JP7818956B2 - adhesive tape - Google Patents

Description

The present invention relates to an adhesive tape.

Generally, adhesives (also known as pressure-sensitive adhesives; the same applies hereinafter) are in a soft solid (viscoelastic) state at temperatures near room temperature, and have the property of easily adhering to an adherend when pressure is applied. Taking advantage of these properties, adhesives are widely used in a variety of fields for purposes such as joining, fixing, surface protection, masking, and marking, typically in the form of adhesive tape having an adhesive layer on a substrate. Marking adhesive tapes are generally used, for example, as line tape to mark divisions, markers, and information on the floors of factories, gymnasiums, etc., or as tape to create tiger patterns (yellow and black stripes) to draw attention at construction sites, etc. Patent Document 1 is an example of a technical document related to marking adhesive tapes.

Japanese Patent Application Laid-Open No. 2001-279202

However, conventional marking adhesive tapes are prone to peeling or damage (tears, chips, etc.) when applied to rough surfaces and subjected to frequent strong stresses from the backside of the tape (specifically, when applied to outdoor paved surfaces and frequently driven over by vehicles, a harsh usage pattern). If the period during which the above-mentioned adhesive tape can properly perform its functions (usage life) could be improved, it would be beneficial from the perspective of maintaining a good appearance for a longer period of time and reducing the frequency of replacement with new adhesive tape, thereby reducing workload and saving resources.

The present invention therefore aims to provide an adhesive tape that exhibits an improved service life even when applied to a rough surface and subjected to frequent strong stresses.

The pressure-sensitive adhesive tape provided by this specification includes a substrate having a first side and a second side, and a pressure-sensitive adhesive layer disposed on the first side of the substrate. The substrate includes at least a layer A composed of a resin composition (a) and constituting the first side, and a layer B composed of a resin composition (b) and disposed closer to the second side than the layer A. Here, the resin composition (a) contains 50 wt % or more of a filler. The pressure-sensitive adhesive tape has a tensile strength FT of 35 N/15 mm or more and 145 N/15 mm or less, measured as the maximum tensile load [N/15 mm] when a 15 mm wide test _piece is stretched to break under conditions of 23°C and 50% RH using a tensile tester with a chuck distance of 15 mm and a pulling rate of 300 mm/min.

In the pressure-sensitive adhesive tape having the above configuration, it is advantageous for the resin composition (a) constituting Layer A of the substrate (i.e., the layer disposed on the pressure-sensitive adhesive layer side) to contain 50 wt % or more of a filler, in terms of enhancing plastic deformability to conform to irregularities that may exist on the surface of the adherend (e.g., the irregularities of a rough surface such as a paved surface). Furthermore, since the tensile strength _FT of the pressure-sensitive adhesive tape is limited to 145 N/15 mm or less, the plastic deformability of Layer A can be utilized to appropriately achieve the effect of allowing the entire pressure-sensitive adhesive tape to conform well to the irregularities of the adherend surface. Pressure-sensitive adhesive tapes that have good conformability (adhesion) to the irregularities of the adherend surface are preferred because they are more likely to prevent lifting or peeling from the adherend. Furthermore, since the pressure-sensitive adhesive tape has a tensile strength _FT of 35 N/15 mm or more, it is suitable for preventing tearing or chipping due to insufficient strength of the pressure-sensitive adhesive tape itself. Therefore, with an adhesive tape of the above configuration, even in a situation where the tape is attached to a rough surface and is subjected to frequent strong stress from above, it is possible to prevent the adhesive tape from lifting or peeling off from the rough surface, or damage to the adhesive tape itself, thereby improving the service life of the adhesive tape.

In some embodiments of the pressure-sensitive adhesive tape disclosed herein, the pressure-sensitive adhesive tape preferably has a sag of 55 mm or more as measured by the following method: A pressure-sensitive adhesive tape having a sag of 55 mm or more can more effectively utilize the plastic deformability of Layer A to allow the entire pressure-sensitive adhesive tape to conform well to the irregularities of the surface of an adherend.
[Sagging measurement]
In an environment of 23°C and 50% RH, a test piece having a width of 50 mm and a length of 300 mm is held cantilevered on a horizontal holding stand with the adhesive layer side facing downwards so that a range from one end of the test piece to a length of 100 mm extends outward from the holding stand, and after leaving it to stand for 10 minutes, the difference in height between the upper surface of the holding stand and one end of the test piece is measured.

The resin composition (a) constituting Layer A of the substrate preferably contains an elastomer as the base resin. The pressure-sensitive adhesive tape disclosed herein can be suitably implemented in an embodiment that includes a substrate having Layer A composed of resin composition (a) that contains an elastomer as the base resin and 50% by weight or more of a filler.

In some preferred embodiments, resin composition (b) constituting Layer B of the substrate may be a composition containing a polyolefin-based resin as a base resin. For example, in an adhesive tape in which the second surface of the substrate is constituted by Layer B and the second surface also serves as the back surface of the adhesive tape, resin composition (b) containing a polyolefin-based resin as a base resin may be advantageous from the perspective of the stain resistance of the back surface of the adhesive tape.

In some embodiments, the substrate preferably has a ratio (T _A /T _B ) of the thickness T _A [μm] of Layer A to the thickness T _B [μm] of Layer B of 0.5 or more and 10 or less. A substrate having a ratio (T _A /T _B ) within the above range makes it easy to realize an adhesive tape that favorably combines conformability to rough surfaces (e.g., paved surfaces) with durability against stress from the back surface of the adhesive tape (e.g., stress associated with the passage of vehicles).

In some preferred embodiments, the total thickness of the adhesive tape is 2000 μm or less. Having a total thickness that is not too large is advantageous from the perspective of minimizing unevenness that occurs on the adherend (e.g., paved surface) when the adhesive tape is applied.

In some embodiments of the pressure-sensitive adhesive tape disclosed herein, the total thickness (T _P +T _{A )} of the thickness T _P [μm] of the pressure-sensitive adhesive layer and the thickness T _A [μm] of Layer A is 150 μm or more. A pressure-sensitive adhesive tape having a total thickness (T _P +T _A ) of the pressure-sensitive adhesive layer and Layer A of 150 μm or more is preferred because, even if the adherend is a rough surface such as a paved surface, the pressure-sensitive adhesive layer and Layer A can be easily deformed and the pressure-sensitive adhesive layer and Layer A can be easily deformed and the pressure-sensitive adhesive layer and Layer A can be easily deformed and the pressure-sensitive adhesive tape can be easily conformed to the rough surface.

In some embodiments of the adhesive tape disclosed herein, an acrylic adhesive layer may be preferably used as the adhesive layer of the adhesive tape. For adhesive tapes intended for outdoor use (for example, use in a form in which the tape is attached to outdoor pavement), it is particularly preferable that the adhesive layer be an acrylic adhesive layer from the standpoints of weather resistance, heat resistance, etc.

The adhesive tape disclosed herein is suitable for use on outdoor pavement surfaces, as it offers a good balance between conformability to rough surfaces and durability against backside stress. In particular, the benefits of applying the technology disclosed herein can be best achieved when the tape is applied to outdoor pavement surfaces over which vehicles frequently pass.

The adhesive tapes disclosed herein can be preferably used, for example, as marking adhesive tapes. Therefore, this specification provides a marking adhesive tape made from any of the adhesive tapes disclosed herein.

In addition, appropriate combinations of the elements described in this specification may also be included within the scope of the invention for which patent protection is sought through this patent application.

1 is a cross-sectional view schematically illustrating a pressure-sensitive adhesive tape according to an embodiment. FIG. 2 is an explanatory diagram schematically showing a method for measuring sagging.

Preferred embodiments of the present invention will be described below. Matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings on carrying out the invention described in this specification and the common general technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field.
In the following drawings, components and parts that perform the same function may be denoted by the same reference numerals, and duplicated explanations may be omitted or simplified. Furthermore, the embodiments shown in the drawings are schematic in order to clearly explain the present invention, and do not necessarily accurately represent the size or scale of the actual product.

<Adhesive tape structure example>
The adhesive tape disclosed herein includes a substrate and an adhesive layer disposed on a first surface of the substrate. The concept of "adhesive tape" in this specification may include what is called an "adhesive sheet." The adhesive tape disclosed herein typically has a shape in which the longitudinal dimension is larger than the width dimension, and is preferably configured in a strip shape in which the longitudinal dimension is larger than the width dimension. In an adhesive tape having a substrate configured to include a resin film, the machine direction (MD) of the resin film generally corresponds to the longitudinal direction of the adhesive tape.

