Adhesive tape, instructions on how to use adhesive tape

Abstract

To provide an adhesive tape which has excellent followability and transparency and high weather resistance and can prevent the deterioration of adhesive strength even after long-term use outdoors.SOLUTION: There is provided an adhesive tape for a concrete structure or a structure having a rusted part, which is an adhesive tape comprising a base material and an adhesive layer provided on at least one surface of the base material, wherein the adhesive tape has 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 and has a tensile elongation at break of 100% or more, the total light transmittance of the adhesive tape is 50% or more after performing the accelerated weather resistance test according to cycle A in JIS K5600-7-7 for 500 hours, the peeling angle obtained by bonding the adhesive tape to a stainless steel plate through the adhesive layer after performing the accelerated weather resistance test for 500 hours is 180 degree, the base material does not break in a peeling test conducted under the condition of a peeling speed of 300 mm / minute and the adhesive strength of the adhesive layer is 20 N / 25 mm or more.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Large structures such as viaducts, tunnels, bridges, towers, and tanks are often constructed by combining steel materials and concrete materials. Steel materials and concrete materials corrode over time, and rust, cracks, and fissures occur. When these corrosions progress, for example, the corroded parts may be repaired by applying paint or an adhesive to the surface of the structure. However, such repair methods have complex work processes and require a considerable amount of time until the actual repair work is started. Therefore, there are problems such as further progress of rust at the corroded parts or falling of concrete pieces from the corroded parts before the actual repair work is started.

[0003] As a method of simplifying the process of repairing corroded parts, it is known to suppress the progress of corrosion by attaching a sheet to the corroded parts. However, since the sheet is often highly rigid and opaque, the sheet may not be properly attached following the corroded parts. In addition, it is impossible to visually check whether corrosion is progressing inside the sheet, and corrosion often progresses without sufficient recognition of the progress of corrosion, and preventive measures against corrosion cannot be effectively taken. Therefore, conventionally, for example, as disclosed in Patent Document 1, a laminated sheet excellent in followability and transparency has been proposed as a sheet used for a concrete structure or a structure having a rusted part.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, Patent Document 1 does not discuss weather resistance for laminated sheets, and there is a risk that the sheets may deteriorate due to ultraviolet rays and other factors if used outdoors for a long period of time. Therefore, there is a problem in that it is not suitable for long-term outdoor use. Therefore, the object of the present invention is to provide an adhesive tape that has excellent conformability and transparency, high weather resistance, and can prevent deterioration of adhesive strength even when used outdoors for a long period of time. [Means for solving the problem]

[0006] As a result of diligent research, the inventors of the present invention have found that the above problems can be solved by having the following configuration, and have completed the present invention. The present invention provides the following [1] to

[17] . [1] An adhesive tape comprising a base material and an adhesive layer provided on at least one side of the base material, wherein the difference between the tensile load when stretched by 2.5% and the tensile load when stretched by 0.5% is 1.3 N / mm or less, the elongation at the tensile breaking point is 100% or more, the total light transmittance of the adhesive tape is 50% or more after an accelerated weathering test in accordance with Cycle A of JIS K5600-7-7 is performed for 500 hours, the base material does not break in a peel test performed after the accelerated weathering test is performed for 500 hours, and the adhesive strength of the adhesive layer is 20 N / 25 mm or more, an adhesive tape for concrete structures or structures with rusted parts. [2] The adhesive tape according to [1], wherein the Elmendorf tear strength of the substrate, measured without making a slit in the Elmendorf tear test in accordance with JIS K7128-2 (1998), is 1.7 N or more. [3] The adhesive tape described in [1] or [2], wherein when a fluorine-based topcoat paint conforming to JIS K5659:2018 is applied to the substrate to a thickness of 25 μm and dried at 23°C for 16 hours, and a grid test is performed on the obtained sample in accordance with JIS K5600-5-6, none of the grid lines peel off. [4] The adhesive tape according to any one of [1] to [3], wherein the dimensional change rate of the substrate after immersing the substrate in xylene for 5 minutes is 3% or less. [5] The adhesive tape according to any one of [1] to [4], wherein the gloss retention rate of the substrate after the accelerated weathering test has been carried out for 500 hours is 80% or more. [6] The adhesive tape according to any one of [1] to [5], wherein the base material comprises at least one selected from the group consisting of polyvinyl chloride resin, acrylic resin, and fluororesin. [7] The adhesive tape according to any one of [1] to [6], wherein the thickness of the base material is 20 to 300 μm. [8] The adhesive tape according to any one of [1] to [7], wherein the thickness of the adhesive layer is 50 to 2500 μm. [9] The adhesive tape according to any one of [1] to [8], wherein the adhesive layer is formed of a photocurable resin.

[10] The adhesive tape according to any one of [1] to [9], wherein the adhesive layer is formed of an acrylic adhesive.

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

[10] , wherein the storage modulus of the adhesive layer at 23°C is 50,000 to 1,000,000 Pa.

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

[11] , wherein the adhesive layer contains a metal having a lower potential than iron.

[13] The adhesive tape described in

[12] , wherein zinc is a metal with a lower potential than iron.

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

[13] , wherein the adhesive layer contains a conductive material other than a metal having a lower potential than iron.

[15] The adhesive tape according to

[14] , wherein the conductive material is carbon nanotubes. A method of using adhesive tape, wherein the adhesive tape described in any of

[16] [1] to

[15] is applied to the surface of a concrete structure or a structure having rusted parts.

[17] The method of using the adhesive tape described in

[16] , wherein a rust inhibitor or primer is applied to the surface to which the adhesive tape is attached, and then the adhesive tape is attached. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an adhesive tape that has excellent conformability and transparency, high weather resistance, and can prevent deterioration of adhesive strength even when used outdoors for a long period of time. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing one embodiment of the adhesive tape of the present invention. [Figure 2] This is a schematic diagram illustrating a method for evaluating the conformability of the adhesive tape of the present invention. [Figure 3] This is a diagram to explain the evaluation of topcoat painting. [Modes for carrying out the invention]

[0009] [Adhesive tape] The adhesive tape of the present invention comprises a base material and an adhesive layer provided on at least one side of the base material. A more detailed description follows.

[0010] <Difference in tensile load> The adhesive tape of the present invention has a difference of 1.3 N / mm or less between the tensile load when stretched by 2.5% and the tensile load when stretched by 0.5% (hereinafter sometimes simply referred to as "difference in tensile load"). The difference in tensile load essentially represents the tensile load per 2% elongation in the elastic region. When the difference in tensile load is small, it becomes easier to adhere to the shape of the adherend (e.g., steps), and even when stretched and applied to the adherend, less stress is generated due to shrinkage after application, so the adhesive strength after application is easily maintained. When the difference in tensile load exceeds 1.3 N / mm, the followability of the adhesive tape cannot be fully exhibited, and there may be problems such as the inability to properly attach to an adherend with a complex shape. Further, the difference in tensile load is not particularly limited, but from the viewpoint of imparting a certain firmness and workability to the adhesive tape and effectively preventing problems during construction, it is preferably 0.4 N / mm or more, more preferably 0.7 N / mm or more, and even more preferably 1.0 N / mm or more. The difference in tensile load is measured in the MD direction and TD direction of the adhesive tape, respectively, and the larger value is adopted. Also, when the MD direction and TD direction are unknown, it is advisable to adopt the value with the largest difference in tensile load. The difference in tensile load can be obtained by the measuring method described in the examples.

[0011] <Elongation at tensile break point> The adhesive tape of the present invention has an elongation at tensile break point of 100% or more. When the elongation at tensile break point of the adhesive tape is less than 100%, when attempting to adhere the adhesive tape in a stretched state, the adhesive tape may tear or may not sufficiently follow the adherend, so there is a risk that the adhesive tape cannot be properly attached to the adherend. From such a viewpoint, the elongation at tensile break point of the base material is preferably 105% or more, more preferably 150% or more, and even more preferably 200% or more. On the other hand, the upper limit value of the elongation at tensile break point of the adhesive tape is not particularly limited, but from the viewpoint of mechanical strength and the like, it is preferably 700% or less, more preferably 600% or less. The elongation at tensile break point is measured in the MD direction and TD direction of the adhesive tape, respectively, and the smaller value is adopted. Also, when the MD direction and TD direction are unknown, it is advisable to adopt the value with the smallest elongation at tensile break point. The elongation at tensile break point can be obtained by the measuring method described in the examples. Also, the difference in tensile load and the elongation at tensile break point of the adhesive tape can be adjusted within the above ranges by appropriately selecting the materials used for the base material and the adhesive layer, the thickness of the adhesive tape, and the like.

