2.5 or more. From the standpoint of achieving good temporary fixation of the adhesive sheet S to the adherend in the bonding operation and ensuring the above-mentioned adhesive force between the adherends, Xb/Xa is preferably 4.5 or less, more preferably 4.0 or less, and further Preferably it is 3.5 or less.

The first adhesive force Xa and the third adhesive force Xc of the adhesive layer 10 satisfy 2.3≦Xc/Xa≦7. The third adhesive force Xc-based adhesive layer 10 is attached to the adherend, subjected to the above-mentioned heat and pressure treatment, and then left at 25° C. for 168 hours (third standing), the adherend Adhesive force at 25°C.

A configuration in which the ratio (Xc/Xa) of the third adhesive force Xc to the first adhesive force Xa is 2.3 or more (a configuration in which the third adhesive force Xc is increased so that Xc/Xa is about 2.3 or greater) is essential for securing utilization. The bonding reliability between the adherends of the adhesive sheet S is preferable. From this point of view, Xc/Xa is more preferably at least 2.4, further preferably at least 2.5, and particularly preferably at least 2.6. The configuration where Xc/Xa is 7 or less (the first adhesive force Xa is not too small, so that Xc/Xa is about 7 or less) is essential for ensuring the above-mentioned bonding reliability, and the relationship between the adhesive sheet S and the adherend It is preferable to achieve good temporary fixation of the adhesive sheet S to the adherend in the bonding operation. From this point of view, Xc/Xa is more preferably 4.5 or less, further preferably 4.0 or less, particularly preferably 3.5 or less.

The first adhesive force Xa and the fourth adhesive force Xd of the adhesive layer 10 satisfy 0.7≦Xd/Xa≦1.4. The fourth adhesive force Xd refers to the adhesive force of the adhesive layer 10 on the adherend at 25° C. after the adhesive layer 10 is attached to the adherend and left at 25° C. for 30 minutes (the fourth standing still). The above configuration satisfying 0.7≦Xd/Xa≦1.4 is preferable for peeling the adhesive sheet S temporarily attached to the adherend from the adherend as necessary in the bonding operation of the adhesive sheet S to the adherend , Therefore, it is better to ensure the reworkability of the bonding operation.

When the adhesive layer 10 is attached to the adherend and left at 25°C for 300 minutes (the fifth rest), the minimum adhesive force Ya at 25°C to the adherend is preferably 0.1 N /25 mm or more, more preferably 1 N/25 mm or more, further preferably 3 N/25 mm or more, especially preferably 5 N/25 mm or more. Such a configuration is preferable for achieving good temporary fixation of the adhesive sheet S to the adherend in the bonding operation of the adhesive sheet S to the adherend. As a method of adjusting the minimum adhesive force Ya, selection of the kind of base polymer used for the adhesive layer 10, adjustment of molecular weight, and adjustment of a compounding quantity are mentioned, for example. Selection of the type of base polymer includes selection of the type (constitution) of the main chain of the base polymer, selection of the type of functional group and adjustment of the amount (the same applies to the selection of the type of base polymer described below). As the method of adjusting the minimum adhesive force Ya, selection of the type of components other than the base polymer and adjustment of the compounding amount of the components may also be mentioned. As this component, a crosslinking agent, a silane coupling agent, and an oligomer are mentioned.

The elapsed time Ta (minutes) from when the adhesive layer 10 is attached to the adherend until it has the minimum adhesive force Ya preferably satisfies 0≦Ta≦100. Such a configuration is preferable for peeling the adhesive sheet S temporarily bonded to the adherend from the adherend as needed, and thus is preferable for securing reworkability in the bonding operation. As a method of adjusting the elapsed time Ta, for example, selection of the type of base polymer used for the adhesive layer 10 , adjustment of the molecular weight, and adjustment of the compounding amount may be mentioned. As a method of adjusting the elapsed time Ta, selection of the type of components other than the base polymer and adjustment of the compounding amount of the components are also exemplified. As this component, a crosslinking agent, a silane coupling agent, and an oligomer are mentioned.

The first adhesive force Xa is preferably at least 0.1 N/25 mm, more preferably at least 1 N/25 mm, further preferably at least 3 N/25 mm, particularly preferably at least 5 N/25 mm. The first adhesive force Xa is preferably at most 10 N/25 mm, more preferably at most 9 N/25 mm, further preferably at most 8 N/25 mm. Such a configuration is preferable for both the proper implementation of the bonding operation of the adhesive sheet S to the adherend and the reworkability of the operation. As a method of adjusting the first adhesive force Xa, for example, selection of the type of base polymer used in the adhesive layer 10, adjustment of the molecular weight, adjustment of the blending amount, and components other than the base polymer (such as cross-linking) Selection of types of coupling agent, silane coupling agent, and oligomer) and adjustment of the blending amount. Regarding the second adhesive force Xb, the ratio of the second adhesive force to the first adhesive force Xa (Xb/Xa), the third adhesive force Xc, and the ratio of the third adhesive force Xc to the first adhesive force Xa (Xc/Xa ), the fourth adhesive force Xd, and each adjustment method of the ratio (Xd/Xa) of the fourth adhesive force Xd to the first adhesive force Xa is the same.

The second adhesive force Xb is preferably at least 0.2 N/25 mm, more preferably at least 2 N/25 mm, further preferably at least 5 N/25 mm, particularly preferably at least 6 N/25 mm. The second adhesive force Xb is preferably at most 50 N/25 mm, more preferably at most 40 N/25 mm, further preferably at most 30 N/25 mm.

The third adhesive force Xc is preferably at least 0.2 N/25 mm, more preferably at least 2 N/25 mm, further preferably at least 5 N/25 mm, particularly preferably at least 6 N/25 mm. The third adhesive force Xc is preferably at most 50 N/25 mm, more preferably at most 40 N/25 mm, further preferably at most 30 N/25 mm.

The fourth adhesive force Xd is preferably at least 0.1 N/25 mm, more preferably at least 1 N/25 mm, further preferably at least 3 N/25 mm, particularly preferably at least 5 N/25 mm. The fourth adhesive force Xd is preferably at most 10 N/25 mm, more preferably at most 9 N/25 mm, further preferably at most 8 N/25 mm.

From the viewpoint of ensuring the above-mentioned cohesion, the above-mentioned shear storage elastic modulus (first storage elastic modulus Ma) of the adhesive layer 10 is preferably 25 kPa or more, more preferably 30 kPa or more, and still more preferably 33 kPa. above kPa, preferably above 35 kPa. From the viewpoint of stress relaxation, the first storage elastic modulus Ma is preferably at most 50 kPa, more preferably at most 45 kPa, still more preferably at most 43 kPa, and most preferably at most 40 kPa. As a method of adjusting the first modulus of elasticity Ma of the adhesive layer 10, for example, selection of the type of the base polymer used in the adhesive layer 10, adjustment of the molecular weight, adjustment of the blending amount, and exchange Selection of the type of joint agent and adjustment of the blending amount. Regarding the following second storage modulus Mb, the ratio (Mb/Ma) of the second storage modulus Mb to the first storage modulus Ma, the following third storage modulus Mc, and the third storage modulus The same applies to each adjustment method of the ratio (Mc/Ma) of the modulus Mc to the first storage elastic modulus Ma.

The shear storage elastic modulus (second storage elastic modulus Mb) of the adhesive layer 10 at 60°C is from the viewpoint of ensuring the above-mentioned cohesive force necessary for bonding between adherends in a temperature range around 60°C, It is preferably at least 18 kPa, more preferably at least 23 kPa, and still more preferably at least 25 kPa. The second storage elastic modulus Mb is preferably 45 kPa or less, more preferably 43 kPa or less, and still more preferably 40 kPa, from the viewpoint of suppressing peeling from the bent adherend in a temperature range around 60°C. the following.

