JP2021113297A - Adhesive tape and manufacturing method thereof - Google Patents

Abstract

To provide adhesive tape superior in long-term stability of sticking performance even if containing air bubbles, and to provide a manufacturing method thereof.SOLUTION: Adhesive tape 10 comprises a base material 11 and an adhesive layer 20 provided on the surface of the base material 11 and containing air bubble 21 inside. The surface roughness (Rz) of an external surface 20A of the adhesive layer 20 is equal to or less than 40 μm. A manufacturing method of the adhesive tape includes: a step of laminating an adhesive composition containing expandable particle on the surface of the base material; and a step of heating the laminate so that the adhesive composition side surface temperature of the laminate lowers in comparison with the base material side surface temperature of the laminate, and foaming at least the expandable particle in the base material side of the adhesive composition.SELECTED DRAWING: Figure 1

Description

The present invention relates to an adhesive tape having air bubbles inside the adhesive layer and a method for producing the same.

Adhesive tapes are used in various fields. For example, kraft paper-based kraft tapes are widely used as tapes used for packaging and the like. Conventionally, in adhesive tapes such as kraft tape, as a method of ensuring adhesive strength with a small amount of adhesive, air bubbles are contained in the adhesive layer to increase the thickness.

As a method of incorporating air bubbles in the pressure-sensitive adhesive layer, for example, as disclosed in Patent Document 1, a volatile substance is permeated into a tape base material and gasified to gasify the tape base material to form fine closed cells in the pressure-sensitive adhesive layer. The method of forming inside is known. Further, as disclosed in Patent Document 2, a pressure-sensitive adhesive containing heat-expandable microcapsules is applied to a base material and then heated to expand the heat-expandable microcapsules to form bubbles inside the pressure-sensitive adhesive layer. The method is also known.

Special Fair 2-29705 Gazette Japanese Patent No. 2709353

Some of the adhesive tapes containing air bubbles in the adhesive layer may have poor adhesiveness to the adherend after a long period of time after being manufactured, or may be adhered to the adherend for a long time. There was something that came off. Therefore, an object of the present invention is to provide an adhesive tape having excellent long-term stability of adhesive performance even if air bubbles are contained, and a method for producing the adhesive tape.

The gist of the present invention is as follows [1] to [11].
[1] Adhesive having a base material and a pressure-sensitive adhesive layer provided on the surface of the base material and containing air bubbles inside, and having a surface roughness (Rz) of 40 μm or less on the outer surface of the pressure-sensitive adhesive layer. tape.
[2] The pressure-sensitive adhesive layer includes a foamed pressure-sensitive adhesive layer containing air bubbles inside and a non-foamed pressure-sensitive adhesive layer containing no air bubbles inside on the opposite side of the foamed pressure-sensitive adhesive layer to the base material side. The adhesive tape according to [1].
[3] The adhesive tape according to the above [1] or [2], wherein the bubbles include a first bubble arranged at a position away from the surface of the base material.
[4] The adhesive tape according to the above [3], wherein the first bubble is a bubble derived from foamable particles.
[5] The adhesive tape according to the above [3], wherein the first bubble is a bubble formed inside a hollow particle.
[6] The adhesive tape according to any one of [3] to [5] above, wherein the bubbles further include a second bubble that comes into contact with the surface of the base material.
[7] The adhesive tape according to any one of the above [1] to [6], wherein the foaming ratio of the pressure-sensitive adhesive layer measured by a compression test is 1.7 times or more.
[8] The adhesive tape according to any one of the above [1] to [7], wherein the average bubble diameter of the bubbles contained in the pressure-sensitive adhesive layer is 55 μm or less.
[9] The base material comprises a paper base material and a resin layer provided on one surface of the paper base material, and the pressure-sensitive adhesive layer is provided on the other surface of the paper base material. The adhesive tape according to any one of 1] to [8].
[10] The adhesive tape according to the above [9], wherein the paper base material is kraft paper and the resin layer is a polyethylene-based resin layer.
[11] The step of laminating the pressure-sensitive adhesive composition containing the foamable particles on the surface of the base material, and the temperature of the surface of the obtained laminated body on the base material side, the pressure-sensitive adhesive composition side of the laminated body. A method for producing an adhesive tape, which comprises a step of heating the laminate so that the temperature of the surface of the pressure-sensitive adhesive composition is lowered, and at least foaming the foamable particles on the substrate side of the pressure-sensitive adhesive composition.

According to the present invention, it is possible to provide an adhesive tape having excellent long-term stability of adhesive performance even if it has air bubbles, and a method for producing the adhesive tape.

It is a schematic cross-sectional view which shows the adhesive tape which concerns on one Embodiment of this invention. It is a schematic cross-sectional view which shows the adhesive tape which showed the base material in detail in one Embodiment of this invention. It is a schematic cross-sectional view which shows the modification of the adhesive tape which concerns on one Embodiment of this invention. It is a schematic cross-sectional view which shows the modification of the adhesive tape which concerns on one Embodiment of this invention. It is a schematic cross-sectional view which shows the modification of the adhesive tape which concerns on one Embodiment of this invention. It is a schematic diagram which shows the method of measuring the foaming ratio by a compression test.

Hereinafter, the adhesive tape according to the embodiment of the present invention will be described in detail with reference to the drawings. In the present embodiment, as shown in FIG. 1, the adhesive tape 10 includes a base material 11 and a pressure-sensitive adhesive layer 20 provided on one surface 11A of the base material 11 and having air bubbles 21 inside.

[Adhesive layer]
The surface roughness (Rz) of the outer surface 20A of the pressure-sensitive adhesive layer 20 is 40 μm or less. If the surface roughness (Rz) of the outer surface 20A of the pressure-sensitive adhesive layer 20 is larger than 40 μm, the long-term stability of the adhesive performance of the pressure-sensitive adhesive tape 10 may deteriorate. The following reasons are not limited to the present invention, but if the surface roughness (Rz) of the outer surface 20A of the pressure-sensitive adhesive layer 20 is larger than 40 μm, the long-term stability of the adhesive performance of the adhesive tape 10 deteriorates as follows. It is considered that this is due to the reason.
When the surface roughness (Rz) of the outer surface 20A of the pressure-sensitive adhesive layer 20 is larger than 40 μm, it is considered that bubbles having a large bubble diameter are present in the vicinity of the outer surface 20A of the pressure-sensitive adhesive layer 20. When the bubbles are present in the vicinity of the outer surface 20A of the pressure-sensitive adhesive layer 20, the bubbles are likely to break. Further, when the bubble diameter of the bubble is large, the bubble is more likely to break. Therefore, if the surface roughness (Rz) of the outer surface 20A of the pressure-sensitive adhesive layer 20 is larger than 40 μm, air bubbles will break during the long-term storage of the pressure-sensitive adhesive tape 10, and the pressure-sensitive adhesive tape 10 will adhere. It is thought that the long-term stability of performance will deteriorate.

