WO2021124080A1

WO2021124080A1 - Adhesive sheet, panel product, sheet product, and cable product

Info

Publication number: WO2021124080A1
Application number: PCT/IB2020/061910
Authority: WO
Inventors: Yoshinao Yamazaki; Haruyuki Mikami; Ikuse NOMOTO; Kaori Ozawa; Kenji WAKAMATSU; Rina Takahashi
Original assignee: 3M Innovative Properties Company
Priority date: 2019-12-18
Filing date: 2020-12-14
Publication date: 2021-06-24
Also published as: JP2021095511A

Abstract

An adhesive sheet includes an adhesive layer including a fine structure on a front surface of the adhesive layer. The fine structure includes a plurality of convex structures. Each of the convex structures includes two or more parts. The first part present at the top of the convex structure includes a first adhesive material. The second part present below the first part includes a second adhesive material having higher adhesiveness than the first adhesive material. When a test is conducted in accordance with JIS K 7125 except that a metal sliding piece is pulled at a speed of 1000 mm/min., a coefficient of static friction is 10 or more.

Description

ADHESIVE SHEET, PANEL PRODUCT, SHEET PRODUCT, AND CABLE

PRODUCT

Technical Field

The present disclosure relates to an adhesive sheet, a panel product, a sheet product, and a cable product.

Background

U.S. Patent No. 5,141, 790 discloses a releasable adhesive tape including a plurality of protrusions formed on a surface of an adhesive layer. A group of particles not containing a pressure sensitive adhesive is disposed at the top of the protrusions.

JP 6042580 B discloses a pressure-adhesive type adhesive member including a plurality of protrusions disposed at intervals on a main surface of an adhesive layer. A frictional force applied to a stainless steel plate by the pressure-sensitive adhesion type adhesive member when the protrusions are in contact with an adherend surface is approximately 0.4 N/cm² or less.

JP 2003-96415 A discloses an adhesive tape including two types of adhesive layers varied in adhesive force.

Summary Technical Problem

The adhesive sheets in U.S. Patent No. 5,141, 790, JP 6042580 B, and JP 2003- 96415 A are not provided with a protrusion made from a plurality of portions including different adhesive materials.

The present disclosure provides an adhesive sheet, a panel product, a sheet product, and a cable product that can be temporarily joined to a subject at low pressures and can be strongly attached to the subject at high pressures.

Solution to Problem

An adhesive sheet according to an aspect of the present disclosure is an adhesive sheet including an adhesive layer including a fine structure on a front surface of the adhesive layer, wherein the fine structure includes a plurality of convex structures, each of the plurality of convex structures includes two or more parts, a first part present at a top of the convex structure includes a first adhesive material, a second part present below the first part includes a second adhesive material having higher adhesiveness than the first adhesive material, and when a test is conducted in accordance with JIS K 7125 except that a metal sliding piece is pulled at a speed of 1000 mm/min., a coefficient of static friction is 10 or more.

When a test is conducted in accordance with JIS Z 1541 except that a roller has a mass of 100 g and that a left standing time after compression bonding is 1 minute, a 90° peeling adhesive force is 0.5 N/cm or more and 5 N/cm or less.

The above-described two or more parts may be joined together via an interface.

Assuming that a height of the convex structure is 100%, a height of the first part may be in a range from 10% to 90% of the height of the convex structure.

An angle Q formed between a side surface and a bottom surface of the convex structure may be 5° or more.

A height of the convex structure may be 5 pm or more.

A panel product according to the present disclosure includes the adhesive sheet described above and a panel provided on a surface opposite to the front surface of the adhesive layer of the adhesive sheet.

A sheet product according to the present disclosure includes the adhesive sheet described above, and a sheet member provided on a surface of the adhesive sheet opposite the front surface of the adhesive layer.

A cable product according to the present disclosure includes a cable and the adhesive sheet provided on at least a portion of an outer circumferential surface of the cable, wherein a surface opposite to the front surface of the adhesive layer of the adhesive sheet faces at least the portion of the outer circumferential surface of the cable.

Advantageous Effects of Invention

According to the present disclosure, an adhesive sheet, a panel product, a sheet product, and a cable product may be provided that can be temporarily joined to a subject at low pressures and are strongly attached to the subject at high pressures.

Brief Description of the Drawings

FIG. l is a perspective view of an adhesive sheet according to an embodiment.

FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. FIG. 3 is a cross-sectional view of an adhesive sheet according to another embodiment.

FIG. 4 is a cross-sectional view of an adhesive sheet according to another embodiment.

FIG. 5 is a partial cross-sectional view of an adhesive sheet according to another embodiment.

FIG. 6 is a cross-sectional view illustrating other examples of a cone structure.

FIG. 7 is a cross-sectional view illustrating other examples of a frustum structure.

FIG. 8 is a perspective view of an adhesive sheet according to another embodiment.

FIG. 9 is a cross-sectional view illustrating a step in a method for manufacturing the adhesive sheet of FIG. 3.

FIG. 10 is a cross-sectional view illustrating a step following the step of FIG. 9.

FIG. 11 is a cross-sectional view illustrating a step following the step of FIG. 10.

FIG. 12 is a cross-sectional view illustrating a step of applying the adhesive sheet of FIG. 3 to a subject.

FIG. 13 is a cross-sectional view illustrating a panel product according to an embodiment and a subject to which the panel product is to be applied.

FIG. 14 is a cross-sectional view illustrating a sheet product according to an embodiment and a subject to which the sheet product is to be applied.

FIG. 15 is a cross-sectional view illustrating a cable product according to an embodiment and a subject to which the cable product is to be applied.

Detailed Description

Detailed description of embodiments are given below with reference to the attached drawings. In the description of the drawings, the same or equivalent elements are denoted by the same reference signs, and redundant description of such elements will be omitted. The XYZ rectangular coordinate system is illustrated in the drawings as necessary.

FIG. l is a perspective view of an adhesive sheet according to an embodiment. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. An adhesive sheet 10 illustrated in FIGS. 1 and 2 includes an adhesive layer 12. In the present embodiment, the adhesive layer 12 includes a fine structure 13 on a front surface 12a and no fine structure on a back surface 12b opposite to the front surface 12a. The front surface 12a and the back surface 12b extend along a plane (e.g., an XY plane) orthogonal to a thickness direction (e.g., Z-axis direction) of the adhesive layer 12. The fine structure 13 includes a plurality of cone structures 31. The cone structure 31 may be replaced with a frustum structure 131 (FIG. 5) or a rib structure 231 (FIG. 8) described below. The cone structure 31, the frustum structure 131, and the rib structure 231 are each an example of a convex structure (convex part). Herein, the “convex structure” generally refers to a solid figure that includes any plane figure as a bottom surface, and that is constructed by connecting all points in a side of the bottom surface and all points in a side of any other plane figure or a line (top) that is not on the bottom surface. Preferably, the area of the top of the convex structure is smaller than the area of the bottom surface. More preferably, the convex structure is shaped to be tapered from the bottom surface toward the top. The plurality of cone structures 31 are arrayed along the X-axis direction and the Y-axis direction to form a lattice shape in the front surface 12a. FIG. 2 is a cross-sectional view through apices of the plurality of cone structures 31 arrayed along the X-axis direction. The plurality of cone structures 31 can preferably be regularly arrayed or randomly arrayed on a plane. The area of each of the cone structures 31 projected to the plane orthogonal to the height direction of the cone structure 31 (area of a bottom surface 1 of the cone structure 31) may be 10 square micrometers or more and may be 10000 square micrometers or less.