[0012] The adhesive tape of the present invention preferably has a total light transmittance of 55% or more, more preferably 60% or more, and even more preferably 70% or more. Here, the total light transmittance is measured before the accelerated weather resistance test described later, and is also referred to as the initial total light transmittance. Since the initial total light transmittance of the adhesive tape of the present invention is at least the above lower limit value, the transparency immediately after the adhesive tape is attached to the adherend is good. In addition, it becomes easier to make the total light transmittance after the accelerated weather resistance test a certain value or more. The higher the initial total light transmittance, the better, and it may be 100% or less, but in practical use, it may be, for example, 97% or less. The adhesive tape of the present invention preferably has an adhesive strength of 15 N / 25 mm or more, more preferably 20 N / 25 mm or more, and even more preferably 30 N / 25 mm or more. Here, the adhesive strength is measured before the accelerated weather resistance test described later, and is also referred to as the initial adhesive strength. Since the initial adhesive strength of the adhesive tape of the present invention is at least the above lower limit value, it is easily attached to the adherend with a high adhesive strength. In addition, it becomes easier to make the adhesive strength after the accelerated weather resistance test a certain value or more. The initial adhesive strength is not particularly limited, but in practical use, it is, for example, 200 N / 25 mm or less.

[0013] <Each physical property after the accelerated weather resistance test> (Total light transmittance) The total light transmittance of the adhesive tape of the present invention is 50% or more after conducting an accelerated weather resistance test in accordance with Cycle A in JIS K5600-7-7 for 500 hours. If the total light transmittance is less than 50%, the transparency cannot be ensured after the adhesive tape is used outdoors for a long time, and it becomes difficult to visually recognize the progress of corrosion at the location where the adhesive tape is adhered from above the tape. From the viewpoint of improving the visibility after long-term use, the above total light transmittance is preferably 52% or more, and more preferably 60% or more. The higher the total light transmittance, the better, and it may be 100% or less, but in practical use, it is 95% or less.

[0014] Furthermore, the adhesive tape of the present invention preferably has a total light transmittance of 50% or more, more preferably 52% or more, and even more preferably 60% or more, after undergoing an accelerated weathering test in accordance with Cycle A of JIS K5600-7-7 for 1000 hours. Moreover, the tape preferably has a total light transmittance of 50% or more, more preferably 52% or more, and even more preferably 60% or more, after undergoing the same test for 2000 hours. The higher the total light transmittance, the better; it should ideally be 100% or less, but in practical terms, it should be 95% or less.

[0015] The total light transmittance can be obtained by the measurement method described in the examples. Furthermore, the total light transmittance can be adjusted within the above range by appropriately selecting the materials used for the substrate and adhesive layer, the thickness of the adhesive layer, etc.

[0016] (Adhesive strength) The adhesive tape of the present invention is such that, in a peel test conducted after an accelerated weathering test in accordance with Cycle A of JIS K5600-7-7 for 500 hours, the substrate does not break and the adhesive strength of the adhesive layer is 20 N / 25 mm or more. If the substrate breaks during a peel test after an accelerated weathering test, the adhesive tape lacks weather resistance and is unsuitable for long-term outdoor use. Furthermore, if the adhesive strength is less than 20 N / 25 mm, the long-term adhesive strength will be insufficient, the adhesive tape will easily peel off the substrate, and its corrosion resistance will also decrease. From the viewpoint of maintaining high adhesive strength over a long period of time, the adhesive strength after accelerated weathering testing is preferably 25 N / 25 mm or higher, more preferably 30 N / 25 mm or higher, and even more preferably 40 N / 25 mm or higher. The higher the adhesive strength, the better, but in practical terms, it is 200 N / 25 mm or lower.

[0017] Furthermore, the adhesive strength of the adhesive layer of the adhesive tape of the present invention in a peel test conducted after 1000 hours of accelerated weathering testing in accordance with Cycle A of JIS K5600-7-7 is preferably 20 N / 25 mm or more, 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. Moreover, the adhesive strength of the adhesive layer of the tape in a peel test conducted after 2000 hours of the same test is preferably 20 N / 25 mm or more, 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. While higher adhesive strength is always better, practically speaking, 200N / 25mm or less is sufficient.

[0018] The adhesive strength of the adhesive tape after accelerated weathering testing is measured as follows: A sample for evaluating adhesion strength is prepared by attaching the adhesive tape of the present invention to a stainless steel plate (SUS plate). During this process, the adhesive layer of the tape is attached so that it is in contact with the surface of the SUS plate. 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 moving a 2 kg roller back and forth twice at a speed of 10 ± 0.5 mm / s. Using the adhesive strength evaluation sample, accelerated weathering tests will be conducted according to Cycle A of JIS K5600-7-7. The tests will be conducted for a total of 500 hours. For samples used to evaluate adhesion strength after accelerated weathering testing, the adhesion strength is measured by a peel test of the adhesive tape. In the peel test, a tensile testing machine is used to pull the tape at a length of 60 mm or more under conditions of 23°C and 50 RH, with a peel angle of 180° and a speed of 300 mm / min. The average value of the detected load (N) over the interval is taken as the adhesion strength. The condition of the substrate described above can also be confirmed by the same peel test.

[0019] (Elmendorf tear strength) In the substrate used for the adhesive tape of the present invention, the Elmendorf tear strength measured without slitting in the Elmendorf tear method in accordance with JIS K7128-2 (1998) is preferably 1.7 N or higher, more preferably 3.0 N or higher, even more preferably 6.0 N or higher, and even more preferably 12 N or higher. Having an Elmendorf tear strength of the substrate measured without slitting that is above the above lower limit makes it easier to impart excellent conformability to the adhesive tape. Furthermore, when measuring the Elmendorf tear strength of a substrate without making slits, a higher value is better, and the upper limit of this range is, for example, 16N. Furthermore, when measuring the Elmendorff tear strength of a substrate without making slits, the measurement should be taken in both the MD direction and the TD direction of the substrate, and the smaller of the two values ​​should be adopted. In cases where the MD and TD directions are unknown, the smallest Elmendorff tear strength value should be adopted. The Elmendorff tear strength of a substrate measured without making slits can be measured in the same manner as the Elmendorff tear test method compliant with JIS K7128-2 (1998), except that the measurement is taken without making slits. Furthermore, the Elmendorf tear strength of the substrate measured without making slits can be adjusted to the above range by appropriately selecting the material used for the substrate, the thickness of the substrate, etc.

[0020] (Gloss retention rate) The 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, after undergoing an accelerated weathering test in accordance with Cycle A of JIS K5600-7-7 for 500 hours. If the gloss retention rate is above the lower limit, it is possible to prevent the adhesive strength of the adhesive tape from decreasing or the appearance of the adhesive tape from deteriorating when exposed to light for a long period of time, such as when the adhesive tape is used outdoors. The higher the gloss retention rate, the better, with an upper limit of 100%. The gloss retention rate of the adhesive tape after the accelerated weathering test can be determined by measuring the haze B of the substrate before the accelerated weathering test and the haze A of the substrate after the accelerated weathering test, and using the following formula. The details of the measurement method can be carried out as described in the examples below. Gloss retention rate (%) = (Haze B / Haze A) × 100

[0021] Furthermore, the 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, after undergoing an accelerated weathering test in accordance with Cycle A of JIS K5600-7-7 for 1000 hours. Moreover, the tape preferably has a gloss retention rate of 80% or more, more preferably 85% or more, and even more preferably 90% or more, after undergoing the same test for 2000 hours. The higher these gloss retention rates are, the better, with an upper limit of 100%.