From the viewpoint of long-term stability of the adhesive performance of the adhesive tape 10, the surface roughness (Rz) of the outer surface 20A of the pressure-sensitive adhesive layer 20 is preferably 30 μm or less, more preferably 25 μm or less, still more preferably 20 μm. It is as follows. The lower limit of the range of the surface roughness (Rz) of the outer surface 20A of the pressure-sensitive adhesive layer 20 is not particularly limited, but is, for example, 0 μm or more. The surface roughness (Rz) of the outer surface 20A of the pressure-sensitive adhesive layer 20 means a value measured based on the method described in Examples described later.

The surface roughness (Rz) of the outer surface 20A of the pressure-sensitive adhesive layer 20 can be reduced to 40 μm or less by not allowing bubbles to exist near the outer surface of the pressure-sensitive adhesive layer 20, or by reducing the bubble diameter of the bubbles even if they do exist. can do. By not allowing air bubbles to exist near the outer surface of the pressure-sensitive adhesive layer 20, it is possible to prevent the air bubbles existing near the outer surface from bursting and deteriorating the adhesive performance of the adhesive tape. As a result, the adhesive tape 10 is not easily peeled off even if it is attached to the adherend for a long time. Further, by reducing the bubble diameter of the bubbles near the outer surface of the pressure-sensitive adhesive layer 20, even if a convex portion is generated on the outer surface of the pressure-sensitive adhesive layer due to the bubbles existing near the outer surface, the outer surface of the pressure-sensitive adhesive is covered. The surface roughness (Rz) is also reduced, and can be 40 μm or less. In addition, small bubbles are hard to break.

The pressure-sensitive adhesive layer 20 may include a foamed pressure-sensitive adhesive layer 23 containing air bubbles inside and a non-foamed pressure-sensitive adhesive layer 22 containing no air bubbles inside on the opposite side of the foamed pressure-sensitive adhesive layer 23 from the base material 11 side. preferable. This makes it easy to set the surface roughness (Rz) of the outer surface 20A of the pressure-sensitive adhesive layer 20 to 40 μm or less. As a result, the long-term stability of the adhesive performance of the adhesive tape 10 is improved. Since the foamed pressure-sensitive adhesive layer 23 and the non-foamed pressure-sensitive adhesive layer 22 usually differ only in the presence or absence of air bubbles, the interface between the foamed pressure-sensitive adhesive layer 23 and the non-foaming pressure-sensitive adhesive layer 22 is not clear.

In the pressure-sensitive adhesive layer 20, the bubbles 21 have a first bubble 21A arranged at a position away from the surface 11A of the base material 11 and a second bubble 21B in contact with the surface 11A of the base material 11. As described above, the pressure-sensitive adhesive layer 20 has not only the first bubbles 21A but also the second bubbles 21B that come into contact with the surface 11A of the base material 11, so that many of the pressure-sensitive adhesive layers 20 are in the vicinity of the outer surface 20A of the pressure-sensitive adhesive layer 20. The occupied volume of bubbles in the pressure-sensitive adhesive layer 20 can be increased without containing bubbles or increasing the bubble diameter more than necessary. Further, since it is not necessary to increase the diameter of the second bubble 21B or the like more than necessary, the bubble 21 is less likely to break. Therefore, the pressure-sensitive adhesive layer 20 having a sufficient thickness can be formed with a small amount of the pressure-sensitive adhesive while improving the adhesive performance. Further, even if the adhesive tape 10 is attached to the adherend for a long time, it is difficult to peel off.

As shown in FIG. 1, the second bubble 21B has a shape in the pressure-sensitive adhesive layer 20 that spreads in the plane direction rather than the thickness direction. Further, the second bubble 21B has a shape in which the side in contact with the surface 11A spreads in the plane direction and becomes smaller in the plane direction at a position away from the surface 11A, and is preferably hemispherical. The first bubble 21A has a shape in which the vicinity of the center in the thickness direction spreads in the plane direction and the end portion on the outer surface 20A or the surface 11A side becomes smaller in the plane direction, and is typically spherical or in the plane direction. It has a flat shape that extends along it. The first and second bubbles 21A and 21B are closed cells that do not communicate with other bubbles.

In the present embodiment, the second bubble 21B may be formed by volatilizing a liquid volatile component as described in detail in the production method described later. Further, the first bubble 21A is preferably a bubble derived from effervescent particles. As the effervescent particles, heat-expandable microcapsules are preferable as described later. The heat-expandable microcapsules are already expanded in the adhesive tape 10 and become hollow particles having bubbles inside the outer shell in the adhesive layer 20. That is, the first bubble 21A is preferably a bubble formed inside the hollow particle.

The average bubble diameter (D) of the bubbles 21 in the pressure-sensitive adhesive layer 20 is preferably 70 μm or less. When it is 70 μm or less, it is possible to prevent the bubbles from becoming too large and bursting. Therefore, it is possible to improve the adhesive performance of the pressure-sensitive adhesive layer 20 and prevent the adhesive strength after initial sticking from becoming too high or the adhesive performance from deteriorating after sticking. The average cell diameter (D) is more preferably 60 μm or less, further preferably 55 μm or less, and particularly preferably 50 μm or less.
The average bubble diameter (D) of the bubbles 21 is not particularly limited, but is preferably 10 μm or more, more preferably 20 μm or more, and more preferably 25 μm from the viewpoint of facilitating the formation of bubbles and the ease of reducing the amount of the adhesive due to the bubbles. The above is more preferable.
The average bubble diameter (D) of the bubbles 21 in the pressure-sensitive adhesive layer 20 means a value measured based on the method described in Examples described later.

Further, in the pressure-sensitive adhesive layer 20, the average cell diameter (D2) of the second bubble 21B is preferably larger than the average cell diameter (D1) of the first bubble 21A. According to such an embodiment, the diameter of the bubbles existing in the vicinity of the outer surface 20A of the pressure-sensitive adhesive layer 20 becomes small, so that the adhesive performance of the pressure-sensitive adhesive layer 20 can be easily improved.
The average bubble diameter (D2) of the specific second bubble 21B is preferably 20 to 100 μm, more preferably 30 to 80 μm, and even more preferably 35 to 60 μm.
Further, the average bubble diameter (D1) of the first bubble 21A is preferably smaller than the thickness of the pressure-sensitive adhesive layer 20. The specific average cell diameter (D1) is preferably 1 to 50 μm, more preferably 5 to 40 μm, and even more preferably 10 to 35 μm.
The average bubble diameter of each bubble can be measured by observing the pressure-sensitive adhesive layer 20 from the outer surface 20A side in a plan view.

