Adhesive tape and method for using adhesive tape

Abstract

Disclosed is an adhesive tape for a concrete structure or a structure having a rust part, the adhesive tape comprising a base material and an adhesive layer that is provided on at least one surface of the base material. The adhesive tape has the total light transmittance of 50% or more, and a difference between the tensile load at 2.5% elongation and the tensile load at 0.5% elongation of 1.3 N / mm or less. The transmittance of ultraviolet light having a wavelength of 340 nm of the base material is 5% or less, and the color difference change rate after performing an accelerated weathering test on the base material for 500 hours is 5 or less.

Description

Adhesive tape, how to use adhesive tape

[0001] The present invention relates to an adhesive tape and a method for using the tape.

[0002] Large structures such as viaducts, tunnels, bridges, steel towers, and tanks are often constructed by combining steel and concrete materials. Steel and concrete materials corrode over time, causing rust, cracks, and other defects. When this corrosion progresses, the corroded areas can be repaired, for example, by applying paint or adhesive to the surface of the structure. However, this repair method requires complex work processes and takes a considerable amount of time before the actual repair work can begin. As a result, there are problems such as the rust progressing further in the corroded areas or pieces of concrete falling off from the corroded areas before the actual repair work can begin.

[0003] One known method for simplifying the repair process for corroded areas is to suppress the progression of corrosion by applying a sheet to the corroded area. However, because the sheet can be highly rigid, the sheet may not be applied properly to the corroded area. In addition, the sheet is often opaque, making it impossible to visually check whether corrosion is progressing inside the sheet. This often results in corrosion progressing without sufficient awareness of the progress of corrosion, and corrosion prevention measures are often not effective. Therefore, as disclosed in Patent Document 1, for example, a laminated sheet with excellent conformability and transparency has been proposed for use in concrete structures or structures with rusted areas.

[0004] JP 2019-64260 A

[0005] However, Patent Document 1 does not discuss the weather resistance of the laminated sheet at all, and there is a risk that the sheet may deteriorate due to ultraviolet rays, etc., when used outdoors for a long period of time, which is a problem in that the laminated sheet is not suitable for long-term outdoor use.

[0006] Therefore, an object of the present invention is to provide an adhesive tape that has excellent conformability and transparency, is highly weather resistant, and is capable of preventing deterioration and discoloration of the adhesive tape even when used outdoors for a long period of time, thereby maintaining excellent corrosion resistance and transparency.

[0007] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by the following configurations. That is, the present invention provides the following [1] to

[20] .

[0008] [1] An adhesive tape for concrete, mortar, underwater materials, or metal materials, comprising a substrate and a pressure-sensitive adhesive layer provided on at least one surface of the substrate, wherein the pressure-sensitive adhesive tape has a total light transmittance of 30% or more, a difference between the tensile load at 2.5% elongation and the tensile load at 0.5% elongation of less than 2.0 N / mm, the substrate has a transmittance of 5% or less for ultraviolet light having a wavelength of 340 nm, and a color difference (ΔE) of 5 or less after 500 hours of accelerated weathering testing. [2] The pressure-sensitive adhesive tape according to [1], wherein the pressure-sensitive adhesive tape has a tensile elongation at break of 100% or more. [3] The pressure-sensitive adhesive tape according to [1] or [2], wherein the pressure-sensitive adhesive tape has a total light transmittance of 30% or more after 500 hours of accelerated weathering testing in accordance with Cycle A of JIS K5600-7-7. [4] The pressure-sensitive adhesive tape according to any one of [1] to [3], wherein the substrate does not break in a peel test conducted after 500 hours of an accelerated weathering test in accordance with Cycle A of JIS K5600-7-7, and the adhesive strength of the pressure-sensitive adhesive layer is 20 N / 25 mm or more. [5] The pressure-sensitive adhesive tape according to any one of [1] to [4], wherein the Elmendorf tear strength of the substrate measured without slits in the Elmendorf tear method in accordance with JIS K7128-2 (1998) is 1.7 N or more. [6] The pressure-sensitive adhesive tape according to any one of [1] to [5], wherein a measurement sample obtained by applying a fluorine-based topcoat paint in accordance with JIS K5659:2018 to a thickness of 25 μm and drying at 23°C for 16 hours to the substrate is subjected to a cross-cut test in accordance with JIS K5600-5-6, and none of the grids peels off. [7] The pressure-sensitive adhesive tape according to any one of [1] to [6], wherein the dimensional change rate of the substrate after immersion in xylene for 5 minutes is 3% or less. [8] The pressure-sensitive adhesive tape according to any one of [1] to [7], wherein the gloss retention rate of the substrate after carrying out the accelerated weather resistance test for 500 hours is 80% or more. [9] The pressure-sensitive adhesive tape according to any one of [1] to [8], wherein the substrate comprises an acrylic resin.

[10] The pressure-sensitive adhesive tape according to any one of [1] to [9], wherein the thickness of the substrate is 20 to 300 μm.

[11] The pressure-sensitive adhesive tape according to any one of [1] to

[10] , wherein the pressure-sensitive adhesive layer has a thickness of 50 to 2500 μm.

[12] The pressure-sensitive adhesive tape according to any one of [1] to

[11] , wherein the pressure-sensitive adhesive layer is formed from a photocurable resin.

[13] The pressure-sensitive adhesive tape according to any one of [1] to

[11] , wherein the pressure-sensitive adhesive layer is formed from an acrylic pressure-sensitive adhesive.

[14] The pressure-sensitive adhesive tape according to any one of [1] to

[13] , wherein the pressure-sensitive adhesive layer has a storage modulus at 23° C. of 50,000 to 1,000,000 Pa.

[15] The pressure-sensitive adhesive tape according to any one of [1] to

[14] , wherein the pressure-sensitive adhesive layer contains a metal having a lower potential than iron.

[16] The pressure-sensitive adhesive tape according to

[15] , wherein the metal having a lower potential than iron is zinc.

[17] The pressure-sensitive adhesive tape according to any one of [1] to

[16] , wherein the pressure-sensitive adhesive layer contains a conductive material other than a metal having a lower potential than iron.

[18] The pressure-sensitive adhesive tape according to

[17] , wherein the conductive material is carbon nanotubes.

[19] A method for using the pressure-sensitive adhesive tape, comprising applying the pressure-sensitive adhesive tape according to any one of [1] to

[18] to a surface of a concrete structure or a structure having rust.

[20] The method for using the pressure-sensitive adhesive tape according to

[19] , wherein a rust progression inhibitor or a primer is applied to the application surface of the pressure-sensitive adhesive tape before applying the pressure-sensitive adhesive tape.

[0009] According to the present invention, it is possible to provide an adhesive tape that has excellent conformability and transparency, is highly weather resistant, and is prevented from deterioration or discoloration even when used outdoors for a long period of time, thereby maintaining excellent corrosion resistance and transparency.

[0010] It is a schematic diagram showing one embodiment of the pressure-sensitive adhesive tape of the present invention. It is a schematic diagram showing one embodiment of the pressure-sensitive adhesive tape of the present invention. It is a schematic diagram showing a method for evaluating the tracking ability of the pressure-sensitive adhesive tape of the present invention. It is a diagram for explaining the evaluation of top coating.

[0011] [Adhesive Tape] The adhesive tape of the present invention is an adhesive tape comprising a substrate and an adhesive layer provided on at least one surface of the substrate.

[0012] <Tensile Load Difference> The pressure-sensitive adhesive tape of the present invention has a difference between the tensile load at 2.5% elongation and the tensile load at 0.5% elongation (hereinafter simply referred to as "tensile load difference") of less than 2.0 N / mm. The tensile load difference essentially means the tensile load per 2% elongation in the elastic region. When the tensile load difference is small, the tape is easily attached to the shape of the adherend (e.g., unevenness, etc.). Furthermore, even when the tape is stretched and attached to the adherend, stress due to shrinkage or the like is less likely to occur after attachment, so the adhesive strength after attachment is easily maintained. When the tensile load difference is 2.0 N / mm or more, the adhesive tape may not be able to fully exhibit its conformability, which may result in problems such as inability to properly attach the tape to adherends with complex shapes. From the viewpoint of fully exhibiting conformability, the tensile load difference is preferably 1.3 N / mm or less. Furthermore, the difference in tensile load is not particularly limited, but from the viewpoint of imparting a certain degree of stiffness and workability to the adhesive tape and effectively preventing defects during application, it is preferably 0.1 N / mm or more, more preferably 0.2 N / mm or more, and even more preferably 0.3 N / mm or more. The difference in tensile load is measured in both the MD and TD directions of the adhesive tape, and the larger of these values ​​is adopted. Furthermore, when the MD and TD directions are unknown, it is preferable to adopt the value with the largest difference in tensile load. The difference in tensile load can be obtained by the measurement method described in the Examples. The same applies to the difference in tensile load of the substrate described below. Furthermore, the difference in tensile load of the adhesive tape can be adjusted within the above range by appropriately selecting the materials used for the substrate and adhesive layer, the thickness of the adhesive tape, etc.

[0013] <Initial Total Light Transmittance> The pressure-sensitive adhesive tape of the present invention has a total light transmittance of 30% or more. The total light transmittance referred to here is measured before the accelerated weathering test described below, and is also referred to as the initial total light transmittance. If the initial total light transmittance is less than 30%, the visibility immediately after the pressure-sensitive adhesive tape is applied to the adherend may be insufficient, and it may be impossible to check the surface condition of the area where the tape is applied immediately after the pressure-sensitive adhesive tape is applied. From this perspective, the initial total light transmittance is preferably 38% or more, more preferably 55% or more. The higher the initial total light transmittance, the better, and it is sufficient if it is 100% or less, but in practice it may be, for example, 97% or less.

[0014] <Total Light Transmittance After Accelerated Weathering Test> The pressure-sensitive adhesive tape of the present invention preferably has a total light transmittance of 30% or more after 500 hours of accelerated weathering test in accordance with Cycle A of JIS K5600-7-7. A total light transmittance of 30% or more ensures excellent visibility even after the pressure-sensitive adhesive tape has been used outdoors for a long period of time, and the progress of corrosion at the location where the pressure-sensitive adhesive tape is applied can be visually confirmed through the tape. From the viewpoint of improving visibility after long-term use, the total light transmittance is preferably 35% or more, more preferably 50% or more. The higher the total light transmittance, the better, and a total light transmittance of 100% or less is sufficient, but in practical use, it is 95% or less.

