CN115427527A

CN115427527A - Double-sided adhesive tape

Info

Publication number: CN115427527A
Application number: CN202180028783.2A
Authority: CN
Inventors: 原田桃子; 前川博亮; 松井由纪菜; 石堂泰志
Original assignee: Sekisui Chemical Co Ltd
Current assignee: Sekisui Chemical Co Ltd
Priority date: 2020-09-23
Filing date: 2021-09-22
Publication date: 2022-12-02
Also published as: WO2022065392A1; JPWO2022065392A1; TW202219210A

Abstract

The invention aims to provide a double-sided adhesive tape which has high level difference following performance of two adhesive surfaces, can exert high holding force to shearing load and inclined load, has excellent reworkability of at least one adhesive surface, and further has excellent handling performance when being adhered. The present invention relates to a double-sided adhesive tape comprising a foam base and adhesive layers laminated on both sides of the foam base, wherein the foam base comprises a 1 st foamed resin layer and a2 nd foamed resin layer laminated on at least one side of the 1 st foamed resin layer, the 2 nd foamed resin layer has a lower expansion ratio than the 1 st foamed resin layer, and at least one of the adhesive layers has a storage modulus at 180 ℃ of 11000Pa or more.

Description

Double-sided adhesive tape

Technical Field

The present invention relates to a double-sided pressure-sensitive adhesive tape having high level difference following properties on both pressure-sensitive adhesive surfaces, capable of exerting a high holding force against a shear load and an oblique load, excellent in reworkability of at least one pressure-sensitive adhesive surface, and further excellent in handling properties at the time of adhesion.

Background

Adhesive tapes are widely used for fixing electronic components. Specifically, for example, in a display device such as a television or a monitor, an adhesive tape is used to fix a cover plate on the surface to a housing. Such an adhesive tape is used so as to be disposed in a shape such as a frame shape around a display screen.

In recent years, as a result of the demands for design and functionality, the frame of display devices such as televisions and monitors has been narrowed, and the expectation for frameless display devices has been increased. In the manufacture of conventional display devices, the cover plate is sometimes fixed to the housing by fitting or screwing, but in display devices with a narrowed bezel, fitting or screwing is difficult, and therefore, there is an increasing demand for fixing with an adhesive tape, and thinning and narrowing of the adhesive tape are also advancing.

As an adhesive tape that can be used for such a display device, for example,

patent documents

1 and 2 describe an impact absorption tape that is a crosslinked polyolefin resin foamed sheet in which an acrylic adhesive layer is integrally laminated on at least one surface of a base layer, and the base layer has a specific degree of crosslinking and an aspect ratio of bubbles.

Since the foam base material has appropriate flexibility and can relax stress, there are advantages that the use of the foam base material as the base material of the pressure-sensitive adhesive tape can improve the step following property, improve the impact resistance, and reduce the display unevenness generated in the display device.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2009-242541

Patent document 2: japanese laid-open patent publication No. 2009-258274

Disclosure of Invention

Problems to be solved by the invention

However, the display devices such as televisions and monitors are becoming larger in size, and the weight of the members to be fixed such as the cover and the housing is also increasing. Therefore, a very large load, which has been conventionally applied, is applied to the pressure-sensitive adhesive tape, particularly to the pressure-sensitive adhesive tape having a reduced thickness and a reduced width. In which a very large load is applied in the shear direction and a high holding force is required for the shear load. In addition, in applications such as wall-mounted televisions, the display device is often installed in a state tilted forward, for example, by about 20 to 45 ° with respect to the vertical direction, and a high holding force with respect to a tilting load is also required.

Further, in recent years, since electronic parts tend to be expensive, there is a demand for reworking of the parts when, for example, a failure occurs at the time of fixing the parts. As one of the methods for reworking a component, for example, the following methods are used: the foam base material of the adhesive tape was torn with a cutter knife to break the interlayer and the member was removed, and a part of the adhesive tape remaining on the member was peeled off and removed. In such a case, the pressure-sensitive adhesive tape is required to have excellent reworkability to be peeled and removed without leaving a residue (for example, a part of the foam base material left by breaking) on the member.

The invention aims to provide a double-sided adhesive tape which has high level difference following performance of two adhesive surfaces, can exert high holding force to shear load and inclined load, has excellent reworkability of at least one adhesive surface, and further has excellent handling performance when being pasted.

Means for solving the problems

The present invention relates to a double-sided adhesive tape, which comprises a foam base and adhesive agent layers laminated on both sides of the foam base, wherein the foam base comprises a 1 st foamed resin layer and a2 nd foamed resin layer laminated on at least one side of the 1 st foamed resin layer, the 2 nd foamed resin layer has a lower expansion ratio than the 1 st foamed resin layer, and at least one of the adhesive agent layers has a storage modulus at 180 ℃ of 11000Pa or more.

The present invention will be described in detail below.

The present inventors have studied a multilayer substrate as a foam base material, which is reinforced by laminating a resin layer on at least one surface of a foamed resin layer, in order to improve holding power against a shear load and an oblique load and improve reworkability of at least one pressure-sensitive adhesive surface in a double-sided pressure-sensitive adhesive tape having the foam base material and the pressure-sensitive adhesive layer laminated on both surfaces of the foam base material.

However, for example, when the resin layer on one side or both sides is too hard, the step following property on the side where the resin layer is laminated is lowered, and peeling is likely to occur. In recent years, the number of cases where an adhesive tape partially overlaps a polarizing plate in a display device or partially overlaps a guide formed in a housing in order to indicate a region where the adhesive tape is to be attached has increased, and in the case where the adhesive tape is used in a thin and narrow width, it is also required to sufficiently follow the height difference between the polarizing plate and the guide. On the other hand, in the case where the resin layer is too flexible on both surfaces in order to improve the level difference following property (for example, in the case where a styrene-acrylic block copolymer is used for the resin layer on both surfaces), the holding force against the shear load and the tilt load cannot be sufficiently obtained, and the adhesive tape is elongated at the time of sticking, which causes a problem of poor handling property.

In view of these problems, the present inventors have studied: the foamed resin layer (outermost layer) is also used as a resin layer laminated on the foamed resin layer (central foamed resin layer), and the expansion ratio of the outermost layer is adjusted to be lower than that of the central foamed resin layer. The present inventors have found that by using such a multilayer substrate as a foam substrate, both of the step following properties of both adhesive surfaces, the holding force against a shear load and an oblique load, and the reworkability of at least one adhesive surface can be simultaneously satisfied, and excellent handleability can be obtained. The present inventors have further found that the holding force against the shear load and the tilt load can be further improved by adjusting the storage modulus at 180 ℃ of at least one of the pressure-sensitive adhesive layers to a specific range, and have completed the present invention.

The double-sided adhesive tape of the present invention has a foam base and adhesive layers laminated on both sides of the foam base. By having the foam base, the double-sided pressure-sensitive adhesive tape of the present invention can exhibit an excellent stress relaxation property while having an improved level difference following property.

The foam base material has a 1 st foamed resin layer and a2 nd foamed resin layer laminated on at least one surface of the 1 st foamed resin layer, and the 2 nd foamed resin layer has a lower expansion ratio than the 1 st foamed resin layer.

By laminating the 2 nd foamed resin layer on the 1 st foamed resin layer, it is possible to alleviate the deformation stress of the 1 st foamed resin layer caused by the application of a shear load or a tilt load, to make it difficult to transmit the deformation stress to the pressure-sensitive adhesive layer, and to suppress the peeling of the pressure-sensitive adhesive layer. Further, by laminating the 2 nd foamed resin layer on the 1 st foamed resin layer, the double-sided adhesive tape of the present invention can be peeled and removed at the time of rework without leaving a residue (for example, a part of the 1 st foamed resin layer remaining by breaking) on an adherend on the side on which the 2 nd foamed resin layer is laminated, and can exhibit excellent reworkability.

In the double-sided adhesive tape of the present invention, the 2 nd foamed resin layer is laminated on the 1 st foamed resin layer, whereby the lowering of the step following property on both adhesive surfaces can be suppressed. On the other hand, in the case where an excessively soft resin layer is laminated on both surfaces of the first foamed resin layer 1 (for example, in the case where a styrene-acrylic block copolymer is used for the resin layers on both surfaces) in order to improve the step following property, there is a problem that the holding force against the shear load and the tilt load cannot be sufficiently obtained, and the handling property at the time of sticking is poor. In contrast, the double-sided adhesive tape of the present invention can exhibit high holding power against shear load and tilt load and excellent handling property at the time of sticking by laminating the 2 nd foamed resin layer on the 1 st foamed resin layer.

The foam base may have the 2 nd foamed resin layer only on one side of the 1 st foamed resin layer, or may have the 2 nd foamed resin layer on both sides of the 1 st foamed resin layer. Among them, from the viewpoint that the holding force of the double-sided adhesive tape against the shear load and the tilt load is further improved and excellent reworkability can be exhibited on both adhesive surfaces, it is preferable that the 2 nd foamed resin layer is provided on both surfaces of the 1 st foamed resin layer. In this case, the resin composition, physical properties, thickness, and the like of the 2 nd foamed resin layers on both sides may be the same or different.

In general, an adhesive tape is provided in a state of being wound into a roll, and is used after being pulled out from the roll. In the case where the resin layer is excessively hard and laminated on both surfaces of the first foamed resin layer 1, if the core has a diameter of a certain size or more, wrinkles or breaks may occur during winding. In contrast, in the double-sided pressure-sensitive adhesive tape of the present invention, by laminating the 2 nd foamed resin layer on the 1 st foamed resin layer, even when the 2 nd foamed resin layers are laminated on both sides, flexibility of the whole double-sided pressure-sensitive adhesive tape can be ensured. This makes it easy to wind the double-sided adhesive tape in a roll shape, remarkably improves handling properties, and suppresses wrinkles and breaks during winding.

The foam base may have another layer such as an adhesive layer in addition to the 1 st foamed resin layer and the 2 nd foamed resin layer, but it is preferable that no other layer is provided between the 1 st foamed resin layer and the 2 nd foamed resin layer from the viewpoint of preventing the complication of the production process.

