Adhesive material

Abstract

To provide an adhesive member with excellent adhesion to an adherend and suppressed contamination.SOLUTION: An adhesive member has a base material having a plurality of convex portions on at least one surface, the convex portions having a breaking strength of 18 MPa to 50 MPa and a swelling ratio of 110% to 150% after immersion in toluene at 25°C for 24 hours.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to adhesive materials. [Background technology]

[0002] Generally, when bonding a substrate to an adherend, an adhesive layer is applied to the substrate surface, and the substrate and adherend are bonded through chemical interactions such as hydrogen bonding, ionic bonding, and electronic interactions. Examples of adhesives used include acrylic adhesives and silicone adhesives.

[0003] However, when an adhesive is used to bond a substrate to an adherend, the adhesive tends to become more difficult to remove over time, or when heated. Furthermore, there is a problem of adhesive residue remaining on the adherend after it has been removed.

[0004] Therefore, research is being conducted on using physical forces such as van der Waals force and air pressure to bond a substrate to an adherend. When using physical forces to bond a substrate to an adherend, the adhesive force changes significantly depending on the direction in which the force is applied. For this reason, research is also being conducted on adhesive materials that can adhere strongly or peel off easily depending on the direction in which the force is applied, i.e., adhesive materials with direction-dependent adhesive force. Such adhesive materials leave no residue on the adherend and are easy to reuse.

[0005] The adhesive force of gecko feet is direction-dependent, and it is known that geckos utilize this characteristic to walk by repeatedly sticking and detaching. Therefore, several examples of artificial adhesive materials that mimic the microstructure of the gecko foot surface have been reported.

[0006] For example, an artificial adhesive member that mimics the microstructure of a gecko's foot surface has been disclosed, which has fine protrusions such as cylindrical or mushroom-shaped on the side that comes into contact with the object to be adhered to (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2014 / 124352 [Overview of the project] [Problems that the invention aims to solve]

[0008] In adhesive members having fine protrusions such as cylindrical or mushroom shapes, as described in Patent Document 1, the adhesion to the adherend may not be sufficient, or some of the protrusions may break off and remain on the adherend when the adhesive member is peeled off from the adherend. Therefore, it is desirable that adhesive members having fine protrusions such as cylindrical or mushroom shapes have excellent adhesion and that the property of some of the protrusions breaking off and remaining on the adherend when the adhesive member is peeled off from the adherend (hereinafter referred to as "contamination") is suppressed.

[0009] This disclosure has been made in view of the above, and aims to provide an adhesive member that has excellent adhesion to the adherend and suppresses contamination. [Means for solving the problem]

[0010] The specific measures to solve the above problems are as follows: <1> A substrate having multiple protrusions on at least one surface, The aforementioned protrusion is an adhesive material having a breaking strength of 18 MPa to 50 MPa and a swelling rate of 110% to 150% after immersion in toluene at 25°C for 24 hours. <2> The aforementioned protrusion has a wider tip than its base. <1> The adhesive material described above. <3> The substrate comprises a surface layer that is arranged across the tips of at least two of the protrusions formed on one surface of the substrate and covers at least a portion of the surface of the substrate having the plurality of protrusions, A space exists between the bottom surface on which the plurality of protrusions are formed and the surface of the surface layer that faces the bottom surface. <1> or <2> The adhesive material described above. <4> The thickness of the surface layer is 0.1 μm to 50 μm. <3> The adhesive material described above. <5> The width of the base of the protrusion is 5 nm to 250 μm. <1> ~ <4> The adhesive material described in any one of the following. <6> The ratio of the width of the tip of the convex part to the width of the base of the convex part is between 1.0 and 1.4. <1> ~ <5> The adhesive material described in any one of the following. <7> The distance between the protrusions is 10 nm to 500 μm. <1> ~ <6> The adhesive material described in any one of the following. <8> The height of the protrusions is 2.5 nm to 500 μm. <1> ~ <7> The adhesive material described in any one of the following. <9> The ratio of the height of the protrusion to the width of the base of the protrusion is between 0.2 and 10.0. <1> ~ <8> The adhesive material described in any one of the following. <10> The aforementioned protrusions are made of a resin material having a structure formed by the polymerization of at least one selected from the group consisting of (meth)acrylate compounds, urethane (meth)acrylate compounds, epoxy (meth)acrylate compounds, and olefin compounds. <1> ~ <9> The adhesive material described in any one of the following. [Effects of the Invention]

[0011] According to this disclosure, it is possible to provide an adhesive member that has excellent adhesion to the adherend and suppresses contamination. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram of the adhesive member according to the first embodiment of the present invention. [Figure 2] This is a schematic diagram of the adhesive member according to the second embodiment of the present invention. [Figure 3] This is a schematic diagram of the adhesive member according to the third embodiment of the present invention. [Figure 4] (a) A schematic diagram of an adhesive member having a narrower protrusion and (b) a schematic diagram of an adhesive member having a wider protrusion. [Figure 5](a) Schematic configuration diagrams of an adhesive member with convex portions arranged in a square lattice pattern and (b) an adhesive member with convex portions arranged in a hexagonal shape. [Figure 6] Schematic configuration diagram of an adhesive member according to a modified example of an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0013] In the present disclosure, the numerical range represented using "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In the numerical ranges described step by step in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other step-by-step descriptions. Also, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value of that numerical range may be replaced with the value shown in the examples. In the present disclosure, "(meth)acrylate" means acrylate or methacrylate.

[0014] [Adhesive Member] The adhesive member of the present disclosure includes a base material having a plurality of convex portions on at least one surface, and the convex portions have a breaking strength of 18 MPa to 50 MPa and a swelling ratio of 110% to 150% after being immersed in toluene at 25°C for 24 hours. By satisfying the breaking strength and the swelling ratio within the aforementioned numerical ranges, the adhesive member of the present disclosure has excellent adhesiveness to the adherend and suppresses contamination.

[0015] In the adhesive member of the present disclosure, the convex portions have a breaking strength of 18 MPa to 50 MPa, and from the viewpoint of adhesiveness, it is preferably 20 MPa to 48 MPa, more preferably 20 MPa to 45 MPa, and even more preferably 20 MPa to 40 MPa. More specifically, when the breaking strength of the convex portions is 18 MPa or more, the adhesive member has excellent adhesive force to the adherend, and when the adhesive member is peeled from the adherend, a part of the adhesive member is prevented from being damaged and remaining on the adherend (contamination). Also, when the breaking strength of the convex portions is 50 MPa or less, the adhesive member has excellent adhesive force to the adherend. The breaking strength of the protrusion may be measured by cutting out the protrusion or a portion of the same material as the protrusion from the adhesive member and using the method described in the examples below.