An example of the configuration of an adhesive tape according to one embodiment is shown in FIG. 1. This adhesive tape 1 comprises a sheet-like substrate 10 having a first side 10A and a second side 10B, and an adhesive layer 20 disposed on the first side 10A. The substrate 10 has a laminated structure (a two-layer or three-layer multilayer structure; in this embodiment, a two-layer structure) including at least an A layer and a B layer, each having a different composition. The A layer constitutes the first side 10A of the substrate 10 and is composed of a resin composition (a) containing 50% or more by weight of a filler. The B layer is disposed closer to the second side 10B of the substrate 10 than the A layer and is composed of a resin composition (b) having a different composition from the resin composition (a). In the example shown in FIG. 1, the substrate 10 is a two-layer resin film in which the A layer 12, which constitutes the first side 10A, and the B layer 14, which constitutes the second side 10B, are laminated in direct contact with each other. The second surface 10B of the substrate 10 also serves as the back surface of the adhesive tape 1 (the surface opposite to the adhesive surface 20A). The substrate 10 may further include an auxiliary layer (not shown) as an optional component. The A layer 12 may be a resin layer containing an elastomer as a base resin and 50% by weight or more of a filler. The B layer 14 may be a resin layer containing a polyolefin resin and/or an ethylene-vinyl acetate copolymer as a base resin. The B layer 14 may or may not contain a filler.

Before use (i.e., before application to an adherend), the adhesive tape 1 may be in the form of an adhesive tape roll, for example, wound longitudinally so that the adhesive layer 20 abuts against the second surface 10B of the substrate (which may also serve as the back surface of the adhesive tape), thereby protecting its surface (adhesive surface) 20A. Alternatively, the adhesive tape before use may be in a form in which the surface of the adhesive layer is protected by a release liner that is separate from the adhesive tape and at least the side facing the adhesive layer serves as a release surface. Any known or commonly used release liner can be used without particular limitation. For example, a release liner having a release-treated layer on the surface of a substrate such as plastic film or paper, or a release liner made of a low-adhesion material such as a fluorine-based polymer (e.g., polytetrafluoroethylene) or a polyolefin-based resin (e.g., polyethylene or polypropylene), can be used.

<Base material>
The substrate of the pressure-sensitive adhesive tape disclosed herein has a first side, which is the surface on which the pressure-sensitive adhesive layer is disposed, and a second side, which is the surface opposite to the first side. The substrate includes at least Layer A, which constitutes the first side, and Layer B, which is disposed closer to the second side than Layer A. Hereinafter, Layer A may be referred to as the "inner layer" and Layer B may be referred to as the "outer layer" based on their relative positional relationship when attached to an adherend.

(Layer A (inner layer))
Layer A of the substrate is a layer composed of a resin composition (a) containing 50% by weight or more of a filler. As the filler, any of organic fillers, inorganic fillers, and organic-inorganic composite fillers can be used. The filler may be subjected to a known or conventional surface treatment. From the viewpoints of cost and availability, inorganic fillers are preferably used.

Examples of inorganic fillers include calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, calcium hydroxide, potassium hydroxide, barium hydroxide, zirconium oxide, magnesium oxide, zinc oxide, titanium oxide, molybdenum oxide, hydrotalcite, smectite, zeolite, zinc borate, anhydrous zinc borate, zinc metaborate, barium metaborate, antimony oxide, antimony trioxide, antimony pentoxide, red phosphorus, talc, alumina, silica, boehmite, bentonite, sodium silicate, calcium silicate, calcium sulfate, and carbon black. Of these, calcium carbonate, magnesium carbonate, hydrotalcite, talc, alumina, silica, calcium silicate, and calcium sulfate are preferred, with calcium carbonate being more preferred.

The average particle size of the filler is not particularly limited and may be, for example, about 0.1 μm to 100 μm. In some embodiments, the average particle size of the filler is preferably 0.5 μm or more, may be 1 μm or more, or may be 3 μm or more, from the viewpoints of handleability, dispersibility, etc. In some embodiments, the average particle size of the filler is suitably 70 μm or less, preferably 50 μm, may be 30 μm or less, 20 μm or less, 15 μm or less, or may be 10 μm or less (e.g., 7 μm or less), from the viewpoint of easily imparting appropriate plastic deformability to layer A.
In this specification, unless otherwise specified, the term "average particle size" refers to the particle size at an integrated value of 50% in the particle size distribution measured using a particle size distribution measuring device based on a laser diffraction scattering method (50% volume average particle size).

The filler content in resin composition (a) (which typically corresponds to the filler content in Layer A) is not particularly limited and can be set appropriately within the range of 50% by weight or more and less than 100% by weight. In some embodiments, the filler content in Layer A may be, for example, 95% by weight, 90% by weight or less, less than 90% by weight, 88% by weight or less, 85% by weight or less, 80% by weight or less, or 75% by weight or less, from the viewpoint of the ease of molding Layer A and the ease of manufacturing the substrate. Furthermore, the filler content in Layer A may be, for example, more than 50% by weight, 52% by weight or more, 55% by weight or more, 60% by weight or more, or 65% by weight or more, from the viewpoint of easily imparting appropriate brittleness (which may also be understood as low plastic deformability or toughness) to Layer A.

The base resin of the resin composition (a) can be appropriately selected from various resins that can be used for the substrate of a pressure-sensitive adhesive tape. In some preferred embodiments, an elastomer is used as the base resin. Non-limiting examples of the elastomer include ethylene-vinyl acetate copolymer (EVA), ethylene-propylene rubber, thermoplastic polyolefin elastomer (TPO), thermoplastic polyurethane elastomer (TPU), thermoplastic polyester elastomer (TPEE), polyvinyl chloride, (meth)acrylate-butadiene-styrene copolymer (e.g., methyl methacrylate-butadiene-styrene copolymer), acrylonitrile-butadiene-styrene copolymer, acrylonitrile-butadiene copolymer (NBR), styrene-butadiene copolymer, styrene-butadiene-styrene copolymer, other synthetic rubbers (isoprene rubber, butadiene rubber, etc.), and the like. These can be used alone or in appropriate combination of two or more. Among these, EVA is a preferred base resin. For example, EVA having a vinyl acetate content of about 5 to 50% by weight (preferably about 10 to 47% by weight, e.g., about 15 to 45% by weight) can be used. Commercially available EVA products include Ultrathene series (trade name) manufactured by Tosoh and Evaflex series (trade name) manufactured by Mitsui Dow Polychemicals.
The base resin of Layer A refers to the resin component that constitutes Layer A. The same applies to the base resin of Layer B, which will be described later.

From the viewpoint of adhesion to irregularities that may exist on the surface of the adherend (for example, the irregularities of a rough surface such as a paved surface), the thickness of layer A (T _A ) is suitably approximately 50 μm or more, advantageously 100 μm or more, preferably 150 μm or more, more preferably 200 μm or more, and may be 300 μm or more, 400 μm or more, 500 μm or more, 600 μm or more, or 700 μm or more. Furthermore, from the viewpoint of suppressing the height of steps that occur on the adherend by applying the adhesive tape, the thickness of layer A is suitably approximately 1800 μm or less, preferably 1600 μm or less, may be 1400 μm or less, 1200 μm or less, 1000 μm or less, or may be 900 μm or less.

(B layer (outer layer))
Layer B of the substrate is a layer composed of resin composition (b). The base resin of resin composition (b) can be appropriately selected from various resins that can be used as resin materials for forming substrates of pressure-sensitive adhesive tapes. Suitable examples of base resins that can form pressure-sensitive adhesive tapes that combine durability with conformability to rough surfaces such as road surfaces include polyolefin resins and ethylene-vinyl acetate copolymers (EVA). Other examples of materials that can be used as the base resin of resin composition (b) include the materials exemplified as base resins that can be used in resin composition (a). The base resin of resin composition (b) can be used alone or in appropriate combination of two or more types. Among these, polyolefin resins are preferred. Using a polyolefin resin as the base resin of resin composition (b) can be advantageous from the perspective of the stain resistance of the pressure-sensitive adhesive tape. This is particularly significant, for example, in a configuration in which layer B constitutes the other surface of the substrate, and this other surface also serves as the back surface of the pressure-sensitive adhesive tape.

