Adhesive sheet

Abstract

Provided is an adhesive sheet that is less likely to peel around a bent part even when the adhesive sheet is bonded to an adherend and bent repeatedly.　The adhesive sheet 10 is provided with an adhesive layer 1. The adhesive sheet 10 is used by being bent in at least one direction D1. The adhesive layer 1 has, within the same plane, a soft region 11 and a hard region 12 that are coplanar and adjacent to each other along a direction D2 perpendicular to the one direction D1.

Description

Adhesive Sheet

[0001] The present invention relates to an adhesive sheet.

[0002] A display panel has a laminated structure including, for example, a pixel panel, a touch panel, a polarizing plate, a cover film, and the like. In the manufacturing process of such a display panel, for example, a transparent adhesive sheet (optically adhesive sheet) is used to join the elements included in the laminated structure. On the other hand, foldable display panels that can be repeatedly bent are being developed, for example, for smartphones and tablet terminals. In a foldable display panel, each element in the laminated structure is fabricated to be repeatedly bendable, and an optically adhesive sheet is used for bonding between such elements. An optically adhesive sheet for foldable devices such as foldable display panels is described, for example, in Patent Document 1 below.

[0003] Japanese Unexamined Patent Publication No. 2018-111754

[0004] However, conventional adhesive sheets have a problem that when a device is repeatedly bent in a state where the adhesive sheet is bonded to an adherend such as the device, peeling from the adherend occurs around the bent portion.

[0005] The present invention is made to solve such a problem, and an object thereof is to provide an adhesive sheet that hardly causes peeling around a bent portion even when the adhesive sheet is bonded to an adherend and repeatedly bent.

[0006] As a result of diligent efforts to solve the above problem, the present inventors have found that a specific adhesive sheet hardly causes peeling around a bent portion even when the adhesive sheet is bonded to an adherend and repeatedly bent. The present invention has been completed based on these findings.

[0007] That is, the present invention is an adhesive sheet that includes an adhesive layer and is used by being bent in at least one direction, and the adhesive layer has a soft region and a hard region adjacent to each other along the direction perpendicular to the one direction within the same surface.

[0008] Preferably, the width W1 of the soft region and the width W2 of the hard region in the vertical direction of the adhesive sheet satisfy the following formula (1): 0.3 ≤ W1 / W2 ≤ 3 (1)

[0009] The adhesive sheet described above preferably has a maximum value A of the elastic modulus in the soft region at -20 to 100°C of 60 kPa or less.

[0010] The above adhesive sheet preferably satisfies the following equation (2) when the maximum value A and minimum value B of the elastic modulus in the soft region at -20 to 100°C: 0.1 ≤ B / A < 1 (2)

[0011] The above adhesive sheet preferably satisfies the following formula (3): 2 ≤ G(Hard) / G(Soft) ≤ 5 × 10 ３ (3)

[0012] The adhesive sheet of the present invention is less prone to peeling around the bent portion, even when repeatedly bent after being attached to a substrate.

[0013] Figure 1 shows a cross-sectional view of an adhesive sheet according to one embodiment of the present invention. Figure 2 shows a cross-sectional view according to one embodiment of a state in which the adhesive sheets shown in Figure 1 are laminated so as to span two adherends. Figure 3 shows a simplified plan view of the laminate shown in Figure 2. Figure 4 shows a simplified cross-sectional view of the laminate shown in Figure 2 in a folded state.

[0014] [Adhesive Sheet] In this specification, "adhesion" refers to the property of two surfaces adhering tightly to each other based on cohesive forces derived from the chemical structure of the composition in response to external pressure (e.g., minute pressure), and being able to be peeled off if necessary. In contrast, "bonding" refers to the property of two surfaces being firmly joined together by a chemical reaction (hardening) of the composition, which produces a hardened product and is not intended to be peeled off.

[0015] Furthermore, in this specification, the form of the "adhesive" is not particularly limited and may be liquid at room temperature (for example, a fluid solid (paste), an adhesive composition, etc.), or a solid at room temperature. Also, the form of the "adhesive" is not particularly limited and may be in the form of a sheet. In this specification, the "adhesive layer" is a non-fluid sheet-like (layered) adhesive layer.

[0016] The adhesive sheet of the present invention comprises at least an adhesive layer in which a soft region and a hard region are adjacent to each other on the same surface. The hard region is a region that is harder than the soft region. That is, the soft region is a region that is softer than the hard region. In this specification, the adhesive layer may be referred to as "the adhesive layer of the present invention."

[0017] The adhesive sheet of the present invention may be a so-called "substrate-less type" adhesive sheet that does not have a base material (substrate layer), or it may be an adhesive sheet that has a base material. In this specification, a "substrate-less type" adhesive sheet may be referred to as a "substrate-less adhesive sheet," and an adhesive sheet that has a base material may be referred to as a "substrate-attached adhesive sheet." Examples of the above-mentioned substrate-less adhesive sheet include a double-sided adhesive sheet consisting only of the adhesive layer of the present invention, and a double-sided adhesive sheet consisting of the adhesive layer of the present invention and other adhesive layers (adhesive layers other than the adhesive layer of the present invention). Examples of the above-mentioned substrate-attached adhesive sheet include a single-sided adhesive sheet having the adhesive layer of the present invention on one side of the base material, a double-sided adhesive sheet having the adhesive layer of the present invention on both sides of the base material, and a double-sided adhesive sheet having the adhesive layer of the present invention on one side of the base material and other adhesive layers on the other side. The above-mentioned "substrate (substrate layer)" refers to the support, and is the part that is attached to the adherend together with the adhesive layer when the adhesive sheet of the present invention is used (attached) to an adherend. The release liner that is peeled off when the adhesive sheet is used (applied) is not included in the above-mentioned substrate.

[0018] The adhesive sheet of the present invention will be described below with reference to the drawings. However, the adhesive sheet of the present invention is not limited to the embodiments shown in each drawing.

[0019] Figure 1 is a cross-sectional view showing an adhesive sheet according to one embodiment of the present invention. The adhesive sheet 10 shown in Figure 1 is a substrate-less adhesive sheet consisting of an adhesive layer 1. The adhesive layer 1 is sandwiched between the release surfaces of the release liners 21 and 22. The adhesive layer 1 has adjacent soft regions 11 and hard regions 12 on the same plane. Specifically, the adhesive layer 1 has three soft regions 11 (11a to 11c) and three hard regions 12 (12a to 12c) on the same plane, with soft region 11a, hard region 12a, soft region 11b, hard region 12b, soft region 11c, and hard region 12c being adjacent to each other in this order along one direction D2. That is, rectangular soft regions 11 and hard regions 12 are alternately located on the same plane. In the adhesive layer 1, the soft region 11 and the hard region 12 are formed from one end to the other in a direction perpendicular to one direction D2 (specifically, D1 in Figure 3). The hard regions 12a to 12c are harder than the soft regions 11a to 11c. In Figure 1, the boundaries between the soft region 11 and the hard region 12 are drawn with solid lines, but these boundaries do not actually need to be observed visually.