[0022] <Base material> The base material for the adhesive tape of the present invention should preferably be weather-resistant. By using a weather-resistant base material, the adhesive tape can be made not only to have excellent conformability and transparency, but also to have excellent weather resistance, so that the adhesive tape will not deteriorate even when exposed to light for a long period of time, such as when used outdoors. One way to make a substrate weather-resistant is to impart weather resistance to the substrate itself. Specifically, this can be achieved by using a weather-resistant resin in the resin that makes up the substrate, or by incorporating ultraviolet absorbers, light stabilizers (HALS), etc., into the resin that makes up the substrate. Furthermore, a weather-resistant film may be formed on the surface of the substrate to provide weather resistance. The weather-resistant film is preferably formed on at least one surface of the substrate. The weather-resistant film can be formed, for example, by applying a weather-resistant paint.

[0023] As a weather-resistant substrate, a resin film is preferred, and as the resin constituting the resin film, for example, acrylic resin, fluororesin, polycarbonate resin, polyvinyl chloride resin, AES resin, ASA resin, etc., can be preferably used. These resins may be used individually or in combination of two or more. As the above resin, at least one selected from the group consisting of polyvinyl chloride resin, acrylic resin, and fluororesin is preferred. Therefore, as the resin film, it is preferable to use at least one of polyvinyl chloride resin film, acrylic resin film, and fluororesin film, with polyvinyl chloride resin film being more preferred among them. The resin film used as the substrate may be single-layer or multi-layer. In the case of multi-layer, only resin films of the same type may be laminated, or two or more types of resin films may be laminated.

[0024] By using the resins described above, the resin film can impart weather resistance to the substrate without the need for UV absorbers, light stabilizers, or the application of weather-resistant coatings. This prevents the bleed-out of UV absorbers and light stabilizers. Furthermore, it eliminates the need to apply coatings to the substrate surface, improving the production efficiency of adhesive tapes. Furthermore, acrylic resin films are particularly excellent at protecting adhesive layers because of the strong interatomic bonding forces within the acrylic resin, which is the main component, and their low ultraviolet light transmittance. Fluorine resin films, on the other hand, are thought to have high weather resistance due to the strong interatomic bonding forces between fluorine atoms and other atoms.

[0025] Preferably, the substrate constituting the adhesive tape of the present invention has the property of not peeling off any grid when 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 is subjected to a grid test in accordance with JIS K5600-5-6. The adhesive tape of the present invention may be applied to a substrate and then coated with a topcoat paint. Therefore, having such physical properties in the substrate improves the adhesion between the substrate and the topcoat paint, making the topcoat paint less likely to peel off.

[0026] (Rate of dimensional change after xylene immersion) The dimensional change rate of the substrate used in the 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 upper limit, solvent resistance is imparted to the tape, and when a topcoat paint is applied to the substrate to which the adhesive tape is attached, wrinkles are prevented from forming on the adhesive tape after the paint dries, making it easier to maintain a good appearance of the substrate to which the topcoat paint has been applied. On the other hand, the lower limit of the range of dimensional change rate of the substrate after immersing the substrate used in the adhesive tape of the present invention in xylene for 5 minutes is not particularly limited, but is preferably 0%. The dimensional change rate of the substrate after xylene immersion can be measured, for example, by the method described in the examples below. Furthermore, the dimensional change rate of the substrate after xylene immersion can be adjusted within the above range by appropriately selecting the materials used for the substrate. When applying a topcoat, the substrate is preferably one that has high adhesion to the topcoat paint and a low rate of dimensional change after xylene immersion. From this viewpoint, an acrylic resin film is preferred.

[0027] The thickness of the substrate is preferably 20 to 300 μm, more preferably 30 to 200 μm, and even more preferably 40 to 100 μm. The substrate can function as a support when its thickness is above the lower limit. Furthermore, by making the thickness below the upper limit, it becomes easier to improve the conformability to the adherend and transparency.

[0028] <Adhesive layer> The adhesive tape of the present invention comprises an adhesive layer on at least one surface of the substrate. The adhesive layer will be described below.

[0029] (Adhesive) The adhesive layer is preferably formed by an adhesive. The type of adhesive is not particularly limited, but examples include acrylic adhesives, rubber adhesives, urethane adhesives, and silicone adhesives. These may be used individually or in combination. Furthermore, it is preferable that the adhesive layer be formed from a photocurable resin. As mentioned 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 made. As a result, it becomes easier to follow the irregularities of the surface of the adherend, increasing the adhesion area with the adherend and reducing the risk of peeling. The adhesive layer is more preferably formed from an acrylic adhesive among photocurable resins. The adhesive layer can be formed by using a photocurable polymer as the main polymer constituting the adhesive; for example, in the case of an acrylic adhesive, the acrylic polymer can be of photocurable type.

[0030] (Acrylic adhesive) Acrylic adhesives are adhesives that contain an acrylic polymer obtained by polymerizing polymerizable monomers, including (meth)acrylate alkyl ester monomer (A). In this specification, the term "(meth)acrylate alkyl ester" refers to a concept that includes both alkyl acrylates and alkyl methacrylates, and the same applies to other similar terms. Furthermore, the term "polymerizable monomer" refers to a concept that may include not only compounds without repeating units, but also compounds copolymerized with (meth)acrylate alkyl ester monomers (A), including olefin polymers (C) described later, in which the monomer itself has repeating units.

[0031] ((meth)acrylate alkyl ester monomer (A)) The alkyl (meth)acrylate 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, it is easier to increase the adhesive strength and to adjust the storage modulus of the adhesive at 23°C, which will be described later, to a predetermined range.

[0032] Specific examples of alkyl (meth)acrylate monomers (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 combinations thereof are more preferred. In particular, by using at least n-butyl (meth)acrylate, the tackiness of the adhesive can be appropriately controlled, and the workability when applying the adhesive tape can be improved. (Meth)acrylate alkyl ester monomer (A) may be used alone or in combination of two or more types.

[0033] The constituent units derived from the alkyl methacrylate monomer (A) constitute the main component in the adhesive layer, and their 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 adhesive layer. In this way, increasing the content of the alkyl methacrylate monomer (A) makes it possible to impart the desired adhesive strength to the adhesive layer. Furthermore, the above content of the constituent units derived from the alkyl methacrylate 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 include a certain amount or more of other components. Furthermore, the content of constituent units derived from (meth)acrylate alkyl ester monomer (A) in the adhesive layer is substantially the same as the content of (meth)acrylate alkyl ester monomer (A) in the adhesive composition described later, and can therefore be expressed interchangeably. The same applies to components other than component (A), such as components (B) and (C) described below.

[0034] (Polar group-containing vinyl monomer (B)) The polymerizable monomer preferably contains a polar group-containing vinyl monomer (B) in addition to an alkyl (meth)acrylate monomer (A). The polar group-containing vinyl monomer (B) has a polar group and a vinyl group. Using the polar group-containing monomer (B) makes it easier to improve the adhesion to the adherend. Examples of polar group-containing vinyl monomers (B) include vinyl carboxylate esters such as vinyl acetate, vinyl group-containing carboxylic acids such as (meth)acrylic acid and itaconic acid, and their anhydrides, vinyl monomers having hydroxyl groups 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, and nitrogen-containing vinyl monomers such as (meth)acrylonitrile, N-vinylpyrrolidone, N-vinylcaprolactam, N-vinyllauricolactam, (meth)acryloylmorpholine, (meth)acrylamide, dimethyl (meth)acrylamide, N-methylol (meth)acrylamide, N-butoxymethyl (meth)acrylamide, and dimethylaminomethyl (meth)acrylate. Among these, vinyl group-containing carboxylic acids such as (meth)acrylic acid and itaconic acid, and their anhydrides 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 individually or in combination of two or more.

[0035] When using polar group-containing vinyl monomer (B), the content of constituent units derived from polar group-containing vinyl monomer (B) in the 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 constituent units derived from alkyl (meth)acrylate monomer (A). By setting the content of polar group-containing vinyl monomer (B) within this range, it becomes easier to improve the adhesive strength of the adhesive tape.

