Adhesive sheet, repeated bending laminated member, and repeated bending device

Abstract

The present invention provides an adhesive sheet, a repeatedly bent laminated component, and a repeatedly bent device that exhibit excellent bending resistance during repeated bending and good laser cutting processability. The adhesive sheet (1) is an adhesive sheet (1) having an adhesive layer (11) for bonding one bending component (21) constituting the repeatedly bent device to another bending component (22). The adhesive sheet (1) has a strain of 10% or more and 120% or less when subjected to a pressure of 10 kPa for 600 seconds at a temperature of 23°C and a frequency of 1 Hz according to the torsion shear method of JIS K7244-6. The adhesive sheet (1) has an adhesion force of 5 N / 25 mm or more to soda-lime glass.

Description

Technical Field

[0001] This invention relates to adhesive sheets for repetitive bending devices, as well as repetitive bending laminates and repetitive bending devices. Background Technology

[0002] In recent years, a flexible display has been proposed for the display body (showpiece) of electronic devices. In addition to displays that are curved in only one step, a repeatedly bending display for repeated bending (folding) applications has also been proposed.

[0003] For the aforementioned repeatedly bent display, it is possible to consider using an adhesive layer to bond one bendable component (bending component) to another bending component constituting the bendable display. However, when using conventional adhesive sheets for repeatedly bent displays, problems such as lifting and peeling occur at the interface between the adhesive layer and the adhered object.

[0004] Patent Document 1 discloses an adhesive that addresses the technical problem of preventing the adhesive layer from lifting and peeling even when repeatedly bent. This adhesive comprises a substance formed by crosslinking a (meth)acrylate copolymer formed by copolymerizing specified monomers using a crosslinking agent.

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2016-108555 Summary of the Invention

[0006] (a) Technical problems to be solved In order to obtain a repeatedly bending device from a repeatedly bending laminate formed by bonding one bending member to another using an adhesive layer, the end faces of the repeatedly bending laminate should sometimes be shaped. One method for this is laser cutting.

[0007] However, if the ends of a repeatedly bent laminated component using a conventional adhesive as described in Patent Document 1 are laser-cut, the adhesive may seep out from the end face. To prevent this, the amount of crosslinking agent can be increased to enhance the cohesive force of the adhesive, but this would reduce the adhesion of the adhesive layer to the bent component, making it prone to lifting or peeling during repeated bending.

[0008] Furthermore, even when using adhesives such as those described in Patent Document 1, as the number of times the device is repeatedly bent increases, it is prone to lifting and peeling at the bent portion, and the bending resistance tends to decrease. One reason for this is believed to be that at the bent portion, the adhesive layer deforms with the stress change of the adhesive, making it difficult to return to its original state.

[0009] To prevent this, one could consider increasing the amount of crosslinking agent to enhance the cohesive force of the adhesive. However, this would reduce the original adhesive force and decrease the bending resistance.

[0010] The present invention was implemented in view of the above-mentioned practical situation, and its purpose is to provide an adhesive sheet, a repeatedly bent laminated component, and a repeatedly bent device that exhibit excellent bending resistance during repeated bending and good laser cutting processability. Furthermore, the present invention also aims to provide an adhesive sheet, a repeatedly bent laminated component, and a repeatedly bent device that exhibit excellent bending resistance even with a large number of repeated bending cycles, where the state of the adhesive layer does not easily change.

[0011] (II) Technical Solution To achieve the above objectives, firstly, the present invention provides an adhesive sheet having an adhesive layer for bonding one bending member constituting a repeatedly bending device to another bending member, characterized in that, when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 23°C and a frequency of 1 Hz according to the torsional shearing method of JIS K7244-6, the strain is 10% or more and 120% or less, and the adhesive force of the adhesive sheet to soda-lime glass is 5 N / 25 mm or more (Invention 1).

[0012] Second, the present invention provides an adhesive sheet having an adhesive layer for bonding one bending member constituting a repeatedly bending device to another bending member, characterized in that, when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 23°C and a frequency of 1 Hz according to the torsional shear method of JIS K7244-6, the strain is 120% or less, the storage modulus G'(23) of the adhesive constituting the adhesive layer at 23°C is 0.30 MPa or less, and the adhesive force of the adhesive sheet to soda-lime glass is 5 N / 25 mm or more (Invention 2).

[0013] Third, the present invention provides an adhesive sheet having an adhesive layer for bonding one bending member constituting a repeatedly bending device to another bending member, characterized in that the strain of the adhesive layer when subjected to a pressure of 10 kPa for 600 seconds at a temperature of 23°C and a frequency of 1 Hz by the torsional shear method according to JIS K7244-6 is 120% or less, and the storage modulus G'(23) of the adhesive constituting the adhesive layer at 23°C is 0.05 MPa or more and 0.25 MPa or less (Invention 3).

[0014] Fourth, the present invention provides an adhesive sheet having an adhesive layer for bonding one bending member constituting a repeatedly bending device to another bending member, characterized in that, when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 23°C and a frequency of 1Hz according to the torsional shear method of JIS K7244-6, the strain is 120% or less, the storage modulus G'(-20) of the adhesive constituting the adhesive layer at -20°C is 1.5 MPa or less, and the adhesive sheet has an adhesion force of 5 N / 25 mm or more to soda-lime glass (Invention 4).

[0015] In the aforementioned inventions (Inventions 1-4), the adhesive layer possesses a specified hardness, specified flexibility, and tightness in adhering to bending components. When the repeatedly bent laminated component with the adhesive layer is repeatedly bent, it is less prone to lifting and peeling at the interface between the adhesive layer and the bending component, thus achieving excellent bending resistance. Furthermore, when the end face of the repeatedly bent laminated component with the adhesive layer is laser-cut to shape the end face, adhesive leakage from the end face can be suppressed, resulting in excellent laser-cutting machinability.

[0016] Fifth, the present invention provides an adhesive sheet having an adhesive layer for bonding one bending member constituting a repeatedly bending device to another bending member, characterized in that, when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 60°C and a frequency of 1 Hz according to the torsion shear method of JIS K7244-6, the strain is 18% or more and 140% or less, and the adhesive force of the adhesive sheet to soda-lime glass is 5 N / 25 mm or more (Invention 5).

[0017] Sixth, the present invention provides an adhesive sheet having an adhesive layer for bonding one bending member constituting a repeatedly bending device to another bending member, characterized in that, when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 60°C and a frequency of 1Hz according to the torsional shear method of JIS K7244-6, the strain is 18% or more, and the rate of change of elastic modulus obtained by the following formula (1) based on the storage modulus G'(-20) of the adhesive constituting the adhesive layer at -20°C and the storage modulus G'(40) at 40°C is 610% or more and 10000% or less (Invention 6).

[0018] Rate of change of elastic modulus (%) = (G'(-20) / G'(40)) × 100 …(1) Seventh, the present invention provides an adhesive sheet having an adhesive layer for bonding one bending member constituting a repeatedly bending device to another bending member, characterized in that, when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 60°C and a frequency of 1Hz according to the torsional shear method of JIS K7244-6, the strain is 140% or less, the storage modulus G'(-20) of the adhesive constituting the adhesive layer is 1.5 MPa or less at -20°C, and the adhesive sheet has an adhesion force of 5 N / 25 mm or more to soda-lime glass (Invention 7).

[0019] In the aforementioned inventions (Inventions 5-7), the adhesive layer possesses a specified hardness, specified flexibility, and a tight fit to the bending member. Therefore, even if the repeatedly bent laminated member with this adhesive layer undergoes a high number of bending cycles (e.g., 400,000 cycles), the shape (thickness, etc.) of the adhesive layer at the bending portion easily returns to its original state, and the state of the adhesive layer is not easily altered. As a result, lifting and peeling are less likely to occur at the interface between the adhesive layer and the bending member, resulting in excellent bending resistance.

[0020] In the above inventions (Inventions 1 to 7), it is preferable that the adhesive constituting the adhesive layer has a storage modulus G'(-20) of 0.001 MPa or more and 1.5 MPa or less at -20°C (Invention 8).

[0021] In the above inventions (Inventions 1 to 8), it is preferable that the adhesive constituting the adhesive layer has a storage modulus G'(40) of 0.001 MPa or more and 1 MPa or less at 40°C (Invention 9).

[0022] In the above inventions (Inventions 1 to 9), it is preferable that the rate of change of elastic modulus obtained by the following formula (1) based on the storage modulus G'(-20) of the adhesive constituting the adhesive layer at -20°C and the storage modulus G'(40) at 40°C is 100% or more and 10000% or less (Invention 10).

[0023] Rate of change of elastic modulus (%) = (G'(-20) / G'(40)) × 100 …(1) In the above inventions (Inventions 1 to 10), it is preferable that the rate of change of elastic modulus obtained by the following formula (2) based on the storage modulus G'(-20) of the adhesive constituting the adhesive layer at -20°C and the storage modulus G'(23) at 23°C is 100% or more and 10000% or less (Invention 11).

[0024] Rate of change of elastic modulus (%) = (G'(-20) / G'(23)) × 100 …(2) In the above inventions (Inventions 1-4, 8-11), it is preferable that the elastic modulus change rate obtained by the following formula (3) based on the storage modulus G'(23) of the adhesive constituting the adhesive layer at 23°C and the storage modulus G'(40) at 40°C is 10% or more and 10000% or less (Invention 12).

[0025] Rate of change of elastic modulus (%) = (G'(23) / G'(40)) × 100 …(3) In the above inventions (Inventions 5 to 7), it is preferable that the adhesive constituting the adhesive layer has a storage modulus G'(23) of 0.001 MPa or more and 1 MPa or less at 23°C (Invention 13).

[0026] In the above inventions (Inventions 5-7, 13), it is preferable that the elastic modulus change rate obtained by the following formula (3) based on the storage modulus G'(23) of the adhesive constituting the adhesive layer at 23°C and the storage modulus G'(40) at 40°C is 100% or more and 10000% or less (Invention 14).