As the polyolefin-based resin, one type of polyolefin can be used alone, or two or more types of polyolefins can be used in combination. The polyolefin can be, for example, an α-olefin homopolymer, a copolymer of two or more α-olefins, or a copolymer of one or more α-olefins with other vinyl monomers. Specific examples include polyethylene (PE), polypropylene (PP), ethylene-propylene copolymers such as poly-1-butene, poly-4-methyl-1-pentene, and ethylene-propylene rubber (EPR), ethylene-propylene-butene copolymers, ethylene-butene copolymers, ethylene-vinyl alcohol copolymers, and ethylene-ethyl acrylate copolymers. Examples of PE include linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), medium-density polyethylene, and high-density polyethylene. Suitable examples of PE include LLDPE and LDPE. Among these, LLDPE is preferred.

In some embodiments, a polyolefin-based resin containing a combination of PE and an α-olefin copolymer can be preferably used as the base resin of resin composition (b). Specific examples include a polyolefin-based resin containing LLDPE and an α-olefin copolymer, a polyolefin-based resin containing LDPE and an α-olefin copolymer, and a polyolefin-based resin containing LLDPE, LDPE, and an α-olefin copolymer. The ratio of the amounts of PE and the α-olefin copolymer used, by weight, may be, for example, 5/95 to 95/5, preferably 10/90 to 95/5, more preferably 25/75 to 90/10, 30/70 to 90/10, 30/70 to 85/20, 40/60 to 80/20, or 40/60 to 60/40.

Resin composition (b) may contain a filler in addition to the base resin. Examples of fillers include the same materials described above as fillers that can be used in resin composition (a). The average particle size of the filler used in resin composition (b) can be selected appropriately from the same range as the average particle size of the filler used in resin composition (a).

By appropriately setting the filler content in resin composition (b) (which typically corresponds to the filler content in layer B), it is possible to adjust the tensile strength of layer B, the tensile strength of the adhesive tape, and the sagging of the adhesive tape, as described below. The filler content in layer B can be set as appropriate within a range greater than 0% by weight, and may be, for example, 10% by weight or more, 15% by weight or more, 20% by weight or more or more than 20% by weight, 25% by weight or more, 30% by weight or more, 40% by weight or more, 50% by weight or more, 60% by weight or more, or 65% by weight or more. Furthermore, from the standpoint of the strength and durability of layer B, the filler content in layer B is suitably 95% by weight or less, advantageously 90% by weight or less, preferably less than 90% by weight, more preferably 88% by weight or less, or may be 85% by weight or less, less than 85% by weight, 80% by weight or less, or 75% by weight or less. For example, in embodiments in which the base resin of resin composition (b) is a polyolefin resin, EVA, or a mixture thereof, the filler contents described above can be preferably employed. Furthermore, in some embodiments in which EVA is used as the base resin of resin composition (b), the filler content of layer B is advantageously, for example, 60% by weight or less, preferably 50% by weight or less or less than 50% by weight, and may be 45% by weight or less, 40% by weight or less, or 35% by weight or less.

The thickness of Layer B (T _B ) is suitably 20 μm or more, advantageously 50 μm or more, preferably 75 μm or more, more preferably 100 μm or more, and may be 150 μm or more, 200 μm or more, 300 μm or more, 350 μm or more, or 380 μm or more, from the viewpoint of easily setting one or more of the tensile strength of Layer B, the tensile strength of the adhesive tape, the sagging of the adhesive tape, etc., within an appropriate range. Furthermore, from the viewpoint of suppressing the height of steps that occur on the adherend by applying the adhesive tape, the thickness of Layer B is suitably approximately 1600 μm or less, preferably 1400 μm or less, or may be 1200 μm or less, 1000 μm or less, 800 μm or less, 60 μm or less, or 500 μm or less.

The thickness of the entire substrate, including Layer A and Layer B, is not particularly limited and can be selected depending on the intended use and manner of use of the adhesive tape. The thickness of the substrate can be selected, for example, from a range of approximately 70 μm to approximately 1900 μm. From the perspective of making it easier to extend the service life of the adhesive tape, in some embodiments, the total substrate thickness is suitably 100 μm or more, preferably 200 μm or more, and more preferably 250 μm or more, and may be, for example, 400 μm or more, 600 μm or more, 800 μm or more, 1000 μm or more, or 1100 μm or more. Furthermore, from the viewpoint of reducing the height of steps that occur on the adherend when the pressure-sensitive adhesive tape is applied, in some embodiments, the thickness of the substrate may be, for example, 1980 μm or less, suitably 1950 μm or less, preferably 1900 μm or less, or may be 1800 μm or less, 1600 μm or less, 1500 μm or less, 1400 μm or less, or 1450 μm or less.

In some embodiments, the ratio (T _A /T _B ) of the thickness T _A [μm] of layer A to the thickness T _B [μm] of layer B may be, for example, about 0.2 to 50, and preferably about 0.5 to 10. From the viewpoint of easily exhibiting good conformability to the irregularities of the adherend surface, in some embodiments, the ratio (T _A /T _B ) is suitably 0.7 or more, advantageously 1.0 or more or more than 1.0, preferably 1.2 or more, more preferably 1.5 or more, or may be 1.6 or more, or may be 1.8 or more. Furthermore, from the viewpoint of easily obtaining good durability while avoiding an excessively large total thickness of the pressure-sensitive adhesive tape, the ratio (T _A /T _B ) is suitably 8.0 or less, advantageously 6.0 or less, preferably 4.0 or less, or may be 3.0 or less, or may be 2.5 or less.

From the viewpoint of durability, the substrate of the adhesive tape disclosed herein can be preferably implemented in an embodiment in which at least the above-mentioned Layer A and Layer B are both non-porous resin layers. Here, a non-porous resin layer typically means a resin layer that is substantially bubble-free (for example, one in which the proportion of bubbles in the apparent volume of the substrate is less than 3% by volume, preferably less than 1% by volume). It is preferable that the entire substrate is non-porous.

The resin material constituting each layer of the substrate may contain known additives, such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), slip agents, and antiblocking agents, as needed, provided that the effects of the present invention are not significantly impaired. The amount of additives added is not particularly limited and can be set appropriately to achieve the desired effect.

The method for manufacturing the substrate is not particularly limited, and can be any known method, such as co-extrusion molding of the resin materials that make up each layer, thermal lamination or adhesive lamination of resin films formed individually from each resin material, extrusion lamination of a resin material onto a resin film that makes up a layer, or a combination or repetition of these methods. The resin film can be produced by conventional, commonly known resin film molding methods, such as extrusion molding, inflation molding, T-die casting, calendar roll molding, and calendaring.

The substrate of the adhesive tape disclosed herein may be configured to include at least Layer A and Layer B, and may be a substrate with a two-layer structure consisting of Layer A and Layer B, or a substrate with a structure that further includes one or more layers different from Layer A and Layer B (hereinafter also referred to as optional layers). In some embodiments using a substrate with a structure that includes optional layers, from the viewpoint of making it easier to optimally exhibit the effects of including Layer A and Layer B, the combined thickness of Layer A and Layer B is preferably 80% or more of the total thickness of the substrate, and more preferably 90% or more or 95% or more (e.g., 98% or more).

The optional layer may be, for example, an optical property adjusting layer (e.g., a colored layer or an antireflection layer), a printed layer or a laminate layer for imparting a desired appearance to the substrate, an antistatic layer, a hard coat layer provided for the purpose of improving the durability (scratch resistance, abrasion resistance, stain resistance, etc.) of the substrate, or the like, a release layer for imparting releasability to the back surface of the pressure-sensitive adhesive tape (the surface opposite to the adhesive surface), an undercoat layer (primer layer) provided for the purpose of improving the anchoring property of the pressure-sensitive adhesive layer to the substrate or improving the adhesion between the substrate and the hard coat layer, or the like.
As the hard coating agent for forming the hard coating layer, known materials such as acrylic, urethane, urethane acrylate, and silicone materials can be appropriately used. The thickness of the hard coating layer is not particularly limited and can be appropriately set depending on the purpose. In some embodiments, the thickness of the hard coating layer may be, for example, about 0.1 μm to 100 μm, or about 1 μm to 50 μm.
As the release treatment agent for forming the release layer, known materials such as silicone-based, long-chain alkyl-based, fluorine-based, molybdenum sulfide, etc. can be appropriately used. The thickness of the release layer is not particularly limited and can be appropriately set depending on the purpose. In some embodiments, the thickness of the release layer may be, for example, about 0.01 μm to 5 μm, or about 0.05 μm to 3 μm.
The composition of the primer used to form the undercoat layer is not particularly limited and can be appropriately selected from known primers. The thickness of the undercoat layer is not particularly limited and can be appropriately set depending on the purpose. In some embodiments, the thickness of the undercoat layer may be, for example, about 0.01 μm to 1 μm, or about 0.1 μm to 1 μm.