The foaming ratio (E) of the pressure-sensitive adhesive layer 20 is preferably 1.7 times or more. When the foaming ratio (E) is 1.7 times or more, the thickness of the pressure-sensitive adhesive layer 20 can be sufficiently increased by the bubbles 21, and the amount of pressure-sensitive adhesive in the pressure-sensitive adhesive layer 20 can be reduced while maintaining the pressure-sensitive adhesive performance. Can be done. From such a viewpoint, the foaming ratio (E) of the pressure-sensitive adhesive layer 20 is more preferably 1.8 times or more, further preferably 1.9 times or more.
The foaming ratio (E) should be as high as possible from the viewpoint of reducing the amount of the adhesive, but from the viewpoint of adhesive performance, it is preferably 3.2 times or less, more preferably 3.0 times or less, and more preferably 2.8 times. The following is more preferable, 2.4 times or less is more preferable, and 2.0 times or less is particularly preferable.
The foaming ratio (E) is an index showing the amount of increase in the thickness of the pressure-sensitive adhesive layer 20 due to the bubbles 21. Specifically, the foaming ratio (E) is determined by the compression test shown in Examples described later to determine the amount of increase in the thickness of the pressure-sensitive adhesive layer 20 due to the bubbles 21, and the amount of non-foaming is determined based on the amount of increase in the thickness. The thickness of the pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer after foaming can be obtained and calculated from the thickness of the pressure-sensitive adhesive layer after foaming / the thickness of the non-foamed pressure-sensitive adhesive layer.

The foaming ratio (E1) of the pressure-sensitive adhesive layer 20 due to the second bubbles 21B is preferably 1.1 to 1.9 times, more preferably 1.3 to 1.8 times. The foaming ratio by the second bubble 21B is the foaming ratio when it is assumed that the first bubble 21A does not exist, and can be measured by, for example, the method described in Examples described later.
Further, in the pressure-sensitive adhesive layer 20, the increase in foaming ratio (E2) due to the first bubble 21A is preferably 0.05 to 1.5 times, more preferably 0.1 to 1.3 times.
The increase in foaming ratio (E2) can be calculated by subtracting the foaming ratio (E1) due to the second bubble 21B from the foaming ratio (E) of the entire pressure-sensitive adhesive layer 20.

The thickness of the pressure-sensitive adhesive layer 20 is not particularly limited, but is preferably 10 μm or more, more preferably 15 μm or more, and more preferably 20 μm or more, from the viewpoint of ensuring adhesive performance while appropriately forming bubbles 21 inside the pressure-sensitive adhesive layer 20. Is even more preferable. The thickness of the pressure-sensitive adhesive layer 20 is preferably 150 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less. By setting these upper limit values or less, the amount of adhesive can be reduced. In addition, the effect of providing the second bubble 21B in contact with the surface 11A of the base material 11 can be easily exerted.

The ball tack value measured with respect to the outer surface 20A of the adhesive tape 10 stored in a constant temperature bath adjusted to 40 ° C. for 4 weeks is preferably 5 to 14. When the ball tack value is within the above range, the adhesive layer 20 has excellent long-term stability of stickability, and can be suitably used for an adhesive tape for packaging or the like. From these viewpoints, the ball tack value of the pressure-sensitive adhesive layer 20 in the pressure-sensitive adhesive tape 20 stored in a constant temperature bath adjusted to 40 ° C. for 4 weeks is more preferably 6 to 12. The ball tack value can be measured in accordance with JISZ 0237: 2009.

Examples of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 20 include an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a polyvinyl ether-based pressure-sensitive adhesive, and a silicone-based pressure-sensitive adhesive. These pressure-sensitive adhesives contain a resin component that is a main component of a pressure-sensitive adhesive such as an acrylic resin, a rubber component, a urethane resin, a polyvinyl ether, and a silicone resin, and the main agent is further mixed with an additive or the like as appropriate. ..

(Effervescent particles)
As described above, the pressure-sensitive adhesive layer 20 has bubbles derived from effervescent particles. Therefore, the pressure-sensitive adhesive layer 20 can be formed by heating and foaming the pressure-sensitive adhesive composition containing the effervescent particles in addition to the above-mentioned main agent, as will be described later. The effervescent particles are those that foam when heated, and may be a pyrolytic foaming agent or the like, but thermally expandable microcapsules are preferable. When heated, the heat-expandable microcapsules become hollow particles having bubbles inside the outer shell. When the heat-expandable microcapsules are used in the present embodiment, the gas generated from the effervescent particles is prevented from escaping to the outside of the pressure-sensitive adhesive layer 20, and appropriate amounts of the first and second bubbles 21A and 21B are adhered. It becomes easy to coexist in the agent layer 20, and it becomes easy to improve the foaming ratio.

Thermally expandable microcapsules contain volatile substances such as low boiling point solvents inside the outer shell resin, and the outer shell resin softens due to heating, and the contained volatile substances volatilize or expand. The pressure causes the outer shell to expand and the particle size to increase.
The outer shell of the heat-expandable microcapsules is preferably formed of a thermoplastic resin. Thermoplastic resins are made from vinyl polymers such as ethylene, styrene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, butadiene, and chloroprene, copolymers thereof, polyamides such as nylon 6, nylon 66, and polyesters such as polyethylene terephthalate. One or more selected types can be used. Among these, a copolymer of acrylonitrile is preferable because the contained volatile substances are difficult to permeate.

Volatile substances contained inside the heat-expandable microcapsules include hydrocarbons having 3 to 7 carbon atoms such as propane, propylene, butene, normal butane, isobutane, isopentane, neopentane, normal pentane, hexane, and heptane, and petroleum. One or 2 selected from methane halides such as ether, methyl chloride and methylene chloride _{, chlorofluorocarbons such as CCl 3} F and CCl ₂ F ₂ , tetraalkylsilanes such as tetramethylsilane and trimethylethylsilane, and the like. Low boiling point liquids above the seed are used. Among these, it is preferable to use a hydrocarbon having 3 to 7 carbon atoms.