[0036] (Olefin polymer (C)) The polymerizable monomer preferably further contains an olefin polymer (C) having a polymerizable bond at one end. Using such an olefin polymer (C) makes it easier to improve the adhesive strength of the adhesive tape. A polymerizable bond refers to an unsaturated carbon-carbon bond that can polymerize with polymerizable monomers. Examples include unsaturated double bonds, and preferably (meth)acryloyl groups. Examples of olefin polymers (C) include polyolefins having a (meth)acryloyl group at one end. Polyolefins are polymers of aliphatic hydrocarbon compounds having double bonds, such as ethylene, propylene, butane, butadiene, and isoprene, or their hydrogenated products.

[0037] Examples of polyolefins having a (meth)acryloyl group at one end include polyethylene having a (meth)acryloyl group at one end, prepared by reacting polyethylene having an epoxy group at one end with (meth)acrylic acid. Other examples include polybutadiene having a (meth)acryloyl group at one end or its hydrogenated products, with "L-1253" manufactured by Kuraray Co., Ltd. being a commercially available example.

[0038] 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 can be measured by gel permeation chromatography (GPC) and calculated using a calibration curve for standard polystyrene. Furthermore, the content of constituent units derived from the olefin polymer (C) in the 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 constituent units derived from the alkyl (meth)acrylate monomer (A).

[0039] (Crosslinking agent (D)) The polymerizable monomer preferably further contains a crosslinking agent. Examples of crosslinking agents include polyfunctional monomers having two or more vinyl groups, and preferably polyfunctional (meth)acrylates having two or more (meth)acryloyl groups. Using polyfunctional monomers makes it easier to adjust the tackiness of the adhesive layer to an appropriate range. The polyfunctional (meth)acrylate is not particularly limited and includes hexanediol di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, tris(2-hydroxyethyl) isocyanurate triacrylate, ethoxylated trimethylolpropane triacrylate, proxiated trimethylolpropane triacrylate, proxiated glyceryl triacrylate, neopentyl glycol adipate diacrylate, and 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. A commercially available liquid hydrogenated 1,2-polybutadiene diacrylate is "TEAI-1000" manufactured by Nippon Soda Co., Ltd. Furthermore, the content of the crosslinking agent-derived structural units in the 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 structural units derived from (meth)acrylate alkyl ester monomer (A). When the crosslinking agent content is within the above range, it becomes easier to adjust the adhesive strength of the adhesive layer to an appropriate range.

[0040] (Adhesive-granting resin) Acrylic adhesives may contain a tackifying resin to improve adhesive strength. Preferred tackifying resins include those with low polymerization inhibitory properties, such as hydrogenated terpene resins, hydrogenated rosin, disproportionated rosin resins, and petroleum resins. Among these, hydrogenated resins are preferred, and hydrogenated petroleum resins are particularly preferred, as tackifying resins with many double bonds inhibit the polymerization reaction. The softening point of the tackifying resin should be approximately 95°C or higher from the viewpoint of improving the cohesive force and adhesive strength of the adhesive, but it is preferable to include resins with a softening point of 120°C or higher. Furthermore, from the viewpoint of improving adhesion to the adherend, for example, a combination of resins with a softening point of 95°C or higher but less than 120°C and resins with a softening point of 120°C or higher but less than 150°C may be used. The softening point should be measured by the ring-and-ball method specified in JIS K2207. The content of the tackifying resin in the acrylic 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 constituent units derived from the alkyl ester monomer (A) (meth)acrylate.

[0041] (fine particles) Acrylic adhesives may contain fine particles. The inclusion of fine particles can improve adhesive strength. Examples of fine particles 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 fine particles such as glass beads, silica beads, and synthetic mica; and organic fine particles such as ethyl polyacrylate, polyurethane, polyethylene, and polypropylene. The content of fine particles in the acrylic 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 constituent units derived from the alkyl ester monomer (A) (meth)acrylate.

[0042] (Other ingredients) The acrylic adhesive used in the adhesive layer may also contain various additives conventionally used in adhesives, such as plasticizers, softeners, pigments, dyes, dispersants, photopolymerization initiators, and flame retardants, in addition to the components mentioned above.

[0043] (Rubber-based adhesive) Rubber-based adhesives contain 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 has a diblock ratio of preferably 25 to 70% by mass, more preferably 30 to 65% by mass, and even more preferably 45 to 60% by weight. Here, a diblock refers to a diblock composed of styrene and isoprene. Setting the diblock ratio within the above range makes it easier to increase the 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 a styrene block.

[0044] The amount of styrene in the styrene-isoprene block copolymer is not particularly limited, but is preferably 14 to 24% by mass, and more preferably 15 to 18% by mass. When the amount of styrene is 14% by mass or more, it tends to become an adhesive with high cohesiveness. On the other hand, when the amount of styrene is 24% by mass or less, the cohesive force becomes of an appropriate magnitude, making it easier to exhibit adhesiveness. The molecular weight of the styrene-isoprene block copolymer is not particularly limited, but is preferably 100,000 to 400,000 by weight-average molecular weight, and more preferably 150,000 to 250,000. Here, weight-average molecular weight refers to the molecular weight measured as polystyrene-equivalent molecular weight by GPC (gel permeation chromatography).

[0045] Various tackifying resins can be used in rubber-based adhesives, but petroleum-based resins, terpene resins, and coumarone resins are preferred. The tackifying resin may be used alone or in combination of two or more, but it is preferable to use a combination of petroleum-based resin and at least one selected from terpene resins and coumarone resins. Such a combination of tackifying resins makes it easier to improve the adhesive strength. Examples of petroleum-based resins include aliphatic petroleum resins (C5 petroleum resins), alicyclic petroleum resins, and aromatic petroleum resins, with aliphatic petroleum resins being preferred from the viewpoint of compatibility with styrene-isoprene block copolymers. Furthermore, it is preferable to use petroleum-based resins with a softening point of approximately 90 to 120°C. Furthermore, while terpene resins with a softening point of approximately 80 to 120°C can be used, those with a softening point of less than 100°C are preferred from the viewpoint of ensuring adhesive strength. In addition, for coumarone resins, those with a softening point of preferably 110 to 130°C, and more preferably 115 to 125°C, are used to ensure cohesive strength.

[0046] The tackifying resin is preferably in an amount of 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 amount of tackifying resin within the above range, it becomes possible to improve the cohesive force and impart appropriate tackiness. Furthermore, when using a combination of petroleum-based resin and at least one selected from terpene resin and coumarone resin, the amount of petroleum-based resin is preferably 50 to 200 parts by mass, preferably 60 to 150 parts by mass, and more preferably 60 to 110 parts by mass, per 100 parts by mass of rubber component. On the other hand, the amount of 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 rubber component. Furthermore, the amount of 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 rubber component. The rubber-based adhesive may contain the fine particles described above, similar to the acrylic-based adhesive. Furthermore, the rubber-based adhesive may optionally contain sacrificial corrosion protection metals, conductive materials, softeners, antioxidants, fillers, etc.

[0047] (Urethane-based adhesive) The urethane adhesive is not particularly limited and includes, for example, a urethane resin obtained by reacting at least a polyol with a polyisocyanate compound. Examples of the polyol include polyether polyol, polyester polyol, polycarbonate polyol, and polycaprolactone polyol. Examples of the polyisocyanate compound include diphenylmethane diisocyanate, tolylene diisocyanate, and hexamethylene diisocyanate. These urethane adhesives may be used individually or in combination of two or more. Furthermore, as a urethane-based adhesive, a urethane resin obtained by reacting a polyurethane polyol with a polyfunctional isocyanate-based curing agent may be used. Examples of polyurethane polyols include those obtained by reacting the above-mentioned polyol with a polyisocyanate compound, or those obtained by reacting a polyol with a polyisocyanate compound and a chain extender such as a diamine. As the polyfunctional isocyanate-based curing agent, any compound having two or more isocyanate groups is acceptable, 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, as necessary, tackifying resins, sacrificial corrosion protection metals, conductive materials, softeners, antioxidants, fillers, etc.

[0048] (Silicone-based adhesive) Examples of silicone-based adhesives include addition reaction type, peroxide curing type, or condensation reaction type silicone-based adhesives. Among these, addition reaction type silicone-based adhesives are preferred from the viewpoint of being able to cure at low temperatures and in a short time. Addition reaction type silicone-based adhesives cure 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, silicone-based adhesives may contain fine particles, and may also contain crosslinking agents and various additives to control adhesive strength.