The optional layer may be disposed on the surface of Layer A (between Layer A and the adhesive layer), may constitute the second surface of the substrate (the surface on the back side of the adhesive tape), or may be disposed between Layer A and Layer B. Furthermore, the optional layer may be disposed over the entire area of the substrate, or may be disposed partially.

If necessary, the first surface of the substrate may be subjected to a conventional surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, or alkali treatment. Such a surface treatment may be intended to improve the anchoring ability of the pressure-sensitive adhesive layer to the substrate. The above surface treatments may be applied alone or in combination.

<Adhesive Layer>
The adhesive layer of the adhesive tape disclosed herein can be composed of one or more types of adhesives appropriately selected from various types of adhesives. Examples of such adhesives include, but are not limited to, acrylic adhesives, polyester adhesives, polyamide adhesives, urethane adhesives, rubber adhesives, polyether adhesives, silicone adhesives, and fluorine-based adhesives. Here, an acrylic adhesive refers to an adhesive having an acrylic polymer as the base polymer. Similarly, a polyester adhesive refers to an adhesive having a polyester as the base polymer. The same applies to rubber adhesives and other adhesives. Furthermore, the base polymer of an adhesive refers to the main component of the rubber-like polymer (a polymer that exhibits rubber elasticity at temperatures around room temperature) contained in the adhesive, and typically refers to a component that accounts for more than 50 wt% (e.g., 70 wt% or more, or even 90 wt% or more) of the polymer components. The adhesive tape disclosed herein can be preferably implemented, for example, in an embodiment having an adhesive layer (acrylic adhesive layer) formed using an acrylic adhesive.

In this specification, the term "acrylic polymer" refers to a polymer containing monomer units derived from (meth)acrylic monomers in the polymer structure, and typically refers to a polymer containing more than 50% by weight of monomer units derived from (meth)acrylic monomers. Furthermore, a (meth)acrylic monomer refers to a monomer having at least one (meth)acryloyl group per molecule. Here, "(meth)acryloyl group" refers collectively to acryloyl groups and methacryloyl groups. Therefore, the concept of a (meth)acrylic monomer here encompasses both a monomer having an acryloyl group (acrylic monomer) and a monomer having a methacryloyl group (methacrylic monomer). Similarly, in this specification, "(meth)acrylic acid" refers collectively to acrylic acid and methacrylic acid, and "(meth)acrylate" refers collectively to acrylate and methacrylate.

(acrylic polymer)
The acrylic polymer serving as the base polymer of the acrylic pressure-sensitive adhesive is preferably a polymer of a monomer raw material that contains, for example, an alkyl(meth)acrylate as a main monomer and may further contain a sub-monomer copolymerizable with the main monomer, where the main monomer is a component that accounts for more than 50% by weight of all monomer components in the monomer raw material.

As the alkyl(meth)acrylate, for example, a compound represented by the following formula (1) can be suitably used.
CH ₂ =C(R ¹ )COOR ² (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. R ² is a chain alkyl group having 1 to 20 carbon atoms (hereinafter, this range of carbon atoms may be referred to as "C _1-20 "). From the viewpoint of the storage modulus of the PSA, alkyl (meth)acrylates in which R ² is a chain alkyl group of C _1-14 (e.g., C _2-10 , typically C _4-9 ) are preferred, and alkyl acrylates in which R ¹ is a hydrogen atom and R ² is a chain alkyl group of C _4-9 are more preferred.

Examples of alkyl(meth)acrylates in which R ² is a C _1-20 chain alkyl group include methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, s-butyl(meth)acrylate, pentyl(meth)acrylate, isopentyl(meth)acrylate, hexyl(meth)acrylate, heptyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, octyl(meth)acrylate, isopropyl(meth)acrylate, ... Examples of alkyl (meth)acrylates include octyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. These alkyl (meth)acrylates can be used alone or in combination of two or more. Particularly preferred alkyl (meth)acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA). BA and 2EHA can be used alone or in combination.

The proportion of the main monomer in the total monomer components is preferably about 70% by weight or more (for example, about 85% by weight or more, typically about 90% by weight or more), and is usually preferably about 99.5% by weight or less (for example, about 99% by weight or less). When a _C4-9 alkyl acrylate is used as the monomer component, the proportion of the _C4-9 alkyl acrylate in the alkyl (meth)acrylate contained in the monomer components is preferably about 70% by weight or more, more preferably about 90% by weight or more, and even more preferably about 95% by weight or more (typically about 99% by weight or more and about 100% by weight or less). In a preferred embodiment, the monomer components include at least one of BA and 2EHA. The technology disclosed herein can be preferably practiced, for example, in an embodiment in which the total amount of BA and 2EHA accounts for about 50% by weight or more (typically about 70% by weight or more, for example, about 90% by weight or more) of the total monomer components.

A secondary monomer copolymerizable with the primary alkyl (meth)acrylate monomer can be useful for introducing crosslinking points into the acrylic polymer and for enhancing the cohesive strength of the acrylic polymer. Examples of the secondary monomer include one or more functional group-containing monomers, such as carboxyl group-containing monomers, hydroxyl group-containing monomers, acid anhydride group-containing monomers, amide group-containing monomers, amino group-containing monomers, keto group-containing monomers, monomers with nitrogen atom-containing rings, alkoxysilyl group-containing monomers, imide group-containing monomers, and epoxy group-containing monomers. From the perspective of enhancing cohesive strength, acrylic polymers in which a carboxyl group-containing monomer and/or a hydroxyl group-containing monomer is copolymerized as the secondary monomer are preferred. Suitable examples of carboxyl group-containing monomers include acrylic acid and methacrylic acid. Suitable examples of hydroxyl group-containing monomers include hydroxyalkyl (meth)acrylates, such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate.

The amount of the secondary monomer is not particularly limited and may be selected appropriately so as to achieve the desired cohesive strength. To achieve a good balance between adhesive strength and cohesive strength, the amount of the secondary monomer is typically approximately 0.5% by weight or more of the total monomer components of the acrylic polymer, and preferably approximately 1% by weight or more. Furthermore, the amount of the secondary monomer is typically approximately 30% by weight or less of the total monomer components, and preferably approximately 15% by weight or less (e.g., approximately 10% by weight or less).

The acrylic polymer may be copolymerized with other monomers (other monomers) than those mentioned above. The other monomers can be used, for example, to adjust the glass transition temperature of the acrylic polymer or adjust the adhesive properties (e.g., releasability). Examples of monomers that can improve the cohesive strength of the adhesive include sulfonic acid group-containing monomers, phosphate group-containing monomers, cyano group-containing monomers, vinyl esters (vinyl acetate, vinyl propionate, vinyl laurate, etc.), and aromatic vinyl compounds. The other monomers may be used alone or in combination of two or more. The content of the other monomers is preferably approximately 30% by weight or less (e.g., approximately 10% by weight or less) of the total monomer components, and can be, for example, approximately 0.01% by weight or more (typically, approximately 0.1% by weight or more).

The method for obtaining the acrylic polymer is not particularly limited, and the polymer can be obtained by applying various polymerization methods commonly used for synthesizing acrylic polymers, such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization. Furthermore, the acrylic polymer may be a random copolymer, block copolymer, graft copolymer, or the like. From the viewpoint of productivity, etc., random copolymers are usually preferred.

(Crosslinking agent)
A crosslinking agent may be used in the pressure-sensitive adhesive layer (e.g., an acrylic pressure-sensitive adhesive layer) as needed. Examples of the crosslinking agent include, but are not limited to, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, silicone-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, silane-based crosslinking agents, alkyl-etherified melamine-based crosslinking agents, and metal chelate-based crosslinking agents. The crosslinking agents may be used alone or in combination of two or more. In some embodiments, an epoxy-based crosslinking agent may be preferably used as the crosslinking agent. An epoxy-based crosslinking agent may be used in combination with another crosslinking agent.