[0016] In the adhesive member of this disclosure, the swelling rate of the protrusions after immersion in toluene at 25°C for 24 hours is 110% to 150%, preferably 110% to 145%, more preferably 115% to 140%, and even more preferably 120% to 140% from the viewpoint of adhesiveness and low contamination. More specifically, an expansion rate of 110% or more in the protrusions provides excellent adhesion to the adherend. An expansion rate of 150% or less in the protrusions suppresses contamination when the adhesive member is peeled off the adherend. The swelling rate of the protrusions is a value measured by cutting out the protrusions or a portion of the same material as the protrusions from the adhesive member and using the method described in the examples below.

[0017] In the adhesive member of this disclosure, the protrusions satisfy the aforementioned breaking strength and swelling rate, and from the viewpoint of adhesiveness and processability, it is preferable that the elongation at break of the protrusions is 10% to 1000%. More preferably, the elongation at break of the protrusions is 20% to 750%, and even more preferably 50% to 500%. The elongation at break of the protrusions may be measured, like the breaking strength, by cutting out the protrusions or a portion of the same material as the protrusions from the adhesive member and using the method described in the examples below.

[0018] In the adhesive member of this disclosure, the protrusions satisfy the aforementioned breaking strength and swelling rate, and from the viewpoint of using the adhesive member at or near room temperature, the glass transition temperature after curing is preferably -50°C to 50°C, and more preferably -20°C to 25°C. A glass transition temperature of -50°C or higher makes it easy to peel the adhesive member from the adherend even when the environment in which the adhesive member is used is high temperature. A glass transition temperature of 50°C or lower eliminates the need for heating or other treatments when attaching to the adherend, or reduces the burden of heating treatment. The glass transition temperature of the protrusion can be measured by cutting out the protrusion or a portion of the same material as the protrusion from the adhesive member and measuring it with a thermal analyzer (DSC - Differential Scanning Calorimetry), for example, by the method described in the examples below.

[0019] The breaking strength and swelling rate of the protrusions can be appropriately adjusted by adjusting the crosslinking density of the resin material when the protrusions are made of resin material. For example, increasing the crosslinking density of the resin material constituting the protrusions tends to increase the breaking strength of the protrusions and decrease the swelling rate of the protrusions. On the other hand, decreasing the crosslinking density of the resin material constituting the protrusions tends to decrease the breaking strength of the protrusions and increase the swelling rate of the protrusions.

[0020] Because the breaking strength of the protrusions is 18 MPa or higher and the swelling rate of the protrusions is 150% or lower, when forming the protrusions using an imprint or other method with a mold having an uneven shape, the tips of the protrusions are less likely to break, and the loss of the pattern shape during the production of adhesive materials is suppressed, resulting in superior formability. Furthermore, the retention of parts of the damaged pattern shape in the mold having an uneven shape is suppressed, resulting in superior productivity of adhesive materials.

[0021] The adhesive member of this disclosure can be adhered to a substrate by bringing the side on which the protrusion is formed into contact with the substrate.

[0022] The adhesive member of this disclosure may be capable of maintaining adhesiveness with the adherend semi-permanently. For example, it may have anisotropic adhesiveness due to the convex portion having an asymmetrical shape in the thickness direction, planar direction, etc., or the convex portion being composed of different materials at different parts such as the base and tip, so that adhesion to the adherend is released when force is applied in a specific direction. It may also be capable of releasing adhesion to the adherend by applying stimuli such as ultraviolet light or heat to the adhesive member.

[0023] The shape of the adhesive member is not particularly limited as long as it is a shape that can exhibit adhesiveness with the adherend when the protrusions are in contact with the adherend, and examples include tape, sheet, and film shapes.

[0024] The adhesive strength of the adhesive member of this disclosure can be adjusted according to the purpose, type of adherend, etc. For example, it may be 0.01 N / 25 mm to 50 N / 25 mm, 0.1 N / 25 mm to 30 N / 25 mm, or 0.2 N / 25 mm to 20 N / 25 mm. Generally, it is preferable to be able to adjust it within the range of 0.1 N / 25 mm to 20 N / 25 mm, as this offers high versatility and makes peeling after use easy. In this disclosure, the adhesive strength is the value obtained by converting the stress when the adhesive member attached to the adherend is peeled off at a peeling angle of 180 degrees to N / 25mm, and is measured by the method described in the examples.

[0025] (base material) The adhesive member of this disclosure comprises a substrate having a plurality of protrusions on at least one surface. For example, an uneven surface may be formed on at least one main surface (the surface with the largest area), or an uneven surface may be formed on two main surfaces.

[0026] The protrusions on the base material are not particularly limited and may have any shape, such as cylindrical, conical, tapered, inversely tapered, rectangular, polygonal columnar, mushroom-shaped, umbrella-shaped, or dumbbell-shaped. Furthermore, the central axis of the protrusions on the base material may be inclined with respect to the vertical direction.

[0027] The shape of the convex portion when viewed from above is not particularly limited. For example, it may be a regular shape such as a circle, ellipse, triangle, square, rhombus, rectangle, strip, hexagon, or other polygon, or a star or grid. It may also be an irregular shape.

[0028] The width of the tip of the protrusion on the base material may be greater than the width of the base. Specifically, the tip may be wider than the base due to a reverse taper, mushroom shape, umbrella shape, etc. For example, if the protrusion is mushroom-shaped, umbrella-shaped, etc., stress tends to concentrate at the base of the tip, which can become the starting point for fracture. However, fracture tends to be suppressed if the fracture strength and swelling rate of the protrusion satisfy the aforementioned numerical ranges. Furthermore, the width of the tip of the protrusion may be smaller than the width of the base, or the width of the base and the width of the tip may be the same.

[0029] The tip of the protrusion may be fibrous, and may have multiple bumps and grooves.

[0030] The width of the base of the protrusion may be 5 nm to 250 μm, 0.5 μm to 250 μm, or 5 μm to 50 μm. In this disclosure, the width of the base of the protrusion refers to the length at which the distance between two parallel planes is maximized when the perimeter of the bottom of the protrusion is sandwiched between two parallel planes. If the convex part is cylindrical or conical, for example, the diameter of the base corresponds to the width of the base of the convex part; if it is rectangular, the length of the diagonal of the base corresponds to the width of the base of the convex part; and if it is triangular prism, the maximum distance between one side of the base and a vertex that does not make up that side corresponds to the width of the base of the convex part.