[0020] The adhesive sheet of the present invention is used by laminating it on the same side so as to span two adherends with a separation region between them. Figure 2 shows a cross-sectional view of one embodiment in which the adhesive sheet shown in Figure 1 is laminated on the same side so as to span the two adherends. The adhesive sheet 10 is arranged so as to be laminated in the following order: cover member 2, adhesive sheet 10, glass plate 3, adhesive sheet 4, and optical member 5. The adhesive sheet 10 is interposed between the cover member 2 and the glass plate 3, bonding them together. The adhesive sheet 4 is interposed between the optical member 5 and the glass plate 3, bonding them together. The adhesive sheet 10 is the adhesive sheet of the present invention, and the adhesive sheet 4 may be the adhesive sheet of the present invention, or an adhesive sheet other than the adhesive sheet of the present invention (another adhesive sheet). Alternatively, the adhesive sheet 10 may be the other adhesive sheet and the adhesive sheet 4 may be the adhesive sheet of the present invention.

[0021] The optical laminate 13, formed by directly stacking a cover member 2, an adhesive sheet 10, a glass plate 3, an adhesive sheet 4, and an optical member 5 in this order, is used by adhering it to two adherends 6 and 7, which are arranged with a separation region R on the same side (i.e., the same side of the adhesive sheet 10), via adhesive sheets 8 and 9. The two adherends 6 and 7 are used by bending them, for example, at or near a bend in the separation region R.

[0022] The adhesive sheet of the present invention is used by bending in at least one direction. That is, the adhesive sheet of the present invention is used by folding or unfolding in at least one direction. Figure 3 shows a simplified plan view of the laminate shown in Figure 2. In Figure 3, the cover member 2 in the optical laminate 13 and the adhesive sheets 8 and 9 provided on the adherends 6 and 7 are omitted in order to make it easier to understand the relationship between the soft region 11 and the hard region 12 in the adhesive sheet 10 and the bending direction of the adhesive sheet 10. The cross-sectional view of Figure 2 corresponds to the II-II' cross-sectional view of Figure 3, except that it has the cover member 2 and the adhesive sheets 8 and 9.

[0023] As shown in Figure 3, the adhesive sheet 10 is used by bending it in at least one direction D1. The adhesive layer 1 has a soft region 11 and a hard region 12 adjacent to each other along a direction D2 perpendicular to the direction D1 within the same plane. Specifically, the adhesive layer 1 has three soft regions 11 (11a to 11c) and three hard regions 12 (12a to 12c) within the same plane, with the soft region 11a, hard region 12a, soft region 11b, hard region 12b, soft region 11c, and hard region 12c adjacent to each other along the direction D2 in this order. Each boundary between the soft region 11 and the hard region 12 is perpendicular to the opposing side surfaces of the adherends 6 and 7.

[0024] The width Y of the separation region R is appropriately selected depending on the size of the object to be attached, but is, for example, 1 to 40 mm, preferably 5 to 30 mm, and more preferably 10 to 20 mm. If the width Y is 1 mm or more, sufficient width Y can be secured, and the object to be attached can be easily folded. If the width Y is 40 mm or less, the excess soft area that extends outside the object to be attached when the object is folded can be reduced.

[0025] Figure 4 is a simplified cross-sectional view showing the laminate shown in Figure 3 bent at the bending portion V. In Figure 4, the components other than the adhesive sheet 10 in the optical laminate 13 and the adhesive sheets 8 and 9 are omitted in order to make it easier to recognize the positional relationship between the adhesive sheet 10 and the adherends 6 and 7. As shown in Figures 2 and 3, the adherends 6 and 7 are separated by a separation region R and bonded to the optical laminate 13, so when the optical laminate 13 is folded, the adherends 6 and 7 do not bend, and only the optical laminate 13 bends. When bent at the bending portion V, it takes on a teardrop shape as shown in Figure 4. When the adhesive sheet 10 is bent, the hard region 12 is difficult to deform, so the soft region 11 is forced to deform. Here, because the soft region 11 and the hard region 12 are adjacent to each other in the same plane in a direction perpendicular to the bending direction, the strain on the soft region 11 when the adhesive sheet 10 is bent is small, and peeling is less likely to occur around the bent portion V (such as the bent region or near the edges of the adherends 6 and 7) even when the adhesive sheet 10 is repeatedly bent. In addition, because the adhesive layer 1 has a soft region 11 and a hard region 12, adhesive overflow during die-cutting is less likely to occur than when it is composed of a soft region alone, resulting in excellent die-cutting processability.

[0026] In Figure 3, the soft region 11 and the hard region 12 extend in one direction D1 and are parallel to each other. Although all the soft regions 11 and hard regions 12 are parallel in Figure 3, the adhesive layer of the present invention is not limited to this shape as long as it can be bent for use.

[0027] The soft region 11 and the hard region 12 may have the same or different widths (length in one direction D2). Also, in Figures 1 to 3, the widths of all the soft regions 11a to 11c are the same, but they may be different, and the widths of all the hard regions 12a to 12c are the same, but they may be different.

[0028] Preferably, the widths W1 of adjacent soft regions and W2 of hard regions in one direction D2 satisfy the following formula (1). When the following formula (1) is satisfied, the material exhibits excellent bending resistance, and in the optical laminate formed by laminating the adhesive sheet and glass plate of the present invention, indentations are less likely to remain, and cracks are less likely to occur in the glass plate. 0.3 ≤ W1 / W2 ≤ 3 (1)

[0029] In the above formula (1), [W1 / W2] is preferably 0.5 to 2, more preferably 0.7 to 1.5.

[0030] The widths W1 of the soft region and W2 of the hard region are not particularly limited, but can be selected from, for example, within the range of 0.1 to 10 mm. The widths W1 of the soft region and W2 of the hard region are the distance from the boundary at one end of each region to the boundary at the other end. If the boundary at one end and / or the boundary at the other end is not clearly defined, the boundary is the central part between the centers of adjacent regions (for example, the central part from the point where the hardness gradient starts to the point where the gradient ends (the central part of the boundary region described later)).

[0031] In Figure 1, one end of direction D2 is a soft region 11a and the other end is a hard region 12c, but both ends may be soft regions, or both ends may be hard regions. Furthermore, the number of soft regions and hard regions in the adhesive layer of the present invention is not particularly limited; it may have one or more of each, or two or more (for example, 2 to 20). When there are two or more of each, the hardness of the multiple soft regions may be the same or different. Similarly, the hardness of the multiple hard regions may be the same or different.

[0032] The adjacent soft region 11 and hard region 12 may or may not have a clearly defined boundary. The area near the boundary between the soft region 11 and hard region 12 may be a boundary region where the hardness changes gradually. In the boundary region, there is a hardness gradient, and along one direction D2, the hardness gradually changes from the center of the soft region 11 to the center of the adjacent hard region 12. Therefore, the boundary region is the area from the point where the hardness gradient begins to the point where the gradient ends. When the boundary region is present, the hardness of the soft region 11 and hard region 12 are the physical properties of the parts outside the boundary region, respectively.