Each cone structure 31 has the bottom surface 1, a top 2, and a plurality of side surfaces 3 connecting edges of the bottom surface 1 and the top 2. The bottom surface 1 has any plane figure such as a circle (including an ellipse) or a polygon. Examples of a shape of the cone structure 31 include a cone, a triangular pyramid, a quadrangular pyramid, and a hexagonal pyramid. In the example illustrated in FIGS. 1 and 2, the shape of the cone structure 31 is a quadrangular pyramid. The cone structures 31 may have the same shape or different shapes, but preferably have substantially the same height (with a difference within ±5%, ±3%, or ±1%) and more preferably all have substantially the same shape. In a case where the cone structures 31 have different shapes, the fine structure 13 preferably includes 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, or 2 or less types of cone structures 31. Two or more of the cone structure 31, the frustum structure 131 (FIG. 5) and the rib structure 231 (FIG. 8) may coexist. Each cone structure 31 includes a first part 4 present at the top 2 of the cone structure 31 and a second part 5 present in a lower side (the bottom surface 1 side) of the first part 4.

The top 2 is a part substantially occupying a region located at the highest position of the cone structure 31 (a part of the cone structure 31 that initially comes into contact with a subject when the adhesive sheet of the present disclosure approaches the subject) The top 2 preferably includes the apex of the cone structure 31. The “substantially occupying” means that the case where a different material is attached to or incorporated in only a part is also acceptable. For example, the first part 4 may occupy a majority (e.g., 90% or more, or 95% or more) of the region located at the highest position of the cone structure 31. Even when a small amount of a filler or the like is incorporated in the region, the filler or the like does not correspond to the first part 4. The first part 4 contacts the subject when the pressure applied to the adhesive sheet 10 is low, resulting in low adhesiveness. When high pressure is applied to the adhesive sheet 10, the second part 5 itself is deformed, the first part 4 is deformed, or the first part 4 is incorporated into the second part 5 to bring the second part 5 into contact with the subject, leading to high adhesiveness.

The first part 4 and the second part 5 can be joined to each other via an interface along an XY plane for example. The being “joined via an interface” means a state where two matrix phases having different kinds of composition are in contact via a distinct interface. For example, the first part 4 (matrix phase) and the second part 5 (matrix phase) are layered and separated as illustrated in FIGS. 1 and 2 and thus are joined via the interface. Note that for example, in the case of a composition in which fine particles are dispersed in a resin, the resin serving as a substrate corresponds to the matrix phase, while the fine particles correspond to a dispersed phase. The being joined via an interface does not include joining of two phases including a common matrix phase and different dispersed phases, or a joining manner in which a material varies continuously, for example, in a material in which fine particles are dispersed in a resin, only density of the fine particles continuously varies in a direction. The interface may be a plane parallel or not parallel to the bottom surface 1 of the cone structure 31. The interface may include a surface curved due to, for example, a manufacturing error or surface tension in a manufacturing method described below. The cone structure 31 may optionally further include a third part, or may have a multilayer structure including three or more layers.

The first part 4 is made from a first adhesive material. As the first adhesive material, a material is preferable that has adhesion to a subject but that can be easily re peeled from the subject. Note that “re-peeling” means that the adhesive attached to the subject can be peeled off with little glue remaining. In one embodiment, a first adhesive material is a pressure sensitive adhesive having a storage elastic modulus (G¹) of 3 ^c 10⁵ Pa or less calculated by dynamic viscoelasticity measurement at 25°C or lower and at a frequency of 1 Hz. Specific examples of the first adhesive material include an acrylic- based adhesive, a rubber-based adhesive, a silicone-based adhesive, a urethane-based adhesive, a polyester-based adhesives, a polyolefin-based adhesive, and an adhesive obtained by blending any of these adhesives together. The first adhesive material preferably has high solubility and/or dispersibility in any general purpose solvent of a water miscible solvent such as water and alcohol, or a water immiscible solvent such as hydrocarbon. Additionally, a solvent in which the first adhesive material dissolves and/or disperses preferably has a relatively low vapor pressure and is easy to dry. Further, wettability to a mold for forming the fine structure 13 is preferably also considered. When the wettability is too low, the solvent may not enter an inside of a recess of the mold, and when the wettability is too high, the solvent may remain inside the recess of the mold.

The second part 5 is made from a second adhesive material having higher adhesiveness than the first adhesive material. Particularly, a material exhibiting a relatively strong adhesive force to a subject, and being not easily peeled again is preferable for the second adhesive material. In one embodiment, the second adhesive material is a pressure sensitive adhesive having a storage elastic modulus (G) of 3 ^c 10⁵ Pa or less calculated by dynamic viscous elasticity measurement at 25°C and at a frequency of 1 Hz. Specific examples of the first adhesive material include an acrylic-based adhesive, a rubber-based adhesive, a silicone-based adhesive, a urethane-based adhesive, a polyester- based adhesives, a polyolefin-based adhesive, and an adhesive obtained by blending any of these adhesives together. The second adhesive material may be blended with a tackifier.

Both the first adhesive material and the second adhesive material preferably have a certain hardness or higher to allow the fine structure 13 to be maintained. For example, a material having a tan d of 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, or 0.3 or less as measured at normal temperature and a frequency of 1 Hz is preferable.

Note that “adhesiveness” means the relative strength of an adhesive force to the same subject. Adhesiveness can be evaluated by a known technique such as dynamic viscoelasticity measurement or a 180° peeling strength test.

A combination of the material of the first part 4 and the material of the second part 5 is not limited, but the materials are more preferably selected in consideration of adhesive force between the first part 4 and the second part 5. For example, in terms of affinity of a polymer structure and the like, when the material of the first part 4 is silicone, the material of the second part 5 is also preferably a silicone-based adhesive. However, the first part 4 and the second part 5 are not necessarily polymers having the same structure.

The adhesive layer 12 may include a base 32 below the plurality of cone structures 31. The base 32 is joined or continuous with the bottom surfaces 1 of the cone structures 31 of the fine structure 13. A material of the base 32 may be the same as or different from the material of the second part 5. In an embodiment, the cone structure 31 includes two parts that are the first part 4 and the second part 5, and the base 32 is made from the same material as the material of the second part 5, and continuous with the second part 5. The thickness (height H3) of the base 32 can arbitrarily be set according to a desired thickness of the adhesive layer 12. In a case where the material of the base 32 is elastic, the cone structures 31 in the fine structure 13 can sink into the base 32, and thus the second parts 5 of the cone structures 31 comes into easier contact with the subject, improving the adhesiveness of the adhesive sheet 10.

When the first adhesive material constituting the first part 4, the second adhesive material constituting the second part 5, and a material constituting another part, if any, are all transparent, the adhesive layer 12 can entirely be made transparent. At that time, to make the interface via which the parts are joined invisible, a difference in a refractive index among the materials constituting these parts is preferably within 1%. Specifically, when the first part 4 and the second part 5 of the cone structure 31 are adjacent to each other and the difference between the refractive index of the material constituting the first part 4 and the refractive index of the material constituting the second part 5 is within 1%, within 0.9%, within 0.8%, within 0.7%, or within 0.6%, the interface between the two parts is generally invisible. For example, when the first part 4 and the second part 5 include a transparent acrylic adhesive, the above-described requirements can be satisfied, and the adhesive layer 12 completely transparent can be provided. Note that transparent can be defined by, for example, haze of 40% or less as measured in accordance with JIS K 7136.

In terms of facilitation of formation of the first part 4, and the like, for the cone structures 31 included in the fine structure 13, the longest distance between the centers of two cone structures 31 adjacent to each other may be 300 pm or less, 260 pm or less, 220 pm or less, 180 pm or less, 140 pm or less, or 100 pm or less. Note that the center of the cone structure 31 means an apex of a cone. The center of the frustum structure 131 (FIG.

5) means an apex of a corresponding cone structure.

The bottom surfaces 1 of two cone structures 31 adjacent to each other may be close to each other. For example, in the case of a quadrangular pyramid or a hexagonal pyramid, the bottom surfaces 1 of two cone structures 31 adjacent to each other may share one side, or adjacent sides may be separate at an interval b (FIG. 5) of, for example, 250 pm or less, 200 pm or less, 150 pm or less, 100 pm or less, 50 pm or less, 15 pm or less, or 10 pm or less.