[0031] The width of the tip of the protrusion may be 5 nm to 350 μm, 0.5 μm to 250 μm, or 6 μm to 60 μm. In this disclosure, the width of the tip of the protrusion refers to the length at which the distance between two parallel planes is maximized when the perimeter of the top of the protrusion is sandwiched between two parallel planes.

[0032] The ratio of the width of the tip of the protrusion to the width of the base of the protrusion (width of the tip of the protrusion / width of the base of the protrusion) may be 1.0 to 1.5, 1.05 to 1.4, or 1.05 to 1.2.

[0033] The distance between the protrusions on the substrate may be 10 nm to 500 μm, 1 μm to 500 μm, or 10 μm to 100 μm. In this disclosure, the distance between convexities refers to the distance between the centers of two adjacent convexities.

[0034] The height of the protrusions on the substrate may be 2.5 nm to 500 μm, 0.5 μm to 250 μm, or 5 μm to 50 μm.

[0035] The ratio of the height of the protrusion to the width of the base of the protrusion (height of the protrusion / width of the base of the protrusion) may be 0.2 to 10.0, 0.3 to 3.0, or 0.5 to 2.0.

[0036] The ratio of the distance between the protrusions to the width of the base of the protrusions (distance between protrusions / width of the base of the protrusions) is preferably 0.05 to 20, more preferably 0.1 to 10, and even more preferably 0.5 to 5.

[0037] In a plan view, the area occupied by the protrusions in the adhesive member may be 5% to 80%, 10% to 70%, or 20% to 60% of the entire surface on which the protrusions are formed (including the area occupied by the protrusions).

[0038] The base material only needs to comprise a plurality of protrusions and a base on which the plurality of protrusions are formed. The material constituting the protrusions and the material constituting the base may be the same or different. If the material constituting the protrusions and the material constituting the base are the same, the adhesive member may be formed by creating the protrusions on the base material, for example, by imprinting using a mold with an uneven shape. If the material constituting the protrusions and the material constituting the base are different, the adhesive member may be formed by separately arranging protrusions on the base. Furthermore, the protrusion may be made of a single material, or it may be made of a combination of multiple materials depending on the purpose. For example, the material that makes up the base of the protrusion and the material that makes up the tip may be different.

[0039] The materials constituting the base, that is, the materials constituting the base and the materials constituting the protrusions, can each be independently resin materials, etc. The materials constituting the base are not particularly limited, and the materials constituting the protrusions are not particularly limited as long as the breaking strength and swelling rate satisfy the aforementioned numerical ranges.

[0040] Examples of resin materials include olefin resins, polyester resins, polyurethane resins, polyimide resins, silicone resins, styrene resins, acrylic resins, amide resins, ester resins, and carbonate resins.

[0041] From the viewpoint of the adhesive properties of the adhesive member, the resin material preferably has a structure formed by the polymerization of at least one selected from the group consisting of (meth)acrylate compounds, urethane (meth)acrylate compounds, epoxy (meth)acrylate compounds, and olefin compounds, and more preferably has a structure formed by the polymerization of at least one selected from the group consisting of difunctional or trifunctional (meth)acrylate compounds, difunctional or trifunctional urethane (meth)acrylate compounds, and difunctional or trifunctional epoxy (meth)acrylate compounds.

[0042] The resin material may have a crosslinked structure. The crosslinked structure may be a chemical crosslink, in which covalent bonds are formed by a chemical reaction and molecules are bonded together, or it may be a physical crosslink, in which molecules are bonded by weak physical forces other than covalent bonds, such as hydrogen bonds. For example, a chemical crosslink may be formed by polymerization of at least one selected from the group consisting of (meth)acrylate compounds, urethane (meth)acrylate compounds, and epoxy (meth)acrylate compounds. Whether or not a resin material has a cross-linked structure can be confirmed by methods such as IR (infrared spectroscopy) analysis or evaluation of the mechanical properties of a micro-region (e.g., nanoindentation).

[0043] Furthermore, the protrusions may contain a substance that exhibits stimulus responsiveness, such as UV (ultraviolet) light or heat, which changes its chemical structure when exposed to such stimuli. This allows for a configuration in which, for example, the adhesive material can be released from its adhesion to the adherend by applying UV light, heat, or other stimuli to the substrate.

[0044] The adhesive member of this disclosure may be arranged across the tips of at least two protrusions formed on one surface of the substrate and may include a surface layer that covers at least a portion of the surface of the substrate having multiple protrusions. For example, it may be arranged across the tips of 10 or more protrusions on the substrate. Furthermore, a space may exist between the bottom surface on which the multiple protrusions are formed and the surface of the surface layer that faces the bottom surface.

[0045] If the adhesive member has a surface layer, it is not necessary for all protrusions on a single surface to be covered by the surface layer; at least two protrusions may be covered by the surface layer. Furthermore, multiple surface layers covering at least two protrusions may be independently arranged on a single surface.

[0046] The ratio of the height of the protrusions on the substrate to the thickness of the surface layer (height of protrusions / thickness of the surface layer) is preferably 0.2 to 5000, more preferably 0.5 to 1000, and even more preferably 1.0 to 500.

[0047] The thickness of the surface layer is preferably 0.1 μm to 50 μm, more preferably 3 μm to 20 μm, and even more preferably 5 μm to 15 μm, in order to further enhance adhesion with the adherend.

[0048] The materials included in the surface layer are not particularly limited, and include resins such as olefin resins, polyester resins, polyurethane resins, polyimide resins, silicone resins, styrene resins, acrylic resins, amide resins, ester resins, and carbonate resins. Among these, olefin resins or silicone resins are preferred because they have superior adhesion to the adherend. The aforementioned substrate and surface layer may contain the same material.

[0049] The surface layer is preferably formed from a material with a high elastic modulus and low tackiness, from the viewpoint of maintaining the shape of the protrusions, suppressing stickiness, ensuring stable adhesive strength, easy peeling after use, and minimizing contamination of the adherend after peeling.

[0050] The storage modulus of the surface layer at 25°C is preferably 1 MPa to 1 GPa, more preferably 5 MPa to 1 GPa, and even more preferably 10 MPa to 50 MPa. Furthermore, it is preferable that the storage modulus of the surface layer at 25°C is smaller than that of the substrate at 25°C. The storage modulus of the surface layer is measured as follows: First, a test specimen made of the material contained in the surface layer is prepared, for example, a specimen with a width of 3 mm, a length of 5 cm, and a thickness of 50 μm. A solid viscoelasticity analyzer (e.g., RSA-III, manufactured by T.A. Instrument Japan Co., Ltd.) is used. The test specimen is set in a jig with a chuck distance of 20 mm, and the storage modulus E' of the material contained in the surface layer is determined by measuring the storage modulus E' in tensile mode at a measurement frequency of 1 Hz while raising the temperature from -50°C to 100°C at a rate of 3°C / min under a nitrogen environment.