Fig. 3 is a cross-sectional view schematically showing an example of the double-sided adhesive tape of the present invention. The double-sided pressure-sensitive adhesive tape 7 shown in fig. 3 includes a foam base 8 and pressure-sensitive adhesive layers 91 and 92 laminated on both sides of the foam base 8. The foam base 8 has a 1 st

foamed resin layer

10 and 2 nd

foamed resin layers

11 and 12 laminated on both surfaces of the 1 st foamed resin layer 10. In the double-sided pressure-sensitive adhesive tape shown in fig. 3, the 2 nd foamed resin layer is laminated on both sides of the 1 st foamed resin layer, but the present invention is not limited to such an embodiment.

The first foamed resin layer 1 may have an open cell structure or an isolated cell structure, and preferably has an isolated cell structure. By having the independent cell structure, the strength of the 1 st foamed resin layer is improved, and therefore, deformation and interlayer breakage of the 1 st foamed resin layer when a shear load and an inclination load are applied can be suppressed, and the holding force of the double-sided pressure-sensitive adhesive tape against the shear load and the inclination load can be further improved.

The first foamed resin layer 1 may have a single-layer structure or a multilayer structure.

The 1 st foamed resin layer is not particularly limited, and examples thereof include: a polyurethane foamed resin layer, a polyolefin foamed resin layer, a rubber foamed resin layer, an acrylic foamed resin layer, and the like. Among them, from the viewpoint of being able to exert excellent stress relaxation property and strength, a polyurethane foamed resin layer or a polyolefin foamed resin layer is preferable, and a polyolefin foamed resin layer is more preferable.

The polyurethane foam resin layer is not particularly limited, and examples thereof include: a polyurethane foam resin layer formed from a urethane resin composition containing a polyisocyanate and a polyol. Such a polyurethane foam resin layer can be produced by heat-curing the urethane resin composition.

The polyolefin foam resin layer is not particularly limited, and examples thereof include: a foamed resin layer formed of a resin such as a polyethylene resin, a polypropylene resin, or a polybutadiene resin. Among them, a foamed resin layer made of a polyethylene resin is preferable in that a flexible polyolefin foamed resin layer can be easily obtained.

The polyethylene resin is not particularly limited, and examples thereof include: polyethylene resins obtained by polymerization using a polymerization catalyst such as a Ziegler-Natta compound, a metallocene compound, or a chromium oxide compound. In addition, in view of increasing flexibility of the first foamed resin layer 1, linear low-density polyethylene is preferable as the polyethylene resin. The linear low-density polyethylene is preferably a linear low-density polyethylene obtained by copolymerizing ethylene with a small amount of an α -olefin used as needed, and examples of the α -olefin include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene. Among them, an α -olefin having 4 to 10 carbon atoms is preferable.

The expansion ratio of the 1 st foamed resin layer is not particularly limited as long as it is higher than the expansion ratio of the 2 nd foamed resin layer.

In the case where the 1 st foamed resin layer is a polyolefin foamed resin layer, a preferable lower limit of the foaming ratio of the 1 st foamed resin layer is 5cm ³ A preferred upper limit of 30 cm/g ³ (ii) in terms of/g. If the expansion ratio is 5cm ³ When the amount of the foaming resin is more than or equal to g, the 1 st foamed resin layer can have appropriate flexibility, and the step following property and the stress relaxation property of both adhesive surfaces of the double-sided adhesive tape can be further improved. If the expansion ratio is 30cm ³ When the ratio/g or less is smaller, the strength of the 1 st foamed resin layer is sufficiently improved, and the holding force of the double-sided pressure-sensitive adhesive tape against the shear load and the tilt load is further improved. A more preferable lower limit of the expansion ratio is 8cm ³ A more preferred upper limit of 25 cm/g ³ A further preferred lower limit is 10cm ³ A more preferred upper limit is 20 cm/g ³ A still more preferred upper limit is 18 cm/g ³ /g。

The expansion ratio can be determined in accordance with JIS K7222 (in the case of using polyethylene). The expansion ratio can be determined as the reciprocal of the apparent density.

The thickness of the first foamed resin layer 1 is not particularly limited, but the lower limit is preferably 100 μm and the upper limit is preferably 2000. Mu.m. When the thickness is 100 μm or more, the 1 st foamed resin layer can have appropriate flexibility, and the step following property and the stress relaxation property of both adhesive surfaces of the double-sided adhesive tape can be further improved. If the thickness is 2000 μm or less, the deformation of the 1 st foamed resin layer when a shear load and an inclination load are applied can be suppressed, and the holding force of the double-sided adhesive tape with respect to the shear load and the inclination load can be further improved. A more preferable lower limit of the thickness is 300. Mu.m, a more preferable upper limit is 1500. Mu.m, a further more preferable lower limit is 500. Mu.m, and a further more preferable upper limit is 1000. Mu.m.

The thickness of the foamed resin layer can be measured using a dial gauge (for example, "ABS digital INDICATOR" manufactured by Mitutoyo corporation).

The 2 nd foamed resin layer is not particularly limited as long as it has a lower foaming ratio than the 1 st foamed resin layer, and may be a foamed resin layer having the same cell structure, layer structure, resin composition, physical properties and the like as those of the 1 st foamed resin layer, or a foamed resin layer having a different cell structure, layer structure, resin composition, physical properties and the like from those of the 1 st foamed resin layer.

The 2 nd foamed resin layer may have an open cell structure or an isolated cell structure, and preferably has an isolated cell structure. By having the independent bubble structure, the strength of the 2 nd foamed resin layer is improved, and therefore, the double-sided adhesive tape can be peeled and removed at the time of rework without further residue (for example, a part of the 1 st foamed resin layer remaining by breaking) remaining on the adherend on the side on which the 2 nd foamed resin layer is laminated, and can exhibit more excellent reworkability.

The 2 nd foamed resin layer may have a single-layer structure or a multilayer structure.

The 2 nd foamed resin layer is not particularly limited, and examples thereof include: a polyurethane foamed resin layer, a polyolefin foamed resin layer, a rubber foamed resin layer, an acrylic foamed resin layer, and the like. Among them, from the viewpoint of being able to exert excellent stress relaxation property and strength, a polyurethane foamed resin layer or a polyolefin foamed resin layer is preferable, and a polyolefin foamed resin layer is more preferable.

The urethane foamed resin layer is not particularly limited, and may be the same as the urethane foamed resin layer in the 1 st foamed resin layer. The polyolefin foamed resin layer is not particularly limited, and may be the same as the polyolefin foamed resin layer in the 1 st foamed resin layer.

The expansion ratio of the 2 nd foamed resin layer is not particularly limited as long as it is lower than the expansion ratio of the 1 st foamed resin layer, and the preferable lower limit is 1.1cm ³ A preferred upper limit of 7 cm/g ³ (ii) in terms of/g. If the expansion ratio is 1.1cm ³ When the amount of the second foamed resin layer is more than or equal to g, the 2 nd foamed resin layer can have appropriate flexibility, and the step following property and the stress relaxation property of both adhesive surfaces of the double-sided adhesive tape can be further improved. If the above foaming ratio is 7cm ³ When the ratio/g or less is smaller, the strength of the 2 nd foamed resin layer is sufficiently improved, the holding force of the double-sided pressure-sensitive adhesive tape against the shear load and the tilt load is further improved, and the handling property at the time of sticking is further improved. A more preferable lower limit of the expansion ratio is 1.3cm ³ A more preferred upper limit is 5 cm/g ³ A further preferred lower limit is 1.4cm ³ A more preferred upper limit is 2 cm/g ³ A still more preferred lower limit is 1.5 cm/g ³ A still more preferred upper limit is 1.9 cm/g ³ /g。

The thickness of the 2 nd foamed resin layer is not particularly limited, and the lower limit is preferably 5 μm and the upper limit is preferably 100 μm. If the thickness is 5 μm or more, the holding force of the double-sided adhesive tape against the shear load and the tilt load is further improved. When the thickness is 100 μm or less, the step following property and the stress relaxation property of both adhesive surfaces of the double-sided adhesive tape are further improved. A more preferable lower limit of the thickness is 10 μm, a more preferable upper limit is 80 μm, a further more preferable lower limit is 30 μm, and a further more preferable upper limit is 60 μm.

The 25% compressive strength of the foam base (the entire foam base) is not particularly limited, and the lower limit is preferably 1kPa, and the upper limit is preferably 200kPa. When the 25% compressive strength is 1kPa or more, the strength of the foam base is sufficiently improved, and the holding force of the double-sided pressure-sensitive adhesive tape against a shear load and a tilt load is further improved. When the 25% compressive strength is 200kPa or less, the foam base material can have appropriate flexibility, and the step following property and the stress relaxation property of both adhesive surfaces of the double-sided adhesive tape can be further improved. A more preferable lower limit of the 25% compressive strength is 10kPa, a more preferable upper limit is 100kPa, a further preferable lower limit is 20kPa, and a further preferable upper limit is 40kPa.

For example, the 25% compressive strength of the foam base (the entire foam base) can be adjusted to be within the above range by adjusting the expansion ratio of the 1 st foamed resin layer.

The 25% compressive strength may be based on JIS K6254: 2016, which is obtained by the following measurement using "AutographAGS-X" manufactured by Shimadzu corporation, for example.

The foam base material was cut into pieces of 20mm × 20mm, and the pieces were stacked to prepare samples having a thickness of about 5mm × 20mm × 20 mm. The sample was crushed at a speed of 10mm/min in the compression direction, and the pressure (N) at which the sample was compressed by 25% was confirmed. The 25% compressive strength was calculated from the obtained pressure by the following formula (2). When the sample is compressed by 25% with the thickness of 100 (the sample has a thickness of 75), the sample is compressed by 25%.

Compressive strength (kPa) = pressure (N)/0.4 (2)

The thickness of the foam base (the entire foam base) is not particularly limited, and the lower limit is preferably 105 μm and the upper limit is preferably 2100 μm. When the thickness is within the above range, the holding force of the double-sided pressure-sensitive adhesive tape against the shear load and the tilt load is further improved, and the step following property and the stress relaxation property of both pressure-sensitive adhesive surfaces are further improved. A more preferable lower limit of the thickness is 310. Mu.m, a more preferable upper limit is 1580. Mu.m, a further preferable lower limit is 530. Mu.m, and a further preferable upper limit is 1060. Mu.m.