[0033] The shape of the boundary between the soft region 11 and the hard region 12 is linear in Figures 1 to 3, but it is not particularly limited as long as the adhesive sheet 10 can be bent, and it may be a wavy line or the like. The adhesive layer 1 is symmetrical in one direction D1. For example, in Figures 1 to 3, the soft region 11 and the hard region 12 are positioned in the adhesive layer 1 so as to be symmetrical with respect to the bending portion V.

[0034] The maximum value A of the elastic modulus of the soft region in the range of -20 to 100°C is preferably 60 kPa or less, more preferably 55 kPa or less, and even more preferably 50 kPa or less. When the maximum value A is 60 kPa or less, the soft region has appropriate flexibility in a wide range of temperature environments, and the adherend can be easily folded. The lower the maximum value A, the more flexible it is, but from the viewpoint of excellent handling, it is preferably 10 kPa or more, more preferably 20 kPa or more, and even more preferably 30 kPa or more. Examples of the elastic modulus include the storage modulus and the loss modulus.

[0035] The minimum value B of the elastic modulus of the soft region in the range of -20 to 100°C is preferably 30 kPa or less, more preferably 20 kPa or less, and even more preferably 15 kPa or less. When the minimum value B is 30 kPa or less, the soft region has appropriate flexibility under a wide temperature range. A lower minimum value B indicates greater flexibility, but from the viewpoint of excellent handling, it is preferably 1 kPa or more, more preferably 3 kPa or more, and even more preferably 5 kPa or more. Examples of the elastic modulus include the storage modulus and the loss modulus.

[0036] Preferably, the above maximum value A and minimum value B satisfy the following equation (2). When the following equation (2) is satisfied, the difference between the maximum value A and minimum value B is small, and the soft region has appropriate flexibility under a wide temperature environment. 0.1 ≤ B / A < 1 (2)

[0037] In formula (2) above, [B / A] is preferably 0.1 to 0.8, more preferably 0.15 to 0.5.

[0038] The modulus of elasticity G (Hard) at room temperature (23±2°C) in the hard region and the modulus of elasticity G (Soft) at room temperature (23±2°C) in the soft region preferably satisfy the following formula (3). When the following formula (3) is satisfied, the difference between the hard region and the soft region is sufficiently large and appropriate, making peeling around the bent portion less likely. Examples of the above modulus of elasticity include the storage modulus and the loss modulus. 2 ≤ G (Hard) / G (Soft) ≤ 5 × 10 ３ (3)

[0039] In formula (3) above, [G (Hard) / G (Soft)] is preferably 5 or more, and more preferably 10 or more. Also, in formula (3) above, [G (Hard) / G (Soft)] is 1 × 10 ３ The following is preferred, and more preferably 1 × 10 ２ The following are possible values: 90 or less, 80 or less, 70 or less, 60 or less, 50 or less, 40 or less, 30 or less, 20 or less, or 10 or less.

[0040] The above G (Hard) is preferably 80 kPa or more, more preferably 90 kPa or more, and still more preferably 140 kPa or more. The above G (Hard) is preferably 1000 kPa or less, more preferably 500 kPa or less, and still more preferably 300 kPa or less.

[0041] The above G (Soft) is preferably 70 kPa or less, more preferably 60 kPa or less, still more preferably 50 kPa or less, and particularly preferably 30 kPa or less. The above G (Soft) is preferably 1 kPa or more, more preferably 5 kPa or more, and still more preferably 10 kPa or more.

[0042] The storage elastic modulus of each region in the pressure-sensitive adhesive layer is a value measured by dynamic viscoelasticity. The storage elastic modulus can be controlled by the type and monomer composition of the base polymer of the pressure-sensitive adhesive constituting each region in the pressure-sensitive adhesive layer, the weight average molecular weight, the amount (addition amount) of the crosslinking agent used, the type and content of other additives, and the like. Specifically, the above elastic modulus (storage elastic modulus) can be measured by the following measurement method.

[0043] <Method for Measuring Elastic Modulus> A plurality of pressure-sensitive adhesive layer pieces cut out from the region to be measured are bonded together to prepare a pressure-sensitive adhesive sheet with a thickness of about 2 mm, and the sheet is then punched out to obtain a cylindrical pellet (diameter 9 mm) as a measurement sample. Then, the measurement sample is fixed to a parallel plate jig with a diameter of 8 mm, and then dynamic viscoelasticity measurement is performed. In this measurement, the deformation mode is set to torsion, the measurement temperature range is set to -70°C to 150°C, the temperature rising rate is set to 5°C / min, and the frequency is set to 1 Hz. Then, the storage elastic modulus in the range of -20°C to 100°C including room temperature is read from the measurement result. The dynamic viscoelasticity measurement can be carried out by a conventional method using a commercially available dynamic viscoelasticity measuring apparatus, for example, using "Advanced Rheometric Expansion System (ARES)" manufactured by TA Instruments or an equivalent product thereof.

[0044] The peel adhesive strength F (Hard) of the hard region at room temperature (23±2°C) is preferably more than 3 N / 10 mm, more preferably 3.5 N / 10 mm or more, further preferably 4 N / 10 mm or more, and particularly preferably 4.5 N / 10 mm or more. When the peel adhesive strength F (Hard) is more than 3 N / 10 mm, the adhesiveness in the hard region is excellent, and peeling is less likely to occur. The peel adhesive strength F (Hard) is preferably as high as possible for excellent adhesiveness, and is, for example, 20 N / 10 mm or less.

[0045] The peel adhesive strength F (Soft) of the soft region at room temperature (23±2°C) is preferably more than 3 N / 10 mm, more preferably 3.5 N / 10 mm or more, further preferably 4 N / 10 mm or more, and particularly preferably 4.5 N / 10 mm or more. When the peel adhesive strength F (Soft) is more than 3 N / 10 mm, the adhesiveness in the soft region is excellent, and peeling is less likely to occur. The peel adhesive strength F (Soft) is preferably as high as possible for excellent adhesiveness, and is, for example, 20 N / 10 mm or less.

[0046] The peel adhesive strength F (Hard) and the peel adhesive strength F (Soft) preferably satisfy the following formula (4). While the hard region typically has a lower peel adhesive strength than the soft region, when the following formula (4) is satisfied, the difference between the hard region and the soft region is small, and peeling is less likely to occur near the boundary between the soft region and the hard region. 0.9≦F (Hard) / F (Soft)≦1.1 (4)

[0047] [F (Hard) / F (Soft)] in the above formula (4) is preferably 0.95 to 1.05.

[0048] The adjacent soft region 11 and hard region 12 preferably have close optical properties. When the optical properties are close, the boundary between the hard region and the soft region is difficult to visually recognize, and the appearance when the pressure-sensitive adhesive sheet of the present invention is attached to an optical member for use becomes favorable. The optical properties of the plurality of soft regions may be the same or different. Further, the optical properties of the plurality of hard regions may be the same or different.