[0027] Rate of change of elastic modulus (%) = (G'(23) / G'(40)) × 100 …(3) In the above-mentioned inventions (Inventions 5-7, 13, 14), it is preferable that the strain when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 60°C and a frequency of 1 Hz according to the torsional shear method of JIS K7244-6 is defined as CS1(%), and the strain when the adhesive layer is placed at a temperature of 60°C and a frequency of 10 kPa for 600 seconds at a temperature of 60°C without pressure after being subjected to a torsional shear method of JIS K7244-6 is defined as CS2(%), the ratio of CS2 to CS1, i.e., the recovery rate, is 91% or more (Invention 15).

[0028] In the above inventions (Inventions 1 to 15), it is preferable that the gel fraction of the adhesive constituting the adhesive layer is 40% or more and 100% or less (Invention 16).

[0029] In the above inventions (Inventions 1 to 16), the adhesive constituting the adhesive layer is preferably an acrylic adhesive (Invention 17).

[0030] In the above inventions (Inventions 1 to 17), it is preferred that the adhesive constituting the adhesive layer is an adhesive formed by thermally crosslinking and curing an adhesive composition containing (meth)acrylate polymer (A), crosslinking agent (B) and active energy ray curable component (C) with active energy ray (Invention 18).

[0031] In the above inventions (Inventions 1-18), it is preferred that the adhesive sheet has two release tabs, and the adhesive layer is held by the release tabs in such a way that it contacts the release surfaces of the two release tabs (Invention 19).

[0032] Eighth, the present invention provides a repeatedly bent laminated component, characterized in that it comprises: a bending component and another bending component constituting a repeatedly bent device, and an adhesive layer for bonding the one bending component and the other bending component together, wherein the adhesive layer is the adhesive layer of the adhesive sheet (Invention 1-19) (Invention 20).

[0033] In the above invention (Invention 20), it is preferable that the end face of the repeatedly bent and stacked member is formed by laser cutting (Invention 21).

[0034] Ninth, the present invention provides a repeatedly bending device, characterized in that it comprises the repeatedly bending stacked member (Invention 20, 21) (Invention 22).

[0035] (III) Beneficial Effects The adhesive sheet, repeatedly bent laminate, and repeatedly bent device of the present invention exhibit excellent bending resistance during repeated bending and good laser cutting processability. Furthermore, even with a large number of repeated bending cycles, the adhesive layer of the adhesive sheet, repeatedly bent laminate, and repeatedly bent device of the present invention does not easily change, demonstrating excellent bending resistance. Attached Figure Description

[0036] Figure 1 This is a cross-sectional view of an adhesive sheet according to one embodiment of the present invention.

[0037] Figure 2 This is a cross-sectional view of a repeatedly bent laminated member according to one embodiment of the present invention.

[0038] Explanation of reference numerals in the attached figures 1: Adhesive sheet; 11: Adhesive layer; 12a, 12b: Release sheet; 2: Repeatedly bent laminated member; 21: First bending member; 22: Second bending member. Detailed Implementation

[0039] The following describes the embodiments of the present invention.

[0040] [Adhesive sheet] One embodiment of the present invention includes an adhesive sheet comprising an adhesive layer for bonding one bending member to another bending member constituting a repetitive bending device. The repetitive bending device and the bending member will be described later. Furthermore, the repetitive bending laminate in this embodiment has a configuration in which one bending member is bonded to another bending member using the aforementioned adhesive layer, thus constituting a repetitive bending device.

[0041] For the adhesive sheet of this embodiment, firstly, preferably, the strain (creep strain; CS0) when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 23°C and a frequency of 1Hz according to the torsional shear method of JIS K7244-6 is 10% or more and 120% or less, and the adhesion of the adhesive sheet to the soda-lime glass is 5 N / 25 mm or more (sometimes the above properties are referred to together as "properties of the first embodiment").

[0042] Second, preferably: when the strain (creep strain; CS0) of the adhesive layer is applied to the adhesive layer at a temperature of 23°C and a frequency of 1Hz for 600 seconds using the torsional shear method according to JIS K7244-6, the strain is 120% or less; the storage modulus G'(23) of the adhesive constituting the adhesive layer at 23°C (sometimes marked as "G'(23)" in this specification) is 0.30MPa or less; and the adhesion of the adhesive sheet to the soda-lime glass is 5N / 25mm or more (sometimes the above properties are referred to together as "properties of the second embodiment").

[0043] Third, preferred: when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 23°C and a frequency of 1 Hz by the torsional shear method according to JIS K7244-6, the strain (creep strain; CS0) is 120% or less, and the G'(23) of the adhesive constituting the adhesive layer is 0.05 MPa or more and 0.25 MPa or less (sometimes the above properties are referred to together as "the properties of the third option").

[0044] Fourth, preferably: when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 23°C and a frequency of 1Hz according to the torsional shear method of JIS K7244-6, the strain (creep strain; CS0) is 120% or less; the storage modulus G'(-20) of the adhesive constituting the adhesive layer at -20°C (sometimes marked as "G'(-20)" in this specification) is 1.5 MPa or less; and the adhesion of the adhesive sheet to the soda-lime glass is 5 N / 25 mm or more (sometimes the above properties are referred to together as "the properties of the fourth embodiment").

[0045] Details of the method for determining creep strain in this specification are shown in the test examples described later. Furthermore, the method for determining the storage modulus G' in this specification is also shown in the test examples described later.

[0046] The adhesive force in this specification refers to the adhesive force determined essentially by the 180-degree peel method according to JIS Z0237: 2022. The test sample is set to be 25 mm wide and 100 mm long, and is attached to the object to be adhered. After being pressurized at 0.5 MPa and 50°C for 20 minutes, it is placed under normal pressure, 23°C and 50%RH for 24 hours, and then the value is measured at a peeling speed of 300 mm / min.

[0047] The adhesive layer of the adhesive sheet in this embodiment achieves a specified hardness by reducing the creep strain (CS0) in the physical properties of the first to fourth embodiments to below 120%. As a result, when the end face of a repeatedly bent laminated component with this adhesive layer is shaped by laser cutting, adhesive leakage from the end face can be suppressed. Therefore, the adhesive sheet of this embodiment exhibits excellent laser cutting machinability.

[0048] Furthermore, the adhesive layer of the adhesive sheet in this embodiment achieves a specified flexibility by making the creep strain (CS0) in the physical properties of the first embodiment 10% or more. Moreover, by making the aforementioned adhesion force 5 N / 25 mm or more, a tight fit to the bending member can be ensured. As a result, even when the laminated member is repeatedly bent, it is not easy for lift-off and peeling to occur at the interface between the adhesive layer and the bending member, exhibiting excellent bending resistance.

[0049] The adhesive layer of the adhesive sheet in this embodiment achieves a specified flexibility by setting G'(23) in the physical properties of the second embodiment to 0.30 MPa or less. Furthermore, by setting the adhesion force to 5 N / 25 mm or more, a tight fit to the bending member can be ensured. As a result, even when the repeatedly bent laminated member is repeatedly bent, it is not easy for the adhesive layer to lift and peel off at the interface between the adhesive layer and the bending member, exhibiting excellent bending resistance.

[0050] The adhesive layer of the adhesive sheet in this embodiment exhibits excellent flexibility and adhesion by setting G'(23) in the physical property of the third embodiment to below 0.25 MPa. Therefore, even when the laminated component is repeatedly bent, it is not prone to lifting or peeling at the interface between the adhesive layer and the bending component, resulting in excellent bending resistance. Furthermore, by setting G'(23) in the physical property of the third embodiment to above 0.05 MPa, the adhesive layer acquires a specified hardness, which, combined with the aforementioned creep strain (CS0), further enhances laser cutting machinability.

[0051] The adhesive layer of the adhesive sheet in this embodiment achieves a specified flexibility by setting G'(-20) in the physical properties of the fourth embodiment to 1.5 MPa or less. Furthermore, by setting the aforementioned adhesive force to 5 N / 25 mm or more, a tight fit to the bending member is ensured. As a result, even when the laminated member is repeatedly bent, it is not prone to lifting or peeling at the interface between the adhesive layer and the bending member, exhibiting excellent bending resistance.

[0052] From the perspective of laser cutting processability, the creep strain (CS0) is more preferably 100% or less, particularly preferably 75% or less, even more preferably 50% or less, and preferably 40% or less. Considering bending resistance, the lower limit of the creep strain (CS0) is preferably 10% or more, more preferably 12% or more, particularly preferably 14% or more, and even more preferably 16% or more.

[0053] From the perspective of bending resistance, the physical property G'(23) in the second embodiment is more preferably 0.27 MPa or less, particularly preferably 0.24 MPa or less, further preferably 0.22 MPa or less, and preferably 0.2 MPa or less. Similarly, from the perspective of bending resistance, the physical property G'(23) in the third embodiment is more preferably 0.27 MPa or less, particularly preferably 0.24 MPa or less, further preferably 0.22 MPa or less, and preferably 0.2 MPa or less. From the perspective of laser cutting processability, the lower limit value of the above-mentioned G'(23) is preferably 0.05 MPa or more, more preferably 0.06 MPa or more, particularly preferably 0.07 MPa or more, and further preferably 0.08 MPa or more.

[0054] Furthermore, from the perspective of flexural strength, the G'(-20) of the adhesive constituting the adhesive layer is more preferably 1.5 MPa or less, particularly preferably 1.3 MPa or less, even more preferably 1.1 MPa or less, and most preferably 1 MPa or less. From the perspective of laser cutting processability, the lower limit of the G'(-20) is preferably 0.001 MPa or more, more preferably 0.01 MPa or more, particularly preferably 0.1 MPa or more, even more preferably 0.2 MPa or more, and most preferably 0.4 MPa or more.

[0055] From the perspective of bending resistance, the above-mentioned adhesion is preferably 5N / 25mm or more, more preferably 8N / 25mm or more, particularly preferably 10N / 25mm or more, and from the perspective of balancing bending resistance and laser cutting processability, it is even more preferably 12N / 25mm or more.

[0056] Furthermore, the upper limit of the aforementioned adhesive force is preferably 100 N / 25 mm or less, more preferably 60 N / 25 mm or less, particularly preferably 40 N / 25 mm or less, even more preferably 30 N / 25 mm or less, and most preferably 20 N / 25 mm or less. This provides good reprocessability, allowing the adhered material to be reused in the event of an adhesion error.