In the foam base, the ratio of the thickness of the 1 st foamed resin layer to the thickness of the 2 nd foamed resin layer (the value of the thickness of the 1 st foamed resin layer/the thickness of the 2 nd foamed resin layer) is not particularly limited, and a preferable lower limit is 1.0 and a preferable upper limit is 400. When the ratio of the thicknesses is within the above range, the holding force of the double-sided pressure-sensitive adhesive tape against the shear load and the tilt load is further improved, and the step following property and the stress relaxation property of both pressure-sensitive adhesive surfaces are further improved. A more preferable lower limit of the thickness ratio is 3, a more preferable upper limit is 150, a further more preferable lower limit is 5, and a further more preferable upper limit is 40.

In the foam base, the ratio of the expansion ratio of the 1 st foamed resin layer to the expansion ratio of the 2 nd foamed resin layer (the value of the expansion ratio of the 1 st foamed resin layer/the expansion ratio of the 2 nd foamed resin layer) is not particularly limited, and a preferable lower limit is 1.3 and a preferable upper limit is 100. When the ratio of the expansion ratios is within the above range, the holding force of the double-sided pressure-sensitive adhesive tape against the shear load and the tilt load is further improved, and the step following property and the stress relaxation property of both pressure-sensitive adhesive surfaces are further improved. A more preferable lower limit of the ratio of the expansion ratio is 3, a more preferable upper limit is 50, a further more preferable lower limit is 8, and a further more preferable upper limit is 20.

The method for producing the foamed base material is not particularly limited, and may be a method in which the 1 st foamed resin layer and the 2 nd foamed resin layer are separately produced and then they are pressure-bonded or bonded via an adhesive layer or the like, and preferably a method in which a plurality of layers are extruded using the foamable composition for forming the 1 st foamed resin layer and the foamable composition for forming the 2 nd foamed resin layer. In the case of the method of performing the multilayer extrusion, the 1 st foamed resin layer and the 2 nd foamed resin layer may be laminated without using a pressure-sensitive adhesive layer or the like, and it is preferable from the viewpoint of preventing the complication of the production process.

The method of performing the multilayer extrusion is not particularly limited, and for example, first, the foamable composition forming the 1 st foamable resin layer and the foamable composition forming the 2 nd foamable resin layer are separately extruded, and the separately extruded foamable compositions are joined in a layer form in a die in a molten state to obtain a laminate sheet in which a plurality of layers formed of the foamable composition are laminated. The foamable composition for forming the first foamed resin layer 1 and the foamable composition for forming the second foamed resin layer 2 are, for example, compositions containing the polyethylene resin and the thermal decomposition type foaming agent as described above. The expansion ratio of the foamed resin layer obtained can be adjusted by changing the type and amount of the thermal decomposition type foaming agent.

Next, at least one surface of the obtained laminate sheet is irradiated with ionizing radiation to crosslink the polyethylene resin. The expansion ratio of the foamed resin layer obtained can be adjusted by changing the degree of crosslinking of the polyethylene resin.

The foamed base material having the 1 st foamed resin layer and the 2 nd foamed resin layer can be obtained by foaming and crosslinking the laminated sheet by heating or the like. The stretching may be performed during and/or after foaming the crosslinked laminate sheet by heating or the like.

The adhesive layer is laminated on both surfaces of the foam base. The adhesive layers on both sides may be identical in resin composition, physical properties, thickness, and the like, or may be identical.

The lower limit of the storage modulus at 180 ℃ of at least one of the adhesive layers is 11000Pa. In this case, the storage modulus at 180 ℃ of both sides of the pressure-sensitive adhesive layer may be in this range, or the storage modulus at 180 ℃ of only one side may be in this range. When the storage modulus at 180 ℃ is 11000Pa or more, the volume strength of the adhesive layer (Japanese: 124961252312463. The storage modulus at 180 ℃ preferably has a lower limit of 13000Pa, more preferably has a lower limit of 15000Pa, and still more preferably has a lower limit of 20000Pa.

The upper limit of the storage modulus at 180 ℃ is not particularly limited, and a preferable upper limit is 50000Pa. If the storage modulus at 180 ℃ is 50000Pa or less, the occurrence of interfacial peeling when a shear load or a tilt load is applied due to insufficient wettability of the interface of the pressure-sensitive adhesive layer can be suppressed. A more preferable upper limit of the storage modulus at 180 ℃ is 40000Pa, and a further more preferable upper limit is 32000Pa.

The storage modulus at 180 ℃ of the above adhesive layer can be adjusted to the above range, for example, as follows: adjusting the composition, weight average molecular weight, molecular weight distribution (weight average molecular weight/number average molecular weight), and the like of the acrylic copolymer contained in the pressure-sensitive adhesive layer; adjusting the type and amount of the crosslinking agent and the tackifier resin contained in the pressure-sensitive adhesive layer; the gel fraction of the pressure-sensitive adhesive layer is adjusted.

The storage modulus at 180 ℃ can be determined using a viscoelasticity measuring apparatus (for example, "Rheometrics Dynamic analysis RDA-700" manufactured by Rheometrics) under conditions of a measurement temperature of-40 to 200 ℃, a temperature rise rate of 3 ℃/min, and a frequency of 10 Hz.

The pressure-sensitive adhesive layer is not particularly limited, and examples thereof include: acrylic pressure-sensitive adhesive layers, rubber pressure-sensitive adhesive layers, urethane pressure-sensitive adhesive layers, silicone pressure-sensitive adhesive layers, and the like. Among them, at least one of the pressure-sensitive adhesive layers is preferably an acrylic pressure-sensitive adhesive layer in view of being relatively stable to light, heat, moisture, and the like and being capable of adhering to various adherends (having low selectivity for adherends). That is, at least one of the pressure-sensitive adhesive layers preferably contains an acrylic copolymer. In this case, the pressure-sensitive adhesive layer may contain an acrylic copolymer on both surfaces or may contain an acrylic copolymer on only one surface.

The acrylic copolymer is preferably obtained by copolymerizing a monomer mixture containing butyl acrylate and/or 2-ethylhexyl acrylate, from the viewpoint that the initial tackiness thereof is improved and the ease of adhesion at low temperatures is improved. The acrylic copolymer is more preferably obtained by copolymerizing a monomer mixture containing butyl acrylate and 2-ethylhexyl acrylate.

The preferable lower limit of the content of the butyl acrylate in the whole monomer mixture is 30% by weight, and the preferable upper limit is 80% by weight. When the content of butyl acrylate is within this range, both high adhesion and tackiness can be achieved.

The content of the above-mentioned 2-ethylhexyl acrylate in the whole monomer mixture preferably has a lower limit of 10% by weight, a preferable upper limit of 100% by weight, a more preferable lower limit of 30% by weight, a more preferable upper limit of 80% by weight, a further preferable lower limit of 50% by weight, and a further preferable upper limit of 60% by weight. When the content of 2-ethylhexyl acrylate is within this range, high adhesive force can be exerted.

The monomer mixture may contain, if necessary, another polymerizable monomer copolymerizable with butyl acrylate and 2-ethylhexyl acrylate. Examples of the other copolymerizable monomers include: alkyl (meth) acrylates in which the alkyl group has 1 to 3 carbon atoms, alkyl (meth) acrylates in which the alkyl group has 13 to 18 carbon atoms, functional monomers, and the like.

Examples of the alkyl (meth) acrylate in which the alkyl group has 1 to 3 carbon atoms include: methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and the like. Examples of the alkyl (meth) acrylate in which the alkyl group has 13 to 18 carbon atoms include: tridecyl methacrylate, stearyl (meth) acrylate, and the like. Examples of the functional monomer include: hydroxyalkyl (meth) acrylates, glycerol dimethacrylate, glycidyl (meth) acrylate, 2-methacryloyloxyethyl isocyanate, (meth) acrylic acid, itaconic acid, maleic anhydride, crotonic acid, maleic acid, fumaric acid, and the like.

Among them, hydroxyl group-containing monomers such as hydroxyalkyl (meth) acrylate and glycerol dimethacrylate are preferable from the viewpoint of improving the storage modulus and the bulk strength of the pressure-sensitive adhesive layer at 180 ℃. That is, the acrylic copolymer preferably has a structural unit derived from a hydroxyl group-containing monomer. The hydroxyalkyl (meth) acrylate is not particularly limited, and more specifically, for example, 2-hydroxyethyl (meth) acrylate and the like can be mentioned.

In order to obtain the acrylic copolymer by copolymerizing the monomer mixture, the monomer mixture may be subjected to a radical reaction in the presence of a polymerization initiator. As a method for radically reacting the monomer mixture, that is, a polymerization method, conventionally known methods can be used, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, and bulk polymerization.

The lower limit of the weight average molecular weight (Mw) of the acrylic copolymer is preferably 50 ten thousand. When the weight average molecular weight of the acrylic copolymer is 50 ten thousand or more, the adhesive layer has an improved storage modulus and bulk strength at 180 ℃, and peeling of the adhesive layer can be suppressed when a shear load or a tilt load is applied. A more preferable lower limit of the weight average molecular weight is 60 ten thousand, a still more preferable lower limit is 80 ten thousand, and a still more preferable lower limit is 100 ten thousand.

The upper limit of the weight average molecular weight of the acrylic copolymer is not particularly limited, and a preferable upper limit is 200 ten thousand. If the weight average molecular weight of the acrylic copolymer is 200 ten thousand or less, the occurrence of interfacial peeling when a shear load or a tilt load is applied due to insufficient wettability of the interface of the pressure-sensitive adhesive layer can be suppressed. A more preferable upper limit of the weight average molecular weight of the acrylic copolymer is 190 ten thousand, a further more preferable upper limit is 180 ten thousand, and a further more preferable upper limit is 175 ten thousand.

The weight average molecular weight (Mw) is a weight average molecular weight in terms of polystyrene based on the standard of GPC (Gel Permeation Chromatography).