The heat-expandable microcapsules are not particularly limited, but for example, those having an average particle size of 1 to 40 μm and an expansion start temperature (also referred to as “foaming start temperature”) of about 95 to 150 ° C. may be used. The average particle size may be obtained by averaging 10 points by randomly selecting particles with an optical microscope or the like. The expansion start temperature is the temperature at which the thermally expandable microcapsules start to expand, and can be measured by a thermomechanical analyzer (TMA) or the like.

Examples of commercially available heat-expandable microcapsules include "EXPANCEL" manufactured by AkzoNobel, "Advancel" manufactured by Sekisui Chemical Co., Ltd., "Matsumoto Microsphere" manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd., and "Micro" manufactured by Kureha Corporation. "Sfair" and the like.

Further, the thermally decomposable foaming agent used as the foamable particles may be either an organic foaming agent or an inorganic foaming agent. Examples of the organic foaming agent include azodicarboxylic amides, azodicarboxylic acid metal salts (such as barium azodicarboxylic acid), azo compounds such as azobisisobutyronitrile, and nitroso compounds such as N, N'-dinitrosopentamethylenetetramine. Examples thereof include hydrazine derivatives such as hydrazodicarboxylic amide, 4,4'-oxybis (benzenesulfonyl hydrazide) and toluenesulfonylhydrazide, and semicarbazide compounds such as toluenesulfonyl semicarbazide.
Examples of the inorganic foaming agent include ammonium carbonate, sodium carbonate, ammonium hydrogencarbonate, sodium hydrogencarbonate, ammonium nitrite, sodium borohydride, monosoda anhydrous citrate and the like.

(Rubber adhesive)
Among the above, it is preferable to use a rubber-based pressure-sensitive adhesive as the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 20. By using the rubber-based pressure-sensitive adhesive, the pressure-sensitive adhesive layer 20 is imparted with a certain degree of hardness or more, and it becomes easy to maintain a constant shape even if many bubbles are formed inside. Therefore, the pressure-sensitive adhesive layer 20 can easily maintain the pressure-sensitive adhesive performance even if the foaming ratio is increased. The rubber-based pressure-sensitive adhesive uses a rubber component as a main component as described above, and the rubber components include natural rubber, ethylene / propylene rubber (EPDM), chloroprene rubber (CR), isoprene rubber, and butyl rubber (IIR). ), butadiene rubber (BR), chlorosulfonated polyethylene and the like. Of these, natural rubber is preferred. Further, the rubber component may be a thermoplastic elastomer.

As the rubber component, a thermoplastic elastomer is preferable, and a styrene-based thermoplastic elastomer is particularly preferable. By using the thermoplastic elastomer, the pressure-sensitive adhesive can be used as a hot-melt pressure-sensitive adhesive, and it becomes easy to appropriately form fine bubbles as described later.
As the styrene-based thermoplastic elastomer, block copolymers of styrene and isoprene are preferably used, specifically, styrene-isoprene-styrene block copolymer (SIS) and styrene-isoprene block copolymer (SI). Etc., and SIS is more preferable.

The rubber-based pressure-sensitive adhesive preferably contains a tack-imparting agent in addition to the above-mentioned rubber component. The adhesiveness-imparting agent imparts adhesiveness to the rubber-based pressure-sensitive adhesive to improve the adhesive performance of the pressure-sensitive adhesive layer 20. Examples of the tackifier include rosin-based resin, terpene-based resin, kumaron-inden resin, petroleum-based resin, and terpene-phenol resin, and among these, petroleum-based resin is preferable. The content of the tackifier in the pressure-sensitive adhesive is, for example, 20 to 200 parts by mass, preferably 50 to 150 parts by mass with respect to 100 parts by mass of the rubber component.

The rubber-based pressure-sensitive adhesive may contain a softening agent in addition to the above-mentioned tackifier. When the rubber-based pressure-sensitive adhesive contains a softening agent, the pressure-sensitive adhesive is softened, and it becomes easy to improve the coatability and adhesive performance. Examples of the softening agent include mineral oils such as paraffin oil and naphthenic oil (also called process oils), liquid polybutene, liquid lanolin, liquid polyisoprene, and liquid polyacrylate. The content of the softening agent in the pressure-sensitive adhesive is, for example, 5 to 80 parts by mass, preferably 10 to 50 parts by mass with respect to 100 parts by mass of the rubber component.

In addition to the above, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 20 is appropriately blended with known additives used for pressure-sensitive adhesives such as fillers, antioxidants, antioxidants, ultraviolet rays, and pigments. May be good.

[Base material]
The base material 11 used for the adhesive tape may be a paper base material, a cloth base material, a resin film, or a multilayer base material in which two or more of these are combined. For example, a multilayer base material in which a resin layer is provided on at least one surface of a paper base material or a cloth base material may be used.
Examples of the paper base material include kraft paper, glassine paper, and woodfree paper. Examples of the cloth base material include woven fabrics, knitted fabrics, and non-woven fabrics made of thermoplastic resins such as polyester resins, polyamide resins, and polyolefin resins, and natural fibers such as cotton threads and hemp threads. Examples of the resin film include polyester film, polyolefin film, polystyrene film, acrylic resin film, polyphenylene sulfide film, EVA film and the like. Similarly, examples of the resin layer used for the multilayer base material include a polyester resin layer, a polyolefin resin layer, a polystyrene resin layer, an acrylic resin layer, a polyphenylene sulfide resin layer, and an EVA resin layer.

Among these, as shown in FIG. 2, the base material 11 is preferably a multilayer base material including the paper base material 12 and the resin layer 13 provided on one surface of the paper base material 12. In this case, the surface of the paper base material 12 opposite to the surface on which the resin layer 13 is provided (the other surface) constitutes the surface 11A of the base material 11, and the pressure-sensitive adhesive layer 20 is provided on the other surface. It would be nice to be done.
As shown in FIG. 2, by using the paper base material 12, the liquid volatile component described later is easily impregnated into the base material 11, and by providing the resin layer 13, the impregnated liquid volatile component is used as a base. It becomes difficult to volatilize from the back surface 11B of the material 11. Therefore, it becomes easy to efficiently form the second bubble 21B in the pressure-sensitive adhesive layer 20.

The paper base material 12 is preferably kraft paper, and the resin layer 13 is preferably a polyolefin resin layer. When kraft paper is used as the paper base material 12, it becomes easier to impregnate the liquid volatile component more into the base material 11, and it becomes easier to form the second bubble 21B uniformly in a sufficient amount. Further, when kraft paper is used, the adhesive tape 10 becomes a kraft tape, which is suitable as an adhesive tape for packaging or the like.
As the polyolefin resin used for the polyolefin resin layer, a polyethylene-based resin and a polypropylene-based resin are preferable, but a polyethylene-based resin is more preferable. That is, the resin layer 13 is preferably a polyethylene-based resin layer. By using the polyethylene-based resin, the heat resistance and the adhesiveness to the paper base material such as kraft paper are likely to be improved, and further, the volatilization of the liquid volatile component from the back surface 11B is easily prevented.