[0057] The storage modulus G'(40) of the adhesive constituting the adhesive layer at 40°C (sometimes marked as "G'(40)" in this specification) is preferably 0.001~1 MPa, more preferably 0.01~0.6 MPa, particularly preferably 0.03~0.4 MPa, further preferably 0.04~0.2 MPa, and most preferably 0.05~0.15 MPa. As a result, the adhesive exhibits good hardness and flexibility, and its laser cutting machinability and bending resistance are significantly improved.

[0058] Based on the adhesives G'(-20) and G'(40) constituting the adhesive layer described above, the elastic modulus change rate (RC1) obtained from the following formula (1) is preferably 100~10000%, more preferably 250~5000%, particularly preferably 400~1000%, further preferably 500~900%, and preferably 600~820%, especially preferably 650~795%. Therefore, the adhesive readily possesses good hardness and flexibility, and exhibits superior laser cutting machinability and bending resistance.

[0059] The rate of change of elastic modulus (RC1) (%) = (G'(-20) / G'(40)) × 100 …(1) Based on the adhesives G'(-20) and G'(23) constituting the adhesive layer described above, the elastic modulus change rate (RC2) obtained from the following formula (2) is preferably 100~10000%, more preferably 200~5000%, particularly preferably 300~1000%, further preferably 350~600%, preferably 400~550%, and especially preferably 440~525%. Therefore, the adhesive readily possesses good hardness and flexibility, and exhibits superior laser cutting machinability and bending resistance.

[0060] The rate of change of elastic modulus (RC2) (%) = (G'(-20) / G'(23)) × 100 …(2) Based on the adhesives G'(23) and G'(40) constituting the adhesive layer described above, the elastic modulus change rate (RC3) obtained from the following formula (3) is preferably 10~10000%, more preferably 40~5000%, particularly preferably 80~1000%, further preferably 100~500%, and preferably 120~300%, especially preferably 130~200%. Therefore, the adhesive readily possesses good hardness and flexibility, and exhibits superior laser cutting machinability and bending resistance.

[0061] Rate of change of elastic modulus (RC3) (%) = (G'(23) / G'(40)) × 100 …(3) For the adhesive sheet of this embodiment, fifthly, preferably, the strain (creep strain; CS1) when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 60°C and a frequency of 1Hz according to the torsional shear method of JIS K7244-6 is 18% or more and 140% or less, and the adhesion of the adhesive sheet to the soda-lime glass is 5 N / 25 mm or more (sometimes the above properties are referred to together as "the properties of the fifth embodiment").

[0062] Sixth, preferred: the strain (creep strain; CS1) when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 60°C and a frequency of 1Hz according to the torsional shear method of JIS K7244-6 is 18% or more, and the elastic modulus change rate (RC1) obtained from the above formula (1) according to the adhesive G'(-20) and G'(40) constituting the adhesive layer is 610% or more and 10000% or less (sometimes the above properties are referred to together as "the properties of the sixth option").

[0063] Seventh, preferably: when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 60°C and a frequency of 1Hz according to the torsional shear method of JIS K7244-6, the strain (creep strain; CS1) is 140% or less, the G'(-20) of the adhesive constituting the adhesive layer is 1.5 MPa or less, and the adhesion of the adhesive sheet to soda-lime glass is 5 N / 25 mm or more (sometimes the above properties are referred to together as "the properties of the seventh embodiment").

[0064] Among these schemes, the adhesives in schemes five through seven have low surface viscosity at room temperature, which makes the measuring fixture prone to slippage when measuring creep strain. This can easily lead to deviations in the measured values ​​at room temperature. On the other hand, it is known that high-accuracy measurement results can be obtained by performing the measurement at higher temperatures. That is, in schemes five through seven, the creep strain at 60°C was found to be a material property value that contributes to solving the technical problem.

[0065] The adhesive layer of the adhesive sheet in this embodiment achieves a specified hardness by reducing the creep strain (CS1) in the physical properties of the fifth embodiment to 140% or less. Furthermore, by reducing this creep strain to 18% or more, it achieves a certain degree of flexibility. Therefore, even after numerous bending cycles (e.g., 400,000 cycles), the shape (thickness, etc.) of the adhesive layer at the bending points easily returns to its original state, and the state of the adhesive layer is less prone to change. Moreover, by achieving an adhesion strength of 5 N / 25 mm or more, a tight fit to the bending member can be ensured. As a result, even after numerous bending cycles, lifting and peeling at the interface between the adhesive layer and the bending member are less likely to occur, resulting in excellent bending resistance.

[0066] The adhesive layer of the adhesive sheet in this embodiment exhibits a certain degree of flexibility by achieving a creep strain (CS1) of 18% or more in the physical properties of the sixth embodiment, thus easily demonstrating good adhesion. Furthermore, by maintaining a rate of change of elastic modulus (RC1) of 610% or more and 10000% or less, it possesses a specified hardness while maintaining good adhesion. Therefore, even after numerous bending cycles (e.g., 400,000 cycles), the shape (thickness, etc.) of the adhesive layer at the bending points easily returns to its original state, and the state of the adhesive layer is not easily altered. In addition, good adhesion to the bending member is also ensured. As a result, even after numerous bending cycles, lifting and peeling at the interface between the adhesive layer and the bending member are less likely to occur, resulting in excellent bending resistance.

[0067] The adhesive layer of the adhesive sheet in this embodiment achieves a specified hardness by reducing the creep strain (CS1) in the physical properties of the seventh embodiment to 140% or less. Furthermore, it achieves a certain degree of flexibility by reducing G'(-20) to 1.5 MPa or less. Therefore, even after numerous bending cycles (e.g., 400,000 cycles), the shape (thickness, etc.) of the adhesive layer at the bending points easily returns to its original state, and the state of the adhesive layer is not easily altered. Moreover, by achieving an adhesion strength of 5 N / 25 mm or more, a tight fit to the bending member can be ensured. As a result, even after numerous bending cycles, lifting and peeling at the interface between the adhesive layer and the bending member are less likely to occur, resulting in excellent bending resistance.

[0068] From the perspective of suppressing changes in the state of the adhesive layer, the creep strain (CS1) is preferably 140% or less, more preferably 110% or less, particularly preferably 90% or less, further preferably 70% or less, and most preferably 50% or less. Considering the adhesion, the lower limit of the creep strain (CS1) is preferably 18% or more, more preferably 19% or more, particularly preferably 20% or more, and further preferably 21% or more.

[0069] From the perspective of the tightness and even the bending resistance of the bending member, the above-mentioned adhesive force is preferably 5N / 25mm or more, more preferably 8N / 25mm or more, particularly preferably 10N / 25mm or more, and even more preferably 12N / 25mm or more. In addition, the upper limit of the above-mentioned adhesive force is the same as that of the first to fourth embodiments described above.

[0070] From the perspective of flexural resistance, the rate of change of elastic modulus (RC1) in the physical properties of the sixth embodiment is more preferably 610~10000%, more preferably 625~5000%, particularly preferably 640~1000%, further preferably 660~800%, preferably 670~770%, and especially preferably 680~740%. Furthermore, from the perspective of flexural resistance, the rate of change of elastic modulus (RC1) in the physical properties of the fifth and seventh embodiments is preferably 100~10000%, more preferably 300~5000%, particularly preferably 500~1000%, further preferably 600~800%, preferably 640~770%, and especially preferably 680~740%.

[0071] From the perspective of flexibility and even adhesion, the G'(-20) of the adhesive constituting the adhesive layer is preferably 1.5 MPa or less, more preferably 1.2 MPa or less, particularly preferably 1.1 MPa or less, and even more preferably 1 MPa or less. From the perspective of suppressing changes in the state of the adhesive layer, the lower limit of G'(-20) is preferably 0.001 MPa or more, more preferably 0.01 MPa or more, particularly preferably 0.1 MPa or more, even more preferably 0.2 MPa or more, and most preferably 0.4 MPa or more.

[0072] The adhesive G'(40) constituting the adhesive layer is preferably 0.001~1 MPa, more preferably 0.01~0.6 MPa, particularly preferably 0.03~0.4 MPa, even more preferably 0.04~0.2 MPa, and most preferably 0.05~0.15 MPa. This makes it easier to satisfy the aforementioned rate of change of elastic modulus (RC1).

[0073] From the perspective of flexibility and even adhesion, the adhesive G'(23) constituting the adhesive layer is preferably 1 MPa or less, more preferably 0.7 MPa or less, particularly preferably 0.5 MPa or less, further preferably 0.3 MPa or less, and most preferably 0.25 MPa or less. From the perspective of suppressing changes in the state of the adhesive layer, the lower limit of G'(23) is preferably 0.001 MPa or more, more preferably 0.01 MPa or more, particularly preferably 0.03 MPa or more, further preferably 0.05 MPa or more, and most preferably 0.07 MPa or more.

[0074] Based on G'(-20) and G'(23) of the adhesive constituting the adhesive layer, the elastic modulus change rate (RC2) obtained from the above formula (2) is preferably 100~10000%, more preferably 200~5000%, particularly preferably 300~1000%, further preferably 350~800%, further preferably 400~600%, and even more preferably 450~530%. Therefore, the adhesive easily possesses good hardness and flexibility, and its bending resistance is even more excellent.

[0075] Based on G'(23) and G'(40) of the adhesive constituting the adhesive layer, the elastic modulus change rate (RC3) obtained from the above formula (3) is preferably 10~10000%, more preferably 40~5000%, particularly preferably 80~1000%, further preferably 100~500%, further preferably 110~200%, and even more preferably 120~150%. Therefore, the adhesive easily possesses good hardness and flexibility, and its bending resistance is even more excellent.

[0076] When the strain (creep strain) when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 60°C and a frequency of 1 Hz according to the torsional shear method of JIS K7244-6 is defined as CS1 (%), and the strain (creep strain) when the adhesive layer is placed at a temperature of 60°C and a frequency of 1 Hz for 600 seconds after being subjected to a pressure of 10 kPa for 600 seconds at a temperature of 60°C without pressure is defined as CS2 (%), the ratio of CS2 to CS1, i.e., the recovery rate ((CS2 / CS1)×100) is preferably 91% or more, more preferably 91.5% or more, particularly preferably 92% or more, and even more preferably 92.5% or more.