The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic copolymer has a preferred lower limit of 1.05 and a preferred upper limit of 5.0. When the Mw/Mn is 5.0 or less, the ratio of the low-molecular weight component is suppressed, the storage modulus and the bulk strength of the pressure-sensitive adhesive layer at 180 ℃ are improved, and the peeling of the pressure-sensitive adhesive layer when a shear load or an oblique load is applied can be suppressed. A more preferable upper limit of Mw/Mn is 4.5, a still more preferable upper limit is 4, and a still more preferable upper limit is 3.5.

At least one of the pressure-sensitive adhesive layers preferably contains a tackifier resin from the viewpoint of exhibiting high adhesive force. In this case, the pressure-sensitive adhesive layer may contain a tackifier resin on both surfaces or may contain a tackifier resin on only one surface.

Examples of the tackifier resin include: rosin resin, rosin ester resin, hydrogenated rosin resin, terpene phenol resin, coumarone indene resin, alicyclic saturated hydrocarbon resin, C5 petroleum resin, C9 petroleum resin, C5-C9 copolymer petroleum resin, and the like. These tackifying resins may be used alone or in combination of two or more. Among them, rosin-based resins and terpene-based resins are preferable, and rosin-based resins and terpene-based resins having a hydroxyl group are more preferable.

The softening temperature of the tackifier resin is preferably 70 ℃ at the lower limit and 170 ℃ at the upper limit. If the softening temperature is 70 ℃ or higher, the pressure-sensitive adhesive layer is prevented from becoming too soft and the holding force against shear load and tilt load is prevented from decreasing. If the softening temperature is 170 ℃ or lower, the occurrence of interfacial peeling when a shear load or a tilt load is applied due to insufficient wettability of the interface of the pressure-sensitive adhesive layer can be suppressed. A more preferred lower limit of the softening temperature is 120 ℃.

The softening temperature is a softening temperature measured by the ring and ball method of JIS K2207.

The preferable lower limit of the hydroxyl value of the tackifier resin is 25. When the hydroxyl value is equal to or higher than the above value, the occurrence of interfacial separation when a shear load or an oblique load is applied due to insufficient interaction at the interface of the pressure-sensitive adhesive layer can be suppressed. A more preferable lower limit of the hydroxyl value is 30. The upper limit of the hydroxyl value is not particularly limited.

The hydroxyl value can be measured according to JIS K1557 (phthalic anhydride method).

The content of the tackifier resin is not particularly limited, and a preferable lower limit is 10 parts by weight and a preferable upper limit is 40 parts by weight with respect to 100 parts by weight of the acrylic copolymer. When the content of the tackifier resin is 10 parts by weight or more, the adhesive strength of the pressure-sensitive adhesive layer is improved. If the content of the tackifier resin is 40 parts by weight or less, the pressure-sensitive adhesive layer can be prevented from becoming too hard and reducing the adhesive strength.

At least one of the pressure-sensitive adhesive layers preferably has a crosslinked structure formed by a crosslinking agent between main chains of resins (for example, the acrylic copolymer, the tackifier resin, and the like) constituting the pressure-sensitive adhesive layer. In this case, the pressure-sensitive adhesive layer may have a crosslinking agent added to both surfaces or may have a crosslinking agent added to only one surface. By adjusting the type and amount of the crosslinking agent, the storage modulus and gel fraction of the pressure-sensitive adhesive layer at 180 ℃ can be easily adjusted.

The crosslinking agent is not particularly limited, and examples thereof include an isocyanate-based crosslinking agent, an aziridine-based crosslinking agent, an epoxy-based crosslinking agent, and a metal chelate-based crosslinking agent. Among them, isocyanate-based crosslinking agents are preferable.

The amount of the crosslinking agent added is preferably 0.01 part by weight in the lower limit, 10 parts by weight in the upper limit, 0.1 part by weight in the lower limit, and 3 parts by weight in the upper limit, based on 100 parts by weight of the acrylic copolymer.

The above adhesive layer may contain a silane coupling agent for the purpose of improving the adhesive force. The silane coupling agent is not particularly limited, and examples thereof include epoxy silanes, acrylic silanes, methacrylic silanes, amino silanes, isocyanate silanes, and the like.

The above adhesive layer may contain a coloring material for the purpose of imparting light-shielding properties. The coloring material is not particularly limited, and examples thereof include carbon black, aniline black, and titanium oxide. Among these, carbon black is preferable in terms of being relatively inexpensive and chemically stable.

The pressure-sensitive adhesive layer may contain conventionally known fine particles such as inorganic fine particles, conductive fine particles, antioxidants, foaming agents, organic fillers, inorganic fillers, and the like, and additives, as required.

A preferred lower limit of the gel fraction of at least one of the pressure-sensitive adhesive layers is 15% by weight. In this case, the gel fraction on both sides of the pressure-sensitive adhesive layer may be within this range, or the gel fraction on only one side may be within this range. When the gel fraction is 15 wt% or more, the storage modulus and the bulk strength of the pressure-sensitive adhesive layer at 180 ℃ are improved, and the pressure-sensitive adhesive layer can be prevented from peeling off when a shear load or an oblique load is applied. A more preferable lower limit of the gel fraction is 30 wt%, and a further preferable lower limit is 40 wt%.

The upper limit of the gel fraction is not particularly limited, and a preferable upper limit is 80% by weight. If the gel fraction is 80 wt% or less, the occurrence of interfacial peeling when a shear load or a tilt load is applied due to insufficient wettability of the interface of the pressure-sensitive adhesive layer can be suppressed. A more preferable upper limit of the gel fraction is 75% by weight, a still more preferable upper limit is 70% by weight, and a still more preferable upper limit is 65% by weight.

The gel fraction of the pressure-sensitive adhesive layer can be measured by the following method.

The double-sided adhesive tape was cut into a flat rectangular shape of 50mm × 100mm to prepare a test piece. The test piece was immersed in ethyl acetate at 23 ℃ for 24 hours, then taken out of the ethyl acetate, and dried at 110 ℃ for 1 hour. The weight of the dried test piece was measured, and the gel fraction was calculated by the following formula (1). The test piece was not laminated with a release film for protecting the adhesive layer.

Gel fraction (% by weight) =100 × (W) ₂ -W ₀ )/(W ₁ -W ₀ ) (1)

(W ₀ : weight of foamed base material, W ₁ : weight of test piece before immersion, W ₂ : weight of the immersed and dried test pieceMeasuring)

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and the lower limit of the thickness of the pressure-sensitive adhesive layer on one side is preferably 20 μm, and the upper limit is preferably 100 μm. If the thickness of the pressure-sensitive adhesive layer is 20 μm or more, the adhesive strength of the pressure-sensitive adhesive layer is sufficient. If the thickness of the pressure-sensitive adhesive layer is 100 μm or less, the stress relaxation property of the foam base can sufficiently contribute to the stress relaxation property of the double-sided pressure-sensitive adhesive tape as a whole. A more preferable lower limit of the thickness of the pressure-sensitive adhesive layer is 25 μm, a more preferable upper limit is 80 μm, a further more preferable lower limit is 30 μm, a further more preferable upper limit is 70 μm, a further more preferable lower limit is 35 μm, and a further more preferable upper limit is 65 μm.

The thickness of the adhesive layer can be measured using a dial gauge (for example, "ABS digital INDICATOR") manufactured by Mitutoyo corporation.

The double-sided adhesive tape of the present invention may have, if necessary, other layers than the foam base and the adhesive layer.

The preferable lower limit of the strength of the double-sided adhesive tape of the present invention when the tape is elongated 5mm from the initial distance between the holding jigs in the tensile test is 1.5N. If the strength is 1.5N or more, the holding force of the double-sided adhesive tape against the shear load and the tilt load is further improved, and the handling property at the time of bonding is also further improved. A more preferable lower limit of the strength is 1.7N, and a further preferable lower limit is 2.2N.

For example, the strength of the 2 nd foamed resin layer may be increased by adjusting the expansion ratio of the 2 nd foamed resin layer to an appropriate range, and the strength may be adjusted to be within the range.

In the tensile test, the strength at the time of elongation of 5mm from the initial distance between the holding jigs can be measured by a method based on JIS K7161. Specifically, for example, a test piece was produced by punching the double-sided adhesive tape into a dumbbell shape using a punching blade "pull 3 dumbbell" manufactured by polymer counter corporation. The obtained test piece was stretched at a stretching speed of 50mm/min at 25 ℃ and a relative humidity of 50%, for example, using "Autograph AGS-X" manufactured by Shimadzu corporation. At this time, the initial inter-clamp distance was set to 60mm, and the strength at 5mm elongation from this distance (inter-clamp distance 65 mm) was read.

The 25% compressive strength of the double-sided pressure-sensitive adhesive tape of the present invention is not particularly limited, and the lower limit is preferably 20kPa, and the upper limit is preferably 70kPa. If the 25% compressive strength is 20kPa or more, the holding force of the double-sided pressure-sensitive adhesive tape with respect to the shear load and the tilt load is further improved. When the 25% compressive strength is 70kPa or less, the step followability and the stress relaxation property of both adhesive surfaces of the double-sided adhesive tape are further improved. A more preferable lower limit of the 25% compressive strength is 25kPa, a further more preferable lower limit is 27kPa, and a particularly preferable lower limit is 30kPa. A more preferable upper limit of the 25% compressive strength is 65kPa, a further more preferable upper limit is 60kPa, and a particularly preferable upper limit is 40kPa.

The 25% compressive strength of the double-sided adhesive tape of the present invention can be determined in accordance with JIS K6254: 2016, and performing the measurement.

The double-sided adhesive tape of the present invention preferably has a tensile breaking strength of 2N or more when a sample obtained by slicing the 1 st foamed resin layer is subjected to a 23 ℃ tensile test. If the tensile breaking strength is 2N or more, the double-sided pressure-sensitive adhesive tape can exhibit more excellent reworkability at room temperature. The tensile break strength is more preferably 3N or more, and still more preferably 4N or more.

The upper limit of the tensile break strength is not particularly limited, but from the viewpoint of the step following property and the stress relaxation property, the upper limit is preferably 20N, and more preferably 15N.