The thickness of the base material 11 is not particularly limited, but is, for example, 10 to 1000 μm. Further, when the base material 11 is a multilayer base material including the paper base material 12 and the resin layer 13 as described above, the paper base material 12 preferably ^{has a basis weight of 10 to 150 g / m 2.} More preferably, it is ~ 100 g / m ^2. When the basis weight is within the above range, the base material 11 can be easily impregnated with the liquid volatile component without increasing the thickness of the base material 11 more than necessary. The thickness of the resin layer 13 is preferably, for example, 5 to 100 μm, more preferably 10 to 50 μm.

(Release agent layer)
As shown in FIGS. 1 and 2, the adhesive tape 10 is preferably provided with the release agent layer 30 on the surface (back surface 11B) opposite to the surface of the base material 11 on which the adhesive layer 20 is provided. By providing the release agent layer 30, when the adhesive tape 10 is wound into a roll to form a wound body, the adhesive layer 20 comes into contact with the release agent layer 30. Therefore, the adhesive tape 10 can be easily unwound from the winding body.
The release agent layer 30 may be formed from a known release agent such as a silicone-based release agent or a long-chain alkyl-based release agent. The thickness of the release agent layer 30 is not particularly limited, but may be adjusted so that the amount of adhesion thereof is, for example, 0.1 to 10 g / m ² , preferably about 0.3 to 5 g / m ^2.

As described above, the adhesive tape 10 may be wound in a roll shape to form a wound body. The adhesive tape 10 may be wound around the core in a roll shape, for example. In the case of forming a wound body, the adhesive layer 20 may be wound on the inside and the release agent layer 30 may be on the outside, whereby the outermost peripheral surface of the wound body may be formed on the release agent layer 30. can. Further, the adhesive tape 10 is suitable as an adhesive tape for packaging by forming a wound body.
Of course, the adhesive tape 10 does not have to be a wound body, and may be left in the form of a sheet. In such a case, a release sheet or the like for protecting the pressure-sensitive adhesive layer 20 may be attached to the surface of the pressure-sensitive adhesive layer 20, and the release agent layer 30 may be omitted as appropriate.

[Manufacturing method of adhesive tape]
The method for producing an adhesive tape according to the embodiment of the present invention is compared with the step of laminating the pressure-sensitive adhesive composition containing foamable particles on the surface of the base material and the temperature of the surface of the obtained laminate on the base material side. The step includes heating the laminate so that the temperature of the surface of the laminate on the pressure-sensitive adhesive composition side becomes low, and at least foaming the foamable particles on the substrate side of the pressure-sensitive adhesive composition. This makes it easy to manufacture an adhesive tape having a surface roughness (Rz) of 40 μm or less on the outer surface of the adhesive layer. As a result, it becomes easy to manufacture an adhesive tape that has good stickability to the adherend and is hard to peel off even if it is stuck to the adherend for a long time. For example, in the above step of heating the laminate, the foamable particles on the base material side of the pressure-sensitive adhesive composition are foamed, and the foamable particles near the surface on the side opposite to the base material side of the pressure-sensitive adhesive composition are foamed. You may not let it.

The method for producing an adhesive tape according to the embodiment of the present invention includes, for example, the following steps 1 to 3.
Step 1: A step of coating or impregnating the surface of the base material with a liquid volatile component Step 2: A step of laminating an adhesive composition containing foamable particles on the surface of the base material Step 3: Lamination obtained in Step 2. A step of forming bubbles inside the pressure-sensitive adhesive layer composed of the pressure-sensitive adhesive composition by heating the body.

Hereinafter, each step will be described in detail.
(Step 1)
The base material used in this production method is as described above, but when the release agent layer 30 is provided on the pressure-sensitive adhesive tape 10, the surface (surface 11A) on which the pressure-sensitive adhesive layer 20 of the base material 11 is provided. It is preferable to form the release agent layer 30 on the surface (back surface 11B) opposite to the above. The release agent layer may be formed, for example, by applying a release agent diluted with a solvent or the like to the base material, and heating and drying as necessary.

The liquid volatile component used in step 1 is a liquid at normal temperature (23 ° C.) and normal pressure (1 atm), and a component that volatilizes by heating is used. Examples of the liquid volatile component include alcohols such as water, ethanol, methanol, isopropanol and n-propanol, and organic solvents such as toluene, ethyl acetate and methyl ethyl ketone. Of these, water is preferably used because it is excellent in safety and does not volatilize rapidly. These liquid volatile components may be used alone or in combination of two or more.

The method of coating or impregnating the liquid volatile component is not particularly limited, and examples thereof include a transfer coating method using a gravure roll or the like, a spray coating method using a spray coating machine or the like, and the like.
In this production method, the amount of the liquid volatile component adhered to the substrate is preferably 1 to ^{20 g / m 2.} By setting the adhering amount of the liquid volatile component to the above lower limit value or more, a sufficient amount of the second bubble 21B can be formed in the pressure-sensitive adhesive layer 20. Further, by setting the value to the upper limit or less, it is possible to prevent the bubble diameter of the second bubble 21B from becoming too large and causing bubbles to break, and it becomes easy to improve the adhesive performance. From these viewpoints, the adhesion amount of the liquid volatile component to the substrate is more preferably 1.5~15g / ^{m 2,} more preferably 2 to 10 g / ^{m 2.}

(Step 2)
The step 2 is a step of laminating the pressure-sensitive adhesive composition containing the foamable particles on the surface of the base material coated or impregnated with the liquid volatile component in the step 1.
Here, the pressure-sensitive adhesive composition contains effervescent particles in addition to the main agent (resin component) constituting the pressure-sensitive adhesive, a pressure-sensitive adhesive, a softening agent, and other additives to be blended as needed. The effervescent particles are as described above, and thermally expandable microcapsules are preferably used.
The blending amount of the effervescent particles in the pressure-sensitive adhesive composition is preferably 0.05 parts by mass or more, more preferably 0.15 parts by mass or more, and more preferably 0.3 parts by mass or more with respect to 100 parts by mass of the pressure-sensitive adhesive composition. More preferred. By setting the blending amount of the effervescent particles to these lower limit values or more, an appropriate amount of the first bubble 21A can be formed in the pressure-sensitive adhesive layer 20. The blending amount of the effervescent particles is preferably 1.5 parts by mass or less, more preferably 1.0 part by mass or less, and further preferably 0.5 parts by mass or less. By setting the blending amount of the effervescent particles to these upper limit values or less, the amount of air bubbles near the outer surface 20A of the pressure-sensitive adhesive layer 20 is suppressed, and the adhesive performance is prevented from being deteriorated by the air bubbles 21.