[0049] (Metals with a lower electrical potential than iron) The adhesive layer preferably contains a metal with a lower potential than iron. By including 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 resistance of the adhesive tape. The sacrificial corrosion protection metal is dispersed in the adhesive that constitutes the adhesive layer.

[0050] Examples of sacrificial corrosion protection metals include cadmium, chromium, zinc, manganese, and aluminum. Among these, zinc and aluminum are preferred, with zinc being particularly preferred. Using zinc results in superior sacrificial corrosion protection.

[0051] The sacrificial corrosion protection metal may be dispersed in the adhesive as a filler in any form, such as particulate, flake, or spindle-shaped, but it is preferably in particulate form. By using particulate form, the sacrificial corrosion protection metal is easily dispersed in the adhesive layer without significantly reducing the adhesiveness of the adhesive layer. In this specification, particle shape refers to a particle with a small ratio of length in the long axis direction to length in the short axis direction (aspect ratio), for example, an aspect ratio of 3 or less, preferably 2 or less. The particle shape is not particularly limited, and may be spherical or amorphous, such as a powder. The particle shape of the above metal has a particle size of, 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.

[0052] When the adhesive layer contains a sacrificial corrosion-preventive metal, the content of the sacrificial corrosion-preventive metal in the adhesive layer is, for example, 0.5 to 30% by mass, preferably 1 to 20% by mass, and more preferably 2 to 15% by mass, based on the total amount of the adhesive layer. If the content of the sacrificial corrosion-preventive metal is above these lower limits, the corrosion protection performance is improved due to increased sacrificial corrosion protection. If it is below these upper limits, the adhesive strength is increased, and the transparency of the adhesive tape can be ensured.

[0053] The adhesive layer may also preferably not contain sacrificial corrosion-preventive metal. When sacrificial corrosion-preventive metal is not included, the adhesive strength of the adhesive tape is maintained at a higher level compared to when it is included, making it less likely to peel off the adherend. This blocks water and oxygen, thereby improving corrosion protection. Furthermore, the transparency of the adhesive tape can be ensured.

[0054] (Conductive materials) The adhesive layer may contain conductive materials other than the sacrificial corrosion protection metal described above. It is preferable that the adhesive layer contains a conductive material when it contains a sacrificial corrosion protection metal or when a metal layer, as described later, is provided on the adhesive tape. Including a conductive material makes it easier to transfer electrons released when the sacrificial corrosion protection metal is ionized to the adherend, thereby improving the sacrificial corrosion protection performance. 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. Carbon-based materials include carbon black, graphite, graphene, carbon nanotubes, and acetylene black. Metallic materials include gold, silver, copper, nickel, or alloys containing these, or metals with a higher potential than iron, or iron itself. Metal oxide materials include, for example, indium tin oxide (ITO), antimony trioxide (ATO), fluorine-doped tin oxide (FTO), and zinc oxide. 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, or derivatives thereof. Ionic polymers include sodium polyacrylate and potassium polyacrylate. Conductive materials may be used individually or in combination of two or more types. Among the above, carbon-based materials are preferred as conductive materials, and carbon nanotubes are more preferred.

[0055] (Carbon nanotubes) The adhesive layer preferably contains carbon nanotubes as a conductive material, as described above. The inclusion of carbon nanotubes improves the sacrificial corrosion protection of the adhesive layer while maintaining high adhesive strength and transparency, making it easier to obtain an adhesive tape that balances high adhesive strength, sacrificial corrosion protection, and high transparency. This is presumed to be because, although carbon nanotubes are conductive materials, the amount required to achieve a certain level of sacrificial corrosion protection is small compared to other types of conductive materials, resulting in less reduction in adhesive strength.

[0056] Carbon nanotubes are tubular materials formed from carbon. Carbon nanotubes possess excellent electrical properties, and when combined with resins or other materials, they can form highly conductive sheets. Carbon nanotubes are materials with a structure in which graphite sheets with a hexagonal network of carbon atoms are wound into a cylindrical shape. Those wound in a single 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 single-walled carbon nanotubes, multi-walled carbon nanotubes, or mixtures containing these in any proportion. Furthermore, carbon nanotubes manufactured by various methods such as arc discharge, laser evaporation, and chemical vapor deposition (CVD) can be used.

[0057] The average diameter of the carbon nanotubes is preferably 1 to 100 nm, and more preferably 2 to 15 nm. The average length of the carbon nanotubes is preferably 0.1 to 1000 μm, and more preferably 10 to 500 μm. The aspect ratio (average length / average diameter) of the carbon nanotubes is preferably 10 to 100,000, and more preferably 500 to 30,000. Note that the diameter of a carbon nanotube refers to the outer diameter in the case of a single-walled carbon nanotube, and the outer diameter of the outermost tube in the case of a multi-walled carbon nanotube. The diameter and length of a carbon nanotube can be measured, for example, from an image obtained by observation using a TEM (transmission electron microscope), and the average diameter and average length can be determined by the arithmetic mean of any 50 nanotubes.

[0058] From the viewpoint of sacrificial corrosion protection of the adhesive layer, adhesive strength, and transparency of the adhesive tape, the content of conductive material in the adhesive layer is preferably 0.001 to 10% by mass, more preferably 0.002 to 5% by mass, and even more preferably 0.003 to 3% by mass, based on the total amount of the adhesive layer.

[0059] When the conductive material is carbon nanotubes, the carbon nanotube content in the adhesive layer is preferably 0.0005 to 0.7% by mass, more preferably 0.002 to 0.05% by mass, and even more preferably 0.003 to 0.045% by mass, based on the total amount of the adhesive layer. When the carbon nanotube content is above these lower limits, sacrificial corrosion protection tends to improve. Conversely, when the carbon nanotube content is below these upper limits, the adhesive strength tends to improve, and the transparency of the adhesive tape can be ensured.

[0060] (Method for manufacturing acrylic adhesive and adhesive layer) The adhesive layer can be manufactured using a general method for forming an adhesive layer. Below, we will explain in detail the manufacturing method of an acrylic adhesive and an adhesive layer, using the case where the adhesive is an acrylic adhesive and of the photocurable type as an example. Acrylic adhesives can be obtained by irradiating an adhesive composition containing the above-mentioned polymerizable monomers and, if necessary, a sacrificial corrosion-preventive metal and a conductive material with light to polymerize the polymerizable monomers. The adhesive composition may also optionally contain at least one of the above-mentioned tackifying resins, fine particles, and other components. More specifically, polymerizable monomers, sacrificial corrosion-preventive metals and conductive materials as needed, and tackifying resins, fine particles, and other components as needed are placed in a reaction vessel such as a glass container and mixed to obtain an adhesive composition. Next, to remove dissolved oxygen from the adhesive composition, an inert gas such as nitrogen gas is generally supplied to purge the oxygen. Then, the adhesive composition is applied to a release sheet, or after being applied to a substrate, light is irradiated to polymerize the polymerizable monomers, thereby obtaining an adhesive layer. It is preferable that the steps from applying or impregnating the adhesive composition to irradiating it with light be carried out under an inert gas atmosphere or in a state where oxygen is blocked by a film or the like. In this manufacturing method, the adhesive composition obtained by mixing each component may be prepolymerized before being applied to a release sheet or support in order to increase its viscosity.

[0061] (Storage modulus) Preferably, the adhesive layer has a storage modulus of 50,000 to 1,000,000 Pa at 23°C. When the storage modulus at 23°C is within this range, the adhesive layer has a strong ability to restore damaged areas (hereinafter also referred to as self-healing power) when damaged by external impacts, etc. As a result, corrosion protection performance is improved, and when used in materials such as steel, for example, it becomes easier to suppress the occurrence of rust. The storage modulus of the adhesive layer at 23°C is more preferably 200,000 to 800,000 Pa, and even more preferably 300,000 to 600,000 Pa, from the viewpoint of enhancing self-healing ability and improving corrosion protection performance. The storage modulus can be calculated by measuring the dynamic viscoelastic spectrum.