[0077] By achieving the recovery rate described above, the state, including the thickness of the adhesive layer, can be easily restored to its original state, making it less prone to change in the state of the adhesive layer. Based on the adhesive sheet that satisfies the above-described physical properties, the aforementioned high recovery rate can be achieved.

[0078] In addition, there is no particular limit to the upper limit of the recovery rate mentioned above, which is a maximum of 100%, but it is generally preferred to be below 99%, particularly preferred to be below 98%, and even more preferred to be below 97%.

[0079] The gel fraction of the adhesive constituting the adhesive layer is preferably 40-100%, more preferably 50-99%, particularly preferably 60-95%, further preferably 70-90%, and most preferably 80-87%. This readily satisfies the aforementioned creep strain and storage modulus G', and exhibits the prescribed cohesive force, more effectively suppressing adhesive exudation during laser cutting, resulting in superior laser cutting processability. Furthermore, the adhesive layer's state is less prone to change, leading to superior flexural resistance. The method for determining the gel fraction in this specification is shown in the experimental examples described later.

[0080] The adhesive constituting the adhesive layer may satisfy the aforementioned physical properties. Examples of such adhesives include acrylic adhesives, polyester adhesives, polyurethane adhesives, rubber adhesives, and silicone adhesives, among which acrylic adhesives that readily satisfy the aforementioned physical properties are preferred.

[0081] As an acrylic adhesive, a cross-linking type is preferred, and a thermally cross-linking type is more preferred. Furthermore, as this acrylic adhesive, it is preferable to undergo active energy radiation curing. That is, the acrylic adhesive in this embodiment is particularly preferably subjected to thermal cross-linking and active energy radiation curing. In addition, from the perspective of SDGs, materials constituting this adhesive can be materials with high biomass content, materials that can be recycled or reused, or materials that have already been recycled or reused.

[0082] The adhesive in this embodiment is preferably an adhesive formed by thermally crosslinking and curing an adhesive composition (hereinafter sometimes referred to as "adhesive composition P") containing a (meth)acrylate polymer (A), a crosslinking agent (B), and an active energy radiation curable component (C). This adhesive readily satisfies the aforementioned physical properties. Furthermore, in this specification, (meth)acrylate refers to acrylic acid and methacrylic acid. The same applies to other similar terms. Additionally, "polymer" also includes the concept of "copolymer."

[0083] 1. Components of the adhesive composition P (1) (Meth)acrylate polymer (A) The (meth)acrylate polymer (A) preferably contains alkyl (meth)acrylate and monomers with reactive functional groups (monomers with reactive functional groups) as monomer units constituting the polymer.

[0084] The (meth)acrylate polymer (A) exhibits good adhesion by containing alkyl (meth)acrylate as a monomer unit constituting the polymer. Preferably, the alkyl (meth)acrylate is an alkyl (meth)acrylate with 1 to 20 carbon atoms. The alkyl group can be linear, branched, or have a cyclic structure.

[0085] Alkyl methacrylates having 1 to 20 carbon atoms as the alkyl group include, for example, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, n-decyl methacrylate, n-dodecyl methacrylate, myristyl methacrylate, palmitate methacrylate, and stearate methacrylate. Among these, alkyl methacrylates having 1 to 8 carbon atoms are preferred from the perspective of easily satisfying the above-mentioned physical properties, and alkyl methacrylates having 4 to 8 carbon atoms are particularly preferred. Specifically, n-butyl methacrylate or 2-ethylhexyl methacrylate are preferred, and n-butyl methacrylate or 2-ethylhexyl methacrylate are particularly preferred. Furthermore, these alkyl methacrylates can be used alone or in combination of two or more.

[0086] The (meth)acrylate polymer (A) preferably contains 60-99.99% by mass, more preferably 80-99.9% by mass, particularly preferably 90-99.5% by mass, and even more preferably 95-99.2% by mass of alkyl (meth)acrylates having 1-20 carbon atoms as monomer units constituting the polymer. This readily satisfies the aforementioned physical properties. Furthermore, other monomer components can be introduced into the (meth)acrylate polymer (A) in the desired amounts.

[0087] (Meth)acrylate polymer (A) contains monomers with reactive functional groups as monomer units constituting the polymer. These reactive functional groups react with a crosslinking agent (B) described later, thereby forming a crosslinked structure (three-dimensional network structure) to obtain an adhesive with the desired cohesive strength. This adhesive readily satisfies the aforementioned physical properties.

[0088] Monomers containing reactive functional groups that constitute the (meth)acrylate polymer (A) as monomer units of the polymer are preferably examples of monomers having an intramolecular hydroxyl group (hydroxyl-containing monomers), monomers having an intramolecular carboxyl group (carboxyl-containing monomers), and monomers having an intramolecular amino group (amino-containing monomers). These monomers containing reactive functional groups may be used individually or in combination with two or more monomers.

[0089] Among the aforementioned monomers containing reactive functional groups, hydroxyl-containing monomers or carboxyl-containing monomers are preferred, with hydroxyl-containing monomers being particularly preferred. Hydroxyl-containing monomers readily satisfy the aforementioned storage modulus G' related properties. That is, if a hydroxyl-containing monomer is used, especially one that can reduce the storage modulus G' at low temperatures, the storage modulus G' of the obtained adhesive can be easily fine-tuned.

[0090] Examples of hydroxyl-containing monomers include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, and other hydroxyalkyl methacrylates. Among these hydroxyl-containing monomers, from the perspective of satisfying the aforementioned storage modulus G', hydroxyalkyl methacrylates having a hydroxyalkyl group having 1 to 4 carbon atoms are preferred. Specifically, 2-hydroxyethyl methacrylate and 4-hydroxybutyl methacrylate are preferred examples, and 2-hydroxyethyl acrylate or 4-hydroxybutyl acrylate are particularly preferred. These hydroxyl-containing monomers can be used alone or in combination of two or more.

[0091] The (meth)acrylate polymer (A) preferably contains 0.01 to 10% by mass, more preferably 0.1 to 7% by mass, particularly preferably 0.4 to 4% by mass, and even more preferably 0.8 to 2% by mass of a monomer containing reactive functional groups as the monomer unit constituting the polymer. As a result, the adhesive obtained has moderate cohesion and readily satisfies the aforementioned physical properties, especially the storage modulus G', particularly the storage modulus G'(-20) at -20°C.

[0092] The (meth)acrylate polymer (A) preferably does not contain carboxyl-containing monomers as monomer units constituting the polymer. Since carboxyl groups are acidic components, by not containing carboxyl-containing monomers, even when there are components in the adhesive that are prone to adverse effects due to acid, such as transparent conductive films or metal films or metal meshes, these adverse effects (corrosion, changes in resistance, etc.) caused by acid can be suppressed.

[0093] Here, "free of carboxyl-containing monomers" means substantially free of carboxyl-containing monomers. Besides being completely free of carboxyl-containing monomers, it also allows the presence of carboxyl-containing monomers to a degree that will not cause corrosion of transparent conductive films or metal wiring caused by carboxyl groups. Specifically, in the (meth)acrylate polymer (A), it is permissible to contain carboxyl-containing monomers as monomer units in amounts of 0.1% by mass or less, preferably 0.01% by mass or less, and more preferably 0.001% by mass or less.

[0094] The (meth)acrylate polymer (A) may also contain other monomers as constituent units, depending on requirements. As other monomers, monomers without reactive functional groups are preferred to avoid hindering the aforementioned effects of monomers containing reactive functional groups. Examples of such monomers include, for instance, non-reactive nitrogen-containing monomers such as N-acryloylmorpholine and N-vinylpyrrolidone; alkoxyalkyl esters of (meth)acrylate such as methoxyethyl acrylate and ethoxyethyl acrylate; vinyl acetate and styrene. These other monomers may be used alone or in combination of two or more.

[0095] The polymerization form of (meth)acrylate polymer (A) can be a random copolymer or a block copolymer.

[0096] The weight-average molecular weight of the (meth)acrylate polymer (A) is preferably 100,000 to 3,000,000, more preferably 400,000 to 2,400,000, particularly preferably 600,000 to 1,800,000, further preferably 800,000 to 1,500,000, and most preferably 900,000 to 1,200,000. This readily satisfies the aforementioned physical properties. Furthermore, the weight-average molecular weight in this specification is a value converted from standard polystyrene determined by gel permeation chromatography (GPC).

[0097] In the adhesive composition P, the (meth)acrylate polymer (A) can be used alone or in combination of two or more.

[0098] (2) Crosslinking agent (B) Crosslinking agent (B) is used as an inducing factor, such as heating, of the adhesive composition P containing crosslinking agent (B) to crosslink the (meth)acrylate polymer (A) to form a three-dimensional network structure. As a result, the cohesive strength of the obtained adhesive is increased, making it easier to satisfy the aforementioned physical properties.

[0099] As the aforementioned crosslinking agent (B), any crosslinking agent that reacts with the reactive groups present in the (meth)acrylate polymer (A) may be used. Examples include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, and ammonium salt-based crosslinking agents. Among the aforementioned crosslinking agents, isocyanate-based crosslinking agents with excellent reactivity with monomers containing reactive functional groups are preferred. Furthermore, crosslinking agent (B) may be used alone or in combination of two or more.

[0100] Isocyanate-based crosslinking agents include at least polyisocyanate compounds. Examples of polyisocyanate compounds include aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and phenylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate; their biuret forms, isocyanurate forms, and adducts as reactants with low-molecular-weight compounds containing active hydrogen, such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. From the perspective of reactivity with hydroxyl groups, trimethylolpropane-modified aromatic polyisocyanates are preferred, and trimethylolpropane-modified toluene diisocyanate or trimethylolpropane-modified phenylene diisocyanate are particularly preferred.

[0101] The content of crosslinking agent (B) in the adhesive composition P is preferably 0.01 to 1 part by mass relative to 100 parts by mass of (meth)acrylate polymer (A), more preferably 0.02 to 0.8 parts by mass, particularly preferably 0.03 to 0.6 parts by mass, further preferably 0.04 to 0.4 parts by mass, and most preferably 0.05 to 0.3 parts by mass, especially preferably 0.06 to 0.2 parts by mass. This readily satisfies the aforementioned physical properties.