[0015] <Tensile Elongation at Break> The pressure-sensitive adhesive tape of the present invention preferably has a tensile elongation at break of 100% or more. When the pressure-sensitive adhesive tape has a tensile elongation at break of 100% or more, when the pressure-sensitive adhesive tape is applied in a stretched state, the pressure-sensitive adhesive tape can easily conform to the adherend without tearing, thereby enabling the pressure-sensitive adhesive tape to be properly attached to the adherend. From this perspective, the tensile elongation at break of the pressure-sensitive adhesive tape is more preferably 120% or more, and even more preferably 130% or more. On the other hand, the upper limit of the tensile elongation at break of the pressure-sensitive adhesive tape is not particularly limited, but is preferably 700% or less, more preferably 600% or less, from the viewpoint of mechanical strength, etc. The tensile elongation at break is measured in both the MD and TD directions of the substrate, and the smaller of these values ​​is adopted. Furthermore, when the MD and TD directions are unknown, it is preferable to adopt the smallest tensile elongation at break value. The tensile elongation at break can be obtained by the measurement method described in the Examples. The difference in tensile load and tensile elongation at break of the adhesive tape can be adjusted within the above ranges by appropriately selecting the materials used for the substrate and adhesive layer, the thickness of the adhesive tape, etc.

[0016] <Gloss Retention Rate> The pressure-sensitive adhesive tape of the present invention preferably has a gloss retention rate of 80% or more, more preferably 85% or more, and even more preferably 90% or more, of the substrate after 500 hours of accelerated weathering test in accordance with Cycle A of JIS K5600-7-7. When the gloss retention rate is equal to or greater than the above-mentioned lower limit, it is possible to prevent the adhesive strength of the pressure-sensitive adhesive tape from decreasing or the appearance of the pressure-sensitive adhesive tape from deteriorating when the pressure-sensitive adhesive tape is exposed to light for a long period of time, such as when used outdoors. The higher the gloss retention rate, the better, with the upper limit being 100%. The gloss retention rate of the pressure-sensitive adhesive tape after the accelerated weathering test can be determined by measuring the gloss B of the substrate before the accelerated weathering test and the gloss A of the substrate after the accelerated weathering test, and using the following formula. Details of the measurement method can be performed as described in the Examples below. Gloss retention rate (%) = (gloss B / gloss A) x 100

[0017] <Adhesive Strength> The adhesive tape of the present invention is preferably one in which the substrate does not break and the adhesive strength of the adhesive layer is 20 N / 25 mm or more in a peel test conducted after 500 hours of accelerated weathering testing in accordance with Cycle A of JIS K5600-7-7. When the substrate does not break in the peel test after the accelerated weathering test, the adhesive tape has weather resistance and can be suitable for long-term outdoor use. Furthermore, an adhesive strength of 20 N / 25 mm or more ensures sufficient long-term adhesive strength, prevents peeling from the adherend, and makes it easier to maintain corrosion resistance, etc. From the perspective of maintaining high adhesive strength over a long period of time, the adhesive strength after the accelerated weathering test is more preferably 25 N / 25 mm or more, even more preferably 30 N / 25 mm or more, and even more preferably 40 N / 25 mm or more. The higher the adhesive strength, the better, but in practical terms, it is 200 N / 25 mm or less.

[0018] The adhesive strength of an adhesive tape after an accelerated weather resistance test is measured as follows. The adhesive tape of the present invention is attached to a stainless steel plate (SUS plate) to prepare a sample for adhesive strength evaluation. At this time, the adhesive tape is attached so that the adhesive layer of the adhesive tape comes into contact with the surface of the SUS plate to prepare the sample for adhesive strength evaluation. The size of the adhesive tape is 100 mm in length and 25 mm in width. The adhesive tape is attached to the SUS plate by rolling a 2 kg roller back and forth twice at a speed of 10±0.5 mm / s. An accelerated weather resistance test is performed using the adhesive strength evaluation sample based on Cycle A of JIS K5600-7-7. The test is performed for a total of 500 hours. The adhesive strength of the adhesive strength evaluation sample after the accelerated weather resistance test is measured by an adhesive tape peel test. The peel test is performed using a tensile tester under conditions of 23°C and 50% RH, with a peel angle of 90° and a pulling speed of 300 mm / min, and the average value of the detected load (N) is taken as the adhesive strength. The condition of the substrate can also be confirmed by the peel test.

[0019] <Substrate> (Ultraviolet Transmittance) It is preferable to use a weather-resistant substrate for the adhesive tape of the present invention. By using a weather-resistant substrate, the adhesive tape can be made not only excellent in tracking ability and transparency but also excellent in weather resistance. Even when exposed to light for a long period of time, such as when used outdoors, deterioration and discoloration of the adhesive tape are prevented, and excellent corrosion resistance and transparency can be maintained. Specifically, in the present invention, the substrate for the adhesive tape has a transmittance of ultraviolet light with a wavelength of 340 nm (hereinafter also referred to as "ultraviolet transmittance") of 5% or less. If the ultraviolet transmittance exceeds 5%, the adhesive layer will be deteriorated by ultraviolet light, and the corrosion resistance of the adhesive tape may not be maintained for a long period of time when used outdoors. From this perspective, the ultraviolet transmittance is preferably 3% or less, and more preferably 1% or less. The lower the ultraviolet transmittance, the better, and it is sufficient if it is 0% or more. The ultraviolet transmittance can be obtained by the measurement method described in the examples.

[0020] (Color Difference (ΔE)) Furthermore, the substrate constituting the pressure-sensitive adhesive tape of the present invention has a color difference (ΔE) of 5 or less after undergoing an accelerated weather resistance test for 500 hours. If ΔE exceeds 5, when the pressure-sensitive adhesive tape is used outdoors, the pressure-sensitive adhesive tape may discolor, making it difficult to visually check the progress of corrosion or damage at corroded or damaged areas through the tape. Taking this into consideration, ΔE is preferably 3 or less, and more preferably 1 or less. The lower ΔE is, the better, and ΔE may be 0 or more, but in practice it is, for example, 0.1 or more, preferably 0.2 or more, and more preferably 0.3 or more. The color difference (ΔE) is measured by conducting an accelerated weather resistance test on the substrate for 500 hours, and expressing the difference in color of the substrate before and after the test as the color difference (ΔE).

[0021] As a means for reducing the ultraviolet transmittance of the substrate or reducing the color difference (ΔE), it is possible to reduce the ultraviolet transmittance of the substrate itself or to impart weather resistance. Specifically, it is preferable to use a weather-resistant resin as the resin constituting the substrate, or to blend an ultraviolet absorber, a light stabilizer (HALS), or the like into the resin constituting the substrate. In addition, as a weather-resistant substrate, a weather-resistant film may be formed on the surface of the substrate. It is preferable to form the weather-resistant film on at least one surface of the substrate. The weather-resistant film can be formed, for example, by applying a weather-resistant paint, which is a paint having weather resistance.

[0022] The substrate is preferably a resin film, and examples of resins constituting the resin film include acrylic resins, silicone resins, polycarbonate resins, AES resins, ASA resins, and polyolefins such as polyethylene and polypropylene. These resins may be used alone or in combination of two or more. The silicone resin is not particularly limited, but may be an acrylic silicone resin. The resin film may also contain additives such as an ultraviolet absorber, an antioxidant, and a light stabilizer. The resin preferably contains an acrylic resin, which can easily reduce ultraviolet transmittance and reduce color difference (ΔE). Therefore, it is preferable to use an acrylic resin film as the resin film. Acrylic resin films have strong interatomic bonding strength in the acrylic resin, which is the main component, low ultraviolet transmittance, and can reduce color difference (ΔE) even after long-term use.

[0023] Furthermore, the resin film is preferably a soft resin film, and it is more preferable to use a soft acrylic resin film. The soft resin film may be a film containing a soft component such as a plasticizer. The use of a soft resin film makes it easier to reduce the tensile load difference of the adhesive tape, thereby improving the conformability of the adhesive tape. Furthermore, the use of a soft acrylic resin film among soft resin films can result in a film that has high conformability, low UV transmittance, and small color difference (ΔE) even after long-term use. The resin film used as the substrate may be single-layered or multi-layered. In the case of a multi-layered film, only resin films of the same type may be laminated, or two or more types of resin films may be laminated.

[0024] The substrate may contain additives other than those described above, as long as they satisfy the requirements for ultraviolet transmittance and color difference. Examples of additives include colorants such as pigments and dyes, antistatic agents, flame retardants, mildew inhibitors, antioxidants, leveling agents, flow control agents, antifoaming agents, dispersants, reinforcing fibers, metal oxide particles such as silica, alumina, and titania, antifouling agents, thickeners, and film strength improvers.

[0025] (Cross-Cut Test) The substrate constituting the pressure-sensitive adhesive tape of the present invention preferably has the property that none of the grids peel off when a cross-cut test according to JIS K5600-5-6 is performed on a measurement sample obtained by applying a fluorine-based topcoat paint conforming to JIS K5659:2018 to a thickness of 25 μm and drying at 23 ° C. for 16 hours. The pressure-sensitive adhesive tape of the present invention may have a topcoat paint applied to the tape after being attached to an adherend. Therefore, when the substrate has such physical properties, the adhesion between the substrate and the topcoat paint is improved, making it possible to make the topcoat paint less likely to peel off.

[0026] (Dimensional Change Rate After Immersion in Xylene) The dimensional change rate of the substrate used in the pressure-sensitive adhesive tape of the present invention after immersion in xylene for 5 minutes is preferably 6% or less, more preferably 3% or less, even more preferably 2% or less, and even more preferably 1.5% or less. When the dimensional change rate of the substrate is below the above-mentioned upper limit, the tape is imparted with solvent resistance, and when a top coat paint is applied to an adherend to which the pressure-sensitive adhesive tape is attached, the occurrence of wrinkles in the pressure-sensitive adhesive tape after the paint has dried is prevented, making it easier to maintain a good appearance of the adherend coated with the top coat paint. On the other hand, the lower limit of the range of the dimensional change rate of the substrate used in the pressure-sensitive adhesive tape of the present invention after immersion in xylene for 5 minutes is not particularly limited, but is preferably 0%. The dimensional change rate of the substrate after immersion in xylene can be measured, for example, by the method described in the Examples below. The dimensional change rate of the substrate after immersion in xylene can be adjusted to within the above range by appropriately selecting the materials used for the substrate, etc. When topcoating is performed, it is preferable that the substrate has high adhesion to the topcoat paint and a low rate of dimensional change after immersion in xylene, and from this viewpoint, an acrylic resin film is preferred.

[0027] (Elmendorf Tear Strength) The substrate used in the pressure-sensitive adhesive tape of the present invention preferably has an Elmendorf tear strength of 1.7 N or more, more preferably 3.0 N or more, even more preferably 6.0 N or more, and even more preferably 12 N or more, measured without slits using the Elmendorf tear method in accordance with JIS K7128-2 (1998). When the Elmendorf tear strength of the substrate measured without slits is equal to or greater than the above-mentioned lower limit, excellent conformability is easily imparted to the pressure-sensitive adhesive tape. Furthermore, the higher the Elmendorf tear strength of the substrate measured without slits, the better, and the upper limit of this range is, for example, 16 N. The Elmendorf tear strength of the substrate measured without slits is measured in both the MD and TD directions of the substrate, and the smaller of these values ​​is adopted. Furthermore, when the MD and TD directions are unknown, it is advisable to adopt the smallest Elmendorf tear strength value. The Elmendorf tear strength of a substrate measured without slitting can be measured by the same method as the Elmendorf tear method in accordance with JIS K7128-2 (1998), except that the measurement is performed without slitting. The Elmendorf tear strength of a substrate measured without slitting can be adjusted to fall within the above range by appropriately selecting the material used for the substrate, the thickness of the substrate, and the like.