The double-sided adhesive tape of the present invention preferably has a tensile breaking elongation of 30mm or more when a sample obtained by slicing the 1 st foamed resin layer is subjected to a tensile test at 23 ℃. When the tensile breaking elongation is 30mm or more, the double-sided pressure-sensitive adhesive tape can exhibit more excellent reworkability at normal temperature. The tensile elongation at break is more preferably 50mm or more, and still more preferably 70mm or more.

The upper limit of the tensile elongation at break is not particularly limited, and is preferably 200mm from the viewpoint of exerting holding force against a shear load and a tilt load.

The method of performing the 23 ℃ tensile test on the sample obtained by slicing the above-mentioned 1 st foamed resin layer is as follows.

The double-sided adhesive tape was cut into a size of dumbbell No. 3 (center width 5 mm), and the No. 1 foamed resin layer (center portion) was cut into pieces with a feather blade. Thus, a sample of the adhesive layer/the 2 nd foamed resin layer/the 1 st foamed resin layer (about half thickness) was obtained.

Each sample was subjected to a tensile test at a tensile rate of 100mm/min, at a temperature of 23 ℃ and at a distance of 45mm between holding jigs, using "Autograph AGS-X" manufactured by Shimadzu corporation. The strength at break of the sample was taken as the tensile break strength, and the elongation at break of the sample was taken as the tensile break elongation.

In the double-sided adhesive tape of the present invention, the tensile breaking strength is preferably 1N or more when a sample obtained by slicing the 1 st foamed resin layer is subjected to a tensile test at 80 ℃. When the tensile breaking strength is 1N or more, the double-sided pressure-sensitive adhesive tape can exhibit more excellent reworkability at high temperatures. The tensile break strength is more preferably 1.5N or more.

The upper limit of the tensile break strength is not particularly limited, and is preferably 10N from the viewpoint of the step following property and the stress relaxation property.

In the double-sided pressure-sensitive adhesive tape of the present invention, the rate of decrease in tensile breaking strength when a sample obtained by slicing the 1 st foamed resin layer is subjected to a tensile test at 80 ℃ is preferably 70% or less. If the tensile breaking strength reduction rate is 70% or less, the double-sided adhesive tape can exhibit more excellent reworkability at high temperatures. The tensile strength reduction rate is more preferably 60% or less.

The lower limit of the tensile strength reduction rate is not particularly limited, but the lower the tensile strength reduction rate, the more preferable the lower the tensile strength reduction rate, the lower the tensile strength reduction rate is substantially 10% or so.

The method of performing the 80 ℃ tensile test on the sample obtained by slicing the first foamed resin layer 1 is as follows.

The double-sided adhesive tape was cut into a long strip of 5mm, and the 1 st foamed resin layer (central portion) was cut into pieces with a feather blade. Thus, a sample of the adhesive layer/the 2 nd foamed resin layer/the 1 st foamed resin layer (about half thickness) was obtained.

Each sample was subjected to a tensile test at a tensile rate of 100mm/min, a temperature of 80 ℃ and a distance between holding jigs of 10mm using an Autograph AGS-X manufactured by Shimadzu corporation. After the sample was set at a distance of 10mm between the holding jigs, the sample was left at 80 ℃ for 5 minutes, and then the measurement was started. The strength at break of the sample was taken as the tensile break strength. In addition, a value of 1- (tensile strength at break at 80 ℃ C./tensile strength at break at 23 ℃ C.) was calculated as a tensile strength reduction rate.

The thickness of the double-sided adhesive tape of the present invention is not particularly limited, and the lower limit is preferably 100 μm and the upper limit is preferably 3000 μm. When the thickness is 100 μm or more, the adhesive force of the double-sided pressure-sensitive adhesive tape becomes sufficient, and the stress relaxation property also becomes sufficient. When the thickness is 3000 μm or less, sufficient adhesion and fixation can be achieved by the double-sided pressure-sensitive adhesive tape, and the level difference following property on both adhesive surfaces becomes sufficient. A more preferable lower limit of the thickness is 250 μm, a more preferable upper limit is 1600 μm, a further preferable lower limit is 350 μm, a further preferable upper limit is 1500 μm, a further preferable lower limit is 500 μm, and a further preferable upper limit is 1300 μm.

The method for producing the double-sided adhesive tape of the present invention includes, for example, the following methods.

First, a solvent is added to an acrylic copolymer, a tackifier, a crosslinking agent, and the like to prepare a solution of the adhesive a. The pressure-sensitive adhesive layer is formed by applying the solution of the pressure-sensitive adhesive a to the release-treated surface of the release film, drying the solvent in the solution, and removing the solvent. The pressure-sensitive adhesive layer is pressure-bonded to the surface of the foam base material by a rubber roller or the like. In the same manner, a double-sided adhesive tape having an adhesive layer on both sides of a foam base and a release film covering the surface of the adhesive layer can be obtained by laminating an adhesive layer on the other side of the foam base.

The double-sided adhesive tape of the present invention is not particularly limited in its application, and can be used for fixing parts in electronic devices, for example. The electronic device is not particularly limited, and examples thereof include a television, a monitor, a portable electronic device, and an in-vehicle electronic device.

The double-sided adhesive tape of the present invention is suitable for fixing parts in a display device such as a television and a monitor, particularly a relatively large display device, and specifically for fixing a front cover plate to a housing in the display device. The double-sided pressure-sensitive adhesive tape of the present invention can exert a high holding force against a shear load and a tilt load, and therefore can be suitably used even when a member is fixed by a narrow-width double-sided pressure-sensitive adhesive tape in a relatively large-sized display device. The double-sided adhesive tape of the present invention may have a narrow width, and the width is not particularly limited, but the lower limit is preferably 0.5mm, the upper limit is preferably 20mm, the lower limit is more preferably 1mm, and the upper limit is more preferably 5mm. The shape of the double-sided adhesive tape of the present invention for these applications is not particularly limited, and examples thereof include a rectangular shape, a frame shape, a circular shape, an oval shape, and a ring shape.

The double-sided adhesive tape of the present invention can be used for interior equipment of vehicles, interior and exterior equipment of home appliances (e.g., TVs, monitors, air conditioners, refrigerators, etc.), and the like.

Effects of the invention

According to the present invention, a double-sided pressure-sensitive adhesive tape having high level difference following properties on both pressure-sensitive adhesive surfaces, capable of exerting high holding force against shear load and oblique load, excellent in reworkability of at least one pressure-sensitive adhesive surface, and further excellent in handling properties at the time of adhesion can be provided.

Drawings

Fig. 1 is a schematic view showing a 45 ° oblique holding force test of a double-sided adhesive tape.

Fig. 2 is a schematic diagram showing a shear holding force test of the double-sided adhesive tape.

Fig. 3 is a cross-sectional view schematically showing an example of the double-sided adhesive tape of the present invention.

Detailed Description

The mode of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(preparation of acrylic copolymer A)

159 parts by weight of ethyl acetate, 75 parts by weight of Butyl Acrylate (BA), 25 parts by weight of 2-ethylhexyl acrylate (2 EHA), 0.1 part by weight of 2-hydroxyethyl acrylate (HEA) and 5 parts by weight of acrylic acid (AAc) as solvents were charged in a reactor equipped with a thermometer, a stirrer and a cooling tube. After the nitrogen substitution, a reactor was placed in a water bath set at 60 ℃, and the reactor was heated to start the reflux. After 30 minutes from the start of reflux, 0.050 parts by weight of azobisisobutyronitrile as a polymerization initiator was charged into the reactor and reacted for 6 hours. Then, ethyl acetate was added to the reactor and the mixture was diluted and cooled to obtain a solution of an acrylic copolymer a.

The resulting acrylic copolymer A solution was diluted 50-fold with Tetrahydrofuran (THF), and the resulting diluted solution was filtered through a filter (material: polytetrafluoroethylene, pore size: 0.2 μm). The obtained filtrate was subjected to gel permeation chromatography (2690 Separations Model, made by Waters), GPC measurement was performed under conditions of a sample flow rate of 1 ml/min and a column temperature of 40 ℃, and polystyrene-equivalent molecular weight of the acrylic copolymer A was measured to determine weight average molecular weight (Mw). The weight average molecular weight (Mw) was 140 ten thousand. As the column, GPCKF-806L (manufactured by SHOWA DENKO K.K.) was used, and as the detector, a differential refractometer was used.

(preparation of acrylic copolymer B)

A solution of acrylic copolymer B was obtained in the same manner as acrylic copolymer a except that the solvent was changed to 100 parts by weight of ethyl acetate and 50 parts by weight of toluene, and the polymerization initiator was changed to 0.14 part by weight of azobisisobutyronitrile. The weight average molecular weight of the resulting acrylic copolymer B was 80 ten thousand.

(preparation of acrylic copolymer C)

A solution of acrylic copolymer C was obtained in the same manner as acrylic copolymer a except that the polymerization initiator was changed to azobisisobutyronitrile of 0.04 parts by weight. The weight average molecular weight of the resulting acrylic copolymer C was 160 ten thousand.

(preparation of acrylic copolymer D)

A solution of an acrylic copolymer D was obtained in the same manner as in the case of the acrylic copolymer A except that the loading of acrylic acid was changed to 3 parts by weight. The weight average molecular weight of the resulting acrylic copolymer D was 140 ten thousand.

(preparation of acrylic copolymer E)

50 parts by weight of ethyl acetate as a solvent was charged into a reactor equipped with a thermometer, a stirrer and a cooling tube, and after nitrogen substitution, the reactor was heated to start reflux. After 30 minutes from the boiling of the ethyl acetate, 0.20 part by weight of azobisisobutyronitrile was added as a polymerization initiator. A monomer mixture comprising 75 parts by weight of butyl acrylate, 25 parts by weight of 2-ethylhexyl acrylate, 0.1 part by weight of 2-hydroxyethyl acrylate and 3 parts by weight of acrylic acid was uniformly and slowly added dropwise thereto over 1 hour and 30 minutes to effect reaction. After the completion of the dropwise addition for 30 minutes, 0.15 parts by weight of azobisisobutyronitrile was added to conduct a polymerization reaction for further 5 hours, and ethyl acetate was added to the reactor and the mixture was cooled while being diluted to obtain a solution of an acrylic copolymer E. The weight average molecular weight of the resulting acrylic copolymer E was 40 ten thousand.