[0049] The optical properties mentioned above include transparency, visible light transmittance, total light transmittance, haze value, and refractive index.

[0050] Preferably, the absolute value of the difference between the refractive index (Soft) of the soft region at a wavelength of 594 nm and the refractive index (Hard) of the hard region adjacent to the soft region at a wavelength of 594 nm satisfies the following equation (5). When the following equation (5) is satisfied, the boundary between the hard region and the soft region becomes difficult to see, resulting in a good appearance when the adhesive sheet of the present invention is used by being bonded to an optical component. |Refractive index (Soft) - Refractive index (Hard)| ≤ 0.1 (5)

[0051] In the above formula (5), |refractive index (Soft) - refractive index (Hard)| is preferably 0.07 or less, more preferably 0.05 or less, and even more preferably 0.03 or less.

[0052] The refractive index (Soft) and refractive index (Hard) are not particularly limited, but can be selected from, for example, within the range of 1.1 to 1.9.

[0053] In this specification, the refractive index of an adhesive sheet refers to the refractive index of the surface of the adhesive sheet. The refractive index of an adhesive sheet can be measured using a prism coupler under the conditions of a measurement temperature of 25°C and a measurement wavelength of 594 nm. For adhesive sheets with a thickness of less than 20 μm, measurement using the light propagation mode is generally suitable. For adhesive sheets with a thickness of 20 μm or more, measurement using the critical angle mode is generally suitable. A commercially available measuring device can be used as the prism coupler; for example, the "Model 2010 / M prism coupler" or an equivalent from Metricon can be used.

[0054] Preferably, the absolute difference between the transmittance (Soft) (total light transmittance) [%] of the soft region and the transmittance (Hard) (total light transmittance) [%] of the hard region adjacent to the soft region satisfies the following formula (6). When the following formula (6) is satisfied, the boundary between the hard region and the soft region becomes difficult to see, resulting in a good appearance when the adhesive sheet of the present invention is used by being bonded to an optical component. |Transmittance (Soft) - Transmittance (Hard)| ≤ 5 (6)

[0055] In the above formula (6), |transmittance (Soft) - transmittance (Hard)| is preferably 3 or less, more preferably 1 or less, and even more preferably 0.5 or less.

[0056] The transmittance (Soft) and transmittance (Hard) are not particularly limited, but can be selected from the range of 1 to 100, respectively. The total light transmittance mentioned above is a value measured in accordance with JIS K7361-1.

[0057] Preferably, the absolute value of the difference between the haze (Soft) [%] of the soft region and the haze (Hard) [%] of the hard region adjacent to the soft region satisfies the following formula (7). When the following formula (7) is satisfied, the boundary between the hard region and the soft region becomes difficult to see, resulting in a good appearance when the adhesive sheet of the present invention is used by laminating it to an optical component. |Haze (Soft) - Haze (Hard)| ≤ 0.5 (7)

[0058] In the above formula (7), |Hayes (Soft) - Hayes (Hard)| is preferably 0.3 or less, more preferably 0.2 or less, and even more preferably 0.1 or less.

[0059] Haze (Soft) and Haze (Hard) are not particularly limited, but can be selected from a range of, for example, 99% or less (e.g., 0-99%). The above "haze" refers to the ratio of diffusely transmitted light to total transmitted light when visible light is irradiated onto the object to be measured, and is also called the haze value. Haze can be expressed by the following formula: Th (%) = Td / Tt × 100 In the above formula, Th is haze (%), Td is the scattered light transmittance, and Tt is the total light transmittance. The above haze value can be adjusted, for example, by selecting the composition and thickness of the adhesive layer.

[0060] In addition, if it is difficult to cut out an adhesive layer of a predetermined size from the area to be measured when measuring the various physical properties described herein, an adhesive layer with the same composition as the area to be measured may be prepared, and an adhesive layer of the predetermined size may be cut out from that adhesive layer to prepare a measurement sample.

[0061] Soft and hard regions, which have different elastic moduli and similar characteristics in one or more of the group consisting of refractive index, transmittance, and haze, can be prepared by making the types of base polymers and constituent monomers and their amounts similar for each region, and by creating differences in the degree of polymer crosslinking within each region, for example, by making differences in the type and amount of crosslinking agent used.

[0062] (Method for manufacturing the adhesive layer) The adhesive layer having the soft region and the hard region can be manufactured by known or conventional methods. Examples of methods for manufacturing the adhesive layer include the first to fourth methods. The first to fourth methods may be used individually or in combination of two or more.

[0063] The first method involves using adhesive compositions with different compositions for forming the soft region and the hard region. Examples of differing adhesive compositions include those that differ in the type of base polymer of the adhesive constituting the adhesive layer, the monomer composition of the base polymer, the weight-average molecular weight of the base polymer, the type of crosslinking agent, the amount of crosslinking agent used (amount added), and the type and content of other additives. For example, if the amount of crosslinking agent used is different, the region using a larger amount of crosslinking agent will be a relatively hard region, and the region using a smaller amount of crosslinking agent will be a relatively soft region.

[0064] Examples of base polymers constituting the soft and hard regions include known and conventional polymers, such as acrylic polymers, urethane acrylate resins, urethane resins, rubber resins, epoxy resins, epoxy acrylate resins, oxetane resins, silicone resins, silicone acrylic resins, polyester resins, polyether resins (such as polyvinyl ether), polyamide resins, fluororesins, vinyl acetate / vinyl chloride copolymers, and polyolefins.

[0065] Examples of the above-mentioned crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, amine-based crosslinking agents, silicone-based crosslinking agents, silane-based crosslinking agents, and polyfunctional monomers such as polyfunctional (meth)acrylates. In this specification, the above-mentioned "crosslinking agent" refers to a compound that can form crosslinks in a resin, and may be referred to as a "curing agent."

[0066] Examples of the above-mentioned other additives include crosslinking accelerators, tackifying resins (rosin derivatives, polyterpene resins, petroleum resins, oil-soluble phenols, etc.), oligomers, antioxidants, fillers (metal powders, organic fillers, inorganic fillers, etc.), antioxidants, plasticizers, softeners, surfactants, antistatic agents, surface lubricants, leveling agents, light stabilizers, UV absorbers, polymerization inhibitors, granular materials, foil-like materials, and release modifiers.

[0067] In the first method, for example, an adhesive composition that forms a soft region and an adhesive composition that forms a hard region are first applied to the release surface or substrate of the same release liner, respectively. The application of the adhesive composition that forms the soft region and the adhesive composition that forms the hard region may be done simultaneously or sequentially. After applying the adhesive composition to the release surface or substrate of the release liner to form an adhesive composition layer, the adhesive composition layer is solidified by volatilization and removal of the solvent by heating or polymerization by irradiation with active energy rays to form an adhesive layer, thereby creating an adhesive layer having a soft region and a hard region. In addition, heating, drying, etc. may be performed in addition to the irradiation with active energy rays as needed.