The ratio (Mb/Ma) of the second storage modulus of elasticity Mb to the first storage modulus of elasticity Ma preferably satisfies 0.6≦Mb/Ma≦1. Such a configuration is preferable from the viewpoint of stabilization of adhesive properties in the temperature range from normal temperature to around 60°C.

From the viewpoint of ensuring the above-mentioned cohesive force necessary for bonding between adherends in a temperature range around 85°C, the shear storage modulus of the adhesive layer 10 at 85°C (third storage modulus Mc) It is preferably at least 15 kPa, more preferably at least 18 kPa, and still more preferably at least 20 kPa. From the viewpoint of suppressing peeling from the bent adherend in a temperature range around 85°C, the third storage elastic modulus Mc is preferably 45 kPa or less, more preferably 43 kPa or less, further preferably 40 kPa the following.

The ratio (Mc/Ma) of the third storage elastic modulus Mc to the first storage elastic modulus Ma preferably satisfies 0.5≦Mb/Ma≦0.8. Such a configuration is preferable from the viewpoint of stabilization of adhesive properties in the temperature range from normal temperature to around 85°C.

The adhesive layer 10 is a pressure-sensitive adhesive layer formed from an adhesive composition. The adhesive layer 10 has transparency (visible light transmittance). The adhesive layer 10 contains at least a base polymer.

The base polymer is an adhesive component that expresses adhesiveness in the adhesive layer 10 . As the base polymer, for example, acrylic polymers, silicone polymers, polyester polymers, polyurethane polymers, polyamide polymers, polyvinyl ether polymers, vinyl acetate/ Vinyl chloride copolymers, modified polyolefin polymers, epoxy polymers, fluoropolymers, and rubber polymers. The base polymer may be used alone or in combination of two or more. From the viewpoint of securing good transparency and adhesiveness of the adhesive layer 10 , it is preferable to use an acrylic polymer as the base polymer.

The acrylic polymer is a copolymer containing a monomer component of an alkyl (meth)acrylate in a ratio of 50% by mass or more. "(Meth)acrylic acid" means acrylic acid and/or methacrylic acid.

As the alkyl (meth)acrylate, an alkyl (meth)acrylate having 1 to 20 carbon atoms in the alkyl group is suitably used. Alkyl (meth)acrylate may have linear or branched alkyl groups, and may have cyclic alkyl groups such as alicyclic alkyl groups.

Examples of the alkyl (meth)acrylate having a linear or branched alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, Isobutyl (meth)acrylate, second butyl (meth)acrylate, third butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, (meth) Neopentyl acrylate, Hexyl (meth)acrylate, Heptyl (meth)acrylate, 2-Ethylhexyl (meth)acrylate, Octyl (meth)acrylate, Isooctyl (meth)acrylate, Nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, (meth)acrylic acid Lauryl acrylate (Lauryl acrylate), Isotridecyl (meth)acrylate, Myristyl (meth)acrylate, Isotetradecyl (meth)acrylate, (Meth) ) pentadecyl acrylate, cetyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isostearyl (meth)acrylate , and nonadecyl (meth)acrylate.

Examples of alkyl (meth)acrylates having an alicyclic alkyl group include cycloalkyl (meth)acrylates, (meth)acrylates having a bicyclic aliphatic hydrocarbon ring, and (Meth)acrylate of aliphatic hydrocarbon ring with three or more rings. Examples of cycloalkyl (meth)acrylates include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclopentyl (meth)acrylate. Octyl esters. As (meth)acrylate which has a bicyclic aliphatic hydrocarbon ring, iso(meth)acrylate is mentioned, for example. Examples of (meth)acrylates having an aliphatic hydrocarbon ring having three or more rings include: dicyclopentanyl (meth)acrylate, dicyclopentyloxyethyl (meth)acrylate, (meth)acrylic acid Tricyclopentyl, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate ester.

As the alkyl (meth)acrylate, it is preferable to use an alkyl acrylate having an alkyl group having 3 to 15 carbon atoms, and it is more preferable to use an alkyl acrylate selected from n-butyl acrylate, 2-ethylhexyl acrylate, and acrylic acid. At least one of the group consisting of dodecyl esters.

From the viewpoint of appropriately expressing basic properties such as adhesiveness of the adhesive layer 10, the ratio of the alkyl (meth)acrylate in the monomer component is preferably at least 50% by mass, more preferably at least 60% by mass. , and more preferably at least 70% by mass. This ratio is, for example, 99% by mass or less.

The monomer component may also contain a copolymerizable monomer that can be copolymerized with an alkyl (meth)acrylate. As a copolymerizable monomer, the monomer which has a polar group is mentioned, for example. As a polar group containing monomer, the monomer which has a ring containing a nitrogen atom, a hydroxyl group containing monomer, and a carboxyl group containing monomer are mentioned, for example. Polar group-containing monomers help to introduce crosslinking points into acrylic polymers, ensure the cohesion of acrylic polymers, and contribute to the modification of acrylic polymers.

Examples of monomers having a ring containing a nitrogen atom include: N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone , N-vinylpyrimidine, N-vinylpiperazole, N-vinylpyrrole, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryl- 2-pyrrolidone, N-(meth)acrylpiperidine, N-(meth)acrylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N- Vinyl-2-caprolactam, N-vinyl-1,3-㗁𠯤-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-ethylene Isoxazole, N-vinylthiazole, and N-vinylisothiazole. As a monomer having a nitrogen atom-containing ring, N-vinyl-2-pyrrolidone is preferably used.

From the viewpoint of ensuring the cohesive force in the adhesive layer 10 and ensuring the adhesion of the adhesive layer 10 to the adherend, the ratio of the monomer having a nitrogen atom-containing ring in the monomer component is preferably 0.1% by mass above, more preferably at least 0.3% by mass, and still more preferably at least 0.55% by mass. From the viewpoint of adjusting the glass transition temperature of the acrylic polymer and adjusting the polarity of the acrylic polymer (compatibility between various additive components in the adhesive layer 10 and the acrylic polymer), the ratio is preferably 30 mass % or less, more preferably 20 mass % or less.

Examples of the hydroxyl group-containing monomer include: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxy (meth)acrylate - Hydroxypropyl, 4-Hydroxybutyl (meth)acrylate, 6-Hydroxyhexyl (meth)acrylate, 8-Hydroxyoctyl (meth)acrylate, 10-Hydroxydecyl (meth)acrylate, ( 12-Hydroxylauryl meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. As a hydroxyl group-containing monomer, it is preferable to use 4-hydroxybutyl (meth)acrylate, and it is more preferable to use 4-hydroxybutyl acrylate.

From the viewpoint of introducing a crosslinked structure into the acrylic polymer and ensuring cohesion in the adhesive layer 10, the ratio of the hydroxyl group-containing monomer in the monomer component is preferably 0.1% by mass or more, more preferably 0.5% by mass % or more, and more preferably 0.8% by mass or more. From the viewpoint of adjusting the polarity of the acrylic polymer (compatibility between the various additive components in the adhesive layer 10 and the acrylic polymer), the ratio is preferably 20% by mass or less, more preferably 10% by mass. the following.

Examples of carboxyl group-containing monomers include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and methacrylic acid. .

From the viewpoint of introducing a cross-linked structure to the acrylic polymer, ensuring the cohesion in the adhesive layer 10, and ensuring the adhesion of the adhesive layer 10 to the adherend, the ratio of the carboxyl group-containing monomer in the monomer component Preferably it is 0.1 mass % or more, More preferably, it is 0.5 mass % or more, More preferably, it is 0.8 mass % or more. From the viewpoint of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of corrosion of the adherend due to acid, the ratio is preferably at most 30% by mass, more preferably at most 20% by mass.