When a crosslinking agent is used, its amount is not particularly limited, and can be any amount greater than 0 parts by weight per 100 parts by weight of the solids content of the adhesive (e.g., an acrylic adhesive) to which the crosslinking agent is added, and can be an amount that adequately exhibits its intended effect. For example, the amount of crosslinking agent used can be appropriately set within the range of approximately 0.005 to 15 parts by weight (preferably 1 to 5 parts by weight) per 100 parts by weight of the adhesive, based on the solids content (non-volatile content). In some embodiments, the amount of crosslinking agent used can be, for example, 0.005 parts by weight or more, preferably 0.010 parts by weight or more (e.g., 0.015 parts by weight or more), based on the solids content (non-volatile content), and can be 0.1 parts by weight or more, more than 0.5 parts by weight, 0.7 parts by weight or more, more than 1.0 parts by weight, more than 1.2 parts by weight, more than 1.5 parts by weight, or more than 2.0 parts by weight. In some embodiments, the amount of crosslinking agent used is suitably, for example, 15 parts by weight or less, based on the solids (non-volatile content) and may be 10 parts by weight or less, 5 parts by weight or less, 3 parts by weight or less, 1 part by weight or less, 0.5 parts by weight or less, or 0.1 parts by weight or less (e.g., 0.05 parts by weight or less), per 100 parts by weight of the adhesive. Using an amount of crosslinking agent that is not too large can be advantageous, for example, from the standpoint of the adhesiveness of the adhesive tape to the adherend (which, in the case of an adherend having an uneven surface, can also be understood as the ability to penetrate into the unevenness).

(Tackifier)
The pressure-sensitive adhesive layer may contain a tackifier as needed. The use of a tackifier can improve adhesion to an adherend. Examples of preferred tackifiers include tackifier resins such as rosin resins, terpene resins, petroleum resins, phenolic resins, alkylphenol resins, xylene resins, coumarone-indene resins, alkyd resins, epoxy resins, and hydrogenated versions thereof. Tackifiers can be used alone or in appropriate combinations of two or more. When a tackifier is used, its amount can be determined so as to achieve the desired effect, and is not particularly limited. The amount of tackifier used can be, for example, 5 wt% or more, 10 wt% or more, or 15 wt% or more of the total weight of the pressure-sensitive adhesive layer. The amount of tackifier used can also be, for example, 60 wt% or less, 40 wt% or less, or 30 wt% or less of the total weight of the pressure-sensitive adhesive layer. The pressure-sensitive adhesive tape disclosed herein can also be preferably implemented in an embodiment in which a tackifier is substantially not used.

The adhesive layer may contain appropriate components (additives) that are acceptable for inclusion in the adhesive layer, as needed. Examples of such additives include antistatic agents, colorants (including pigments, dyes, etc.), fillers, antioxidants, and light stabilizers (including radical scavengers, UV absorbers, etc.). These additives may be used alone or in combination of two or more. The amount of each additive may be approximately the same as the amount typically used in the field of adhesive tapes.

(Formation of Pressure-Sensitive Adhesive Layer)
The form of the PSA composition used to form the PSA layer in the technology disclosed herein is not particularly limited. The PSA layer may be formed, for example, from a water-dispersible PSA composition, a solvent-based PSA composition, a hot-melt PSA composition, or an active energy ray-curable PSA composition. The PSA layer can be formed in accordance with known methods for forming PSA layers in PSA tapes. For example, a method (direct method) in which the PSA composition is directly applied (typically coated) to a substrate and dried, or a method (transfer method) in which the PSA composition is applied to a surface with good releasability (e.g., the surface of a release liner, the backside of a release-treated substrate, etc.) and dried to form a PSA layer on the surface, and then the PSA layer is transferred to the substrate, can be used.

The thickness of the adhesive layer is not particularly limited and can be selected depending on the intended use and mode of use of the adhesive tape. The thickness of the adhesive layer can be set appropriately, for example, in the range of 10 μm to 800 μm. For adhesive tapes intended to be attached to substrates with uneven surfaces (e.g., paved surfaces), from the viewpoint of adhesion to the substrate (ability to penetrate into the unevenness), the thickness of the adhesive layer is suitably 20 μm or more, preferably 30 μm or more, more preferably 50 μm or more, and may be 70 μm or more, 80 μm or more, or 90 μm or more. Furthermore, from the viewpoint of productivity of the adhesive tape and suppression of blocking at the edge faces of the adhesive tape (particularly the edge faces along the longitudinal direction), in some embodiments, the thickness of the adhesive layer is suitably 500 μm or less, preferably 400 μm or less, and may be 300 μm or less, 200 μm or less, or 150 μm or less.

<Adhesive tape>
The thickness of the adhesive tape disclosed herein is not particularly limited and can be selected depending on the purpose and mode of use of the adhesive tape. From the viewpoint of easily achieving both good conformability to rough surfaces such as road surfaces and durability, in some embodiments, the thickness of the adhesive tape may be, for example, 80 μm or more, suitably 120 μm or more, preferably 150 μm or more, or may be 250 μm or more, 450 μm or more, 650 μm or more, 850 μm or more, 1000 μm or more, or 1100 μm or more. The thickness of the adhesive tape may be, for example, 2500 μm or less. From the viewpoint of reducing the height of steps that occur on the adherend when the adhesive tape is applied, in some embodiments, the thickness of the adhesive tape is suitably 2000 μm or less, preferably 1800 μm or less, or may be 1600 μm or less, 1500 μm or less, or may be 1400 μm or less. Reducing the height of the step is also advantageous from the viewpoint of preventing chipping of the edge of the adhesive tape when it is attached to an adherend. For example, in a use mode in which a vehicle passes over the adhesive tape attached to a rough surface (such as a paved surface), it is beneficial to prevent chipping of the adhesive tape by reducing the height of the step to a predetermined level or less.

In some embodiments of the pressure-sensitive adhesive tape disclosed herein, the total thickness (T _P +T _A ) of the thickness T _P [μm] of the pressure-sensitive adhesive layer and the thickness T _A [μm] of layer A may be, for example, 60 μm or more, advantageously 100 μm or more, preferably 150 μm or more, more preferably 300 μm or more, or may be 500 μm or more, 700 μm or more, or 800 μm or more. By increasing the total thickness (T _P +T _A ), even if the adherend is a rough surface such as a paved surface, the pressure-sensitive adhesive layer's easy deformability and layer A's plastic deformability tend to make it easier for the pressure-sensitive adhesive tape to conform to the rough surface. [0033] Furthermore, from the viewpoint of suppressing the height of steps that occur on an adherend when the pressure-sensitive adhesive tape is applied, in some embodiments, the total thickness (T _P +T _A ) is suitably 1800 μm or less, preferably 1500 μm or less, and may be 1300 μm or less, 1100 μm or less, or 1000 μm or less. From the viewpoint of suppressing blocking of the pressure-sensitive adhesive tape while exhibiting good conformability to rough surfaces, in some embodiments, the ratio (T _A /T _P ) of the thickness T _A [μm] of layer _A to the thickness T P [μm] of the pressure-sensitive adhesive layer is preferably 1 or more, preferably 3 or more, or may be 5 or more, 6 or more, or may be 7 or more. Furthermore, from the viewpoint of increasing the 90-degree peel strength of the pressure-sensitive adhesive tape, the ratio (T _A /T _P ) is suitably 30 or less, preferably 20 or less, or may be 15 or less, 12 or less, or 10 or less.

(Tensile strength F _T )
The pressure-sensitive adhesive tape disclosed herein has a tensile strength F _T of 35 N/15 mm or more and 145 N/15 mm or less, and may be, for example, 40 N/15 mm or more and 130 N/15 mm or less. From the viewpoint of further improving the durability of the pressure-sensitive adhesive tape (for example, durability under harsh usage conditions such as vehicles passing across a pressure-sensitive adhesive tape attached to a paved surface), in some embodiments, the tensile strength F _T is advantageously 40 N/15 mm or more, preferably 45 N/15 mm or more, more preferably 50 N/15 mm or more, and may be 55 N/15 mm or more, 60 N/15 mm or more, 65 N/15 mm or more, 70 N/15 mm or more, or even 75 N/15 mm or more. In some embodiments, the tensile strength F _T is suitably 110 N/15 mm or less, preferably 100 N/15 mm or less or less than 100 N/15 mm, and may be 95 N/15 mm or less, 90 N/15 mm or less, or 85 N/15 mm or less. Having a tensile strength F _T that is not too high can be advantageous from the perspective of effectively utilizing the plastic deformability of Layer A to improve the overall conformability of the adhesive tape to rough surfaces (e.g., paved surfaces). The tensile strength F _T can be adjusted by selecting the structure of the substrate, the composition of each layer, the manufacturing method of the substrate, etc.