[0068] The second method involves using the same adhesive composition for both the soft region and the hard region, adding a modifier in such a way that the proportions differ between the soft and hard regions, and then forming an adhesive layer. In this case, an active energy ray polymerizable adhesive composition can be used as the adhesive composition.

[0069] In the second method, for example, first, an adhesive composition for forming an adhesive layer is applied to the release surface of the release liner or the substrate. After applying the adhesive composition to the release surface of the release liner or the substrate to form an adhesive composition layer, a modifier is added to the areas to be designated as soft regions and / or hard regions. The addition can be done by application. The modifier may be added to only one of the areas to be designated as soft regions and / or hard regions, or it may be added to both. If it is added to both, the amounts added should be different. The modifier to be added may be the modifier itself, or it may be a solution or dispersion in which it is dissolved and dispersed in a solvent.

[0070] The above-mentioned modifiers can be used without particular limitations, and those added in the field of adhesives can be used. Examples include polymerization initiators, crosslinking agents, ultraviolet absorbers, rust inhibitors, antistatic agents, crosslinking accelerators, silane coupling agents, tackifying resins, anti-aging agents, colorants such as dyes, antioxidants, chain transfer agents, plasticizers, softeners, surfactants, and fillers. Regions with a large amount of crosslinking agent will have a high crosslinking density of the base polymer when the adhesive layer is formed, resulting in a relatively hard region. Regions with a large amount of plasticizer will result in a relatively soft region. After adding the modifiers, the adhesive composition layer can be solidified by volatilization and removal of the solvent by heating or polymerization by irradiation with active energy rays to form an adhesive layer, thereby creating an adhesive layer having both soft and hard regions.

[0071] A third method involves using the same adhesive composition for both the soft region and the hard region, but with different degrees of polymerization. In this case, an active energy ray polymerizable adhesive composition can be used as the adhesive composition.

[0072] In the third method, for example, first, an adhesive composition for forming the adhesive layer is applied to the release surface of the release liner or the substrate. After applying the adhesive composition to the release surface of the release liner or the substrate to form the adhesive composition layer, a photomask is placed over a portion of the layer, and the adhesive composition layer is irradiated with active energy rays. In addition, heating, drying, etc. may be performed as needed in addition to the irradiation with active energy rays. In this way, the adhesive layer is formed by solidifying the adhesive composition layer through polymerization by irradiation with active energy rays. In the area covered by the photomask, the active energy rays are not irradiated, or the amount of active energy rays irradiated is small, and the degree of polymerization in that area is relatively small. On the other hand, in the area not covered by the photomask, the amount of active energy rays irradiated is large, and the degree of polymerization in that area is relatively large. The two areas formed in this way have different physical properties such as hardness, and can be a soft area and a hard area.

[0073] In the third method, a photomask having regions with different transmittances of active energy rays may be placed over the entire surface of the adhesive composition layer and irradiated with active energy rays. In this way, an adhesive layer having soft and hard regions with different amounts of active energy irradiated can be produced.

[0074] The fourth method involves forming an adhesive layer using the same adhesive composition for both the soft region and the hard region, and then impregnating the adhesive layer with the modifier such that the amounts of the modifier differ in the soft region and the hard region. In this case, an active energy ray polymerizable adhesive composition can be used as the adhesive composition.

[0075] In the fourth method, for example, first, an adhesive composition for forming the adhesive layer is applied to the release surface of the release liner or the substrate. After applying the adhesive composition to the release surface of the release liner or the substrate to form the adhesive composition layer, the adhesive layer is solidified by volatilization and removal of the solvent by heating or polymerization by irradiation with active energy rays. Subsequently, a modifier is impregnated into the areas to be designated as soft regions and / or hard regions. In this way, an adhesive layer having soft regions and hard regions can be produced.

[0076] Impregnation can be carried out by coating. The modifier may be impregnated into only one of the areas to be treated as a soft region and the area to be treated as a hard region, or it may be impregnated into both. If both are impregnated, the amount of modifier added should be different. The modifier to be impregnated may be the modifier itself, or it may be a solution or dispersion obtained by dissolving and dispersing it in a solvent.

[0077] (Substrate) When the adhesive sheet of the present invention is an adhesive sheet with a substrate, the substrate is not particularly limited, but examples include plastic films, anti-reflective (AR) films, anti-glare (AG) films, polarizing plates, and various optical films such as phase difference plates. Other examples of substrates include porous materials such as paper, cloth, and nonwoven fabrics, nets, foamed sheets, and metal foils. Examples of materials such as plastic films include polyester resins such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetylcellulose (TAC), polysulfone, polyarylate, polyimide, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymer, and cyclic olefin polymers such as the trade name "Arton" (cyclic olefin polymer, manufactured by JSR Corporation) and the trade name "Zeonor" (cyclic olefin polymer, manufactured by Nippon Zeon Co., Ltd.). Note that one or more of these plastic materials may be used.

[0078] The surface of the substrate on the side with the adhesive layer may be subjected to surface treatments such as physical treatments like corona discharge treatment, plasma treatment, sandblasting, ozone exposure treatment, flame exposure treatment, high-voltage electric shock exposure treatment, or ionization radiation treatment; chemical treatments like chromic acid treatment; or surface treatments such as easy adhesion treatment with a coating agent (primer) in order to improve adhesion and retention with the adhesive layer. It is preferable that the surface treatment to improve adhesion is applied to the entire surface of the substrate on the side with the adhesive layer.

[0079] The above-mentioned substrate may be a noise-reducing film. The noise-reducing film is not particularly limited as long as it has noise-reducing performance, but examples include a film substrate on which a noise-reducing layer is formed on at least one side. The noise-reducing layer may be a single layer or a multi-layer, and is not particularly limited as long as it has the function of reducing electromagnetic noise, but from the viewpoint of transparency, a transparent conductive layer is preferred. As the transparent conductive layer, a thin film layer formed of a conductive organic or inorganic material, or a conductive layer formed by partial contact of conductive organic or inorganic materials can be used.

[0080] The thickness of the above-mentioned substrate is not particularly limited, but is preferably 10 to 150 μm, more preferably 15 to 125 μm, and even more preferably 25 to 100 μm. The above-mentioned substrate may be in the form of a single layer or multiple layers.

[0081] The above-mentioned adhesive sheet may have a release liner on the surface (adhesive surface or bonding surface) of the adhesive layer, etc., until use. If the above-mentioned adhesive sheet is a double-sided adhesive sheet, each adhesive surface may be protected by two release liners, or it may be protected in a roll-like form (winding body) by a single release liner with both sides being release surfaces. The release liner is used as a protective material for the adhesive layer and is peeled off when it is attached to the object. Furthermore, if the above-mentioned adhesive sheet is a substrate-less adhesive sheet, the release liner also plays the role of a support for the adhesive layer. Note that the release liner is not necessarily required.

