Active energy beam curable adhesive sheet, adhesive sheet having a release film, laminate, method for manufacturing a laminate, laminated sheet, laminate for an image display device, flexible image display device, adhesive sheet for a flexible display and method for manufacturing a laminate for an image display device

Abstract

Even if the image display device component has a stepped portion on its surface, it can be filled to every corner by following the step, and the laminated structure formed by laminating the image display device component and the adhesive sheet can exhibit excellent resilience and durability even when bent in a high-temperature environment and excellent durability even when bent in a low-temperature environment, and the adhesive sheet has an adhesive layer containing a (meth)acrylic polymer (A), and satisfies the requirements of (1) to (3) below. (1) The thickness is 0.8 mm to 1.5 mm, and the warping (creep deformation) is 50% or more when a pressure of 1000 Pa is applied at a temperature of 25°C for 3600 seconds. (2) When the thickness is set to 0.8 mm to 1.5 mm and an integrated light intensity of 2,000 to 4,000 mJ / cm² is applied using an active energy line with a wavelength of 365 nm, the warping (creep deformation) becomes 10% or more when a pressure of 1,000 Pa is applied at a temperature of 80°C for 180 seconds. (3) When an active energy line with a wavelength of 365 nm is applied using an integrated light intensity of 2,000 to 4,000 mJ / cm², the recovery rate after 200% deformation at 25°C, expressed by the following formula, becomes 60% or more. Recovery rate (%) = {(xy) / x} × 100 (where x is the initial warping applied in the shear direction to an adhesive sheet with a thickness of 0.8 mm to 1.5 mm, and y is the residual warping after 600 seconds have elapsed following release after the initial warping has been applied for 600 seconds.)

Description

Technology Field

[0001] The present invention relates to an adhesive sheet suitable for use in an image display device having a curved surface or a flexible image display device capable of being folded. In particular, the invention relates to an adhesive sheet suitable for use in laminating a member for configuring an image display device having a step portion on the lamination surface, an adhesive sheet having a release film using said adhesive sheet, a laminate, a method for manufacturing a laminate, a laminated sheet, a laminate for an image display device, a flexible image display device, an adhesive sheet for a flexible display, and a method for manufacturing a laminate for an image display device. Background Technology

[0002] Recently, image display devices including curved sections using organic light-emitting diodes (OLEDs) or quantum dots (QDs), and flexible image display devices capable of folding or winding, have been developed and are being widely commercialized.

[0003] In such a display device, a plurality of sheet members, such as a cover lens, a circular polarizer, a touch film sensor, and a light-emitting element, have a laminated structure in which they are bonded together with a transparent adhesive sheet, and when focusing on any of the adhesive sheets, the members and the adhesive sheet can be considered as a laminate.

[0004] Regarding flexible image display devices capable of bending or winding, various problems arise due to interlayer stress when bent. For example, there are cases where delamination occurs between layers when folded (delamination, the phenomenon of delamination between layers is called "delamy"), so a laminate that does not delaminate even when folded is required.

[0005] In addition, a laminated body is required that quickly restores to a flat state when the screen is opened from a folded state.

[0006] Additionally, during repeated folding or winding operations, stress is applied to the substrate of the adhesive sheet, causing cracks and eventually fracture; therefore, there is a requirement for a laminate that is durable, especially during repeated folding operations at low temperatures.

[0007] Regarding a foldable flexible image display device, for example, Patent Document 1 discloses an adhesive and adhesive sheet for a repetitive bending device, and a bending laminate member and a repetitive bending device, wherein the value obtained by multiplying the creep compliance variation value and the relaxation elastic modulus variation value is set to a preferred range, and the adhesive exhibits high resilience that suppresses deformation of the adhesive layer and mitigates the effect of being placed in a bending state after being released from the bending state when placed in a bending state for a long period of time. Prior art literature

[0008] Japanese Patent Publication No. 2019-123826 The problem to be solved

[0009] Even if the value obtained by multiplying the creep compliance variation value and the relaxation modulus variation value of the adhesive sheet is controlled to a desirable range at room temperature as disclosed in Patent Document 1, when a folding operation is performed at a high temperature, the effect of being placed in a bent state remains, resulting in insufficient recovery, or when a repeated folding operation is performed at a low temperature, stress is applied to the member that is the adherend to the adhesive sheet, so there were cases where problems such as the member breaking occurred.

[0010] Since a device including an adhesive sheet is intended to be used at high temperatures caused by heat generation of the device, or at high and low temperatures depending on the environment such as region or season, the adhesive sheet is required to have properties that stably exhibit resilience or durability over a wide temperature range.

[0011] In addition, the surface of a component constituting an image display device (also referred to as an "image display device component") may have irregularities formed by wiring, printing, pattern development, or surface treatment. An adhesive sheet for bonding an image display device component having such a stepped portion is required to have high fluidity because, under the limitation that it cannot be made thick due to the desire for thinning of the image display device, if it is thin and cannot fill every corner following the stepped portion, air bubbles may form inside the adhesive layer.

[0012] However, in adhesive sheets with high fluidity when laminated, it was difficult to stably exhibit resilience or durability over a wide temperature range.

[0013] Therefore, the present invention aims to provide an adhesive sheet capable of exhibiting excellent resilience and durability even when subjected to bending operations in a high-temperature environment, and excellent durability even when subjected to bending operations in a low-temperature environment, and a method for manufacturing the same, wherein the laminate comprises a configuration in which an image display device component is laminated with an adhesive sheet, and is capable of filling every corner by following the step so that no bubbles are generated even when an image display device component is provided with a step portion on its surface. means of solving the problem

[0014] The present invention proposes an active energy beam curable adhesive sheet having an adhesive layer comprising a (meth)acrylic polymer (A) and satisfying the requirements of (1) to (3) below.

[0015] (1) The thickness is 0.8 mm to 1.5 mm, and the warping (creep deformation) is 50% or more when a pressure of 1000 Pa is applied at a temperature of 25°C for 3600 seconds.

[0016] (2) When the thickness is 0.8 mm to 1.5 mm and an integrated light intensity of 2000 to 4000 mJ / cm² is applied with an active energy line of wavelength 365 nm, and a pressure of 1000 Pa is applied for 180 seconds at a temperature of 80°C, the warping (creep deformation) is 10% or more.

[0017] (3) When an active energy line of wavelength 365 nm is irradiated with an integrated light intensity of 2000~4000 mJ / cm², the recovery rate after 200% deformation at 25°C, expressed by the following formula, is 60% or more.

[0018] Restoration rate (%) = {(xy) / x} × 100

[0019] (x is the initial twist applied in the shear direction to an adhesive sheet with a thickness of 0.8 mm to 1.5 mm, and y is the residual twist after 600 seconds have elapsed following the release of the initial twist applied for 600 seconds.)

[0020] The present invention also proposes an adhesive sheet comprising a release film having a configuration in which the active energy beam curable adhesive sheet proposed by the present invention and the release film are laminated.

[0021] The present invention also proposes a laminate having a configuration in which a release film and a member for configuring an image display device having a height difference of 2 μm or more on the laminated surface are laminated with the active energy beam curable adhesive sheet proposed by the present invention interposed therein.

[0022] The present invention also proposes a method for manufacturing a laminate, wherein a release film and a member for configuring an image display device having a height difference of 2 μm or more on the laminated surface are laminated with the active energy beam curable adhesive sheet proposed by the present invention interposed therein, and active energy beam irradiation is performed on the adhesive sheet by passing the release film through the release film from the release film side.

[0023] The present invention also proposes a laminated sheet having a configuration in which the active energy beam curable adhesive sheet proposed by the present invention and another adhesive sheet are laminated.

[0024] The present invention also proposes a laminate for an image display device having a configuration in which two image display device components are laminated with the active energy beam curable adhesive sheet proposed by the present invention interposed therebetween, and at least one of the image display device components has a step difference of 2 μm or more on the contact surface with the adhesive sheet.

[0025] The present invention also relates to an adhesive sheet for a flexible display having an adhesive layer comprising a (meth)acrylic polymer (A), wherein

[0026] The thickness is 15㎛ or more and 50㎛ or less, and

[0027] A flexible display adhesive sheet is proposed that has active energy beam curability and is characterized by not having foaming around the step when bonded to a member for configuring an image display device having a step of 2 to 10 μm at a spacing of 10 mm or less under the following bonding conditions.

[0028] (Joining conditions)

[0029] a) Ultraviolet light is irradiated onto an adhesive sheet with a thickness of 15 to 50 μm so that the total light intensity of 365 nm is 2000 to 4000 mJ / cm².

[0030] b) The adhesive sheet is vacuum-bonded to the surface of a substrate having a step difference of 2 to 10 μm at intervals of 10 mm or less, under conditions of a press pressure of 0.2 MPa and 30 seconds.

[0031] c) Autoclave treatment is performed under conditions of 70℃, atmospheric pressure of 0.45 MPa, and 20 minutes.

[0032] The present invention also relates to a method for manufacturing a laminate for an image display device having a configuration in which two image display device constituent members 1 and 2 are laminated with an active energy beam curable adhesive sheet interposed therebetween,

[0033] A method for manufacturing a laminate for an image display device is proposed, characterized by having the following processes 1 to 3, performing processes 1 and 2, and then performing process 3.

[0034] Process 1: One surface of the active energy beam curable adhesive sheet proposed by the present invention is laminated to a member 1 for configuring an image display device.

[0035] Process 2: Irradiate with an active energy beam and cure the active energy beam curable adhesive sheet proposed by the present invention.

[0036] Process 3: A member 2 for configuring an image display device is laminated to the other surface of the adhesive sheet to form a laminate. Effects of the invention

[0037] The adhesive sheet proposed by the present invention can fill every corner by following the step, so that even if there is a step on the adhesive surface of the image display device component to be adhered to, bubbles will not be generated.

[0038] Additionally, the adhesive sheet proposed by the present invention, having a laminated structure in which the adhesive sheet and an image display device component are laminated, can exhibit excellent resilience and durability even when subjected to bending operations in a high-temperature environment, and can exhibit excellent durability even when subjected to bending operations in a low-temperature environment.

[0039] Therefore, for example, the laminate can exhibit excellent durability or resilience even when folded, bent, or wound in high and low temperature environments.

[0040] In light of the above, the adhesive sheet proposed by the present invention can be suitably used, for example, as an adhesive sheet for a flexible display. Specific details for implementing the invention

[0041] Next, the present invention will be explained based on exemplary embodiments. However, the present invention is not limited to the embodiments described below.

[0042] <This adhesive sheet>

[0043] An adhesive sheet (referred to as "this adhesive sheet") related to one embodiment of the present invention is an active energy beam curable adhesive sheet having an adhesive layer (referred to as "this adhesive layer") which is particularly included as a main component resin comprising a (meth)acrylic polymer (A).

[0044] The adhesive layer of the adhesive sheet can be formed from an adhesive composition (referred to as "the adhesive composition") that, for example, comprises a (meth)acrylic polymer (A), particularly comprises a (meth)acrylic polymer (A) as the main component resin, preferably comprises a crosslinking agent (B) and / or a polymerization initiator (C), and additionally comprises other components as needed.

[0045] The above "active energy beam curable adhesive sheet" means an adhesive sheet having the property of being curable by an active energy beam; in other words, an adhesive sheet having active energy beam curability that leaves room for curing by an active energy beam.

[0046] The adhesive sheet may be cured in a state where there is room to be cured by an active energy beam (also referred to as "pre-cured"), or not cured at all (referred to as "uncured"), and may also be curable by an active energy beam.

[0047] If the adhesive sheet is partially cured or uncured, the adhesive sheet can be cured by an active energy beam (also referred to as "full curing") before or after bonding the adhesive sheet to a substrate, and as a result, the adhesive strength can be increased by increasing the cohesive strength.

[0048] In addition, the term "main component resin" above refers to the resin having the highest mass ratio among the resins constituting the adhesive layer or the adhesive composition. The content of the main component resin may be 70 mass% or more, and among the resins constituting the adhesive layer or the adhesive composition, 80 mass% or more, or 90 mass% or more (including 100 mass%).

[0049] Creep Characteristics

[0050] The adhesive sheet has a thickness of 0.8 mm to 1.5 mm, and it is preferable that the warping (creep deformation) is 50% or more when a pressure of 1000 Pa is applied at a temperature of 25°C for 3600 seconds.

[0051] In the present adhesive sheet, the creep deformation of 50% or more when a pressure of 1000 Pa is applied at a temperature of 25°C for 3600 seconds in the pre-curing state indicates that it is easy to deform in this state, so it is desirable that it can follow even the corners of the stepped portion even if the surface of the image display device component to be adhered to has irregularities.

[0052] In this regard, it is preferable that the creep deformation of the adhesive sheet be 50% or more, and among them 100% or more, among them 105% or more, and particularly 110% or more.

[0053] Meanwhile, regarding the upper limit, it is desirable that the creep deformation be 10,000% or less in terms of maintaining the shape at room temperature or below.

[0054] In this regard, the creep deformation of the adhesive sheet is more preferably 5000% or less, and more preferably 2500% or less, and furthermore 1000% or less, and more preferably 500% or less, and particularly 250% or less.

[0055] As mentioned above, the creep deformation of the adhesive sheet is a value when the thickness is 0.8 mm to 1.5 mm. However, in order to accurately measure the creep deformation of the adhesive sheet, it is necessary to avoid variations in the measurement results caused by the influence of the measurement jig due to insufficient thickness of the adhesive sheet. To do so, it is necessary to measure after adjusting the adhesive sheet to a certain thickness range.

[0056] By pre-adjusting the thickness of the adhesive sheet to within the above range and then measuring the creep deformation, the creep deformation of the adhesive sheet can be accurately determined without being affected by the measurement jig.