The tensile strength _FT of an adhesive tape is measured in accordance with JIS K 7127:1999. Specifically, the tensile strength _FT of an adhesive tape is measured by stretching a 15 mm wide test piece to break using a tensile tester at a chuck distance of 15 mm and a tensile speed of 300 mm/min under an environment of 23°C and 50% RH, and measuring the maximum tensile load [N/15 mm] at that time. The test piece can be prepared, for example, by appropriately cutting the adhesive tape to be evaluated. It is desirable to prepare the test piece so that the direction in which the test piece is stretched during measurement of the tensile strength _FT is the longitudinal direction of the adhesive tape (typically the machine direction (MD)). The tensile tester may be an "Autograph AGS-J" manufactured by Shimadzu Corporation. The length of the test piece may be any length that can be set in the tensile tester with a chuck distance of 15 mm, and is suitably, for example, approximately 50 mm. A similar measurement method is also employed in the examples described below.

Although not particularly limited, in the pressure-sensitive adhesive tape disclosed herein, the tensile strength _Ft , which is measured by stretching a test piece until it breaks in a direction (typically, the width direction (TD) of the pressure-sensitive adhesive tape) perpendicular to the direction in which the test piece is stretched when measuring the tensile strength _Ft , may be, for example, 15 N/15 mm or more (advantageously, 20 N/15 mm or more). The tensile strength _Ft is measured in the same manner as the measurement of the tensile strength _Ft , except for the stretching direction of the test piece during measurement. From the viewpoint of improving the durability of the pressure-sensitive adhesive tape, in some embodiments, the tensile strength _Ft is preferably 25 N/15 mm or more, more preferably 30 N/15 mm or more, and may be 35 N/15 mm or more, 40 N/15 mm or more, 48 N/15 mm or more, 50 N/15 mm or more, or 55 N/15 mm or more. The tensile strength _Ft may be, for example, 200 N/15 mm or less, and from the viewpoint of conformability, etc., it is appropriate to be 150 N/15 mm or less, advantageously 140 N/15 mm or less, preferably 120 N/15 mm or less, more preferably 110 N/15 mm or less, 100 N/15 mm or less or less than 100 N/15 mm, 95 N/15 mm or less, 90 N/15 mm or less, 85 N/15 mm or less, 80 N/15 mm or less, or 75 N/15 mm or less. The tensile strength _Ft can be adjusted by selecting the structure of the substrate, the composition of each layer, the manufacturing method of the substrate, etc.

The absolute value of the difference between the tensile strength F _T [N/15 mm] and the tensile strength F _t [N/15 mm], i.e., |F _T - _{F t} |, is not particularly limited, but from the viewpoint of reducing the directional dependency in the plane direction and improving performance stability, it is advantageous for it not to be too large. In some embodiments, |F _T - _{F t} | is preferably 20 N/15 mm or less, more preferably 15 N/15 mm or less, and may be 11 N/15 mm or less, or may be 9.0 N/15 mm or less. Theoretically, the lower limit of |F _T - _{F t} | is 0.0 N/15 mm. From the practical viewpoint of productivity, cost, etc., in some embodiments, |F _T - _{F t} | may be, for example, 0.1 N/15 mm or more, 0.2 N/15 mm or more, 0.5 N/15 mm or more, 1.0 N/15 mm or more, 3.0 N/15 mm or more, or 5.0 N/15 mm or more. The relative magnitude relationship between _{F T} and F _t may be F _T > F _t , F _T = F _t , or F _T < F _t . In some preferred embodiments, F _T ≧ F _t (typically F _T > F _t ). The pressure-sensitive adhesive tapes according to the examples (Examples 1 to 8) described below all had F _T - F _t within the range of 5.0 to 15 N/15 mm.

(Tensile strength F _B )
In some embodiments of the pressure-sensitive adhesive tape disclosed herein, the tensile strength F _B of layer B constituting the substrate of the pressure-sensitive adhesive tape is suitably 15 N/15 mm or more, preferably 18 N/15 mm or more, more preferably 20 N/15 mm or more, and may be 25 N/15 mm or more, 28 N/15 mm or more, or even 30 N/mm or more. Layer B exhibiting such a tensile strength F _B facilitates the realization of a highly durable pressure-sensitive adhesive tape. Furthermore, the tensile strength F _B of layer B may be, for example, 75 N/15 mm or less. From the viewpoint of avoiding impairment of the plastic deformability of layer A, it is suitably 70 N/15 mm or less or less than 70 N/15 mm, advantageously 65 N/15 mm or less, preferably 60 N/15 mm or less, more preferably 58 N/15 mm or less, and may be 55 N/15 mm or less, or may be 50 N/15 mm or less. The tensile strength F _B can be adjusted by selecting the composition, thickness, and forming method of the B layer.

The tensile strength F _B of layer B is measured as follows. That is, a single-layer resin film consisting of layer B of a substrate is prepared. For example, a single-layer resin film having the same thickness as layer B of the substrate is produced using resin composition (b) constituting layer B of the substrate. Except for using this resin film as the evaluation object, the tensile strength F _B of layer B can be measured in the same manner as the tensile strength F _T of an adhesive tape. A similar measurement method is also used in the examples described below.

Although not particularly limited, in Layer B constituting the substrate of the pressure-sensitive adhesive tape disclosed herein, the tensile strength _Fb , measured by stretching a test piece until it breaks in a direction (typically TD) perpendicular to the direction in which the test piece is stretched when measuring the tensile strength _Fb , may be, for example, 5.0 N/15 mm or more (advantageously, 8.0 N/15 mm or more). The tensile strength _Fb is measured in the same manner as the measurement of the tensile strength _Fb , except for the stretching direction of the test piece during measurement. From the viewpoint of improving the durability of the pressure-sensitive adhesive tape, in some embodiments, the tensile strength _Fb is preferably 10 N/15 mm or more, more preferably 15 N/15 mm or more, and may be 18 N/15 mm or more, 20 N/15 mm or more, 23 N/15 mm or more, or 25 N/15 mm or more. The tensile strength _Fb may be, for example, 75 N/15 mm or less, or 70 N/15 mm or less, and is advantageously 65 N/15 mm or less from the viewpoint of conformability, etc., and is preferably 60 N/15 mm or less or less than 60 N/15 mm, more preferably 55 N/15 mm or less, and may be 50 N/15 mm or less, 48 N/15 mm or less, or 46 N/15 mm or less. The tensile strength _Fb can be adjusted by selecting the composition, thickness, formation method, etc. of layer B.

The absolute value of the difference between the tensile strength F _B [N/15 mm] and the tensile strength F _b [N/15 mm], i.e., |F _B - _{F b} |, is not particularly limited. From the viewpoint of reducing the directional dependency in the in-plane direction, in some embodiments, |F _B - F _b | is preferably 10 N/15 mm or less, more preferably 8.0 N/15 mm or less, and may be 6.0 N/15 mm or less, 5.0 N/15 mm or less, or 4.0 N/15 mm or less. Theoretically, the lower limit of |F _B - F _b | is 0 N/15 mm. From the practical viewpoint of productivity, cost, and the like, in some embodiments, |F _B - F _b | may be, for example, 0.1 N/15 mm or more, 0.5 N/15 mm or more, 1.0 N/15 mm or more, 1.5 N/15 mm or more, 2.0 N/15 mm or more, 2.5 N/15 mm or more, or 3.0 N/15 mm or more. The relative magnitude relationship between F _B and F _b may be F _B > F _b , F _B = F _b , or F _B < F _b . In some preferred embodiments, F _B ≧ F _b (typically F _B > F _b ). The layer B constituting the substrate of the pressure-sensitive adhesive tape according to the examples (Examples 1 to 8) described below all had F _B - F _b in the range of 2.0 to 5.0 N/15 mm.