[0028] The thickness of the substrate is preferably 20 to 300 μm, more preferably 30 to 250 μm, and even more preferably 40 to 230 μm. When the thickness of the substrate is equal to or greater than the lower limit, the substrate can function as a support. When the thickness is equal to or less than the upper limit, the substrate can easily improve its conformability to the adherend and its transparency.

[0029] (Tensile Load Difference) The difference between the tensile load at 2.5% elongation and the tensile load at 0.5% elongation (hereinafter simply referred to as "tensile load difference") of the substrate is preferably less than 2.0 mm / mm, more preferably 1.3 N / mm or less, even more preferably 1 N / mm or less, and even more preferably 0.8 N / mm or less. When the tensile load difference of the substrate is less than 2.0 N / mm, the conformability of the adhesive tape can be further enhanced, making it easier to properly attach it to an adherend with a complex shape. The tensile load difference of the substrate is not particularly limited, but from the viewpoint of imparting a certain degree of stiffness and workability to the adhesive tape and effectively preventing defects during application, it is preferably 0.05 N / mm or more, more preferably 0.08 N / mm or more, and even more preferably 0.1 N / mm or more. The tensile load difference of the substrate can be adjusted within the above range by appropriately selecting the material used for the substrate, the thickness of the substrate, etc.

[0030] <Adhesive Layer> The adhesive tape of the present invention has an adhesive layer on at least one surface of the substrate. The adhesive layer will be described below.

[0031] (Adhesive) The adhesive layer is preferably formed from an adhesive. The type of adhesive is not particularly limited, but examples include acrylic adhesives, rubber adhesives, urethane adhesives, and silicone adhesives. Acrylic adhesives are particularly preferred from the standpoint of weather resistance. These may be used alone or in combination. The adhesive layer is preferably formed from a photocurable resin. As described above, the adhesive tape has a high total light transmittance, so even if the adhesive layer is formed from a photocurable resin, it can be properly cured. By using a photocurable resin for the adhesive layer, a thick film of 100 μm or more can be formed. As a result, the adhesive layer can easily conform to the unevenness of the adherend surface, increasing the adhesive area with the adherend and reducing the risk of peeling. Among photocurable resins, the adhesive layer is preferably formed from an acrylic adhesive. The adhesive layer may be formed from a photocurable main polymer. For example, in the case of an acrylic adhesive, the acrylic polymer may be photocurable.

[0032] (Acrylic pressure-sensitive adhesive) The acrylic pressure-sensitive adhesive is a pressure-sensitive adhesive containing an acrylic polymer obtained by polymerizing a polymerizable monomer containing a (meth)acrylic acid alkyl ester monomer (A). In this specification, the term "(meth)acrylic acid alkyl ester" refers to a concept including both an acrylic acid alkyl ester and a methacrylic acid alkyl ester, and the same applies to other similar terms. In addition, the term "polymerizable monomer" refers to a concept that can include not only compounds that do not have a repeating unit, but also compounds that can copolymerize with a (meth)acrylic acid alkyl ester monomer (A), such as the olefin polymer (C) described below, that have a repeating unit themselves.

[0033] ((Meth)acrylic acid alkyl ester monomer (A)) The (meth)acrylic acid alkyl ester monomer (A) is an ester of (meth)acrylic acid and an aliphatic alcohol, and is preferably an alkyl ester derived from an aliphatic alcohol in which the number of carbon atoms in the alkyl group of the aliphatic alcohol is preferably 2 to 14, more preferably 4 to 10. When the number of carbon atoms in the alkyl group is within this range, the adhesive strength is easily increased, and the storage modulus at 23°C of the adhesive, which will be described later, is easily adjusted to a predetermined range.

[0034] Specific examples of the (meth)acrylic acid alkyl ester monomer (A) include ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, and tetradecyl (meth)acrylate. Among these, n-butyl(meth)acrylate, hexyl(meth)acrylate, heptyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, and n-octyl(meth)acrylate are preferred, and n-butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, or a combination thereof is more preferred. Among these, by using at least n-butyl(meth)acrylate, the adhesiveness of the adhesive can be appropriately controlled, and workability when applying the adhesive tape can be improved. The (meth)acrylic acid alkyl ester monomer (A) may be used alone or in combination of two or more.

[0035] The structural unit derived from the (meth)acrylic acid alkyl ester monomer (A) constitutes the main component of the pressure-sensitive adhesive layer, and its content is generally 30% by mass or more, preferably 50% by mass or more, and more preferably 70% by mass or more, based on the total amount of the pressure-sensitive adhesive layer. Increasing the content of the (meth)acrylic acid alkyl ester monomer (A) thus makes it possible to impart a desired adhesive strength to the pressure-sensitive adhesive layer. Furthermore, the content of the structural unit derived from the (meth)acrylic acid alkyl ester monomer (A) is, for example, 97% by mass or less, preferably 95% by mass or less, and more preferably 90% by mass or less, in order to contain a certain amount or more of other components. The content of the structural unit derived from the (meth)acrylic acid alkyl ester monomer (A) in the pressure-sensitive adhesive layer is substantially the same as the content of the (meth)acrylic acid alkyl ester monomer (A) in the pressure-sensitive adhesive composition described below, and can therefore be expressed interchangeably. The same applies to components other than component (A), such as components (B) and (C) described below.

[0036] (Polar Group-Containing Vinyl Monomer (B)) The polymerizable monomer preferably contains a polar group-containing vinyl monomer (B) in addition to the (meth)acrylic acid alkyl ester-based monomer (A). The polar group-containing vinyl monomer (B) has a polar group and a vinyl group. Use of the polar group-containing monomer (B) makes it easier to improve the adhesive strength to the adherend. Examples of the polar group-containing vinyl monomer (B) include carboxylic acid vinyl esters such as vinyl acetate, carboxylic acids containing a vinyl group such as (meth)acrylic acid and itaconic acid, and anhydrides thereof, vinyl monomers having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, caprolactone-modified (meth)acrylate, polyoxyethylene (meth)acrylate, and polyoxypropylene (meth)acrylate, (meth)acrylonitrile, N-vinylpyrrolidone, N-vinylcaprolactam, N-vinyllaurolactam, (meth)acryloylmorpholine, (meth)acrylamide, dimethyl (meth)acrylamide, N-methylol (meth)acrylamide, N-butoxymethyl (meth)acrylamide, diethyl (meth)acrylamide, ethylmethyl (meth)acrylamide, and nitrogen-containing vinyl monomers such as dimethylaminomethyl (meth)acrylate. Among these, vinyl group-containing carboxylic acids such as (meth)acrylic acid and itaconic acid, their anhydrides, and nitrogen-containing vinyl monomers are preferred, (meth)acrylic acid is more preferred, and acrylic acid is even more preferred. These polar group-containing vinyl monomers (B) may be used alone or in combination of two or more.

[0037] When a polar group-containing vinyl monomer (B) is used, the content of the structural units derived from the polar group-containing vinyl monomer (B) in the pressure-sensitive adhesive layer is preferably 1 to 15 parts by mass, more preferably 2 to 12 parts by mass, and even more preferably 3 to 10 parts by mass, per 100 parts by mass of the structural units derived from the (meth)acrylic acid alkyl ester monomer (A). By setting the content of the polar group-containing vinyl monomer (B) within this range, the adhesive strength of the pressure-sensitive adhesive tape can be easily improved.

[0038] (Olefin Polymer (C)) The polymerizable monomer preferably further contains an olefin polymer (C) having a polymerizable bond at one end. Use of such an olefin polymer (C) makes it easier to improve the adhesive strength of the pressure-sensitive adhesive tape. The polymerizable bond means an unsaturated carbon-carbon bond that can be polymerized with the polymerizable monomer, and examples thereof include unsaturated double bonds, and preferably (meth)acryloyl groups. Examples of the olefin polymer (C) include polyolefins having a (meth)acryloyl group at one end. The polyolefins are polymers of aliphatic hydrocarbon compounds having a double bond, such as ethylene, propylene, butane, butadiene, and isoprene, or hydrogenated products thereof.

[0039] Examples of polyolefins having a (meth)acryloyl group at one end include polyethylene having a (meth)acryloyl group at one end, which is prepared by reacting polyethylene having an epoxy group at one end with (meth)acrylic acid. Also included are polybutadiene having a (meth)acryloyl group at one end or hydrogenated products thereof, and examples of commercially available products include "L-1253" manufactured by Kuraray Co., Ltd.

[0040] The olefin polymer (C) preferably has a number average molecular weight of 500 to 20,000, more preferably 1,000 to 10,000. The number average molecular weight may be measured by gel permeation chromatography (GPC) and calculated using a calibration curve of standard polystyrene. The content of the structural units derived from the olefin polymer (C) in the pressure-sensitive adhesive layer is preferably 1 to 30 parts by mass, more preferably 2 to 20 parts by mass, and even more preferably 4 to 15 parts by mass, per 100 parts by mass of the structural units derived from the (meth)acrylic acid alkyl ester monomer (A).

[0041] (Crosslinking Agent (D)) The polymerizable monomer preferably further contains a crosslinking agent. Examples of the crosslinking agent include polyfunctional monomers having two or more vinyl groups, and preferably polyfunctional (meth)acrylates having two or more (meth)acryloyl groups. Use of polyfunctional monomers makes it easier to adjust the adhesive strength of the pressure-sensitive adhesive layer to an appropriate range. Examples of polyfunctional (meth)acrylates include, but are not limited to, hexanediol di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, ethoxylated trimethylolpropane triacrylate, proxied trimethylolpropane triacrylate, proxied glyceryl triacrylate, neopentyl glycol adipate diacrylate, as well as polymers such as polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and liquid hydrogenated 1,2-polybutadiene di(meth)acrylate. Among these polyfunctional (meth)acrylates, polymers are preferred, and liquid hydrogenated 1,2-polybutadiene diacrylate is more preferred. Commercially available liquid hydrogenated 1,2-polybutadiene diacrylates include "TEAI-1000" manufactured by Nippon Soda Co., Ltd. Furthermore, the content of the crosslinking agent-derived structural units in the pressure-sensitive adhesive layer is preferably 0.1 to 4 parts by mass, more preferably 0.3 to 3 parts by mass, and even more preferably 0.5 to 2 parts by mass, per 100 parts by mass of the structural units derived from the (meth)acrylic acid alkyl ester monomer (A). When the content of the crosslinking agent is within the above range, the adhesive strength of the pressure-sensitive adhesive layer can be easily adjusted to an appropriate range.