In order to prevent metal elements such as electrodes in the foldable device from being corroded by acid components, the adhesive layer 10 of the adhesive sheet S preferably has a small acid content. Also, when the adhesive sheet S is used for bonding polarizing plates, the adhesive layer 10 preferably has a small acid content in order to suppress polyeneization of the polyvinyl alcohol-based polarizing element due to the acid component. In this acid-free adhesive sheet S, the content of organic acid monomers (such as (meth)acrylic acid and carboxyl group-containing monomers) in the adhesive layer 10 is preferably less than 100 ppm, more preferably less than 70 ppm, Furthermore, it is more preferably 50 ppm or less. The organic acid monomer content of the adhesive layer 10 was obtained by immersing the adhesive layer 10 in pure water and heating it at 100° C. for 45 minutes to extract the acid monomer from the water, by Ion chromatography quantifies the acid monomer.

From the viewpoint of no acid, it is preferable that the base polymer in the adhesive layer 10 does not substantially contain an organic acid monomer as a monomer component. From the viewpoint of acid-free, the ratio of the organic acid monomer in the monomer component is preferably at most 0.5% by mass, more preferably at most 0.1% by mass, still more preferably 0.05% by mass, and ideally 0% by mass.

The monomer component may also contain other copolymerizable monomers. As other copolymerizable monomers, for example, acid anhydride monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, alkoxy group-containing monomers, and Aromatic vinyl compounds. These other copolymerizable monomers may be used alone or in combination of two or more.

In this embodiment, the base polymer has a crosslinked structure. As a method of introducing a cross-linked structure into the base polymer, for example, a base polymer having a functional group capable of reacting with a cross-linking agent and a cross-linking agent are formulated into an adhesive composition, and the base polymer and the cross-linking agent are mixed. A method of reacting an agent in the adhesive layer 10 (the first method); and including a multifunctional monomer in the monomer component forming the base polymer, and by polymerizing the monomer component, the polymer chain is formed to introduce The method of the base polymer of the branched structure (cross-linked structure). These methods can be used in combination.

As a crosslinking agent used by the said 1st method, the compound which reacts with the functional group (hydroxyl group, carboxyl group, etc.) contained in a base polymer is mentioned, for example. Examples of such crosslinking agents include isocyanate crosslinking agents, peroxide crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, and carbodiimide crosslinking agents. agent, and metal chelate crosslinking agent. A crosslinking agent may be used individually or in combination of 2 or more types. As the crosslinking agent, it is preferable to use isocyanate crosslinking agent, peroxide crosslinking agent, and epoxy crosslinking agent.

As the isocyanate crosslinking agent, for example, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, Hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenylisocyanate. Moreover, as an isocyanate crosslinking agent, the derivative|guide_body of these isocyanate is also mentioned. As this isocyanate derivative, an isocyanurate modified product and a polyol modified product are mentioned, for example. Commercially available isocyanate crosslinking agents include, for example, Coronate L (trimethylolpropane adduct of toluene diisocyanate, manufactured by Tosoh), Coronate HL (trimethylolpropane of hexamethylene diisocyanate) adduct, manufactured by Tosoh), Coronate HX (isocyanurate body of hexamethylene diisocyanate, manufactured by Tosoh), and Takenate D110N (trimethylolpropane adduct of xylylene diisocyanate, manufactured by Mitsui chemical manufacturing).

Examples of peroxide crosslinking agents include dibenzoyl peroxide, bis(2-ethylhexyl) peroxydicarbonate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, Di-2-butyl peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-hexyl peroxypivalate, and tert-butyl peroxypivalate.

Examples of the epoxy crosslinking agent include bisphenol A, epichlorohydrin type epoxy resin, ethylidene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether , 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidylamine, N,N,N',N'-tetraglycidyl-meta Xylylenediamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

An isocyanate crosslinking agent (particularly, a difunctional isocyanate crosslinking agent) and a peroxide crosslinking agent are preferable from the viewpoint of securing appropriate flexibility (therefore, flexibility) of the adhesive layer 10 . An isocyanate crosslinking agent (particularly, a trifunctional isocyanate crosslinking agent) is preferable from the viewpoint of securing the durability of the adhesive layer 10 . In the base polymer, the difunctional isocyanate crosslinking agent and peroxide crosslinking agent form softer two-dimensional crosslinking, while the trifunctional isocyanate crosslinking agent forms stronger three-dimensional crosslinking. From the viewpoint of achieving both durability and flexibility of the adhesive layer 10 , it is preferable to use a trifunctional isocyanate crosslinking agent, a peroxide crosslinking agent and/or a difunctional isocyanate crosslinking agent in combination.

From the viewpoint of securing the cohesive force of the adhesive layer 10, the amount of the crosslinking agent to be formulated is, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more, more preferably 0.07 parts by mass relative to 100 parts by mass of the base polymer above. From the viewpoint of securing good adhesiveness of the adhesive layer 10, the compounding amount of the crosslinking agent is, for example, 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 3 parts by mass relative to 100 parts by mass of the base polymer. Parts by mass or less.

In the above-mentioned second method, monomer components (including polyfunctional monomers and other monomers for introducing a crosslinking structure) may be polymerized at one time or in multiple stages. In the multi-stage polymerization method, first, the monofunctional monomer used to form the base polymer is polymerized (prepolymerized), thereby preparing a prepolymerized polymer containing a part of the polymer (a mixture of a polymer with a low degree of polymerization and an unreacted monomer). composition. Next, after adding a multifunctional monomer to the prepolymer composition, a part of the polymer is polymerized with the multifunctional monomer (mainly polymerized).

As a polyfunctional monomer, the polyfunctional (meth)acrylate which has 2 or more ethylenically unsaturated double bonds in 1 molecule is mentioned, for example. As the polyfunctional monomer, a polyfunctional acrylate is preferable from the viewpoint of being able to introduce a crosslinked structure by active energy ray polymerization (photopolymerization).

As a polyfunctional (meth)acrylate, a difunctional (meth)acrylate, a trifunctional (meth)acrylate, and a tetrafunctional or more polyfunctional (meth)acrylate are mentioned.

As the difunctional (meth)acrylate, for example, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, Tetraethylene glycol dimethacrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, new Pentylene glycol di(meth)acrylate, stearic acid modified pentaerythritol di(meth)acrylate, dicyclopentenyl diacrylate, di(meth)acryl isocyanurate, and cyclic Oxyalkylene-modified bisphenol di(meth)acrylate.

Trifunctional (meth)acrylates include, for example, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and tris(acryloxyethyl)isocyanurate. .

As the tetrafunctional or more polyfunctional (meth)acrylate, for example, di-trimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, base) acrylate, alkyl-modified dipentaerythritol pentaacrylate, and dipentaerythritol hexa(meth)acrylate.

The molecular weight of the polyfunctional monomer is preferably 1500 or less, more preferably 1000 or less. Moreover, the functional group equivalent (g/eq) of a polyfunctional monomer becomes like this. Preferably it is 50 or more, More preferably, it is 70 or more, More preferably, it is 80 or more. The functional group equivalent weight is preferably 500 or less, more preferably 300 or less, further preferably 200 or less. These constitutions are preferable from the viewpoint of appropriately adjusting viscoelasticity (for example, storage elastic modulus G' and loss tangent tanδ) by introducing a crosslinked structure into the base polymer.

An acrylic polymer can be formed by polymerizing the above-mentioned monomer components. As a polymerization method, for example, solution polymerization, active energy ray polymerization (for example, UV polymerization), bulk polymerization, and emulsion polymerization may be mentioned. From the viewpoints of transparency, water resistance, and cost of the adhesive layer 10, solution polymerization and UV polymerization are preferable. As a solvent for solution polymerization, ethyl acetate and toluene can be used, for example. Moreover, as a polymerization initiator, a thermal polymerization initiator and a photopolymerization initiator can be used, for example. The usage-amount of a polymerization initiator is 0.05 mass part or more with respect to 100 mass parts of monomer components, and is, for example, 1 mass part or less.