The pressure-sensitive adhesive composition may be a solvent-diluted type diluted with a solvent, or may be a hot-melt type without being diluted with a solvent, but a hot-melt type is preferable. By adopting the hot melt type, the pressure-sensitive adhesive composition can be easily softened by heat without hindering the gasification of liquid volatile components, and the bubbles easily solidified by cooling can be retained in a finely dispersed state. ..

The method for preparing the pressure-sensitive adhesive composition is not particularly limited, and for example, the components constituting the pressure-sensitive adhesive composition may be mixed in a stirrer or the like. Further, in the case of the hot melt type, it is preferable to heat and mix the resin component as the main agent at a temperature higher than the melting temperature. Further, in order to prevent the effervescent particles from expanding due to heating, mixing may be performed under appropriate pressure.
The method of laminating the pressure-sensitive adhesive composition is not particularly limited, and examples thereof include a method of directly coating the pressure-sensitive adhesive composition on a base material using a roll coater, a die coater, a hot melt coater, or the like.

(Step 3)
Step 3 is a step of forming bubbles 21 inside the pressure-sensitive adhesive layer 20 composed of the pressure-sensitive adhesive composition by heating the laminate obtained in step 2. Specifically, in step 3, the laminate is heated so that the temperature of the surface of the obtained laminate on the substrate side is lower than the temperature of the surface of the laminate on the pressure-sensitive adhesive composition side. Then, the foamable particles on the base material side of the pressure-sensitive adhesive composition are foamed, and the foamable particles near the surface on the side opposite to the base material side of the pressure-sensitive adhesive composition are not foamed. For example, when a hot air furnace is used as the foaming furnace, the temperature of the hot air blown to the base material side of the laminated body is higher than the temperature of the hot air blown to the adhesive composition side of the laminated body to make the laminated body as described above. Can be heated. As a result, the effervescent particles in the pressure-sensitive adhesive composition start foaming from the substrate side. Then, before the effervescent particles near the surface of the pressure-sensitive adhesive composition on the side opposite to the base material side start foaming, the laminate is discharged from the foaming furnace to bring the pressure-sensitive adhesive composition to the base material side. It is possible to foam certain foamable particles so that the foamable particles near the surface of the pressure-sensitive adhesive composition on the side opposite to the base material side are not foamed. Further, using a batch furnace, the laminate is heated so that the temperature of the surface of the laminate on the pressure-sensitive adhesive composition side is lower than the temperature of the surface of the laminate on the substrate side, and the base of the pressure-sensitive adhesive composition is heated. The laminate may be removed from the batch furnace before the foamable particles near the surface on the side opposite to the material side begin to foam.

Further, in step 3, the liquid volatile component coated or impregnated in the base material is volatilized to form a second bubble 21B at a position in contact with the surface 11A of the base material 11. Further, as described above, by foaming the effervescent particles contained in the pressure-sensitive adhesive composition, the first bubbles 21A derived from the effervescent particles are formed at a position away from the surface 11A of the base material 11. At the same time, the non-foaming pressure-sensitive adhesive layer 22 is formed on the side opposite to the base material side of the pressure-sensitive adhesive layer 20.

The heating temperature on the substrate side of the laminate in step 3 may be a temperature equal to or higher than the boiling point of the liquid volatile component and equal to or higher than the foaming start temperature of the foamable particles. The specific heating temperature is preferably 110 ° C. to 170 ° C., more preferably 130 to 165 ° C. On the other hand, the heating temperature on the pressure-sensitive adhesive composition side of the laminate in step 3 is preferably 20 ° C. or higher, more preferably 25 ° C. or higher, still more preferably 30 ° C. or higher, as compared with the heating temperature on the substrate side of the laminate. The temperature may be low. The specific heating temperature is preferably 85 to 145 ° C, more preferably 105 to 140 ° C.
Further, the heating time at the above heating temperature is equal to or longer than the time during which the liquid volatile components are volatilized and the foamable particles on the substrate side of the pressure-sensitive adhesive composition are foamed, and the heating time is equal to or longer than the time required for the base material side of the pressure-sensitive adhesive composition. It is not limited as long as it is less than or equal to the time during which the effervescent particles near the surface on the opposite side do not foam, but it is preferably 1 to 20 seconds, more preferably 2 to 10 seconds, and further preferably 3 to 5 seconds.
The heating method is not particularly limited, and examples thereof include hot air, infrared rays, and microwaves. For example, the laminate may be passed through a heating furnace whose inside is heated to a predetermined temperature. The method for transporting the heating furnace is not particularly limited, and examples thereof include a roll support type, an air floating type, a belt transport type, and a hanging dryer type.

As described above, the adhesive tape of the present invention has been described in detail with reference to the embodiments, but the adhesive tape is not limited to the above-described configuration as long as the effects of the present invention are exhibited. For example, the first bubble 21A may be formed by a particle other than the foamable particles, or the second bubble 21B may be formed by a component other than the liquid volatile component. Furthermore, the first and second bubbles do not have to be closed cells. Further, the release agent layer may be omitted as appropriate, or another layer may be provided on the back surface 11B of the base material 11 instead of the release agent layer. Further, another layer may be appropriately provided between the release agent layer and the back surface 11B of the base material 11.

The adhesive tape of the embodiment of the present invention may be modified as follows.
The pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape according to the embodiment of the present invention may not contain both the first bubble and the second bubble, or may contain one of the first bubble and the second bubble. For example, as in the adhesive tape shown in FIG. 3, the pressure-sensitive adhesive layer 20 contains the first air bubbles 21A separated from the surface 11A of the base material 11, and the pressure-sensitive adhesive layer 20 does not contain the second air bubbles in contact with the surface 11A of the substrate 11. May be good.