[0062] (Thickness) The thickness of the adhesive layer is preferably 50 to 2500 μm, more preferably 60 to 2200 μm, and even more preferably 80 to 1500 μm. By setting the thickness above the lower limit, the self-healing ability is enhanced, improving the corrosion resistance of the adhesive tape, and also making it easier to increase the adhesive strength. Conversely, by setting the thickness of the adhesive layer below the upper limit, an improvement in corrosion resistance corresponding to the thickness can be obtained, and the transparency of the adhesive tape can be made excellent.

[0063] <Composition of adhesive tape> In the present invention, as shown in Figure 1, the adhesive tape 10 is preferably a single-sided adhesive tape having a base material 12 and an adhesive layer 11 provided on one side of the base material 12. This allows the adhesive layer 11 to be protected by the base material 12. The adhesive tape is used by attaching it to the object to be adhered, with the surface 11A of the adhesive layer 11 serving as the adhesive surface. Furthermore, although not shown in the illustration, the adhesive tape may also be a double-sided adhesive tape having a base material and adhesive layers on both sides of the base material.

[0064] The adhesive tape of the present invention may have a release sheet attached to the surface of the adhesive layer. The release sheet is preferably peeled off from the adhesive layer before the adhesive tape is used, exposing the adhesive layer, which then adheres to the substrate. More specifically, the release sheet is preferably attached to the surface 11A of the adhesive layer, which is the surface opposite to the surface on which the substrate or metal layer 13 is provided. A resin film is suitable as the release sheet, but it is preferable that the surface that adheres to the adhesive layer is a release-treated surface that has been treated with a silicone release agent or the like. Furthermore, if a release liner is attached, the various physical properties of the adhesive tape, such as total light transmittance, tensile elongation at break, and difference in tensile load, shall be those measured after the release liner has been removed.

[0065] <Applications and usage> The adhesive tape of the present invention is used by being applied to the surface of a concrete structure or the surface of a structure having rusted parts. The adhesive tape of the present invention has excellent conformability and transparency, as well as excellent weather resistance. Because of these characteristics, the adhesive tape of the present invention is suitable for long-term use on concrete structures or structures having rusted parts installed outdoors. Furthermore, the adhesive tape of the present invention is also preferably used for corrosion prevention to prevent corrosion of metal materials and the like. More specifically, the adhesive tape of the present invention can suppress the progression of corrosion or damage, or corrosion of the structure from damaged areas, by applying the tape to corroded or damaged areas of the above-mentioned structure. Furthermore, because the adhesive tape of the present invention has excellent transparency, even after application, it is possible to visually check the progress 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 surface. Therefore, it is possible to take appropriate preventive maintenance measures, such as checking the corrosion or damage status of the area to which the tape is applied, and taking repair measures according to the progression of corrosion or damage.

[0066] Examples of concrete structures include elevated bridges, tunnels, embankments, buildings, mooring facilities in ports, utility poles, and dams. Concrete structures may also have metal materials such as steel inside. If a concrete structure has damage such as cracks, water may seep in through the damaged area, causing corrosion of the internal steel materials. However, by applying the adhesive tape of the present invention to the damaged area, water ingress can be prevented, thereby preventing corrosion of the internal steel materials. Furthermore, the structure having rusted parts is not particularly limited as long as it has rusted parts. Examples include various metal structures such as iron bridges, tanks, plants, factory machinery and equipment, signs, road signs, guardrails, containers, power transmission equipment, water pipes, and ships. Preferably, the metal material is a metal material containing at least one selected from the group consisting of iron and iron-containing alloys. Specifically, iron-containing alloys include various steel materials such as nickel-chromium steel, nickel-chromium-molybdenum steel, chromium steel, chromium-molybdenum steel, manganese steel, and carbon steel. In addition, the adhesive tape is preferably applied to the rusted surface of the structure when it has rusted parts. Note that rust is the corrosive part of metal and is not limited to red rust or brown rust caused by iron, but includes various types of rust such as blue rust, black rust, and white rust.

[0067] The adhesive tape of the present invention may be applied to the surface to be attached after applying a rust inhibitor or primer. The rust inhibitor that can be used in the present invention is not particularly limited, but examples include those that have an adsorption effect that adsorbs moisture and salt, which are rust-causing substances, and rust converters that convert red rust to black rust. When attaching these rust inhibitors to a structure that has rust, applying them to the surface to be attached to the tape makes it easier to enhance the effect of preventing the progression of corrosion. On the other hand, it is preferable to use a primer that has alkali-resistant properties. Applying an alkali-resistant primer to the surface to be attached to the tape before attaching it to a concrete structure makes it easier to enhance the effect of preventing the progression of corrosion. Both the rust inhibitor and the primer can be known products, and from the viewpoint of being able to see the attached surface, it is preferable that they have transparency. [Examples]

[0068] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0069] [Evaluation Method] In the examples and comparative examples, the adhesive tapes were evaluated using the following evaluation method.

[0070] <Total light transmittance (500h)> The adhesive tapes obtained in each example and comparative example were processed into measurement samples measuring 50 mm in width and 30 mm in length, and the total light transmittance (initial total light transmittance) was measured. In addition, accelerated weathering tests were conducted using measurement samples prepared in the same manner, based on Cycle A of JIS K5600-7-7. The tests were conducted for 500 hours. After the accelerated weathering tests, the total light transmittance (total light transmittance after the test) was measured for the measurement samples. The total light transmittance was measured in accordance with JIS K7361-1. Specifically, it was measured using a haze meter (Haze Meter NDH4000 manufactured by Nippon Denshoku Industries Co., Ltd.) in an atmosphere of 23°C and 50% humidity.

[0071] <Total light transmittance (1000h)> Except for a 1000-hour accelerated weathering test, the measurements were performed using the same procedure as for total light transmittance (500h).

[0072] <Total light transmittance (2000h)> Except for a 2000-hour accelerated weathering test, the measurements were performed using the same procedure as for total light transmittance (500h).

[0073] The total light transmittance after accelerated weathering tests was evaluated based on the following evaluation criteria. ◎: After 500 hours of accelerated weathering testing, 1000 hours of testing, and 2000 hours of testing, the total light transmittance was 50% or higher in all cases. ○: After 1000 hours of accelerated weathering testing, and at least after 2000 hours of testing, the total light transmittance was less than 50%, but after 500 hours of testing, the total light transmittance was 50% or more. ×: After 500 hours, 1000 hours, and 2000 hours of accelerated weathering testing, the total light transmittance was less than 50%.

[0074] <Difference in tensile load> For each example and comparative example, the adhesive tapes obtained were tested using a tensile testing machine to measure the tensile load when stretched by 2.5% and the tensile load when stretched by 0.5%, respectively. The difference between the two values ​​was then calculated. This measurement was performed in both the MD and TD directions, and the difference between the tensile load when the adhesive tape was stretched by 2.5% and the tensile load when the adhesive tape was stretched by 0.5% was calculated for each direction. The larger of the calculated differences in tensile loads in the MD and TD directions was used as the difference in tensile load.

[0075] <Tensile elongation at breaking point> The adhesive tapes obtained in each example and comparative example were subjected to tensile tests in the MD direction and TD direction using a tensile testing machine (Tensilon Universal Material Testing Machine, manufactured by A&D Co., Ltd.), and the tensile elongation at the breaking point was calculated using the following formula. Tensile elongation at fracture (%) = (L - L0) / L0 × 100 Here, L is the length of the sample at the time of fracture, and L0 is the length of the sample before the tensile test. The measurement value of whichever of the substrate or adhesive layer fractured first was adopted as the tensile elongation at fracture. Of the adopted tensile elongations at fracture in the MD direction and TD direction, the smaller value was taken as the tensile elongation at fracture of the adhesive tape. The conditions for measuring tensile load and elongation at tensile fracture were as follows. Furthermore, all of the above tensile tests were conducted under conditions of 23°C and 50RH. Base material dimensions and shape: Strips measuring 24mm wide x 80mm long. Chuck spacing: 50mm Tensile speed: 300 mm / min

[0076] <Topcoat adhesion> A fluorine-based topcoat paint (manufactured by Dainippon Paint Co., Ltd., product name "V-Flon #100H Smile Topcoat IG") conforming to JIS K5659:2018 was applied to a topcoat with a dry thickness of 25 μm. The sample obtained by drying at 23°C for 16 hours was then subjected to a grid test in accordance with JIS K5600-5-6 to evaluate the topcoat adhesion, and the number of peeled grids was recorded. In the grid test, the dimensions and number of grid squares were set to 2 mm x 2 mm and 25 squares, respectively.