As a thermal polymerization initiator, an azo polymerization initiator and a peroxide polymerization initiator are mentioned, for example. As an azo polymerization initiator, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis( Dimethyl 2-methylpropionate, 4,4'-azobis-4-cyanopentanoic acid, azobisisovaleronitrile, 2,2'-azobis(2-amidinopropane)di Hydrochloride, 2,2'-Azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-Azobis(2-methyl propionamidine) disulfate, and 2,2'-azobis(N,N'-dimethyleneisobutylamidine) dihydrochloride. As a peroxide polymerization initiator, dibenzoyl peroxide, t-butyl peroxymaleate, and lauryl peroxide may be mentioned, for example.

系光聚合起始劑、及醯基氧化膦系光聚合起始劑。Examples of photopolymerization initiators include: benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-keto alcohol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization Initiator, photoactive oxime-based photopolymerization initiator, benzoin-based photopolymerization initiator, benzoyl-based photopolymerization initiator, benzophenone-based photopolymerization initiator, ketal-based photopolymerization initiator agent, 9-oxosulfur

It is a photopolymerization initiator, and an acyl phosphine oxide-based photopolymerization initiator.

During polymerization, a chain transfer agent and/or a polymerization inhibitor (polymerization retarder) may be used for the purpose of adjusting the molecular weight or the like. As the chain transfer agent, α-thioglycerol, lauryl mercaptan, glycidyl mercaptan, thioglycolic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolic acid, 2 , 3-dimercapto-1-propanol, and α-methylstyrene dimer.

By adjusting the type and/or amount of the polymerization initiator, the molecular weight of the base polymer can be adjusted. For example, in free radical polymerization, the more the amount of polymerization initiator is, the higher the concentration of free radicals in the reaction system is, so the density of reaction starting points is higher, and the molecular weight of the formed base polymer tends to be smaller. In contrast, the smaller the amount of the polymerization initiator, the lower the density of the reaction starting point, so the polymer chain is easier to elongate, and the molecular weight of the formed base polymer tends to increase.

The weight average molecular weight of the acrylic polymer is preferably at least 100,000, more preferably at least 300,000, and still more preferably at least 500,000, from the viewpoint of securing the cohesive force in the adhesive layer 10 . The weight average molecular weight is preferably at most 5 million, more preferably at most 3 million, further preferably at most 2 million. The weight average molecular weight of the acrylic polymer was measured by gel permeation chromatography (GPC), and calculated in terms of polystyrene.

The glass transition temperature (Tg) of the base polymer is preferably 0°C or lower, more preferably -10°C or lower, further preferably -20°C or lower. The glass transition temperature is, for example, -80°C or higher.

Regarding the glass transition temperature (Tg) of the base polymer, the glass transition temperature (theoretical value) obtained based on the following Fox formula can be used. The relationship between the glass transition temperature Tg of the Fox type polymer and the glass transition temperature Tgi of the homopolymer of the monomers that constitute the polymer. In the following Fox formula, Tg represents the glass transition temperature (°C) of the polymer, Wi represents the weight fraction of monomer i constituting the polymer, and Tgi represents the glass transition temperature of the homopolymer formed by monomer i ( ℃). For the glass transition temperature of the homopolymers, literature values can be used. For example, in "Polymer Handbook" (4th edition, John Wiley & Sons, Inc., 1999) and "New Polymer Library 7 Introduction to Synthetic Resins for Coatings" (Kyo Kitaoka, Polymer Press, 1995) The glass transition temperatures of various homopolymers are given. On the other hand, the glass transition temperature of the homopolymer of the monomer can also be obtained by the method specifically described in JP-A-2007-51271.

Fox formula 1/(273+Tg)=Σ[Wi/(273+Tgi)]

The adhesive composition may also contain one or two or more oligomers in addition to the base polymer. When using an acrylic polymer as a base polymer, it is preferable to use an acrylic oligomer as an oligomer. The acrylic oligomer is a copolymer containing a monomer component of an alkyl (meth)acrylate in a ratio of 50% by mass or more, and has a weight average molecular weight of, for example, 1,000 to 30,000.

The glass transition temperature of the acrylic oligomer is preferably at least 60°C, more preferably at least 80°C, still more preferably at least 100°C, particularly preferably at least 110°C. The glass transition temperature of the acrylic oligomer is, for example, 200°C or lower, preferably 180°C or lower, more preferably 160°C or lower. By using a low Tg acrylic polymer (base polymer) with a crosslinked structure and a high Tg acrylic oligomer in combination, the adhesive force of the adhesive layer 10 , especially the adhesive force at high temperature can be improved. The glass transition temperature of the acrylic oligomer was calculated by the above-mentioned Fox formula.

The acrylic oligomer having a glass transition temperature of 60° C. or higher preferably contains an alkyl (meth)acrylate (chain alkyl (meth)acrylate) with a chain alkyl group and an alicyclic alkyl group. A polymer of monomer components of alkyl (meth)acrylate (cycloalkyl (meth)acrylate). Specific examples of such alkyl (meth)acrylates include the above-mentioned alkyl (meth)acrylates that are monomer components of the acrylic polymer.

As the chain alkyl (meth)acrylate, methyl methacrylate is preferable in terms of high glass transition temperature and excellent compatibility with the base polymer. As the alicyclic alkyl (meth)acrylate, dicyclopentyl acrylate, dicyclopentyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate are preferable. That is, the acrylic oligomer preferably contains one or more kinds selected from the group consisting of dicyclopentyl acrylate, dicyclopentyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate together with methyl A polymer based on the monomer component of methyl acrylate.

The ratio of the alicyclic alkyl (meth)acrylate in the monomer component of the acrylic oligomer is preferably at least 10% by weight, more preferably at least 20% by weight, and still more preferably at least 30% by weight. The ratio is preferably at most 90% by weight, more preferably at most 80% by weight, further preferably at most 70% by weight. The ratio of the chain alkyl (meth)acrylate in the monomer component of the acrylic oligomer is preferably at most 90% by weight, more preferably at most 80% by weight, further preferably at most 70% by weight. The ratio is preferably at least 10% by weight, more preferably at least 20% by weight, and still more preferably at least 30% by weight.

The weight average molecular weight of the acrylic oligomer is preferably at least 1,000, more preferably at least 1,500, and still more preferably at least 2,000. The molecular weight is preferably at most 30000, more preferably at most 10000, still more preferably at most 8000. The molecular weight range of such an acrylic oligomer is preferable to ensure the adhesion and adhesion retention of the adhesive layer 10 .

The acrylic oligomer is obtained by polymerizing the monomer components of the acrylic oligomer. As a polymerization method, for example, solution polymerization, active energy ray polymerization (for example, UV polymerization), bulk polymerization, and emulsion polymerization may be mentioned. In the polymerization of the acrylic oligomer, a polymerization initiator may be used, and a chain transfer agent may be used for the purpose of adjusting the molecular weight.

In order to fully improve the adhesion of the adhesive layer 10, the content of the acrylic oligomer in the adhesive layer 10 is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, with respect to 100 parts by mass of the base polymer, and further Preferably it is 1 part by mass or more. On the other hand, from the viewpoint of ensuring the transparency of the adhesive layer 10, the content of the acrylic oligomer in the adhesive layer 10 is preferably 5 parts by mass or less, more preferably 100 parts by mass of the base polymer. It is 4 mass parts or less, More preferably, it is 3 mass parts or less. When the content of the acrylic oligomer in the adhesive layer 10 is too large, the compatibility of the acrylic oligomer decreases, and the haze tends to increase and the transparency tends to decrease.