[0082] Examples of the configuration of the adhesive sheet described above include the configuration of the adhesive sheet 10 shown in Figure 1 [release liner / adhesive layer / release liner], [adhesive layer / release liner], [substrate / adhesive layer / release liner], [release liner / adhesive layer / substrate / adhesive layer / release liner], and [substrate / adhesive layer / substrate / adhesive layer / release liner]. In the configuration comprising two adhesive layers, at least one adhesive layer is the adhesive layer of the present invention, but from the viewpoint of the adhesive sheet being flexible, it is preferable that both are the adhesive layers of the present invention. Furthermore, the arrangement shapes of the soft region and the hard region in the two adhesive layers of the present invention may be the same or different.

[0083] The adhesive sheet of the present invention is not particularly limited in its use and can be used for any purpose. The adhesive sheet of the present invention can be used, for example, in optical applications, i.e., for bonding to optical components. The adhesive sheet of the present invention is used, for example, in optical components of electrical and electronic equipment when attaching (mounting) various components or parts to a predetermined part (e.g., a housing). Note that "electrical and electronic equipment" refers to equipment that falls under at least one of electrical equipment or electronic equipment. Examples of the above electrical and electronic equipment include image display devices such as liquid crystal displays, electroluminescent displays, and plasma displays, and portable electronic devices. Examples of the above image display devices include image display devices in portable electronic devices, and displays (roll displays) inside and outside vehicles such as trains and buses.

[0084] Examples of the above-mentioned portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (e.g., wristwear-type devices worn on the wrist like watches, modular devices attached to a part of the body with clips or straps, eyewear-type devices including glasses (monocular and binocular types, including head-mounted types), clothing-type devices attached to shirts, socks, hats, etc. as accessories, earwear-type devices attached to the ears like earphones, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game consoles, electronic dictionaries, electronic organizers, e-books, in-car information systems, portable radios, portable televisions, portable printers, portable scanners, and portable modems. In this specification, "portable" means not merely being able to carry something, but having a level of portability that allows an individual (a typical adult) to carry it relatively easily.

[0085] The above-mentioned adhesive sheet is preferably used, for example, for bonding components and modules that make up portable electronic devices to each other, or for fixing components and modules that make up portable electronic devices to the casing. More specifically, examples include bonding cover glass or lenses (especially glass lenses) to touch panels or touch sensor films (especially touch sensor films having metal wiring such as metal mesh films or silver nanowire films), bonding polarizing films to touch panels or touch sensors, bonding display panels to touch panels or touch sensor films, fixing cover glass or lenses (especially glass lenses) to the casing, fixing display panels to the casing, fixing input devices such as sheet keyboards and touch panels to the casing, bonding protective panels of information display sections to the casing, bonding casings to each other, bonding casings to decorative sheets, and fixing or bonding various components and modules that make up portable electronic devices. In this specification, a display panel refers to a structure that is at least composed of a lens (especially a glass lens) and a touch panel. Furthermore, in this specification, a lens is a concept that includes both transparent materials that exhibit light refraction and transparent materials that do not exhibit light refraction. In other words, the term "lens" in this specification also includes simple window panels that do not have a refractive effect.

[0086] Furthermore, the adhesive sheet can be suitably used with transparent conductive films (metal mesh films, silver nanowire films) in which the metal wiring is metal mesh wiring or silver nanowires, and in particular with optical components (touch sensor films) having a metal mesh film. When optical components having metal wiring such as metal mesh films or silver nanowire films are bonded together via the adhesive sheet, the low dielectric constant suppresses noise generation while providing sufficient adhesive strength and excellent resistance to drop impacts.

[0087] The adhesive sheet of the present invention is less prone to peeling around the bent portion even when repeatedly bent after being adhered to an object. Therefore, the adhesive sheet of the present invention is preferably used for bonding components (especially between components) in electrical and electronic equipment that is used in a bent manner, such as a bendable object, such as a bendable image display device (flexible display) (especially a foldable image display device (foldable display)).

[0088] [Optical Laminate] A laminate comprising the adhesive sheet and optical member of the present invention, such as optical laminate 13, may be referred to as "the optical laminate of the present invention." The optical laminate of the present invention preferably comprises a cover member, an adhesive sheet (A), a glass plate, an adhesive sheet (B), and an optical member in this order. In the optical laminate of the present invention, the cover member side is preferably the viewing side when laminated on, for example, an image display device. In the optical laminate of the present invention, at least one of the adhesive sheets is the adhesive sheet of the present invention, and both may be the adhesive sheets of the present invention. From the viewpoint of superior scratch resistance of the optical member, it is preferable that adhesive sheet (A) is the adhesive sheet of the present invention.

[0089] The optical laminate 13 shown in Figure 2 is one embodiment of the optical laminate of the present invention. In the optical laminate 13, the cover member 2 functions as an element for protecting other optical components (for example, touch sensors and image display devices) in the optical laminate 13.

[0090] Examples of the cover member include a cover glass and a plastic cover. The cover member may be bonded to the glass plate 3 via an adhesive sheet 10 or other adhesive sheets, as shown in Figure 2. Examples of plastics that make up the plastic cover include polyester resins such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetylcellulose (TAC), polysulfone, polyarylate, polyimide, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, and ethylene-propylene copolymer. Only one type of plastic material may be used, or two or more types may be used.

[0091] From the viewpoint of being thin yet strong and being able to be bent, the glass plate 3 is preferably made of a type of glass other than alkali glass, such as alkali-free glass. The thickness of the glass plate 3 is preferably 30 to 70 μm, and more preferably 30 to 50 μm, from the viewpoint of being able to be bent.

[0092] The thickness of the adhesive sheet (A) and the adhesive sheet (B) described above is preferably 25 to 100 μm, and more preferably 25 to 50 μm, from the viewpoint of providing excellent stress relief when subjected to impact, minimizing the likelihood of indentations remaining on the optical laminate, and minimizing the likelihood of cracks occurring in the glass plate.

[0093] In the optical laminate 13, the optical member 5 has a film on the surface facing the adhesive sheet 4. Examples of the film include various optical films such as plastic films, anti-reflective (AR) films, anti-glare (AG) films, polarizing plates, and phase difference plates. Examples of materials such as the plastic film include those described and illustrated as plastics that can constitute the cover member 2. In addition to the above-mentioned film, the optical member 5 may include one or more selected from the group consisting of a touch sensor, a noise reduction layer, and an image display device.

[0094] Examples of the above-mentioned image display devices include liquid crystal displays, organic / inorganic electroluminescent displays, and plasma displays. Examples of the above-mentioned image display devices include image display devices in portable electronic devices, in-vehicle displays, and digital signage (electronic billboards and electronic display boards). The above-mentioned image display devices may be in a form (structure) such as a so-called "flexible type," or they may be in a form (structure) that can be bent or folded, such as a so-called "foldable type" or "rollable type."