The pressure-sensitive adhesive layer 20 is formed by forming the non-foaming pressure-sensitive adhesive layer 22 containing no air bubbles inside on the foamed pressure-sensitive adhesive layer 23 containing air bubbles as in the pressure-sensitive adhesive tape 10 shown in FIG. You may try to do it. Also in this case, since the non-foaming pressure-sensitive adhesive layer 22 existing near the outer surface of the pressure-sensitive adhesive layer 20 does not have bubbles that cause the outer surface 20A of the pressure-sensitive adhesive layer 20 to form a convex portion, the pressure-sensitive adhesive layer The surface roughness (Rz) of the outer surface 20A of 20 can be easily reduced to 40 μm or less. For example, a pressure-sensitive adhesive composition containing effervescent particles is applied onto a substrate, and then a pressure-sensitive adhesive composition containing no effervescent particles is applied onto a layer of the pressure-sensitive adhesive composition containing effervescent particles. Then, the obtained laminate may be foamed. Further, the pressure-sensitive adhesive composition containing the effervescent particles is applied onto the base material, the obtained laminate is foamed, and then the pressure-sensitive adhesive composition containing no effervescent particles is further applied onto the laminate. It may be applied.

If the surface roughness (Rz) of the outer surface 20A of the pressure-sensitive adhesive layer 20 can be 40 μm or less, the pressure-sensitive adhesive layer 20 may not include a non-foaming pressure-sensitive adhesive layer containing no bubbles inside. For example, as in the adhesive tape 10 shown in FIG. 5, by reducing the bubble diameter of the first bubbles 21A existing in the vicinity of the outer surface of the adhesive layer 20, the first cells are located in the vicinity of the outer surface of the adhesive layer 20. Even if the bubbles 21A are present, the surface roughness (Rz) of the outer surface 20A of the first air pressure-sensitive adhesive layer 20 can be reduced to 40 μm or less. The bubble diameter of the first bubble 21A existing in the vicinity of the outer surface of the pressure-sensitive adhesive layer 20 is, for example, 40 μm or less, preferably 30 μm or less, more preferably 25 μm or less, still more preferably 20 μm or less.

Further, the method for producing the adhesive tape according to the embodiment of the present invention may be modified as follows.
In the step of heating the laminate of the method for producing an adhesive tape in the embodiment of the present invention, the foamable particles on the base material side of the pressure-sensitive adhesive composition are foamed, and the side opposite to the base material side of the pressure-sensitive adhesive composition is foamed. The effervescent particles near the surface were not foamed. However, if the bubble diameter is reduced in the step of heating the laminate (for example, 40 μm or less, preferably 30 μm or less, more preferably 25 μm or less, still more preferably 20 μm or less), the substrate side of the pressure-sensitive adhesive composition Foamable particles near the surface on the opposite side may be foamed. Also in this case, it becomes easy to manufacture an adhesive tape having a surface roughness (Rz) of 40 μm or less on the outer surface of the adhesive layer. As a result, it becomes easy to manufacture an adhesive tape having excellent long-term stability of adhesive performance even if it has air bubbles.

Examples of the present invention will be described below. However, the present invention is not limited to the following examples.

The measurement method and evaluation method are as follows.
<Average cell diameter (D)>
With respect to the obtained adhesive tape, a region of 1 mm × 1 mm from the outer surface side of the adhesive layer was observed with an optical microscope (“VHX-6000” manufactured by KEYENCE CORPORATION) at a magnification of 200 times, and the bubble diameter of all bubbles in the region was observed. Was measured, and the average value was taken as the average cell diameter (D). Further, the average bubble diameters (D1) and (D2) of the first and second bubbles were measured by the same method.

<Effervescence magnification (E)>
The adhesive tape was wound around a tubular core (outer diameter of 80 mm) by 50 m to form a wound body. As shown in FIG. 6, a columnar fixing portion 51 is passed through the inside of the winding core of the obtained winding body 50, and the movable portion 52 is pressed against the outer peripheral surface of the winding body 50 to reduce the diameter of the movable portion 52. Pressing inward in the direction, the winding body 50 was compressed along the radial direction. Tencilon "RTC-1310A" (manufactured by ORIENTEC) was used for compression of the winding body 50.
In the graph (movement distance (x-axis) vs. weight (y-axis)) when the winding body 50 is compressed, the tangent line of the portion where the slope of the tangent line is constant is extended, and the value of x at the intersection with the x-axis is extended. Was calculated as the thickness (A) of the wound body containing bubbles. After that, the same operation is performed with the tape sample without bubbles, the thickness (B) of the wound body containing no bubbles is measured from the calculated intersection, and the thickness (B) is subtracted from the thickness (A). , The thickness increased by the air bubbles contained in the wound body was calculated, and the thickness was divided by the number of laminated tapes to obtain the increase in the thickness due to the air bubbles contained in one tape. For the foaming ratio, the thickness of the pressure-sensitive adhesive layer of the tape sample without bubbles is defined as the thickness of the unfoamed pressure-sensitive adhesive layer, and the value obtained by adding the increase in thickness to the thickness of the non-foamed pressure-sensitive adhesive layer is the value after foaming. As the thickness of the pressure-sensitive adhesive layer, the foaming ratio (E) was calculated from the thickness of the pressure-sensitive adhesive layer after foaming / the thickness of the non-foamed pressure-sensitive adhesive layer.
The tape sample without bubbles is the same as in each Example and Comparative Example except that the base material is not coated or impregnated with a liquid volatile component and foamable particles are not blended in the pressure-sensitive adhesive composition. It is a sample obtained when an adhesive tape is prepared by the method.

<Expansion ratio due to the second bubble (E1), increase in expansion ratio due to the first bubble (E2)>
Adhesive tapes were prepared in the same manner as in each Example and Comparative Example except that the pressure-sensitive adhesive composition did not contain foamable particles, and the obtained sample was used as a tape sample without foamable particles. The foaming ratio of the tape sample without foamable particles was measured in the same manner as described above, and the foaming ratio was defined as the foaming ratio (E1) by the second bubble. Further, the increase in the foaming ratio (E2) due to the first bubble was calculated by subtracting the foaming ratio (E1) due to the second bubble from the foaming ratio (E) calculated above.

<Surface roughness (Rz)>
In the roughness curve measured according to JIS B 0601, the average of the mountain heights from the highest peak in the vertical direction to the fifth in the height order from the average line, and 5 in the order of depth from the deepest valley bottom. It was calculated from the sum with the average of the valley depths up to the third depth.

<Long-term stability of ball tack>
The prepared adhesive tape was stored in a constant temperature bath adjusted to 40 ° C. for 4 weeks. Then, for the adhesive tape after storage for 4 weeks, the ball tack value of the adhesive layer was measured at an inclination angle of 30 ° in accordance with JISZ 0237: 2009. The measured ball tack value was evaluated according to the following evaluation criteria.
A: The ball tack value was 6 or more and 12 or less, and the long-term stability of stickability was excellent.
B: The ball tack value was smaller than 6 and larger than 12, but it was 5 or more and 14 or less, and the long-term stability of stickability was good.
C: The ball tack value was less than 5 or larger than 14, and the adhesive strength was insufficient, or the adhesive strength was too large and the reworkability was insufficient, and the long-term stability of the stickability was insufficient.