The adhesive composition may also contain a silane coupling agent. The content of the silane coupling agent in the adhesive composition is preferably at least 0.1 parts by mass, more preferably at least 0.2 parts by mass, based on 100 parts by mass of the base polymer. The content is preferably at most 5 parts by mass, more preferably at most 3 parts by mass.

The adhesive composition may contain other components as needed. Examples of other components include tackifiers, plasticizers, softeners, anti-deterioration agents, fillers, colorants, ultraviolet absorbers, antioxidants, surfactants, and antistatic agents.

The adhesive sheet S can be manufactured by, for example, drying the coating film after applying the above-mentioned adhesive composition on the release film L1 (1st release film) to form a coating film.

As the release film, for example, a flexible plastic film may be mentioned. As this plastic film, a polyethylene terephthalate film, a polyethylene film, a polypropylene film, and a polyester film are mentioned, for example. The thickness of the release film is, for example, 3 μm or more, and, for example, 200 μm or less. The surface of the release film is preferably subjected to a release treatment.

Examples of coating methods for the adhesive composition include roll coating, touch roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, and rod coating. Coating, blade coating, air knife coating, curtain coating, lip coating, and die coating. The drying temperature of the coating film is, for example, 50°C to 200°C. The drying time is, for example, 5 seconds to 20 minutes.

The peeling film L2 (2nd peeling film) may be further laminated|stacked on the adhesive layer 10 on the 1st peeling film L1. The second release film is a flexible plastic film with a surface release treatment, and the same ones as those described above for the first release film can be used.

In the above manner, the adhesive sheet S whose adhesive surface is covered and protected by the release films L1 and L2 can be manufactured. The release films L1 and L2 are peeled from the adhesive sheet S when the adhesive sheet S is used as necessary.

From the viewpoint of securing sufficient adhesiveness to the adherend, the thickness of the adhesive layer 10 is preferably at least 10 μm, more preferably at least 15 μm. From the viewpoint of the handleability of the adhesive sheet S, the thickness of the adhesive layer 10 is preferably 300 μm or less, more preferably 200 μm or less, further preferably 100 μm or less, especially preferably 50 μm or less.

The haze of the adhesive layer 10 is preferably 3% or less, more preferably 2% or less, more preferably 1% or less. The haze of the adhesive layer 10 can be measured using a haze meter according to JIS K7136 (2000). Examples of the haze meter include "NDH2000" manufactured by Nippon Denshoku Kogyo Co., Ltd. and "HM-150" manufactured by Murakami Color Technology Research Institute Co., Ltd., for example.

The total light transmittance of the adhesive layer 10 is preferably at least 60%, more preferably at least 80%, and still more preferably at least 85%. The total light transmittance of the adhesive layer 10 is, for example, 100% or less. The total light transmittance of the adhesive layer 10 can be measured according to JIS K 7375 (2008).

2A to 2C show an example of how to use the adhesive sheet S. As shown in FIG.

In this method, first, as shown in FIG. 2A , the adhesive sheet S is attached to one surface in the thickness direction T of the first member 21 (adhered body). The first member 21 is, for example, one element of the laminated structure of the flexible panel. As this element, for example, a pixel panel, a touch panel, a polarizing plate, and a cover film can be mentioned (the same applies to the second member 22 described below). Through this step, the adhesive layer 10 for bonding with other members is provided on the first member 21 .

In this step, when bonding failure (for example, the positional displacement of the adhesive sheet S on the first member 21 ) occurs, the adhesive sheet S is peeled off from the first member 21 . Thereafter, the pasting operation was carried out again with an alternative adhesive sheet S.

Next, as shown in FIG. 2B , the one side in the thickness direction T of the first member 21 is bonded to the other side in the thickness direction T of the second member 22 via the adhesive layer 10 on the first member 21 . The second member 22 is, for example, another element of the laminated structure of the flexible panel.

Next, as shown in FIG. 2C , the adhesive layer 10 between the first member 21 and the second member 22 is aged. Through aging, the cross-linking reaction of the base polymer proceeds in the adhesive layer 10, and the bonding force between the first member 21 and the second member 22 is improved. The aging temperature is, for example, 20°C to 160°C. The aging time is, for example, 1 minute to 21 days. When performing autoclave treatment (heating and pressure treatment) as aging treatment, the temperature is, for example, 30°C to 80°C, the pressure is, for example, 0.1 to 0.8 MPa, and the treatment time is, for example, 15 minutes or more.

As for the adhesive sheet S used in the above-mentioned manner in the manufacturing process of the foldable device, the adhesive layer 10 has a shear storage elastic modulus of 20 kPa to 50 kPa at 25° C., and the first adhesive force Xa and The second adhesive force Xb satisfies 2.2≦Xb/Xa≦5. Such an adhesive sheet S is suitable for securing the reworkability of being attached to an adherend (the first member 21 in the above example of usage) as described above, and suppressing peeling from the bent adherend. [Example]

Examples are given below to describe the present invention in detail. This invention is not limited to an Example. In addition, the specific numerical values such as the blending amount (content), physical property values, and parameters described below can be replaced with the corresponding upper limits of the blending amount (content), physical property values, and parameters described in the above-mentioned "embodiment" (defined as A value that is "below" or "under") or a lower limit (defined as a value that is "above" or "exceeded").

<Preparation Example 1 of Acrylic Oligomer> In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, 95 parts by mass of cyclohexyl methacrylate (CHMA), 5 parts by mass of acrylic acid (AA), and α-methanol as a chain transfer agent A mixture of 10 parts by weight of phenylstyrene dimer and 120 parts by weight of toluene as a solvent was stirred under a nitrogen atmosphere at room temperature for 1 hour. Thereafter, 10 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) was added to the mixture as a thermal polymerization initiator to prepare a reaction solution, which was reacted at 85° C. for 5 hours under a nitrogen atmosphere (1st Formation of acrylic oligomers). Thereby, the oligomer solution (50 mass % of solid content concentration) containing the 1st acrylic oligomer was obtained. The weight average molecular weight of the 1st acrylic oligomer was 4300. In addition, the glass transition temperature (Tg) of the first acrylic oligomer was 84°C.

<Preparation Example 2 of Acrylic Oligomer> In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, 60 parts by mass of dicyclopentanyl methacrylate (DCPMA), 40 parts by mass of methyl methacrylate (MMA), as a chain transfer A mixture of 3.5 parts by mass of α-thioglycerol as an agent and 100 parts by mass of toluene as a solvent was stirred at 70° C. for 1 hour under a nitrogen atmosphere. Thereafter, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) was added to the mixture as a thermal polymerization initiator to prepare a reaction solution, which was reacted at 70° C. for 1 hour under a nitrogen atmosphere, and then Reaction was carried out at 80° C. for 2 hours (formation of the second acrylic oligomer). Thereafter, toluene, chain transfer agent and unreacted monomers were volatilized and removed by heating the reaction solution to 130°C. Thereby, the solid 2nd acrylic oligomer was obtained. The weight average molecular weight of the 2nd acrylic oligomer was 5100. The glass transition temperature (Tg) of the 2nd acrylic oligomer was 130 degreeC.

[Example 1] ＜Preparation of Acrylic Base Polymer＞ In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 70 parts by mass of 2-ethylhexyl acrylate (2EHA), 20 parts by mass of n-butyl acrylate (BA), 20 parts by mass of n-butyl acrylate, lauryl acrylate ( LA) 8 parts by mass, 4-hydroxybutyl acrylate (4HBA) 1 part by mass, N-vinyl-2-pyrrolidone (NVP) 0.6 parts by mass, 2,2'-azo as a thermal polymerization initiator A mixture (solid content concentration: 47% by mass) of 0.1 parts by mass of diisobutyronitrile (AIBN) and ethyl acetate as a solvent was stirred at 56° C. under a nitrogen atmosphere for 6 hours (polymerization reaction). Thereby, a polymer solution containing an acrylic base polymer was obtained. The weight average molecular weight of the acrylic base polymer in the polymer solution is about 2 million.