[0095] The above-mentioned touch sensor is a capacitive touch sensor, and is, for example, a transparent conductive film in which a transparent conductive layer is provided on a glass plate or a transparent plastic film (particularly PET film, polycarbonate film, or cyclic olefin polymer film). It is preferable that the adhesive layer of the present invention is bonded so as to be in contact with the above-mentioned transparent conductive layer.

[0096] Examples of the transparent conductive layer include thin films of ITO (indium tin oxide), ZnO, SnO, and CTO (cadmium tin oxide). Other materials such as silver, copper, and CNT (carbon nanotube) can also be used to form the transparent conductive layer. Furthermore, metal mesh sensors such as Ag nanowires and Ag / Cu can be used in the transparent conductive layer. The touch sensor may also have wiring formed from thin films of copper or silver paste at its ends.

[0097] The optical laminate of the present invention preferably comprises an image display device and a touch sensor. The optical laminate of the present invention can be used in known or conventional optical products that include an image display device and a touch sensor. Examples of such optical products include the electrical and electronic devices described above, and can be used in, for example, image display devices, portable electronic devices, roll displays, etc.

[0098] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it.

[0099] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0100] Example 1 (Preparation of Acrylic Prepolymer Solution) In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, 58 parts by mass of 2-ethylhexyl acrylate (2EHA), 39 parts by mass of lauryl acrylate (LA), 3 parts by mass of 4-hydroxybutyl acrylate (4HBA), and 0.19 parts by mass of a photopolymerization initiator (trade name "Omnirad 184", manufactured by IGM Resins Italia Srl) were added. Then, nitrogen gas was introduced and the mixture was purged with nitrogen for about 20 minutes while stirring. After that, the mixture was purged with nitrogen at 5 mW / cm². ２ Polymerization was carried out by irradiating with ultraviolet light, and the reaction rate was adjusted to 5-15% to obtain an acrylic prepolymer solution.

[0101] (Preparation of Adhesive Composition 1) To the above acrylic prepolymer solution, 0.06 parts by mass of dipentaerythritol hexaacrylate (DPHA) and 5 parts by mass of dicyclopentanyl methacrylate (DCPDMA) were added as crosslinking agents, and 0.3 parts by mass of (product name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) was added as a silane coupling agent, and the mixture was stirred to prepare Adhesive Composition 1.

[0102] (Preparation of Adhesive Sheet) The adhesive composition 1 obtained above was applied to a polyethylene terephthalate (PET) release liner (heavy release liner, trade name "MRF38", manufactured by Mitsubishi Chemical Corporation) so that the final thickness (thickness of the adhesive sheet) was 50 μm, forming a coating layer (adhesive composition layer). Next, a PET release liner (light release liner, trade name "MRE38", manufactured by Mitsubishi Chemical Corporation) was placed on the coating layer to cover the coating layer and block oxygen. Then, a laminate of MRF38 / coating layer (adhesive composition layer) / MRE38 was obtained. Next, a pattern light-shielding film was placed on the upper surface (MRE38 side) of this laminate, and a rack light of 2.5 mW / cm² was applied from the upper surface of the laminate through the pattern light-shielding film. ２ The ultraviolet light at an illuminance of 2400 mJ / cm² is measured by the cumulative light intensity of 2400 mJ / cm². ２Polymerization was carried out by irradiation until the desired result was reached. In this way, a substrate-less adhesive sheet (thickness 50 μm) was manufactured, consisting of an adhesive layer having 118 hard regions (relatively hard) that were cured by UV irradiation and 118 uncured, relatively soft regions (relatively soft) that were not cured by UV irradiation, arranged alternately adjacent to each other (total of 236 regions). The width of each soft region and hard region in the obtained adhesive sheet was 0.3 mm, and the total width of the adhesive layer was 70.8 mm (W1 / W2 = 1).

[0103] Comparative Example 1 A substrate-less adhesive sheet (thickness 50 μm) was manufactured in the same manner as in Example 1, except that the boundary between the soft and hard regions was changed to be perpendicular to the boundary between the soft and hard regions in the adhesive sheet of Example 1. The adhesive layer consisted of an adhesive layer having 118 hard regions and 118 soft regions (236 in total) arranged alternately adjacent to each other. The width of each soft and hard region in the obtained adhesive sheet was 0.3 mm, and the total width of the adhesive layer was 70.8 mm (W1 / W2 = 1).

[0104] Manufacturing Example 1: An adhesive sheet (thickness 35 μm) was manufactured in the same manner as in Example 1, except that the adhesive layer consisted only of a soft region (total width length 70.8 mm) and the thickness was changed.

[0105] <Evaluation> The adhesive sheets obtained in the examples were evaluated as follows.

[0106] (1) Elastic Modulus In order to obtain the elastic moduli of the soft and hard regions of the adhesive layer obtained in Example 1, adhesive layers consisting only of the soft region and only of the hard region were prepared. These adhesive layers were laminated to create measurement samples with a thickness of 2 mm, and the elastic moduli were measured by dynamic viscoelasticity measurement using the "Advanced Rheometric Expansion System (ARES)" manufactured by TA Instruments. The measurement conditions were as follows. As a result, the maximum value of the elastic modulus of the soft region in the range of -20 to 100°C was 35.9 kPa (-20°C), and the minimum value was 6.53 kPa (100°C). In addition, at 25°C, the elastic modulus G (Soft) of the soft region was 14.2 kPa, and the elastic modulus G (Hard) of the hard region was 42.6 kPa. Therefore, the [B / A] ratio was 0.18, and the [G (Hard) / G (Soft)] ratio was 1.1.

[0107] (2) Peel Adhesion Strength In order to obtain the peel adhesion strength of the soft and hard regions of the adhesive layer obtained in Example 1, adhesive layers composed only of the soft region (uncured region) and only of the hard region (cured region) were prepared, and the peel strength (peel adhesion strength) of these adhesive layers to the glass plate was measured. Specifically, under a measurement environment of 23°C and 50% RH, the release liner was peeled off one side of an adhesive sheet in which release liners were attached to both sides of the adhesive layer, a PET film with a thickness of 25 μm was attached as a backing, and the sheet was cut to a size of 10 mm in width and 100 mm in length to be used as a test piece. The release liner was peeled off the other side of the test piece, and it was pressed onto the surface of an alkali glass plate, which was to be adhered to, by moving a hand roller back and forth once. This was placed in a pressurized degassing device (autoclave) and autoclaved for 30 minutes at a temperature of 50°C and a pressure of 0.5 MPa. After that, it was left for 24 hours in an atmosphere of 23°C and 50% RH, and then the peel strength (adhesion) [N / 10mm] was measured using a universal tensile and compression tester at a tensile speed of 60 mm / min and a peel angle of 180 degrees. A benchtop precision universal tester (product name "AG-X plus", manufactured by Shimadzu Corporation) was used as the universal tensile and compression tester. As a result, the peel adhesion strength F (Soft) in the soft region was 4.9 N / 10mm, and the peel adhesion strength F (Hard) in the hard region was 5.6 N / 10mm. Therefore, [F (Hard) / F (Soft)] was 1.1.