[0057] In addition, the phrase “to have a thickness of 0.8 mm to 1.5 mm” means that if the thickness of the adhesive sheet used as the measurement sample does not satisfy this range, the thickness of the measurement sample is adjusted to this range by overlapping several sheets, etc. The same applies even if the thickness of the measurement sample is specified in other tests.

[0058] In the adhesive sheet, in order to adjust the creep deformation to the above range, it is preferable to adjust the composition or molecular weight of the (meth)acrylic polymer (A), or to adjust the type or amount of crosslinking agent (B). However, this is not limited to these means.

[0059] In addition, the adhesive sheet has a thickness of 0.8 mm to 1.5 mm, and it is desirable that the distortion (creep deformation) is 10% or more when an integrated light intensity of 2000 to 4000 mJ / ㎠ is applied after irradiating an active energy line of wavelength 365 nm, and a pressure of 1000 Pa at a temperature of 80°C is applied for 180 seconds.

[0060] The fact that the adhesive sheet has a warping (creep deformation) of 10% or more when a pressure of 1000 Pa is applied for 180 seconds at a temperature of 80°C after curing indicates that it is prone to deformation in a heated state even after curing. Therefore, even if the surface of the image display device component to be adhered to has irregularities, heating after curing allows it to further follow the step portion to every corner and absorb the step portion until the surface becomes smooth.

[0061] In this regard, it is more desirable for the creep deformation after active energy beam hardening to be 10% or more, and among them 20% or more, and among them 30% or more, and 40% or more.

[0062] Meanwhile, regarding the upper limit of the warping (creep deformation) after curing, if it is excessively high, there is a risk that the adhesive sheet will protrude from the cross-section of the laminate under a high-temperature environment, causing the cross-section to become sticky, causing cohesive peeling when folded, or damaging the restorability when opened from the folded state; therefore, it is preferable that it be 500% or less, more preferable that it be 300% or less, more preferable that it be 100% or less, particularly preferable that it be 80% or less, and most preferable that it be 60% or less.

[0063] In addition, regarding the creep deformation of the adhesive sheet after active energy beam curing, as described above, the thickness of the adhesive sheet is adjusted to 0.8 mm to 1.5 mm and then measured, but this reason is to take into account the influence of the measurement jig as described above, and it is not intended to require the thickness of the adhesive sheet to be within the above range.

[0064] In order to adjust the creep deformation after active energy beam curing of the adhesive sheet to the above range, it is preferable to adjust the composition or molecular weight of the base polymer (meth)acrylic polymer (A) described later, the type or amount of crosslinking agent (B) added, or the amount of irradiation of the active energy beam. However, this is not limited to these means.

[0065] <Resilience>

[0066] It is preferable that the adhesive sheet has a recovery rate of 60% or more after 200% deformation at 25°C, represented by the following formula, when irradiated with an active energy line of wavelength 365 nm at an integrated light intensity of 2000 to 4000 mJ / cm².

[0067] The restoration rate is expressed by the following formula.

[0068] Restoration rate (%) = {(xy) / x} × 100

[0069] (x is the initial twist applied in the shear direction to an adhesive sheet with a thickness of 0.8 mm to 1.5 mm, and y is the residual twist after 600 seconds have elapsed following the release of the initial twist applied for 600 seconds. More specific measurement methods are described in the Examples.)

[0070] If the recovery rate of the adhesive sheet after curing is 60% or higher, permanent deformation can be suppressed, and the recovery ability when opened from a folded state is also good. From this perspective, it is preferable that the recovery rate be 70% or higher, and among them 75% or higher, and among them 80% or higher is more preferable.

[0071] In addition, regarding the recovery rate of the adhesive sheet above, as described above, the thickness of the adhesive sheet is adjusted to 0.8 mm to 1.5 mm and then measured; however, this reason is to take into account the influence of the measuring jig as described above, and it is not intended to require that the thickness of the adhesive sheet be within the above range.

[0072] Gel fraction

[0073] It is preferable that the adhesive sheet be in an uncrosslinked or slightly crosslinked state, that is, a state in which the gel fraction is 0% or more and 20% or less, before being cured by an active energy beam.

[0074] From the perspective of conformability to irregularities on the substrate surface, it is more preferable for the gel fraction to be 10% or less, more preferable for it to be 8% or less, and more preferable for it to be 5% or less.

[0075] In addition, when the adhesive sheet is cured by irradiating an active energy line of wavelength 365 nm with an integrated light intensity of 2000 to 4000 mJ / cm², the gel fraction increases compared to before curing, and it is desirable that the gel fraction be 10% or more and 85% or less.

[0076] By having a gel fraction of 10% or more after active energy beam curing, shape stability of the adhesive sheet, or resilience and durability when folded in a laminate can be provided.

[0077] From this perspective, it is desirable that the gel fraction after active energy beam curing be 10% or more, and among them 30% or more, and among them 40% or more is more desirable.

[0078] Meanwhile, it is desirable that the gel fraction after active energy beam curing be 85% or less.

[0079] In addition, when laminating the adhesive sheet after active energy beam curing, if the gel fraction after active energy beam curing is not excessively high, it has a certain degree of flexibility, so even if the substrate is a component of an image display device having a stepped portion on its surface, it can be filled to every corner by following the step without generating bubbles. From this perspective, it is more preferable that the gel fraction after active energy beam curing is 70% or less, and among them, 60% or less, and among them, 55% or less is even more preferable.

[0080] In addition, the adhesive sheet may be such that even when cured by irradiating an active energy line of 365 nm wavelength with an integrated light intensity of 1000 mJ / cm², the gel fraction does not change compared to before curing or increases by less than 0.5%.

[0081] The adhesive sheet may have low light sensitivity as described above.

[0082] In order to prepare the gel fraction after curing in the present adhesive sheet to be within the above range, it is preferable to adjust the composition or molecular weight of the base polymer (meth)acrylic polymer (A), adjust the type or amount of crosslinking agent (B), or adjust the intensity or integrated amount of irradiated active energy rays. However, this is not limited to these means.

[0083] <Adhesion>

[0084] The adhesive sheet is preferably to have the following (4) characteristics.

[0085] (4) Adhesion to a soda-lime glass surface at 23°C, 50% RH, peel angle 180°, peel speed 300 mm / min is 1 N / cm or more

[0086] If the adhesive strength is 1 N / cm or more, it is desirable because it facilitates positioning or temporary fixing when bonding the image display device components described later.

[0087] In this regard, the adhesive strength is preferably 1 N / cm or more, more preferably 2 N / cm or more, more preferably 4 N / cm or more, particularly preferably 5 N / cm or more, and more preferably 10 N / cm or more. In addition, the upper limit is typically 40 N / cm.

[0088] The adhesive sheet is also preferably to have the following (5) characteristics.

[0089] (5) After laminating the adhesive sheet to the soda-lime glass, the adhesive strength on the surface of the soda-lime glass at 23°C, 50% RH, peeling angle 180°, and peeling speed 300 mm / min is 1 N / cm or more when irradiated with an active energy line of wavelength 365 nm at an integrated light intensity of 2000 to 4000 mJ / cm².

[0090] If the adhesive strength is 1 N / cm or more, it is desirable because when bonded with the image display device component described later to form a laminate, it does not cause dilamina during bending and has good durability.

[0091] In this regard, the adhesive strength when irradiated with an active energy beam after lamination to soda-lime glass is preferably 1 N / cm or more, more preferably 2 N / cm or more, more preferably 3 N / cm or more, and more preferably 5 N / cm or more. In addition, the upper limit is typically 40 N / cm.

[0092] The adhesive sheet is also preferably to have the following (6) characteristics.

[0093] (6) When the adhesive sheet is laminated to soda-lime glass after irradiating an active energy line of wavelength 365 nm with an integrated light intensity of 2000 to 4000 mJ / cm², the adhesive strength on the surface of the soda-lime glass at 23°C, 50% RH, a peel angle of 180°, and a peel speed of 300 mm / min is 1 N / cm or more.

[0094] If the adhesive strength is 1 N / cm or more, it is desirable because when bonded with the image display device component described later to form a laminate, it does not cause dilamina or the like during bending and has good durability.

[0095] In this regard, the adhesive strength when the adhesive sheet is laminated to soda-lime glass after active energy beam curing is preferably 1 N / cm or more, more preferably 2 N / cm or more, more preferably 3 N / cm or more, and more preferably 5 N / cm or more. In addition, the upper limit is typically 40 N / cm.

[0096] Loss tangent (tanδ)

[0097] The adhesive sheet has a thickness of 0.8 mm to 1.5 mm, and it is preferable that the loss tangent obtained by measuring dynamic viscoelasticity in a shear mode at a frequency of 1 Hz is 0.8 or higher at -30°C. More preferably, it is 1 or higher, among which 1.2 or higher, more preferably 1.5 or higher, and more preferably 2.0 or lower, more preferably 1.8 or lower.

[0098] It is desirable that the loss tangent (tanδ) of the adhesive sheet is within the above range, so that even if the substrate has irregularities on the surface, the adhesive resin can flow and fill the stepped portion by heating.

[0099] In addition, the adhesive sheet is preferably 0.8 mm to 1.5 mm thick after active energy ray curing, that is, after irradiating an active energy ray of wavelength 365 nm with an integrated light amount of 2000 to 4000 mJ / cm², and the loss tangent obtained by measuring dynamic viscoelasticity in a shear mode of wavenumber 1 Hz is preferably 0.5 to 2.3 in the range of -30°C to -10°C.

[0100] Since the loss tangent (tanδ) after curing is within the above range, it is desirable that even when a laminate using the adhesive sheet is folded in a low-temperature environment, there is no risk of delamination or buckling of the interface of the image display device components or cracking of the image display device components. In this regard, the loss tangent (tanδ) in the range of -30°C to -10°C is preferably 0.5 to 2.3, more preferably 0.8 to 2.0, and more preferably 1.1 to 1.9.

[0101] In addition, in the present invention, the adhesive sheet has a thickness of 0.8 mm to 1.5 mm, and the maximum point of the loss tangent obtained when dynamic viscoelasticity is measured in a shear mode at a frequency of 1 Hz is preferably -20°C or lower.

[0102] It is desirable that the maximum point of the loss tangent be -20°C or lower, as this allows for durability during bending when the structure is made into a laminate. In this regard, the maximum point of the loss tangent is more preferably -25°C or lower, more preferably -30°C or lower, more preferably -33°C or lower, and particularly preferably -35°C or lower. In addition, the lower limit is typically -60°C or higher.

[0103] In addition, regarding the loss tangent before or after curing of the adhesive sheet, as described above, the thickness of the adhesive sheet is adjusted to 0.8 mm to 1.5 mm and then measured, but this reason is to take into account the influence of the measuring jig as described above, and it is not intended to require the thickness of the adhesive sheet to be within the above range.

[0104] In order to adjust the loss tangent (tanδ) of the adhesive sheet before or after curing, it is preferable to adjust the composition or molecular weight of the base polymer (meth)acrylic polymer (A) described below, the type or amount of crosslinking agent (B) added, or the amount of irradiation of the active energy beam. However, this is not limited to these means.

[0105] Storage Modulus (G')

[0106] The adhesive sheet is preferably 0.8 mm to 1.5 mm thick, and has a storage modulus (G') of 0.01 to 0.2 MPa obtained by measuring dynamic viscoelasticity in a shear mode at a temperature of 25°C and a frequency of 1 Hz.

[0107] Since the storage modulus (G') of the adhesive sheet is within this range, even if the surface of the substrate has irregularities, effects such as being able to follow the irregularities and absorb the irregularities can be obtained.

[0108] In this regard, the storage modulus (G') of the adhesive sheet is preferably 0.01 MPa or more and 0.2 MPa or less at a temperature of 25°C and a frequency of 1 Hz, and is preferably 0.02 MPa or more or 0.1 MPa or less, and is more preferably 0.03 MPa or more or 0.09 MPa or less.

[0109] In addition, the adhesive sheet is preferably 0.8 mm to 1.5 mm thick after active energy ray curing, that is, after irradiating an active energy ray with a wavelength of 365 nm with an integrated light intensity of 2000 to 4000 mJ / cm², and has a storage modulus (G') obtained by measuring dynamic viscoelasticity in a shear mode at a temperature of 25°C and a frequency of 1 Hz, which is 0.02 MPa or more and 0.24 MPa or less.

[0110] Since the storage modulus (G') of the adhesive sheet after curing is within this range, when it is laminated with the image display device component described later to form a laminate, it does not cause dilamina or the like when folded and has good durability.

[0111] In this regard, the storage modulus (G') of the adhesive sheet after curing is preferably 0.02 MPa or more and 0.24 MPa or less at a temperature of 25°C and a frequency of 1 Hz, and more preferably 0.03 MPa or more and 0.20 MPa or less, and more preferably 0.04 MPa or more and 0.10 MPa or less.

[0112] In addition, regarding the storage modulus (G') of the adhesive sheet before or after curing, as described above, the thickness of the adhesive sheet is adjusted to 0.8 mm to 1.5 mm and then measured, but this reason is to take into account the influence of the measuring jig as described above, and it is not intended to require the thickness of the adhesive sheet to be within the above range.

[0113] In order to adjust the storage modulus (G') of the adhesive sheet before or after curing, it is preferable to adjust the composition or molecular weight of the base polymer (meth)acrylic polymer (A) described below, the type or amount of crosslinking agent (B) added, or the amount of irradiation of active energy rays. However, this is not limited to these means.

[0114] <This adhesive composition>

[0115] The adhesive composition is a composition comprising a (meth)acrylic polymer (A), preferably a crosslinking agent (B) and / or a polymerization initiator (C), and additionally, other components as needed.

[0116] <(Meta)acrylic polymer(A)>

[0117] The adhesive composition contains a (meth)acrylic polymer (A), and in particular, contains it as a main component resin.

[0118] That is, the (meth)acrylic polymer (A) is the resin with the highest mass ratio among the resins constituting the adhesive composition. At this time, among the resins constituting the adhesive composition, the mass ratio of the (meth)acrylic polymer (A) may be 50 mass% or more, 70 mass% or more, 80 mass% or more, and 90 mass% or more (including 100 mass%).