[0077] <Evaluation of topcoat paint> A general structural rolled steel material (SS400) measuring 70 mm in length and 150 mm in width was prepared. Then, as shown in Figure 3, adhesive tapes (60 mm wide, 140 mm long) 10 for each example and comparative example were attached to the rolled steel material 30. Using a brush, the rolled steel material 30 with the adhesive tapes 10 attached was painted with a topcoat paint (manufactured by Dainippon Paint Co., Ltd., product name "V-Flon #100H Smile Topcoat") 40. After the topcoat paint 40 applied to the rolled steel material 30 was allowed to dry for 24 hours, the wrinkle formation of the adhesive tapes 10 was visually observed. ○...When the adhesive tape was wrinkle-free and the above grid test was performed, two or fewer grids were peeled off. ×...The adhesive tape had wrinkles, or when the above grid test was performed, more than two grids were peeled off.

[0078] <Solvent resistance> 1. Sample preparation The sample was cut into 60mm squares. The length of the diagonal of the cut sample was measured. This diagonal length was designated as diagonal A. 2. Measurement of solvent resistance The sample obtained in step 1 above was immersed in xylene for 5 minutes. The length of the diagonal of the sample after immersion was measured. This diagonal length was designated as diagonal B. The dimensional change rate of the tape's base material was calculated using the lengths of the two diagonals obtained as described above. The formula for calculating the dimensional change rate was as follows: Dimensional change rate (%) = (diagonal B - diagonal A) / diagonal A × 100

[0079] <Elmendorf tear strength> The measurement was performed using a method similar to the Elmendorf tear strength method in accordance with JIS K7128-2 (1998), except that the sample was not slit during measurement. Measurements were performed for both MD and TD, and the smaller value was taken as the Elmendorf tear strength (N) of the substrate.

[0080] <Storage modulus at 23°C> The storage modulus of the adhesive layer of the adhesive tape at 23°C was calculated by measuring the dynamic viscoelastic spectrum using a dynamic viscoelasticity measuring device (manufactured by IT Measurement Control Co., Ltd., product name "DVA-200") under the following conditions: shear mode: 10 Hz, strain: 0.1%, temperature range: -100°C to 100°C, and heating rate: 10°C / min.

[0081] <Adhesion (500h)> 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 create measurement samples. Bonding to the SUS plate was performed by running a 2 kg roller back and forth twice at a speed of 10 ± 0.5 mm / s. The initial adhesive strength (adhesive strength before testing) was measured using these measurement samples. In addition, using a similarly prepared sample, an accelerated weathering test was conducted based on Cycle A of JIS K5600-7-7. The test was performed for 500 hours. The adhesive strength (adhesion after the test) of the sample after the accelerated weathering test was then measured. 2.Measurement method Adhesion strength was measured using pre- and post-test samples, and peel tests were performed as follows. Each measurement sample was fixed to the chuck of a tensile testing machine (Tensilon Universal Material Testing Machine, manufactured by A&D Co., Ltd.). Then, under conditions of 23°C and 50RH, the adhesive tape was pulled for more than 60mm at a peel angle of 180° and a speed of 300mm / min, and the interval average value of the load (N) detected by the load cell was recorded and defined as the adhesive strength.

[0082] <Adhesion (1000h)> Except for a 1000-hour accelerated weathering test, the measurements were performed using the same procedure as for adhesion (500h).

[0083] <Adhesion (2000h)> Except for a 2000-hour accelerated weathering test, the measurements were performed using the same procedure as for adhesion strength (500h).

[0084] The adhesive strength after accelerated weathering tests was evaluated based on the following evaluation criteria. ◎: After 500 hours of accelerated weathering testing, 1000 hours of testing, and 2000 hours of testing, the adhesive strength was 20 N / 25 mm or higher. ○: After 500 hours and 1000 hours of accelerated weathering testing, the adhesive strength was 20 N / 25 mm or higher. However, after 2000 hours of testing, the adhesive strength was either less than 20 N / 25 mm or could not be measured due to substrate fracture. ×: After 2000 hours of accelerated weathering testing, the adhesive strength was less than 20 N / 25 mm or could not be measured due to substrate fracture. Furthermore, similar results were obtained after at least 500 hours and 1000 hours of accelerated weathering testing.

[0085] <Gloss retention rate (500h)> 1.Measurement method The adhesive tapes (25 mm wide, 100 mm long) obtained in each example and comparative example were attached to the substrate, and the haze of the substrate was measured by irradiating the surface of the tape from the substrate side using a haze meter (manufactured by Horiba, Ltd., product name: "IG-340"). The haze was measured using a haze meter with a geometric condition of 60° in accordance with JIS K 5600-4-7. The haze obtained at this measurement is designated as Haze A. Subsequently, 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 was conducted for 500 hours in accordance with cycle A of JIS K 5600-7-7. After the accelerated weathering test, the haze of the substrate of the tape was measured in the same manner as before the test. The haze obtained at the measurement after the test is designated as Haze B. The gloss retention rate of the tape was calculated using the two types of haze obtained as described above. The formula for calculating the gloss retention rate is as follows: Gloss retention rate (%) = (Haze B / Haze A) × 100

[0086] <Gloss retention rate (1000h)> Except for conducting an accelerated weathering test for 1000 hours, the gloss retention rate (500h) was measured using the same procedure.

[0087] <Gloss retention rate (2000h)> Except for conducting an accelerated weathering test for 2000 hours, the gloss retention rate (500h) was measured using the same procedure.

[0088] The gloss retention rate calculated using the above method was evaluated based on the following evaluation criteria. ◎: After 500 hours, 1000 hours, and 2000 hours of accelerated weathering testing, the gloss retention rate was 80% or higher in all cases. ○: After 500 hours and 1000 hours of accelerated weathering testing, the gloss retention rate was 80% or higher, but after 2000 hours of the same test, the gloss retention rate was less than 80%. ×: At a minimum, the gloss retention rate was less than 80% after 1000 hours and 2000 hours of accelerated weathering testing.

[0089] <Overall Weather Resistance Evaluation> Based on the results of the adhesive strength and total light transmittance evaluation of the adhesive tape after accelerated weathering testing according to Cycle A of JIS K5600-7-7, a comprehensive weather resistance evaluation was conducted. The evaluation criteria are as follows: ◎: Of the evaluation results for adhesive strength, total light transmittance, and gloss retention, at least the evaluation for total light transmittance was "◎" and there were no "×" ratings. ○: Of the evaluation results for adhesive strength, total light transmittance, and gloss retention, the evaluation for total light transmittance was not "◎", but there were no "×" ratings. ×: One or more "×" marks were found in the evaluation results for adhesive strength, total light transmittance, and gloss retention.

[0090] <Practical evaluation regarding responsiveness> The tracking performance was evaluated using the following procedure, 1-4 below. 1. As shown in Figure 2, the adhesive tape 10, prior to being subjected to accelerated weathering testing in accordance with Cycle A of JIS K 5600-7-7, was attached to the adhesive surface 20A of the L-shaped SUS plate 20 so that the height h from the corner and the width t were 2 mm. 2. A squeegee was pressed against the portion of the adhesive tape 10 that was not attached to the L-shaped SUS plate 20. 3. After pressing the tape as described in 2. above, the height h of the lifted portion was measured, and the presence or absence of tears in the adhesive tape 10 was visually checked. 4. Based on the height h measurements obtained in 3. above, the conformability of the adhesive tape 10 was evaluated according to the following criteria. ◎: The height h became 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 tear occurred in the adhesive tape 10, and it maintained a certain degree of conformability. ×: The height h was 2 mm, and a tear occurred in the adhesive tape 10, and it did not conform to the SUS plate at all.