[0108] (3) The refractive index of the soft and hard regions of the adhesive layer obtained in Refractive Index Example 1 was measured using a prism coupler. As a result, the refractive index of the soft region (Soft) was 1.46 and the refractive index of the hard region (Hard) was 1.46. Therefore, |Refractive Index (Soft) - Refractive Index (Hard)| was 0.0.

[0109] (4) Transmittance (Total Light Transmittance) In order to obtain the total light transmittance of the soft and hard regions of the adhesive layer obtained in Example 1, adhesive layers consisting only of the soft region (uncured region) and only of the hard region (cured region) were prepared, and the total light transmittance of these adhesive layers was measured. Specifically, the release liners on both sides of the adhesive sheet were peeled off and attached to a measuring jig, and the total light transmittance was measured using a spectrophotometer (product name "U4150", manufactured by Hitachi High-Tech Corporation). As a result, the transmittance of the soft region (Soft) was 94%, and the transmittance of the hard region (Hard) was 94%. Therefore, |Transmittance (Soft) - Transmittance (Hard)| was 0.0.

[0110] (5) Haze To obtain the haze values ​​of the soft and hard regions of the adhesive layer obtained in Example 1, adhesive layers consisting only of the soft region (uncured region) and only of the hard region (cured region) were prepared, and the haze was measured for these adhesive layers. Specifically, the release liners on both sides of the adhesive sheet were peeled off, and one side was bonded to alkali-free glass (thickness 0.8 to 1.0 mm, total light transmittance 92%, haze 0.4%) to test specimens. The haze of the test specimens was measured using a haze meter (product name "HAZEMETER HM-150", manufactured by Murakami Color Technology Research Institute Co., Ltd.) in a measurement environment of 23°C. The value obtained by subtracting the haze of the alkali-free glass from the measured value was taken as the haze value of the adhesive layer. As a result, the haze of the soft region (Soft) was 0.1%, and the haze of the hard region (Hard) was 0.2%. Therefore, |Hayes (Soft) - Hayes (Hard)| was 0.1.

[0111] (6) Flexural resistance test A laminate was prepared by bonding a PET film (25 μm thick) and a glass plate (30 μm thick) together with an adhesive sheet (35 μm thick) prepared in Manufacturing Example 1, and then bonding a PET film (50 μm thick) to the glass plate surface of the laminate via the adhesive sheet obtained in Example 1. Then, an adhesive layer was formed on the surface of two plates (product name "Tension-Free® Folding Clamshell-type", manufactured by Yuasa System Equipment Co., Ltd.) with a width of 75 mm (length of one direction D1 in Figure 3), and they were arranged so that the width of the separation region was 12 mm (along one direction D1 in Figure 3, plate width 75 mm / separation distance width 12 mm / plate width 75 mm). For Example 1, an evaluation sample was prepared by attaching the 50 μm thick PET film side of the laminate to the two adherends such that the direction of extension of the boundary between the soft and hard regions of the adhesive sheet and the separated region were perpendicular (i.e., the boundary and the bending direction were parallel, as shown in Figure 3). For Comparative Example 1, an evaluation sample was prepared by attaching the laminate to the two adherends such that the direction of extension of the boundary between the soft and hard regions of the adhesive sheet and the separated region were parallel (i.e., the boundary and the bending direction were perpendicular). The two adherends were folded in 0.5 seconds so that the adhesive surfaces of the two adherends were spaced 0.5 mm apart, with the evaluation sample on the inside. The folded state was then released in 0.5 seconds to open the evaluation sample and return it to its original state. This process was considered one fold, and it was repeated 200,000 times. Visual inspection was performed to check for peeling around the folds at 0, 100,000, and 200,000 folds. As a result, when using the adhesive sheet of Example 1, no peeling was observed even after 200,000 bends. On the other hand, when using the adhesive sheet of Comparative Example 1, no peeling was observed after 100,000 bends, but peeling was observed after 200,000 bends. Therefore, it was determined that the adhesive sheet of Example 1 is less likely to peel around the bends even when repeatedly bent after being attached to an object.

[0112] The following describes variations of the invention relating to this disclosure. [Note 1] An adhesive sheet comprising an adhesive layer and used by bending in at least one direction, wherein the adhesive layer has a soft region and a hard region adjacent to each other along a direction perpendicular to the one direction within the same plane. [Note 2] The adhesive sheet according to Note 1, wherein the width W1 of the soft region and the width W2 of the hard region in the vertical direction satisfy the following formula (1): 0.3 ≤ W1 / W2 ≤ 3 (1) [Note 3] The adhesive sheet according to Note 1 or 2, wherein the maximum value A of the elastic modulus of the soft region at -20 to 100°C is 60 kPa or less. [Note 4] The adhesive sheet according to any one of Notes 1 to 3, wherein the maximum value A and minimum value B of the elastic modulus of the soft region at -20 to 100°C satisfy the following formula (2). 0.1 ≤ B / A < 1 (2) [Note 5] The adhesive sheet described in any one of Notes 1 to 4, wherein the elastic modulus G (Hard) of the hard region at room temperature and the elastic modulus G (Soft) of the soft region at room temperature satisfy the following formula (3). 2 ≤ G (Hard) / G (Soft) ≤ 5 × 10 ３ (3)

[0113] 1 Adhesive layer 2 Cover member 3 Glass plate 4 Adhesive sheet 5 Optical member 6, 7 Adhesive body 8, 9 Adhesive sheet 10 Adhesive sheet 11, 11a, 11b, 11c Soft region 12, 12a, 12b, 12c Hard region 13 Optical laminate 14 Adhesive composition 1 15 Adhesive composition 2 16 Applicator 21, 22 Peel-off liner R Separation region V Bent portion Y Width of separation region

Claims

1. An adhesive sheet comprising an adhesive layer, which is used by bending in at least one direction, wherein the adhesive layer has a soft region and a hard region adjacent to each other along a direction perpendicular to the one direction.

2. The adhesive sheet according to claim 1, wherein the width W1 of the soft region and the width W2 of the hard region in the vertical direction satisfy the following formula (1): 0.3 ≤ W1 / W2 ≤ 3 (1) 3. The adhesive sheet according to claim 1 or 2, wherein the maximum value A of the elastic modulus of the soft region at -20 to 100°C is 60 kPa or less.

4. The adhesive sheet according to claim 1 or 2, wherein the maximum value A and minimum value B of the elastic modulus of the soft region in the range of -20 to 100°C satisfy the following formula (2): 0.1 ≤ B / A < 1 (2) 5. The adhesive sheet according to claim 1 or 2, wherein the elastic modulus G (Hard) of the hard region at room temperature and the elastic modulus G (Soft) of the soft region at room temperature satisfy the following formula (3): 2 ≤ G (Hard) / G (Soft) ≤ 5 × 10 ３ (3)

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