[0119] The above (meth)acrylic polymer (A) comprises a structural unit derived from a compound represented by the following formula 1 (wherein R1 represents a hydrogen atom or a methyl group, and R2 represents a straight-chain or branched alkyl group or alicyclic hydrocarbon having 4 to 18 carbon atoms), and it is preferable to polymerize a polymer component containing 50 mass% or more of the monomer component.

[0120] Among them, the (meth)acrylic polymer (A) is more preferably polymerized by including 55 mass% or more of the monomer component as a polymerization component, and among them, it is particularly preferable to polymerize by including 60 mass% or more.

[0121] In addition, in the present invention, "(meth)acryl" encompasses acrylic and methacryl, "(meth)acryloyl" encompasses acryloyl and methacryloyl, and "(meth)acrylate" encompasses acrylate and methacrylate, respectively, and "(co)polymer" encompasses polymer and copolymer.

[0122]

[0123] As monomers represented by Formula 1 above, for example, n-butyl(meth)acrylate, isobutyl(meth)acrylate, sec-butyl(meth)acrylate, t-butyl(meth)acrylate, pentyl(meth)acrylate, isopentyl(meth)acrylate, neopentyl(meth)acrylate, hexyl(meth)acrylate, cyclohexyl(meth)acrylate, heptyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, nonyl(meth)acrylate, isononyl(meth)acrylate, t-butylcyclohexyl(meth)acrylate, decyl(meth)acrylate, Examples include isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, isobornyl (meth)acrylate, 3,5,5-trimethylcyclohexane (meth)acrylate, dicyclofentanyl (meth)acrylate, dicyclofentenyl (meth)acrylate, etc. These may be used in combination of one or more types. Among the above, it is particularly preferable to include one or more of butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, and lauryl (meth)acrylate.

[0124] The above (meth)acrylic polymer (A) is preferably a copolymer having a “other copolymerizable monomer” other than the monomer component as a copolymer component.

[0125] The above “other copolymer monomer” is preferably included in an amount of 1 to 30 mass% in the (meth)acrylic polymer (A), and more preferably included in an amount of 2 mass% or more or 25 mass% or less.

[0126] The "other copolymerizable monomers" in question include, for example: (a) a carboxyl group-containing monomer (hereinafter also referred to as "copolymerizable monomer a1"), (b) a hydroxyl group-containing monomer (hereinafter also referred to as "copolymerizable monomer a2"), (c) an amino group-containing monomer (hereinafter also referred to as "copolymerizable monomer a3"), (d) an epoxy group-containing monomer (hereinafter also referred to as "copolymerizable monomer a4"), (e) an amide group-containing monomer (hereinafter also referred to as "copolymerizable monomer a5"), (f) a vinyl monomer (hereinafter also referred to as "copolymerizable monomer a6"), (g) a (meth)acrylate monomer of an alkyl group having 1 to 3 carbon atoms (hereinafter also referred to as "copolymerizable monomer a7"), (h) a macro monomer (hereinafter also referred to as "copolymerizable monomer a8"), (i) an aromatic group-containing monomer (hereinafter Examples include (referred to as “cosynthetic monomer a9”) or (j) other functional group-containing monomers (hereinafter referred to as “cosynthetic monomer a10”). One or more of these may be combined.

[0127] As the above copolymer monomer a1, for example, (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypropyl (meth)acrylate, carboxybutyl (meth)acrylate, ω-carboxypolycaprolactone mono(meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethylphthalic acid, 2-(meth)acryloyloxypropylphthalic acid, 2-(meth)acryloyloxyethylmaleic acid, 2-(meth)acryloyloxypropylmaleic acid, 2-(meth)acryloyloxyethylsuccinic acid, 2-(meth)acryloyloxypropylsuccinic acid, crotonic acid, fumaric acid, Examples include maleic acid and itaconic acid. One or more of these may be combined.

[0128] Examples of the copolymer monomer a2 above include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-1-methylethyl acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycerin mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol polypropylene glycol mono(meth)acrylate, polyethylene glycol polybutylene glycol mono(meth)acrylate, polypropylene glycol polybutylene glycol mono(meth)acrylate, and hydroxyphenyl (meth)acrylate. There are. These may be combined in one or more types.

[0129] Examples of the copolymer monomer a3 above include aminoalkyl(meth)acrylates such as aminomethyl(meth)acrylate, aminoethyl(meth)acrylate, aminopropyl(meth)acrylate, and aminoisopropyl(meth)acrylate; N-alkylaminoalkyl(meth)acrylates such as N,N-dialkylaminoalkyl(meth)acrylates; and N,N-dialkylaminoalkyl(meth)acrylates such as N,N-dimethylaminoethyl(meth)acrylate and N,N-dimethylaminopropyl(meth)acrylate. One or more of these may be combined.

[0130] Examples of the copolymer monomer a4 above include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate glycidyl ether. One or more of these may be combined.

[0131] Examples of the copolymer monomer a5 above include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, diacetone(meth)acrylamide, maleic acid amide, and maleimide. One or more of these may be combined.

[0132] Examples of the copolymerized monomer a6 above include compounds having vinyl groups within the molecule. Examples of such compounds include functional monomers having functional groups such as alkoxyalkyl groups, such as ethoxydiethylene glycol acrylate, methoxytriethylene glycol acrylate, methoxypolyethylene glycol acrylate, methoxydipropylene glycol acrylate, and methoxypolypropylene glycol acrylate; polyalkylene glycol di(meth)acrylates; vinyl ester monomers such as vinyl acetate, N-vinyl-2-pyrrolidone, vinyl propionate, and vinyl laurate; and aromatic vinyl monomers such as styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrenes. One or more of these may be combined.

[0133] Examples of the copolymer monomer a7 mentioned above include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, etc. One or more of these may be combined.

[0134] The macromonomer as the copolymer monomer a8 above is a high molecular weight monomer having terminal functional groups and high molecular weight backbone components.

[0135] When the above “other copolymerized monomer” is copolymerized monomer a8, the above (meth)acrylic polymer (A) is a copolymer containing structural units derived from macromonomers.

[0136] The backbone component of the above macromonomer is preferably composed of an acrylic acid ester polymer or a vinyl polymer. Examples include the above (meth)acrylate having a straight or branched alkyl group having 4 to 18 carbon atoms, the above copolymer monomer a1, the above copolymer monomer a2, the above copolymer monomer a6, the above copolymer monomer a7, etc., and these can be used alone or in combination of two or more types.

[0137] The number average molecular weight of the macromonomer is preferably 1,000 or more, more preferably 1,500 or more, and even more preferably 2,000 or more. In addition, the upper limit of the number average molecular weight is typically 20,000.

[0138] In the present adhesive composition, the macro monomer is a copolymerized macro monomer having a straight-chain or branched alkyl group having 1 to 3 carbon atoms, which is preferred because it can improve processability and storage stability.

[0139] The number average molecular weight of these macromonomers is preferably 1,000 to 10,000, particularly preferably 1,500 or more or 5,000 or less, more preferably 2,000 or more or 4,000 or less.

[0140] In addition, the above macromonomer is a copolymerized macromonomer of a (meth)acrylate having a straight-chain or branched alkyl group having 8 to 18 carbon atoms, so it is good because it can achieve good irregularity-following properties even when there are irregularities on the surface of the substrate.

[0141] The number average molecular weight of these macromonomers is preferably 2000 to 20000, particularly preferably 3000 or more or 15000 or less, more preferably 4000 or more or 10000 or less.

[0142] By using copolymerizing monomer a8, a macromonomer can be introduced as a branching component of the graft copolymer, and a (meth)acrylic acid ester copolymer can be used as the graft copolymer. For example, a (meth)acrylic polymer (A) can be formed by a copolymer containing structural units derived from a macromonomer as a branching component.

[0143] Therefore, depending on the selection or mixing ratio of copolymerizing monomer a8 and other monomers, the characteristics of the main chain and side chain of the graft copolymer can be changed.

[0144] In particular, in the present adhesive composition, the copolymerization ratio of the macro monomer in the (meth)acrylic polymer (A) is preferably 30 mass% or less in terms of imparting fluidity during hot melt, more preferably 2 mass% or more or 15 mass% or less, even more preferably 3 mass% or more or 10 mass% or less, and particularly preferably 4 mass% or more or 7 mass% or less.

[0145] Examples of the copolymer monomer a9 mentioned above include benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, nonylphenol EO-modified (meth)acrylate, etc. One or more of these may be combined.

[0146] Examples of the copolymerized monomer a10 above include (meth)acrylic modified silicone, 2-acryloyloxyethyl acid phosphate, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, 1H,1H,5H-octafluoropentyl (meth)acrylate, 1H,1H,2H,2H-tridecafluoro-n-octyl (meth)acrylate, and other fluorine-containing monomers. One or more of these may be combined.

[0147] Among the repeating units derived from (meth)acrylic acid esters in the acrylic polymer (A), it is preferable that the glass transition temperature of at least one repeating unit is -70 to 0°C.

[0148] In addition, the glass transition temperature of a copolymer component refers to a value calculated by Fox's formula from the glass transition temperature and composition ratio of the polymer obtained from the homopolymer of each copolymer component.

[0149] Fox's formula is a calculated value obtained by the following formula, and can be obtained using the values ​​listed in the Polymer Hand Book [Polymer Hand Book, J. Brandrup, Interscience, 1989].

[0150] 1 / (273+Tg)=Σ(Wi / (273+Tgi))

[0151] [In the formula, Wi represents the weight fraction of monomer i, and Tgi represents the Tg (°C) of the homopolymer of monomer i.]

[0152] When obtaining the above (meth)acrylic polymer (A), it is preferable that the glass transition temperature of at least one repeating unit among the repeating units derived from (meth)acrylic acid esters of the acrylic polymer (A) be -70 to 0°C.

[0153] Examples of (meth)acrylic acid esters constituting these repeating units include, butyl acrylate, n-hexyl acrylate, n-octyl acrylate, n-nonyl acrylate, n-decyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, 2-methylhexyl acrylate, isooctyl acrylate, isononyl acrylate, isodecyl acrylate, isodecyl methacrylate, isostearyl acrylate, isostearyl (meth)acrylate, multibranched stearyl acrylate, multibranched stearyl (meth)acrylate, etc., but are not limited to these.

[0154] In addition, when the glass transition temperature of at least one repeating unit among the repeating units derived from (meth)acrylic acid esters of the acrylic polymer (A) is 20 to 120°C, it is desirable because excellent processability or storage stability can be maintained. Specifically, since it affects the hot melt temperature of the adhesive sheet, it is desirable that the glass transition temperature (Tg) be 30°C to 120°C, and among these, it is more desirable that it be 40°C or higher or 110°C or lower, and among these, 50°C or higher or 100°C or lower.

[0155] If there is a repeating unit having such a glass transition temperature (Tg), by adjusting the molecular weight, excellent processability and storage stability can be maintained, and it can be adjusted to hot melt at 50°C or higher.

[0156] Examples of (meth)acrylic acid esters constituting these repeating units include methyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl acrylate, isobutyl acrylate, isobutyl methacrylate, isobornyl acrylate, cyclohexyl acrylate, cyclohexyl methacrylate, 1,4-cyclohexanedimethanol monoacrylate, tetrahydrofurfuryl methacrylate, benzyl acrylate, benzyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, etc.

[0157] In addition, if the glass transition temperature of the repeating unit derived from the (meth)acrylic acid ester of the acrylic polymer (A) is all between -70 and 20°C, it is desirable because it makes the irregularity-following ability superior when there are irregularities on the surface of the substrate.

[0158] Among the above, the (meth)acrylic polymer (A) is preferably a block copolymer and / or a graft copolymer in order to impart hot melt properties to the adhesive.

[0159] The (meth)acrylic polymer (A) can be made into an adhesive sheet with excellent shape stability and hot melt properties by being a block copolymer or a graft copolymer.

[0160] Here, a block copolymer refers to a copolymer having multiple polymer chains containing repeating units derived from (meth)acrylic acid esters, wherein multiple polymer chains having different chemical structures are bonded in a linear fashion.

[0161] It is preferable that some blocks of the block copolymer contain repeating units derived from macromonomers.

[0162] Meanwhile, a graft copolymer is a copolymer containing repeating units derived from (meth)acrylic acid esters as stem components, and means having structures such as comb polymers, brush-shaped polymers, star polymers, palm-shaped polymers, and dumbbell polymers depending on the method of introducing branch components.

[0163] It is preferable that the branch component of the graft copolymer is a copolymer containing repeating units derived from macromonomers.

[0164] In addition, in the examples described below, a graft copolymer containing repeating units derived from macromonomers is used as the base polymer. Since the aggregation and phase separation of repeating units derived from macromonomers to produce an effect is common to both the macromonomer and the graft copolymer, it can be expected that the block copolymer containing macromonomers can also obtain the same effect as the graft copolymer containing macromonomers.

[0165] The above (meth)acrylic polymer (A) is a copolymer containing structural units derived from macromonomers as described above. If the copolymerization ratio of the macromonomer is 2 mass% or more, it is desirable because it can impart hot melt properties. On the other hand, if it is 30 mass% or less, it is desirable because when laminated with the image display device component described later to form a laminate, it does not cause dilamina or the like during folding and has good durability.

[0166] In this regard, the copolymerization ratio of the macromonomer in the (meth)acrylic polymer (A) is preferably 2 mass% or more, and more preferably 3 mass% or more, and more preferably 4 mass% or more. On the other hand, it is preferably 30 mass% or less, and more preferably 15 mass% or less, and more preferably 10 mass% or less, and more preferably 8 mass% or less, and additionally more preferably 7 mass% or less.