Although not particularly limited thereto, in some embodiments of the pressure-sensitive adhesive tape disclosed herein, the pressure-sensitive adhesive tape satisfies the following inequality (1):
(F _B /T _B )>(F _T /T _S ) (1);
It is preferable that the following is satisfied. In the above inequality (1), T _B is the thickness [μm] of Layer B, and T _S is the thickness [μm] of the substrate. That is, it is preferable that the value obtained by dividing the tensile strength F _B [N/15 mm] of Layer B by the thickness T _B [μm] of Layer B is greater than the value obtained by dividing the tensile strength F _B [N/15 mm] of the pressure-sensitive adhesive tape by the thickness T _S [μm] of the substrate. Here, T _B in the above inequality (1) is the numerical part when the thickness of Layer B is expressed in units of μm, and T B itself is a dimensionless number having no unit. The same applies to F _T , T _B , and T _S in the above inequality (1). In addition, the reason why the denominator on the right-hand side of the above inequality (1) is the thickness of the substrate rather than the thickness of _the pressure-sensitive adhesive tape is that the tensile strength of the pressure-sensitive adhesive tape can be understood as an approximate value of the tensile strength of the substrate, since the tensile strength of the pressure-sensitive adhesive layer is generally significantly smaller than the tensile strength of the substrate. In other words, the above inequality (1) shows that when the tensile strength of the substrate (approximate to the tensile strength of a pressure-sensitive adhesive tape) and the tensile strength of Layer B are converted into values per thickness, the presence of Layer B increases the tensile strength of the entire substrate.

(sagging)
In some embodiments of the pressure-sensitive adhesive tape disclosed herein, the pressure-sensitive adhesive tape preferably has a sag of 55 mm or more. Higher sag of a pressure-sensitive adhesive tape indicates that the pressure-sensitive adhesive tape is more easily deformed. Therefore, a pressure-sensitive adhesive tape with a sag of 55 mm or more can effectively conform the entire pressure-sensitive adhesive tape to the irregularities of the adherend surface by utilizing the plastic deformability of Layer A of the substrate. The sag is more preferably 58 mm or more, even more preferably 60 mm or more or more than 60 mm, and may be 62 mm or more or 64 mm or more. On the other hand, from the viewpoint of the durability of the pressure-sensitive adhesive tape, it is advantageous for the sag not to be too high. From this viewpoint, in some embodiments, the sag is suitably 80 mm or less, advantageously 78 mm or less or 75 mm or less, preferably less than 75 mm, and may be 73 mm or less, 70 mm or less, or 68 mm or less. The sag can be adjusted by selecting the structure of the substrate, the composition of each layer, the method of manufacturing the substrate, the thickness of the pressure-sensitive adhesive tape, etc.

The sagging of adhesive tapes is measured as follows: A 50 mm wide, 300 mm long test piece is cantilevered on a horizontal table at 23°C and 50% RH, with the adhesive side facing downwards. The test piece is then extended 100 mm from one end of the test piece beyond the table. After leaving the test piece for 10 minutes, the height difference between the top surface of the table and the end of the test piece is measured. The test piece can be prepared, for example, by cutting the adhesive tape to be evaluated. It is desirable to prepare the test piece so that its longitudinal direction coincides with the longitudinal direction of the adhesive tape. More specifically, as shown in Figure 2, a test piece 32 measuring 50 mm wide and 300 mm long is attached to the top surface of the holder 30 so that a 100 mm long section from one end 32A of the test piece 32 extends outward from the horizontal holder 30, perpendicular to the outer edge of the holder 30, and a 200 mm long section from the other end 32B of the test piece 32 is attached to the top surface of the holder 30. A weight 34 is then placed on top of the test piece 32, thereby holding the test piece 32 cantilevered on the holder 30. After leaving the test piece 32 stationary for 10 minutes, the difference in height (hanging height) L1 between the top surface of the holder 32 and one end 32A of the test piece 32 is measured, and this value is used as the measurement value of sagging [mm].

(90 degree peel strength)
In some embodiments of the pressure-sensitive adhesive tape disclosed herein, the pressure-sensitive adhesive tape suitably has a 90-degree peel strength (hereinafter also simply referred to as "90-degree peel strength") from a stainless steel plate of 5.0 N/20 mm or more, advantageously 7.0 N/20 mm or more, and preferably 10.0 N/20 mm or more. From the viewpoint of improving peel resistance, in some embodiments, the 90-degree peel strength of the pressure-sensitive adhesive tape may be 13.0 N/20 mm or more, 15.0 N/20 mm or more, or 18.0 N/20 mm or more. The upper limit of the 90-degree peel strength is not particularly limited, and may be, for example, 80 N/20 mm or less. In some embodiments, from the viewpoint of ease of peeling when peeling a pressure-sensitive adhesive tape attached to an adherend from the adherend and replacing it with a new pressure-sensitive adhesive tape, the 90-degree peel strength may be, for example, 45 N/20 mm or less, 30 N/20 mm or less, or 25 N/20 mm or less.

The 90-degree peel strength of adhesive tape is measured as follows. Specifically, a measurement sample cut into a 20 mm wide strip is pressed against the surface of a stainless steel plate (SUS 304BA plate) using a 2 kg roller, moving back and forth once, in an environment of 23°C and 50% RH. After leaving the sample in the same environment for 30 minutes, the peel strength (N/20 mm) is measured using a tensile tester in accordance with JIS Z 0237:2000, at a pulling speed of 300 mm/min and a peel angle of 90 degrees. An example of a tensile tester that can be used is the Shimadzu Autograph AGS-J. Measurements are also performed in the examples described below using a similar method.

<Application>
The adhesive tape disclosed herein can be preferably used in an embodiment in which it is attached to a rough surface such as a paved surface (particularly an outdoor paved surface) by taking advantage of its feature of being able to improve the service life even in an embodiment in which the adhesive tape is attached to a rough surface and is frequently subjected to strong stress from above. The paved surface can be, for example, a paved surface made of asphalt, concrete, concrete block, etc. The application effects of the technology disclosed herein can be suitably exhibited in an embodiment in which vehicles (e.g., passenger cars, trucks, forklifts, reach stackers, etc.) pass across the adhesive tape attached to the paved surface.
Furthermore, taking advantage of the above-mentioned features, the adhesive tape disclosed herein can be preferably used, for example, as an adhesive tape for marking, which is suitable for applications such as being stuck on factory premises or roads to indicate no-entry zones or pallet storage areas, marking markers such as vehicle stopping positions or parking lot boundaries, marking information such as destination signs, and forming tiger patterns to attract attention at construction sites or train stations.
Furthermore, the adhesive tape disclosed herein is not limited to applications in which it is attached to paved surfaces, but is also useful for applications in which it is attached to, for example, indoor or outdoor mortar-coated surfaces, block walls, brick walls, stone walls, stone-paved roads, etc.

The following describes several examples of the present invention, but it is not intended that the present invention be limited to those shown in these examples. Note that "parts" and "%" in the following descriptions are by weight unless otherwise specified.

<Materials used>
The materials used to prepare the adhesive tapes in the following experiments are as follows.
PET: Polyethylene terephthalate (PET) film available from Nisshin Chemical Industry Co., Ltd., trade name "Diafoil S100."
EVA: Tosoh's "Ultrathene 636" (ethylene-vinyl acetate copolymer, vinyl acetate content 19%) and Mitsui-Dow Polychemical's "Evaflex EV40LX" (ethylene-vinyl acetate copolymer, vinyl acetate content 41%) were used in a weight ratio of 1:1.
Polyolefin resin: Polyethylene (linear low-density polyethylene manufactured by Tosoh Corporation, product name "Nipolon-L F21") and α-olefin copolymer (ethylene-α-olefin copolymer manufactured by Mitsui Chemicals, product name "Tafmer A 4070S") were used in a weight ratio of 1:1. In Table 1, this is abbreviated as "polyolefin."
Filler: calcium carbonate (manufactured by Takehara Chemical Industry Co., Ltd., average particle size 4.5 μm).
Adhesive composition: Toyochem's two-component curing acrylic solvent-based adhesive. Just before use, 0.02 parts of epoxy crosslinking agent as a curing agent was mixed with 100 parts of the base material, which contains 40-50% acrylic ester copolymer and 5-15% tackifier resin in an organic solvent (both on a non-volatile basis).