[0042] (Tackifying Resin) The acrylic adhesive may contain a tackifying resin from the viewpoint of improving adhesive strength. Preferred tackifying resins are those with low polymerization inhibition properties, such as hydrogenated terpene resins, hydrogenated rosins, disproportionated rosin resins, and petroleum resins. Among these, hydrogenated tackifying resins are preferred, since tackifying resins with many double bonds inhibit the polymerization reaction, and hydrogenated petroleum resins are particularly preferred. The softening point of the tackifying resin may be about 95°C or higher from the viewpoint of improving the cohesive strength and adhesive strength of the adhesive, but preferably includes a tackifying resin with a softening point of 120°C or higher. Furthermore, from the viewpoint of improving adhesiveness to an adherend, for example, a tackifying resin with a softening point of 95°C or higher but lower than 120°C and a tackifying resin with a softening point of 120°C or higher but lower than 150°C may be used in combination. The softening point may be measured by the ring and ball method specified in JIS K2207. The content of the tackifier resin in the acrylic pressure-sensitive adhesive is preferably 3 to 40 parts by mass, more preferably 5 to 35 parts by mass, and even more preferably 7 to 25 parts by mass, per 100 parts by mass of the structural units derived from the (meth)acrylic acid alkyl ester monomer (A).

[0043] (Microparticles) The acrylic pressure-sensitive adhesive may contain microparticles. The inclusion of microparticles can improve adhesive strength. Examples of the microparticles include inorganic hollow particles such as glass balloons, shirasu balloons, and fly ash balloons; organic hollow particles made of polymethyl methacrylate, acrylonitrile-vinylidene chloride copolymer, polystyrene, and phenolic resin; inorganic microparticles such as glass beads, silica beads, and synthetic mica; and organic microparticles such as polyethyl acrylate, polyurethane, polyethylene, and polypropylene. The content of the microparticles in the acrylic pressure-sensitive adhesive is preferably 0.1 to 15 parts by mass, more preferably 0.3 to 10 parts by mass, and even more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the structural units derived from the (meth)acrylic acid alkyl ester monomer (A).

[0044] (Other Components) In addition to the components described above, the acrylic pressure-sensitive adhesive used in the pressure-sensitive adhesive layer may contain various additives conventionally used in pressure-sensitive adhesives, such as a plasticizer, a softener, a pigment, a dye, a dispersant, a photopolymerization initiator, and a flame retardant.

[0045] However, the components that can be used in the acrylic pressure-sensitive adhesive are not limited to those mentioned above, and other components may be used. For example, a crosslinking agent (D) other than those mentioned above may be used, and a crosslinking agent other than those mentioned above that can be used in acrylic pressure-sensitive adhesives, such as an isocyanate-based crosslinking agent, may be used instead of the polymerizable monomer. In addition, the olefin polymer (C), fine particles, etc. may not be used.

[0046] (Rubber-Based Pressure-Sensitive Adhesive) The rubber-based pressure-sensitive adhesive contains a rubber component and a tackifying resin, and it is preferable to use a styrene-isoprene block copolymer as the rubber component. The styrene-isoprene block copolymer preferably has a diblock ratio of 25 to 70% by mass, more preferably 30 to 65% by mass, and even more preferably 45 to 60% by weight. Here, "diblock" refers to a diblock composed of styrene and isoprene. By setting the diblock ratio within the above range, it becomes easier to increase adhesive strength. In addition to diblocks, styrene-isoprene block copolymers also include those having three or more blocks, such as triblocks composed of styrene, isoprene, and styrene blocks.

[0047] The amount of styrene in the styrene-isoprene block copolymer is not particularly limited, but is preferably 14 to 24% by mass, more preferably 15 to 18% by mass. If the styrene amount is 14% by mass or more, the resulting adhesive tends to have high cohesive strength. Furthermore, if the styrene amount is 24% by mass or less, the cohesive strength becomes moderate and adhesive strength is easily exerted. The molecular weight of the styrene-isoprene block copolymer is not particularly limited, but is preferably 100,000 to 400,000 in mass average molecular weight, more preferably 150,000 to 250,000. The mass average molecular weight referred to here refers to the molecular weight measured as polystyrene equivalent by GPC (gel permeation chromatography) method.

[0048] Various tackifying resins can be used in rubber-based pressure-sensitive adhesives, but petroleum-based resins, terpene resins, and coumarone resins are preferred. Tackifying resins may be used alone or in combination. However, it is preferable to use a petroleum-based resin in combination with at least one selected from terpene resins and coumarone resins. This combination of tackifying resins facilitates improved adhesive strength. Examples of petroleum-based resins include aliphatic petroleum resins (C5 petroleum resins), alicyclic petroleum resins, and aromatic petroleum resins. From the perspective of compatibility with styrene-isoprene block copolymers, aliphatic petroleum resins are preferred. Furthermore, it is preferable to use petroleum-based resins with a softening point of approximately 90 to 120°C. Furthermore, terpene resins with a softening point of approximately 80 to 120°C can be used, but those below 100°C are preferred from the perspective of ensuring adhesive strength. Furthermore, to ensure cohesive strength, coumarone resins with a softening point of preferably 110 to 130°C, more preferably 115 to 125°C, are used.

[0049] The amount of the tackifier resin is preferably 60 to 250 parts by mass, more preferably 100 to 200 parts by mass, and even more preferably 110 to 180 parts by mass, per 100 parts by mass of the rubber component. By setting the blending amount of the tackifier resin within the above range, it is possible to improve the cohesive strength and impart appropriate adhesive strength. Furthermore, when a petroleum-based resin is used in combination with at least one selected from a terpene resin and a coumarone resin, the amount of the petroleum-based resin is preferably 50 to 200 parts by mass, more preferably 60 to 150 parts by mass, and more preferably 60 to 110 parts by mass, per 100 parts by mass of the rubber component. Meanwhile, the amount of the terpene resin is preferably 10 to 70 parts by mass, more preferably 20 to 60 parts by mass, and even more preferably 30 to 50 parts by mass, per 100 parts by mass of the rubber component. Furthermore, the amount of the coumarone resin is preferably 10 to 60 parts by mass, more preferably 15 to 50 parts by mass, and even more preferably 20 to 40 parts by mass, per 100 parts by mass of the rubber component. The rubber-based adhesive may contain the above-mentioned fine particles, similar to the acrylic-based adhesive, and may also contain, as necessary, a sacrificial anticorrosive metal, a conductive material, a softener, an antioxidant, a filler, etc.

[0050] (Urethane-Based Pressure-Sensitive Adhesive) The urethane-based pressure-sensitive adhesive is not particularly limited, and examples thereof include urethane resins obtained by reacting at least a polyol with a polyisocyanate compound. Examples of the polyol include polyether polyols, polyester polyols, polycarbonate polyols, and polycaprolactone polyols. Examples of the polyisocyanate compounds include diphenylmethane diisocyanate, tolylene diisocyanate, and hexamethylene diisocyanate. These urethane-based pressure-sensitive adhesives may be used alone or in combination of two or more. Furthermore, examples of the urethane-based pressure-sensitive adhesive include urethane resins obtained by reacting a polyurethane polyol with a polyfunctional isocyanate curing agent. Examples of polyurethane polyols include those obtained by reacting the above-mentioned polyols with a polyisocyanate compound, or those obtained by reacting a polyol, a polyisocyanate compound, and a chain extender such as a diamine. The polyfunctional isocyanate curing agent may be any compound having two or more isocyanate groups, and the above-mentioned isocyanate compounds can be used. The urethane-based adhesive may contain the above-mentioned fine particles in addition to the urethane resin, and may also contain a tackifying resin, a sacrificial anticorrosive metal, a conductive material, a softener, an antioxidant, a filler, etc., as necessary.

[0051] (Silicone-based adhesive) Examples of silicone-based adhesives include addition reaction type, peroxide curing type, and condensation reaction type silicone-based adhesives. Among them, addition reaction type silicone-based adhesives are preferably used from the viewpoint of being curable at low temperature in a short time. Note that addition reaction type silicone-based adhesives are cured when the adhesive layer is formed. When an addition reaction type silicone-based adhesive is used as the silicone-based adhesive, the silicone-based adhesive may contain a catalyst such as a platinum catalyst. Furthermore, the silicone-based adhesive may contain fine particles, and a crosslinking agent and various additives for controlling adhesive strength may be added.

[0052] (Metal with a lower potential than iron) The pressure-sensitive adhesive layer preferably contains a metal with a lower potential than iron. By containing a metal with a lower potential than iron (hereinafter also referred to as "sacrificial corrosion protection metal"), sacrificial corrosion protection against iron is imparted, thereby improving the corrosion protection of the pressure-sensitive adhesive tape. The sacrificial corrosion protection metal is dispersed in the pressure-sensitive adhesive that constitutes the pressure-sensitive adhesive layer.

[0053] Examples of sacrificial corrosion protection metals include cadmium, chromium, zinc, manganese, and aluminum. Of these, zinc and aluminum are preferred, with zinc being particularly preferred. The use of zinc provides excellent sacrificial corrosion protection.

[0054] The sacrificial corrosion protection metal may be dispersed in the pressure-sensitive adhesive as a filler in any form, such as a particle shape, a scale shape, or a spindle shape, but a particle shape is preferred. By forming the sacrificial corrosion protection metal into a particle shape, it is easily dispersed in the pressure-sensitive adhesive layer without substantially reducing the adhesiveness of the pressure-sensitive adhesive layer. In this specification, a particle shape refers to a particle having a small aspect ratio (the ratio of the major axis length to the minor axis length), for example, an aspect ratio of 3 or less, preferably 2 or less. The particle shape is not particularly limited, but may be spherical or amorphous, such as a powder. The particle size of the above-mentioned particulate metal is, for example, 1 to 500 μm, preferably 1 to 200 μm. In this specification, particle size refers to the average particle size measured by laser diffraction / scattering.

[0055] When the pressure-sensitive adhesive layer contains a sacrificial metal, the content of the sacrificial metal in the pressure-sensitive adhesive layer is, for example, 0.5 to 30 mass%, preferably 1 to 20 mass%, and more preferably 2 to 15 mass%, based on the total amount of the pressure-sensitive adhesive layer. When the content of the sacrificial metal is equal to or greater than these lower limits, the sacrificial corrosion protection is enhanced, thereby improving corrosion prevention performance. When the content is equal to or less than these upper limits, the adhesive strength is increased, and the transparency of the pressure-sensitive adhesive tape can be further ensured.

[0056] It is also preferable that the pressure-sensitive adhesive layer does not contain a sacrificial anticorrosive metal. When the pressure-sensitive adhesive layer does not contain a sacrificial anticorrosive metal, the adhesive strength of the pressure-sensitive adhesive tape is maintained high compared to when the pressure-sensitive adhesive layer contains a sacrificial anticorrosive metal, making the pressure-sensitive adhesive tape less likely to peel from the adherend, thereby blocking water and oxygen and improving corrosion prevention. In addition, the transparency of the pressure-sensitive adhesive tape can be ensured.