[0167] In the present invention, when using a (meth)acrylic polymer (A) in which a (meth)acrylate copolymer having a straight-chain or branched alkyl group having 1 to 3 carbon atoms is copolymerized as the macro monomer, the glass transition temperature of the repeating unit derived from the macro monomer is preferably 20 to 150°C, and among these, 40°C or higher or 130°C or lower, and among these, 60°C or higher or 120°C or lower is more preferable.

[0168] In addition, where the above (meth)acrylic polymer (A) is a block copolymer and / or a graft copolymer, the content of the copolymer component having a glass transition temperature in the above range is preferably 3 mass% or more with respect to the above (meth)acrylic polymer (A) for the same reasons as above, and more preferably 4 mass% or more. On the other hand, it is preferably 10 mass% or less, and more preferably 9 mass% or less, and more preferably 8 mass% or less, and further more preferably 7 mass% or less.

[0169] In addition, as confirmed by the examples described below, if the repeating unit derived from the macromonomer, i.e., the copolymer component having a glass transition temperature of 20 to 150°C, is 3 mass% or more with respect to the (meth)acrylic polymer (A), it can impart hot melt properties, and if it is 4 mass% or more, it can stabilize the shape, so within this range, the same effect as in the examples can be obtained.

[0170] <Crosslinking agent (B)>

[0171] The crosslinking agent (B) is a compound or composition that forms a crosslinking structure in the adhesive composition and is a compound having two or more crosslinkable functional groups.

[0172] By including a crosslinking agent (B) in the adhesive composition, the adhesive composition forms a crosslinked structure, thereby providing durability or resilience to the adhesive sheet.

[0173] Examples of the above-mentioned crosslinkable functional groups include isocyanate groups, epoxy groups, (meth)acryloyl groups, thioisocyanate groups, primary or secondary amino groups, and thiol groups. These may be protected by suitable protecting groups.

[0174] Preferred combinations of crosslinkable functional groups included in the crosslinking agent include epoxy groups only, isocyanate groups only, (meth)acryloyl groups only, thioisocyanate groups only, thiol groups only, primary or secondary amino groups only, combinations of epoxy groups and (meth)acryloyl groups, and combinations of isocyanate groups and (meth)acryloyl groups.

[0175] Among them, in order to ensure that the adhesive sheet hardens when irradiated with active energy rays, it is preferable that the crosslinking agent (B) be a polyfunctional (meth)acrylate (b) having two or more (meth)acryloyl groups.

[0176] The content mass of the polyfunctional (meth)acrylate (b) is preferably 0.5 parts by mass or more per 100 parts by mass of the (meth)acrylic polymer (A), and among these, 1 part by mass or more, and among these, 1.5 parts by mass or more is more preferable.

[0177] Regarding the upper limit value, from the perspective of maintaining appropriate flexibility to ensure followability to the workpiece during bending, it is preferable that it be 10 parts by mass or less, more preferable that it be 7 parts by mass or less, more preferable that it be 5 parts by mass or less, and additionally, among these, 3 parts by mass or less, and among these, 2 parts by mass or less is particularly preferable.

[0178] In particular, when bonding to an image display device component having a step after curing, from the perspective of providing flexibility sufficient to follow the step, it is preferable that the amount be 5 parts by mass or less, and among them, 3 parts by mass or less, and among them, 2 parts by mass or less is more preferable.

[0179] As polyfunctional (meth)acrylates (b), for example, 1,4-butanediol di(meth)acrylate, glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerin glycidyl ether di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, tricyclodecane dimethacrylate, tricyclodecane dimethanol di(meth)acrylate, bisphenol A polyethoxydi(meth)acrylate, bisphenol A polypropoxydi(meth)acrylate, bisphenol F polyethoxydi(meth)acrylate, ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, Trimethylolpropane trioxyethyl (meth)acrylate, ε-caprolactone modified tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, tris(acryloxyethyl)isocyanurate, dipentaerythritol hexa(meth)acrylate, Examples include UV-curable polyfunctional (meth)acrylate monomers such as dipentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, hydroxypivalsan neopentyl glycol di(meth)acrylate, ε-caprolactone adduct of hydroxypivalsan neophenglycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate, as well as polyfunctional (meth)acrylate oligomers such as polyester (meth)acrylate, epoxy (meth)acrylate, urethane (meth)acrylate, and polyether (meth)acrylate.Among these, propoxylated pentaerythritol tri(meth)acrylate and polytetramethylene glycol di(meth)acrylate are preferred. One or more of these may be used in combination.

[0180] The adhesive composition may additionally include a monofunctional (meth)acrylate component (D) having one (meth)acryloyl group. By including the monofunctional (meth)acrylate component, the molecular weight between the crosslinking points of the cured product can be increased, thereby increasing the degree of freedom of movement of the molecular chains. When a laminate in which an image display device component is laminated with the adhesive sheet is folded in a high temperature or low temperature environment, the adhesive sheet made of the adhesive composition can deform accordingly.

[0181] As a monofunctional (meth)acrylate component (D), for example, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, isododecyl (meth)acrylate, tetradecyl (meth)acrylate, stearyl (meth)acrylate, Isostearyl (meth)acrylate, Behenyl (meth)acrylate, Cyclopropyl (meth)acrylate, Cyclobutyl (meth)acrylate, Cyclopentyl (meth)acrylate, Cyclohexyl (meth)acrylate, Cycloheptyl (meth)acrylate, Cyclooctyl (meth)acrylate, Cyclononyl (meth)acrylate, Cyclodecyl (meth)acrylate, Isobornyl (meth)acrylate, Norbornyl (meth)acrylate, Adamantyl (meth)acrylate, Tricyclodecanedimethylol acrylate, Ethoxylated-o-phenylphenol acrylate, Methoxypolyethylene glycol (meth)acrylate, Methoxypolypropylene glycol (meth)acrylate, Polyethylene glycol (meth)acrylate, Polypropylene glycol (meth)acrylate, phenoxyethylene glycol (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, 2-hydroxy-o-phenylphenolpropylacrylate, 2-(meth)acryloyloxyethylsuccinic acid, 2-(meth)acryloyloxyethyltetrahydrophthalic acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylphthalic acid, 2-(meth)acryloyloxypropylhydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, etc., phenoxyethyl (meth)acrylate, phenoxyethylene glycol (meth)acrylate, 2-naphthyl (meth)acrylate, 9-Anthracenyl(meth)acrylate, 1-pyrenylmethyl(meth)acrylate, benzyl(meth)acrylate,Tricyclodecane dimethanol monoacrylate monocarboxylic acid, dicyclofentanyl acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, trimethylolpropane mono(meth)acrylate, glycerin mono(meth)acrylate, pentaerythritol mono(meth)acrylate, diglycerin mono(meth)acrylate, ditrimethylolpropane mono(meth)acrylate, dipentaerythritol mono(meth)acrylate, ethoxylated trimethylolpropane mono(meth)acrylate, propoxylated Examples include trimethylolpropane mono(meth)acrylate, ethoxylated glycerin mono(meth)acrylate, propoxylated glycerin mono(meth)acrylate, ethoxylated pentaerythritol mono(meth)acrylate, propoxylated pentaerythritol mono(meth)acrylate, ethoxylated ditrimethylolpropane mono(meth)acrylate, propoxylated ditrimethylolpropane mono(meth)acrylate, alkylene oxide modified diglycerin mono(meth)acrylate and alkylene oxide modified dipentaerythritol mono(meth)acrylate, etc., as well as monofunctional urethane (meth)acrylate, monofunctional epoxy (meth)acrylate, monofunctional polyester (meth)acrylate, and monofunctional oligomers. These may be used in combination of one or more types.

[0182] When a monofunctional (meth)acrylate component (D) is included, the mass ratio of the polyfunctional (meth)acrylate (b) and the monofunctional (meth)acrylate component (D) is preferably 1:0.1 to 1:9, more preferably 1:1 to 1:9, and even more preferably 1:2 to 1:9. By being within this range, the monofunctional (meth)acrylate component is not excessively abundant, so there is no risk of reduced productivity due to decreased sensitivity to light.

[0183] <Polymerization Initiator (C)>

[0184] The polymerization initiator (C) imparts active energy line curability to the adhesive sheet and may be a compound that generates radicals by the active energy line.

[0185] Polymerization initiators (C) are broadly classified into two types based on the radical generation mechanism: cleavage-type photoinitiators that can generate radicals by cleavage-decomposing the single bonds of the polymerization initiator itself, and hydrogen withdrawal-type photoinitiators that can transfer hydrogen from the hydrogen donor by forming an excited complex between the excited initiator and the hydrogen donor in the system.

[0186] As for the polymerization initiator (C), it may be either a cleavage-type photoinitiator or a hydrogen withdrawal-type photoinitiator, and each may be used individually or a mixture of both, and additionally, one or more of each may be used in combination.

[0187] When a hydrogen drawing type photoinitiator is used as a photoinitiator, it is desirable in that it induces a hydrogen drawing reaction even from acrylic (co)polymers, and accepts not only active energy beam curable compounds but also acrylic (co)polymers into the cross-linking structure, thereby forming a cross-linking structure with many cross-linking sites.

[0188] In addition, when a cleavage-type photoinitiator is used as the polymerization initiator (C), it is desirable in that once a radical is generated, it decomposes and becomes inactive, so there is no risk of unexpected reactions or deterioration after curing.

[0189] As cleavage-type photoinitiators, for example, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-(4-(2-hydroxyethoxy)phenyl)-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-[4-{4-(2-hydroxy-2-methyl-propionyl)benzyl}phenyl]-2-methyl-propan-1-one, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propan-one), methyl phenylglyoxylate, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, Examples include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, or their derivatives.

[0190] As hydrogen drawing type photoinitiators, for example, benzophenone, 4-methyl-benzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 4-(meth)acryloyloxybenzophenone, 2-methyl benzoylbenzoate, methyl benzoylformate, bis(2-phenyl-2-oxoacetate)oxybisethylene, 4-(1,3-acryloyl-1,4,7,10,13-pentaoxotridedecyl)benzophenone, thioxantone, 2-chlorothioxantone, 3-methylthioxantone, 2,4-dimethylthioxantone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, or Examples include derivatives.

[0191] The content of the above polymerization initiator (C) is not particularly limited. As a standard, it is preferable to contain it in a ratio of 0.5 parts by mass or more and 5 parts by mass or less, among them 1 part by mass or more and 4 parts by mass or less, among them 1.2 parts by mass or more and 3 parts by mass or less, per 100 parts by mass of (meth)acrylic polymer (A).

[0192] Other ingredients

[0193] As for the "other components" included in the adhesive composition other than those mentioned above, it is possible to appropriately include various additives such as silane coupling agents, tackifying resins, plasticizers, antioxidants, light stabilizers, metal deactivators, anti-aging agents, hygroscopic agents, polymerization inhibitors, UV absorbers, anti-corrosion agents, inorganic particles, sensitizers, and pigments, as needed. Typically, it is preferable to select the amount of these additives so as not to adversely affect the curing of the adhesive sheet or the physical properties of the adhesive sheet.

[0194] In addition, if necessary, reaction catalysts such as tertiary amine compounds, quaternary ammonium compounds, and tin laurate compounds may be appropriately contained.

[0195] Examples of silane coupling agents include compounds having hydrolyzable functional groups such as alkoxy groups, along with unsaturated groups such as vinyl groups, acryloxy groups, and methacrylic oxygen groups, amino groups, and epoxy groups.

[0196] Specific examples of silane coupling agents include, for instance, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, etc.

[0197] Among them, γ-glycidoxypropyltrimethoxysilane or γ-methacryloxypropyltrimethoxysilane can be preferably used in terms of having good adhesion and minimal discoloration such as yellowing.

[0198] The above silane coupling agent can be used as a single type or in combination of two or more types.

[0199] When containing a silane coupling agent, it is preferable to have 0.1 to 5 parts by mass per 100 parts by mass of (meth)acrylic polymer, and among these, it is more preferable to have 0.2 parts by mass or more or 3 parts by mass or less.

[0200] In addition, similar to silane coupling agents, coupling agents such as organic titanate compounds can also be effectively utilized.

[0201] The adhesive composition may include a hydrocarbon adhesive promoter to impart adhesiveness or hot-melt properties to the adhesive sheet.

[0202] Examples of hydrocarbon tackifiers include terpene resins such as polyterpenes (e.g., α-pinene resins, β-pinene resins, and limonene resins) and aromatic modified polyterpene resins (e.g., phenol modified polyterpene resins), coumarone-indene resins, petroleum resins such as C5 hydrocarbon resins, C9 hydrocarbon resins, C5 / C9 hydrocarbon resins, and dicyclopentadiene resins, and rosins such as modified rosin, hydrogenated rosin, polymerized rosin, and rosin esters.

[0203] It is preferable that the hydrocarbon tackifier be compatible with the adhesive composition.

[0204] The mass of the hydrocarbon tackifier is not particularly limited. It is preferable to have 0.1 to 20 parts by mass per 100 parts by mass of the (meth)acrylic polymer, and more preferable to have 0.5 parts by mass or more or 15 parts by mass or less.

[0205] By including these silane coupling agents or tackifiers, an adhesive composition having excellent adhesive properties can be suitably prepared.

[0206] Method for manufacturing the adhesive sheet

[0207] Next, a method for manufacturing the adhesive sheet is described. However, the following description is merely an example of a method for manufacturing the adhesive sheet, and the adhesive sheet is not limited to being manufactured by such a method.

[0208] In manufacturing the adhesive sheet of the present invention, the adhesive composition of the present invention is prepared by mixing, in addition to the (meth)acrylic polymer (A), a crosslinking agent (B) and / or a polymerization initiator (C) as needed, and other components as needed, in predetermined amounts, molding the adhesive composition into a sheet shape, and, if necessary, curing the adhesive sheet by crosslinking, i.e., polymerizing, a curable compound. However, the method is not limited to this.