A pitch a of the cone structures 31 adjacent to each other (the pitch in the case of FIG. 5 is a + b) may be 10 pm or more, 15 pm or more, or 20 pm or more, and 200 pm or less, 150 pm or less, or 100 pm or less.

In terms of facilitation of formation of the first part 4 and the like, a width a of the bottom surface 1 of the cone structure 31 in an array direction (the X-axis direction, for example) of the cone structures 31 may be 500 pm or less, 450 pm or less, 400 pm or less, 350 pm or less, 300 pm or less, 250 pm or less, 200 pm or less, 150 pm or less, 100 pm or less, 95 pm or less, 90 pm or less, 85 pm or less, 80 pm or less, 75 pm or less, 70 pm or less, 65 pm or less, 60 pm or less, 55 pm or less, or 50 pm or less. In the array direction of the cone structures 31 (e.g., the X-axis direction), a width al of the bottom surface of the first part 4 is smaller than the width a of the bottom surface 1 of the cone structure 31.

In terms of facilitation of manufacture of the adhesive sheet 10, facilitation of peel of the liner 71 (see FIG. 11) from the adhesive sheet 10 completed, or the like, a height H of the cone structure 31 may be 100 pm or less, 95 pm or less, 90 pm or less, 85 pm or less, 80 pm or less, 75 pm or less, 70 pm or less, 65 pm or less, 60 pm or less, 55 pm or less, or 50 pm or less. The height H of the cone structure 31 may be 5 mih or more, 10 mih or more, or 25 mih or more. In a case where the height H of the cone structure 31 is 100%, a height HI of the first part 4 may be 10% or more, 15% or more, or 20% or more of the height H of the cone structure 31 in terms of re-peelability and the like. The height HI may be 90% or less, 80% or less, 70% or less, 60% or less, or 50% or less in terms of adhesiveness and the like. A height H2 of the second part 5 corresponds to the difference between the height H of the cone structure 31 and the height HI of the first part 4. Note that the heights H,

HI, and H2 are based on the normal direction (the Z-axis direction) of the bottom surface 1 of the cone structure 31. When the interface between the first part 4 and the second part 5 located below the first part 4 is a plane or a curved surface that is not parallel to the bottom surface 1, the height HI is calculated from an average value of the heights of the interface determined based on the normal direction of the bottom surface 1. A relatively small size of the first part 4 tends to reduce the re-peelability of the adhesive sheet 10 obtained when low pressure is applied and to improve the adhesive force of the adhesive sheet 10 exhibited when high pressure is applied. On the other hand, when the first part 4 is relatively large, the opposite is true.

The thickness of the adhesive layer 12 (H + H3) can arbitrarily be set according to the adhesive material used, the intended use of the adhesive sheet 10, or the like, and can be, for example, in the range from 15 pm to 10 mm or 200 pm to 4 mm. The thickness of the adhesive layer 12 means the distance between the highest part of the cone structure 31 and the back surface 12b opposite to the front surface 12a with the fine structure 13, based on the normal direction of the bottom surface 1 of the cone structure 31.

In terms of facilitation of formation of the first part 4, re-peelability, or the like, an angle Q formed between a side surface 3 and the bottom surface 1 of the cone structure 31 can be 5° or more, 10° or more, 15° or more, 20° or more, or 25° or more in a cross section (XZ plane) including the apices of the cone structures 31 and the array direction of the cone structures 31. Additionally, in terms of smoothly peeling the adhesive sheet 10 from the liner 71 described below, the angle Q may be less than 90°, 85° or less, 80° or less, or 70° or less in the cross section (XZ plane) including the apices of the cone structures 31 and the array direction of the cone structures 31.

In view of sufficient re-peelability, the number of cone structures 31 is preferably 16 or more, 25 or more, 36 or more, 49 or more, 64 or more, 81 or more, or 100 or more per mm² of the front surface of the adhesive layer 12. The number of the cone structures 31 corresponds to the number of the centers of the cone structures 31 present in the unit area. High density of the cone structures 31 also contributes to improvement of re- peelability.

The adhesive layer 12 may include an additional material other than an adhesive, for example, fine particles such as hollow or solid glass spheres for the purpose of adjusting adhesiveness. However, the adhesive sheet 10 of the present disclosure can achieve desired properties without including such additional materials. In an embodiment, the adhesive layer 12 includes no fine particle.

Characteristics of adhesive sheet

The adhesive sheet 10 exhibits a low adhesive force to a subject when low pressure is applied to the back surface 12b of the adhesive layer 12. In one embodiment, the “low pressure” can be defined as pressure of 100 g/cm² or less, 50 g/cm² or less, 10 g/cm² or less, or 5 g/cm² or less. In another embodiment, the “low pressure” can be defined as pressure corresponding to pressure generated by reciprocating a roller of 100 g at a speed of 300 mm/min. by using a compression bonding apparatus defined in JIS K 7125.

In one embodiment, when a test is conducted in accordance with JIS K 7125 except that a metal sliding piece such as steel material (e.g., SS400 material that may include plating such as chrome plating) is pulled at a speed of 1000 mm/min., the adhesive sheet 10 (the front surface 12a of the adhesive layer 12) preferably has a coefficient of static friction of 10 or more, 20 or more, 30 or more, 40 or more, or 50 or more. A large coefficient of static friction makes the adhesive sheet 10 less likely to be displaced when the adhesive sheet 10 is pressed against the subject at low pressure. Thus, the adhesive sheet 10 can be temporarily joined to the subject.

In one embodiment, when a test is conducted in accordance with JIS Z 1541 except that the roller has a mass of 100 g and that the left standing time after the compression bonding is 1 minute, the adhesive sheet 10 (the front surface 12a of the adhesive layer 12) has a 90° peeling adhesive force (hereinafter, also referred to as “initial adhesive force”) of 0.5 N/cm or more or 1.0 N/cm or more. A high initial adhesive force improves the adhesiveness of the adhesive sheet 10. The initial adhesive force may be 5 N/cm or less or 4 N/cm or less. A low initial adhesive force improves the re-peelability of the adhesive sheet 10. The adhesive sheet 10 exhibits a high adhesive force to the subject when high pressure is applied to the back surface 12b of the adhesive layer 12. In an embodiment, the “high pressure” can be defined as pressure corresponding to pressure generated by reciprocating a roller of 2 kg at a speed of 300 mm/min. by using a compression bonding apparatus defined in 10.2.4 of JIS Z 0237: 2009. In another embodiment, the “high pressure” can be defined as pressure corresponding to pressure generated by reciprocating a roller of 5 kg at a speed of 300 mm/min. by using a compression bonding apparatus defined in JIS Z 1541. In yet another embodiment, the “high pressure” can be defined as pressure of 200 g/cm² or more, 300 g/cm² or more, 400 g/cm² or more, 500 g/cm² or more, 600 g/cm² or more, or 700 g/cm² or more. In a preferred embodiment, when the adhesive sheet 10 is tested on an SUS plate at a temperature of 23°C and a tensile speed of 300 mm/min., the adhesive sheet 10 has a 90° peeling adhesive force of 2 N/10 mm or more, 4 N/10 mm or more, 6 N/10 mm or more, 8 N/10 mm or more, or 10 N/10 mm or more at 24 hours after the adhesion. Such an adhesive force makes peel-off less likely to occur after the adhesive sheet 10 is applied to the subject at high pressure.