[0051] The tack force of the surface layer is 25 N / cm 2 Preferably, it is 20 N / cm 2 More preferably, the following is preferred: 10 N / cm 2 It is even more preferable that the following conditions are met: The tack force of the aforementioned surface layer is 0.1 N / cm². 2 It may be greater than or equal to 0.3 N / cm 2 That's fine too. The tack force of the surface layer is measured as follows: First, prepare a test specimen made of the material contained in the surface layer, for example, a specimen with dimensions of 2.5 cm wide × 7 cm long × 50 μm thick. Use a tacking tester (e.g., TAC-II, manufactured by Resca Co., Ltd.). At room temperature (25°C), a 5 mm diameter stainless steel cylindrical probe is brought into contact with the surface of the test specimen at a speed of 120 mm / min, and a load of 200 N / cm is applied. 2 After applying the load for 1 second, the probe is pulled away vertically at a speed of 120 mm / min. By measuring the resistance value (load value) experienced by the probe at this time, the tack force of the material contained in the surface layer at 25°C is determined.

[0052] If the adhesive member of this disclosure includes a surface layer, the width of the base portion of the protrusion and the width of the tip portion of the protrusion may be independently 0.5 μm to 200 μm, 0.5 μm to 100 μm, 1 μm to 20 μm, or 2 μm to 10 μm.

[0053] If the adhesive member of this disclosure includes a surface layer, the distance between the protrusions may be 0.1 μm to 500 μm, 1 μm to 100 μm, or 2 μm to 50 μm. In this case, the distance between the protrusions refers to the distance between the centers of two adjacent protrusions.

[0054] If the adhesive member of this disclosure includes a surface layer, the height of the protrusion may be 0.1 μm to 200 μm, 1 μm to 100 μm, or 2 μm to 50 μm.

[0055] When the adhesive member of this disclosure includes a surface layer, the ratio of the height of the protrusion to the width of the base or tip of the protrusion (height of the protrusion / width of the base of the protrusion, or height of the protrusion / width of the tip of the protrusion) may be independently 1 to 15, 1.5 to 10, or 2 to 5. When the ratio of the height of the protrusion to the width of the base or tip of the protrusion is 1 or more, the adhesion to the adherend tends to be superior, and when the ratio of the height of the protrusion to the width of the base or tip of the protrusion is 15 or less, the strength of the protrusion tends to be superior.

[0056] If the adhesive member of this disclosure includes a surface layer, the ratio of the distance between the protrusions to the width of the base of the protrusion or the width of the tip of the protrusion (distance between protrusions / width of the base of the protrusion, or distance between protrusions / width of the tip of the protrusion) may be 0.05 to 10, 0.1 to 5, or 0.2 to 2.

[0057] If the adhesive member of this disclosure includes a surface layer, the ratio of the total surface layer area (including the area occupied by the protrusion) to the area occupied by the bottom surface of the protrusion may be 1 to 100, 1.5 to 50, or 2 to 20, from the viewpoint of the adhesiveness of the adhesive member and the shape retention of the adhesive member.

[0058] When the adhesive member of this disclosure includes a surface layer, the proportion (volume ratio) of the protrusions in the region obtained by multiplying the height of the protrusions by the entire surface on which the protrusions are formed may be 0.0001 to 0.5, 0.02 to 0.4, or 0.05 to 0.33, from the viewpoint of the adhesiveness and shape retention of the adhesive member.

[0059] Embodiments of the adhesive members of this disclosure will be described with reference to the drawings, but this disclosure is not limited to these embodiments. Furthermore, the sizes of the members in each figure are conceptual, and the relative relationships of the sizes between the members are not limited thereto.

[0060] (First Embodiment) In the adhesive member 10 of the first embodiment shown in Figure 1, a plurality of protrusions 2 are formed on one surface of the base portion 1. The plurality of protrusions 2 have a breaking strength of 18 MPa to 50 MPa and a swelling rate of 110% to 150% after immersion in toluene at 25°C for 24 hours.

[0061] (Second embodiment) In the adhesive member 20 of the second embodiment shown in Figure 2, a plurality of protrusions 2 are formed on one surface of the base 1, and the width of the tip portion 3 of the protrusion 2 is greater than the width of the base portion of the protrusion 2, so that the overall shape of the protrusion is mushroom-shaped.

[0062] (Third embodiment) In the adhesive member 30 of the third embodiment shown in Figure 3, a plurality of protrusions 2 are formed on one surface of the base 1, and a surface layer 4 is formed spanning the tips of the plurality of protrusions 2. Furthermore, a space 5 exists between the bottom surface on which the plurality of protrusions 2 are formed and the surface of the surface layer 4 that faces the bottom surface.

[0063] In the adhesive member of this disclosure, the adhesiveness to the adherend can be adjusted by adjusting the ratio of the area occupied by the protrusions to the entire surface on which the protrusions are formed. For example, by reducing the width of the protrusions or sparsely arranging the protrusions, the adhesiveness to the adherend on the surface layer can be increased compared to cases where the width of the protrusions is increased or the arrangement of the protrusions is denser. More specifically, as shown in Figure 4(a), by making the width of the protrusions 2 smaller and reducing the proportion occupied by the protrusions 2, the adhesiveness of the adhesive member to the adherend can be increased compared to cases where the width of the protrusions 2 is increased and the proportion occupied by the protrusions 2 is increased, as shown in Figure 4(b).

[0064] The arrangement of the protrusions is not particularly limited; as long as the distance between the protrusions is within a desirable range, they may be arranged in a periodic manner such as a square grid, triangular grid, or around the same circumference, or they may be arranged irregularly. As shown in Figure 5(a), adjacent protrusions 2 may be arranged at approximately equal intervals. Also, as shown in Figure 5(a), the arrangement of the protrusions 2 may be uniform, or as shown in Figure 5(b), there may be localized variations in the density of the arrangement of the protrusions 2 (in the figure, a hexagonal arrangement).

[0065] Hereinafter, modified examples of the adhesive member of this disclosure will be described with reference to Figure 6. In the following modified examples, an example will be described in which a surface layer 4 is formed across the tips of multiple protrusions 2.