＜Preparation of Adhesive Composition＞ In the polymer solution, 1.5 parts by mass of the first acrylic oligomer, a first crosslinking agent (trade name "Nyper BMT-40SV", diperoxide Benzoyl, manufactured by NOF Corporation) 0.26 parts by mass, a second crosslinking agent (trade name "Coronate L", trimethylolpropane/toluene diisocyanate trimer adduct, manufactured by Tosoh) 0.02 parts by mass, and 0.3 parts by mass of a silane coupling agent (trade name "KBM403", manufactured by Shin-Etsu Chemical Co., Ltd.) was mixed to prepare an adhesive composition C1.

＜Formation of Adhesive Layer＞ Next, the adhesive composition C1 was applied on the peeling-treated surface of the first peeling film that had undergone silicone peeling treatment on one side to form a coating film. The first release film is a polyethylene terephthalate (PET) film (trade name "DIAFOIL MRF#75", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) with one side treated with silicone release. Next, the coating film on the first release film is pasted to the release-treated surface of the second release film that has undergone silicone release treatment on one side. The second release film is a PET film (trade name "DIAFOIL MRF#75", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) with one side treated with silicone release. Next, the coating film on the first release film was dried by heating at 100° C. for 1 minute and then at 150° C. for 3 minutes to form a transparent adhesive layer with a thickness of 50 μm. In the above manner, the adhesive sheet of Example 1 having a transparent adhesive layer (50 μm in thickness) was produced. The monomer composition and the adhesive layer composition of the acrylic base polymer in the adhesive sheet of Example 1 are shown in Table 1 in units of parts by mass (the same applies to the following Examples and Comparative Examples).

[Embodiments 2-4] The adhesive sheets of Examples 2 to 4 were produced in the same manner as the adhesive sheet of Example 1, except that the monomer composition was changed as shown in Table 1 in the preparation of the acrylic base polymer.

[Example 5, 6] Examples 5 and 6 were produced in the same manner as the adhesive sheet of Example 1, except that the thickness of the formed adhesive layer was set to 25 μm (Example 5) or 100 μm (Example 6) instead of 50 μm. Each adhesive sheet.

[Comparative example 1] For 56 parts by mass of 2-ethylhexyl acrylate (2EHA), 34 parts by mass of lauryl acrylate (LA), 7 parts by mass of 4-hydroxybutyl acrylate (4HBA), N-vinyl-2-pyrrolidone ( NVP) 2 mass parts, and the mixture of 0.015 mass parts of photopolymerization initiator (trade name " Omnirad 184 ", manufactured by IGM Resins company), irradiate ultraviolet rays (polymerization reaction), obtain prepolymer composition (polymerization rate about 10% ) (The prepolymer composition contains unpolymerized monomer components).

Next, 100 parts by mass of the prepolymer composition, 0.08 parts by mass of 1,6-hexanediol diacrylate (HDDA), 1 part by mass of the second acrylic oligomer, and a silane coupling agent (trade name "KBM403") , Shin-Etsu Chemical Co., Ltd.) 0.3 parts by mass were mixed to prepare photocurable adhesive composition C2.

Next, the adhesive composition C2 was applied on the peeling-treated surface of the first peeling film that had undergone silicone peeling treatment on one side to form a coating film. The first release film is a polyethylene terephthalate (PET) film (trade name "DIAFOIL MRF#75", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) with one side treated with silicone release. Next, the coating film on the first release film is pasted to the release-treated surface of the second release film that has undergone silicone release treatment on one side. The second release film is a PET film (trade name "DIAFOIL MRF#75", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) with one side treated with silicone release. Next, ultraviolet rays are irradiated to the coating film through the second release film, and the coating film is cured by ultraviolet rays. Ultraviolet irradiation was performed using a black light lamp. The irradiation intensity of ultraviolet rays was set at 5 mW/cm ² . The adhesive sheet (thickness: 50 μm) of Comparative Example 1 was produced in the above manner.

[Comparative example 2] The adhesive sheet of Comparative Example 2 was produced in the same manner as the adhesive sheet of Comparative Example 1 except that the monomer composition was changed as shown in Table 1 in the preparation of the acrylic base polymer.

[Comparative example 3] The adhesive sheet of Comparative Example 3 was produced in the same manner as the adhesive sheet of Example 1 except that the monomer composition was changed as shown in Table 1 in the preparation of the acrylic base polymer.

＜Adhesion＞ About each adhesive sheet of Examples 1-6 and Comparative Examples 1-3, the adhesive force was investigated by the peeling test.

First, about each adhesive sheet, the required number of test pieces used for the peeling test before an autoclave process below, and the peeling test after an autoclave process were produced. In preparation of the test piece, first, the second peeling film was peeled off from the adhesive sheet, and a PET film (thickness: 25 μm) was bonded to the exposed surface of the adhesive layer exposed thereby to obtain a laminate. Next, a test piece (width 25 mm x length 100 mm) was cut out from this laminated body. Next, the first peeling film was peeled off from the adhesive layer of the test piece, and the exposed surface exposed by this was subjected to plasma treatment. On the other hand, plasma treatment was also performed on a polyimide film (trade name "GV200D", thickness 80 μm, manufactured by SKC Kolon PI) as an adherend. For each plasma treatment, a plasma irradiation device (trade name "AP-TO5", manufactured by Sekisui Kogyo Co., Ltd.) was used, with a voltage of 160 V, a frequency of 10 kHz, and a processing speed of 5000 mm/min. Then, the above-mentioned exposed surface of the adhesive layer of the test piece was bonded to the plasma-treated surface of the polyimide film. In this bonding, the test piece was pressure-bonded to the adherend by reciprocating a 2 kg roller once in an environment of 25°C.

[Peel test before autoclave treatment] After the above lamination, let it stand at 25°C for a specific time (2 minutes, 30 minutes), then implement a peel test of peeling the test piece from the polyimide film, and measure the peel strength as the adhesive force (N/25 mm) . In this measurement, a tensile testing machine (trade name "Autograph AGS-J", manufactured by Shimadzu Corporation) was used. In this measurement, the measurement temperature is set at 25°C, the peeling angle of the test piece relative to the adherend is set at 180°, the tensile speed of the test piece is set at 300 mm/min, and the peeling length is set at 50 mm ( Determination conditions of peel test). The adhesive force Xa after standing at 25°C for 2 minutes after bonding, the adhesive force Xd after standing at 25°C for 30 minutes after bonding, and the ratio of Xd to Xa (Xd/Xa) are shown in the table 1.

[Peel test after autoclave treatment] Within 3 minutes after the above lamination, start the autoclave treatment (heating and pressure treatment) of the test piece with the adherend attached. In the autoclave treatment, the temperature was set to 50° C., the pressure was set to 0.5 MPa, and the treatment time was set to 15 minutes. Then, immediately after the autoclave treatment, and after the autoclave treatment, after standing at 25°C for a specific time (12 hours, 24 hours, 72 hours, 120 hours, 168 hours, 336 hours), the same as before the autoclave treatment In the same manner as the above-mentioned peeling test, a peeling test under the above-mentioned measurement conditions was implemented. Adhesive force Xb after autoclaving and standing at 25°C for 72 hours, adhesive force Xc after autoclaving and standing at 25°C for 168 hours, ratio of Xb to Xa (Xb/Xa), and Table 1 shows the ratio (Xc/Xa) of Xc to Xa. In addition, the measurement results of the above-mentioned peeling test before and after the autoclave treatment are shown in the graph of FIG. 3 . In the figure, at each measurement time, the long bar on the left represents the adhesive force of the adhesive sheet of Comparative Example 1, and the long bar on the right represents the adhesive force of the adhesive sheet of Example 1.