[0057] (Conductive Material) The pressure-sensitive adhesive layer may contain a conductive material other than the sacrificial protection metal. When the pressure-sensitive adhesive layer contains a sacrificial protection metal, it preferably contains a conductive material. The inclusion of a conductive material facilitates the transfer of electrons released when the sacrificial protection metal is ionized to the adherend, thereby improving sacrificial protection. Examples of conductive materials include one or more selected from carbon-based materials, metal-based materials, metal oxide-based materials, ionic polymers, and conductive polymers. Examples of carbon-based materials include carbon black, graphite, graphene, carbon nanotubes, acetylene black, etc. Examples of metal-based materials include metals with a more noble potential than iron, such as gold, silver, copper, nickel, or alloys containing these, or iron. Examples of metal oxide-based materials include indium tin oxide (ITO), antimony trioxide (ATO), fluorine-doped tin oxide (FTO), zinc oxide, etc. Examples of conductive polymers include polyacetylene, polypyrrole, PEDOT (polyethylenedioxythiophene), PEDOT / PSS (a composite of polyethylenedioxythiophene and polystyrene sulfonic acid), polythiophene, polyaniline, poly(p-phenylene), polyfluorene, polycarbazole, polysilane, and derivatives thereof. Examples of ionic polymers include sodium polyacrylate and potassium polyacrylate. These conductive materials may be used alone or in combination of two or more. Among the above, carbon-based materials are preferred as the conductive material, and carbon nanotubes are more preferred.

[0058] (Carbon nanotubes) As described above, the pressure-sensitive adhesive layer preferably contains carbon nanotubes as a conductive material. By containing carbon nanotubes, the sacrificial corrosion protection of the pressure-sensitive adhesive layer is improved and high adhesive strength and transparency can be maintained, making it easier to obtain a pressure-sensitive adhesive tape that combines high adhesive strength, sacrificial corrosion protection, and high transparency. This is presumably because, although carbon nanotubes are a conductive material, a smaller amount is required to exhibit a certain level of sacrificial corrosion protection compared to other types of conductive materials, so the degree of decrease in adhesive strength is smaller.

[0059] Carbon nanotubes are tubular materials formed from carbon. Carbon nanotubes have excellent electrical properties, and when combined with resins or other materials, they can be used to form highly conductive sheets. Carbon nanotubes are substances with a cylindrical structure in which graphite sheets with a hexagonal mesh-like carbon atom arrangement are wound. Those wound in one layer are called single-wall carbon nanotubes, and those wound in multiple layers are called multi-wall carbon nanotubes. The type of carbon nanotube is not particularly limited, and may be any of single-wall carbon nanotubes, multi-wall carbon nanotubes, or mixtures containing these in any ratio. Carbon nanotubes manufactured by various methods, such as arc discharge, laser evaporation, and chemical vapor deposition (CVD), can also be used.

[0060] The average diameter of the carbon nanotubes is preferably 1 to 100 nm, more preferably 2 to 15 nm. The average length of the carbon nanotubes is preferably 0.1 to 1,000 μm, more preferably 10 to 500 μm. The aspect ratio (average length / average diameter) of the carbon nanotubes is preferably 10 to 100,000, more preferably 500 to 30,000. Note that the diameter of the carbon nanotubes refers to the outer diameter in the case of single-walled carbon nanotubes, and the outer diameter of the outermost tube in the case of multi-walled carbon nanotubes. The diameter and length of the carbon nanotubes can be measured, for example, in images obtained by observation with a transmission electron microscope (TEM), and the average diameter and average length can be determined by the arithmetic average of any 50 nanotubes.

[0061] From the viewpoints of the sacrificial corrosion protection and adhesive strength of the adhesive layer, and the transparency of the adhesive tape, the content of the conductive material in the adhesive layer is preferably 0.001 to 10 mass%, more preferably 0.002 to 5 mass%, and even more preferably 0.003 to 3 mass%, based on the total amount of the adhesive layer.

[0062] When the conductive material is carbon nanotubes, the content of the carbon nanotubes in the pressure-sensitive adhesive layer is preferably 0.0005 to 0.7 mass%, more preferably 0.002 to 0.05 mass%, and even more preferably 0.003 to 0.045 mass%, based on the total amount of the pressure-sensitive adhesive layer. When the content of carbon nanotubes is equal to or greater than these lower limits, sacrificial corrosion protection is likely to be enhanced. On the other hand, when the content of carbon nanotubes is equal to or less than these upper limits, adhesive strength is likely to be improved, and transparency of the pressure-sensitive adhesive tape can be ensured.

[0063] (Method for Producing Acrylic Pressure-Sensitive Adhesive and Pressure-Sensitive Adhesive Layer) The pressure-sensitive adhesive layer can be produced by a general pressure-sensitive adhesive layer formation method. Hereinafter, the method for producing an acrylic pressure-sensitive adhesive and a pressure-sensitive adhesive layer will be described in detail, taking as an example a case where the pressure-sensitive adhesive is an acrylic pressure-sensitive adhesive and a photocurable type. The acrylic pressure-sensitive adhesive can be obtained by irradiating a pressure-sensitive adhesive composition containing the above-mentioned polymerizable monomer, and optionally a sacrificial corrosion protection metal and a conductive material, with light to polymerize the polymerizable monomer. The pressure-sensitive adhesive composition may also contain at least one of the above-mentioned tackifier resin, microparticles, and other components. More specifically, the polymerizable monomer, optionally a sacrificial corrosion protection metal and a conductive material, and optionally a tackifier resin, microparticles, and other components are first introduced into a reaction vessel such as a glass vessel and mixed to obtain a pressure-sensitive adhesive composition. Next, to remove dissolved oxygen from the pressure-sensitive adhesive composition, an inert gas such as nitrogen gas is generally supplied to purge the oxygen. The pressure-sensitive adhesive composition is then applied to a release sheet or a substrate, and then irradiated with light to polymerize the polymerizable monomer, thereby obtaining a pressure-sensitive adhesive layer. The steps from application or impregnation of the pressure-sensitive adhesive composition to the step of irradiating with light are preferably carried out in an inert gas atmosphere or in a state where oxygen is blocked by a film, etc. In the present production method, the pressure-sensitive adhesive composition obtained by mixing the components may be pre-polymerized before being applied to a release sheet, a support, or the like in order to increase the viscosity.

[0064] (Storage Modulus) The pressure-sensitive adhesive layer preferably has a storage modulus of 50,000 to 1,000,000 Pa at 23°C. When the storage modulus at 23°C is within the above range, when the pressure-sensitive adhesive layer is damaged by external impact or the like, the force to restore the damaged area (hereinafter also referred to as self-repairing ability) is strong. As a result, corrosion prevention performance is improved, and when used on steel materials, for example, rust generation is more easily suppressed. From the viewpoint of increasing the self-repairing ability and improving corrosion prevention performance, the storage modulus of the pressure-sensitive adhesive layer at 23°C is more preferably 200,000 to 800,000 Pa, and even more preferably 300,000 to 600,000 Pa. The storage modulus can be calculated by measuring a dynamic viscoelasticity spectrum.

[0065] As described below, when a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer are provided, the pressure-sensitive adhesive layer on the surface side, i.e., the second pressure-sensitive adhesive layer, may have the configuration of the pressure-sensitive adhesive layer described above. On the other hand, the configuration of the first pressure-sensitive adhesive layer is not particularly limited, and it may be formed from a known pressure-sensitive adhesive, such as an acrylic pressure-sensitive adhesive, a rubber pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, or a silicone pressure-sensitive adhesive, with acrylic pressure-sensitive adhesives being preferred. Details of the pressure-sensitive adhesive in the first pressure-sensitive adhesive layer are as described above, and therefore will not be described in detail here.

[0066] (Thickness) The thickness of the pressure-sensitive adhesive layer is preferably 50 to 2500 μm, more preferably 60 to 2200 μm, and even more preferably 80 to 1500 μm. By making the thickness equal to or greater than the above-mentioned lower limit, the self-repairing ability and other properties can be enhanced, improving the corrosion resistance of the pressure-sensitive adhesive tape, and the adhesive strength can also be easily increased. Furthermore, by making the thickness of the pressure-sensitive adhesive layer equal to or less than the above-mentioned upper limit, the corrosion resistance can be improved according to the thickness, and the transparency of the pressure-sensitive adhesive tape can be improved.

[0067] As described below, when a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer are provided, the thickness of the first pressure-sensitive adhesive layer is preferably 5 to 100 μm, more preferably 10 to 50 μm, and even more preferably 30 to 50 μm. The thickness of the second pressure-sensitive adhesive layer is also in the same range as the thickness of the first pressure-sensitive adhesive layer described above. The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may have the same thickness or different thicknesses.

[0068] <Intermediate Layer> The pressure-sensitive adhesive tape of the present invention may have an intermediate layer between the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer. Examples of the intermediate layer include sheet-like materials such as foams, resin films, and nonwoven fabrics. Examples of foams include polyolefin resin foams such as polyethylene foams, modified polyethylene foams, and polypropylene foams, polystyrene foams, styrene-acrylonitrile copolymer foams, polyvinyl chloride foams, polyvinyl alcohol foams, cellulose-based foams, polyamide foams, polyurethane foams, phenolic resin foams, urea resin foams, epoxy resin foams, acrylic resin foams, silicone resin foams, pyranyl resin foams, and polyimide foams. Examples of resin films include polyolefin-based resin films such as polypropylene-based resin films, polyethylene-based resin films, and ethylene-vinyl acetate copolymer (EVA)-based resin films, polyester-based resin films, polyamide-based resin films, acrylic-based resin films, polyurethane-based resin films, polystyrene-based resin films, polyvinyl chloride-based resin films, ethylene vinyl acetate-based resin films, acrylonitrile-based resin films, fluorine-based films, polycarbonate-based films, AES resin-based films, and ASA resin-based films. Nonwoven fabrics include nonwoven fabrics made of synthetic resin fibers such as polyamide-based, polyester-based, polyacrylic-based, polyolefin-based, and polyurethane-based. These sheet-like materials can be used alone or in combination of two or more. From the viewpoint of protecting the adherend from impact, the substrate is preferably a foam, with polyolefin resin foam and acrylic resin foam being more preferred. The thickness of the intermediate layer is not particularly limited, but is preferably 100 to 3,000 μm, more preferably 500 to 2,000 μm, and even more preferably 800 to 1,500 μm. When the thickness of the substrate is equal to or greater than these lower limits, the substrate can function as a support and can adequately protect the adherend from impact, while when the thickness of the substrate is equal to or less than these upper limits, the workability is improved and the tape can be easily handled.