(styrene-acrylic block copolymer A)

A styrene-acrylic block copolymer a having the physical properties and composition shown in table 1 was prepared.

[ Table 1]

(example 1)

(1) Production of foamed base Material

As the foamable composition for forming the 1 st foamed resin layer (the central foamed resin layer), a composition comprising 100 parts by weight of a polyethylene resin (UBE polyethylene F420), 8.5 parts by weight of azodicarbonamide as a thermal decomposition type foaming agent, 1 part by weight of zinc oxide as a decomposition temperature regulator, and 0.5 part by weight of 2, 6-di-t-butyl-p-cresol as an antioxidant was used.

As the foamable composition for forming the 2 nd foamed resin layer (outermost layer), a composition comprising 100 parts by weight of a polyethylene resin (UBE polyethylene F420), 1.1 parts by weight of azodicarbonamide as a thermal decomposition type foaming agent, 1 part by weight of zinc oxide as a decomposition temperature adjusting agent, and 0.5 part by weight of 2, 6-di-t-butyl-p-cresol as an antioxidant was used.

The UBE POLYETHYLENE F420 is UBE POLYETHYLENE F420 (density: 0.920 g/cm) manufactured by UBE-MARUZEN POLYETHYLENE Co., ltd ³ )。

The foamable composition for forming the 1 st foamed resin layer (the central foamed resin layer) and the foamable composition for forming the 2 nd foamed resin layer (the outermost layer) were supplied to a multi-layer extruder for extrusion molding, and melt-kneaded at 130 ℃. After melt kneading, a foam roll in a long sheet form having a thickness of about 1.0mm, in which a layer formed of the foamable composition forming the 2 nd foamable resin layer (outermost layer) was laminated on both sides of a layer formed of the foamable composition forming the 1 st foamable resin layer (central foamable resin layer), was extruded.

Then, both surfaces of the long sheet-like foam roll were irradiated with an electron beam of 4.0Mrad having an acceleration voltage of 500kV to crosslink the foam roll. The crosslinked foam roll was continuously fed into a foaming furnace maintained at 250 ℃ by hot air and infrared heaters, heated and foamed, and stretched with the MD stretching ratio of 3.5 times and the TD stretching ratio of 3.5 times. Thus, a foam base was obtained in which the 2 nd foamed resin layer (outermost layer) -1 and the 2 nd foamed resin layer (outermost layer) -2 were laminated on both sides of the 1 st foamed resin layer (central foamed resin layer). The thickness of each foamed resin layer and the expansion ratio according to JIS K7222, and the thickness of the foam base and the expansion ratio according to JIS K6254: 2016 in 25% compressive strength. The measurement results are shown in table 2.

(2) Production of double-sided adhesive tape

To 100 parts by weight of the solid content of the acrylic copolymer A, 15 parts by weight of a polymerized rosin ester resin (Pensel D-135, softening point 135 ℃ C., hydroxyl value 45, manufactured by Mitsuwa CHEMICAL Co., ltd.) and 15 parts by weight of a terpene phenolic resin (YS POLYSTAR G150, softening point 150 ℃ C., hydroxyl value 135, manufactured by YASUHARA CHEMICAL Co., ltd.) were added. Further, 30 parts by weight of ethyl acetate (manufactured by Nippon Kagaku Co., ltd.) and 1.3 parts by weight of a solid content of an isocyanate-based crosslinking agent (manufactured by Nippon polyurethane Co., ltd.; trade name: coronate L45) were added thereto and stirred to obtain a binder solution.

A release film having a thickness of 75 μm was prepared, and a pressure-sensitive adhesive layer having a thickness of 50 μm was formed by applying a pressure-sensitive adhesive solution to the release-treated surface of the release film and drying the adhesive solution at 110 ℃ for 5 minutes. The pressure-sensitive adhesive layer was bonded to the surface of the foam base obtained above. Next, in the same manner, the same pressure-sensitive adhesive layer as described above was attached to the surface opposite to the foam base material after peeling off the PET separator. Then, the mixture was heated at 40 ℃ for 48 hours to effect aging. Thus, a double-sided pressure-sensitive adhesive tape covered with a release film was obtained.

(3) Determination of gel fraction

Gel fraction (% by weight) =100 × (W) ₂ -W ₀ )/(W ₁ -W ₀ ) (1)

(W ₀ : weight of foamed base material, W ₁ : weight of test piece before immersion, W ₂ : weight of test piece after dipping and drying

(4) Determination of storage modulus at 180 deg.C

The storage modulus of the adhesive layer at 180 ℃ was determined using a viscoelasticity measuring apparatus ("Rheometrics Dynamic analysis RDA-700", manufactured by Rheometrics) under conditions of a measurement temperature of-40 to 200 ℃, a temperature rise rate of 3 ℃/min and a frequency of 10 Hz.

(5) Measurement of Strength at 5mm elongation from the initial distance between holding jigs (tensile test)

The strength at 5mm elongation from the initial distance between the clamps was measured as follows based on JIS K7161.

The test piece was produced by punching a double-sided adhesive tape into a dumbbell shape using a "stretched dumbbell type 3" punch blade manufactured by polymer counter corporation. The obtained test piece was stretched at a stretching speed of 50mm/min at 25 ℃ and a relative humidity of 50% by using "Autograph AGS-X" manufactured by Shimadzu corporation. At this time, the initial inter-clamp distance was set to 60mm, and the strength when the specimen was extended by 5mm from this distance (inter-clamp distance 65 mm) was read.

(6) Determination of 25% compressive Strength

The 25% compressive strength of the double-sided pressure-sensitive adhesive tape is also based on JIS K6254: 2016, and performing the measurement.

(7) Tensile test at 23 ℃

The double-sided adhesive tape was cut into a size of dumbbell No. 3 (center width 5 mm), and the No. 1 foamed resin layer (center portion) was cut into pieces with a feather blade. Thus, the samples were divided into an adhesive layer/2 nd foamed resin layer (outermost layer) -1/1 st foamed resin layer (about half thickness) (sample set as "2 nd foamed resin layer (outermost layer) -1 side"), and a 1 st foamed resin layer (about half thickness)/2 nd foamed resin layer (outermost layer) -2/adhesive layer (sample set as "2 nd foamed resin layer (outermost layer) -2 side").

Each sample was subjected to a tensile test at a tensile rate of 100mm/min, a temperature of 23 ℃ and a distance between holding jigs of 45mm using "Autograph AGS-X" manufactured by Shimadzu corporation. The strength at break of the sample was taken as the tensile break strength, and the elongation at break of the sample was taken as the tensile break elongation.

(8) Tensile test at 80 ℃

The double-sided adhesive tape was cut into a long strip of 5mm, and the No. 1 foamed resin layer (central portion) was cut into pieces with a feather blade. Thus, the samples were divided into an adhesive layer/2 nd foamed resin layer (outermost layer) -1/1 st foamed resin layer (about half thickness) (sample set as "2 nd foamed resin layer (outermost layer) -1 side"), and a 1 st foamed resin layer (about half thickness)/2 nd foamed resin layer (outermost layer) -2/adhesive layer (sample set as "2 nd foamed resin layer (outermost layer) -2 side").

Each sample was subjected to a tensile test at a tensile rate of 100mm/min, a temperature of 80 ℃ and a distance between holding jigs of 10mm using an Autograph AGS-X manufactured by Shimadzu corporation. After the sample was set at a distance of 10mm between the grips, the measurement was started after leaving the sample at 80 ℃ for 5 minutes. The strength at break of the sample was taken as the tensile break strength. In addition, a value of 1- (tensile strength at break at 80 ℃ C./tensile strength at break at 23 ℃ C.) was calculated as a tensile strength reduction rate.

(examples 2 to 6 and 11 to 14)

A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in example 1, except that the foam base was changed as shown in table 2. The thickness of the foamed resin layer is adjusted by adjusting the thickness and the MD and TD stretching ratios in the multilayer extrusion, and the expansion ratio of the foamed resin layer is adjusted by adjusting the amount of the thermal decomposition type foaming agent.

(examples 7 to 10)

A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in example 1, except that the pressure-sensitive adhesive layer was changed as shown in table 2. In example 6, the acrylic copolymer B was used, and the amount of the crosslinking agent was 1.9 parts by weight as a solid content. In example 7, the acrylic copolymer C was used, and the amount of the crosslinking agent was 1.1 parts by weight as a solid content. In both examples 8 and 9, the acrylic copolymer D was used, but the gel fraction was changed by setting the amount of the crosslinking agent to 1.4 parts by weight of the solid content in example 8 and to 1.1 parts by weight of the solid content in example 9.

Comparative example 1

In the case of "(1) production of a foam base", the foamable composition forming the 2 nd foamed resin layer (outermost layer) is not used, and only the foamable composition forming the 1 st foamed resin layer (central foamed resin layer) is used. A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in example 1, except that a polyethylene terephthalate (PET) sheet and a styrene-acrylic copolymer sheet were laminated on each side of the obtained 1 st foamed resin layer (the central foamed resin layer).

Specifically, in "(1) production of foam base material", first, only the 1 st foamed resin layer (central foamed resin layer) is formed. Subsequently, a binder solution containing acrylic copolymer A was applied to the surface of a polyethylene terephthalate (PET) sheet (X30, manufactured by Toray corporation) having a thickness of 50 μm, and dried at 110 ℃ for 5 minutes, thereby forming a binder layer having a thickness of 20 μm. The obtained 1 st foamed resin layer (the central foamed resin layer) was laminated on the pressure-sensitive adhesive layer to obtain a laminate composed of a polyethylene terephthalate (PET) sheet, a pressure-sensitive adhesive layer, and the 1 st foamed resin layer (the central foamed resin layer).