[0066] (Variation 1) In the first modified example, if the adhesive member has a configuration in which both the surface layer (main surface) and the base material (main surface) adhere to the adherend, the thickness of the surface layer 4 may be made smaller than the thickness of the base 1, as shown in Figure 6(a), to create a difference in the adhesiveness of the surface layer 4 and the base 1. Since reducing the thickness of the surface tends to improve the adhesiveness to the adherend, in the configuration shown in Figure 6(a), the adhesiveness of the surface layer 4 tends to be higher than that of the base 1.

[0067] (Modification 2) Furthermore, the adhesive member of the modified example 2 may have a configuration in which a plurality of protrusions 2 are formed on each of the two main surfaces of the base 1, as shown in Figure 6(b), and surface layers 4 and 6 covering the plurality of protrusions 2 are arranged on the two main surfaces of the base 1. In this case, the arrangement of the plurality of protrusions 2 on one main surface of the base 1 and the arrangement of the plurality of protrusions 2 on the other main surface of the base 1 may be different, and a difference in the adhesiveness of the two surface layers 4 and 6 may be created. For example, the surface layer 6 on the side where the protrusions 2 are spaced far apart tends to have improved adhesiveness with respect to the adherend compared to the surface layer 4 on the side where the protrusions 2 are spaced far apart and closely arranged. Therefore, in the structure shown in Figure 6(b), the surface layer 6 on the side where the protrusions 2 are spaced far apart tends to have improved adhesiveness with respect to the adherend compared to the surface layer 4 on the side where the protrusions 2 are closely arranged. Furthermore, in the modified example 2, the adhesive member may not have surface layers 4 and 6, and multiple protrusions 2 may be formed on each of the two main surfaces of the base 1.

[0068] (Variation 3) Furthermore, the adhesive member of the modified example 3 may include a surface-treated portion 7 on the surface layer 4 that comes into contact with the adherend, as shown in Figure 6(c). The surface-treated portion 7 preferably has a shape that further improves adhesion to the adherend, and may have a nanoscale or microscale fine uneven shape, and specifically may have a shape like that shown in "Nitto Denko Technical Report No. 90, 2009, vol. 47, Gecko Tape Using Carbon Nanotubes".

[0069] (Modification 4) Furthermore, as shown in Figure 6(d), the adhesive member of Modified Example 4 may have a cross-linked structure in the resin material constituting the base 1 and the resin material constituting the protrusion 2. The adhesive member of Modified Example 4 tends to have excellent heat resistance, durability, mechanical strength, etc.

[0070] (Variation 5) Furthermore, the adhesive member of Modification 5 may have a configuration in which the central axis of the protrusion 2 on the base 1 is inclined with respect to the vertical direction, as shown in Figure 6(e). This makes it possible to increase the adhesiveness of the adherend against force in a specific direction.

[0071] The following describes two methods for manufacturing the adhesive member of this disclosure: Method 1 and Method 2.

[0072] [Method for manufacturing adhesive material 1] The method for manufacturing an adhesive member 1 includes the steps of: preparing a resin composition containing a thermosetting resin (hereinafter referred to as "step Ia"), applying the resin composition onto a mold having an uneven shape (hereinafter referred to as "step IIa"), curing the resin composition applied onto the mold (hereinafter referred to as "step IIIa"), and peeling off the cured product obtained by curing the resin composition from the mold (hereinafter referred to as "step IVa").

[0073] (Process Ia) Step Ia is a step of preparing a resin composition containing a thermosetting resin. For example, the resin composition may be prepared by mixing the thermosetting resin with an initiator, additives, etc., as needed. The type of thermosetting resin is not particularly limited and examples include bifunctional or trifunctional (meth)acrylates, bifunctional or trifunctional epoxy (meth)acrylates, bifunctional or trifunctional urethane (meth)acrylates, epoxy oligomers, oxetane oligomers, etc. The thermosetting resin may be one type or two or more types in combination.

[0074] (Step IIa) Step IIa is a step of applying the resin composition prepared in Step Ia onto a mold having an uneven shape. The method of applying the resin composition onto the mold is not particularly limited and includes known application methods such as spin coating, die coating, slit coating, inkjet printing, and dip coating.

[0075] (Step IIIa) Step IIIa is a step of curing the resin composition applied to the mold. In this step, the thermosetting resin contained in the resin composition may be heated to a curing temperature to thermally polymerize the thermosetting resin, or the thermosetting resin may be photopolymerized by irradiating the resin composition with ultraviolet light or the like. In this step, heating of the resin composition and irradiation of the resin composition with ultraviolet light may be combined.

[0076] The material of the mold having an uneven surface is not particularly limited, and examples include silicon, nickel, and resin. From the viewpoint of being able to form a fine structure, it is preferable to use a mold with an uneven surface that is made by lithography. The uneven surface can be freely selected by referring to known shapes, taking into consideration the adhesiveness and processability of the adhesive material.

[0077] (Process IVa) Step IVa is the step of curing the resin composition and peeling the cured product obtained from the mold. Since the shape of the mold transferred to the cured product is retained, the surface of the peeled-off cured product has the transferred shape of the mold, i.e., multiple protrusions. As a result, a cured product with multiple protrusions formed on one surface of the base is obtained as an adhesive member.

[0078] [Method for manufacturing adhesive material 2] The adhesive member manufacturing method 2 includes the steps of: preparing a substrate made of a thermoplastic resin (hereinafter referred to as "step Ib"); heating the substrate to a temperature above the softening point of the thermoplastic resin constituting the substrate (hereinafter referred to as "step IIb"); pressing a mold having an uneven shape onto the heated substrate and then cooling the substrate to a temperature below the softening point of the thermoplastic resin, preferably below the softening point (hereinafter referred to as "step IIIb"); peeling the cooled substrate from the mold (hereinafter referred to as "step IVb"); and crosslinking and curing the thermoplastic resin constituting the substrate having a plurality of protrusions (hereinafter referred to as "step Vb").

[0079] (Process Ib) Step Ib is a step of preparing a substrate made of a thermoplastic resin. In the adhesive member manufacturing method 2, the substrate made of a thermoplastic resin is the base and multiple protrusions of the adhesive member. The thermoplastic resin is not particularly limited as long as it is a resin that softens when heated, and any of the aforementioned resins that exhibit thermoplasticity may be used.

[0080] (Step IIb) Step IIb is a step of heating the substrate to a temperature above the softening point of the thermoplastic resin constituting the substrate. In step IIb, methods for heating the substrate include, for example, a method of heating the substrate by bringing it into contact with a high-temperature plate surface such as a hot plate, a method of heating the substrate by bringing it into contact with a temperature control roll, and a method of heating the feed-out substrate film by applying heat.