As described above, when the adhesive sheet 10 is pressed against the subject at low pressure with the front surface 12a of the adhesive layer 12 with the fine structure 13 facing the subject, the first part 4 is bonded to the subject. This allows the adhesive sheet 10 to be temporarily joined to the subject. On the other hand, when the adhesive sheet 10 is pressed against the subject at high pressure with the front surface 12a of the adhesive layer 12 with the fine structure 13 facing the subject, the second part 5 is bonded to the subject. Thus, the adhesive sheet 10 can be strongly applied to the subject.

The adhesive sheet 10 like this has various applications. Appropriate re-peelability is useful for applications where position changes are important. For example, in fixture of a wall material, a flooring material, a tile material, a sash material, a sign, a display panel, a battery cell, an on-board device, a wiring cable, and the like, when, after temporary junction, a change in position is desired, it may be effective to provide favorable re- peelability and to enable a change in position for allowing application again (re application and re-temporary -junction). Application of the adhesive sheet 10 for such applications is particularly useful. Additionally, a high adhesive force is often required in such applications. The adhesive sheet 10 allows the provision, in a compatible manner, of a function to enable temporary junction, re-peeling, and re-application and a function to provide a high adhesive force when strong compression bonding is performed.

An initial adhesive force of 0.5 N/cm or more improves adhesiveness when the adhesive sheet 10 is temporarily joined to the subject. An initial adhesive force of 5 N/cm or less allows the adhesive sheet 10 temporarily joined to the subject to be peeled off with a weak force.

In a case where the angle Q formed by the side surface 3 and the bottom surface 1 of the cone structure 31 is 5° or larger, the distance from the bottom surface 1 of the cone structure 31 to the subject increases. Thus, when the adhesive sheet 10 is pressed against the subject at low pressure, the second part 5 can be inhibited from contacting the subject over a large area. Accordingly, after the adhesive sheet 10 is pressed against the subject at low pressure, the adhesive sheet 10 can be easily peeled off from the subject. That is, the adhesive sheet 10 having good re-peelability is obtained.

In a case where the height H of the cone structure 31 is 5 pm or larger, the distance from the bottom surface 1 of the cone structure 31 to the subject increases. Thus, when the adhesive sheet 10 is pressed against the object at low pressure, the second part 5 can be inhibited from contacting the subject over a large area. Accordingly, after the adhesive sheet 10 is pressed against the subject at low pressure, the adhesive sheet 10 can be easily peeled off from the subject. That is, an adhesive sheet 10 having good re-peelability is obtained.

In a case where the height H of the cone structure 31 is 100% and where the height HI of the first part 4 is in the range from 10% to 90% of the height H of the cone structure 31, after the adhesive sheet 10 is pressed against the subject at low pressure, the adhesive sheet 10 can be easily peeled off from the subject, whereas, when the adhesive sheet 10 is pressed against the subject at high pressure, the second part 5 can contact the subject with a large area.

FIG. 3 is a cross-sectional view of an adhesive sheet according to another embodiment. An adhesive sheet 110 illustrated in FIG. 3 includes the adhesive layer 12 illustrated in FIGS. 1 and 2, the liner 71 disposed on the fine structure 13, and a carrier 102 provided on the back surface 12b provided with no fine structure. The liner 71 can protect the fine structure 13. The adhesive sheet 110 may not include any one of the liner 71 and the carrier 102. For example, when the adhesive sheet 110 does not include the carrier 102, a roll can be formed by winding the adhesive sheet 110 around a core with the adhesive layer 12 on the inner side.

Examples of the carrier 102 include a resin film, for example, a film made from ABS, ASA, acrylic, polycarbonate, polyurethane, fluorine resins, polypropylene, PET, or PVC. The use of an elastic carrier 102 such as acrylic foam allows the cone structures 31 in the fine structure 13 to be sunken into the carrier 102. This may bring the second part 5 of the cone structure 31 into easy contact with the subject, improving the adhesiveness of the adhesive sheet 110. The adhesive sheet 110 can include any layer including a primer or the like between the carrier 102 and the adhesive layer 12.

Examples of the liner 71 include a film made from a material similar to the material of the carrier 102.

FIG. 4 is a cross-sectional view of an adhesive sheet according to another embodiment. An adhesive sheet 210 illustrated in FIG. 4 includes an adhesive layer 112 and a pair of liners 71 sandwiching the adhesive layer 112. The adhesive layer 112 has a configuration in which the fine structure 13 is provided on the back surface 12b of the adhesive layer 12 illustrated in FIGS. 1 and 2. Thus, both the front surface 112a and the back surface 112b of the adhesive layer 112 are each provided with the fine structure 13. The back surface 112b is a surface opposite to the front surface 112a. The fine structures 13 provided on the front surface 112a and the back surface 112b may have an identical structure or different structures. For example, the material or the height HI of the first part 4 may be identical or different between the front surface 112a and the back surface 112b.

FIG. 5 is a partial cross-sectional view of an adhesive sheet according to another embodiment. An adhesive sheet 310 illustrated in FIG. 5 includes the same configuration as the configuration of the adhesive sheet 10 except that the adhesive sheet 310 includes a plurality of frustum structures 131 instead of the plurality of cone structures 31, and that the plurality of frustum structures 131 are disposed at intervals b in the array direction. Each of the frustum structures 131 includes a structure obtained by partially cutting off an uppermost part of the cone structure 31 including the apex. Examples of a shape of the frustum structure 131 includes a truncated cone, a triangular truncated cone, a quadrangular truncated cone, a hexagonal truncated cone, and the like. Each frustum structure 131 includes a first part 4 present at a top 2 of the frustum structure 131 and a second part 5 present in a lower side (a bottom surface 1 side) of the first part 4. In the array direction of the frustum structures 131, the width of a top surface of the frustum structure 131 is defined as a and an interval between the top surfaces of the frustum structures 131 adjacent to each other is defined as b. When a is 0, the frustum structure 131 includes the same structure as the cone structure 31.

The width a of the top surface of the frustum structure 131 in the array direction of the frustum structures 131 is, for example, 50 pm or less, 40 pm or less, 30 pm or less, 20 pm or less, or 10 pm or less. Reduction of adhesive force exerted under pressure of a certain level or more can be prevented by making the width a of the top surface not too large with respect to the width a of the bottom surface 1.

FIG. 6 is a cross-sectional view illustrating other examples of the cone structure. A cross section of the cone structure 31 can have a triangular shape as illustrated in (a) of FIG. 6, may have distorted side surfaces as illustrated in (b) to (d), or may have a shape in which a position of an apex is shifted from the center of a bottom surface as illustrated in (e). As illustrated in (f) of FIG. 6, a cross section of the cone structure 31 can have a distorted side surfaces and has a shape in which a position of an apex is shifted from the center of a bottom surface. Note that all the cross sections passing through the apices of the cone structures 31 do not necessarily have the same shape, and may have different shapes for each cross section.

FIG. 7 is a cross-sectional view illustrating other examples of the frustum structure. A cross section of the frustum structure 131 may have a trapezoidal shape as illustrated in (a) of FIG. 7, may have distorted side surfaces as illustrated in (b) to (c), or may have a distorted top surface illustrated in (d) to (e). As illustrated in (f) of FIG. 7, a cross section of the frustum structure 131 may have distorted side surfaces and a distorted top surface. Note that all the cross sections passing through the apices of cones corresponding to the frustum structures 131 do not necessarily have the same shape, and may have different shapes for each cross section. Additionally, the top surface of the frustum structure 131 may not be in parallel with the bottom surface, or may not be a flat surface.

FIG. 8 is a perspective view of an adhesive sheet according to another embodiment. An adhesive sheet 410 illustrated in FIG. 8 includes the same configuration as the configuration of the adhesive sheet 10 illustrated in FIG. 1 except that the adhesive sheet 410 includes a plurality of rib structures 231 instead of the plurality of cone structures 31. The adhesive sheet 410 includes an adhesive layer 212 including a fine structure 113 including the plurality of rib structures 231. The plurality of rib structures 231 are arrayed along the X-axis direction, and each rib structure 231 extends in the Y- axis direction. Each rib structure 231 includes a first part 14 present at a top of the frustum structure 231 and a second part 15 present in a lower side (bottom surface side) of the first part 14. A cross section of the adhesive sheet 410 orthogonal to the Y-axis direction is the same as the cross section of the adhesive sheet 10 illustrated in FIG. 2.