Further, 5 parts by weight of a crosslinking agent was added to an ethyl acetate solution of the styrene-acrylic block copolymer A per 100 parts by weight of the styrene-acrylic block copolymer A, and the resulting mixture was coated on a polyethylene terephthalate (PET) sheet having a thickness of 50 μm whose surface was subjected to a mold release treatment, and dried to obtain an uncrosslinked resin film having a thickness of 40 μm. As the crosslinking agent, a product name "Coronate L45" manufactured by Nippon polyurethane Co., ltd. An uncrosslinked resin film was laminated on the 1 st foamed resin layer (central foamed resin layer) side of the laminate composed of the polyethylene terephthalate (PET) sheet/adhesive layer/1 st foamed resin layer (central foamed resin layer), to obtain a laminate composed of the polyethylene terephthalate (PET) sheet/adhesive layer/1 st foamed resin layer (central foamed resin layer)/uncrosslinked resin film. Next, the uncrosslinked resin film was heated at 40 ℃ for 48 hours to thermally crosslink the uncrosslinked resin film, thereby obtaining a foamed base material composed of a polyethylene terephthalate (PET) sheet/an adhesive layer/the 1 st foamed resin layer (the central foamed resin layer)/a styrene-acrylic copolymer sheet.

Comparative example 2

A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in example 1 except that the foamable composition for forming the 2 nd foamed resin layer (outermost layer) was not used in the "(1) production of foamed base material", and only the foamable composition for forming the 1 st foamed resin layer (central foamed resin layer) was used, and the styrene-acrylic copolymer sheet was laminated on both sides of the obtained 1 st foamed resin layer (central foamed resin layer).

Specifically, in "(1) production of foam base", first, only the 1 st foamed resin layer (the central foamed resin layer) is formed. Next, a crosslinking agent was added in an ethyl acetate solution of the styrene-acrylic block copolymer A in an amount of 5 parts by weight based on 100 parts by weight of the styrene-acrylic block copolymer A, and the resulting mixture was coated on a polyethylene terephthalate (PET) sheet having a thickness of 50 μm and subjected to a releasing treatment, and dried to obtain an uncrosslinked resin film having a thickness of 40 μm. As the crosslinking agent, a product name "Coronate L45" manufactured by Nippon polyurethane Co., ltd.

An uncrosslinked resin film was laminated on the 1 st foamed resin layer (the central foamed resin layer) to obtain a laminate composed of the uncrosslinked resin film/the 1 st foamed resin layer (the central foamed resin layer). Subsequently, the resultant was heated at 40 ℃ for 48 hours to thermally crosslink the uncrosslinked resin film, thereby obtaining a laminate composed of the styrene-acrylic copolymer sheet/the 1 st foamed resin layer (the central foamed resin layer).

Further, the uncrosslinked resin film prepared in the same manner was laminated on the 1 st foamed resin layer (central foamed resin layer) side of the laminate composed of the styrene-acrylic copolymer sheet/the 1 st foamed resin layer (central foamed resin layer), to obtain a laminate composed of the styrene-acrylic copolymer sheet/the 1 st foamed resin layer (central foamed resin layer)/the uncrosslinked resin film. Subsequently, the uncrosslinked resin film was heated at 40 ℃ for 48 hours to thermally crosslink the uncrosslinked resin film, thereby obtaining a foamed base material composed of a styrene-acrylic copolymer sheet/the 1 st foamed resin layer (central foamed resin layer)/a styrene-acrylic copolymer sheet.

Comparative example 3

A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in example 1 except that the foamable composition for forming the 2 nd foamed resin layer (outermost layer) was not used in the "(1) preparation of foam base material", and only the foamable composition for forming the 1 st foamed resin layer (central foamed resin layer) was used, and a Polyethylene (PE) sheet was laminated on both sides of the obtained 1 st foamed resin layer (central foamed resin layer).

Specifically, in "(1) production of foam base material", first, only the 1 st foamed resin layer (central foamed resin layer) is formed. A release film having a thickness of 75 μm was prepared, and a pressure-sensitive adhesive layer having a thickness of 6 μm was formed by applying a pressure-sensitive adhesive solution containing acrylic copolymer A to the release-treated surface of the release film and drying at 110 ℃ for 5 minutes. Then, the pressure-sensitive adhesive layer was bonded to the surface of a low-density Polyethylene (PE) sheet having a thickness of 40 μm to obtain a laminate composed of the pressure-sensitive adhesive layer and the low-density Polyethylene (PE) sheet. The release film of the pressure-sensitive adhesive layer in the laminate composed of the pressure-sensitive adhesive layer/low-density Polyethylene (PE) sheet was peeled off and bonded to the 1 st foamed resin layer (the central foamed resin layer). In the same manner, an adhesive layer/low-density Polyethylene (PE) sheet was also bonded to the surface opposite to the 1 st foamed resin layer (the central foamed resin layer). Then, the mixture was heated at 40 ℃ for 48 hours to effect aging. A foam base material composed of a Polyethylene (PE) sheet/adhesive layer/1 st foamed resin layer (central foamed resin layer)/adhesive layer/Polyethylene (PE) sheet was obtained.

Comparative example 4

A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in example 2 except that the foamable composition for forming the 2 nd foamed resin layer (outermost layer) was not used in the "(1) preparation of foam base material", and only the foamable composition for forming the 1 st foamed resin layer (central foamed resin layer) was used, and a polyethylene terephthalate (PET) sheet was laminated on one side of the obtained 1 st foamed resin layer (central foamed resin layer).

Specifically, in "(1) production of foam base material", first, only the 1 st foamed resin layer (central foamed resin layer) is formed. Subsequently, a pressure-sensitive adhesive layer having a thickness of 20 μm was formed by applying a pressure-sensitive adhesive solution containing acrylic copolymer A to the surface of a polyethylene terephthalate (PET) sheet (X30, manufactured by Toray corporation) having a thickness of 50 μm, and drying the sheet at 110 ℃ for 5 minutes. The obtained 1 st foamed resin layer (the central foamed resin layer) was laminated on the pressure-sensitive adhesive layer to obtain a foam base material composed of a polyethylene terephthalate (PET) sheet, a pressure-sensitive adhesive layer, and the 1 st foamed resin layer (the central foamed resin layer).

Comparative example 5

A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in example 2 except that the foamable composition for forming the 2 nd foamed resin layer (outermost layer) was not used in the "(1) preparation of foam base" and only the foamable composition for forming the 1 st foamed resin layer (central foamed resin layer) was used.

Comparative examples 6 to 8

A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in example 1, except that the pressure-sensitive adhesive layer was changed as shown in table 3. In comparative example 6, the acrylic copolymer E was used, but the gel fraction was changed by setting the amount of the crosslinking agent to 2.5 parts by weight of the solid content. In comparative example 7, the acrylic copolymer D was used in the same manner as in examples 8 and 9, but the gel fraction was changed by setting the amount of the crosslinking agent to 0.7 parts by weight of the solid content.

Comparative example 9

In the case of "(1) production of a foam base", the foamable composition forming the 2 nd foamed resin layer (outermost layer) is not used, and only the foamable composition forming the 1 st foamed resin layer (central foamed resin layer) is used. A double-sided adhesive tape was obtained in the same manner as in example 1, except that acrylic copolymer sheets were laminated on both sides of the obtained 1 st foamed resin layer (the central foamed resin layer).

Specifically, in "(1) production of foam base material", first, only the 1 st foamed resin layer (central foamed resin layer) is formed. Then, 100 parts by weight of ethyl acetate was added to 45 parts by weight of LA2270, a product of Colorado, and the mixture was stirred to obtain a solution. The obtained solution was coated on a polyethylene terephthalate (PET) sheet having a thickness of 50 μm whose surface was subjected to a releasing treatment, and dried at 110 ℃ for 5 minutes to obtain a resin film having a thickness of 40 μm. The exposed surface of the resin film was bonded to one surface of the 1 st foamed resin layer (the central foamed resin layer). A resin film having a thickness of 40 μm was prepared again in the same manner as described above, and the exposed surface of the resin film was bonded to the surface opposite to the 1 st foamed resin layer (the central foamed resin layer) to obtain a foamed base material.

< evaluation >

The double-sided adhesive tapes obtained in examples and comparative examples were evaluated as follows. The results are shown in tables 4 to 5.

(1) Evaluation of following Performance for height difference

A single-sided pressure-sensitive adhesive tape (125 mm. Times.20 mm, thickness 300 μm) was attached to a glass plate (125 mm. Times.50 mm, thickness 1.5 mm) to prepare a step having a height of 300 μm. The double-sided adhesive tape was cut into a size of 25mm × 50mm, and one side was lined with a polyethylene terephthalate (PET) sheet having a thickness of 23 μm. The other surface of the double-sided adhesive tape was attached to the surface of the glass plate on which the step difference was formed, and a 2kg rubber roller was reciprocated 1 time from the glass plate side and pressure-bonded thereto. The air penetration distance from the stepped portion was measured and evaluated according to the following criteria.

A: the air bite distance is less than 700 μm

B: the air biting distance is 700 μm or more and less than 800 μm

C: the air bite distance is 800 μm or more and less than 900 μm

D: the air biting distance is 900 μm or more and less than 1000 μm

E: the air bite distance is 1000 μm or more

(2) Evaluation of holding force

(2-1) 45 degree inclined holding force test

Fig. 1 shows a schematic diagram illustrating a 45 ° oblique holding force test of a double-sided adhesive tape.

The obtained double-sided pressure-sensitive adhesive tape 18 was cut into a size of 25mm × 25mm, the pressure-sensitive adhesive layer on the 2 nd foamed resin layer (outermost layer) -2 side was bonded to the glass plate 17, and a 2kg rubber roller was reciprocated once on the double-sided pressure-sensitive adhesive tape 18 at a speed of 300 mm/min. Next, the adhesive layer on the 2 nd foamed resin layer (outermost layer) -1 side of the double-sided adhesive tape 18 was bonded to the SUS plate 16, and pressure-bonded by pressing with a 5kg weight for 10 seconds from the SUS plate 16 side, and then left to stand in an environment of 23 ℃ and a relative humidity of 50% for 24 hours to prepare a test sample.

The test sample was attached with a 1kg weight 15 to the center of the SUS plate 16 at 60 ℃ and a relative humidity of 90% so as to apply a load to the double-sided adhesive tape 18 and the SUS plate 16, and held while being inclined at 45 °, and the time until the weight 15 fell (falling time) was measured and evaluated according to the following criteria.