[0209] When preparing the adhesive composition, the above raw materials may be mixed using a temperature-controlled mixer (e.g., a single-screw extruder, a twin-screw extruder, a planetary mixer, a twin-screw mixer, a pressure kneader, etc.).

[0210] In addition, when mixing various raw materials, various additives such as silane coupling agents and antioxidants may be supplied to the mixer after being blended with the resin in advance, or supplied after all materials have been melt-mixed in advance, or a masterbatch in which only the additives are concentrated in the resin may be prepared and supplied.

[0211] As a method for forming the adhesive composition into a sheet, known methods such as wet lamination, dry lamination, extrusion casting using a T-die, extrusion lamination, calendering or inflation, injection molding, and liquid curing may be employed. Among these, when manufacturing a sheet, wet lamination, extrusion casting, and extrusion lamination are preferred.

[0212] In addition, if the adhesive composition of the present invention includes a radical initiator, a cured product can be produced by curing it by irradiating it with heat and / or active energy rays. In particular, the adhesive sheet of the present invention can be produced by irradiating a molded body, for example, a sheet body, with heat and / or active energy rays.

[0213] Here, the active energy rays to be irradiated include ionizing radiation such as alpha rays, beta rays, gamma rays, neutron rays, and electron rays, ultraviolet rays, and visible light, and among them, ultraviolet rays are preferred from the perspective of suppressing damage to the optical device components or controlling reactions.

[0214] In addition, there are no specific limitations regarding the irradiation energy, irradiation time, or irradiation method of the active energy beam; it is sufficient as long as the initiator is activated to polymerize the (meth)acrylate component.

[0215] In addition, as another embodiment of the method for manufacturing the adhesive sheet, the adhesive composition may be dissolved in a suitable solvent and carried out using various coating methods.

[0216] When using a coating method, the adhesive sheet may also be obtained by heat curing in addition to the active energy beam irradiation curing described above.

[0217] In the case of coating, the thickness of the adhesive sheet can be adjusted by the coating thickness and the solid content concentration of the coating liquid.

[0218] (Layers other than the main adhesive layer)

[0219] The adhesive sheet may be composed of a single layer consisting of the adhesive layer, or it may be composed of two or more layers having the adhesive layer.

[0220] When the adhesive sheet is composed of two or more layers, the composition of the layers other than the layer formed by the adhesive composition is optional. However, for example, when an intermediate layer, the outermost layer, or the innermost layer is formed as a layer other than the adhesive layer, it is preferable that the adhesive composition forming the layer other than the adhesive layer also be formed from an adhesive composition containing a (meth)acrylic polymer in order to further enhance interlayer adhesion, and among these, it is more preferable to include a (meth)acrylic polymer (A) such as the adhesive layer. Furthermore, it is more preferable that the layer other than the adhesive layer also include a crosslinking agent (B) and / or a polymerization initiator (C).

[0221] In the case where the adhesive sheet is composed of two or more layers, it is preferable that at least the outermost layer, the innermost layer, or both of these layers correspond to the adhesive layer. All layers may also correspond to the adhesive layer.

[0222] In the case where the adhesive sheet is composed of two or more layers, it is preferable that the thickness of the layer corresponding to the adhesive layer accounts for 10% or more and 100% or less of the total thickness of the adhesive sheet, and more preferable that it accounts for 14% or more or 70% or less, and more than 20% or more or 50% or less.

[0223] (Thickness of the adhesive sheet)

[0224] Since bending stress during folding or curving is proportional to the thickness, if the thickness of the adhesive sheet is 50㎛ or less, it can relieve stress during folding or curving and contribute to thinning the laminate and further thinning the flexible image display device. On the other hand, if the thickness is 15㎛ or more, the handling properties are good, so even if there are uneven parts with a height difference of 2㎛ or more and 10㎛ or less on the image display device components, it can follow the step difference.

[0225] Accordingly, the thickness of the adhesive sheet is preferably 50㎛ or less, and among them 45㎛ or less, further among them 40㎛ or less, and particularly 35㎛ or less. Meanwhile, regarding the lower limit, it is preferably 15㎛ or more, among them 17㎛ or more, and among them 20㎛ or more is more preferable.

[0226] As described above, despite being thin, this adhesive sheet can deform to follow the irregularities on the surface of a member for an image display device and penetrate into the irregularities. Therefore, by absorbing the irregularities, it can smooth the surface of the adhesive sheet, that is, the side opposite to the adhesive surface.

[0227] At this time, if the height difference of the uneven surface is 12% or less of the thickness of the adhesive sheet, it can be absorbed.

[0228] As an example of the adhesive sheet, there is an adhesive sheet for a flexible display having an adhesive layer comprising a (meth)acrylic polymer (A), wherein the thickness is 15 μm or more and 50 μm or less, and has active energy beam curability, and when laminated to a member for configuring an image display device having a step difference of 2 μm or more, for example, 2 to 10 μm at a interval of 10 mm or less under the following lamination conditions, the adhesive sheet for a flexible display is characterized by not having foam around the step difference.

[0229] (Joining conditions)

[0230] a) Ultraviolet light is irradiated onto an adhesive sheet with a thickness of 15 to 50 μm so that the total light intensity of 365 nm is 2000 to 4000 mJ / cm².

[0231] b) The adhesive sheet is vacuum-bonded to the surface of a substrate having a height difference of 2 μm or more, for example, a step difference of 2 to 10 μm at intervals of 10 mm or less, under the conditions of a press pressure of 0.2 MPa and 30 seconds.

[0232] c) Autoclave treatment is performed under conditions of 70℃, atmospheric pressure of 0.45 MPa, and 20 minutes.

[0233] <Usage mode of the adhesive sheet>

[0234] The adhesive sheet may also be used as a standalone adhesive sheet. For example, the adhesive sheet may be used by directly applying the adhesive composition to a component for an image display device described later to form a sheet, by directly extruding the adhesive composition, or by injecting it into a mold. Furthermore, the adhesive sheet may be used by directly filling the adhesive composition between components of the image display device.

[0235] In addition, this adhesive sheet can also be used by laminating it with other adhesive sheets.

[0236] For example, if another adhesive sheet has better flexibility than the present adhesive sheet, it is more desirable for a flexible image display device.

[0237] As another such adhesive sheet, there is an adhesive sheet having a gel fraction of 70% or more, a thickness of 0.8 mm to 1.5 mm, and a maximum point of loss tangent obtained by dynamic viscoelasticity measurement in a shear mode of 1 Hz frequency of -25°C or lower.

[0238] In this case, if the maximum point of the loss tangent is -25℃ or lower, it is desirable because it can be restored even during bending at high and low temperatures.

[0239] In this regard, it is preferable that the maximum point of the loss tangent of the other adhesive sheet be -25°C or lower, and among them -30°C or lower, and among them -35°C or lower is more preferable.

[0240] (Adhesive sheet having this release film)

[0241] The adhesive sheet of the present invention may also be used as an adhesive sheet having a release film having an adhesive layer formed from the adhesive composition of the present invention and a release film having the release film (referred to as "adhesive sheet having the release film of the present invention"). For example, the adhesive composition of the present invention may be formed into a single layer or a multilayer sheet shape on the release film and may be in the form of an adhesive sheet having a release film.

[0242] Examples of materials for the above-mentioned release film include polyester film, polyolefin film, polycarbonate film, polystyrene film, acrylic film, triacetylcellulose film, fluoropolymer film, etc. Among these, polyester film and polyolefin film are particularly preferred.

[0243] The thickness of the release film is not particularly limited. Among these, for example, from the perspective of processability and handling, it is preferable to have a thickness of 25㎛ to 500㎛, and among these, it is more preferable to have a thickness of 38㎛ or more or 250㎛ or less, and among these, 50㎛ or more or 200㎛ or less.

[0244] In the adhesive sheet having the release film of the present invention, it is preferable that the release film be a polyester-based film, and also, in terms of releaseability, it is preferable that it be easy to peel off even after irradiation with active energy rays. In this regard, it is preferable that the peeling force of the present adhesive sheet when irradiated with an integrated light amount of 2000 to 4000 mJ / cm² of active energy rays with a wavelength of 365 nm is 0.1 N / cm or less at a peeling angle of 180° and a peeling speed of 300 mm / min.

[0245] <This laminate>

[0246] A laminate (referred to as "the present laminate") related to an example of an embodiment of the present invention is a laminate having a configuration in which a release film and a member for configuring an image display device having a height difference of 2 μm or more on the laminated surface are laminated with the present adhesive sheet interposed therein.

[0247] The release film of the laminate is the same as the release film of the adhesive sheet having the release film.

[0248] For example, a release film and a member for configuring an image display device having a height difference of 2 μm or more on the laminated surface can be laminated with the adhesive sheet interposed therein, and an active energy beam irradiation can be performed on the adhesive sheet by passing the release film from the release film side. The laminate can be manufactured.

[0249] At this time, the irradiation dose of the active energy line is preferably 4000 mJ / ㎠ or less in terms of step absorption, particularly 3500 mJ / ㎠ or less, and additionally 3200 mJ / ㎠ or less. In addition, in terms of sufficiently curing to improve resilience, 2000 mJ / ㎠ or more is preferable, 2500 mJ / ㎠ or more is more preferable, and 2800 mJ / ㎠ or more is more preferable.

[0250] <Laminate for the image display device>

[0251] A laminate for an image display device related to an example of an embodiment of the present invention (hereinafter referred to as "the present laminate") is a laminate having a member for configuring an image display device on at least one side of the adhesive sheet described above.

[0252] The present laminate is preferably a laminate having a configuration in which a member for configuring a first image display device (hereinafter referred to as the "first member"), the present adhesive sheet, and a member for configuring a second image display device (hereinafter referred to as the "second member") are laminated in this order.

[0253] Additionally, the laminate may have a configuration in which the first member, the second member, and the third member for configuring an image display device (hereinafter referred to as the "third member") are each laminated in this order with the adhesive sheet interposed therebetween. The two or more members laminated may be the same or different.

[0254] The thickness of the laminate is not particularly limited. For example, as an example of use in an image display device, the laminate is in the form of a sheet, and if the thickness is 0.02 mm or more, the handling properties are good, and if the thickness is 1.0 mm or less, it can contribute to thinning the laminate.

[0255] Accordingly, the thickness of the laminate is preferably 0.02 mm or more, and among them, 0.03 mm or more, and particularly 0.05 mm or more is more preferable. Meanwhile, regarding the upper limit, it is preferably 1.0 mm or less, and among them, 0.7 mm or less, and particularly 0.5 mm or less is more preferable.

[0256] The laminate can be manufactured by attaching the adhesive sheet to the first member, the second member, and / or the third member. However, the manufacturing method is not limited to this.

[0257] (Image display device component)

[0258] Depending on the configuration of the flexible image display device or the position of the adhesive sheet, the first member, second member, and third member (which may be collectively referred to as “the member”) may include, for example, a cover lens, a polarizer, a phase difference film, a barrier film, a touch sensor film, a light-emitting element, a PSA, etc.

[0259] In particular, considering the configuration of the image display, it is preferable that the first member has a touch input function. If the adhesive sheet has the second and third members described above, the second and third members may have a touch input function.

[0260] In addition, at least one of the present member may have various irregularities formed on the contact surface with the present adhesive sheet by wiring, printing, pattern development, surface treatment, embossing, etc. When the surface of the member has irregularities, the height difference of the step of the irregularities is preferably 2 μm or more, for example, 2 μm or more and 10 μm or less, more preferably 8 μm or less, more preferably 3 μm or more or 7 μm or less, and more preferably 4 μm or more or 6 μm or less.

[0261] At least one of the members for configuring a laminated image display device (including the first member, the second member, and the third member) may be a resin sheet or thin film glass having one or more resins selected from the group consisting of urethane resin, cycloolefin resin, triacetylcellulose resin, (meth)acrylate resin, epoxy resin, and polyimide resin as the main component.

[0262] Here, “main component” means a component that accounts for the largest mass ratio among the components constituting the image display device component, and specifically, it accounts for 50 mass% or more of the image display device component or the adhesive composition forming said component, and 55 mass% or more, and more preferably 60 mass% or more.

[0263] The adhesive sheet can be hot-melted after curing by an active energy beam. Through this hot-melting, even if the surface of the substrate has irregularities, it can be laminated to follow and absorb said irregularities, and the surface can be made smooth. Therefore, when laminating two image display device components with the adhesive sheet interposed therebetween, even if one or both image display device components are non-transmitting light, the two image display device components can be laminated while absorbing said irregularities.

[0264] <This image display device>

[0265] By assembling the present laminate, for example, by laminating the present laminate onto another image display device component, a flexible image display device (also referred to as the “present image display device”) equipped with the present laminate can be formed.

[0266] A flexible image display device refers to an image display device that does not leave fold marks even when subjected to repeated bending, bending, or winding operations, and can quickly recover to the state prior to the bending, bending, or winding operations when released from the bent, bent, or winding state, and can display an image without distortion. In particular, one of the features of this laminate is that it can not only follow the step and absorb the step without generating bubbles even if there are irregularities with a height difference of 2 μm or more on the contact surface of the image display device component with the adhesive sheet, but also prevents the laminate from breaking or cracking even when subjected to bending, bending, or winding operations in low or high temperature environments, and has good recovery properties, thereby enabling the manufacture of an image display device with excellent flexibility.

[0267] In the image display device, the adhesive sheet may be placed on the viewing side of an image display panel, such as a liquid crystal panel, or on the side opposite to the viewing side of the image display panel, that is, on the light source side.

[0268] Method for manufacturing a laminate for an image display device

[0269] Next, an example of a method for manufacturing the present laminate will be described. However, the method for manufacturing the present laminate is not limited to the method described below.

[0270] The present laminate can be manufactured by a method for manufacturing a laminate for an image display device having the following processes 1 to 3, and additionally process 4 as needed.

[0271] Process 1: One surface of the adhesive sheet is laminated to member 1 for configuring an image display device.