Example 1
A two-layer resin film (substrate) consisting of an 800 μm-thick A layer and a 400 μm-thick B layer was produced by calendaring using a raw material for A layer containing 50% EVA and 50% filler and a raw material for B layer containing 67% polyolefin resin and filler.
A release liner was prepared, with one side of a 38 μm-thick PET film being a release surface made of a silicone-based release agent. The above-described pressure-sensitive adhesive composition was applied to the release surface of this release liner and dried at 100° C. for 2 minutes to form a 100 μm-thick pressure-sensitive adhesive layer. This pressure-sensitive adhesive layer was then bonded to the first side (the surface on the Layer A side) of the resin film to obtain a pressure-sensitive adhesive tape according to this example.

<Examples 2 to 5, Comparative Example 1>
The adhesive tapes according to each example were produced in the same manner as in Example 1, except that the compositions of the raw materials for the A layer and the B layer used to produce the substrate were as shown in Table 1.

<Comparative Examples 2 and 3>
A T-die film molding machine was used to melt-knead and extrude the raw materials for Layer A having the composition shown in Table 1 below, to produce a resin film having a single layer structure and a thickness of 1,200 μm, consisting of Layer A. Pressure-sensitive adhesive tapes according to each example were produced in the same manner as in Example 1, except that the above resin film was used as the substrate.

<Comparative Example 4>
An adhesive tape according to this example was produced in the same manner as in Example 1, except that a 205 μm thick PET film (Nisshin Chemical Industries, trade name "Diafoil S100") was used as the substrate.

Comparative Example 5
A two-layer resin film (substrate) was produced by melt-kneading the raw materials for Layer A having the composition shown in Table 1, and extrusion-laminated the 800 μm-thick Layer A onto one side of a 38 μm-thick PET film (Nisshin Chemical Industries, product name "Diafoil S100") serving as Layer B. The pressure-sensitive adhesive tape according to this example was produced in the same manner as in Example 1, except that this resin film was used as the substrate.

<Examples 6 to 8, Comparative Example 6>
The adhesive tapes according to each example were produced in the same manner as in Example 3, except that the composition of the raw material for layer A used in producing the substrate was as shown in Table 2.

<Measurement and Evaluation>
The tensile strength F _T [N/15 mm], sagging [mm], and tensile strength F _B [N/15 mm] of layer B of the obtained pressure-sensitive adhesive tape were measured by the above-mentioned methods. The results are shown in Tables 1 and 2.

(Road compatibility test)
The adhesive tape according to each example was applied to an outdoor asphalt-paved road surface (road surface) in a width of 50 mm and a length of 3 m when the road surface was dry. Specifically, the adhesive tape was placed on the road surface and lightly pressed by hand, then struck from above (i.e., from the back of the adhesive tape) with a hammer, and then a vehicle (Toyota L&F electric forklift, model 8FBR15, made one round trip at approximately 2 km/h) was driven to press the tape into the road surface. Thereafter, the degree of penetration (conformity) of the adhesive tape into the unevenness of the road surface was observed, and the road surface conformability was evaluated according to the following three levels. The results are shown in Tables 1 and 2.
AA: It is visible from the back of the adhesive tape that the adhesive tape conforms to the unevenness (undulations) of the road surface (excellent conformability).
A: When the backside of the adhesive tape is rubbed with the hand, the unevenness of the road surface can be felt (good conformability).
B: When the backside of the adhesive tape is rubbed with the hand, the unevenness of the road surface is not felt (poor conformability).

(Durability test)
In the same manner as in the road surface conformability test, a 50 mm wide, 3 m long adhesive tape of each example was applied to an outdoor asphalt-paved road surface. After leaving the adhesive tape for one month in an environment where approximately 20 trucks per day passed across the tape, the degree of damage to the adhesive tape was observed and durability was evaluated using the following three levels. The results are shown in Tables 1 and 2.
AA: No obvious tears or chips in the adhesive tape (excellent durability)
A: Partial chipping was observed on the side edge of the adhesive tape, but sufficient marking function was maintained (good durability).
B: The adhesive tape is torn and the marking function is clearly reduced (poor durability)

The 90-degree peel strength of the adhesive tape of Example 3 was 20.6 N/20 mm, and the 90-degree peel strength of the adhesive tapes of the other Examples was roughly the same.

As shown in Tables 1 and 2, all of the pressure-sensitive adhesive tapes of Examples 1 to 8 exhibited good road conformability and durability. Particularly good results were obtained with the pressure-sensitive adhesive tapes of Examples 2 to 4, 7, and 8. Furthermore, the Examples using a polyolefin resin as the base resin for Layer B exhibited better stain resistance in visual observation after the durability test. On the other hand, Comparative Examples 1 and 6, in which Layer A had too low a filler content, exhibited poor road conformability. Furthermore, a comparison of Examples 2 and 3 with Comparative Example 5, which share the same composition and thickness as Layer A, reveals that the selection of Layer B can impair the road conformability of Layer A. The pressure-sensitive adhesive tapes of Comparative Examples 2 to 4, which used a single-layer substrate, lacked either or both road conformability and durability. Furthermore, when the durability of an adhesive tape produced using a 1,200 μm-thick single-layer substrate formed from the raw material for Layer A of Example 3 instead of the substrate (two-layer substrate) of the pressure-sensitive adhesive tape of Example 3 was evaluated in the same manner as above, it was confirmed that the durability was insufficient (evaluation result: B).

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples given above.

1 Adhesive tape 10 Base material 10A First surface 10B Second surface (rear surface)
12 A layer 14 B layer 20 Adhesive layer 20A Surface (adhesive surface)
30: Holding stand 32: Test piece 32A: One end 32B: Other end 34: Weight L1: Hanging height

Claims (11)

An adhesive tape comprising: a substrate having a first surface and a second surface; and an adhesive layer disposed on the first surface of the substrate;
The substrate includes at least a layer A made of a resin composition (a) and constituting the first surface, and a layer B made of a resin composition (b) and arranged closer to the second surface than the layer A,
The resin composition (a) contains an ethylene-vinyl acetate copolymer as a base resin,
The resin composition (a) contains 50% by weight or more of a filler,
The pressure-sensitive adhesive tape has a tensile strength FT of 35 N/15 mm or more and 145 N/15 mm or less, measured as the maximum tensile load [N/15 mm] when a 15 mm wide test piece is stretched to break using a tensile _tester under conditions of a chuck distance of 15 mm and a tensile speed of 300 mm/min under an environment of 23°C and 50% RH. The pressure-sensitive adhesive tape according to claim 1 , wherein the pressure-sensitive adhesive tape has a sag of 55 mm or more as measured by the following method.
[Sagging measurement]
In an environment of 23°C and 50% RH, a test piece having a width of 50 mm and a length of 300 mm is held in a cantilever on a horizontal holding stand with the side having the adhesive layer facing downwards so that a range from one end of the test piece to a length of 100 mm extends outward from the holding stand, and after leaving it to stand for 10 minutes, the difference in height between the upper surface of the holding stand and one end of the test piece is measured. The pressure-sensitive adhesive tape according to claim 1 or 2, wherein the resin composition (a) contains an elastomer as a base resin. The pressure-sensitive adhesive tape according to any one of claims 1 to 3, wherein the resin composition (b) contains a polyolefin resin as a base resin. The pressure-sensitive adhesive tape according to any one of claims 1 to 4, wherein a ratio (T _A /T _B ) of a thickness T _A [μm] of the A layer to a thickness T _B [μm] of the B layer is 0.5 or more and 10 or less. The adhesive tape according to any one of claims 1 to 5, wherein the thickness of the adhesive tape is 2000 μm or less. The pressure-sensitive adhesive tape according to any one of claims 1 to 6, wherein the total thickness (T _P +T _A ) of the thickness T _P [μm] of the pressure-sensitive adhesive layer and the thickness T _A [μm] of the A layer is 150 μm or more. The adhesive tape according to any one of claims 1 to 7, wherein the adhesive layer is an acrylic adhesive layer. The adhesive tape according to any one of claims 1 to 8 is used by being attached to an outdoor paved surface. The pressure-sensitive adhesive tape according to any one of claims 1 to 9, wherein the ethylene-vinyl acetate copolymer has a vinyl acetate content of 5 to 50% by weight. A marking adhesive tape comprising the adhesive tape according to any one of claims 1 to 10 .