＜Storage elastic modulus, loss tangent, and glass transition temperature＞ Dynamic viscoelasticity measurements were performed on the adhesive layers of the adhesive sheets of Examples 1-6 and Comparative Examples 1-3. Samples for measurement were prepared as follows. First, a plurality of adhesive layer sheets are pasted together to produce an adhesive sheet with a thickness of about 1.5 mm. Next, this sheet was punched to obtain cylindrical pellets (7.9 mm in diameter) as a sample for measurement. Then, the dynamic viscoelasticity measurement was performed on the measurement sample by using a dynamic viscoelasticity measurement device (trade name "Advanced Rheometric Expansion System (ARES)", manufactured by Rheometric Scientific Co., Ltd.) after being fixed to a jig of a parallel plate with a diameter of 7.9 mm. . In this measurement, the measurement mode was set to the twist mode, the measurement temperature range was set to -50°C to 150°C, the temperature increase rate was set to 5°C/min, and the frequency was set to 1 Hz. The storage elastic modulus G' (shear storage elastic modulus) and loss tangent tanδ at each temperature (shown in Table 1) were read from the measurement results. The storage elastic modulus Ma (kPa) at 25°C, the storage elastic modulus Mb (kPa) at 60°C, the storage elastic modulus Mc (kPa) at 85°C, and the storage elastic modulus Mb relative to the storage elastic modulus Ma Table 1 shows the ratio (Mb/Ma) and the ratio (Mc/Ma) of the storage modulus Mc to the storage modulus Ma. Also, the temperature at which the loss tangent tan δ becomes maximum is taken as the glass transition temperature of the adhesive sheet. Table 1 also shows the glass transition temperature (° C.).

＜Haze and total light transmittance＞ About the adhesive layer of each adhesive sheet of Examples 1-6 and Comparative Examples 1-3, haze and total light transmittance were investigated as follows. First, a sample for haze measurement is prepared. Specifically, after peeling off the second release film from the adhesive sheet, the adhesive layer side of the sheet (first release film, adhesive layer) is attached to an alkali-free glass (thickness 0.8-1.0 mm, total light transmission Ratio 92%, haze 0.4%, manufactured by Matsunami Glass Co., Ltd.), the first release film was peeled off from the adhesive layer on the glass. In this way, a sample for measurement is prepared. Next, using a haze measuring device (trade name "HM-150", manufactured by Murakami Color Technology Research Institute), the haze and total light transmittance of the adhesive layer of the sample were measured respectively. In this measurement, the sample for measurement was set in the apparatus so that light was irradiated from the non-alkali glass side. In addition, in this measurement, the measurement result measured only about the alkali-free glass under the same conditions was used as a reference line. Table 1 shows the haze and total light transmittance of the adhesive layer thus obtained.

＜Reworkability＞ About each adhesive sheet of Examples 1-6 and Comparative Examples 1-3, reworkability was examined as follows.

First, a test piece was prepared for each adhesive sheet. In preparation of the test piece, first, the second release film was peeled off from the adhesive sheet, and a PET film (thickness: 25 μm) was bonded to the exposed surface of the adhesive layer exposed thereby to obtain a laminate. Next, a test piece (width 25 mm x length 100 mm) was cut out from this laminated body. Next, the first peeling film was peeled off from the adhesive layer of the test piece, and the exposed surface exposed by this was subjected to plasma treatment. On the other hand, plasma treatment was also performed on a polyimide film (trade name "GV200D", thickness 80 μm, manufactured by SKC Kolon PI) as an adherend. For each plasma treatment, a plasma irradiation device (trade name "AP-TO5", manufactured by Sekisui Kogyo Co., Ltd.) was used, with a voltage of 160 V, a frequency of 10 kHz, and a processing speed of 5000 mm/min. Then, the above-mentioned exposed surface of the adhesive layer of the test piece was bonded to the plasma-treated surface of the polyimide film. In this bonding, the test piece was pressure-bonded to the adherend by reciprocating a 2 kg roller once in an environment of 25°C. Next, after standing still at 25° C. for 2 minutes, the end of the test piece on the adherend was pulled by hand to peel the test piece from the adherend (peeling operation). When peeling off, the angle formed by the adherend and the adhesive surface of the test piece is set to about 180 degrees. Then, regarding the reworkability of the adhesive sheet, the case where the test piece can be properly peeled off by the above-mentioned peeling operation without adhesive residue on the adherend is evaluated as "excellent", and the case where the adhesive sheet can be peeled despite the paste residue is evaluated as "excellent". The case where the test piece was not broken was evaluated as "good", and the case where the test piece was broken during the peeling operation or the case where it could not be peeled by hand was evaluated as "poor". In the above manner, the reworkability of the adhesive sheet 2 minutes after being attached to the adherend was evaluated. Table 1 shows the evaluation results of the reworkability (after 2 minutes).

On the other hand, except that the standing time was set to 30 minutes instead of 2 minutes, the test piece preparation to peeling operation was carried out in the same manner, and the reworkability of the adhesive sheet 30 minutes after sticking to the adherend was evaluated. Table 1 also shows the evaluation results of the reworkability (after 30 minutes).

＜Bending test＞ For each of the adhesive sheets of Examples 1 to 6 and Comparative Examples 1 to 3, the adhesiveness to the bent adherend (the extent to which peeling from the adherend is suppressed) was examined. Specifically, as follows.

First, laminate samples were produced for each adhesive sheet. In preparation of the laminate sample, first, the second release film was peeled off from the adhesive sheet, and the exposed surface (first exposed surface) exposed by this was subjected to plasma treatment. On the other hand, the polarizing plate of the polarizing plate with an adhesive layer attached to the polarizing plate with a thickness of 66 μm as the first adherend (a laminated structure of a polarizing plate with a thickness of 51 μm and an adhesive layer with a thickness of 15 μm) is exposed The surface is also treated with plasma. In each plasma treatment, a plasma irradiation device (trade name "AP-TO5", manufactured by Sekisui Kogyo Co., Ltd.) was used, the voltage was set to 160 V, the frequency was set to 10 kHz, and the processing speed was set to 5000 mm/min ( The same applies to the plasma treatment described below). Then, the above-mentioned first exposed surface of the adhesive sheet was bonded to the plasma-treated surface of the polarizing plate. In this lamination, the polarizing plate and the adhesive sheet were pressure-bonded by reciprocating a 2 kg roller once in an environment of 25°C. Next, the first release film was peeled from the adhesive sheet on the polarizing plate, and the exposed surface (second exposed surface) exposed by this was subjected to plasma treatment. On the other hand, plasma treatment was also performed on a polyimide film (trade name "GV200D", thickness 80 μm, manufactured by SKC Kolon PI) as the second adherend. Then, the above-mentioned second exposed surface of the adhesive sheet was bonded to the plasma-treated surface of the polyimide film. In this lamination, the polyimide film and the adhesive sheet were pressure-bonded by reciprocating a 2 kg roller once in an environment of 25°C. Next, a 125-μm-thick PET film treated with plasma was bonded to the adhesive layer of the polarizing plate with the adhesive layer by reciprocating a 2 kg roller once. In the above-mentioned manner, a laminated body sample was produced. The laminate sample has a laminated structure of a PET film, an adhesive layer, a polarizing plate, an adhesive sheet (the adhesive sheet of either Example or Comparative Example), and a polyimide film.