The rib structure 231 is a solid figure that includes, as a bottom surface, a plane figure in which a length in any axial direction (Y-axis direction) on a plane is greater than a length in an axial direction (X-axis direction) orthogonal to the axis, and that is constituted by connecting all points in a side of the bottom surface and all points in a line or a side of a rectangle extending in a direction substantially parallel to the Y-axis direction. A cross section of the rib structure 231 can have any shape as illustrated in FIGS. 6(a) to 6(f) and FIGS. 7(a) to 7(f) as with the cone structure 31 and the frustum structure 131. A ratio of the length in the Y-axis direction of the bottom surface of the rib structure 231 to the length in the X-axis direction, that is, an aspect ratio is, for example, 2 or more, 3 or more, 4 or more, 5 or more, 10 or more, 50 or more, 100 or more, 500 or more, 1000 or more, or 10000 or more. The rib structure 231 may be formed continuously along any axial direction across the entire surface of the adhesive sheet 410.

FIG. 9 is a cross-sectional view illustrating a step in a method of manufacturing the adhesive sheet of FIG. 3. FIG. 10 is a cross-sectional view illustrating a step following the step of FIG. 9. FIG. 11 is a cross-sectional view illustrating a step following the step of FIG. 10. The adhesive sheet 110 of FIG. 3 can be manufactured, for example, through the following steps.

Mold preparation step

First, as illustrated in FIG. 9(a), a mold 61 is prepared. The mold 61 includes a surface 61a provided with a fine structure 61b. The fine structure 61b includes a plurality of cone structures 61c. The mold 61 can be produced by machining a flat plate including a material such as a metal or a resin by using a diamond cutter or a laser. The cone structure 61c has substantially the same shape as the cone structure 31 of the adhesive sheet 110. A difference in the size between the cone structure 61c and the cone structure 31 is preferably within ±5%, within ±3%, or within ±1%. However, with respect to the height H of the cone structure 31, a greater difference may be caused due to influence of shrinkage of the second part 5 and gravity. Note that the size of the cone structure 31 means the size obtained, for example, within 5 minutes or within 3 minutes immediately after the liner 71 is peeled.

Liner production step

Next, as illustrated in FIGS. 9(a) to 9(c), the mold 61 is pressed against the liner 71, to transfer the fine structure 61b of the surface 61a of the mold 61 to the liner 71. Examples of a material of the liner 71 include a material with which the fine structure 61b can be formed by the transfer and can be retained. The liner 71 in an example includes a sheet 71a including a resin laminated on a surface of a sheet body made from a resin or paper, and a release coating 71b provided in a surface of the sheet 71a. The release coating 71b is made from silicone, for example. The fine structure 61b can be transferred by bringing the mold 61 into contact with the surface (release coating 71b) of the liner 71, and heat pressing the surface of the liner 71. A fine structure 72 complementary to the fine structure 61b of the mold 61 is formed by the transfer on the surface of the liner 71. The fine structure 72 includes a plurality of recesses 72a including cone structures.

First part formation step

Next, as illustrated in FIGS. 10(a) to 10(d), the first part 4 is formed by applying a solution including a first adhesive material to the fine structure 72 of the liner 71 and then curing the solution.

First, as illustrated in FIG. 10(a), a solution 81 including the first adhesive material is applied by coating, spraying, or the like to the fine structure 72 formed on the surface of the liner 71.

Next, as illustrated in FIG. 10(b), an excess of the solution 81 is scraped off by, for example, a removal device 82 such as a doctor blade or a squeegee. The removal device 82 moves in a direction A along the surface of the liner 71. Accordingly, the solution 81 is reserved in each of the recesses 72a formed on the surface of the liner 71 as illustrated in FIG. 10(c). In the fine structure 72 formed on the surface of the liner 71, when an interval between the recesses 72a is small, the solution 81 is preferably easily scraped off.

Next, as illustrated in FIG. 10(d), the solution 81 in the recesses 72a is dried, and a solvent is removed. Thus, the first part 4 is formed in each recess 72a. The first part 4 is disposed in a lowermost part of each recess 72a and is made from a solid first adhesive material. After drying, as necessary, the first part 4 may be irradiated with an ultraviolet ray, an electron beam, or the like to cure the first adhesive material. In an embodiment, as illustrated in FIG. 10(d), the first part 4 occupies a space from the lowermost part to the middle of the recess 72a, and includes, in an upper part side, a surface substantially parallel to the horizontal plane defined by placement of the liner 71 during drying. Note that in the mold 61 used in producing the liner 71, when the angle Q formed between the side surface and the bottom surface of the cone structure 61c is large, or when the distance between the bottom surfaces of the cone structures 61c is short, the solution 81 including the first adhesive material can easily reach the lowermost part of the recess 72a. As a result, formation of the first part 4 is also easy. The solution 81 is, for example, a solution formed by dissolving and/or dispersing, into an appropriate solvent, an acrylic adhesive, a rubber adhesive, a silicone-based adhesive, a urethane-based adhesive, a polyester-based adhesive, a polyolefin-based adhesive, and an adhesive obtained by blending any of these adhesives. The solvent used in the solution 81 may also affect the above-described scraping off of the solution 81. For example, when a solvent such as ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, or the like is used, the distance between the bottom surfaces of the cone structures 61c in the mold 61 is preferably shorter (e.g. 50 pm or less).

Second part formation step

Next, as illustrated in FIG. 11(a), a second adhesive material or a precursor of the second adhesive material is applied to the liner 71 in which the first part 4 is formed, thus forming the second part 5. In the present embodiment, the adhesive layer 12 including the second part 5 and the base 32 is formed on the liner 71. When any other part is present between the first part 4 and the second part 5, the second part 5 may be formed after the formation of the first part 4 and then the formation of the any other part. The application of the second adhesive material can be performed by a variety of methods. For example, the second adhesive material molded in advance into a sheet shape or the like is applied to the fine structure 72 of the liner 71, and the fine structure 72 is subjected to heat and/or pressure or kept stationary at normal temperature and normal pressure for a certain period of time or more. Thus, the second adhesive material is caused to flow into the recesses 72a on the surface of the liner 71, and is joined to the first part 4 located at the lowermost part of each of the recesses 72a. In another example, a precursor cured into a second adhesive material by irradiation with an energy ray such as an ultraviolet ray or an electron beam is applied to the fine structure surface 72 of the liner 71 to enter the recesses 72a, and is then irradiated with an energy ray. In another example, a solution of the second adhesive material is applied to the fine structure 72 of the liner 71 to enter the recesses 72a, and is then heated as necessary, and dried to remove the solvent.

Carrier formation step

Next, as illustrated in FIGS. 11(b) to 11(c), the carrier 102 such as a PVC film is formed on the adhesive layer 12. The carrier 102 is laminated onto the adhesive layer 12, for example, by using a roller 103.

Through the steps described above, the adhesive sheet 110 of FIG. 3 can be manufactured. After the second part 5 is formed as illustrated in FIG. 11(a), the liner 71 may be peeled from the adhesive layer 12 without forming the carrier 102. In this case, the adhesive sheet 10 of FIGS. 1 and 2 can be manufactured. Additionally, when the second part 5 is formed, a pair of the liners 71 (see FIG. 10(d)) in which the first part 4 remains in the recess 72a may be prepared, and a second adhesive material or a precursor of the second adhesive material may be disposed between the pair of liners 71. In this case, the adhesive sheet 210 of FIG. 4 can be manufactured. Further, the adhesive sheet 310 of FIG. 5 or an adhesive sheet 410 of FIG. 8 can be manufactured in a manner similar to that described above by changing the shape of the fine structure 61b of the mold 61.