<Long-term stability of packing performance>
The prepared adhesive tape was stored in a constant temperature bath adjusted to 40 ° C. for 4 weeks. A commercially available cardboard box having dimensions of 400 mm × 320 mm × 300 mm and having a flap abutting portion length of 400 mm was prepared. An adhesive tape having a width of 50 mm stored for 4 weeks was attached to the flap abutting portion at 25 ° C. by I-sticking to the cardboard box, and pressure-bonded at 32 g / 50 mm. Then, the peeling rate after being left at an atmospheric temperature of 25 ° C. and a humidity of 50% RH for 1 hour was measured and evaluated according to the following evaluation criteria. The peeling rate is the area ratio of the peeled portion to the adhesive tape used.
AA: The peeling rate was 25% or less, and excellent adhesive performance could be maintained for a long period of time.
A: The peeling rate was larger than 25% and 40% or less, and a constant adhesive performance could be maintained for a long period of time.
B: The peeling rate was more than 40% and 50% or less, and the adhesive performance that could be practically used for a long period of time could be maintained.
C: The peeling rate was larger than 50%, and the adhesive performance could not be maintained for a long period of time.

[Example 1]
Polyethylene (PE) is extruded and laminated to a thickness of 20 μm on one side of a paper base material made of ^{unbleached kraft paper with a basis weight of 73 g / m 2} that has been subjected to curl pack processing and wet strength processing. A polyethylene-based resin layer was formed on one surface to obtain a base material composed of a paper base material and a resin layer. A silicone-based mold release agent is applied onto the polyethylene-based resin layer of the obtained base material so that the amount of adhesion after drying is 1 g / m ^2, and dried to form a mold release agent layer on the back surface of the base material. Formed.
Next, water was spray-coated on the surface of the base material as a liquid volatile component so that the amount of adhesion was 9 g / m ^2, and then the composition shown in Table 1 was applied onto the surface at 150 ° C. and 1.0 MPa. The hot melt type pressure-sensitive adhesive composition obtained by stirring was applied at 150 ° C. so that the coating width was 300 mm and the coating amount was 30 g / m ^{2, to obtain a laminate.} The obtained laminate was passed through a foaming furnace and heated to obtain an adhesive tape of Example 1 by steam foaming and particle foaming. In the foaming furnace, the heating temperature on the substrate side of the laminate was 160 ° C., and the heating temperature on the hot melt type pressure-sensitive adhesive composition side was 135 ° C. The heating time was 4 seconds.
In the adhesive tape, the average bubble diameter of the bubbles (first bubble) obtained by particle foaming was 26 μm, and the average bubble diameter of the bubbles (second bubble) obtained by steam foaming was 50 μm.

[Examples 2 and 3 and Comparative Examples 1 to 3]
The blending amount of the effervescent particles in the pressure-sensitive adhesive composition, the coating temperature of the pressure-sensitive adhesive composition, and the heating conditions of the laminate were changed as shown in Table 2, and in Example 2, Sekisui was used as the effervescent particles. The same procedure as in Example 1 was carried out except that "Advancel EM304: particle size before foaming 24 μm" manufactured by Kagaku Kogyo Co., Ltd. was used.

By comparing the evaluation results of Examples 1 to 3 and Comparative Examples 1 to 3, the surface roughness (Rz) of the outer surface of the adhesive layer of the adhesive tape is set to 40 μm or less, so that the adhesive performance of the adhesive tape is improved. It was found that long-term stability was improved. In Comparative Example 1, since the heating temperature on the base material side of the laminated body was too high, the bubble diameter of the bubbles near the outer surface of the pressure-sensitive adhesive layer became large, and the surface roughness of the outer surface of the pressure-sensitive adhesive layer of the adhesive tape became large. It is considered that the (Rz) became larger than 40 μm. Further, in Comparative Example 2, since the amount of the foamable particles was large, the number of bubbles in the pressure-sensitive adhesive layer increased, and the bubbles having a large bubble diameter overflowed and moved to the vicinity of the outer surface of the pressure-sensitive adhesive layer. It is considered that the surface roughness (Rz) of the outer surface of the pressure-sensitive adhesive layer became larger than 40 μm.

10 Adhesive tape 11 Base material 12 Paper base material 13 Resin layer 20 Adhesive layer 21 Bubbles 21A First bubble 21B Second bubble 30 Release agent layer

Claims (11)

A base material and an adhesive layer provided on the surface of the base material and containing air bubbles inside are provided.
An adhesive tape having a surface roughness (Rz) of 40 μm or less on the outer surface of the pressure-sensitive adhesive layer. The first aspect of the present invention includes a foamed pressure-sensitive adhesive layer containing air bubbles inside, and a non-foamed pressure-sensitive adhesive layer containing no air bubbles inside on the opposite side of the foamed pressure-sensitive adhesive layer to the base material side. The described adhesive tape. The adhesive tape according to claim 1 or 2, wherein the bubbles include a first bubble that is arranged at a position away from the surface of the base material. The adhesive tape according to claim 3, wherein the first bubble is a bubble derived from foamable particles. The adhesive tape according to claim 3, wherein the first bubble is a bubble formed inside the hollow particle. The adhesive tape according to any one of claims 3 to 5, wherein the bubbles further include a second bubble that comes into contact with the surface of the base material. The adhesive tape according to any one of claims 1 to 6, wherein the foaming ratio of the pressure-sensitive adhesive layer measured by a compression test is 1.7 times or more. The adhesive tape according to any one of claims 1 to 7, wherein the average bubble diameter of the bubbles contained in the pressure-sensitive adhesive layer is 70 μm or less. Claims 1 to 8 wherein the base material includes a paper base material and a resin layer provided on one surface of the paper base material, and the pressure-sensitive adhesive layer is provided on the other surface of the paper base material. The adhesive tape according to any one of the above. The adhesive tape according to claim 9, wherein the paper base material is kraft paper and the resin layer is a polyethylene-based resin layer. The step of laminating the pressure-sensitive adhesive composition containing the foamable particles on the surface of the base material, and the temperature of the surface of the laminated body on the base material side as compared with the temperature of the surface of the laminated body on the side of the pressure-sensitive adhesive composition. A method for producing an adhesive tape, which comprises a step of heating the laminate so that the temperature becomes low and at least foaming the foamable particles on the substrate side of the pressure-sensitive adhesive composition.

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