Next, the laminate sample was cut into a rectangle of 35 mm×100 mm so that the direction of the absorption axis of the polarizing plate was parallel to the direction of the long side. Next, the laminate sample was subjected to autoclave treatment (heating and pressure treatment) under the conditions of 50° C., 0.5 MPa, and 15 minutes. Next, a bending test was performed on the autoclaved laminate sample using a planar body no-load U-shaped stretch tester (manufactured by YUASA SYSTEM). In this test, for each of the two ends of the laminated body sample in the long side direction, a bending fixture is installed within 20 mm from the edge of the sample, and the laminated body sample is fixed on the testing machine (in the long side direction of the laminated body sample) The central 60 mm area is not fixed). Also, in this test, the laminate sample was held in a bent form with a bending radius of 1.3 mm and a bending angle of 180° so that the PET film side of the laminate sample was turned inside, and the sample in this state was kept at a temperature of 25°C and Keep in a constant temperature and humidity chamber with a relative humidity of 95% for 240 hours (the first bending test).

The laminate sample after such a first bending test was visually observed to check whether there was peeling between the polyimide film and the polarizing plate at the bent portion. In all the samples in which peeling was confirmed, peeling (void portion) occurred from the end in the short side direction of the laminate sample. For the laminate sample in which peeling was confirmed, the length (mm) of the void portion in the short side direction of the sample was measured. Then, with regard to the adhesiveness of the adhesive sheet to the bent adherend (the degree to which the peeling from the adherend is suppressed), the case where the length of the above-mentioned gap is less than 2 mm is evaluated as "excellent", and the above-mentioned The case where the length of the void portion is 2 mm or more is evaluated as “poor” (in this evaluation, when peeling (void portion) extending along the entire length of the laminate sample in the short side direction is confirmed, the length of the void portion It was set to 35 mm, and when peeling was not confirmed at all, the gap length was set to 0 mm). The evaluation results are shown in Table 1.

Moreover, the bending test (2nd bending test) was implemented in the same manner as the 1st bending test except having changed the holding temperature in the constant temperature and humidity chamber to 85 degreeC instead of 25 degreeC. Thereafter, the laminate sample after the second bending test was visually observed to check whether there was peeling between the polyimide film and the polarizing plate at the bent portion. Then, the adhesiveness of the adhesive sheet to the bent adherend was evaluated based on the same criteria as in the first bending test. The evaluation results are shown in Table 1.

[Table 1] Table 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative example 1 Comparative example 2 Comparative example 3 Acrylic base polymer 2EHA 70 75 65 60 70 70 56 60 - BA 20 15 25 30 20 20 - - 97 LA 8 8 8 8 8 8 34 36.5 - 4HBA 1 1 1 1 1 1 7 1 - NVP 0.6 0.6 0.6 0.6 0.6 0.6 2 2.5 - AAA - - - - - - - - 3 crosslinking agent Nyper-BMT-40SV 0.26 0.26 0.26 0.26 0.26 0.26 - - 0.26 Coronate L 0.02 0.02 0.02 0.02 0.02 0.02 - - 0.02 HDDA - - - - - - 0.08 0.08 - 1st acrylic oligomer 1.5 1.5 1.5 1.5 1.5 1.5 - - 1.5 2nd acrylic oligomer - - - - - - 1 1 - Silane coupling agent 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Adhesive layer thickness (μm) 50 50 50 50 25 100 50 50 50 Adhesion Xa(N/25mm) 7.5 7.3 8.1 8.7 6.2 9.5 8.8 - - Adhesion Xd(N/25 mm) 9.7 9.2 9.9 10.2 7.9 10.9 13.5 - - Adhesion Xb(N/25 mm) 21.1 21.6 21.8 22.2 18.2 23.6 15.2 - - Adhesion Xc(N/25 mm) 21.0 21.4 21.5 22.1 18.0 23.5 15.2 - - Xd/Xa 1.3 1.3 1.2 1.2 1.3 1.1 1.5 - - Xb/Xa 2.8 3.0 2.7 2.6 2.9 2.5 1.7 - - Xc/Xa 2.8 2.9 2.7 2.5 2.9 2.5 1.7 - - Storage elastic modulus Ma(kPa) at 25℃ 36 32 35 38 37 36 twenty four 18 80 Storage elastic modulus Mb(kPa) at 60℃ 27 25 27 29 27 27 15 9 60 Storage elastic modulus Mc(kPa) at 85℃ twenty two twenty three twenty four 25 twenty three twenty two 12 - - Mb/Ma 0.75 0.78 0.77 0.76 0.73 0.75 0.63 0.50 0.75 Mc/Ma 0.61 0.72 0.69 0.66 0.62 0.61 0.50 - - Glass transition temperature (°C) -45.7 -45.9 -45.3 -45.2 -45.4 -45.7 -42.6 -47.6 - Haze (%) 0.3 0.3 0.3 0.3 0.2 0.4 0.3 0.4 0.3 Total light transmittance (%) 92 92 92 92 92 92 92 92 92 Reworkability (after 2 minutes) excellent excellent excellent good excellent good excellent excellent bad Reworkability (after 30 minutes) excellent excellent excellent excellent excellent good bad excellent bad 1st bending test (25°C) excellent excellent excellent excellent excellent excellent excellent bad bad The second bending test (85°C) excellent excellent excellent excellent excellent excellent bad bad bad

10: Adhesive layer 21: 1st component 22: 2nd component L1: Release film L2: Release film S: Adhesive sheet (optical adhesive sheet for foldable devices) T: Thickness direction

Fig. 1 is a schematic cross-sectional view of an embodiment of the optical adhesive sheet of the present invention. 2A to 2C show an example of the method of using the optical adhesive sheet of the present invention. FIG. 2A shows the step of attaching the optical adhesive sheet to the first adherend, FIG. 2B shows the step of joining the first adherend and the second adherend via the optical adhesive sheet, and FIG. 2C shows the aging step. FIG. 3 is a graph showing the adhesive force of each adhesive sheet of Example 1 and Comparative Example 1. FIG.

10: Adhesive layer

L1: Release film

L2: Release film

S: Adhesive sheet (optical adhesive sheet for foldable devices)

T: Thickness direction

Claims (6)

An optical adhesive sheet for foldable devices, which has an adhesive layer, The above adhesive layer has a shear storage elastic modulus of not less than 20 kPa and not more than 50 kPa at 25°C, The above-mentioned adhesive layer has a first adhesive force Xa to the adherend at 25° C. after being attached to the adherend for the first time at 25° C. The above-mentioned adhesive layer was attached to the above-mentioned adherend, then subjected to heat and pressure treatment at 50°C and 0.5 MPa for 15 minutes, and then left at 25°C for 72 hours for the second time. The adherend has the second adhesive force Xb at 25°C, The first adhesive force Xa and the second adhesive force Xb satisfy 2.2≦Xb/Xa≦5. The optical adhesive sheet for foldable devices according to claim 1, wherein the adhesive layer is attached to the adherend, subjected to the heat and pressure treatment, and then left to stand for a third time at 25°C for 168 hours After that, the adherend has the third adhesive force Xc at 25°C, The first adhesive force Xa and the third adhesive force Xc satisfy 2.5≦Xc/Xa≦7. The optical adhesive sheet for a foldable device according to claim 1, wherein the adhesive layer is attached to the adherend at 25°C for 30 minutes and left for the fourth time, and then the adherend is placed at 25°C The following has the 4th adhesive force Xd, The first adhesive force Xa and the fourth adhesive force Xd satisfy 0.7≦Xd/Xa≦1.4. The optical adhesive sheet for foldable devices according to Claim 1, wherein the adhesive layer is placed on the adherend at 25° C. for 300 minutes and the fifth period of resting the adherend at 25° C. The minimum adhesive force Ya at ℃ is above 0.1 N/25 mm. The optical adhesive sheet for foldable devices according to claim 4, wherein the elapsed time Ta (minutes) from when the adhesive layer is attached to the adherend to when it has the minimum adhesive force Ya satisfies 0≦Ta≦100 . The optical adhesive sheet for foldable devices according to any one of claims 1 to 5, wherein the first adhesive force Xa is 0.1 N/25 mm or more and 10 N/25 mm or less.

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