FIG. 12 is a cross-sectional view illustrating a step of applying the adhesive sheet 110 of FIG. 3 to a subject. First, as illustrated in FIG. 12(a), the liner 71 is removed from the adhesive sheet 110, and the adhesive sheet 110 is placed on a subject 111 such that the first part 4 of the adhesive layer 12 faces the subject 111. The subject 111 may be, for example, a plate-like member such as a glass plate. While a low pressure (arrow B) is applied to the adhesive layer 12 via the carrier 102, the first part 4 contacts the subject 111 due to deformation of the first part 4 or the like. The second part 5 does not contact the subject 111 or only slightly contacts the subject 111. Under low pressure, the adhesive layer 12 exerts a low adhesive force to the subject 111. That is, by adhering the first part 4 to the subject 111, the adhesive sheet 110 is temporarily joined to the subject 111. In the temporary junction state, the adhesive sheet 110 can be easily peeled off from the subject 111 On the other hand, as illustrated in FIG. 12(b), when a certain pressure or higher (arrow C) is applied to the adhesive layer 12 via the carrier 102, the second part 5 itself is deformed, the first part 4 is deformed, or the first part 4 is incorporated into the second part 5 to bring the second part 5 into contact with the subject 111. Under high pressure, the adhesive layer 12 exerts a high adhesive force to the subject 111. That is, by adhering the second part 5 to the subject 111, the adhesive sheet 110 is fixed to the subject 111. Thus, the adhesive sheet 110 can be temporarily joined to the subject 111 by being pressed against the subject 111 at low pressure, while the adhesive sheet 110 can be fixed to the subject 111 by being pressed at high pressure (this may be referred to as permanent fixture compared to temporary junction).

Similarly, the adhesive sheets 10, 210, 310, and 410 can be temporarily joined or fixed to the subject 111.

FIG. 13 is a cross-sectional view illustrating a panel product according to one embodiment and a subject to which the panel product is to be applied. The panel product 501 illustrated in FIG. 13 includes the adhesive sheet 10 and a panel 51 provided on the back surface 12b of the adhesive sheet 10. Examples of the panel 51 include an architectural panel such as a wall material, a flooring material, a tile material, a sash material, or a sign. The panel product 501 is pressed against the subject 111 with the first part 4 of the adhesive layer 12 facing the subject 111. Examples of the subject 111 include a wall, a floor, a ceiling, and the like of a building.

With the panel product 501, after the adhesive sheet 10 is pressed and temporarily joined to the subject 111 at low pressure, the adhesive sheet 10 can be pressed and fixed to the subject 111 at high pressure. Thus, workability is improved when the panel product

501 is applied to the subject 111.

FIG. 14 is a cross-sectional view illustrating a sheet product according to an embodiment and a subject to which the sheet product is to be applied. The sheet product

502 illustrated in FIG. 14 includes an adhesive sheet 10 and a sheet member 52 provided on the back surface 12b of the adhesive sheet 10. Examples of the sheet member 52 include wallpaper, paper, a resin sheet, and the like. The sheet product 502 is pressed against the subject 111 with the first part 4 of the adhesive layer 12 facing the subject 111. Examples of the subject 111 include a wall, a floor, a ceiling, and the like of a building. With the sheet product 502, after the adhesive sheet 10 is pressed and temporarily joined to the subject 111 at low pressure, the adhesive sheet 10 can be pressed and fixed to the subject 111 at high pressure. Thus, workability is improved when the sheet product

502 is applied to the subject 111.

FIG. 15 is a cross-sectional view illustrating a cable product according to an embodiment and a subject to which the cable product are to be applied. A cable product

503 illustrated in FIG. 15 is, for example, a wiring cable attached to a vehicle body. The cable product 503 includes a cable 53 and the adhesive sheet 10 provided on at least a portion of an outer circumferential surface 53 s of the cable 53. The cable 53 includes a wire extending along an axis 53 Ax of the cable 53 and an insulation layer covering the wire. The back surface 12b of the adhesive layer 12 of the adhesive sheet 10 faces at least a portion of the outer circumferential surface 53 s. The adhesive sheet 10 extends along the axis 53 Ax of the cable 53. In the present embodiment, the adhesive sheet 10 is provided on a portion of the outer circumferential surface 53 s in a cross section orthogonal to the axis 53 Ax of the cable 53. However, the adhesive sheet 10 may be provided all around the outer circumferential surface 53s (entire circumference) in a cross section orthogonal to the axis 53 Ax of the cable 53. The cable product 503 is pressed against the subject 111 with the first part 4 of the adhesive layer 12 facing the subject 111. An example of the object 111 is a ceiling lining material of a vehicle body or the like. The adhesive sheet 10 may be provided on at least a portion of the outer circumferential surface of a cable bundle including a plurality of the cables 53. When the adhesive sheet 10 is provided all around the outer circumferential surface of the cable bundle (the entire circumference), there is no need for a binding member for bundling a plurality of the cables 53.

With the cable product 503, after the adhesive sheet 10 is pressed against the subject 111 at low pressure and temporarily joined to the subject 111, the adhesive sheet 10 can be pressed against the subject 111 at high pressure and fixed to the subject 111. In addition, in the cable product 503, the cable 53 is substantially the same in length as the adhesive sheet 10 along the axis 53 Ax, and thus possible noise can be suppressed that is caused by a difference in length between the cable 53 and the adhesive sheet. Furthermore, when the cable product 503 is held by hand, the adhesive sheet 10 can be inhibited from firmly sticking to the hand. Thus, the cable product 503 can be easily handled manually Examples

The present disclosure will be described in detail below by way of examples, but the present disclosure is not intended to be limited to the examples.

Example 1

A diamond cutter was used to machine a metal (nickel) flat plate to produce a mold including a plurality of uniformly disposed square pyramid structures (recesses). The angle between the bottom surface and the side surface of the square pyramid (corresponding to Q in FIG. 2) was 30°, the width of the bottom surface of the regular square pyramid (corresponding to a in FIG. 2) was 45 pm, and the height of the square pyramid (corresponding to H in FIG. 2) was 13 pm. Note that the size of the regular square pyramid was measured by observing a surface of the mold by using a high precision microscope, and selecting one regular square pyramid from which the clearest observation image can be obtained.

Then, A base liner was provided, the base liner including layers each made of polyethylene (PE) and provided on respective surfaces of a sheet made of polyethylene terephthalate (PET), silicone coating being applied to one of the PE layers to form a peel- off surface. A mold was brought into contact with the release surface of the base liner, and the fine structure of the mold was transferred to the base liner by heat pressing to produce a liner including a fine structure. Specifically, the mold was pressed against the base liner at a pressure of 7 N/cm² at 120°C for 5 minutes. After cooling down to 55°C, the mold was removed, and a liner was obtained. The fine structure on the liner had substantially the same size as the size of the fine structure of the mold.