[0081] The softening point of a thermoplastic resin is measured using a thermomechanical analyzer (TMA-50, manufactured by Shimadzu Corporation). A thermoplastic resin substrate is cut into a 5mm wide x 15mm long specimen, and the temperature is increased from 10°C to 250°C at a rate of 5°C / min. The TMA softening temperature (softening point) is determined from the intersection of the tangents to the TMA curve around the glass transition temperature. The heating temperature of the substrate is not particularly limited as long as it is above the softening point of the thermoplastic resin contained in the substrate. If the temperature is too high above the softening point, the shrinkage rate of the thermoplastic resin will increase when the substrate is cooled in step IIIb, making it difficult to obtain good shape accuracy. For this reason, the heating temperature of the substrate is preferably below the softening point of the thermoplastic resin + 200°C, and more preferably below the softening point of the thermoplastic resin + 100°C.

[0082] (Step IIIb) Step IIIb is a step in which a mold having an uneven shape is pressed onto the substrate heated in step IIb, and then cooled to a temperature below the softening point of the thermoplastic resin, preferably below the softening point. In step IIIb, for example, a mold having an uneven shape is pressed onto a substrate made of thermoplastic resin that has been heated and softened in step IIb, and pressure is maintained for a certain period of time to transfer the shape (pattern) of the mold to the substrate, thereby forming an uneven shape on the substrate corresponding to the shape of the mold. Alternatively, in step IIIb, the softening of the thermoplastic resin and the transfer of the pattern can be performed simultaneously by using a temperature-controlled roll that holds the mold. After that, the softened thermoplastic resin is solidified by cooling the substrate and the mold to a temperature below the softening point.

[0083] The pressure (pressing pressure) applied when pressing a mold with an uneven shape onto a substrate is not particularly limited and can be set appropriately depending on the situation. The mold having an uneven shape may be heated in the same way as the substrate made of thermoplastic resin.

[0084] The cooling temperature of the substrate is not particularly limited, as long as it is below the softening point of the thermoplastic resin. From the viewpoint of moldability, the cooling temperature of the substrate is preferably 5°C or more lower than the softening point of the thermoplastic resin, more preferably 10°C or more lower than the softening point of the thermoplastic resin, and even more preferably room temperature.

[0085] The material of the mold having an uneven surface is not particularly limited, and examples include silicon, nickel, and resin. It is preferable that the mold having an uneven surface is manufactured by lithography, as this allows for the formation of fine structures. The uneven surface can be freely selected by referring to known shapes, taking into consideration the adhesiveness and processability of the adhesive material.

[0086] (Step IVb) Step IVb is the process of peeling the thermoplastic resin substrate, which was cooled in step IIIb, from the mold having an uneven shape. Since the shape of the mold transferred to the substrate, which is made of softened thermoplastic resin, is retained by the solidification of the thermoplastic resin due to cooling, the surface of the peeled substrate has the transferred shape of the mold, i.e., multiple protrusions.

[0087] In step IIIb, if the substrate and the mold are not cooled below the softening point of the thermoplastic resin, and in step IVb, the substrate is attempted to be peeled from the mold at a temperature close to the heating temperature, the peelability between the substrate and the mold will be insufficient, and the resin will deform easily, potentially damaging the transferred shape. On the other hand, by sufficiently cooling the substrate and the mold below the softening point of the thermoplastic resin before peeling, the shape of the mold is accurately transferred, dimensional stability is easily maintained, and deformation of convex parts due to movement fluctuations between the substrate and the mold during peeling is less likely to occur, ensuring excellent moldability.

[0088] (Process Vb) Step Vb is a step of crosslinking and curing the thermoplastic resin constituting the substrate having multiple protrusions obtained in step IVb. The method of crosslinking and curing is not particularly limited and can be carried out by known methods such as UV irradiation or heating. The wavelength and amount of UV irradiation, the temperature and heating time for heat curing, etc. can be appropriately set according to the initiator, crosslinking agent, etc. used. As a result, an adhesive member is obtained in which multiple protrusions are formed on one surface of the base.

[0089] Methods 1 and 2 for manufacturing adhesive members may include other steps as necessary, provided that they do not impair the effects of the present invention. These other steps are not particularly limited and can be appropriately selected depending on the purpose. For example, other processes include, if the adhesive material is in sheet form, a process of laminating a release film onto the adhesive material to prevent blocking during winding, and a process of laminating a support or the like to the side of the adhesive material that has multiple protrusions or the opposite side thereof.

[0090] The protrusions having a specific shape, such as a mushroom shape or an inverted taper, may be formed in two stages. In this case, a known method for forming a tower top structure having a specific shape, such as a mushroom shape or an inverted taper, at the tip of the protrusion may be employed. For example, a thin film of resin composition may be formed on a support using a known coating method, the protrusions of the cured material may be bonded to the formed resin composition thin film, and then the cured material may be slowly peeled off the resin composition thin film from the support. Next, the cured material may be placed on a new support so that the tip of the protrusion of the cured material is in contact with the support, and then the resin composition on the tip side of the protrusion may be cured by heat curing, ultraviolet irradiation, etc., to form a tower top structure having a specific shape, such as a mushroom shape or an inverted taper, at the tip of the protrusion. When forming the protrusion in two stages, the resin composition used to form the cured product and the resin composition used to form a mushroom shape, reverse taper, or other structure at the tip of the protrusion may be the same or different, as long as the tensile strength and swelling rate satisfy the aforementioned numerical ranges. Using the same resin composition is preferable from the viewpoint of suppressing interfacial fracture within the protrusion, but is not limited to this.

[0091] The surface layer may be bonded to the tips of multiple protrusions so as to cover the multiple protrusions of the adhesive member. The bonding temperature of the multiple protrusions and the surface layer can be appropriately set according to the thermal properties of the materials constituting these members (e.g., resin materials). For example, an adhesive member with a surface layer may be manufactured by pressing the multiple protrusions and the surface layer with a roll, press sheet, etc., at a temperature 10°C to 100°C higher than the glass transition temperature of the resin material constituting the protrusions or the resin material constituting the surface layer. The material of the roll and press sheet is not particularly limited, and commonly used metals and rubbers can be appropriately selected and used according to the bonding conditions. The following describes an example of a method for manufacturing the surface layer.