[0272] Process 2: Cure the adhesive sheet by irradiating it with an active energy beam.

[0273] Process 3: A member 2 for configuring an image display device is laminated to the other surface of the adhesive sheet to form a laminate.

[0274] Process 4: Heat treatment is performed on the laminate to hot-melt the adhesive sheet.

[0275] Process 2 may be performed after Process 1, or Process 1 may be performed after Process 2. After performing Process 1 and Process 2, Process 3 is performed.

[0276] (Process 1)

[0277] Process 1 is a process of laminating one surface of the adhesive sheet to a member 1 for configuring an image display device.

[0278] As a joining method, known methods such as roll joining, press joining using parallel plates, and diaphragm joining can be used.

[0279] As for the bonding environment, there is an atmospheric bonding method performed at normal pressure and a vacuum bonding method performed under reduced pressure. From the perspective of preventing air bubbles during bonding, a method of bonding on parallel plates under a reduced pressure environment is preferred. In addition, the bonding temperature may be appropriately adjusted.

[0280] (Process 2)

[0281] Process 2 is a process of curing the adhesive sheet by irradiating it with active energy rays.

[0282] Ultraviolet and visible light are preferred as active energy rays.

[0283] Regarding the light source used for irradiating active energy rays, for example, high-pressure mercury lamps, metal halide lamps, xenon lamps, halogen lamps, LED lamps, fluorescent lamps, etc., it can be selected and used according to the wavelength or amount of light being irradiated.

[0284] There are no specific limitations regarding the irradiation time or the means of irradiation, but for example, if ultraviolet irradiation is used, it is desirable to irradiate such that the accumulated amount of light at a wavelength of 365 nm is 2000 mJ / cm² or more, particularly 3000 mJ / cm² or more.

[0285] In the case where the surface of the first member or the second member, for example, the laminated surface, has an irregularity with a height difference of 2 μm or more, for example, 2 μm or more and 10 μm or less, by hot-melting the adhesive sheet, the adhesive sheet can follow the height difference and absorb the height difference, so that the surface of the laminate can preferably be smoothed.

[0286] (Process 3)

[0287] Process 3 is a process of forming a laminate by laminating a member 2 for configuring an image display device onto the other surface of the adhesive sheet that has undergone processes 1 and 2.

[0288] In process 3, if necessary, the image display device component 1 and / or image display device component 2 may be laminated together with heating the image display device component 1 and / or image display device component 2.

[0289] Heating at this time may be, for example, a method of pressing a laminate for an image display device, which is composed of an image display device component 1 / this adhesive sheet / an image display device component 2, from both sides with a press plate heated to a predetermined temperature.

[0290] In addition, the heating temperature at this time is preferably 50°C or higher and 80°C or lower. That is, it is preferable to heat the image display device component 1 and / or image display device component 2 to 50°C or higher and hot-melt the adhesive sheet while laminating the image display device component 2.

[0291] In addition, when applying pressure with a press plate, it is more preferable that the press pressure be 0.01 MPa or more or 0.4 MPa or less, and among them, 0.02 MPa or more or 0.35 MPa or less.

[0292] (Process 4)

[0293] Process 4 is a process of hot-melting the adhesive sheet by performing a heat treatment on the laminate obtained in Process 3 after lamination. This Process 4 may be performed as needed.

[0294] By performing a heat treatment on the laminate after lamination to hot-melt the adhesive sheet, even if the surface of the first member or the second member, for example, the laminated surface, has an irregularity with a height difference of 2 μm or more, for example, 2 μm or more and 10 μm or less, the adhesive sheet can follow the height difference and absorb the height difference to make the surface smooth.

[0295] When heat-treating the laminate, the heating temperature is preferably 40°C or higher and 90°C or lower. Among these, the temperature is 50°C or higher and 80°C or lower, and among these, it is more preferable to be 60°C or higher and 70°C or lower.

[0296] In addition, along with the heat treatment, an atmospheric pressure of 0.2 MPa or more and 0.8 MPa or less may be applied to the laminate for at least 5 minutes. At this time, the atmospheric pressure is preferably 0.2 MPa or more and 0.8 MPa or less, and among them, 0.4 MPa or more or 0.6 MPa or less is more preferable.

[0297] The above processing time is preferably 5 minutes or more or 60 minutes or less, and among them, 10 minutes or more or 30 minutes or less.

[0298] In process 4, in addition to the heat treatment above, a press pressure of 0.01 MPa or more and 0.4 MPa or less may be applied to the laminate.

[0299] The above press pressure is preferably 0.01 MPa or more or 0.4 MPa or less, and among them, 0.02 MPa or more or 0.35 MPa or less.

[0300] The above processing time is preferably 5 seconds or more or 10 minutes or less, and among them, 10 seconds or more or 5 minutes or less.

[0301] In addition, when performing process 4, it is preferable to perform it in the order of processes 1, 2, 3, and 4.

[0302] The present manufacturing method is effective when the first and second members do not transmit active energy rays.

[0303] When hot-melting the adhesive sheet after curing, it is preferable to perform the hot-melt treatment within 30 minutes after irradiating the adhesive sheet with an active energy beam. This is because performing the hot-melt treatment before complete curing makes it easier to follow irregularities with a step difference of 2 μm or more. In this regard, the time from irradiating with an active energy beam to the hot-melt treatment is preferably within 30 minutes, more preferably within 20 minutes, and even more preferably within 10 minutes.

[0304] <Explanation of phrases, etc.>

[0305] In the present invention, even when referred to as "film," it includes "sheet," and even when referred to as "sheet," it includes "film."

[0306] In addition, when the term "panel" is used, such as in image display panels or protective panels, it includes a plate body, a sheet, and a film.

[0307] In this specification, when "X~Y" (where X and Y are arbitrary numbers) is used, unless otherwise specifically stated, it includes the meaning of "X or greater and Y or less," as well as the meaning of "preferably greater than X" or "preferably smaller than Y."

[0308] In addition, when written as “X or greater” (where X is any number), it implies “preferably greater than X” unless otherwise specified, and when written as “Y or less” (where Y is any number), it implies “preferably less than Y” unless otherwise specified.

[0309] [Example]

[0310] The present invention is further explained by the following examples. However, the present invention is not limited to the examples shown below.

[0311] First, details of the raw materials of the adhesive composition prepared in the example will be explained.

[0312] <(Meta)acrylic polymer(A)>

[0313] · (Meta)acrylic polymer (A-1): An acrylic graft copolymer formed by copolymerizing 6 parts by mass of polymethyl methacrylate macromonomer (Tg 105°C) with a number average molecular weight of 2800, 90 parts by mass of butyl acrylate (Tg -55°C), and 4 parts by mass of acrylic acid (Tg 106°C) (mass average molecular weight: 220,000, Tg -45°C)

[0314] · (Meta)acrylic polymer (A-2): An acrylic graft copolymer formed by copolymerizing 15 parts by mass of polymethyl methacrylate macromonomer (Tg 105°C) with a number average molecular weight of 2800, 81 parts by mass of butyl acrylate (Tg -55°C), and 4 parts by mass of acrylic acid (Tg 106°C) (mass average molecular weight: 160,000, Tg -36°C)

[0315] · (Meta)acrylic polymer (A-3): An acrylic copolymer formed by copolymerizing 2-ethylhexyl acrylate (Tg -70°C), methyl acrylate (Tg 8°C), ethyl acrylate (Tg -20°C), 2-hydroxyethyl acrylate (Tg -15°C), and 4-hydroxybutyl acrylate (Tg -40°C) (mass average molecular weight: approx. 700,000, Tg -54°C)

[0316] · (Meta)acrylic polymer (A-4): An acrylic graft copolymer formed by random copolymerization of 15 parts by mass of SLMA (Lauryl methacrylate) macromonomer (Tg -65°C) with a number average molecular weight of 5500 and 85 parts by mass of butyl acrylate (Tg -55°C) (mass average molecular weight: 410,000, Tg -38°C)

[0317] · (Meta)acrylic polymer (A-5): An acrylic graft copolymer formed by copolymerizing 9 parts by mass of polymethyl methacrylate macromonomer (Tg 105°C) with a number average molecular weight of 2800, 87 parts by mass of butyl acrylate (Tg -55°C), and 4 parts by mass of acrylic acid (Tg 106°C) (mass average molecular weight: 160,000, Tg -36°C)

[0318] · (Meta)acrylic polymer (A-6): Acrylic copolymer formed by copolymerizing 2-ethylhexyl acrylate (Tg -70°C), methyl acrylate (Tg 8°C), and 2-hydroxyethyl acrylate (Tg -15°C) (Mass average molecular weight: approx. 400,000, Tg -50°C)

[0319] The glass transition temperature of each copolymer component in the above (meth)acrylic polymer is the literature value of the glass transition temperature obtained from the homopolymer of the corresponding component. For the macromonomer, the literature value of the glass transition temperature obtained from the homopolymer of the component forming the high molecular weight backbone in the macromonomer was used.

[0320] The glass transition temperature of the acrylic copolymer is described as the theoretical Tg calculated by Fox's formula from the glass transition temperatures and composition ratios of each copolymer component.

[0321] <Crosslinking agent (B)>

[0322] · Crosslinking agent (B-1): Propoxylated pentaerythritol triacrylate

[0323] · Crosslinking agent (B-2): Polytetramethylene glycol di(meth)acrylate

[0324] <Polymerization Initiator (C)>

[0325] · Initiator (C-1): Mixture of 2,4,6-trimethylbenzophenone and 4-methylbenzophenone (IGM "Esacure TZT")

[0326] <Monofunctional (meth)acrylate(D)>

[0327] · Monofunctional (meth)acrylate (D-1): 4-hydroxybutylacrylate

[0328] · Monofunctional (meth)acrylate (D-2): Monofunctional urethane acrylate containing a propylene glycol backbone (AGC “PEM-X264”, mass average molecular weight: 10,000)

[0329] Others

[0330] · Silane coupling agent (E-1): KBM 403 (Shin-Etsu Silicone)

[0331] · Rust Inhibitor (E-2): 1,2,3-Benzotriazole

[0332] [Example 1]

[0333] An adhesive composition was prepared by uniformly mixing 100 parts by mass of a (meth)acrylic polymer (A-1), 1.5 parts by mass of a crosslinking agent (B-1), 1.5 parts by mass of an initiator (C-1), and 0.5 parts by mass of a rust inhibitor (E-2).

[0334] On a silicone-released release film with a thickness of 100 μm (a PET film manufactured by Mitsubishi Chemical), the adhesive composition was spread into a sheet with a thickness of 25 μm.

[0335] Next, a release film with a thickness of 75 μm (a PET film manufactured by Mitsubishi Chemical Co., Ltd.) that has been silicone-release treated is laminated onto the adhesive composition on the sheet to form a laminate, thereby obtaining an adhesive sheet 1 having a release film composed of a release film / adhesive sheet 1 / release film.

[0336] In addition, adhesive sheet 1 was an active energy beam curable adhesive sheet having active energy beam curability that is cured by irradiating an active energy beam.

[0337] [Example 2]

[0338] As shown in Table 1, except for changing the thickness, an adhesive sheet 2 was manufactured having an adhesive sheet 2 and a release film composed of a release film / adhesive sheet 2 / release film, similar to Example 1.

[0339] In addition, adhesive sheet 2 was an adhesive sheet having active energy beam curability that hardens by irradiating light.

[0340] [Example 3]

[0341] As shown in Table 1, each component was prepared and used as a raw material for the adhesive layer.

[0342] Next, the adhesive composition was sandwiched between two release films: a silicone-released 100㎛ release film (a PET film manufactured by Mitsubishi Chemical, with a thickness of 100㎛) and a silicone-released 75㎛ release film (a PET film manufactured by Mitsubishi Chemical), i.e., two release films, and hot-melt molded into a sheet with a thickness of 50㎛ to obtain an adhesive sheet 3 having a release film composed of a release film / adhesive sheet 3 / release film.

[0343] In addition, adhesive sheet 3 was an adhesive sheet having active energy beam curability that hardens by irradiating light.

[0344] [Example 4]

[0345] As shown in Table 1, each component was prepared and used as a raw material for the adhesive layer.

[0346] Similar to Example 3, an adhesive sheet 4 was manufactured having an adhesive sheet 4 and a release film composed of a release film / adhesive sheet 4 / release film.

[0347] In addition, adhesive sheet 4 was an adhesive sheet having active energy beam curability that hardens by irradiating light.

[0348] [Example 5]

[0349] As shown in Table 1, each component was prepared and used as a raw material for the adhesive layer.

[0350] As in Example 1, an adhesive sheet 5 was manufactured having an adhesive sheet 5 and a release film composed of a release film / adhesive sheet 5 / release film.

[0351] In addition, adhesive sheet 5 was an adhesive sheet having active energy beam curability that hardens by irradiating light.

[0352] [Example 6]

[0353] As shown in Table 1, each component was prepared and used as a raw material for the adhesive layer.

[0354] Similar to Example 3, an adhesive sheet 6 was manufactured having an adhesive sheet 6 and a release film composed of a release film / adhesive sheet 6 / release film.

[0355] In addition, adhesive sheet 6 was an adhesive sheet having active energy beam curability that hardens by irradiating light.

[0356] [Example 7]

[0357] As shown in Table 1, each component was prepared and used as a raw material for the adhesive layer.

[0358] Similar to Example 3, an adhesive sheet 7 was manufactured having an adhesive sheet 7 and a release film composed of a release film / adhesive sheet 7 / release film.

[0359] In addition, adhesive sheet 7 was an adhesive sheet having active energy beam curability that hardens by irradiating light.

[0360] [Comparative Example 1]

[0361] An adhesive composition was prepared by combining 100 parts by mass of a (meth)acrylic polymer (A-3), 25 parts by mass of a monofunctional (meth)acrylate (D-1), 3 parts by mass of an initiator (C-1), 0.3 parts by mass of a silane coupling agent, and 0.3 parts by mass of a rust inhibitor, and the adhesive composition was spread into a sheet on a silicone-treated release film (a PET film manufactured by Mitsubishi Chemical Co., Ltd.) with a thickness of 100 μm so that the thickness of the adhesive composition was 25 μm.