[0069] <Configuration of Adhesive Tape> As shown in Fig. 1 , the adhesive tape of the present invention is preferably a single-sided adhesive tape in which the adhesive tape 10 comprises a substrate 12 and an adhesive layer 11 provided on one side of the substrate 12. This allows the adhesive layer 11 to be protected by the substrate 12. The adhesive tape is used by being attached to an adherend with the surface 11A of the adhesive layer 11 as the adhesive surface.

[0070] 2, the pressure-sensitive adhesive tape of the present invention may be a single-sided pressure-sensitive adhesive tape in which the pressure-sensitive adhesive tape 10 includes a substrate 12, and a first pressure-sensitive adhesive layer 11B, an intermediate layer 13, and a second pressure-sensitive adhesive layer 11C provided on one side of the substrate 12. Although not shown, the pressure-sensitive adhesive tape may also be a double-sided pressure-sensitive adhesive tape in which a substrate and pressure-sensitive adhesive layers are provided on both sides of the substrate.

[0071] The pressure-sensitive adhesive tape of the present invention may have a release sheet attached to the surface of the pressure-sensitive adhesive layer. The release sheet is preferably peeled from the pressure-sensitive adhesive layer before use to expose the pressure-sensitive adhesive layer, and the exposed pressure-sensitive adhesive layer is then attached to the adherend. More specifically, the release sheet is preferably attached to the surface of the pressure-sensitive adhesive layer opposite the surface on which the substrate is provided, i.e., surface 11A. A resin film may be used as the release sheet, and the surface to be attached to the pressure-sensitive adhesive layer is preferably a release-treated surface that has been subjected to a release treatment using a silicone release agent or the like. When a release sheet is attached, the various physical properties of the pressure-sensitive adhesive tape, such as total light transmittance, tensile elongation at break, and tensile load difference, are measured after the release sheet is removed.

[0072] <Uses and Methods of Use> The pressure-sensitive adhesive tape of the present invention is preferably applied to the surface of a concrete structure or the surface of a structure having rust. The pressure-sensitive adhesive tape of the present invention has excellent conformability and transparency, as well as excellent weather resistance. Because the pressure-sensitive adhesive tape of the present invention has the above properties, it is particularly suitable for long-term use on concrete structures installed outdoors or structures having rust. The pressure-sensitive adhesive tape of the present invention is also preferably used for corrosion prevention to prevent corrosion of metal materials, etc. The pressure-sensitive adhesive tape of the present invention may also be applied to the surface of a metal material having rust other than a structure. More specifically, by applying the tape to a corroded or damaged area of ​​the above-mentioned structure, the pressure-sensitive adhesive tape of the present invention can suppress the progression of corrosion or damage, or corrosion of the structure or metal material from the damaged area. Furthermore, because the pressure-sensitive adhesive tape of the present invention has excellent transparency, it is possible to visually check the progression of corrosion or damage at the corroded or damaged area and the conformability of the tape to the corroded or damaged area from the tape even after application. Therefore, it is possible to take appropriate preventative maintenance measures, such as checking the corrosion or damage status of the area where the tape is applied and taking repair measures depending on the progress of the corrosion or damage.

[0073] Examples of concrete structures include viaducts, tunnels, levees, buildings, mooring facilities in ports, utility poles, dams, and the like. Concrete structures may also have metal materials such as steel installed inside. Damage to concrete structures, such as cracks, can lead to water penetration through the damaged areas, corroding the steel materials inside. Applying the adhesive tape of the present invention to the damaged areas can prevent water penetration and corrosion of the steel materials inside. Furthermore, the structure or metal material having rusted portions is not particularly limited as long as it has rusted portions. Examples include structures made of various metal materials, such as railway bridges, tanks, plants, machinery and equipment in factories, signs, road signs, guardrails, containers, power transmission facilities, water pipes, and ships, as well as metal materials other than structures. The metal material is preferably a metal material containing at least one selected from the group consisting of iron and iron-containing alloys. Specific examples of alloys containing iron include alloy steels such as nickel-chromium steel, nickel-chromium-molybdenum steel, chromium steel, chromium-molybdenum steel, and manganese steel, as well as various steel materials such as carbon steel. For structures with rusted areas, the adhesive tape may be applied to the rusted surface of the structure. Rust refers to the corroded portion of a metal, and includes not only red rust or brown rust caused by iron or the like, but also various types of rust such as blue rust, black rust, and white rust.

[0074] The pressure-sensitive adhesive tape of the present invention may be applied after a rust progression inhibitor or primer is applied to the application surface. The rust progression inhibitor that can be used in the present invention is not particularly limited, but examples include those having an adsorption effect that adsorbs moisture and salt, which are rust-causing substances, and rust converters that convert red rust to black rust. Applying these rust progression inhibitors to the application surface of the tape when applying it to a rusted structure makes it easier to enhance the corrosion progression prevention effect. On the other hand, it is preferable to use a primer that has alkali-resistant properties. Applying an alkali-resistant primer to the application surface of the tape before applying it to a concrete structure makes it easier to enhance the corrosion progression prevention effect. Both the rust progression inhibitor and the primer can be known, and those that are transparent are preferred in order to allow the application surface to be visible.

[0075] The pressure-sensitive adhesive tape of the present invention may be applied to adherends other than the surfaces of concrete structures and structures having rusted portions. For example, it may be applied to the surface of metal structures or metal materials other than metal structures, regardless of the presence or absence of rusted portions, such as metal structures without rusted portions. The metal structure is not particularly limited, and examples include structures made of the various metal materials described above. Among these, steel structures are preferred. Metal materials other than metal structures are also as described above. It is preferable that the metal material is used in civil engineering components or buildings. As both the metal structure and the metal material have been described above, detailed description thereof will be omitted.

[0076] Furthermore, mortar and concrete other than concrete structures may also be used as the adherend. Specifically, the pressure-sensitive adhesive tape of the present invention may be used, for example, to protect the foundation adjustment portion of a manhole. In this case, the pressure-sensitive adhesive tape may be attached to the mortar surface that constitutes the foundation adjustment portion, the concrete surface that constitutes the lower manhole, or the like. Using the pressure-sensitive adhesive tape for this purpose can prevent the foundation adjustment portion of the manhole from being deteriorated by hydrogen sulfide generated inside the manhole or sulfuric acid generated when hydrogen sulfide condenses inside the manhole.

[0077] Furthermore, the pressure-sensitive adhesive tape of the present invention may be attached to various underwater materials used underwater, such as structures on or underwater, or concrete, mortar, and metal materials other than structures. The underwater materials are not particularly limited, and specific examples include underwater materials used underwater, such as wharves, quays, piers, wave-breaking blocks, and fishing nets, as well as floating materials used on the sea, such as ships and floats. The pressure-sensitive adhesive tape may also be attached to underwater devices, such as sensors, used on or underwater. The adherend on or underwater may be used, for example, to prevent the attachment of aquatic organisms, such as barnacles. Of course, the location where the pressure-sensitive adhesive tape of the present invention is used is not limited to the sea, and it may also be used in rivers, lakes, and other ponds. When using the pressure-sensitive adhesive tape, it is recommended that it be attached to at least the portion that comes into contact with water, particularly seawater.

[0078] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0079] [Evaluation Method] In the examples and comparative examples, the pressure-sensitive adhesive tapes were evaluated by the following evaluation methods.

[0080] <Difference in Tensile Load of Substrate> The difference in tensile load of the substrate was measured by the same measurement method as the difference in tensile load of the adhesive tape described below, except that the substrate film used in each of the Examples and Comparative Examples was used as the measurement sample.

[0081] <Ultraviolet transmittance> The substrate film used in each of the examples and comparative examples was set in a spectrophotometer (product name "V-750", manufactured by JASCO Corporation) to measure the ultraviolet transmittance. During the measurement, the spectrophotometer was set under the following conditions. (Spectrophotometer conditions) The wavelength of ultraviolet light emitted from the light source was set to 300 to 750 nm, the data acquisition interval was set to 0.5 nm, and the scanning speed was set to 1,000 nm / min, so that the ultraviolet transmittance at 340 nm was read.

[0082] <Color Difference (ΔE) After Accelerated Weathering Test> The color difference (ΔE) of the substrate films used in each of the Examples and Comparative Examples was measured using a color difference meter (product name "CR-400", manufactured by Konica Minolta, Inc.). ＊ a ＊ b ＊ The color difference (ΔE) was calculated using the color coordinates in the L color space (see JIS K 5600 4-4) according to the following formula: ＊ 促進後 , a ＊ 促進後 , and b ＊ 促進後 Regarding the L of the base film after 500 hours of accelerated weather resistance testing in accordance with Cycle A in JIS K5600-7-7, ＊ , a ＊ , b ＊ was measured. ＊ 初期 , a ＊ 初期 , and b ＊ 初期Regarding the L of the base film before the accelerated weather resistance test, ＊ , a ＊ , b ＊ The accelerated weather resistance test was carried out by attaching and fixing the four sides of the substrate film to a SUS plate with masking tape or the like. The color difference of the substrate film was measured with the substrate film placed on the SUS plate. ΔE ＊ ａｂ = [(ΔL ＊ ) ２ + (Δa ＊ ) ２ + (Δb ＊ ) ２ ] １／２ ΔL ＊ =L ＊ 初期 -L ＊ 促進後 Δa ＊ = a ＊ 初期 -a ＊ 促進後 Δb ＊ = b ＊ 初期 -b ＊ 促進後

[0083] <Elmendorf tear strength> Measurement was performed in the same manner as the Elmendorf tear method in accordance with JIS K7128-2 (1998), except that the measurement was performed without slitting the sample. Measurement was performed in both MD and TD, and the smaller value was taken as the Elmendorf tear strength (N) of the substrate.

[0084] <Dimensional Change Rate> 1. Preparation of Samples The films used in each of the Examples and Comparative Examples were cut into 60 mm square samples. The diagonal length of the cut samples was measured. This diagonal length was designated as Diagonal A. 2. Calculation of Dimensional Change Rate The samples obtained in 1 above were immersed in xylene for 5 minutes. The diagonal length of the sample after immersion was measured. This diagonal length was designated as Diagonal B. The dimensional change rate of the substrate of the tape was calculated from the two diagonal lengths obtained in this manner. The formula for calculating the dimensional change rate was as follows: Dimensional change rate (%) = (Diagonal B - Diagonal A) / Diagonal A x 100

[0085] <Gloss Retention Rate> The pressure-sensitive adhesive tape (width 25 mm, length 100 mm) obtained in each Example and Comparative Example was attached, and the surface of the tape was irradiated from the substrate side using a handheld gloss meter (manufactured by Horiba, Ltd., product name: "IG-340") to measure the gloss of the substrate. The gloss was measured using a handheld gloss meter with a 60° geometrical condition in accordance with JIS K 5600-4-7. The gloss obtained in this measurement was designated Gloss A. Thereafter, the tape was attached to the entire surface of a steel plate SS400 (manufactured by TP Giken Co., Ltd., 150 mm x 70 mm), and an accelerated weathering test in accordance with Cycle A of JIS K 5600-7-7 was performed for 500 hours. After the accelerated weathering test, the haze of the substrate of the tape was measured using the same method as that performed before the test. The gloss obtained by the measurement after the test was designated Gloss B. The gloss retention rate of the tape was calculated from the two types of haze obtained as described above. The formula for calculating the gloss retention is as follows: Gloss retention (%) = (Gloss B / Gloss A) x 100

[0086] <Storage Modulus at 23°C> The storage modulus at 23°C of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape obtained in each of the Examples and Comparative Examples was calculated by measuring the dynamic viscoelasticity spectrum using a dynamic viscoelasticity measuring device (manufactured by IT Measurement & Control Co., Ltd., product name "DVA-200") under the conditions of shear mode: 10 Hz, strain amount: 0.1%, temperature range: -100°C to 100°C, and heating rate: 10°C / min.