Then, an acrylic emulsion solution was applied onto the fine structure of the liner, the solution containing 15.6 mass% acrylic emulsion (manufactured by Emulsion Technology Co., Ltd., product name AE-222 C), 42.2 mass% distilled water, and 42.2 mass% isopropyl alcohol (IP A). A solid content of the solution was 5%. After application, excess solution was scraped off by a doctor blade or a squeegee. Subsequently, the liner was heated in an oven at 80°C for 4 minutes and at 100°C for 4 minutes to volatilize water, alcohol or other organic solvent, or a solvent including a mixture thereof, with a solid acrylic resin (the first part 4 of FIG. 2) disposed at the bottom of the square pyramid structure of the liner. Thus, as illustrated in FIG. 2, the height HI of the first part was 4 pm, and the width al of the bottom surface of the first part was 10 pm. A UV curable acrylic adhesive precursor was then applied onto the fine structure of the liner. The UV curable acrylic adhesive precursor is prepared as follows. First, 92 parts by mass of 2-ethylhexyl acrylate, 8 parts by mass of acrylic acid, and 0.04 parts by mass of a photoinitiator (product name Runtecure (registered trademark) 1065) are placed in a container and stirred at room temperature for 30 minutes. Subsequently, the mixture is stirred and the mixture is deformed using a hybrid mixer for 5 minutes. In a nitrogen atmosphere, the mixture is irradiated with UV light at an intensity of 3 mW/cm² for 30 to 60 seconds for partial polymerization. Thus, a transparent polymer solution having a viscosity of 2000 to 3000 cps (2 to 3 Pa s) was obtained. Then, 0.08 parts by mass of 1,6- hexanediol acrylate and 0.10 parts by mass of a photoinitiator (product name Runtecure (registered trademark) 1065) are placed in a container and mixed with the polymer solution. The mixture was stirred for 10 minutes and the mixture was deformed using a hybrid mixer for 5 minutes. In this way, a UV curable acrylic adhesive precursor was obtained.

The PET carrier was then overlaid onto the UV curable acrylic adhesive precursor using a knife coater. UV was radiated on the carrier to cure the UV curable acrylic adhesive precursor. A first zone of a UV irradiation apparatus irradiated the precursor with UV light with an intensity 0.9 mW/cm² and a second zone irradiated the precursor with UV light with an intensity of 7.0 mW/cm². The cured acrylic adhesive includes a portion (second part 5 in FIG. 2) located within the square pyramid structure of the liner and a base (base 32 in FIG. 2) supporting the second part. The height H2 of the second part was 9 pm, the width a of the bottom surface of the second part was 45 pm, and the height H3 of the base was 404 pm. In this way, an adhesive layer having a plurality of convex structures on a front surface of the adhesive layer was formed between the PET carrier and the liner.

Then, the PET carrier and the liner were peeled off to produce an adhesive sheet of Example 1 having a structure similar to the structure of the adhesive sheet 10 of FIGS. 1 and 2.

Example 2

An adhesive sheet of Example 2 was produced as is the case with Example 1 except that, when the first part was formed, instead of 15.6 mass% acrylic emulsion (manufactured by Emulsion Technology Co., Ltd., product name AE-222 C), 15.6 mass% acrylic emulsion (manufactured by Soken Chemical & Engineering Co., Ltd., product name E-33D) was used. As a result, as illustrated in FIG. 2, the height HI of the first part was 4 pm, the width al of the bottom surface of the first part was 9 pm, the height H2 of the second part was 9 pm, the width a of the bottom surface of the second part was 45 pm, and the height H3 of the base portion was 406 pm.

Example 3

An adhesive sheet of Example 3 was produced in a similar manner to that in Example 1 except that, when the second part was formed, the height of the base H3 as illustrated in FIG. 2 was 805 pm. As illustrated in FIG. 2, the height HI of the first part was 4 pm, the width al of the bottom surface of the first part was 10 pm, the height H2 of the second part was 9 pm, and the width a of the bottom surface of the second part was 45 pm.

Example 4

An adhesive sheet of Reference Example 4 was produced in a similar manner to that in Example 2 except that, when the second part was formed, the height H3 of the base as illustrated in FIG. 2 was 803 pm. As illustrated in FIG. 2, the height HI of the first part was 4 pm, the width al of the bottom surface of the first part was 9 pm, the height H2 of the second part was 9 pm, and the width a of the bottom surface of the second part was 45 pm.

Reference Example 1

After a UV curable acrylic adhesive precursor was applied onto a smooth liner (PET) with no fine structure on a front surface of the smooth liner, the UV curable acrylic adhesive precursor was cured as is the case with Example 1. In this way, an adhesive sheet of Reference Example 1 was produced including an adhesive layer with flat opposite surfaces including no fine structure. The adhesive layer had a thickness of 400 pm. Reference Example 2

An adhesive sheet of Reference Example 2 was produced in a similar manner to that in Reference Example 1 except that the adhesive layer had a thickness of 800 pm.

First Evaluation

The adhesive sheets of Examples 1 to 4 and Reference Examples 1 to 2 were evaluated as follows.

Coefficient of static friction The coefficient of static friction of the adhesive sheet of Example 4 was measured in accordance with JIS K 7125 except that a metal sliding piece such as steel material (e.g., SS400 material that may include plating such as chrome plating) was pulled at a speed of 1000 mm/min. Specifically, the adhesive sheet was cut into a sample with a width of 80 mm and a length of 150 mm. A sample placed on a table of a slip/peel tester (TSH- 1202-5 ON, IMASS) with a surface with the fine structure facing upward, and in such a manner that a pressure sensitive adhesive surface was placed upward, and a plate-like steel material of 40 cm² and 200 g was placed directly on the sample as a sliding piece. The sliding piece was pulled at a speed of 1000 mm/min., and a static friction force (F_s) was measured by using a load cell. From measurement results, the coefficient of static friction (p_s) was calculated in accordance with the following equation: p_s = Fs/Fp

F_s: static friction force (N)

FP: normal force (N) (= 1.96 N)

Initial adhesive force

The 90° peeling adhesive force (initial adhesive force) was measured in accordance with JIS Z 1541 except that the roller had a mass of 100 g and that the left standing time after compression bonding was 1 minute. Specifically, first, each adhesive sheet was cut into a sample with a width of 25 mm and a length of 75 mm. Then, each sample was then applied to a backing material such that the back surface of the sample opposite to the front surface with the fine structure was in contact with the backing material (anodized aluminum plate). Then, each sample was placed on a stainless steel plate (BA plate) having a glazed finish such that the surface of the sample with the fine structure was in contact with the stainless steel plate, and the sample was compression- bonded to the BA plate using a roller of 100 g. After the sample was left at normal temperature for 1 minute, the 90° peeling adhesive force was measured at a tensile rate of 300 mm/min.

(Re-peelability and re-initial-adhesion)

Re-peelability was evaluated by conducting a sensory test in which the sample was compression-bonded to a BA plate by using a roller of 100 g and left at normal temperature for 1 minute and in which the sample was then peeled off by hand. A further sensory test was conducted to evaluate whether the sample was successfully re-adhered (re-initial-adhesion) to the BA plate.

Adhesive force after 72 hours

The 90° peeling adhesive force (adhesive force after 72 hours) was measured when a test was conducted in accordance with JIS Z 1541, with the roller having a mass of 5 kg and the left standing time after compression bonding being 72 hours. Specifically, first, each adhesive sheet was cut into a sample with a width of 25 mm and a length of 75 mm. Then, each sample was applied to a backing material such that the back surface of the sample opposite to the front surface with the fine structure was in contact with the backing material. Then, each sample was placed such that the surface with the fine structure was in contact with the BA plate, and the sample was bonded to the BA plate by using a roller of 5 kg. After the sample was left at room temperature for 72 hours, the 90° peeling adhesive force was measured at a tensile speed of 300 mm/min.

First evaluation results are indicated in Table 1.

Table 1

As indicated in Table 1, the initial adhesive force of each of the adhesive sheets of Examples 1 to 4 was smaller than the initial adhesive force of each of the adhesive sheets of Reference Examples 1 and 2. That is, the adhesive sheets of Examples 1 to 4 provided favorable re-peelability compared to the adhesive sheets of Reference Examples 1 and 2. Additionally, the coefficient of static friction of the adhesive sheet of Example 4 was 11.8. Since the initial adhesive force of the adhesive sheet of Example 4 is smaller than the initial adhesive forces of the adhesive sheets of Examples 1 to 3, the adhesive sheets of Examples 1 to 3 have a coefficient of static friction of larger than 11.8.