[0092] (Method for manufacturing the surface layer) The surface layer is manufactured by a known method. As an example, the method for manufacturing the surface layer includes the steps of preparing a liquid resin (hereinafter referred to as "step i"), applying the obtained liquid resin to a desired thickness (hereinafter referred to as "step ii"), and drying the applied liquid resin (hereinafter referred to as "step iii"). Processes i, ii, and iii will be explained below.

[0093] (Process i) Step i is a step of preparing a liquid resin. In step i, for example, the liquid resin may be prepared by dissolving the thermoplastic resin in a known solvent suitable for thermoplastic resins. When obtaining a liquid resin by dissolving the thermoplastic resin in a solvent in step i, the process may be carried out at room temperature or under heating, depending on the solubility of the thermoplastic resin. If a liquid thermosetting resin that has not yet hardened is used, this step can be omitted. Examples of liquid resins include resin solutions containing resin and liquid resins.

[0094] (Step ii) Step II is the step of applying the obtained liquid resin to a desired thickness. In step II, the obtained liquid resin can be applied to a suitable substrate. The method of applying the liquid resin is not particularly limited, and known application methods such as spin coating, die coating, slit coating, inkjet printing, and dip coating can be used.

[0095] (Step iii) Step iii is a step of drying the applied liquid resin. In this step, the liquid resin may be heated for curing as needed, or it may be left at room temperature. Known heating methods include blow-air dryers, etc. Step iii can be carried out in a desired environment such as an air atmosphere or a nitrogen atmosphere. [Examples]

[0096] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the spirit of the invention.

[0097] [Example 1] [Preparation of resin composition] 100 parts by mass of bifunctional urethane acrylate (UA5216, manufactured by MIWON) and 4 parts by mass of photopolymerization initiator (Omnirad 184, manufactured by IGM Resins) were added to a 50 mL poly bottle. The mixture was stirred for 10 minutes using a resin spatula to obtain a resin composition.

[0098] [Preparation of adhesive materials] (1) Fabrication of cylindrical pattern shaped member A nickel mold measuring 100 mm in length and 100 mm in width was prepared, with multiple recessed shapes formed therein (recess shape: cylindrical, recess depth: 40 μm, recess entrance width: 20 μm, recess bottom width: 20 μm, distance between recess centers: 40 μm). The aforementioned resin composition was applied to the nickel mold using a tabletop coater to form a resin composition layer with a thickness of 150 μm. A cumulative dose of 5000 mJ / cm³ was applied to a resin composition layer formed using a UV irradiation device (UVC-408, manufactured by Technovision Co., Ltd.).2 The resin composition layer was cured by performing exposure twice. The cured product was slowly peeled off from the nickel mold to obtain an adhesive member. The obtained member was shaped with a fine uneven pattern corresponding to the concave shape of the nickel mold. Specifically, the adhesive member was a cured product (cylindrical pattern-shaped member) in which cylinders with a convex portion height of 40 μm, a diameter of the base portion and the tip portion of the convex portion of 20 μm, and a center-to-center distance of the convex portions of 40 μm were regularly arranged.

[0099] (2) Production of an adhesive member with mushroom-shaped unevenness Subsequently, the above resin composition was applied onto a glass plate using a separate tabletop coater to form a resin composition layer with a thickness of 5 μm. On this resin composition layer, the above cylindrical pattern-shaped member was gently placed with the convex portion facing downwards, and they were bonded together with a rubber roller at a load of 0.5 kg and a speed of 10 cm / second. After standing for 1 minute, the cylindrical pattern-shaped member was peeled off, and it was left standing for 5 minutes on a separately prepared quartz glass plate such that the tip side of the convex portion was in contact with the quartz glass. Exposure with an integrated amount of 5000 mJ / cm was performed twice on the resin composition layer formed using a UV irradiation device (UVC-408, manufactured by Technovision Co., Ltd.) to cure the resin composition layer. As a result, an adhesive member with mushroom-shaped unevenness was produced. 2 The adhesive member with mushroom-shaped unevenness had a convex portion height of 40 μm, a base portion of the convex portion of 20 μm, a diameter of the tip portion of the convex portion of 22 μm, and a center-to-center distance of the convex portions of 40 μm, and had a mushroom shape as shown in Fig. 2.

[0100] 〔Measurement of swelling ratio〕 The swelling ratio of the cured product of the resin composition prepared in Example 1 was evaluated as follows. First, exposure with an integrated amount of 5000 mJ / cm was performed on the resin composition using a UV irradiation device (UVC-408, manufactured by Technovision Co., Ltd.). 2The resin composition was cured by two exposures. The mass A of the resulting cured product was measured. Next, the cured product was immersed in toluene at 25°C for 24 hours. After the product had expanded, it was removed, the toluene on the surface was wiped off using filter paper, and the mass B of the cured product after immersion was measured. The swelling rate was determined based on the following formula (1). Swelling rate [%] = (B / A) × 100 ... (1) In equation (1), A is the mass of the hardened product before immersion in toluene, and B is the mass of the hardened product after immersion in toluene. The results are shown in Table 1.

[0101] [Measurement of breaking strength and breaking elongation] The resin composition prepared in Example 1 was cured under the same conditions as the swelling rate measurement described above to obtain a cured product with a thickness of 500 μm. The obtained cured product was pulled at a speed of 100 mm / min in accordance with ASTM D882 using a Tensilon universal material tester RTF (manufactured by Kitahama Seisakusho), and the strength (tensile load value divided by the cross-sectional area of ​​the cured product) and elongation at the time of fracture were determined. The determined values ​​were defined as the fracture strength (MPa) and fracture elongation (%). The results are shown in Table 1.

[0102] [Glass transition temperature Tg (°C) of the cured product] The glass transition temperature (Tg) of the cured product was measured under an N2 (nitrogen) atmosphere using a Shimadzu Science DSC-6220. 5 mg or 10 mg of the cured product prepared in Example 1 was cured under the same conditions as described above for measuring the swelling rate, and sealed in an aluminum pan. The temperature was raised from room temperature to 200°C at a rate of 10°C / min, held for 5 minutes, and then cooled to -20°C at a rate of 10°C / min, held for 5 minutes. The glass transition temperature (Tg) of the cured product was then determined from the endothermic curve obtained when the temperature was raised to 200°C at a rate of 10°C / min. The results are shown in Table 1.

[0103] [Evaluation of excipient properties] The surface of the adhesive material, obtained by peeling it from a nickel mold, with its finely textured surface, was observed using an optical microscope at magnifications ranging from 100x to 500x. The observation magnification was set so that the total number of protrusions within the observation field was 500 or more, and the total number of protrusions N within the observation field at the set magnification was measured. Next, the number of defective locations n where protrusions were missing within the observation field was calculated. The defect rate was determined based on the following equation (2). Defect rate = (n / N) × 100 ... (2) Furthermore, the moldability was evaluated based on the following evaluation criteria. The results are shown in Table 1. - Criteria for evaluating excipient properties - A: The defect rate was between 0% and less than 0.1%. B: The defect rate was 0.1% or higher.