[0091] <Practical evaluation regarding peeling> Adhesive tapes (25 mm wide, 100 mm long) from each example and comparative example were attached to a SUS plate (50 mm wide, 125 mm long), and cured at 23°C for 3 days to prepare samples for peel evaluation. Water was sprayed for 5 minutes at a water pressure of 8 MPa from a spray position diagonally above the adhesive tape on the peel evaluation sample, towards the side of the longitudinal end of the adhesive tape. The spray position was determined to be a position where the angle between the line connecting the spray position and the center of the adhesive tape end and the SUS plate was 30°, and also directly above a point 5 cm horizontally away from the center of the adhesive tape end. The distance the adhesive tape peeled off after water spraying was measured and evaluated according to the following criteria. ◎・・The distance of the peeling is between 0mm and less than 15mm ○...The distance of the peeling is 15mm or more but less than 20mm ×...The distance of the peeling is 20mm or more

[0092] <Overall Rating> Based on the results of the overall weather resistance evaluation, conformability evaluation, and practical evaluation regarding peeling, the overall evaluation of the adhesive tape was conducted according to the following criteria. The evaluation criteria are as follows: ◎: The results of the overall weather resistance evaluation, conformability evaluation, and practical evaluation regarding peeling were all "◎", and the result of the practical evaluation regarding the topcoat coating was "〇". ○: The results of the overall weather resistance evaluation, conformability evaluation, and practical evaluation regarding peeling were all "○" or higher. ×: One or more "×" marks were found in the results of the overall weather resistance evaluation, conformability evaluation, and practical evaluation regarding peeling.

[0093] [Materials used] The following materials were used in each example and comparative example.

[0094] <Adhesive layer> • 2-Ethylhexylacrylate n-butyl acrylate Acrylic acid • 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 "Alcon P140", manufactured by Arakawa Chemical Industries, Ltd., hydrogenated petroleum resin, softening point 140℃ • Tackifying resin 2: Product name "Alcon P100", manufactured by Arakawa Chemical Industries, Ltd., hydrogenated petroleum resin, softening point 100℃ • A metal with a lower electrical potential than iron: Zinc particles, manufactured by Sakai Chemical Industry Co., Ltd., product name "Zinc Powder #40", average particle size: 50 μm • Conductive material: Carbon nanotubes (CNTs), manufactured by JEIO, product name "JENOTUBE8A", average diameter 6-9 nm, average length 100-200 μm • Dispersant: Sekisui Chemical Co., Ltd., product name "Eslec BX-L", polyvinyl butyral resin • Microparticles: Product name "Cellstar Z-27", manufactured by Tokai Kogyo Co., Ltd., glass balloon • Crosslinking agent: Product name "TEAI-1000", manufactured by Nippon Soda Co., Ltd. • Polymerization initiator: 2,2-dimethoxy-2-phenylacetophenone

[0095] <film> • Fluorine-based resin film: Product name: "50NS", manufactured by AGC Inc. • Acrylic resin film 1: Product name "Acryprene HBS006", manufactured by Mitsubishi Chemical Corporation • Acrylic resin film 2: Product name "Soft Acrylic Sheet", manufactured by Tatsuta Chemical Co., Ltd. • Acrylic resin film 3: Product name "Acryprene MBS121E", manufactured by Mitsubishi Chemical Corporation • Polyolefin resin film: Product name "Purelon CP-WGF", manufactured by Sumika Sekisui Film Co., Ltd. PET film • Polyvinyl chloride resin film: Product name "00C040M", manufactured by Nippon Carbide Industries, Ltd.

[0096] [Examples 1-11, Comparative Examples 1-4] Adhesive compositions were prepared according to the formulations described in Tables 1-3. In Tables 1-3, "parts" refers to "parts by mass." Dissolved oxygen was removed from the adhesive composition by purging with nitrogen. Next, a spacer with the same thickness as the adhesive layer was placed on the release surface of the release sheet, and the adhesive composition was applied to the release surface of the release sheet. Then, another release sheet was placed over the applied adhesive composition so that its release surface was in contact with the adhesive composition. A silicone-release treated PET film (50 μm thick) was used as the release sheet. In this state, the UV irradiation intensity on the release sheet on the covering side is 5 mW / cm². 2 The lamp intensity of the chemical lamp was adjusted accordingly, and ultraviolet light was irradiated from one side for 15 minutes to obtain an adhesive layer consisting of an adhesive layer alone with release sheets attached to both sides. Then, after peeling off one of the release sheets, the film (substrate) described in Tables 1-3 was bonded to the adhesive layer obtained by the above method to obtain an adhesive tape. Before performing various physical properties or evaluations on the adhesive tape, the other release sheet was also peeled off.

[0097] [Table 1]

[0098] [Table 2]

[0099] [Table 3]

[0100] As is clear from the above examples, the adhesive tape that satisfies the requirements of the present invention not only has excellent conformability and transparency, but also maintains excellent conformability and transparency, and its adhesive strength is not impaired even after weather resistance testing. In contrast, the adhesive tape prepared in Comparative Example 1 had a large tensile load difference but a small elongation at the tensile fracture point, and the adhesive tape lifted during the conformability evaluation, thus failing to achieve excellent conformability. Furthermore, the adhesive tape prepared in Comparative Example 3 had a low total light transmittance after the weather resistance test, thus failing to achieve excellent transparency. In addition, the adhesive tapes prepared in Comparative Examples 2 and 4 failed to achieve excellent weather resistance because the substrate broke during the peel test conducted in the adhesion strength measurement after 500 hours of weather resistance testing. [Explanation of symbols]

[0101] 10 Adhesive Tapes 11 Adhesive layer 12 Base material 13 Metal layer 20 L-shaped SUS plate 20A Adhering surface 30 Rolled steel for general structural use 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, The adhesive tape has a tensile load difference of 0.4 N / mm or more and 1.3 N / mm or less between the tensile load when stretched by 2.5% and the tensile elongation at the breaking point of 100% or more. The adhesive layer comprises an alkyl (meth)acrylate monomer and a crosslinking agent, and has a storage modulus of 50,000 to 1,000,000 Pa at 23°C. An adhesive tape for concrete structures or structures with rusted parts, wherein the total light transmittance of the adhesive tape is 50% or more after both 500 hours and 1000 hours of accelerated weathering testing in accordance with Cycle A of JIS K5600-7-7, and the substrate does not break in a peel test performed after 500 hours of accelerated weathering testing, and the adhesive strength of the adhesive layer is 20 N / 25 mm or more.

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

3. The adhesive tape according to claim 1 or 2, wherein a fluorine-based topcoat paint (manufactured by Dainippon Paint Co., Ltd., product name "V-Flon #100H Smile Topcoat IG") conforming to JIS K5659:2018 is applied to the substrate to a thickness of 25 μm, and a measurement sample obtained by drying at 23°C for 16 hours is subjected to a grid test in accordance with JIS K5600-5-6, and no grid cells peel off.

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

5. The adhesive tape according to claim 1 or 2, wherein the gloss retention rate of the substrate after the accelerated weathering test has been performed for 500 hours is 80% or more.

6. The adhesive tape according to claim 1 or 2, wherein the base material includes at least one selected from the group consisting of polyvinyl chloride resin, acrylic resin, and fluororesin.

7. The adhesive tape according to claim 1 or 2, wherein the thickness of the substrate is 20 to 300 μm.

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

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

10. The adhesive tape according to claim 1 or 2, wherein the adhesive layer is formed of an acrylic adhesive.

11. The adhesive tape according to claim 1 or 2, wherein the adhesive layer contains a metal with a lower potential than iron.

12. The adhesive tape according to claim 11, wherein zinc is a metal with a lower electrical potential than iron.

13. The adhesive tape according to claim 1 or 2, wherein the adhesive layer contains a conductive material other than a metal with a lower potential than iron.

14. The adhesive tape according to claim 13, wherein the conductive material is a carbon nanotube.

15. A method for using adhesive tape, comprising attaching the adhesive tape described in claim 1 or 2 to the surface of a concrete structure or a structure having a rusted portion.

16. The method for using adhesive tape according to claim 15, wherein a rust inhibitor or primer is applied to the surface on which the adhesive tape is to be attached to the concrete structure or the structure having the rusted portion, and then the adhesive tape is attached.

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