Example 5

An adhesive sheet of Example 5 was produced as is the case with Example 1 except that a different type of acrylic emulsion solution was used to form the first part and that a UV curable acrylic adhesive precursor with a different compound ratio was used to form the second part.

In the present example, the first part was formed by using an acrylic emulsion solution containing 58.8 mass% acrylic emulsion (manufactured by Soken Chemical & Engineering Co., Ltd., product name SK dine R-103 C), 20.6 mass% distilled water (manufactured by FUJIFILM Wako Pure Chemical Corporation), and 20.6 mass% isopropyl alcohol (IP A, available from GoDo Co., Ltd.). The solid content of the solution was 32. 4%.

In addition, when the second part was formed, a polymer solution was prepared by using 87.5 parts by mass of 2-ethylhexyl acrylate, 12.5 parts by mass of acrylic acid, and 0.03 parts by mass of a photoinitiator (product name Runtecure (registered trademark) 1065), and a UV curable acrylic adhesive precursor was obtained using 0.065 parts by mass of 1,6-hexanediol acrylate and 0.20 parts by mass of a photoinitiator (product name Runtecure (registered trademark) 1065).

In the adhesive sheet according to the present example, as illustrated in FIG. 2, the height HI of the first part was 5 pm, the width al of the bottom surface of the first part was 23 pm, the height H2 of the second part was 5 pm, the width a of the bottom surface of the second part was 45 pm, and the height H3 of the base was 477 pm.

Example 6

An adhesive sheet of Example 6 was produced as is the case with Example 5 except that a different type of acrylic emulsion solution was used to form the first part.

In the present example, the first part was formed by using an acrylic emulsion solution containing 25.0 mass% acrylic emulsion (manufactured by Soken Chemical & Engineering Co., Ltd., product name SK dine R-103 C), 37.5 mass% distilled water (manufactured by FUJIFILM Wako Pure Chemical Corporation), and 37.5 mass% isopropyl alcohol (IP A, available from GoDo Co., Ltd.). The solid content of the solution was 13. 8%. In the adhesive sheet according to the example, as illustrated in FIG. 2, the height HI of the first part was 2 pm, the width al of the bottom surface of the first part was 11 pm, the height H2 of the second part was 8 pm, the width a of the bottom surface of the second part was 45 pm, and the height H3 of the base portion was 404 pm.

Example 7

An adhesive sheet of Example 7 was produced as is the case with Example 5 except that a different type of acrylic emulsion solution was used to form the first part.

In the present example, the first part was formed by using an acrylic emulsion solution containing 5.6 mass% acrylic emulsion (manufactured by Soken Chemical & Engineering Co., Ltd., product name SK dine R-103 C), 47.2 mass% distilled water (manufactured by FUJIFILM Wako Pure Chemical Corporation), and 47.2 mass% isopropyl alcohol (IP A, available from GoDo Co., Ltd.). The solid content of the solution was 3. 1%.

In the adhesive sheet according to the present example, as illustrated in FIG. 2, the height HI of the first part was 2 pm, the width al of the bottom surface of the first part was 9 pm, the height H2 of the second part was 8 pm, the width a of the bottom surface of the second part was 45 pm, and the height H3 of the base portion was 409 pm.

Reference Example 3

After only a UV curable acrylic adhesive precursor of the same type as that in Example 5 was applied onto a smooth liner (PET) with no fine structure on a surface of the smooth liner, and then the UV curable acrylic adhesive precursor was cured as is the case with Example 5. In this way, an adhesive sheet of Reference Example 3 was produced corresponding to an adhesive layer with flat opposite surfaces. In other words, the adhesive sheet of Reference Example 3 is an adhesive layer made only from the cured UV curable acrylic adhesive cured. The thickness of the adhesive layer was 416 pm. Reference Example 4

An adhesive sheet of Reference Example 4 was produced as is the case with Example 5 except that the first part was not formed.

The adhesive sheet of Reference Example 4 includes a plurality of square pyramid structures and bases made only from an acrylic adhesive obtained by curing a UV curable acrylic adhesive precursor. The height of the square pyramid structure was 11 pm, the width of the bottom surface of the square pyramid structure was 45 pm, and the height of the base was 410 pm.

Second Evaluation

The adhesive sheets of Examples 5 to 7 and Reference Examples 3 and 4 were evaluated for the above-described initial adhesive force and the items below.

Re-peelability

The re-peelability was evaluated as follows. Specifically, first, each adhesive sheet was cut into a sample of 25 mm ^c 25 mm. Then, each sample was applied to a backing material such that the back surface of the sample opposite to the front surface with the fine structure was in contact with the backing material. Each of an acrylic plate, a transparent PET plate, and an anodized aluminum plate was used as the backing material. Then, each sample was placed such that the surface with the fine structure was in contact with each of a glass plate and an SUS plate. Each sample was then peeled off from each of the glass plate and the SUS plate. Results of the second evaluation are indicated in Table 2.

Table 2

As indicated in Table 2, the initial adhesive forces of each of the adhesive sheets of Examples 5 to 7 was smaller than the initial adhesive force of each of the adhesive sheets of Reference Examples 3 and 4. That is, in the adhesive sheets of Examples 5 to 7 provided favorable re-peelability compared to the adhesive sheets of Reference Examples 3 and 4.

Example 8

An adhesive sheet having a structure similar to that of the adhesive sheet 10 in FIGS. 1 and 2 was wound around a bundle of wiring cables such that the back surface of the adhesive sheet opposite to the front surface with the convex structure faces the outer circumferential surface of the bundle of wiring cables. The bundle has a diameter of 10 mm. Thereafter, with the surface with the convex structure facing a plate-like member, the adhesive sheet was pressed against the plate-like member from above the wiring cables with a 1-kg roller moved at a speed of 600 mm/min. After two weeks passed with the plate member disposed vertically to make the adhesive sheet face sideways, the adhesive sheet remained held by the plate-like member.

Claims

What is claimed is:

1. An adhesive sheet comprising an adhesive layer comprising a fine structure on a front surface of the adhesive layer, wherein the fine structure includes a plurality of convex structures, each of the plurality of convex structures comprises two or more parts, a first part present at a top of the convex structure comprises a first adhesive material, a second part present below the first part comprises a second adhesive material comprising higher adhesiveness than the first adhesive material, and when a test is conducted in accordance with JIS K 7125 except that a metal sliding piece is pulled at a speed of 1000 mm/min., a coefficient of static friction is 10 or more.

2. The adhesive sheet according to claim 1, wherein, when a test is conducted in accordance with JIS Z 1541 except that a roller has a mass of 100 g and that a left standing time after compression bonding is 1 minute, a 90° peeling adhesive force is 0.5 N/cm or more and 5 N/cm or less.

3. The adhesive sheet according to claim 1 or 2, wherein the two or more parts are joined together via an interface.

4. The adhesive sheet according to any one of claims 1 to 3, wherein convex structure is 100%, a height of the first part is in a range from 10% to 90% of the height of the convex structure.

5. The adhesive sheet according to any one of claims 1 to 4, wherein an angle Q formed between a side surface and a bottom surface of the convex structure is 5° or more.

6. The adhesive sheet according to any one of claims 1 to 5, wherein a height of the convex structure is 5 pm or more.

7. A panel product comprising the adhesive sheet according to any one of claims 1 to 6 and a panel provided on a surface opposite to the front surface of the adhesive layer of the adhesive sheet.

8. A sheet product comprising the adhesive sheet according to any one of claims 1 to 6, and a sheet member provided on a surface opposite to the front surface of the adhesive layer of the adhesive sheet.

9. A cable product comprising: a cable; and the adhesive sheet according to any one of claims 1 to 6 provided on at least a portion of an outer circumferential surface of the cable, wherein a surface opposite to the front surface of the adhesive layer of the adhesive sheet faces at least the portion of the outer circumferential surface of the cable.