[0087] <Adhesive Strength> 1. Sample Preparation The adhesive tapes obtained in each Example and Comparative Example were cut to a width of 25 mm and a length of 100 mm, and then bonded to a SUS plate (width 50 mm, length 125 mm) via the adhesive layer to prepare a measurement sample. Bonding to the SUS plate was performed by using a 2 kg roller, moving back and forth twice at a speed of 10±0.5 mm / s. Using the measurement samples prepared by the above method, an accelerated weathering test was performed based on Cycle A of JIS K5600-7-7. The test was performed for 500 hours. The adhesive strength of the measurement samples after the accelerated weathering test was then measured. 2. Measurement Method A peel test was performed as follows to measure adhesive strength using the measurement samples before and after the test. Each measurement sample was fixed in the chuck of a tensile tester ("Tensilon Universal Material Tester" manufactured by A&D Co., Ltd.). Thereafter, in an environment of 23°C and 50% RH, the adhesive tape was pulled for 60 mm or more at a peel angle of 90° and a speed of 300 mm / min, and the average value of the load (N) detected by the load cell was recorded and used as the adhesive strength.

[0088] <Total Light Transmittance (Initial, After Accelerated Weathering Test)> The pressure-sensitive adhesive tapes obtained in each Example and Comparative Example were processed into a width of 50 mm and a length of 30 mm to prepare measurement samples, and the total light transmittance (initial total light transmittance) was measured. Furthermore, using measurement samples separately prepared in the same manner, an accelerated weathering test was performed based on cycle A of JIS K5600-7-7. The test was performed for 500 hours. Then, the total light transmittance (total light transmittance after the test) of the measurement samples after the accelerated weathering test was measured. The total light transmittance was measured in accordance with JIS K7361-1. Specifically, the measurement was performed using a haze meter (Haze Meter NDH4000 manufactured by Nippon Denshoku Industries Co., Ltd.) in an atmosphere of 23°C and 50% humidity.

[0089] <Difference in tensile load of adhesive tape> Using the adhesive tapes obtained in each Example and Comparative Example as measurement samples, a tensile tester was used to measure the tensile load when pulled by 2.5% and the tensile load when pulled by 0.5%, and the difference between the two was calculated. Note that all of the measurements were carried out in both the MD direction and the TD direction, and the difference between the tensile load when the adhesive tape was pulled by 2.5% and the tensile load when the adhesive tape was pulled by 0.5% was calculated for each direction. The larger of the calculated differences in tensile load between the MD direction and the TD direction was taken as the difference in tensile load.

[0090] <Tensile elongation at break> The pressure-sensitive adhesive tapes obtained in each of the Examples and Comparative Examples were subjected to tensile tests in both the MD and TD directions using a tensile tester ("Tensilon Universal Material Tester" manufactured by A&D Co., Ltd.), and the tensile elongation at break was calculated using the following formula: Tensile elongation at break (%) = (L - L ０ ) / L ０ × 100 where L is the length of the sample at break, L ０ is the length of the sample before the tensile test. The measured value of either the substrate or the adhesive layer, whichever broke first, was used as the tensile elongation at break. Of the tensile elongations at break in the MD and TD directions used, the smaller value was used as the tensile elongation at break of the adhesive tape. The conditions for measuring the tensile load and the tensile elongation at break were as follows. All of the tensile tests were carried out in an environment of 23°C and 50% RH. Dimensions and shape of substrate: strip with width 24 mm x length 80 mm Distance between chucks: 50 mm Tensile speed: 300 mm / min

[0091] <Rust Generation> The pressure-sensitive adhesive tapes obtained in each of the Examples and Comparative Examples were attached to grit-blasted steel plates (150 x 70 x 3.2 mm) with a surface preparation level of ISO 8501-1 Sa2.5, and an accelerated weather resistance test was carried out based on cycle A of JIS K5600-7-7. Thereafter, the occurrence of rust was evaluated by visually checking whether or not rust had occurred at the location where the pressure-sensitive adhesive tape was attached. The test was carried out for 500 hours. The evaluation criteria for rust generation are as follows: None: No visible rust occurred. Present: Visible rust occurred.

[0092] <Substrate Confirmation> An X mark was drawn with a marker on the adhesive layer of the pressure-sensitive adhesive tape obtained in each Example and Comparative Example, and the pressure-sensitive adhesive tape was then attached to a grit-blasted steel plate (150 × 70 × 3.2 mm) conforming to ISO 8501-1 Sa2.5, and an accelerated weather resistance test based on Cycle A of JIS K5600-7-7 was performed. After the test, the pressure-sensitive adhesive tape was visually inspected from the substrate side to evaluate the substrate confirmation. Note that before the test, the X mark was completely visible from the substrate side. The test was performed for 500 hours. The evaluation criteria for the substrate confirmation are as follows: ◯: After the accelerated weather resistance test, the X mark was visible. ×: After the accelerated weather resistance test, the X mark was at least either not visible or the evaluation result for rust occurrence was "present".

[0093] <Overall evaluation of weather resistance> After conducting an accelerated weather resistance test based on Cycle A of JIS K5600-7-7, an overall evaluation of weather resistance was made based on the occurrence of rust at the adhesive tape affixed portion and the evaluation results of the substrate inspection. The evaluation criteria are as follows: ∘: No visible rust occurred, and the substrate inspection result was "∘". ×: Visible rust occurred, or the substrate inspection result was "×".

[0094] <Practical Evaluation of Convex Part Conformability> The conformability was evaluated according to the procedures set forth in 1. to 4. below. 1. As shown in FIG. 3 , an adhesive tape 10 before undergoing an accelerated weathering test in accordance with Cycle A of JIS K 5600-7-7 was attached to the adherend surface 20A of an L-shaped SUS plate 20 so that the height h and width t of the lifted portion were 2 mm. 2. A squeegee was pressed against the portion of the adhesive tape 10 that was not adhered to the L-shaped SUS plate 20. 3. After pressing in 2. above, the height h of the lifted portion was measured, and the adhesive tape 10 was visually inspected for the presence or absence of tearing. 4. Based on the measured value of the height h obtained in 3. above, the conformability of the adhesive tape 10 was evaluated according to the following criteria. ⊚: The height h was 0 mm, and no tearing occurred in the adhesive tape 10. ◯: A tear occurred in the adhesive tape 10, but the height h was less than 2 mm. Alternatively, the height h was 2 mm, but no tearing occurred in the adhesive tape 10, and a certain degree of conformability was observed. ×: The height h was 2 mm, and tearing occurred in the adhesive tape 10, and the tape did not conform to the SUS plate at all.

[0095] <Practical Evaluation of Peeling> A pressure-sensitive adhesive tape (25 mm wide, 100 mm long) from each Example and Comparative Example was attached to a stainless steel plate (50 mm wide, 125 mm long) and cured at 23°C for 3 days to prepare a sample for peeling evaluation. Water was sprayed for 5 minutes at a water pressure of 8 MPa toward the side of the longitudinal end of the adhesive tape from a spray position diagonally above the adhesive tape in the peeling evaluation sample. The water spray position was a position where the angle between the SUS plate and a line connecting the spray position and the center of the adhesive tape end was 30°, and directly above a point 5 cm horizontally away from the center of the adhesive tape end. After water spraying, the peeled distance of the adhesive tape was measured and evaluated according to the following criteria: ⊚: Peeled distance was 0 mm or more but less than 15 mm; ◯: Peeled distance was 15 mm or more but less than 20 mm; ×: Peeled distance was 20 mm or more.

[0096] <Topcoat adhesion> A fluorine-based topcoat paint conforming to JIS K5659:2018 (manufactured by Dai Nippon Toryo Co., Ltd., product name "V Flon #100H Smile Topcoat IG") was applied to a dry thickness of 25 μm, and the resulting measurement sample was dried at 23 ° C. for 16 hours. A cross-cut test conforming to JIS K5600-5-6 was performed on the resulting sample to evaluate topcoat adhesion and record the number of peeled grids. In the cross-cut test, the grid dimensions and number were 2 mm × 2 mm and 25, respectively.

[0097] <Evaluation of Top Coating> A general structural rolled steel material (SS400) measuring 70 mm long x 150 mm wide was prepared. Then, as shown in FIG. 4 , adhesive tapes (60 mm wide, 140 mm long) 10 of each Example and Comparative Example were attached to the rolled steel material 30. The rolled steel material 30 to which the adhesive tape 10 was attached was painted with a top coat paint (manufactured by Dai Nippon Toryo Co., Ltd., product name "V-Flon #100H Smile Top Coat") 40 using a brush. After the top coat paint 40 applied to the rolled steel material 30 was allowed to dry for 24 hours, the adhesive tape 10 was visually inspected for wrinkles. ○: The adhesive tape was wrinkle-free, and when the above-mentioned cross-cut test was performed, two or fewer grids peeled off. ×: The adhesive tape was wrinkled, or when the above-mentioned cross-cut test was performed, more than two grids peeled off.

[0098] [Materials Used] The following materials were used in each of the Examples and Comparative Examples.