[0104] [Evaluation of adhesiveness] The adhesive material was cut to a width of 25 mm and a length of 10 cm. At 23°C, it was attached to a SUS304-BA plate (JIS G-4305 specification, length: 20 cm, width: 5 cm) using a 2000 g roller, without applying a load greater than the roller's load, via the side with the fine uneven pattern. It was left to stand for 1 hour. After standing, one end of the adhesive material was held, and the adhesive material was peeled off the surface of the SUS304-BA plate under the conditions of peeling angle: 180 degrees and peeling speed: 300 mm / min. The stress at the time of peeling was measured and converted to N / 25 mm to determine the adhesive strength. All other conditions conformed to JIS Z-0237 (2009). Adhesion was evaluated based on the following criteria. The results are shown in Table 1. -Evaluation Criteria for Adhesion- A: The adhesive strength was 1.0 N / 25 mm or higher. B: The adhesive strength was between 0.20 N / 25 mm and less than 1.0 N / 25 mm. C: The adhesive strength was less than 0.20 N / 25 mm.

[0105] [Evaluation of contamination after removal of adhesive material] Following the adhesive strength measurement described above, the entire area of ​​the SUS304-BA plate where the adhesive material was attached and then peeled off was observed using an optical microscope. The contamination after peeling off the adhesive material was evaluated based on the following evaluation criteria. The results are shown in Table 1. -Evaluation criteria for contamination after removal of adhesive material- A: No residual material with a width of 1 μm or more, originating from the adhesive material, was found. B: Residual material with a width of 1 μm or more, originating from the adhesive material, was found.

[0106] [Examples 2-6] The same procedure as in Example 1 was followed, except that instead of the resin composition obtained in Example 1, a resin composition was obtained by mixing 100 parts by mass of the compound shown in Table 1 and 4 parts by mass of a photopolymerization initiator (Omnirad 184, manufactured by IGM Resins). Table 1 shows the evaluation results for the cured products and adhesive members obtained in Examples 2 to 6. The details of the compounds used in each example are as follows. - Compounds used in each example - Example 2: Bifunctional urethane acrylate (E207 / 30PE, manufactured by MIWON) Example 3: Tricyclodecane-modified difunctional acrylate (SR833S, manufactured by Sartomer) Example 4: Bifunctional urethane acrylate (KRM7735, manufactured by Daicel Ornex Co., Ltd.) Example 5: Bifunctional epoxy acrylate (Viscote #540, Osaka Organic Chemical Industry Co., Ltd.) Example 6: Bifunctional epoxy acrylate (EBECRYL3500, manufactured by Daicel Ornex Co., Ltd.)

[0107] [Comparative Examples 1-3] The same procedure as in Example 1 was followed, except that instead of the resin composition obtained in Example 1, a resin composition was obtained by mixing 100 parts by mass of the compound shown in Table 1 and 4 parts by mass of a photopolymerization initiator (Omnirad 184, manufactured by IGM Resins). Table 1 shows the evaluation results for the cured products and adhesive members obtained in Comparative Examples 1 to 3. The details of the compounds used in each comparative example are as follows. - Compounds used in each comparative example - Comparative Example 1: Tetrafunctional Urethane Acrylate (EBECRYL4666, manufactured by Daicel Ornex Corporation) Comparative Example 2: Bifunctional Urethane Acrylate (EBECRYL4491, manufactured by Daicel Ornex Corporation) Comparative Example 3: Bifunctional Acrylate (RA-341, manufactured by Negami Kogyo Co., Ltd.)

[0108] [Comparative Example 4] In Comparative Example 4, an ethylene-α-olefin copolymer (Tafmer A4085S, manufactured by Mitsui Chemicals, Inc.) was prepared instead of the resin composition obtained in Example 1. Furthermore, in Comparative Example 4, cured products and adhesive members were prepared by electron beam crosslinking without using a photopolymerization initiator, and each was evaluated. Table 1 shows the evaluation results for the cured product and adhesive member obtained in Comparative Example 4.

[0109] [Table 1]

[0110] As shown in Table 1, each embodiment was evaluated favorably in terms of formability, tackiness, and staining properties. On the other hand, each comparative example was evaluated poorly in either tackiness or staining properties, and in Comparative Example 3, the formability evaluation was poor. [Explanation of symbols]

[0111] 1 Base, 2 Protrusion, 3 Tip, 4, 6 Surface layer, 5 Space, 7 Surface processed part, 10, 20, 30 Adhesive member

Claims

1. A substrate having multiple protrusions on at least one surface, The aforementioned protrusion is an adhesive member having a breaking strength of 20 MPa to 48 MPa and a swelling rate of 110% to 140% after immersion in toluene at 25°C for 24 hours.

2. The adhesive member according to claim 1, wherein the width of the tip portion of the protrusion is greater than the width of the base portion.

3. The substrate comprises a surface layer that is arranged across the tips of at least two of the protrusions formed on one surface of the substrate and covers at least a portion of the surface of the substrate having the plurality of protrusions, The adhesive member according to claim 1 or claim 2, wherein a space exists between the bottom surface on which the plurality of protrusions are formed and the surface of the surface layer facing the bottom surface.

4. The adhesive member according to claim 3, wherein the thickness of the surface layer is 0.1 μm to 50 μm.

5. The adhesive member according to claim 1 or claim 2, wherein the width of the base of the protrusion is 5 nm to 250 μm.

6. The adhesive member according to claim 1 or claim 2, wherein the ratio of the width of the tip of the protrusion to the width of the base of the protrusion is 1.0 to 1.

4.

7. The adhesive member according to claim 1 or claim 2, wherein the distance between the protrusions is 10 nm to 500 μm.

8. The adhesive member according to claim 1 or claim 2, wherein the height of the protrusion is 2.5 nm to 500 μm.

9. The adhesive member according to claim 1 or claim 2, wherein the ratio of the height of the protrusion to the width of the base of the protrusion is 0.2 to 10.

0.

10. The adhesive member according to claim 1 or claim 2, wherein the protrusion is made of a resin material having a structure formed by polymerizing at least one selected from the group consisting of (meth)acrylate compounds, urethane (meth)acrylate compounds, epoxy (meth)acrylate compounds, and olefin compounds.

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