[0102] (3) Active energy radiation curing component (C) It is believed that in the adhesive obtained by thermally crosslinking and curing an adhesive composition P containing an active energy radiation curable component (C), the active energy radiation curable component (C) polymerizes with each other, and the polymerized active energy radiation curable component (C) is entangled in the crosslinked structure (three-dimensional network structure) of the (meth)acrylate polymer (A). Adhesives with this high-order structure readily satisfy the aforementioned physical properties, effectively achieving a balance between bending resistance and laser cutting machinability. Furthermore, it effectively achieves a balance between a certain degree of hardness and adhesion, with even superior bending resistance.

[0103] The active energy ray curable component (C) is cured by irradiation with active energy rays. There are no particular limitations on the component, as long as it can achieve the aforementioned effects; it can be any of monomers, oligomers, or polymers, or a mixture thereof. Among these, multifunctional acrylate monomers that readily provide the adhesive properties described above are preferably preferred.

[0104] Examples of multifunctional acrylate monomers include tricyclodecanediethanol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, hydroxypentyl hydroxypentanoic acid neopentyl glycol di(meth)acrylate, dicyclopentyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified di(meth)acrylate, di(acryloyloxyethyl)isocyanurate, allylated di(meth)acrylate cyclohexyl acrylate, ethoxylated di(meth)acrylate di(meth)acrylate, ethoxylated bisphenol A diacrylate, and 9,9-bis[4-(2-acryloyloxyethoxy)phenyl] Fluorene and other 2-functional types; trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ethoxylated isocyanuric acid tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, tri-(2-(meth)acryloyloxyethyl)isocyanurate, ε-caprolactone-modified tri-(2-(meth)acryloyloxyethyl)isocyanurate, etc.; diglycerol tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, etc.; propionic acid-modified dipentaerythritol penta(meth)acrylate, etc.; dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, etc., etc. These multifunctional acrylate monomers can be used alone or in combination of two or more. Furthermore, from the perspective of excellent compatibility with (meth)acrylate polymer (A), the multifunctional acrylate monomers preferably have a molecular weight of less than 1000. By using such highly compatible multifunctional acrylate monomers, the resulting adhesives more easily meet the aforementioned physical properties.

[0105] Of the above, from the perspective of easily satisfying the above physical properties, tricyclodecanediethanol di(meth)acrylate is preferred, and tricyclodecanediethanol diacrylate is particularly preferred.

[0106] The content of the active energy ray curable component (C) in the adhesive composition P is preferably 0.1 to 18 parts by mass relative to 100 parts by mass of the (meth)acrylate polymer (A), more preferably 1 to 17 parts by mass, particularly preferably 4 to 16 parts by mass, and even more preferably 8 to 15 parts by mass. This readily satisfies the aforementioned physical properties.

[0107] (4) Photopolymerization initiator (D) When using ultraviolet light as the active energy ray to cure the adhesive composition P, it is preferable that the adhesive composition P further contains a photopolymerization initiator (D). This enables the active energy ray-curable component (C) to polymerize efficiently and reduces the polymerization and curing time as well as the amount of active energy ray irradiation.

[0108] Examples of photopolymerization initiators (D) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)one, benzophenone, and p-phenylbenzene. Ketones, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzoyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoate, oligomeric [2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]acetone], 2,4,6-trimethylbenzoyl diphenylphosphine oxide, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, etc. These photopolymerization initiators can be used alone or in combination of two or more.

[0109] The content of photopolymerization initiator (D) in the adhesive composition P is preferably 1 to 30 parts by mass relative to 100 parts by mass of the active energy ray curable component (C), more preferably 3 to 24 parts by mass, particularly preferably 6 to 18 parts by mass, and even more preferably 8 to 15 parts by mass.

[0110] (5) Various additives Various additives commonly used in acrylic adhesives can also be added to the adhesive composition P as needed, such as silane coupling agents, ultraviolet absorbers, antistatic agents, tackifiers, antioxidants, deoxidizers, colorants, infrared absorbers, light diffusing agents, rust inhibitors, light stabilizers, softeners, fillers, and refractive index modifiers. Furthermore, the polymerization solvents and diluents described later are not included in the additives constituting the adhesive composition P.

[0111] The adhesive composition P preferably further contains a silane coupling agent. This increases the adhesion to the substrate, making it easier to achieve the aforementioned adhesive strength.

[0112] As a silane coupling agent, an organosilicon compound that is compatible with (meth)acrylate polymer (A), has light transmittance, and contains at least one alkoxysilyl group within the molecule is preferred. This results in improved adhesion while maintaining the desired optical properties.

[0113] Examples of silane coupling agents include, for example, silicon compounds containing polymerizable unsaturated groups such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloyloxypropyltrimethoxysilane; silicon compounds with epoxy structures such as 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and silicon compounds containing mercapto groups such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane. Compounds; amino-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane; condensation products of 3-chloropropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, or at least one of these compounds with alkyl-containing silicon compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. These silane coupling agents can be used alone or in combination of two or more.

[0114] The content of silane coupling agent in the adhesive composition P is preferably 0.01 to 1 part by weight relative to 100 parts by weight of (meth)acrylate polymer (A), more preferably 0.04 to 0.7 parts by weight, particularly preferably 0.08 to 0.5 parts by weight, and even more preferably 0.12 to 0.3 parts by weight. This increases the adhesion to the adhered object, making it easier to obtain the aforementioned adhesive strength.

[0115] 2. Preparation of adhesive composition P The adhesive composition P can be prepared by preparing a (meth)acrylate polymer (A), mixing the obtained (meth)acrylate polymer (A), a crosslinking agent (B), and an active energy ray curable component (C), and adding additives as needed.

[0116] (Meth)acrylate polymer (A) can be prepared by polymerizing a mixture of monomers constituting the polymer using conventional free radical polymerization. The polymerization of (meth)acrylate polymer (A) is preferably carried out using a polymerization initiator and via solution polymerization, depending on the desired method. However, the invention is not limited thereto, and polymerization can also be carried out under solvent-free conditions.

[0117] Examples of polymerization solvents include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone; two or more can be used simultaneously. Examples of polymerization initiators include azo compounds and organic peroxides; two or more can also be used simultaneously. Furthermore, in the above polymerization process, the weight-average molecular weight of the obtained polymer can be adjusted by incorporating chain transfer agents such as 2-mercaptoethanol.

[0118] After obtaining (meth)acrylate polymer (A), a crosslinking agent (B), an active energy ray curable component (C), and additives and succinate solvent as needed are added to a solution of (meth)acrylate polymer (A) and thoroughly mixed to obtain a solvent-diluted adhesive composition P (coating solution).

[0119] In addition, for any of the above components, if precipitation occurs when using a solid substance or when mixing with other components in an undiluted state, the component can be dissolved or diluted separately in a diluent before mixing with other components.

[0120] As diluents for the above-mentioned purposes, aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as dichloromethane and dichloroethane; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosol solvents such as ethyl cellosol.

[0121] The concentration and viscosity of the coating solution prepared by the above method are not particularly limited as long as they are within the range suitable for coating and can be appropriately selected according to the situation. For example, the adhesive composition P can be diluted to a concentration of 10-60% by mass. Furthermore, the addition of a diluent is not necessary when obtaining the coating solution; as long as the adhesive composition P has a viscosity suitable for coating, a diluent may not be added. In this case, the adhesive composition P is a coating solution in which the polymerization solvent of (meth)acrylate polymer (A) is directly used as the diluent.

[0122] 3. Formation of the adhesive layer In this embodiment, the adhesive layer is preferably composed of an adhesive formed by thermally crosslinking and curing the adhesive composition P with active energy rays. This adhesive layer can preferably be formed by applying the adhesive composition P onto the desired object and then subjecting it to heat treatment, followed by curing the adhesive composition P by irradiation with active energy rays.

[0123] The heating temperature for the above-mentioned heat treatment is preferably 50~150℃, and more preferably 70~120℃. In addition, the heating time is preferably 10 seconds to 10 minutes, and more preferably 50 seconds to 2 minutes.

[0124] Among them, active energy rays refer to rays containing energy quanta within electromagnetic waves or charged particle beams; specifically, examples include ultraviolet light and electron beams. Ultraviolet light, which is particularly easy to manipulate, is especially preferred among active energy rays.

[0125] Ultraviolet (UV) irradiation can be achieved using high-pressure mercury lamps, Fusion H lamps, xenon lamps, etc. The optimal UV irradiation intensity is 10–1000 mW / cm². 2 More preferably 50~500mW / cm 2 Furthermore, the preferred light intensity is 50~10000 mJ / cm². 2 More preferably 80~5000 mJ / cm 2 The preferred value is 150~2000 mJ / cm³. 2 On the other hand, electron beam irradiation can be performed using an electron beam accelerator or the like, and the preferred irradiation dose is approximately 10 to 1000 krad.

[0126] Through heat treatment of the adhesive composition P, the (meth)acrylate polymer (A) is cross-linked by the cross-linking agent (B), thereby forming a cross-linked structure (three-dimensional network structure). Furthermore, it is believed that by irradiating the adhesive composition P with active energy rays, multiple active energy ray-curable components (C) polymerize with each other, and the polymerized active energy ray-curable components (C) become entangled in the cross-linked structure of the (meth)acrylate polymer (A).

[0127] 4. Physical properties, etc. (1) Thickness of adhesive layer The thickness of the adhesive layer in this embodiment (measured according to JIS K7130) is preferably 1~100 μm, more preferably 5~90 ​​μm, more preferably 10~80 μm, particularly preferably 20~70 μm, even more preferably 30~60 μm, and most preferably 40~55 μm. Thus, while maintaining the required adhesion, the aforementioned physical properties are easily satisfied.

[0128] (2) Total light transmittance In this embodiment, the lower limit of the total light transmittance of the adhesive layer is preferably 70% or more, more preferably 80% or more, particularly preferably 85% or more, and even more preferably 90% or more. This results in good visibility for the repeatedly bent display. On the other hand, the upper limit of the above-mentioned total light transmittance is not particularly limited, but is generally 100% or less. The total light transmittance in this specification is a value measured according to JIS K7361-1: 1997.