[0362] Next, a release film (a PET film manufactured by Mitsubishi Chemical Co., Ltd.) with a thickness of 75 μm and silicone release treatment was laminated onto the adhesive composition on the sheet to form a laminate, and a metal halide lamp irradiation device (Ushio Electric Co., Ltd., UVC-0516S1, lamp UVL-8001M3-N) was used to pass through the release film and light irradiation was performed on the adhesive composition such that the irradiation amount of a wavelength of 365 nm was accumulated to 3000 mJ / cm², thereby obtaining an adhesive sheet laminate in which release films were laminated on both the front and back sides of a 25 μm adhesive sheet (adhesive sheet 8).

[0363] Adhesive sheet 8 is an adhesive sheet in which the reaction caused by light irradiation has proceeded sufficiently, leaving almost no room for active energy beam curing.

[0364] [Comparative Example 2]

[0365] 100 parts by mass of (meth)acrylic polymer (A-2), 2.5 parts by mass of crosslinking agent (B-1), 7.5 parts by mass of monofunctional (meth)acrylate (D-1), 1.5 parts by mass of initiator (C-1), and 0.3 parts by mass of rust inhibitor were prepared and used as raw materials for the adhesive layer.

[0366] Next, the adhesive composition was sandwiched between two release films: a silicone-released 100 μm release film (a PET film manufactured by Mitsubishi Chemical, with a thickness of 100 μm) and a silicone-released 75 μm release film (a PET film manufactured by Mitsubishi Chemical), i.e., two release films, and hot-melt molded into a sheet with a thickness of 25 μm to obtain an adhesive sheet 9 having a release film composed of a release film / adhesive sheet 9 / release film.

[0367] In addition, adhesive sheet 9 was an adhesive sheet having active energy beam curability that hardens by irradiating light.

[0368] [Reference Example 1]

[0369] Adhesive sheet 1 prepared in Example 1 and adhesive sheet 8 prepared in Comparative Example 1 as another adhesive sheet were laminated using a hand roller to produce a laminated sheet with a total thickness of 50 μm.

[0370] In addition, the gel fraction of adhesive sheet 8 as another adhesive sheet was 70%, and the maximum point of the loss tangent obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz was -37°C.

[0371] [Evaluation of Adhesive Sheets]

[0372] The measurement and evaluation of the adhesive sheet obtained in the example were performed as follows.

[0373] Creep Test

[0374] In the example and comparative example, the release film was removed from the adhesive sheet having the release film prepared, and the lamination was repeated with a hand roller to achieve a thickness of about 0.9 mm. An adhesive sheet having a release film that was punched into a circular shape with a diameter of 8 mm was prepared and used as a sample.

[0375] For the above sample, the release film was removed when installing it with a rheometer (TA Instruments “DHR-2”), and the twist (creep deformation) (%) after 3600 seconds was measured using a measuring jig: 8 mm diameter parallel plate, temperature: 25℃, pressure: 1000 Pa.

[0376] The adhesive sheets prepared in the examples and comparative examples were cured by irradiating the adhesive sheets with ultraviolet light through a release film using a high-pressure mercury lamp so that the integrated light amount of 365 nm was 3000 mJ / cm² for adhesive sheets 1-4 and 6-7, and 4000 mJ / cm² for adhesive sheets 5 and 9.

[0377] In addition, the adhesive sheet 8 prepared in Comparative Example 1 was provided for measurement without performing the above-mentioned ultraviolet irradiation because the reaction by light irradiation had proceeded sufficiently and there was almost no room for active energy beam curing.

[0378] A cured adhesive sheet was laminated to a thickness of about 0.9 mm and then punched into a circular shape with a diameter of 8 mm to produce a sample.

[0379] For the above sample, the warping (creep deformation) (%) after 180 seconds was measured using a rheometer (TA Instruments “DHR-2”) with a measuring jig: 8 mm diameter parallel plate, temperature: 80°C, and pressure: 1000 Pa.

[0380] Restoration Rate

[0381] For adhesive sheets equipped with release films prepared in the examples and comparative examples, ultraviolet light was irradiated onto the adhesive sheets through the release film using a high-pressure mercury lamp so that the total light amount of 365 nm was 3000 mJ / cm² for adhesive sheets 1-4 and 6-7, and 4000 mJ / cm² for adhesive sheets 5 and 9, and the adhesive sheets were cured.

[0382] In addition, the adhesive sheet 8 prepared in Comparative Example 1 was provided for measurement without performing the above-mentioned ultraviolet irradiation because the reaction by light irradiation had proceeded sufficiently and there was almost no room for active energy beam curing.

[0383] A cured adhesive sheet was laminated to a thickness of approximately 0.9 mm and then punched into a circular shape with a diameter of 8 mm to produce a sample.

[0384] For the above sample, a rheometer (TA Instruments “DHR-2”, measurement jig: 8 mm diameter parallel plate) was used, and stress was applied to the sample in the shear direction for 600 seconds at a temperature of 25°C so that the shear twist as the initial twist (x) was 200%. Afterward, the stress was released, and the residual twist (y) after 600 seconds was measured, and the recovery rate was calculated from the following formula.

[0385] Restoration rate (%) = {(xy) / x} × 100

[0386] In the above formula, x is the initial twist applied in the shear direction to an adhesive sheet laminated to a thickness of about 0.9 mm, and y is the residual twist after 600 seconds have passed since the initial twist was released after being applied for 600 seconds.

[0387] Loss tangent (tanδ)

[0388] The adhesive sheets prepared in the examples and comparative examples were laminated to a thickness of about 0.9 mm and then punched into a circular shape with a diameter of 8 mm.

[0389] For the above sample, dynamic viscoelasticity measurements were performed using a viscoelasticity measuring device (manufactured by TA Instruments, product name “DHR-2”) with a measuring jig: 8 mm diameter parallel plate, frequency: 1 Hz, measuring temperature: -50 to 150°C, and heating rate: 5°C / min, and the value of the loss tangent (tanδ) at -30°C was read from the obtained data.

[0390] Gel fraction

[0391] The release film was removed from the adhesive sheet having each release film prepared in the examples and comparative examples, and about 0.1 g of adhesive sheet fragment was taken.

[0392] The collected adhesive sheet piece was wrapped in a SUS mesh (#150) of mass (X) that had been shaped into a pouch beforehand, and the opening of the pouch was closed to prepare a sample, and the mass (Y) of the sample was measured. The sample was immersed in ethyl acetate and stored in a dark place at 23°C for 24 hours. Afterward, the sample was removed and heated at 70°C for 4.5 hours to evaporate the ethyl acetate, and the mass (Z) of the dried sample was measured. The gel fraction before curing was calculated using the following formula for each measured mass.

[0393] Gel fraction (%) = [(ZX) / (YX)] × 100

[0394] For adhesive sheets equipped with release films prepared in the examples and comparative examples, ultraviolet rays were irradiated onto the adhesive sheets through the release film using a high-pressure mercury lamp so that the integrated light intensity of 365 nm was 3000 mJ / cm² for adhesive sheets 1-4 and 6-7, and 4000 mJ / cm² for adhesive sheets 5 and 9, thereby curing the adhesive sheets. For the adhesive sheets after curing, the gel fraction after active energy beam curing was determined in the same order as the gel fraction evaluation above.

[0395] In addition, the adhesive sheet 8 prepared in Comparative Example 1 was provided for measurement as the gel fraction after curing because the reaction by light irradiation proceeded sufficiently and there was almost no room for active energy beam curing.

[0396] <Adhesion>

[0397] From the adhesive sheet having each release film prepared in the examples and comparative examples, one release film was removed, and a polyethylene terephthalate film (Toyo Spinning Co., Ltd. "Cosmo Shine A4300", thickness 100 μm) was roll-pressed with a hand roller as a backing film. This was cut into a short sheet with a width of 10 mm × a length of 150 mm, and the remaining release film was peeled off to expose the adhesive surface, which was then roll-attached to soda-lime glass using a hand roller. The laminate was then subjected to autoclave treatment (60°C, gauge pressure 0.2 MPa, 20 minutes) to finish bonding, thereby producing an adhesive strength measurement sample.

[0398] The backing film was peeled off from the soda-lime glass at 23℃ and 50% RH while pulling at a peeling speed of 300 mm / min at an angle of 180°, and the tensile strength was measured using a load cell to determine the adhesion strength (N / cm) to the soda-lime glass.

[0399] <Adhesion (Curing after bonding)>

[0400] From the adhesive sheet having each release film prepared in the examples and comparative examples, one release film was removed, and a polyethylene terephthalate film (Toyo Spinning Co., Ltd. "Cosmo Shine A4300", thickness 100 μm) was roll-pressed with a hand roller as a backing film. This was cut into a sheet with a width of 10 mm × a length of 150 mm, and the remaining release film was peeled off to expose the adhesive surface, which was then roll-bonded to soda-lime glass using a hand roller. The laminate was then subjected to autoclave treatment (60°C, gauge pressure 0.2 MPa, 20 minutes) to finish bonding. After that, using a high-pressure mercury lamp, ultraviolet light was irradiated onto the adhesive sheets with a backing film interposed so that the integrated light intensity of 365 nm was 3000 mJ / cm² for adhesive sheets 1-4 and 6-7, and 4000 mJ / cm² for adhesive sheets 5 and 9, thereby curing the adhesive sheets and preparing adhesive strength measurement samples.

[0401] The backing film was peeled from the soda-lime glass at 23° and 50% RH while pulling at a peeling speed of 300 mm / min at an angle of 180°, and the tensile strength was measured using a load cell. The 180° peel strength (N / cm) of the adhesive sheet against the soda-lime glass after active energy beam curing was measured and used as the adhesive strength (cured after lamination).

[0402] In addition, the adhesive sheet 8 prepared in Comparative Example 1 was not subjected to this measurement because the reaction caused by light irradiation had progressed sufficiently, leaving almost no room for active energy beam curing.

[0403] <Adhesion (Curing before bonding)>

[0404] From the adhesive sheets equipped with each release film prepared in the examples and comparative examples, one release film was removed, and a polyethylene terephthalate film (Toyo Spinning Co., Ltd. “Cosmo Shine A4300”, thickness 100 μm) was roll-pressed with a hand roller as a backing film. Using a high-pressure mercury lamp, ultraviolet light was irradiated onto the adhesive sheets through the backing film so that the integrated light amount of 365 nm was 3000 mJ / ㎠ for adhesive sheets 1-4 and 6-7, and 4000 mJ / ㎠ for adhesive sheets 5 and 9, and the adhesive sheets were cured.

[0405] In addition, the adhesive sheet 8 prepared in Comparative Example 1 was provided for measurement as a sheet cured before lamination because the reaction by light irradiation had proceeded sufficiently and there was almost no room for active energy beam curing.

[0406] As described above, the adhesive sheet cured was cut into a single sheet with a width of 10 mm × a length of 150 mm, the remaining release film was peeled off to expose the adhesive surface, which was then roll-bonded to soda-lime glass using a hand roller, and the laminate was subjected to autoclave treatment (60°C, gauge pressure 0.2 MPa, 20 minutes) to finish bonding, thereby producing an adhesive strength measurement sample.

[0407] The backing film was peeled from the soda-lime glass at 23° and 50% RH while pulling at a peeling speed of 300 mm / min at an angle of 180°, and the tensile strength was measured using a load cell. The 180° peel strength (N / cm) of the adhesive sheet against the soda-lime glass after active energy beam curing was measured and used as the adhesive strength (cured before lamination).

[0408] Step absorption

[0409] An evaluation substrate was prepared by placing two PET films of 6 mm × 100 mm × 5.4 μm thickness at 10 mm intervals on a soda-lime glass of 54 mm × 82 mm × 0.55 mm thickness, and forming a convex shape portion having a height difference of 5.4 μm on the surface.

[0410] An adhesive sheet having each release film prepared in the examples and comparative examples was cut to a size of 5 cm × 5 cm, and one release film was peeled off to expose the adhesive surface, which was then positioned opposite the surface of the evaluation substrate having a step difference, and vacuum laminated under conditions of a press pressure of 0.2 MPa for 30 seconds, and then autoclave treated under conditions of 70°C, atmospheric pressure of 0.45 MPa for 20 minutes to produce a laminate for evaluating step difference absorption.

[0411] The manufactured laminate was visually inspected and evaluated according to the following evaluation criteria.

[0412] ◎ : The adhesive sheet followed the steps near all steps, and there were no bubbles.

[0413] ○ : There were 2 or fewer bubbles occurring near the step.

[0414] × : Bubbles formed because the adhesive sheet did not follow at three or more locations near the step.

[0415] <Standard absorption (after curing)>

[0416] For an adhesive sheet having a release film prepared in Examples 1 to 4, ultraviolet light was irradiated onto the adhesive sheet through the release film using a high-pressure mercury lamp so that the integrated light amount of 365 nm was 3000 mJ / cm², and the adhesive sheet was cured.

[0417] As described above, the release film on one side of the cured adhesive sheet was peeled off to expose the adhesive surface, and the surface of the evaluation substrate having a step was placed facing the other side. The two surfaces were vacuum laminated under conditions of a press pressure of 0.2 MPa for 30 seconds, and then autoclave treatment was performed under conditions of 70°C, atmospheric pressure of 0.45 MPa, and 20 minutes. The above procedure was carried out within 10 minutes after UV irradiation treatment to produce a laminate for evaluating step absorption after curing. The produced laminate was visually inspected and evaluated using the same evaluation criteria as the step absorption evaluation.