[0099] <Adhesive Layer> 2-Ethylhexyl acrylate n-Butyl acrylate Acrylic acid ACMO: acryloylmorpholine Olefin polymer: product name "L-1253" manufactured by Kuraray Co., Ltd., hydrogenated polybutadiene having a (meth)acryloyl group at one end Tackifying resin 1: product name "Arcon P140" manufactured by Arakawa Chemical Industries, Ltd., hydrogenated petroleum resin, softening point 140°C Tackifying resin 2: product name "Arcon P100" manufactured by Arakawa Chemical Industries, Ltd., hydrogenated petroleum resin, softening point 100°C Fine particles: product name "Cellstar Z-27" manufactured by Tokai Kogyo Co., Ltd., glass balloon Metal having a lower electric potential than iron: zinc particles, product name "zinc powder #40" manufactured by Sakai Chemical Industry Co., Ltd., average particle size: 50 μm Conductive material: carbon nanotubes (CNT), manufactured by JEIO, product name "JENOTUBE8A", average diameter 6 to 9 nm, average length 100 to 200 μm Dispersant: Sekisui Chemical Co., Ltd., product name "S-LEC BX-L", polyvinyl butyral resin Cross-linking agent: product name "TEAI-1000", manufactured by Nippon Soda Co., Ltd. Polymerization initiator: 2,2-dimethoxy-2-phenylacetophenone Acrylic adhesive / main agent: product name "Olivine BPS6080TFK", manufactured by Toyochem Co., Ltd. Acrylic adhesive / hardener: product name "BHS8515", manufactured by Toyochem Co., Ltd. Adhesive tape: product name "VHB Y-4910J", manufactured by 3M

[0100] <Films> ・Soft acrylic resin film 1: Product name "Soft Acrylic Sheet", manufactured by Tatsuta Chemical Co., Ltd. ・Soft acrylic resin film 2: Product name "AC-090CL", manufactured by Lonseal Corporation ・Soft acrylic resin film 3: Product name "AC-340CL", manufactured by Lonseal Corporation ・Fluorocarbon resin film: Product name: "50NS", manufactured by AGC Inc. ・Polyvinyl chloride resin film: Product name "00C040M", manufactured by Nippon Carbide Industries Co., Ltd. ・Acrylic resin film: Product name "Acriplene MBS121E", manufactured by Mitsubishi Chemical Corporation ・Acrylic resin film: Product name "Acriplene HTXD37", manufactured by Mitsubishi Chemical Corporation ・Acrylic resin film: Product name "Acriplene HTXB16", manufactured by Mitsubishi Chemical Corporation ・Acrylic resin film: Product name "Acriplene HBS029E", manufactured by Mitsubishi Chemical Corporation・Polyolefin resin film (agricultural PO): Product name "Easter UV Cut", MKV Advance Co., Ltd. ・Acrylic silicone paint / main agent: Product name "Nippe Fine Glassy Si Clear Glossy Paint Liquid", manufactured by Nippon Paint Co., Ltd. ・Acrylic silicone paint / hardener: Product name "Nippe Fine Glassy Si Clear Hardener", manufactured by Nippon Paint Co., Ltd.

[0101] [Examples 1 to 12, Comparative Examples 1 to 4] Pressure-sensitive adhesive compositions were prepared according to the formulations shown in Tables 1, 2, and 5. In Tables 1, 2, and 5, "parts" means "parts by mass." Nitrogen was purged into this pressure-sensitive adhesive composition to remove dissolved oxygen. Next, a spacer having the same thickness as the pressure-sensitive adhesive layer was placed on the release-treated surface of the release sheet, and the pressure-sensitive adhesive composition was applied to the release-treated surface of the release sheet. Next, another release sheet was placed on top of the applied pressure-sensitive adhesive composition so that the release-treated surface was in contact with the pressure-sensitive adhesive composition. Note that a silicone release-treated PET film (thickness 50 μm) was used as the release sheet. In this state, the ultraviolet irradiation intensity on the coated side of the release sheet was 5 mW / cm ２The lamp intensity of the chemical lamp was adjusted so that UV light was irradiated from one side for 15 minutes, thereby obtaining a pressure-sensitive adhesive layer consisting of a single pressure-sensitive adhesive layer with release sheets attached to both sides. One release sheet was then peeled off, and a film (substrate) shown in Tables 1, 2, and 5 was attached to the pressure-sensitive adhesive layer obtained by the above method, thereby obtaining a pressure-sensitive adhesive tape. The other release sheet was also peeled off from the pressure-sensitive adhesive tape before various physical properties or evaluations were performed.

[0102] Examples 13 to 15 Pressure-sensitive adhesive compositions were prepared according to the formulations shown in Table 3. In Table 3, "parts" means "parts by mass." The pressure-sensitive adhesive composition was then applied to the release-treated surface of a release sheet using an applicator adjusted to the desired thickness. In this state, the sheet was placed in a 75°C oven and heated for 5 minutes. Another release sheet was then placed over the sheet so that the release-treated surface was in contact with the pressure-sensitive adhesive composition, and the sheet was cured at 23°C for 7 days to obtain a pressure-sensitive adhesive layer consisting of a single pressure-sensitive adhesive layer with release sheets attached to both sides. A silicone release-treated PET film (thickness: 50 μm) was used as the release sheet. A film (substrate) was also prepared according to the formulations shown in Table 3, and the coating liquid was applied to the release-treated surface of the release sheet using an applicator adjusted to the desired thickness. In this state, the sheet was placed in a 75°C oven and heated for 30 minutes. Next, another release sheet was applied so that the release-treated surface was in contact with the pressure-sensitive adhesive composition, and the film was cured at 23°C for 7 days to obtain a film with release sheets attached to both sides. One of the release sheets was then peeled off from each of the pressure-sensitive adhesive layer and the film (substrate), and the surfaces from which the release sheets had been peeled were attached to each other to obtain a pressure-sensitive adhesive tape. The release sheets on both sides of the pressure-sensitive adhesive tape were also peeled off before various physical properties or evaluations were performed.

[0103] [Examples 16 to 17] Instead of preparing a pressure-sensitive adhesive composition, a commercially available pressure-sensitive adhesive tape ("VHB Y-4910J") was used, and a film (substrate) shown in Table 4 was attached to one of the pressure-sensitive adhesive layers of the pressure-sensitive adhesive tape to obtain a pressure-sensitive adhesive tape.

[0104]

[0105]

[0106]

[0107]

[0108] *In each of the Examples and Comparative Examples, the substrate did not break during the adhesive strength test.

[0109] As is clear from the above examples, the pressure-sensitive adhesive tapes satisfying the requirements of the present invention were excellent in conformability and transparency, and had high weather resistance. Even when used outdoors for a long period of time, the pressure-sensitive adhesive tape was prevented from deteriorating or discoloring, and was able to maintain excellent corrosion resistance and transparency. In contrast, the pressure-sensitive adhesive tape prepared in Comparative Example 1 had a high UV transmittance of the substrate after the accelerated weather resistance test, resulting in poor weather resistance. Rust developed at the locations where the pressure-sensitive adhesive tape was attached after the test, indicating a decrease in the corrosion resistance of the tape. Furthermore, the pressure-sensitive adhesive tape prepared in Comparative Example 2 had a large color difference (ΔE) of the substrate after the test, resulting in a significant decrease in transparency, and the result of the substrate inspection was "X". Furthermore, the pressure-sensitive adhesive tape prepared in Comparative Example 3 had a large tensile load difference, resulting in poor conformability. Furthermore, the pressure-sensitive adhesive tape prepared in Comparative Example 4 had a low total light transmittance both before and after the accelerated weather resistance test, resulting in poor transparency.

[0110] DESCRIPTION OF SYMBOLS 10 Adhesive tape 11 Adhesive layer 11A Surface of adhesive layer 11B First adhesive layer 11C Second adhesive layer 12 Substrate 13 Intermediate layer 20 L-shaped SUS plate 20A Adherend surface 30 General structural rolled steel material 40 Topcoat paint h Height t Width

Claims

1. An adhesive tape comprising a base material and an adhesive layer provided on at least one side of the base material, wherein the adhesive tape has a total light transmittance of 30% or more, and the difference between the tensile load at 2.5% elongation and the tensile load at 0.5% elongation is less than 2.0 N / mm; the base material has a transmittance of ultraviolet light with a wavelength of 340 nm of 5% or less, and a color difference (ΔE) of 5 or less after performing an accelerated weather resistance test for 500 hours, and is an adhesive tape for concrete, mortar, underwater materials or metal materials.

2. The adhesive tape according to claim 1, wherein the tensile break elongation of the adhesive tape is 100% or more.

3. The adhesive tape according to claim 1 or 2, wherein the total light transmittance of the adhesive tape is 30% or more after performing an accelerated weather resistance test for 500 hours in accordance with Cycle A in JIS K5600-7-7.

4. The adhesive tape according to claim 1 or 2, wherein in a peel test performed after performing an accelerated weather resistance test for 500 hours in accordance with Cycle A in JIS K5600-7-7, the base material does not break, and the adhesive strength of the adhesive layer is 20 N / 25 mm or more.

5. The adhesive tape according to claim 1 or 2, wherein the Elmendorf tear strength of the base material measured without slitting in the Elmendorf tear method in accordance with JIS K7128-2 (1998) is 1.7 N or more.

6. For a measurement sample obtained by overcoating a fluorine-based topcoat paint compliant with JIS K5659:2018 on the base material to a thickness of 25 μm and drying it at 23°C for 16 hours, when a crosshatch test compliant with JIS K5600-5-6 is performed, none of the grids are peeled off. The adhesive tape according to claim 1 or 2.

7. The adhesive tape according to claim 1 or 2, wherein the dimensional change rate of the base material after immersing the base material in xylene for 5 minutes is 3% or less.

8. The adhesive tape according to claim 1 or 2, wherein the gloss retention rate of the base material after performing the accelerated weather resistance test for 500 hours is 80% or more.

9. The adhesive tape according to claim 1 or 2, wherein the base material contains an acrylic resin.

10. The adhesive tape according to claim 1 or 2, wherein the thickness of the base material is 20 to 300 μm.

11. The adhesive tape according to claim 1 or 2, wherein the thickness of the adhesive layer is 50 to 2500 μm.

12. The pressure-sensitive adhesive tape according to claim 1 or 2, wherein the pressure-sensitive adhesive layer is formed of a photocurable resin.

13. The pressure-sensitive adhesive tape according to claim 1 or 2, wherein the pressure-sensitive adhesive layer is formed of an acrylic pressure-sensitive adhesive.

14. The pressure-sensitive adhesive tape according to claim 1 or 2, wherein the storage elastic modulus of the pressure-sensitive adhesive layer at 23°C is 50,000 to 1,000,000 Pa.

15. The pressure-sensitive adhesive tape according to claim 1 or 2, wherein the pressure-sensitive adhesive layer contains a metal having a lower potential than iron.

16. The pressure-sensitive adhesive tape according to claim 15, wherein the metal having a lower potential than iron is zinc.

17. The pressure-sensitive adhesive tape according to claim 1 or 2, wherein the pressure-sensitive adhesive layer contains a conductive material other than a metal having a lower potential than iron.

18. The pressure-sensitive adhesive tape according to claim 17, wherein the conductive material is a carbon nanotube.

19. A method of using a pressure-sensitive adhesive tape, wherein the pressure-sensitive adhesive tape according to claim 1 or 2 is attached to the surface of a concrete structure or a structure having a rusty part.

20. The method of using a pressure-sensitive adhesive tape according to claim 19, wherein an anti-rust progress agent or a primer is applied to the attachment surface of the pressure-sensitive adhesive tape, and then the pressure-sensitive adhesive tape is attached.

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