[0129] (3) Haze value In this embodiment, the haze value of the adhesive layer is preferably 90% or less, more preferably 60% or less, particularly preferably 30% or less, even more preferably 10% or less, and most preferably 2% or less, and especially preferably 1% or less. This results in good visibility for repeatedly bent displays. On the other hand, the lower limit of the above-mentioned haze value is not particularly limited, but is generally 0% or more. The haze value in this specification is a value measured according to JIS K7136: 2000.

[0130] 5. Specific Structure The specific structure of the adhesive sheet, as an example of this implementation scheme, is shown below. Figure 1 .

[0131] like Figure 1 As shown, in one embodiment, the adhesive sheet 1 comprises two release sheets 12a and 12b and an adhesive layer 11, which is held by the release sheets 12a and 12b in such a manner that it contacts the release surfaces of the two release sheets 12a and 12b. Furthermore, in this specification, the release surface of a release sheet refers to the surface of the release sheet that exhibits release properties, including both surfaces that have undergone release treatment and surfaces that exhibit release properties even without release treatment.

[0132] (1) Constituent elements (1-1) Adhesive layer The adhesive layer 11 is composed of the adhesive of the above-described embodiment, preferably an adhesive formed by thermally crosslinking and curing the adhesive composition P with active energy rays. Furthermore, the adhesive layer 11 can be formed as a single layer or as multiple layers stacked together.

[0133] (1-2) Peeling sheet Release tabs 12a and 12b protect the adhesive layer 11 until the adhesive sheet 1 is used, at which point it is peeled off. In the adhesive sheet 1 of this embodiment, one or both of the release tabs 12a and 12b are not necessary.

[0134] As release sheets 12a and 12b, for example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene-(meth)acrylate copolymer film, ethylene-(meth)acrylate copolymer film, polystyrene film, polycarbonate film, polyimide film, fluoropolymer film, etc. Furthermore, cross-linked films of these films can also be used. Further, laminated films of these films can also be used. Additionally, from the perspective of SDGs, materials with high biomass content, materials that can be recycled or reused, and materials that have already been recycled or reused can be used as the materials constituting the release sheets.

[0135] Preferably, the release surfaces (especially the surfaces in contact with the adhesive layer 11) of the release sheets 12a and 12b are subjected to a release treatment. Examples of release agents used in the release treatment include alkyd-based, silicone-based, fluorinated, unsaturated polyester-based, polyolefin-based, and wax-based release agents. Furthermore, it is preferable that one of the release sheets 12a and 12b is a heavy-duty release sheet with high release force, and the other is a light-duty release sheet with low release force.

[0136] The thickness of the release strips 12a and 12b is not particularly limited, but is preferably 20 to 300 μm, more preferably 30 to 150 μm.

[0137] (2) Manufacturing of adhesive sheets As a manufacturing example of adhesive sheet 1, the use of the above-described adhesive composition P will be described. A coating liquid of adhesive composition P is applied to the release surface of a release sheet 12a (or 12b), and heat treatment is performed to thermally crosslink the adhesive composition P, thereby forming a coating. Then, the release surface of another release sheet 12b (or 12a) is laminated with the coating. Next, the coating is irradiated with active energy rays through the release sheet 12a (or 12b), thereby curing the coating to form adhesive layer 11.

[0138] In another example of manufacturing the adhesive sheet 1, the coating solution of the adhesive composition P is applied to the release surface of a release sheet 12a (or 12b), and heat treatment is performed to thermally crosslink the adhesive composition P to form a coating. Then, with the coating exposed, the coating is irradiated with active energy rays to cure the coating and form an adhesive layer 11. The release sheet 12b (or 12a) is then stacked on the adhesive layer 11.

[0139] Methods for applying the coating solution of the above-mentioned adhesive composition P can include, for example, rod coating, blade coating, roller coating, squeegee coating, die coating, comma coating, gravure coating, etc. The conditions for heat treatment and irradiation with active energy rays are as described above.

[0140] [Repeatedly bent and stacked components] A repeatedly bent laminated member according to one embodiment of the present invention is shown. Figure 2 .

[0141] The repeatedly bending laminated member 2 of this embodiment is constituted by having a first bending member 21 (one bending member), a second bending member 22 (another bending member), and an adhesive layer 11 located between the first bending member 21 and the second bending member 22 to bond the two together.

[0142] The adhesive layer 11 in the aforementioned repeatedly bent laminated member 2 is composed of the aforementioned adhesive, or is the adhesive layer 11 of the aforementioned adhesive sheet 1.

[0143] The repeatedly bending laminate 2 is either the repeatedly bending device itself or a component constituting part of the repeatedly bending device. The repeatedly bending device is preferably a display capable of repeated bending (including folding), but is not limited thereto. Examples of such repeatedly bending devices include organic electroluminescent (organic EL) displays, mini-LED displays, micro-LED displays, electrophoretic displays (electronic paper), liquid crystal displays using a plastic substrate (film) as a substrate, flexible displays, foldable displays, stretchable displays, rollable displays, etc., and may also be touch panels.

[0144] The first bending member 21 and the second bending member 22 are members that can be repeatedly bent (including folded), such as coatings, blocking films, hard coatings, self-healing coatings, polarizing films (polarizing plates), polarizers, phase difference films (phase difference plates), viewing angle compensation films, brightness enhancement films, contrast enhancement films, diffusion films, semi-transparent reflective films, electrode films, transparent conductive films, metal mesh films, film sensors (touch sensing films), liquid crystal polymer films, light-emitting polymer films, film-like liquid crystal modules, organic EL modules (organic EL films, organic EL elements), electronic paper modules (film-like electronic paper), film heaters, TFT (Thin Film Transistor) substrates, etc.

[0145] The Young's modulus of the first bending member 21 and the second bending member 22 are preferably 0.1~10 GPa, particularly preferably 0.5~7 GPa, and even more preferably 1~5 GPa. This allows for easy repeated bending of each bending member.

[0146] The thicknesses of the first bending member 21 and the second bending member 22 are preferably 10 to 3000 μm, particularly preferably 25 to 1000 μm, and even more preferably 50 to 500 μm. This allows for easy repeated bending of each bending member.

[0147] As an example of manufacturing the aforementioned repeatedly bent laminated member 2, a release tab 12a of the adhesive sheet 1 is peeled off, and the adhesive layer 11 exposed by the adhesive sheet 1 is attached to one surface of the first bent member 21.

[0148] Next, another release tab 12b is peeled off from the adhesive layer 11 of the adhesive tab 1, and the exposed adhesive layer 11 of the adhesive tab 1 is bonded to the second flexible member 22. Alternatively, as another example, the bonding order of the first flexible member 21 and the second flexible member 22 may be changed.

[0149] Preferably, after fabricating the laminated body as the repeatedly bent laminated member 2 in the above manner, the end face of the laminated body is laser-cut to shape the end face, thereby producing the repeatedly bent laminated member 2. In this repeatedly bent laminated member 2, since the adhesive layer 11 described above is used, the seepage of adhesive from the laser-cut end face can be suppressed. As a result, a repeatedly bent laminated member 2 with no contamination caused by adhesive on the end face can be obtained.

[0150] Laser irradiation in laser cutting can be carried out under normal conditions. There are no particular limitations on the laser used; for example, gas lasers such as carbon dioxide (CO2) lasers, TEA-CO2 lasers, and excimer lasers can be used; liquid lasers such as organic chelate lasers, inorganic lasers, and organic pigment lasers can be used; solid-state lasers such as YAG lasers, UV-YAG lasers, YVO4 lasers, and YLF lasers can be used; semiconductor lasers such as vertical-cavity surface-emitting lasers and quantum dot lasers can also be used. Among these, gas lasers are preferred from the perspective of obtaining a large laser output for excellent machinability, with carbon dioxide (CO2) lasers or TEA-CO2 lasers being the most preferred.

[0151] The wavelength of the irradiated laser is preferably 0.1~1000μm, more preferably 0.38~100μm, particularly preferably 0.78~50μm, even more preferably 1~25μm, and most preferably 8~20μm. Furthermore, the power density of the laser is typically 1.0×10⁻⁶. 3 ~1.0×10 10 W / cm 2 Preferably 1.0×10 4 ~1.0×10 8 W / cm 2 In addition, the laser irradiation time is typically 1.0 × 10⁻⁶. -8~1 second, preferably 1.0×10 -5 ~1.0×10 -1 Second.

[0152] [Repeated bending device] The repetitive bending device of this embodiment includes the aforementioned repetitive bending laminate 2. It can be composed solely of the repetitive bending laminate 2, or it can be composed of one or more repetitive bending laminate 2 and other bending members. When laminating one repetitive bending laminate 2 with another repetitive bending laminate 2, or when laminating the repetitive bending laminate 2 with other bending members, it is preferable to laminate via the adhesive layer 11 of the aforementioned adhesive sheet 1.

[0153] Since the adhesive layer is composed of the aforementioned adhesive, the repeatedly bending device of this embodiment is not prone to lifting and peeling at the interface between the adhesive layer 11 and the adhered object (first bending member 21 and second bending member 22) even when it is repeatedly bent or placed in a long-term bending state, and has excellent bending resistance.

[0154] The embodiments described above are provided for ease of understanding of the invention and are not intended to limit the invention. Therefore, it means that the elements disclosed in the above embodiments also cover all design changes and equivalents that fall within the scope of the invention.

[0155] For example, one or both of the release tabs 12a and 12b in the adhesive sheet 1 can be omitted. Alternatively, the required flexible components can be stacked in place of the release tabs 12a and / or 12b.

[0156] Furthermore, in this specification, when "X~Y" (where X and Y are arbitrary numbers) is used, unless otherwise specified, it means "X or more and Y or less," and also includes the meaning of "preferably greater than X" or "preferably less than Y." Additionally, when "X or more" (where X is any number) is used, unless otherwise specified, it includes the meaning of "preferably greater than X," and when "Y or less" (where Y is any number) is used, unless otherwise specified, it also includes the meaning of "preferably less than Y."

[0157] Example The present invention will be further described in detail below through examples, etc., but the scope of the present invention is not limited by these examples, etc.