[0418] [Evaluation of Laminated Structures]

[0419] For adhesive sheets equipped with release films prepared in the examples and comparative examples, ultraviolet light was irradiated onto the adhesive sheets through the release film using a high-pressure mercury lamp so that the total light amount of 365 nm was 3000 mJ / cm² for adhesive sheets 1-4, 6-7 and the laminated sheet of Reference Example 1, and 4000 mJ / cm² for adhesive sheets 5 and 9, and the adhesive sheets were cured.

[0420] In addition, the adhesive sheet 8 prepared in Comparative Example 1 was used as a laminate sample for evaluating flexibility, as the reaction caused by light irradiation had progressed sufficiently and there was almost no room for active energy beam curing. Therefore, the above-mentioned ultraviolet irradiation was not performed.

[0421] The release film of each adhesive sheet was removed, and a transparent polyimide film (manufactured by Kolon, thickness 50 μm) was roll-laminated to both sides of the adhesive sheet using a hand roll. Afterward, the samples were autoclaved under conditions of 60°C, 0.2 MPa pressure, and 20 minutes to produce laminated samples for evaluating flexibility.

[0422] Dynamic Flexibility

[0423] The above laminated sample was subjected to a cycle evaluation of U-shaped bending using a durability system in a constant temperature and humidity chamber and a planar body no-load U-shaped extension tester (manufactured by Yuasa System Equipment Co., Ltd.) with a radius of curvature R=3 mm and a speed of 60 rpm (1 Hz).

[0424] In addition, for the laminated sheet of Reference Example 1, an evaluation was performed with the adhesive sheet 8 side as the inner side as another adhesive sheet.

[0425] After 200,000 bending cycles in a test environment of -20℃ or 60℃, 90% RH, it was evaluated according to the following evaluation criteria.

[0426] ○ : None of the dillamy, fracture, buckling, or flow occurred in the bend.

[0427] × : Dilamy, fracture, buckling, or flow occurred in the bend.

[0428] Static Flexibility

[0429] The above laminated sample was bent to a radius of curvature R=3 mm, stored for 24 hours under conditions of 60°C and 90% RH, and evaluated according to the following evaluation criteria.

[0430] In addition, for the laminated sheet of Reference Example 1, a test was performed with adhesive sheet 8, which is another adhesive sheet, bent to an inner side with a radius of curvature R=3 mm.

[0431] ○ : None of the dillamy, fracture, buckling, or flow occurred in the bend.

[0432] × : Dilamy, fracture, buckling, or flow was observed at the bend.

[0433] The results obtained by measuring and evaluating adhesive sheets and laminates are shown in Table 1.

[0434]

[0435] The adhesive sheets of Examples 1-7 exhibited good lamination in the step absorption test, excellent resilience, and excellent durability in the flexibility test when formed into a laminate. Additionally, the adhesive sheet of Example 1-4 exhibited good lamination in the step absorption test even when laminated after curing.

[0436] The adhesive sheet of Reference Example 1 also exhibited excellent step absorption and excellent bending durability.

[0437] Meanwhile, the adhesive sheet manufactured in Comparative Example 1 used a material that does not have high fluidity, so the warping after 3600 seconds at 25°C was 50% or less, and the step absorption was inferior.

[0438] The adhesive sheet prepared in Comparative Example 2 used a material with low flexibility after curing, so its recovery ability after 200% deformation at 25°C after active energy curing was inferior, and its bending durability when formed into a laminate was also inferior.

Claims

Claim 1 A pressure-sensitive layer formed from a pressure-sensitive adhesive composition comprising a (meth)acrylic polymer (A), a crosslinking agent (B), and a polymerization initiator (C), wherein the (meth)acrylic polymer (A) is formed from a copolymer monomer component in which the glass transition temperature of repeating units derived from (meth)acrylic acid esters of the (meth)acrylic polymer (A) is all -70 to 20°C, the crosslinking agent (B) comprises a polyfunctional (meth)acrylate having two or more (meth)acryloyl groups, and the content of the polyfunctional (meth)acrylate is 0.5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the (meth)acrylic polymer (A), and the content of the polymerization initiator (C) is 0.5 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the (meth)acrylic polymer (A). An active energy beam curable adhesive sheet for a flexible display, which satisfies the requirements of (1) to (3) below and has a thickness of 15㎛ or more and 50㎛ or less. (1) The thickness is 0.8㎜ to 1.5㎜, and the warping (creep deformation) is 50% or more when a pressure of 1000Pa is applied for 3600 seconds at a temperature of 25℃. (2) The thickness is 0.8㎜ to 1.5㎜, and the warping (creep deformation) is 10% or more when a pressure of 1000Pa is applied for 180 seconds at a temperature of 80℃ after irradiating an active energy beam of wavelength 365 nm with an integrated light amount of 2000 to 4000 mJ / ㎠. (3) When an active energy beam of wavelength 365 nm is irradiated with an integrated light amount of 2000 to 4000 mJ / ㎠, the warping is represented by the following formula The recovery rate after 200% deformation at 25℃ is 60% or higher. Recovery rate (%) = {(xy) / x} × 100 (where x is the initial twist applied in the shear direction to an adhesive sheet with a thickness of 0.8 mm to 1.5 mm, and y is the residual twist after 600 seconds have elapsed following the release of the initial twist applied for 600 seconds.) Claim 2 In claim 1, the (meth)acrylic polymer (A) is a block copolymer and / or graft copolymer, an active energy beam curable adhesive sheet for a flexible display. Claim 3 An active energy beam curable adhesive sheet for a flexible display according to claim 1, wherein the adhesive sheet has a thickness of 0.8 mm to 1.5 mm and the maximum point of the loss tangent obtained when dynamic viscoelasticity is measured in a shear mode at a frequency of 1 Hz is -20°C or lower. Claim 4 In claim 1, the (meth)acrylic polymer (A) is a copolymer comprising structural units derived from macromonomers, an active energy beam curable adhesive sheet for a flexible display. Claim 5 In claim 4, the macro monomer is a copolymerized macro monomer of a (meth)acrylate having a straight-chain or branched alkyl group having 1 to 3 carbon atoms, for an active energy beam curable adhesive sheet for a flexible display. Claim 6 In claim 4, the macro monomer is a copolymerized macro monomer of a (meth)acrylate having a straight-chain or branched alkyl group having 8 to 18 carbon atoms, an active energy beam curable adhesive sheet for a flexible display. Claim 7 In claim 4, the (meth)acrylic polymer (A) is an active energy beam curable adhesive sheet for a flexible display having a copolymerization ratio of macromonomers of 2 mass% or more and 30 mass% or less. Claim 8 An active energy beam curable adhesive sheet for a flexible display according to claim 1, wherein the gel fraction is 0% or more and 20% or less. Claim 9 An active energy line curable adhesive sheet for a flexible display according to claim 1, wherein when an active energy line with a wavelength of 365 nm is irradiated with an integrated light amount of 2000 to 4000 mJ / cm², the gel fraction increases compared to before irradiation, and the gel fraction becomes 10% or more and 85% or less. Claim 10 An active energy beam curable adhesive sheet for a flexible display according to claim 1, having a thickness of 0.8 mm to 1.5 mm, and a loss tangent obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz, which is 0.8 or greater at -30°C. Claim 11 An active energy beam curable adhesive sheet for a flexible display, characterized in that, in claim 1, it additionally possesses the following characteristics (4) and (5). (4) An adhesive strength of 1 N / cm or more on a soda-lime glass surface at 23°C, 50% RH, a peel angle of 180°, and a peel speed of 300 mm / min. (5) An adhesive strength of 1 N / cm or more on the surface of the soda-lime glass at 23°C, 50% RH, a peel angle of 180°, and a peel speed of 300 mm / min when the adhesive sheet is laminated to the soda-lime glass and then irradiated with an integrated light intensity of 2000 to 4000 mJ / cm² of an active energy beam with a wavelength of 365 nm. Claim 12 In claim 11, additionally, an active energy beam curable adhesive sheet for a flexible display characterized by having the characteristics of (6). (6) When the adhesive sheet is laminated to a soda-lime glass after irradiating an active energy beam of wavelength 365 nm with an integrated light amount of 2000 to 4000 mJ / cm², the adhesive strength on the surface of the soda-lime glass at 23°C 50% RH, peel angle 180°, and peel speed 300 mm / min is 1 N / cm or more. Claim 13 An adhesive sheet having a release film having a configuration formed by laminating an active energy beam curable adhesive sheet for a flexible display described in any one of claims 1 to 12 and a release film. Claim 14 An adhesive sheet having a release film, wherein the release film is a polyester-based film, and the peel strength of the active energy line curable adhesive sheet for a flexible display after irradiating an active energy line of wavelength 365 nm with an integrated light amount of 2000 to 4000 mJ / cm² is 0.1 N / cm or less at a peel angle of 180° and a peel speed of 300 mm / min. Claim 15 A laminate having a configuration in which a release film and a member for configuring an image display device having a height difference of 2 μm or more on the laminated surface are laminated with an active energy beam curable adhesive sheet for a flexible display described in any one of claims 1 to 12. Claim 16 A method for manufacturing a laminate, wherein a release film and a member for configuring an image display device having a height difference of 2 μm or more on the laminated surface are laminated by interposing an active energy beam curable adhesive sheet for a flexible display described in any one of claims 1 to 12, and active energy beam irradiation is performed on the adhesive sheet by passing the release film through the release film from the release film side. Claim 17 A laminated sheet having a configuration formed by laminating an active energy beam curable adhesive sheet for a flexible display described in any one of claims 1 to 12 and another adhesive sheet. Claim 18 In claim 17, the other adhesive sheet is a laminated sheet having a gel fraction of 70% or more, a thickness of 0.8 mm to 1.5 mm, and a maximum point of loss tangent obtained by dynamic viscoelasticity measurement in a shear mode of 1 Hz frequency, which is -25°C or lower. Claim 19 A laminate for an image display device having a configuration in which two image display device components are laminated with an active energy beam curable adhesive sheet for a flexible display described in any one of claims 1 to 12, and at least one of the image display device components has a step difference of 2 μm or more on the contact surface with the adhesive sheet. Claim 20 A laminate for an image display device according to claim 19, wherein at least one of the members for configuring the image display device is a resin sheet or thin film glass having one or more resins selected from the group consisting of urethane resin, cycloolefin resin, triacetylcellulose resin, (meth)acrylate resin, epoxy resin, and polyimide resin as the main component. Claim 21 A flexible image display device having a laminate for an image display device as described in claim 19. Claim 22 An adhesive sheet for a flexible display having an adhesive layer formed from an adhesive composition containing a (meth)acrylic polymer (A), a crosslinking agent (B), and a polymerization initiator (C), wherein the sheet has a thickness of 15 μm or more and 50 μm or less, is characterized in that when laminated to a member for constructing an image display device having a step difference of 2 to 10 μm at a interval of 10 mm or less under the following lamination conditions, there is no foaming around the step difference, wherein the (meth)acrylic polymer (A) is composed of copolymer monomer components in which the glass transition temperature of repeating units derived from (meth)acrylic acid esters possessed by the (meth)acrylic polymer (A) is all -70 to 20°C, and the crosslinking agent (B) comprises a polyfunctional (meth)acrylate having two or more (meth)acryloyl groups, and the polyfunctional (meth)acrylate An adhesive sheet for a flexible display, wherein the content is 0.5 parts by weight or more and 10 parts by weight or less per 100 parts by weight of a (meth)acrylic polymer (A), and the content of the polymerization initiator (C) is 0.5 parts by weight or more and 5 parts by weight or less per 100 parts by weight of the (meth)acrylic polymer (A). (Lamination conditions) a) Ultraviolet light is irradiated onto an adhesive sheet with a thickness of 15 to 50 μm so that the integrated light amount of 365 nm is 2000 to 4000 mJ / cm². b) The adhesive sheet is vacuum laminated to the surface of a substrate having a step difference of 2 to 10 μm at a distance of 10 mm or less under the conditions of a press pressure of 0.2 MPa and 30 seconds. c) Autoclave treatment is performed under the conditions of 70°C, atmospheric pressure of 0.45 MPa and 20 minutes. Claim 23 A method for manufacturing a laminate for an image display device having a configuration in which two image display device constituent members 1 and 2 are laminated with an active energy beam curable adhesive sheet interposed therebetween, wherein the method comprises the following steps 1 to 3, and is characterized by performing steps 1 and 2, and then performing step 3. Step 1: One surface of an active energy beam curable adhesive sheet for a flexible display described in any one of claims 1 to 12 is laminated to an image display device constituent member 1. Step 2: An active energy beam is irradiated to cure the active energy beam curable adhesive sheet for a flexible display described in any one of claims 1 to 12. Step 3: An image display device constituent member 2 is laminated to the other surface of the adhesive sheet to form a laminate. Claim 24 A method for manufacturing a laminate for an image display device according to claim 23, wherein in process 3 above, the adhesive sheet is heated to a temperature of 50°C or higher and 80°C or lower to hot melt, and a member 2 for configuring an image display device is laminated to form a laminate. Claim 25 A method for manufacturing a laminate for an image display device according to claim 23, wherein, after process 3, additionally, process 4 involves performing a heat treatment on the laminate to hot-melt the adhesive sheet. Claim 26 A method for manufacturing a laminate for an image display device according to claim 25, wherein in the above process 4, the heat treatment is characterized by heating the laminate to a temperature of 40°C or higher and 90°C or lower, and applying an atmospheric pressure of 0.2 MPa or higher and 0.8 MPa or lower for 5 minutes or more. Claim 27 A method for manufacturing a laminate for an image display device, wherein, in claim 25, processes 1 to 4 are carried out in the order of processes 1, 2, 3, and 4. Claim 28 A method for manufacturing a laminate for an image display device according to claim 23, characterized in that at least one of the image display device configuring member 1 or image display device configuring member 2 has a step difference of 2 μm or more on the contact surface with the adhesive sheet. Claim 29 delete Claim 30 delete Claim 31 delete Claim 32 delete

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