O: the falling time is more than 250 hours

And (delta): the falling time is more than 50 hours and less than 250 hours

X: the falling time is less than 50 hours

(2-2) shear holding force test

Fig. 2 shows a schematic diagram illustrating a shear holding force test of the double-sided adhesive tape. Fig. 2 (a) is a front view, and fig. 2 (b) is a side view.

As shown in fig. 2 (a) and (b), the pressure-sensitive adhesive layer on the 2 nd foamed resin layer (outermost layer) -2 side of the double-sided pressure-sensitive adhesive tape 3 is lined with a PET film (# 50) 4. The adhesive layer on the 2 nd foamed resin layer (outermost layer) -1 side of the double-sided adhesive tape 3 was bonded to the SUS plate 1 and the SUS plate 2, and a test sample having a bonding area of 25mm × 25mm between the SUS plate 1 and the double-sided adhesive tape 3 was prepared. Test samples were made as follows.

First, SUS plate 1 (thickness of 2 mm. Times.50 mm. Times.70 mm, the surface of SUS304 steel plate prescribed in JIS-G-4305 was uniformly polished with water-resistant abrasive paper No. 360) and SUS plate 2 (thickness of 1 mm. Times.30 mm. Times.50 mm, not polished) were prepared. The SUS plate 1 and the SUS plate 2 were washed with ethanol and then sufficiently dried. The double-sided adhesive tape 3 was cut to a width of 25mm × a length of 140mm, the release film on one side was peeled off, and the PET film (# 50) 4 was bonded to the exposed adhesive layer. Next, the release film on the other surface was peeled off, the exposed end portion of the pressure-sensitive adhesive layer was attached to the SUS plate 1 so as not to allow air bubbles to enter, and a 2kg rubber roller was reciprocated 1 time at a speed of 10 mm/sec to be pressure-bonded. At this time, the SUS plate 1 and the double-sided adhesive tape 3 were attached so as to overlap by 30 mm. Further, the end of the adhesive layer opposite to the end adhered to the SUS plate 1 was adhered to the SUS plate 2, and a 2kg rubber roller was reciprocated 1 time at a speed of 10 mm/sec to be pressed. At this time, the double-sided adhesive tape 3 is disposed so as to cover the front and back surfaces of the SUS plate 2. Then, the through-hole 5 was provided in the double-sided adhesive tape 3 together with the SUS plate 2, and the double-sided adhesive tape 3 was cut so that the area of the joint between the SUS plate 1 and the double-sided adhesive tape 3 became 25mm × 25 mm.

The test samples prepared as described above were left in a thermostatic bath of 50 ℃ and 80% RH for 24 hours, then a 2kg weight 6 was attached to the through-hole 5 under the same environment, and the deflection after 200 hours was measured and evaluated according to the following criteria. The shear holding power of the pressure-sensitive adhesive layer on the 2 nd foamed resin layer (outermost layer) -2 side of the double-sided pressure-sensitive adhesive tape 3 was also evaluated in the same manner.

O: deflection after 200 hours is less than 2mm

And (delta): the offset after 200 hours is more than 2mm and less than 10mm

X: the offset after 200 hours is 10mm or more

(3) Evaluation of 23 ℃ reworkability and 80 ℃ reworkability

The double-sided adhesive tape was cut into a size of 5mm × 100mm, and one side was attached to a glass plate. The other surface of the double-sided adhesive tape was also bonded to a glass plate to prepare a glass plate/double-sided adhesive tape/glass plate laminate, and the laminate was pressure-bonded under a weight of 5kg for 10 seconds. The 1 st foamed resin layer (central portion) of the resulting laminate was sliced with a feather blade. Thus, the glass plate/adhesive layer/2 nd foamed resin layer (outermost layer) -1/1 st foamed resin layer (about half thickness) (sample "2 nd foamed resin layer (outermost layer) -1 side"), and the 1 st foamed resin layer (about half thickness)/2 nd foamed resin layer (outermost layer) -2/adhesive layer/glass plate (sample "2 nd foamed resin layer (outermost layer) -2 side") were separated.

In the evaluation of the reworkability at 23 ℃, each sample was left at 23 ℃ for 4 days, and then the double-sided adhesive tape portion was peeled off from the glass plate by hand at a high speed.

In the evaluation of the reworkability at 80 ℃, each sample was left at 80 ℃ for 1 day, and immediately after being taken out, the double-sided adhesive tape portion was peeled off from the glass plate by hand at high speed.

Very good: no adhesive residue, no breakage of the double-sided adhesive tape portion, and ability to rework the glass sheet o: the double-sided adhesive tape is not broken even if the adhesive remains, and the glass plate can be reprocessed

X: the double-sided adhesive tape is broken and the glass plate cannot be reprocessed

Based on the evaluation results of the sample on the 2 nd foamed resin layer (outermost layer) -1 side and the sample on the 2 nd foamed resin layer (outermost layer) -2 side, the reworkability at 23 ℃ and the reworkability at 80 ℃ were comprehensively evaluated in accordance with the following criteria.

Very good: the evaluation results of the sample on the 2 nd foamed resin layer (outermost layer) -1 side and the sample on the 2 nd foamed resin layer (outermost layer) -2 side were all very good

O: at least one of the evaluation results of the sample on the 2 nd foamed resin layer (outermost layer) -1 side and the sample on the 2 nd foamed resin layer (outermost layer) -2 side was excellent or good

And (delta): at least one of the evaluation results of the sample on the 2 nd foamed resin layer (outermost layer) -1 side and the sample on the 2 nd foamed resin layer (outermost layer) -2 side was O

X: the evaluation results of the sample on the 2 nd foamed resin layer (outermost layer) -1 side and the sample on the 2 nd foamed resin layer (outermost layer) -2 side were found in

(4) Evaluation of handling Properties

The double-sided adhesive tape thus obtained was cut into a size of 3mm in width × 10mm in length, and the double-sided adhesive tape was stretched at 1N for 10 seconds at 25 ℃ under a relative humidity of 50% using Autograph AGS-X (manufactured by Shimadzu corporation) to measure the elongation (mm). Evaluation was performed according to the following criteria. The initial load change was set to 1N/sec.

O: the elongation is less than 10mm.

X: the elongation is 10mm or more.

(5) Evaluation of Presence or absence of Break

The obtained double-sided adhesive tape was cut into a size of 100mm × 300mm, and wound around a paper core having a diameter of 3 inches so that the 2 nd foamed resin layer (outermost layer) -2 side was inside, to obtain a roll.

The double-sided pressure-sensitive adhesive tape was pulled out from the obtained roll, and then visually observed, and evaluated according to the following criteria.

O: no break was confirmed.

X: breakage was confirmed.

[ Table 2]

[ Table 3]

[ Table 4]

[ Table 5]

Industrial applicability

According to the present invention, a double-sided pressure-sensitive adhesive tape can be provided which has high level difference following properties on both pressure-sensitive adhesive surfaces, can exert high holding force against shear load and oblique load, has excellent reworkability on at least one pressure-sensitive adhesive surface, and further has excellent handling properties at the time of adhesion.

Description of the reference numerals

1. 2 SUS plate

3. Test piece (double-sided adhesive tape)

4 PET film (# 50)

5. Through hole

6. Weight (3 kg)

7. Double-sided adhesive tape

8. Foamed base material

91. 92 adhesive layer

10. The 1 st foamed resin layer

11. 12 nd 2 nd foamed resin layer

15. Weight (1 kg)

16 SUS plate

17. Glass plate

18. Double-sided adhesive tape

Claims

1. A double-sided adhesive tape comprising a foam base and adhesive layers laminated on both sides of the foam base,

the foam base material comprises a 1 st foam resin layer and a2 nd foam resin layer laminated on at least one surface of the 1 st foam resin layer, wherein the 2 nd foam resin layer has a lower expansion ratio than the 1 st foam resin layer,

at least one of the adhesive layers has a storage modulus at 180 ℃ of 11000Pa or more.

2. The double-sided adhesive tape according to claim 1, wherein the foam base does not have another layer between the 1 st foamed resin layer and the 2 nd foamed resin layer.

3. The double-sided adhesive tape according to claim 1 or 2, wherein the double-sided adhesive tape has a strength of 1.5N or more when elongated 5mm from an initial distance between holding jigs in a tensile test.

4. The double-sided adhesive tape according to claim 1, 2 or 3, wherein the foam base has a 25% compressive strength of 200kPa or less.

5. The double-sided adhesive tape according to claim 1, 2, 3 or 4, wherein the double-sided adhesive tape has a tensile break strength of 2N or more when a 23 ℃ tensile test is performed on a sample obtained by slicing the 1 st foamed resin layer, and has a tensile break strength of 1N or more and a tensile break strength reduction rate of 70% or less when an 80 ℃ tensile test is performed on a sample obtained by slicing the 1 st foamed resin layer.

6. The double-sided adhesive tape according to claim 1, 2, 3, 4 or 5, wherein the double-sided adhesive tape has a tensile breaking elongation of 30mm or more when a sample obtained by slicing the 1 st foamed resin layer is subjected to a tensile test at 23 ℃.

7. The double-sided adhesive tape according to claim 1, 2, 3, 4, 5 or 6, wherein the 1 st foamed resin layer is a polyolefin foamed resin layer, and the expansion ratio is 5cm ³ More than g and 30cm ³ The ratio of the carbon atoms to the carbon atoms is below g.

8. The double-sided adhesive tape according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the foam base has the 2 nd foamed resin layer on both sides of the 1 st foamed resin layer.

9. The double-sided adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein at least one of the adhesive layers contains an acrylic copolymer having a weight average molecular weight of 50 ten thousand or more, and the gel fraction is 15% by weight or more.

10. The double-sided adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9, wherein the 2 nd foamed resin layer is a polyolefin foamed resin layer.

11. The double-sided adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, wherein the width of the double-sided adhesive tape is 20mm or less.

12. The double-sided adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the thickness of the double-sided adhesive tape is 100 μm or more and 3000 μm or less.