[0158] [Example 1] 1. Preparation of (meth)acrylate polymer (A) (Meth)acrylate polymer (A) was prepared by solution polymerization of 49 parts by weight of n-butyl acrylate, 50 parts by weight of 2-ethylhexyl acrylate, and 1 part by weight of 4-hydroxybutyl acrylate. The molecular weight of (meth)acrylate polymer (A) was determined by the following method, and the weight-average molecular weight (Mw) was 1 million.

[0159] 2. Preparation of adhesive compositions 100 parts by mass (conversion value of solid content; the same below) of the (meth)acrylate polymer (A) obtained in step 1 above, 0.14 parts by mass of the isocyanate compound (manufactured by Soken Chemical & Engineering Co., Ltd., product name "TD-75") as a crosslinking agent (B), 10 parts by mass of tricyclodecanediethanol dimethacrylate as an active energy ray curing component (C), 1 part by mass of 2,4,6-trimethylbenzoyl diphenylphosphine oxide (D1) as a photopolymerization initiator (D), and 0.2 parts by mass of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent are mixed and stirred thoroughly, and diluted with methyl ethyl ketone to obtain a coating solution of adhesive composition.

[0160] 3. Manufacturing of adhesive sheets The adhesive composition P obtained in step 2 above is coated onto the peel-treated surface of a heavy-release release sheet R1, on which one side of the polyethylene terephthalate film has been peeled using a silicone-based release agent, using a doctor blade coater. Then, a heat treatment at 90°C for 1 minute is performed to form a coating. The coated side of the resulting release sheet R1 is then bonded to the peel-treated surface of a light-release release sheet R2, on which one side of the polyethylene terephthalate film has been peeled using a silicone-based release agent.

[0161] Next, under the following conditions, the coating is irradiated with active energy rays (ultraviolet light) through the release tab R2 to cure the coating and form an adhesive layer with a thickness of 50 μm. Thus, an adhesive sheet consisting of a release tab R2 / adhesive layer (thickness: 50 μm) / release tab R1 is manufactured.

[0162] <Ultraviolet Irradiation Conditions> • Use a high-pressure mercury lamp Illuminance 200mW / cm 2 Light intensity 200 mJ / cm 2 • The UV illuminance / photometer used is the "UVPF-A1" manufactured by EYE GRAPHICS. Furthermore, the thickness of the adhesive layer was measured according to JIS K7130 using a constant pressure thickness gauge (manufactured by Teclock, product name "PG-02"). Additionally, regarding the peel force of the release tabs R1 and R2 in the obtained adhesive sheet, it was confirmed that the peel force of release tab R1 is greater than that of release tab R2.

[0163] Table 1 shows the proportions (converted to solids content) of the adhesive composition when (meth)acrylate polymer (A) is set at 100 parts by weight. Details of the abbreviations, etc., listed in Table 1 are described below.

[0164] [Photopolymerization Initiator (D)] D1: 2,4,6-Trimethylbenzoyldiphenylphosphine oxide D2: A mixture of 1-hydroxycyclohexylphenyl ketone and benzophenone in a mass ratio of 1:1. [Examples 2-4, Comparative Examples 1-3] Except for changing the amount of crosslinking agent (B), the amount of active energy ray curable component (C), and the type and amount of photopolymerization initiator (D) as shown in Table 1, the adhesive sheet was manufactured in the same manner as in Example 1.

[0165] The weight-average molecular weight (Mw) mentioned above is the weight-average molecular weight converted from polystyrene, measured using gel permeation chromatography (GPC) under the following conditions (GPC determination).

[0166] <Measurement Conditions> • GPC measuring apparatus: Manufactured by TOSOH CORPORATION, HLC-8020 • GPC column (passes through in the following order): Manufactured by TOSOH CORPORATION TSK guard column HXL-H TSK gel GMHXL (×2) TSK gel G2000HXL • Determination of solvent: tetrahydrofuran • Measurement temperature: 40℃ [Experimental Example 1] (Determination of Gel Fraction) The adhesive sheets prepared in the examples and comparative examples were cut to a size of 80mm × 80mm. The adhesive layer was wrapped in a polyester mesh (200 mesh size), and its mass was weighed using a precision balance. The mass of the mesh alone was then subtracted to calculate the mass of the adhesive itself. This mass is denoted as M1.

[0167] Subsequently, the adhesive encased in the aforementioned polyester mesh was immersed in ethyl acetate for 24 hours at room temperature (23°C). The adhesive was then removed and air-dried for 24 hours at 23°C and 50% relative humidity, followed by further drying in an oven at 80°C for 12 hours. After drying, its mass was measured using a precision balance, and the mass of the mesh alone was subtracted to calculate the mass of the adhesive itself. This mass is denoted as M2. The gel fraction (%) is expressed as (M2 / M1) × 100. The results are shown in Table 2.

[0168] [Experimental Example 2] (Determination of Creep Strain) In the laminated examples and comparative examples, the adhesive layer in the adhesive sheet was manufactured with a thickness of 500 μm and punched into a cylinder with a diameter of 8 mm, which was used as a sample.

[0169] For the above samples, according to JIS K7244-6, a viscoelasticity measuring apparatus (manufactured by Anton Paar GmbH, product name "MCR302") was used, and the strain (creep strain; 23℃→CS0, 60℃→CS1) was measured under the following conditions by torsional shear method after applying a pressure of 10 kPa for 600 seconds. The results are shown in Table 2.

[0170] Measurement frequency: 1Hz Measurement temperatures: 23℃, 60℃ Furthermore, for the above-mentioned samples (except for Example 4), according to JIS K7244-6, a viscoelasticity measuring apparatus (manufactured by Anton Paar GmbH, product name "MCR302") was used, and the torsional shear method was employed. Under the same conditions as described above, a pressure of 10 kPa was applied for 600 seconds, followed by a 600-second period at 60°C without pressure. The strain (creep strain; CS2) (%) was measured during this period. The ratio of CS2 to CS1, i.e., the recovery rate (%) ((CS2 / CS1)×100), was calculated. The results are shown in Table 2.

[0171] [Experimental Example 3] (Determination of Storage Modulus G') The adhesive layers of the adhesive sheets manufactured in the various embodiments and comparative examples were stacked to form a laminate with a thickness of 1 mm. A cylinder with a diameter of 8 mm (1 mm in height) was punched out from the obtained laminate of adhesive layers and used as a sample.

[0172] For the above samples, the storage modulus G' (MPa) (G'(-20), G'(23) and G'(40)) at various temperatures was determined using a viscoelasticity measuring apparatus (manufactured by Anton Paar GmbH, product name "MCR302") and by torsional shear method under the following conditions, in accordance with JIS K7244-6. The results are shown in Table 2.

[0173] Measurement frequency: 1Hz Measurement temperatures: -20℃, 23℃, 40℃ Furthermore, based on the measured G'(-20), G'(23) and G'(40) above, the elastic modulus change rates (RC1) to (RC3) obtained from the following equations (1) to (3) are calculated. The results are shown in Table 2.

[0174] The rate of change of elastic modulus (RC1) (%) = (G'(-20) / G'(40)) × 100 …(1) The rate of change of elastic modulus (RC2) (%) = (G'(-20) / G'(23)) × 100 …(2) Rate of change of elastic modulus (RC3) (%) = (G'(23) / G'(40)) × 100 …(3) [Experimental Example 4] (Determination of Total Light Transmittance) The adhesive layer of the adhesive sheet manufactured in the examples and comparative examples was bonded to glass and used as the test sample. Based on the background measurement using glass, the total light transmittance (%) of the above test sample was measured using a haze meter (manufactured by NIPPONDENSHOKU INDUSTRIES Co., Ltd., product name "SH-7000") in accordance with JIS K7361-1: 1997. The results are shown in Table 2.

[0175] [Experimental Example 5] (Determination of Haze Value) The adhesive layer of the adhesive sheet manufactured in the examples and comparative examples was bonded to glass and used as the test sample. Based on the background measurement using glass, the haze value (%) of the test sample was measured using a haze meter (manufactured by NIPPONDENSHOKU INDUSTRIES Co., Ltd., product name "SH-7000") in accordance with JIS K7136: 2000. The results are shown in Table 2.

[0176] [Experimental Example 6] (Determination of Adhesion) Peel off release sheet R2 from the adhesive sheet obtained in the examples and comparative examples, and attach the exposed adhesive layer to the easy-adhesive layer of a polyethylene terephthalate (PET) film (manufactured by TOYOBO CO.,LTD., product name "COSMOSHINE A4160", thickness: 100 μm) with an easy-adhesive layer, to obtain a laminate consisting of a PET film / adhesive layer / release sheet R1. Cut the obtained laminate into pieces 25 mm wide and 100 mm long, and use them as samples.

[0177] Under conditions of 23°C and 50%RH, the release tab R1 was peeled off from the above-mentioned sample. The exposed adhesive layer was then attached to soda-lime glass (manufactured by Nippon Sheet Glass Co., Ltd.). The sample was then pressurized for 20 minutes at 0.5 MPa and 50°C using an autoclave manufactured by KURIHARA SEISAKUSHO Co., Ltd. After being placed at 23°C and 50%RH for 24 hours, the adhesion (N / 25 mm) was measured using a tensile testing machine (manufactured by ORIENTEC Co., LTD, product name "TENSILON") at a peeling speed of 300 mm / min and a peeling angle of 180 degrees. Conditions not described here were measured according to JIS Z0237:2009. The results are shown in Table 2.

[0178] [Experimental Example 7] (Evaluation of Laser Cutting Machinability) The adhesive sheets manufactured in the examples and comparative examples were cut to a size of 100mm in length and 100mm in width and used as samples.

[0179] For the ends of each side of the samples obtained above, laser cutting was performed using a 30W CO2 laser system (manufactured by Universal Laser Systems, Inc., Scottsdale, Arizona, product name "VLS2.30"), removing 500μm from each end face. The laser cutting conditions are shown below.

[0180] • Mode: Vector Light · Output 5% • Speed ​​4% 150 PPI After performing the laser cutting process described above, the end faces of the samples were visually inspected to determine whether adhesive leakage had occurred, and the laser cutting processability was evaluated according to the following criteria. The results are shown in Table 2.

[0181] No adhesive seepage was observed on the end face of the sample after laser cutting.

[0182] ×… Adhesive seepage was observed on the end face of the sample after laser cutting.

[0183] [Experimental Example 8] (Evaluation of Bending Resistance) Under conditions of 23°C and 50%RH, release sheet R2 was peeled off from the adhesive sheets prepared in the examples and comparative examples, and the exposed adhesive layer was adhered to one side of a polyethylene terephthalate (PET) film (manufactured by TOYOBO CO.,LTD., product name "COSMOSHINE A4160", thickness: 100 μm). Then, release sheet R1 was peeled off, and the exposed adhesive layer was adhered to one side of another PET film (manufactured by TORAY INDUSTRIES, INC., product name "LUMIRROR #38-U48", thickness: 38 μm). Then, using an autoclave manufactured by KURIHARA SEISAKUSHO Co.,Ltd., the film was pressurized at 0.5 MPa and 50°C for 20 minutes, and then placed at 23°C and 50%RH for 24 hours. The resulting laminate, consisting of a 100 μm PET film, an adhesive layer, and a 38 μm PET film, was cut into pieces 50 mm wide and 200 mm long and used as a sample.

[0184] Using a durability testing machine (manufactured by YUASA SYSTEM Co., Ltd., product name "Paper-like Tensionless U-shaped Expansion Testing Machine (Paper-like Load-free U-shaped Expansion Tester)"), the obtained specimens were repeatedly bent under the following conditions. Furthermore, the specimens were configured to bend inwards with the PET film (38 μm) side facing inwards.

[0185] Number of bends: 100,000 Test temperature: 23℃ For the specimens after completing the above tests, the appearance of the bent portion was visually inspected, and the bending resistance (100,000 cycles) was evaluated according to the following criteria. The results are shown in Table 2.

[0186] ○…No lifting or peeling occurred in the curved section.

[0187] The curved section has experienced lifting and peeling.

[0188] Furthermore, using a durability testing machine (manufactured by YUASA SYSTEM Co., Ltd., product name "Sheet-like Tensionless U-Shaped Expansion Tester"), the obtained specimens (except for Example 4) were repeatedly bent under the following conditions. Additionally, the specimens were configured with the PET film (38 μm) side facing inwards during the test.

[0189] Number of bends: 400,000 Test temperature: 23℃ For the specimens after completing the above tests, the appearance of the bent portion was visually inspected, and the bending resistance (400,000 cycles) was evaluated according to the following criteria. The results are shown in Table 2.

[0190] Even after being bent 400,000 times, no floating or peeling occurred.

[0191] △…No floating / peeling occurred at the stage of 200,000 bending cycles, but floating / peeling occurred when the number of bending cycles reached 400,000.

[0192] ×… Lifting / peeling occurred at the stage of 100,000 bending cycles.

[0193] [Table 1] [Table 2] As shown in Table 2, the adhesive layer of the adhesive sheets in the embodiments exhibits excellent laser cutting processability and bending resistance. Furthermore, the adhesive sheets of Examples 1-3 did not experience lifting / peeling even after numerous repeated bending cycles, demonstrating excellent bending resistance.

[0194] Industrial applicability The present invention is suitable for bonding one bending member to another bending member constituting a repeatedly bending display (especially a foldable display).

Claims

1. An adhesive sheet having an adhesive layer for bonding one bending member to another bending member constituting a repeatedly bending device, characterized in that, According to the torsional shear method of JIS K7244-6, when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 23°C and a frequency of 1 Hz, the strain is 10% or more and 120% or less. The adhesive sheet has an adhesion force of 5 N / 25 mm or more to the soda-lime glass.

2. An adhesive sheet comprising an adhesive layer for bonding one bending member to another bending member constituting a repeatedly bending device, characterized in that, According to the torsional shear method of JIS K7244-6, when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 23°C and a frequency of 1Hz, the strain is less than 120%. The adhesive constituting the adhesive layer has a storage modulus G'(23) of less than 0.30 MPa at 23°C. The adhesive sheet has an adhesion force of 5 N / 25 mm or more to the soda-lime glass.

3. An adhesive sheet having an adhesive layer for bonding one bending member to another bending member constituting a repeatedly bending device, characterized in that, According to the torsional shear method of JIS K7244-6, when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 23°C and a frequency of 1Hz, the strain is less than 120%. The adhesive constituting the adhesive layer has a storage modulus G'(23) of 0.05 MPa or more and 0.25 MPa or less at 23°C.

4. An adhesive sheet having an adhesive layer for bonding one bending member to another bending member constituting a repeatedly bending device, characterized in that, According to the torsional shear method of JIS K7244-6, when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 23°C and a frequency of 1Hz, the strain is less than 120%. The adhesive constituting the adhesive layer has a storage modulus G'(-20) of less than 1.5 MPa at -20°C. The adhesive sheet has an adhesion force of 5 N / 25 mm or more to the soda-lime glass.

5. An adhesive sheet having an adhesive layer for bonding one bending member to another bending member constituting a repeatedly bending device, characterized in that, According to the torsional shear method of JIS K7244-6, when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 60°C and a frequency of 1 Hz, the strain is 18% or more and 140% or less. The adhesive sheet has an adhesion force of 5 N / 25 mm or more to the soda-lime glass.

6. An adhesive sheet having an adhesive layer for bonding one bending member to another bending member constituting a repeatedly bending device, characterized in that, According to the torsional shear method of JIS K7244-6, the strain of the adhesive layer when subjected to a pressure of 10 kPa for 600 seconds at a temperature of 60°C and a frequency of 1 Hz is greater than 18%. Based on the storage modulus G'(-20) of the adhesive constituting the adhesive layer at -20°C and the storage modulus G'(40) at 40°C, the rate of change of elastic modulus obtained by the following formula (1) is 610% or more and 10000% or less. The rate of change of elastic modulus (%) = (G'(-20) / G'(40)) × 100 …(1).

7. An adhesive sheet having an adhesive layer for bonding one bending member to another bending member constituting a repeatedly bending device, characterized in that, According to the torsional shear method of JIS K7244-6, when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 60°C and a frequency of 1 Hz, the strain is less than 140%. The adhesive constituting the adhesive layer has a storage modulus G'(-20) of less than 1.5 MPa at -20°C. The adhesive sheet has an adhesion force of 5 N / 25 mm or more to the soda-lime glass.

8. The adhesive sheet according to any one of claims 1 to 7, wherein The adhesive constituting the adhesive layer has a storage modulus G'(-20) of 0.001 MPa or more and 1.5 MPa or less at -20°C.

9. The adhesive sheet according to any one of claims 1 to 7, wherein The adhesive that constitutes the adhesive layer has a storage modulus G'(40) of 0.001 MPa or more and 1 MPa or less at 40°C.

10. The adhesive sheet according to any one of claims 1 to 7, wherein Based on the storage modulus G'(-20) of the adhesive constituting the adhesive layer at -20°C and the storage modulus G'(40) at 40°C, the rate of change of elastic modulus obtained by the following formula (1) is more than 100% and less than 10000%. The rate of change of elastic modulus (%) = (G'(-20) / G'(40)) × 100 …(1).

11. The adhesive sheet according to any one of claims 1 to 7, wherein Based on the storage modulus G'(-20) of the adhesive constituting the adhesive layer at -20°C and the storage modulus G'(23) at 23°C, the rate of change of elastic modulus obtained by the following formula (2) is more than 100% and less than 10000%. The rate of change of elastic modulus (%) = (G'(-20) / G'(23)) × 100 …(2).

12. The adhesive sheet according to any one of claims 1 to 4, wherein Based on the storage modulus G'(23) of the adhesive constituting the adhesive layer at 23°C and the storage modulus G'(40) at 40°C, the rate of change of elastic modulus obtained by the following formula (3) is 10% or more and 10000% or less. The rate of change of elastic modulus (%) = (G'(23) / G'(40)) × 100 …(3).

13. The adhesive sheet according to any one of claims 5 to 7, wherein The adhesive that constitutes the adhesive layer has a storage modulus G'(23) of 0.001 MPa or more and 1 MPa or less at 23°C.

14. The adhesive sheet according to any one of claims 5 to 7, wherein Based on the storage modulus G'(23) of the adhesive constituting the adhesive layer at 23°C and the storage modulus G'(40) at 40°C, the rate of change of elastic modulus obtained by the following formula (3) is more than 100% and less than 10000%. The rate of change of elastic modulus (%) = (G'(23) / G'(40)) × 100 …(3).

15. The adhesive sheet according to any one of claims 5 to 7, wherein The strain when the adhesive layer is subjected to a pressure of 10 kPa for 600 seconds at a temperature of 60°C and a frequency of 1 Hz according to the torsional shear method of JIS K7244-6 is defined as CS1 (%). The strain CS2 (%) is defined as the strain obtained by applying a pressure of 10 kPa to the adhesive layer for 600 seconds at a temperature of 60°C and a frequency of 1 Hz according to the torsional shear method of JIS K7244-6, followed by placing it at 60°C without pressure for 600 seconds. The ratio of CS2 to CS1, i.e., the recovery rate, is above 91%.

16. The adhesive sheet according to any one of claims 1 to 7, wherein The adhesive comprising the adhesive layer has a gel content of 40% or more and 100% or less.

17. The adhesive sheet according to any one of claims 1 to 7, wherein The adhesive that constitutes the adhesive layer is an acrylic adhesive.

18. The adhesive sheet according to any one of claims 1 to 7, wherein The adhesive constituting the adhesive layer is an adhesive formed by thermally crosslinking and curing an adhesive composition containing (meth)acrylate polymer (A), crosslinking agent (B) and active energy ray curable component (C) with active energy ray.

19. The adhesive sheet according to any one of claims 1 to 7, wherein The adhesive sheet has two release tabs. The adhesive layer is held by the release tabs in such a way that it contacts the release surfaces of the two release tabs.

20. A repeatedly bent, laminated component, characterized in that, have: A bending member constituting a repeatedly bending device and another bending member, and An adhesive layer that bonds one curved member to the other curved member. The adhesive layer is the adhesive layer of the adhesive sheet according to any one of claims 1 to 7.

21. The repeatedly bent laminated member according to claim 20, characterized in that, The end face of the repeatedly bent and stacked component is formed by laser cutting.

22. A device for repeated bending, characterized in that, It has the repeatedly bent laminated member as described in claim 20.

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